Dr. Fa.xon received his MD degree from Boston University School of Medicine. After his internship and residency in internal medicine at Dartmouth Medical Center, he com- pleted his cardiology fellowship at Boston University Medi- cal Center. He continued his career at Boston, beginning with the directorship of the Cardiac Catheterization Labo- ratory at the University Hospital, and became a member of the faculty. He most recently served at Boston University Medical Center as the Associate Director of Cardiology and Professor of Medicine. In June 1993 Dr. Fa,xon joined the faculty at the University of Southern California Medical School as Professor of Medicine and accepted the position of Chie$ Division of Cardiology, at the Los Angeles County and University of Southern California Medical Center. His research and clinical interests include prevention of rest- enosis after angioplasty, healing afler vascular injury, and new interventional devices. He is Board Certified in Znter- nal Medicine and Subspecialty Board Certified in Cardio- vascular Diseases. Dr. Mehra received his MBBS degree from Government Medical College, Surat, India. Afrer his internship and resi- dency training in internal medicine at Los Angeles County and University of Southern California Medical Center, he completed his cardiology fellowship training at the same institution. He is presently an interventional fellow at Los Angeles County and University of Southern California Medi- cal Center. His research and clinical interests include pre- vention of restenosis afler angioplasty, and basic mecha- nisms underlying hibernating myocardium. Dr. Mehra is Board Certified in Internal Medicine. Curr Probl Cardiol, May 1994 233
Transcript
Dr. Fa.xon received his MD degree from Boston University School of Medicine. After his internship and residency in internal medicine at Dartmouth Medical Center, he com- pleted his cardiology fellowship at Boston University Medi- cal Center. He continued his career at Boston, beginning with the directorship of the Cardiac Catheterization Labo- ratory at the University Hospital, and became a member of the faculty. He most recently served at Boston University Medical Center as the Associate Director of Cardiology and Professor of Medicine. In June 1993 Dr. Fa,xon joined the faculty at the University of Southern California Medical School as Professor of Medicine and accepted the position of Chie$ Division of Cardiology, at the Los Angeles County and University of Southern California Medical Center. His research and clinical interests include prevention of rest- enosis after angioplasty, healing afler vascular injury, and new interventional devices. He is Board Certified in Znter- nal Medicine and Subspecialty Board Certified in Cardio- vascular Diseases.
Dr. Mehra received his MBBS degree from Government Medical College, Surat, India. Afrer his internship and resi- dency training in internal medicine at Los Angeles County and University of Southern California Medical Center, he completed his cardiology fellowship training at the same institution. He is presently an interventional fellow at Los Angeles County and University of Southern California Medi- cal Center. His research and clinical interests include pre- vention of restenosis afler angioplasty, and basic mecha- nisms underlying hibernating myocardium. Dr. Mehra is Board Certified in Internal Medicine.
Curr Probl Cardiol, May 1994 233
CURRENT STATUS OF PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY
BACKGROUND
The development of angioplasty as a revascularization therapy in the management of coronary artery disease is one of the most im- portant landmarks in medicine in the last century. This concept was first conceived in 1964 by astute observations made by Dr. Charles Dotter, a vascular radiologist in Portland, Oregon, who noted that a passage of a diagnostic catheter resulted in significant reduction in high-grade iliac artery sten0sis.l Dotter’s technique (dilation with a series of graduated catheters) was subsequently used principally in Europe in the treatment of peripheral vascular disease.’ Modification of this technique with an elastic balloon instead of rigid catheters was first developed by Dr. Werner Postmann. Dr. Andreas Gruentzig, working at the University of Zurich, Switzerland, further modified an- gioplasty by developing an inelastic double-balloon catheter. He used it initially to dilate peripheral vascular stenoses successfully. In the first 75 cases, he reported a success rate of 75% .3 Encouraged by these results, he developed a smaller double-balloon catheter system for coronary artery dilation. However, as noted earlier, the initial con- cept to treat coronary artery stenosis with angioplasty and intravas- cular stents was first suggested by Dotter, although he never used them for this purpose. Subsequently, after successful dilation of ex- perimental stenosis in dogs, the first angioplasty in human beings was performed by Dr. Gruentzig and Dr. Richard Myler at the Uni- versity of San Francisco, where dilation of a saphenous vein graft was successfully accomplished at the time of bypass surgery. Dr. Gru- entzig successfully performed the first angioplasty on a proximal left anterior descending artery in a 37-year-old man on September 17, 1977, at the University of Zurich.4 With this report, the acceptance of the procedure and physicians’ enthusiasm grew rapidly. The follow- ing year the National Heart, Lung and Blood Institute (NHLBI) estab- lished a registry and collected more than 3000 cases from 1977 to 1981.5 In 1980, Dr. John Simpson and Dr. Edward Roberts developed the first over-the-wire catheters (coaxial balloon and shaft system
234 Curr Probl Cardiol, May 1994
with a movable guide wire), which expanded the use of angioplasty to more distal and tortuous vessels. By 1985, approximately 100,000 patients had undergone the procedure in the United States (Fig. 11.” A second NHLBI registry collected data in 3000 patients between 1985 and 1986.7 It showed that angioplasty was being performed in an in- creasing number of older patients, patients with a history of myocar- dial infarction, coronary artery bypass grafting (CABG), left ventricu- lar dysfunction, multivessel disease, and more complex lesions7-” Despite the increased complexity of lesions and high-risk patient characteristics, the success rate of angioplasty increased from 65% in the initial series to 91% in the second NHLBI registry, with signifi- cantly lower complication rates, including myocardial infarction, emergency CABG, and death.8’10’11 The use of angioplasty has con- tinued to increase at a rapid pace; more than 300,000 angioplasties were performed in the United States in 1993, exceeding the number of bypass operations.12 However, angioplasty cannot be applied to all patients with coronary artery disease. At present the major reasons for not performing angioplasty include long-term total occlusion (50% 1, diffuse coronary disease (20% 1, left main coronary artery dis- ease (12%), unfavorable lesion characteristics, such as ostial lesions, and the presence of severe calcification in a minority of cases?
Revascularization Procedures
550 1 o !XtO -Total
p --- 1 - CABG .-- 9 4504 0-0 &CA
/ - 1 (% of Total)
x 400.
j$ 350- g 300.
g 250. g 200. 5 150.
&j 100. 4 z 501 I,, (4) (4) (7) (’
I e<c, 1 I , I , , 79 80 81 82 03 04 05 86 87 88 89 90
FIG. 1. The growth of coronary angioplasty in the United States since its inception 15 years ago. Currently, more than 300,000 procedures are performed, exceeding the number of coronary bypass operations. (From Faxon DP. lntroductlon and historlcal background. In: Faxon DP, ed. Practical angioplasty. New York: Raven Press, 1993:3.)
Cum Probl Cardiol, May 1994 235
b S.R. BAILEY: The expansion of coronary angioplasty to more complex cases is attributable to both the improvement in equipment and the increased experi- ence level of interventional cardiologists in case selection. The continued de- crease in the number of patients requiring emergency coronary artery bypass grafting as the result of coronary angioplasty despite more complex cases is an excellent illustration of the phenomenon.
b P. M. SHAH: Other important reasons for not performing angioplasty include absence of functional correlates of anatomic coronary arterial lesions and ab- sence of documented survival benefits. These are the same reasons for not ml- dertaking coronary artery bypass surgery despite the presence of epicardial COM- nary arterial occlusions. This is especially true because the incidence of reste- nosis of between 30% to 50% in different series is high, the mechanisms are poorly understood, and restenosis is essentially unpreventable.
One of the major limitations of long-term benefits of angioplasty is the recurrence of stenosis at the site of the initial dilation requiring repeat angioplasty or surgical revascularization. Data from currently published trials indicate that one third of patients undergoing an- gioplasty have undergone a previous angioplasty or coronary bypass surgery.‘” Although the understanding of the pathophysiologic mechanisms of restenosis has improved considerably in the last 8 to 10 years, it is still impossible to predict in what patients or vessel segments restenosis will develop. On the basis of our current under- standing of the pathophysiologic mechanisms, a number of well- designed clinical trials have tested antithrombotic, antiproliferative, antiinflammatory, antispastic, and lipid-lowering agents in the last 8 to 10 years without any demonstrable reduction in the rate of restenosis.‘4-‘6 A number of newer devices that were designed to lower the restenosis rate have also failed to make any major impact on the rate of clinical or angiographic restenosis; however, each may be used as preferred therapy in specific circumstances. The future challenges facing balloon angioplasty and newer interventional tech- niques include designing an effective therapy for the expanding group of patients eligible for angioplasty and preventing or reducing restenosis.
- b S.R. BAILEY: PICA is limited in native vessels by the occurrence of dissection, development of thrombus, difficulty in recanalizing totally occluded vessels, and by high restenosis rates in midbody lesions of saphenous vein grafts. The newer interventional devices are being developed to address many of these limitations of conventional balloon angioplasty.
CURRENT INDICATIONS AND CONTRAINDICATIONS
During the early years of its application, coronary angioplasty was used primarily for symptomatic patients with proximal, discrete, non- calcified, subtotal obstructive lesions in a single coronary artery. Sub-
236 Curr Probl cardiol, May 1994
sequently, with technical advances, increased clinical acceptance, and improved clinical experience, its use has expanded to include high-risk patients with multivessel disease, multiple lesions in the same artery, total occlusions, bypass graft stenosis, acute myocardial infarction, and cardiogenic shock. In the second NHLBI registry, mul- tivessel disease accounted for 53% of patients undergoing angio- plasty.7
Current clinical indications for percutaneous transluminal coro- nary angioplasty (PTCA) are outlined in detail in the subcommittee report of the American College of Cardiology/American Heart Asso- ciation Task Force on assessment of diagnostic and therapeutic car- diovascular procedures.17 Some common indications for PTCA are outlined in Table 1.18 In general, indications for PICA should take into account clinical criteria (patients with symptoms versus patients without symptoms and with presence or absence of inducible myo- cardial ischemia), anatomical considerations (single versus multives- se1 disease), and the risk of morbidity and death. Patients should ei- ther have symptoms related to coronary lesions considered for dila- tion that are unresponsive to medical therapy, be intolerant to medi- cal therapy, or should have laboratory evidence (from resting, ambulatory, or exercise electrocardiography) of ischemia on medical therapy. In patients without symptoms, PTCA is indicated only if a significant lesion in one or more major epicardial arteries with mod- erate to large areas of viable myocardium at risk is present with one of the following indications: (11 objective evidence of severe myocar- dial ischemia by laboratory testing on medical therapy; (2) planned high-risk noncardiac surgery and objective evidence of ischemia; (31 resuscitation from a ‘near death” episode or sustained ventricular tachycardia without acute myocardial infarction; or (4) history of myocardial infarction and ischemic type ST segment changes on baseline electrocardiogram.
TABLE 1. Some common indications for percutaneous transluminal coronary angioplasty’
For patients who have a significant lesion in one or more major epicardial arteries that subtend at least a moderate-sized area of viable myocardium and who:
1. Have recurrent ischemic episodes after myocardial infarction. 2. Show evidence of myocardial ischemia while on medical therapy during laboratory
testing (including electrocardiographic monitoring at rest, as with unstable angina). 3. Have angina pectoris that has not responded adequately to medical treatment. 4. Have been resuscitated from cardiac arrest or sustained ventricular tachycardia in the
absence of acute myocardial infarction. 5. Must undergo high-risk noncardiac surgery, if angina is present or there is objective
evidence of ischemia.
From Ryan TJ. Patient selection: current status. In: Faxon DP, ed. Practical angioplasty New York: Raven Press. 1993:17. ‘For a complete listing and discussion of accepted indications for PTCA, see Reference 3.
Curr Probl Cardiol, May 1994 237
b S.R. BAILEY: The clinical recognition that “silent” myocardial &hernia identi- fies a patient population at increased risk of myocardial infarction and death has prompted the use of balloon angioplasty to hopefully decrease these events. This postulate remains to be proven by a prospective study.
b P.M. SHAH: For management of asymptomatic or mildy symptomatic patients, one must consider not only objective evidence of ischemia (that is, a positive exercise stress test or stress radionuclide or stress echocardiographic findings) but also the threshold for developing ischemia. For example, a patient who devel- ops signs of ischemia after 9 to 10 minutes of treadmill exercise with the Bruce protocol generally carries an excellent prognosis with medical management and may only be considered a candidate for intervention in exceptional circum- stances. The fourth indication stated above- that is, a history of myocardial in- farction and ischemic type ST-T segment changes on the baseline ECG-is not based on studies showing improved prognosis with angioplasty. In patients with transmural myocardial infarction, angioplasty should only be considered ifviable mvocardium can be demonstrated in the territory served by the culprit lesion.
Whereas FTCA was initially used primarily in patients with ongo- ing stable angina with single-vessel lesions, it is now used with in- creasing frequency in patients with more unstable clinical syn- dromes, such as new onset, rest, or preinfarction angina. The major pathophysiologic mechanism in unstable coronary syndrome is rup- ture of atherosclerotic plaque with formation of nonocclusive throm- bus on it. The presence of thrombus and activation of intrinsic pro- coagulant and anticoagulant factors in this situation markedly in- crease the risk of serious complications of angioplasty (myocardial infarction, emergency bypass surgery, and death).1sW23 Therefore, in the setting of an unstable angina, the angioplasty procedure should be limited to dilation of one or more culprit lesions only. In unstable angina, if symptoms are controlled with intensive medical therapy, pretreatment with 3 to 4 days of intravenous heparin and aspirin can significantly reduce the risk of abrupt closure. In clinical trials this strategy has been clearly shown to reduce the risk of serious compli- cations of angioplasty.“4-“”
b S.R. BAILEY: Unstable angina and ulcerated coronary lesions clearly identify pa- tients at increased risk of both clinical events and complications during percu- taneous coronary angioplasty (Myler R, et al. J Am Co11 Cardiol 1992;19:1641-52). The role of heparin and thrombolytic agents in stabilizing patients with unstable angina before angioplasty is not clear. Anecdotal reports of heparin given 3 to 14 days before intervention have been associated with decreased procedural com- plications. No prospective randomized study has been performed to answer the questions of what constitutes adequate anticoagulation or duration of therapy before intervention. Published reports of intracoronary thrumbolytic agents for unstable angina have been disappointing and suggest that at present this is not recommended as a routine procedure in the absence bf angiographically visible thrombus (Zeiher A, et al. Circulation 1990;82 [suppl III]:189; and Ambrose JA, et al. J Am Co11 Cardiol 1992;19:1197). Newer agents such as hirudin and a platelet glycoprotein IIb/IIIa inhibitor (7e3) are also being evaluated and show more
238 Cur-r Probl Cardiol, May 1994
promise as adjunctive agents in the stabilization of patients with unstable an- gina.
b P.M. SHAH: The syndrome of unstable angina includes a wide spectrum, from new onset or rest angina with minor ECG changes to prolonged episodes of chest pain accompanied by pronounced (more than 2 mm) ST segment depression in a number of ECG leads. The management of the latter condition requires some urgency and a more aggressive approach, whereas the former may be treated medically unless there is a recurrence of symptoms or objective evidence of isch- emia at a low threshold develops.
A number of clinical studies have now defined the role of angio- plasty in the setting of acute myocardial infarction.27-33 In general, indications for PICA in the setting of acute myocardial infarction in- clude patients with postinfarction angina, severe objective evidence of ischemia, or recurrent ventricular tachycardia or fibrillation de- spite antiarrhythmic therapy who have a significant lesion in the infarct-related artery with suitable angiographic lesion characteris- tics.
CABG surgery results in initial relief of angina in most patients. However, during long-term follow-up, up to 50% of patients have a recurrence of angina within 10 years because of either progression of the disease in native coronary arteries or the development of oc- clusions in bypass grafts (50% in saphenous vein grafts at 10 years) .34-40 This situation has resulted in an exponential increase in the number of patients referred for repeat revascularization.4*J42 Re- operation in this group of patients is known to be associated with increased numbers of deaths resulting from sur lief of angina, and reduced graft patency rates.4 f:
ery, incomplete re- -44 Therefore an in-
creasing number of patients are now considered for PICA for recur- rent angina after bypass surgery.45-47 The success and complication rates of PICA and therefore its indication in patients after CABG is dependent on the time since the operation, the type of conduits (sa- phenous vein grafts versus internal mammary grafts versus native ar- teries), and the site of stenosis. Patients seen with ischemia immedi- ately after CABG (within days to weeks) usually have acute thrombo- sis.48 PICA is best avoided in this situation except in patients with focal stenosis at graft anastomosis or short segment of thrombosis because PICA at this time is associated with a significantly higher risk of distal embolization and reocclusion.4s’50 Patients with recur- rent ischemia 1 to 12 months after CABG usually have graft stenosis as a result of neointimal hyperplasia.51 The risk of distal emboliza- tion in this group of patients is low, and PICA of conduit stenosis can be performed safe1y.46,52-56 The rate of restenosis in distal saphe- nous vein graft stenosis or internal mammary coronary implantation site stenosis is relatively low, but the rate for midsegment saphenous vein graft stenosis or aorta-ostial disease is high with conventional
Corr Probl Cardiol, May 1994 239
balloon angioplasty!’ The use of directional coronary atherectomy or stents may reduce the rate of restenosis in these settings, although a recent randomized trial of directional coronary atherectomy ver- sus PTCA (CAVEL4T II) failed to show a reduction in restenosis with directional atherectomy.58-61 Recurrence of ischemia 1 to 3 years af- ter CABG occurs in 10% to 15% of patients and is commonly due to new stenotic lesions in native coronary arteries and saphenous vein grafts caused by the rapid development of atherosclerosis. It is espe- cially increased in patients with diabetes or hyperlipidemias. When new stenosis occurs in a patient after bypass, PTCA of native coro- nary arteries rather than the bypass graft is preferred because of the lower long-term restenosis rate. Progressive development of friable vein graft atheroma is the principal factor for ischemia developing more than 3 years after CABG.62 Balloon angioplasty can be performed if the graft lesion is believed not to be friable and the graft has not degenerated. PICA of an old and friable vein graft stenosis is associ- ated with a greater than 20% risk of distal coronary embolization and non-Q wave myocardial infarction.63 Angioplasty is often used for di- lation of significant vein graft stenosis in patients who are not surgi- cal candidates because of multiple previous bypass surgeries or other medical illnesses, such as severe pulmonary disease or cancer. Al- though the restenosis rate is high, the amount of time before the de- velopment of restenosis may allow improvement of sufficient distal collateral flow to avoid subsequent disabling symptoms. The proce- dure is successful long-term in at least one half of patients. The pres- ence of extensive thrombus in a degenerated vein graft is preferably treated conservatively because of the high risk of embolization, myo- cardial infarction, and abrupt closure.64-68
b SK BAILEY: The increasing frequency of saphenous vein graft interventions re- fleets the rapid increase of patients with recurrent symptoms 5 to 10 years after bypass grafting as the grafts develop progressive stenoses. The results of balloon angioplasty of SVG stenosis is surprisingly good, Douglas et al. (Circulation lSS1;84[suppl IIl:II-2491 reported their experience with over 599 patients. They noted an 81% S-year survival, an event-free sun&al of 62%, and a 31% need for repeat revascularization. This was similar to the results seen in patients under- going native vessel PTCA during the same period. Unfortunately, angiographic restenosis was noted in 68% of proximal, 61% of midbody, and 45% of distal sites. ‘I’hese investigators also noted that the age of the graft did not predict the oc- currence of restenosis. Stent implantation in stenotic saphenous vein graft le- sions has shown exciting promise. The success rate is greater than 95% and the 2-year event-free sun&al rate is 87%, with an angiographic restenosis rate of only 26%, as reported by Pomerantz et al. (Am J Cardiol 1992;70:161-7). -
ANATOMIC CONSIDERATIONS
In appropriate clinical circumstances, further evaluation of coro- nary anatomy at the time of coronary angiography, including the
240 Cur-r Probl cardiol, May 1994
number of vessels diseased, the structure of the lesions, and the de- gree of left ventricular dysfunction, will determine the suitability for PICA. On the basis of the American College of Cardiology/American Heart Association Task Force report, it is now common practice to classify coronary artery lesions into types A, B, and C on the basis of the angiographic morphologic characteristics of the lesions. This morphologic classification is summarized in Table 2.17,18 This classi- fication provides a guide not only for estimating procedural success rates but also, and more importantly, for judging the risks of abrupt coronary closure. The general use may be limited by marked inter- observer variability, lack of definition of the modes of failure, and a relatively low positive and negative predictive value. In addition, in- creasing numbers of patients with unfavorable lesion characteristics, such as bifurcation lesions or total occlusions, are now undergoing FTCA with higher success rates and relatively lower risks as a result of technical advances in guide wires, dilation catheters, guiding sys- tems, and perfusion catheters, as well as improvements in operator experience.6s-72 In addition, the use of new interventional devices, in- cluding atherectomy, laser, and stents, have significantly increased the success of angioplasty in unfavorable anatomy.
Chronic total occlusions account for 10% to 20% of PTCA proce- dures in some centers and are also the most common reason for re- ferral for CABG (approximately 50% of cases). The occlusions are com- posed of an underlying atherosclerotic plaque Mrlth an occlusive thrombus. The texture of the thrombus (i.e., the age and the degree of fibrosis) determines the success rate of angioplasty. Although the primary success rate of eliminating chronic total occlusions remains low (75% if the occlusions are less than 3 months old versus 10% to 50% if the occlusions are more than 3 months old), the procedure is usually associated with a low complication rate.7”-7”
A well-collateralized total occlusion functionally behaves as a 90% stenosis.“” Distal collaterals usually do not deyelop in younger pa- tients with previous insignificant coronary disease and acute coro- nary occlusion in contrast to older patients with chronic coronary artery disease who have preexisting collaterals.81~8” PTCA of total oc- clusions may be considered to improve blood flow to areas of viable myocardium supplied by inadequate collateral flow or to provide col- lateral blood flow to other hemodynamically significant stenoses un- dergoing dilation so as to reduce the risk caused by serious closure of the other lesion.
Total occlusions flush at the orifice of the vessel or tapering into a small side branch, the presence of bridging collaterals, and total oc- clusions of bypass grafts are relative contraindications for angio- plasty.83 Adequate visualization of the distal part of the occluded ar- tery by way of collaterals is an absolute prerequisite for angioplasty because nonvisualization of the distal vessel may indicate occlusion
Curr Probl Cardiol, May 1994 241
TABLE 2. Characteristics of type A, B, and C lesions
Lesion-specific characteristics
Type A lesions ihigh success >85%; low risk) Discrete I<10 mm in length1 Concentric Headily accessible Nonangulated segment, <45’ Smooth contour Little or no calcification Less than totally occlusive Not ostial in location No major branch involvement Absence of thrombus
Type B lesions [moderate success, 60%-85% ; moderate risk)’ Tubular 110-20 mm in length1 Eccentric Moderate tortuosity of proximal segment Moderately angulated segment, >45’,
<90” Irregular contour Moderate to heay calcification Total occlusions <3 months old Ostial in location Bifurcation lesions requiring guide wires Some thrombus present
me C lesions llow success, <600/o; high riski Diffuse 1>2 cm in length) Excessive tortuosity of proximal segment Extremely angulated segments, >90° Total occlusion >3 months old Inability to protect major side branches Degenerated vein grafts with friable
lesions
From Ryan TJ. Patient selection: current status. In: Faxon DP, ed. Practical angioplasty New York: Raven Press, 1993:17. *Although the risk of abrupt vessel closure is mod- erate, in certain instances the likelihood of a major complication may be !ow, as in dilation of total oc- clusions less than 3 months old or when abundant collateral channels supply the distal vessrl
of the entire length of the vessel or irreversibly damaged distal myo- cardium.83 JTCA should also be avoided in patients with chronic to- tal occlusion with more than one additional lesion in the same ves- sel or with lesions that are more than 3 to 6 months old as deter- mined by clinical history. In patients with an acute myocardial in-
242 Curr Probl Cardiol, May 1964
farction of less than 6 hours and a totally occluded infarct-related artery, restoration of normal blood flow can salvage the ischemic myocardium and may improve the remodeling of myocardium, pro- vide collateral flow to other vessels, and decrease the risk of aneu- rysm formation, ventricular rupture, or ventricular arrhythmia.84-87 However, at present no data exist to support routine angioplasty of a totally occluded infarct-related artery more than 6 hours old in the absence of clinical evidence of significant ischemia or viable myocar- dium.
b S.R. BAILEY: The decision to intervene more than 6 hours after the onset of chest pain in the setting of myocardial infarction should be based primarily upon clinical criteria. Unfortunately, in one series only 9% of patients under- went functional assessment before coronary intervention after myocardial infarc- tion (Top01 E, et al. Circulation 1993;87:1489-973. It is difficult to avoid dilating the stenosis greater than 90% (the oculostenotic dilatory reflex). In a study of elective angioplasty after myocardial infarction in patients with clinical or thal- lium evidence of ischemia, angioplasty was performed on the basis of the angio- graphic appearance of the lesion. In the TOPS study IEllis S, et al. Circulation 1992;86:1400-ti), the acute closure rate of 9.5% with angioplasty was striking when compared with no closures in those patients observed who received medical therapy alone.
NEW CONSIDERATIONS IN MULTIVESSEL DISEASE
As evidenced by the data from the second NHLBI registry, more than 50% of patients undergoing angioplasty at present have mul- tivessel disease. The definition of multivessel disease varies in differ- ent studies. It has been defined as the following: (1) stenosis more than or equal to 70% in two or more arteries (i’0%-70%)~~-~~; (2) ste- nosis more than or equal to 70% in one artery and more than or equal to 50% in a second artery (70%-50%)~“~~; and (3) stenosis more than or equal to 50% in two arteries (50%-50% ).s3-s7 Most patients with multivessel disease undergoing PEA have two-vessel coronary artery disease and normal left ventricular function.88’s2 Recently published data from the BAR1 trial suggest that in patients with multivessel dis- ease, only 40% of patients can be revascularized by PTCA as opposed to 90% found to be suitable for CABG.” Patients with ongoing total occlusions, diffuse disease, left main coronary artery disease, and subtotal lesions with unfavorable lesion characteristics form the ma- jor reasons for referral for CABG. However, PTCA may be a preferred treatment strategy in certain groups of patients who are particularly high-risk surgical patients, such as elderly patients or patients with prior CABG.
Multivessel disease is a frequent finding in elderly patients under- going coronary angiography. The morbidity and mortality rates for elderly patients undergoing angioplasty or coronary artery bypass
Curr Probl Cardiol, May 1994 243
surgery are significantly higher than those for younger patients.” However, the mortality and morbidity rates are also significantly higher with CABG compared with FTCA in elderly patients.” There- fore, despite more common findings of unfavorable lesion character- istics,1oo RCA may be preferentially considered in suitable groups of patients because frequently the goal of angioplasty in this group of patients is not to achieve successful dilation of more than 50% of the lesions but to achieve improvement in symptoms through incomplete but functionally adequate revascularization without increased mor- bidity and mortality.
In contrast, younger patients with multivessel disease with pre- served left ventricular function are reluctantly referred for CABG be- cause of the belief that graft atherosclerosis may develop, with the need for repeat revascularization and associated increased risk of subsequent surgery.” Follow-up studies of young patients with CABG would suggest that such a belief, until subset analyses of large ran- domized trials are available, represents a bias toward PICA in young patients.s8S101
Most patients with prior CABG have multivessel disease. This group of patients are increasingly referred for PICA. They comprised 13% of patients referred for angioplasty in the second NHLBI registry,7 and in the BARI registry they comprised one third of all patients referred for revascularization.13 In addition, 50% of vein grafts develop ath- erosclerosis with significant obstructive disease by 10 years after sur- gery.lo2 Increased numbers of these patients are referred for RCA because a second CABG carries a higher risk of mortality as a result of the patient’s increasing age and associated illnesses. In addition, a second CABG often does not result in complete relief of angina. In approximately 50% of the patients, native coronary artery lesions may be dilated instead of grafts, supplying those arteries with a signifi- cantly lower risk of restenosis.ss
Coronary angioplasty in patients with multivessel disease may be approached as a staged procedure or as a single procedure (Fig. 21. In many instances, especially in unstable coronary syndromes, a single lesion is responsible for most or all of the symptoms, and di- lation of such a “culprit” lesion reduces the risk of serious complica- tions of angioplasty in these circumstances while relieving symp- toms. lo3~lo4 It is possible to identify a culprit lesion reliably in 30% to 80% of cases by electrocardiographic changes, radionuclide imaging, or coronary angiography.103-105 However, patients with unstable rest angina and multivessel disease may be better served with complete revascularization rather than culprit vessel angioplasty.106”07
b S.R. BAILEY: The risk of complications also rose in patients with multivessel disease. The 198.51986 National Heart, Lung, and Blood Institute registry re- ported death in 0.2% of patients with one-vessel CAD, in 0.9% of patients with two-vessel CAD, in 2.2% of patients with three-vessel CAD, and in 8.1% of a small
244 Cur-r Probl Cardiol, May 1994
FIG. 2. Multivessel angioplasty in a single session. A, Successful dilation of complex proxi- mal rtght coronary artery (left anterior oblique view). B, Recanalization of long-term total occlusion of proximal left anterior descending artery (right anterior oblique view).
group of patients with left main disease. Nonmorbid complications followed the same trends, on the basis of severity of the disease.
In multivessel angioplasty as a single procedure, angioplasty of the lesion that supplies the greatest amount of viable myocardium should be performed first. If suboptimal results occur, a staged pro- cedure should be performed, with subsequent dilation of remaining lesions after 24 to 48 hours. The risk of abrupt closure is significantly higher in patients with suboptimal results 1>50% residual stenosis or significant coronary dissection) .108P10s Usually abrupt closure oc- curs in minutes to hours after the procedure; its occurrence more than 1.2 hours later is relatively rare.llO’lll If a totally occluded vessel receives a collateral from another vessel with a hemodynamically sig- nificant stenosis, the occluded vessel should be dilated first because it may provide collateral flow to the other stenosis in case of its abrupt closure. If all lesions are equally significant, the more difficult lesion should be dilated first. In hours to days immediately after myocar- dial infarction, only the infarct-related artery should be dilated. In the staged procedure one lesion is dilated initially, followed by FICA in the remaining lesions 1 day to several days later. The advantages
Cum Probl Cardiol, May 1994 245
of this strategy are less risk of dye-induced acute kidney failure and less risk of multivessel closure with increased chances of death. How- ever, the disadvantages are a longer hospital stay, increased discom- fort to the patient, and increased cost. For these reasons, in the BAR1 trial less than 5% of patients were staged.
CONTRAINDICATIONS
Factors generally considered contraindications for PTCA are sum- marized in Table 3.l’ High-risk anatomy, such as left main stenosis (>50% I, is regarded as an absolute contraindication unless it is pro- tected by at least one completely patent graft to left coronary circu- lation.
Relative contraindications vary according to the symptomatic state of the patient (severity of symptomsJ, degree of left ventricular dys- function, and the presence of other advanced comorbid conditions, such as severe pulmonary disease, cancer, or anoxic encephalopa- thy. The risk of PTCA may be justified in appropriately selected pa- tients with severe symptoms who are not candidates for CABG, whereas the risk may be inadvisable in patients with mild symptoms.
The absence of onsite surgical backup, experienced and qualified PEA operators, and adequate imaging equipment are relative con- traindications to angioplasty. Type C lesion structure suggesting a low success rate or a high complication risk that supplies a moder- ate to large area of viable myocardium is a relative contraindication for PTCA unless it is the only option. Similarly, PICA is contraindi- cated in lesions with less than a 50% diameter reduction as measured by the caliper method and in patients with no clinical or objective
TABLE 3. Factors associated with restenosis
Recent onset angina Unstable angina Variant angina Diabetes mellitus Elevated blood insulin levels Multivessel disease Stenosis at the origin of vessel Stenosis in proximal or mid portion of
saphenous vein graft Chronic total occlusion Presence of thmmbus Severity of residual lesion
From Rvan TJ. Patient selection: current status. In: Faxon DP, ed. Practical angioplasty New York: Raven press, 199327.
Cur-r Probl CardioI, May 1994
evidence of myocardial ischemia because inherent to the strategy of mCA is the risk of serious complications (3% to 6% J and late risk of restenosis (30% after 6 months).
b P.M. SHAH: The absence of surgical backup, a paucity of experienced and trained operators, and inadequate imaging equipment should constitute abso- lute contraindications to angioplasty. Cerainly, no cardiologist would willingly subject himself or his loved ones to the procedure under these circumstances. The final contraindication noted by the authors is really a nonindication (that is, it belongs in the “if it ain’t broke don’t fix it” category]. -
SUCCESS AND COMPLICATIONS
The expected outcome from PI’CA has substantially improved since the initial success rate of 64% reported by Gruentzig in the first 50 procedures and reported in the first NHLBI registry.” Currently, the primary angiographic success rate exceeds 90% for most elective pro- cedures. The definition of a successful angioplasty has varied in dif- ferent studies.1’2-117 A generally acceptable definition of angiographic success is a reduction in the diameter of the lesion of 20% or more dilated with a residual diameter less than 50%. Clinical success is usually defined as angiographic success plus the absence of major in-hospital complications (myocardial infarction, CABG, or death,.
A number of patient-related factors and angiographic characteris- tics have been identified by previous prospective trials to predict a low success rate and high complication rate. Patient-related factors considered high risks for PTCA are age (>70 years of age), female gen- der, history of hypertension, diabetes mellitus, prior myocardial in- farction or CABG, and presence of left ventricular dysfunction.18 How- ever, in a recently published study by Savage et al.,l18 clinical factors such as age, sex, race, history of diabetes mellitus, or prior myocar- dial infarction or smoking did not predict the success rate of angio- plasty in the patients enrolled in Multi-Hospital Eastern Atlantic Re- stenosis trial.
b P.M. SHAH: The terms ‘success” or “successful” angioplasty should be quali- fied to indicate immediate success in achieving dilatation. The ultimate success can only be determined in the long term, because it seems that one third to one half of patients show evidence of restenosis over an intermediate follow-up of 6 months.
Angiographic characteristics of the vessels and the lesions may be more important than patient characteristics in predicting the success rate and the risk of abrupt vessel closure. As reported by the Ameri- can College of Cardiology/American Heart Association Task Force,17 Myler et al.,ll’ and Ellis et. al.,“’ type A lesions have an anticipated success rate of more than 85% to 90%, with low risk of in-hospital complications (<4% 1. Type B lesions have a moderate success rate
Cur-r Probl Cardiol, May 1994 247
160% to 85%), moderate risk of abrupt vessel closure (<S%J, or both, However, patients with certain type B lesions, such as total occlu- sions (<3 months), or with a large number of distal collaterals may have a low likelihood of major complications (Q-wave myocardial in- farction, CABG, or death) despite the high risk of abrupt vessel clo- sure because reocclusion merely reinstitutes the preangioplasty state. Type C lesions have a less than 60% success rate, more than an 8% risk of abrupt vessel closure, or both. More recent studies, including that by Myler et al.,ll’ demonstrate that with the use of current bal- loon techniques, the success rate in type C lesions is much better than previously reported. Certain lesion characteristics, such as ec- centric structure and lesion length, may no longer predict an adverse outcome.“’
On the basis of clinical and angiographic characteristics, patients can be classified into low- and high-risk groups. For instance, a 45- year-old man with a single 70% type A left anterior descending ar- tery lesion has an anticipated success rate of more than 95% and mor- t‘ality rate of less than O.l%, whereas a 70-year-old woman with triple- vessel disease and left ventricular dysfunction and a type C lesion has a success rate of 60% and a mortalitv rate of 3.5%.
b S.R. BAILEY: Several angiographic criteria are helpful in deciding if a totally oc- cluded lesion can be recanalized. These include a terminal tapered shape or “funnel” appearance, length of the vessel that is occluded, and the absence of bridging collateral vessels. In our experience, these angiographic criteria are more important in predicting success than the duration of the occlusion.
For total occlusions the primary procedural success rates vary from 10% to 70%. 73-7s The most important factor predicting success is the age of occlusion. Success declines especially during the first 4 weeks after occlusion because thrombus reorganizes with an increasing amount of fibrosis. If total occlusions are more than 3 months old, the primary success rate declines to less than 20%. Newer devices such as the magnum guide wires or over-the-wire excimer laser an- gioplasty may improve the primary success rate of angioplasty of to- tal occlusions.120’1”1
It is important to reemphasize that in patients with unstable an- gina, despite a high immediate success, PTCA has a significantly greater risk of serious complications, including acute coronary oc- clusions, emergency CABG, or death. Pretreatment of such groups of patients with aspirin and heparin for several days rather than imme- diate PTCA improves the outcome and should be conducted if clini- cally feasible. Similarly, the immediate success rate of angioplasty to reestablish coronary blood flow as primary therapy in acute myocar- dial infarction or as an adjunct to thrombolytic therapy in patients with acute myocardial infarction is approximately 90%.122S123 How- ever, the rate of reocclusion and in-hospital mortality exceeds that of
24s Curr Probl Cardiol, May 1994
elective FICA, especially in patients with persistent occlusion or re- occlusion of an infarct-related artery. As evidenced by data available from three large controlled randomized trials (Thrombolysis and An- gioplasty in Myocardial Infarction, Thrombolysis in Myocardial In- farction, and European Cooperative Study Group), immediate empiric FICA within hours of thrombolytic therapy for acute myocardial in- farction is associated with higher risk and no clear benefit.27’30’“1
Similar to cardiac catheterization, FICA is associated with poten- tial complications of vascular injuries (arterial or venous perforations, obstruction, pseudoaneurysms, or fistulas); myocardial infarction; bleeding; radiographic contrast agent toxicity, including allergic re- actions or kidney failure; and cerebrovascular accidents. In addition, angioplasty is associated with unique complications of coronary dis- section and abrupt vessel closure. Data from the NHLBI registry sug- gest that in patients undergoing routine elective balloon angioplasty the hospital mortality rate is 196, the need for emergency CABG is 2?6 to 3%, and the incidence of nonfatal myocardial infarction is approxi- mately 4% .7 More recent data suggest that those rates have been re- duced by 50% or more.108 Although many factors may be responsible for the improved success rate and reduced complication rate, the most important are improvements in angioplasty equipment, case se- lection, and operator experience. Some infrequent complications as- sociated with PICA are distal embolization of atherosclerotic plaque or thrombotic material (especially in an old saphenous vein graft), coronary perforation (especially in total coronary occlusions), rupture of coronary artery with hemopericardium, and, rarely, cardiac tam- ponade.
As shown in the second NHLBI registry data, major complications with balloon angioplasty are seen in 5.5% of patients with one-vessel disease, 8.1% of patients with two-vessel disease, and 9.3% of patients with three-vessel coronary artery disease.’ In patients undergoing an- gioplasty of a total occlusion, abrupt closure is common; however, the risk of complications with Q-wave myocardial infarction or the need for coronary bypass surgery is uncommon.74-7y In this group of patients perforation with guide wire is infrequent but relatively more common than in routine angioplasty.
ARRUF’TVESSELCLOSURE
Balloon inflation during PICA results in improvement in arterial lumen mostly as a result of “cracking” of the atheroma and expan- sion of the arterial wall caused by plastic stretching of the media and adventitia.lz4-lz6 In the process of achieving an adequate dilation, “controlled injury” is inflicted on the lesion. In most patients con- trolled vessel trauma with intimal dissection does not interfere with
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antegrade flow and heals by reendothelialization in 4 to 6 weeks af- ter the procedure. Occasionally, excessive balloon dilation because of a large balloon-artery size ratio, high-pressure inflations, or guide wire or guiding catheter trauma may cause extensive intimal-medial dissection with intimal flap formation.127 Either occlusive intimal flap or thrombus formed at the site of intimal-medial trauma may exac- erbate the coronary stenosis with abrupt coronary arterial closure and development of myocardial ischemia-infarction or even cardio- vascular collapse.‘z8 Other factors that may contribute to severe ves- sel closure include embolization of atheromatous material or throm- bus distally, subintimal hemorrhage, and coronary vasospasm.1zs-13’ Assessment of the relative role of each of these factors cannot be re- liably determined by angiography in an individual patient, although it is likely that the intimal occlusive flap accounts for most severe abrupt closures. In the absence of significant distal collaterals, abrupt coronary occlusion will result in severe myocardial ischemia or in- farction with or without cardiovascular collapse if coronary blood flow is not reestablished immediately.
b P.M. SHAH: It must be acknowledged that the operator performing the angio- plasty has little if any control over the “injury” or “dissection” that may result. Thus even though “controlled injury” is an objective for a successful outcome, there is little control exercised by the operator. In reality, it amounts to perform- ing the angioplasty and hoping or praying that the resultant injury is “controlled” and not extensive.
Some of the common factors identified by multivariate analysis to be predictive of abrupt closure are branch point stenosis, angulated lesion, presence of other stenosis in the same vessel (more than 50% 1, long (greater than 20 cm) lesion, post-PICA residual stenosis of more than 50%, presence of intimal dissection, and post-PTCA heparin in- fusion. 1os~132J133 However, it is important to recognize that abrupt ves- sel closure still remains largely unpredictable. The most important characteristics that prospectively identify patients at high risk for he- mod”ynamic collapse when abrupt closure develops are the amount of myocardium at risk, the degree of stenosis and diffuse disease in the lesion to be dilated, and the presence of hemodynamically sig- nificant lesions in other coronary arteries.
,- S.R. B. MLEY: Intravascular ultrasound imaging pmvides important information about the vessel wall architecture. This will surely help us to better characterize high-risk lesions such as those with calcium present and choose optimal device sizing to decrease the risk of complications such as arterial dissection.
The incidence of abrupt vessel closure after balloon angioplasty is approximately 4% to 5% in the cardiac catheterization laboratory. An additional 2% to 5% occur within the first 24 hours.‘osS111 Abrupt clo- sure accounts for 50% of all the major complications of angio-
250 Curr Probl Cardiol, May 1994
plasty.‘32J133 In most patients with abrupt coronary occlusions, coro- nary arterial patency can be reestablished by the use of prolonged inflations with conventional balloons or perfusion catheters, use of directional atherectomy, intracoronary thrombolytic agents or arte- rial vasodilators, or the placement of intravascular stents. The perfu- sion balloon has proximal and distal lumens that permit passive blood flow during balloon inflation. A prolonged inflation of 20 min- utes has been reported to treat abrupt closure successfully in up to 70% of patients.134 In recent years, intracoronary stents have emerged as one of the preferred approaches in a select group of patients with impending or established abrupt closure.‘35~‘37 In patients with a suboptimal result after balloon angioplasty and a significant dissec- tion with impending coronary occlusion, placement of single or mul- tiple tandem stents have been shown to avoid severe total coronary occlusion. It must be remembered, however, that stents in themselves increase the risk of acute or subacute thrombosis.13’ Therefore me- ticulous adherence to suggested intensive anticoagulation protocol is an integral part of the management of intravascular stents. The presence of extensive thrombus causing severe closure is a relative contraindication for placement of a stent. Recently, the Gianturco- Roubin stent has been approved by the Food and Drug Administra- tion for this indication. This stent may reduce the need for emergency bypass surgery and might obviate the need for in- hospital surgical standby during PICA in the future. The use of an intraaortic balloon pump or percutaneous cardiopulmonary bypass also may reduce the degree of ischemia created by abrupt vessel closure. In approximately 2% of cases, when these measures fail to establish adequate distal coronary perfusion and severe ischemia and the related ventricular dysfunction develop, emergency bypass surgery is required. The incidence of myocardial infarction and death is increased significantly during these settings despite prompt surgical revascularization (25% to 40% incidence of nonfatal myocardial infarction) .13’
The abrupt closure occurring out of the cardiac catheterization laboratory may be the result of spasm or thrombus at the site of dis- section or some combination. If the patient is hemodynamically stable, the physician should check the activated clotting time (ACT). If the ACT is less than 300, intravenous heparin should be adminis- tered and heparin infusion maintained to keep the ACT above 300. Simultaneously intravenous nitroglycerin may be administered to re- duce coronary spasm and platelet aggregation. Blood pressure should be maintained above the 100 mm Hg systolic level and above the 60 mm Hg diastolic level. If these measures do not immediately improve the situation, then the patient should be returned to the car- diac catheterization laboratory, and coronary patency should be re- established by repeat angioplasty. In most cases, these measures are
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successful in reestablishing the coronary flow without the need for emergency surgical revascularization.‘40
b S.R. BAILEY: Continuous monitoring of the ST segments in patients after coro- nary intervention and their release from the catheterization laboratory can pm- vide an early warning of impending vessel closure. A study by Kmcoff et al. (Cir- culation 1990;81[suppl IVJ:IV-20) demonstrated that ST segment elevation identi- cal to that occurring in the catheterization laboratory during balloon inflation occurred in 92% of patients who went on to suffer an MI, who required CABG, or who died during that hospitalization.
FLESTENOSIS
The long-term benefit of coronary angioplasty is reduced in 30% to 40% of patients because of the recurrence of a stenosis at the site of an initially successful dilation.141-145 From experimental studies it appears that the universal responses to arterial trauma from angio- plasty are platelet adhesion and aggregation, thrombus formation, and inflammatory cell infiltration at the site of injury. Multiple growth factors and cytokines derived from platelets and inflamma- tory cells result in migration and proliferation of smooth muscle cells and subsequent organization of connective tissue matrix.146-148 Late arterial remodeling and arterial spasm play an equally impor- tant role.14’ The contribution of smooth muscle cell proliferation and arterial wall remodeling in an individual patient may vary. The reparative process is usually completed by 3 to 4 months and rarely extends beyond 6 months.150’151 The degree of this response varies in different patients but leads to angiographic restenosis, which is defined as a stenosis of more than 50%, in 30% to 40% of patients. Angiographic restenosis may occur with or without clinical symp- toms. The wide range of definitions of restenosis and incomplete angiographic follow-up in many studies may account for the reported differences in angiographic restenosis rates, which range fI>om 18% to 60% ,112,115-117,150-161 Seven commonly used definitions of restenosis exist. The two most common are a stenosis of more than or equal to 50% luminal diameter at follow-up or more than or equal to 50% loss of initial gain in cross-sectional luminal diameter. Recent quantitative angiographic studies have shown that restenosis is a continuous process that occurs to some degree in nearly all patients.14’ Thus it may be more appropriate to define restenosis as the change in minimal luminat diameter. Current clinical trials have used this definition because it is more sensitive and better reflects the underlying biologic process.150,151 The observed incidence of angiographic restenosis increases progressively over a period of 1 month after the angioplasty, reaching maximum percentage at approximately 3 months, and becoming rare after 6 months.150”51
252 Curr Probl cardiol, May 1994
b P.M. %AH: Although others may differ, I believe the most important statement in this monograph is the one above that U. restenosis is a continuous process that occurs to some degree in nearly all patients.”
Clinical restenosis is defined as recurrence of ischemic symptoms within 6 months after PEA. Most clinical observation studies have used clinical restenosis rather than angiographic restenosis as the major end point because it is more clinically relevant although less sensitive and objective. After angioplasty, approximately 20% of pa- tients return within 6 months with progressively increasing angina after an early period without symptoms.143,144,162-164 The restenosis process is gradual and rarely progresses to acute myocardial infarc- tion (less than 2% of patients). If a patient returns with angina more than 6 months after the procedure, usually the chest pain is the re- sult of progression of disease in other vessels.
b S.R. BAILEY: Recurrent chest pain is not specific for restenosis of the artery at the angioplasty site. Only 60% of patients with recurrence of typical angina within 6 months of angioplasty will have angiographic restenosis. Fifteen percent of asymptomatic patients will also have angiographic restenosis during the 6 months after PTCA (Holmes D, et al. Am J Cardiol 1984;53:77c-SW.
b S.R. BAILEY: Although improvement in symptomatic status is common after an- gioplasy, no study has shown improved survival after elective angioplasty. This is not surprising since only patients with left main coronary artery stenosis, proximal three-vessel disease with left ventricular dysfunction, and proximal LAD and a totally occluded RCA have been shown to have improved survival with surgery. These patient subsets are less likely to undergo balloon angioplasty be- cause of their increased procedural risks and a decreased likelihood of complete revascularization.
A number of patient characteristics and anatomic considerations are associated with a significantly higher risk of restenosis. Some of these factors are outlined in Table 3.18 Restenosis rates are reported to be higher in men, in patients with history of diabetes mellitus or continued smoking, and patients with unstable or variant angina.165-174 Angiographic characteristics that are associated with higher risk of restenosis are left anterior descending artery disease, ostial left anterior descending artery and right coronary artery le- sions, saphenous vein grafts, lesions at bend points, long lesions, and ongoing total occlusions.76,171S175-18” Patients with multivessel disease have a higher restenosis rate than those with single-vessel disease, although the rate per lesion dilated is actually less.ls7 This situation explains why patients with multivessel disease have only one third higher risk of restenosis than patients with single-vessel disease. The clinical restenosis rate in this subgroup of multivessel disease is ap- proximately 34%) whereas the angiographic restenosis rate is ,50~~89,96,S7,188-192 Multiple lesions in the same vessel have a resteno-
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sis rate similar to multivessel disease.1g3’194 If a residual lesion is less than 30% after angioplasty, then the rate of restenosis defined as less than 50% stenosis remains significantly lower.171 The factors related to restenosis are also dependent on the definition. When restenosis is defined as the change in minimal luminal diameter, then the most important determinants are the initial gain and the final minimal lu- minal diameter.
A number of therapies may be used on the basis of potential patho- physiologic mechanisms (Table 4).*s5 More than 50 well-designed
TABLE 4. Potential mechanisms of restenosis and future directions of therap.y
From Brush JE Jr. Clinical features of restenosis fol- lowing cornnary angioplasty. In: Faxon DP, ed. Prac- tical angioplasty. New York: Raven Press, 1993. ACE, Angiotensin-converting enzyme.
Curr Probl Cardiol, May 1~94
clinical trials have used antithrombotic, antiproliferative, antiinflam- matory, antispastic, and lipid-lowering agents in the last 8 to 10 years without any demonstrable reduction in the rate of restenosis.1g6-z1” Despite the failure of most treatments, it seems likely that with fur- ther explanation of the biologic mechanisms responsible, an effec- tive therapy or combination of therapies will be developed. A num- ber of new devices that were designed to reduce the amount of arte- rial wall injury and thereby lower the restenosis rate have also failed to make any major impact; however, each may be used as preferred therapy in specific circumstances. Directional atherectomy is useful in larger coronary arteries for complex ulcerated eccentric lesions, ostial lesions (especially aorta-ostiall, saphenous vein graft lesions, and restenosis lesions.217-Z1Y A recent clinical trial (CAVEAT I) showed a reduction in restenosis with directional coronary atherectomy; however, serious complications were higher.‘l’ Rotational atherec- tomy may be useful for long, calcified tortuous lesions or for ongoing total occlusion when the balloon cannot be passed across the le- sion.z20~221 Laser-assisted angioplasty is useful for lesions not well suited for balloon FTCA (e.g., long or ostial lesions and lesions resis- tant to high-pressure balloon inflations), or type C lesions.222~223 In- tracoronary stents are useful for impending abrupt closure and de- generated saphenous vein grafts.224”25 Again, two recent clinical tri- als suggested that a benefit in reducing restenosis exists, although cost, subacute thrombosis, and the risk of bleeding limit its wide- spread use.226S227 Importantly, both directional atherectomy and stents reduce restenosis by creating a larger lumen after FICA, which reemphasizes that the better the initial result regardless of the drugs used, the lower the restenosis rate.
b P.M. SHAH: Since the possible therapeutic approaches listed in Table 4 to pre- vent restenosis have all proved unsuccessful to date, there is little point in high- lighting them in the table. The reader may be misled into believing that the po- tential of therapy has been realized to some extent.
b P.M. SHAH: The authors state that based on the results of CAVEAT I, there is a reduction in restenosis with DCA. However, in the previous section on current indications the authors refer to CAVEAT II to indicate that DCA failed to show a reduction in restenosis. This could be confusing to the average reader unless the discrepancy between the two CAVEAT studies is explained!
Recurrence of typical and worsening angina1 symptoms after a pe- riod without symptoms indicates a high likelihood of restenosis, and evaluation with coronary angiography should be performed expedi- tiously. If a patient has atypical symptoms after a successful angio- plasty, exercise thallium or other noninvasive testing may be done initially to evaluate for the presence of significant ischemia in the same myocardial segment; however, false positive results are com-
Curr Probl Cardiol, May 1994 255
mon, especially early after the angioplasty.Z28~z2y If a patient returns 6 months after coronary angioplasty with anginal symptoms, usually the symptoms are due to a progression of disease in arterial segments that did not undergo angioplasty and are not likely due to resteno- sis.
Rates of clinical restenosis after first, second, third, and fourth an- gioplasties are 20%, 26%, 37%, and 50%, respectively.230 The charac- teristics that have been identified by multivariate analysis to be inde- pendent predictors of recurrent restenosis are male gender, long le- sions, history of diabetes mellitus, hypertension, unstable angina, and, most important, the recurrence of symptoms within 60 days of the first angioplasty.‘31-233 Treatment of recurrent restenosis involves repeat angioplasty, although after a second restenosis the choice of angioplasty versus CABG is based on patient preference and indi- vidual bias. The success rate of repeat angioplasties is high (93% 1 and the morbidity is low when compared with CABG.234,235 In addition, the expense of angioplasty is lower or equal to CABG for the first and second angioplasties.236 Out of the patients initially referred for an- gioplasty, approximately 10% of those with single-vessel disease and 25% to 30% of those with multivessel disease are subsequently re- ferred for CABG.
LONG-TERM OUTCOME
Although the use of angioplasty as revascularization therapy for ischemic syndromes has expanded considerably during the last 15 years, its role in comparison with medical or surgical therapy has not been evaluated in large-scale, randomized, controlled trials. The Angioplasty Compared with MEdical therapy (ACME) study evaluated the effects of medical therapy versus angioplasty on angina and ex- ercise tolerance in patients with single-vessel coronary artery dis- ease.2”7 A total of 212 patients with single-vessel coronary artery dis- ease (70% to 99% stenosis) and exercise-induced myocardial ischemia were randomized to medical therapy (107 patients) and PICA (105 patients). At 6-month follow-up, the PTCA group had better relief of angina (46% versus 64%, medical versus PICA) and improved exer- cise tolerance (2.1 minutes compared with baseline in the PTCA group versus 0.5 minute compared with baseline in medical therapy). However, ITTCA was associated with a greater frequency of complica- tions and longer hospital stay compared with medical therapy. A re- cently published 3-year follow-up study of these patients showed that even at 3 years, 62% of the patients in the PTCA group remained angina-free compared with 50% of the patients receiving medical therapy.238 The significantly improved exercise tolerance in the PTCA group also persisted at the S-year follow-up despite a more frequent
256 Cum Probl Cardiol, May 1994
need for revascularization procedures (late PTCAXABG) in patients randomized to medical therapy.
The long-term follow-up data available at present suggest that an- gioplasty should be considered the procedure of choice in patients with single-vessel disease and a select group of patients with mul- tivessel disease. A recently published lo-year follow-up of the first 133 successful single-vessel angioplasty procedures performed by Gru- entzig between 1977 and 1980 showed a survival rate of 95% for pa- tients with single-vessel disease and a survival rate of 81% for patients with multivessel disease.23g In this group, 58% of patients had single- vessel disease and 42% had multivessel disease. Overall, approxi- mately 50% of patients underwent repeat revascularization proce- dures including angioplasty or CABG. After 10 years of follow-up, ap- proximately 80% of patients with single-vessel disease were free of angina or CABG surgery, compared with approximately 70% of pa- tients with multivessel disease. Similarly, the 5-year follow-up data from the NHLBI registry indicate that for patients with single-vessel disease, the annual mortality rate was approximately 1% per year and the rate of nonfatal myocardial infarction was 2% per year.240 Free- dom from recurrent symptoms and major cardiac events (death, myo- cardial infarction, need for bypass surgery) has been reported to oc- cur in approximately 70% to 80% of patients at 4 years of follow-up.241 Similarly, previous studies in patients undergoing angioplasty for multivessel disease show that 83% of patients did not have any car- diac events during a 3year follow-up period.242 Overall, patients with single-vessel disease have better long-term outcomes than patients with multivessel disease. The long-term outcome after angioplasty compares favorably with the results after CABG surgery. It is well es- tablished that after CABG most patients (95% ) have relief from angina, with 50% being completely free of angina and the rest with substan- tial relief of angina. However, only about 75% of patients are free of recurrent angina or major cardiac events (myocardial infarction or death) at 5 years of follow-up. This rate falls to 50% of patients at 10 years of follow-up because of the development of progressive athero- sclerosis in native coronary arteries distal to the sites of bypass graft insertions or bypass grafts themselves. At 15 years of follow-up, only 15% of patients remain free of angina, myocardial infarction, or death.3Q The reoperation rate for recurrent symptoms is 6% to 8% per year.41 Similar to angioplasty, the reported mortality rate after by- pass surgery is approximately 1% per year for the first 5 years, and the rate of recurrent fatal or nonfatal myocardial infarction is approxi- mately 2% per year. The overall survival rate after bypass surgery at 10 years is 81% .4’
The short-term results (1 to 2.5 years of follow-up) from a number of recently published randomized controlled trials comparing angio- plasty with coronary bypass surgery suggest no major difference in
Curr Probl Cardiol, May 1994 257
the primary end oints of death and myocardial infarction between the two groups.’ 3-247 r Symptom relief is less from angioplasty, and the recurrence of angina with increased need for antianginal therapy is higher in patients undergoing angioplasty as the initial strategy. The interim results from the Randomized Intervention Treatment of Angina (RITA) trial that randomized 501 patients to CABG and 510 patients to PTCA showed that, although the immediate surgical mor- tality rate is higher compared with angioplasty, at 2.5 years of follow- up, the combined end results of death and myocardial infarction are similar in both groups, approximately 9% to 10% .243 However, repeat revascularization procedures were more common in the PICA group compared with the CABG group, 38% versus 11%. At 6 months follow- up, 32% of the patients initially treated with PTCA had angina as com- pared with 11% of patients randomized to CABG, although this dif- ference narrowed over time. At 2 years follow-up, 61% of patients in the PTCA group were taking at least one antianginal medication as compared with 34% of patients in the CABG group. Notably, in the patients assigned to the CABG group, 97% of arteries selected for treatment were successfully grafted, and an internal mammary graft was used as one of the conduits in 75% of patients. In contrast, in the PTCA group, successful dilation of all the arteries selected for treatment was achieved in 90% of the arteries with subtotal occlu- sions and in only 48% of patients with total occlusions seen at the initial angiogram. This situation suggests that complete revascular- ization was more commonly achieved in patients randomized to the CABG group. The Randomized Intervention Treatment of Angina trial is the only trial that also included patients with single-vessel disease. A total of 45% of patients enrolled in the trial had single-vessel dis- ease. It is important to recognize that in the Randomized Interven- tion Treatment of Angina trial the similar results in terms of mortal- ity rate, myocardial infarction, and relief of angina were seen in pa- tients with single-vessel disease and multivessel disease. Similar re- sults have been reported from other randomized trials, including the German Angioplasty Bypass-Surgery Investigation trial that prospec- tively randomized 358 patients, 179 in each group, with at least a two- vessel disease requiring complete revascularization.244 Periproce- dural myocardial infarction was more common in patients undergo- ing CABG as compared with PTCA, 8.3% versus 2.4%, respectively. In contrast, at l-year follow-up three patients in the PTCA group sus- tained myocardial infarction as opposed to none in the CABG group. The incidence of recurrence of class 3 or 4 angina was similar in both groups at 1 year (7% 1. However, reinterventions were required in 45% of patients in the PEA group as compared with only 6% in the CABG group. Because bypass graft failure occurs primarily after 5 years, long-term follow-up will be necessary to appreciate fully the effect of these two strategies. Although it would be premature to extrapolate
258 Curr Probl Cardiol, May 1994
the results of these trials to clinical practice until more long-term re- sults are available, these studies do suggest that angioplasty is fea- sible in multilesion disease and can be performed as an initial strat- egy, with CABG performed at a later date if needed, without signifi- cantly increasing the risk of myocardial infarction or death. In addi- tion, angioplasty can be used as an initial stratea to delay the need for coronary bypass surgery in younger patients and to relieve symp- toms in elderly patients or patients with severe comorbid disease, such as severe pulmonary disease or malignancy, and in patients af- ter bypass. Because bypass surgery results more commonly in com- plete revascularization compared with PICA, it may be preferred to PICA in patients with class 3 or 4 angina, in patients with more ex- tensive ischemia by objective testing, and especially in patients with reduced left ventricular function.
INCOMPLETE REVASCULARIZATION
In patients with coronary artery disease, especially multivessel dis- ease, the goal of revascularization therapy is to achieve complete re- vascularization. The definition of complete revascularization in pa- tients undergoing PTCA has varied in different studies and is com- monly defined as either successful dilation of all lesions with a 50% or more diameter stenosis8s~s5~248 or successful dilation of all lesions with a 70% or more diameter stenosis.” Defining success as dilation of all lesions with a 70% or more diameter stenosis, complete revas- cularization by PICA is achieved in 45% to 50% of patients with two- vessel coronary disease and 40% to 45% of patients with three-vessel coronary disease.s1~s2~s4~24s Incomplete revascularization by PICA is most often due to total occlusions or diffuse coronary disease that is unapproachable by balloon angioplasty.g1’s4 Surgical revasculariza- tion is considered complete if bypass grafting is performed on each major epicardial coronary artery with a significant stenosis or the number of bypass grafts are equal to or more than the number of diseased vessels.250~252 The incidence of complete surgical revascu- larization in patients with multivessel disease is approximately 70% to gyyo .243,250- 53 Factors leading to incomplete surgical revasculariza- tion are: (1) technical factors that make it unfeasible to bypass all ar- terial segments with significant stenosis; (2) the presence of signifi- cant diffuse coronary disease distal to the site of graft placement; (31 the placement of graft to the distal segment of coronary artery with a proximal stenosis-limiting retrograde flow into a side branch; (4) placement of graft into an arterial segment supplying infarcted myo- cardium that is not functionally significant; and (5) the development of in-hospital or early postdischarge graft occlusion and the late de- velopment of graft atherosclerosis.
Curr Probl Cardiol, May 1994 259
The earlier surgical series have demonstrated that complete revas- cularization reduces morbidity and long-term adverse cardiac events, including death, compared with incomplete revascularization.250~z54 However, subsequent analyses of the same data with multivariate analysis suggest that degree of left ventricular dysfunction and other baseline clinical characteristics may be more important than degree of revascularization.106’254-z56 If the goal of therapy is to relieve symp- toms, functionally adequate but anatomically incomplete revascular- ization by PICA may be an acceptable option in the appropriate group of patients with multivessel disease. This option may be pre- ferred in patients with a total occlusion of a vessel supplying an in- farcted myocardial segment with the presence of a second hemody- namically significant lesion in which dilation of the second subtotal occlusion is an acceptable therapy to relieve ischemia and symptoms. If the goal of revascularization therapy is to prolong survival, the need for incomplete versus complete revascularization will depend on the severity of ischemic burden and the degree of left ventricu- lar dysfunction.1068254 In patients with class 3 or 4 angina, espe- cially with left ventricular dysfunction, complete surgical revas- cularization improves long-term survival. This finding was demonstrated by a report from the Coronary Artery Surgery Study registry, which showed that in patients with three-vessel dis- eases and mild angina, the degree of revascularization corre- lated with the long-term cardiac event rate.257 Similarly, in pa- tients undergoing coronary angioplasty for severe rest angi- na, incomplete revascularization has been shown to predict subse- quent adverse cardiac events.258 If the amount of ischemic myocar- dium revascularized with FTC4 and CABG is similar, then a similar survival benefit would be expected, and the choice of therapy would then depend on the feasibility of achieving complete revasculariza- tion with an acceptable risk of the procedure under consideration. Recently published early results of randomized trials of FTCA versus CABG show no short-term differences between the two groups in terms of survival and freedom from myocardial infarction.243-247 However, incomplete revascularization in patients assigned to PEA resulted more commonly in the recurrence or persistence of angina requiring antianginal medical therapy and repeat PICA, CARG, or both. Thus incomplete revascularization appears to be a major limitation of angioplasty at present. The major limitations of bypass surgery are the increased risk and lower success of reoperation. In contrast, multiple repeat angioplasty procedures can be per- formed with the same or less risk and with a high rate of success, the only limiting factor being increasing clinical restenosis rates with repeat procedures. Therefore, in a select group of patients with multivessel disease, PTCA appears to be an acceptable therapeutic strategv.
260 Cur-r Probl Cardiol, May 19%
ACUTE MYOCARDIAL INFARCTION
It is now well established that the underlying pathophysiologic mechanism for acute myocardial infarction is an occlusive coronary thrombosis developed over a ruptured atherosclerotic plaque.25g The most important therapy for myocardial salvage is the reestablishment of coronary blood flow to the myocardial territory supplied by the artery as rapidly as possible. Administration of thrombolytic therapy within 6 hours of the onset of chest pain and possibly within 12 hours is associated with improved survival. 260,261 It is also clear that the ear- lier the establishment of the coronary blood flow, the larger the amount of myocardium salvaged.87 Thrombolytic therapy fails to es- tablish coronary artery patency in approximately 20% to 30% of pa- tients with acute myocardial infarction.262’263 In approximately 35% of cases in which thrombolytic therapy reestablishes the coronary flow, there is presence of residual stenosis of more than 50% diam- eter in the infarct-related artery.264 Accordingly, FICA used as a di- rect or primary mechanical means rather than chemical means of es- tablishing the coronary artery patency may be preferable. In patients treated with thrombolytic therapy for acute myocardial infarction, PICA can be potentially applied in four settings. It can be used as a rescue or salvage procedure in patients in whom thrombolytics fail to remove the occlusive thrombus, as a routine immediately in all patients, as a routine deferred in all patients, or as an elective proce- dure only in patients with spontaneous or inducible ischemia.
b S.R. BAILEY: Only 20% of patients who initially have myocardial infarction ac- tually receive thrombolytic therapy. The remaining patients include 15% who are “ideal” candidates, 15% who are elderly, 15% who have one or more contraindi- cations for lytic therapy, and 35% who arrive 6 hours after the myocardial in- farction but have continued chest pain (Muller D, et al. Ann Intern Med 1990;113:949-60). This very large group of patients could all potentially benefit from catheterization and direct angioplasty. The latter is also a strategy that might enable us to discharge patients frum the hospital at a much earlier time.
Direct or primary angioplasty has now been demonstrated in re- cent randomized controlled trials to be equivalent to thrombolytic therapy in terms of amount of myocardium salvaged and short-term mortality.&1’122’123 In the recently published Primary Angioplasty in Myocardial Infarction trial in which 395 patients were treated within 12 hours of the onset of myocardial infarction with tissue plasmino- gen activator or primary angioplasty, the success rate of PTCA was 97% .122 Primary angioplasty and thrombolytic therapy resulted in similar ejection fraction at 6 weeks. These findings are supported by a study from the Mayo Clinic in which patients treated with primary angioplasty and thrombolytic therapy had a similar amount of myo- cardium salvaged as assessed by technetium-99m sestamibi.84 In the Primary Angioplasty in Myocardial Infarction trial, primary RCA was
Curr Probl Cardiol, May 1994 261
also associated with a reduction in in-hospital and 6-month mortal- ity, as well as reinfarction rates. Most importantly, intracranial hem- orrhage occurred in 2% of patients treated with tissue plasminogen activator as compared with no event noted in patients treated with primary FTCA. The advantages of direct or primary RCA are as fol- lows: (11 higher earlier patency rates (approximately 90% versus 70% to 80% achievable by presently available thrombolytic therapy); (21 si- multaneous mechanical dilation of the occlusive thrombus and the underlying stenotic lesions, thus avoiding the need for subsequent risk stratification and elective PTCA; (3) identification of high-risk groups (approximately 35% of patients presenting with myocardial infarction may have either significant multivessel disease or left main coronary artery disease with a patent infarct-related vesse1.264 Early angiography in primary FWZA leads to earlier identification of these high-risk patient groups); (41 reduced hospital stay and costs because invasive testing for identification of ischemia, coronary angiography, or elective PTCA is not needed; if the status remains uncomplicated after primary PICA, patients can be discharged earlier than after un- complicated thrombolytic therapy; and (5) the avoidance of the risk of intracranial hemorrhage, as seen in 0.6% to 1.0% of patients re- ceiving thrombolytic therapy. The limitations of primary RCA in- clude the following: (1) it can only be applied in a minority of pa- tients because of a limited number of hospitals with a committed 24- hour catheterization laboratory and emergency surgical team capable of performing primary PICA and (2) primary IITCA potentially may be more expensive.
b S.R. BAILEY: Direct FICA is more likely to achieve TIMI grade 3 flow than in- travenous thrombolWytic agents. The recent GUSTO trial highlighted the impor- tance of TIMI grade 3 flow, with a 20% decrease in mortality for those patients who achieved this flow rate. Sadly, only 36% of patients were this fortunate, whereas more than 95% of patients undergoing FICA will achieve TIMI grade 3 flow. Although this has been associated with a low mortality, studies to date have not shown any significant difference in myocardial function between these pa- tients.
b S.R. BAILEY: Recent survevs have ‘indicated that 92% of all facilities with a cath- kerization laboratory have the capacity for emergency angioplasty. Seventy-five percent of all myocardial infarctions occur in urban areas and 85% of patients are less than 60 minutes by automobile from a center capable of performing emergency FICA. These findings contradict the conventional wisdom that di- rect FICA is not a viable treatment strategy. Given the large percentage of pa- tients with contraindications or late presentation, direct FICA should play a much greater role in clinical practice than.it now does.
Although the success rate of primary FlCA is approximately 90%) the procedure is not without risk. Complication rates for problems such as abrupt vessel closure, cardiogenic shock, need for emergency
262 Cum Probl Cardiol, May 1994
bypass surgery, and deaths are higher if there is thrombolysis in myo- cardial infarction grade 0 or 1 flow in the infarct-related artery as com- pared with a thrombolysis in myocardial infarction grade 2 or 3 base- line flo~.‘~~ Bradycardia and hypotension are also more common with recanalization of total occlusion in the right coronary artery, possibly because of a Bezold-Jarisch reflex.2658266 Approximately 3% to 5% of patients undergoing primary PlCA need emergency bypass surgery because of failed angioplasty or recurrent thrombotic occlu- sions.2”7,268 This rate is similar to patients undergoing elective PTCA for spontaneous or inducible ischemia after successful thrombolysis.
Primary PICA should be strongly considered in four patient sub- groups. The first subgroup consists of patients who arrive early at a hospital that has cardiac catheterization and surgical facilities avail- able without delay. The advantages of primary angioplasty may be particularly high in patients with anterior myocardial infarction.“’ The hospitalized patient who has an acute myocardial infarction while the catheterization laboratory is operational is best treated by direct PTCA.‘“” The second subgroup consists of patients in whom the diagnosis of acute myocardial infarction is uncertain because of baseline electrocardiographic abnormalities such as previous myo- cardial infarction, left bundle branch block, or left ventricular hy- pertrophy. The third subgroup consists of patients with absolute con- traindications to thrombolytic therapy, such as patients with a his- tory of recent stroke, surgery, or trauma; patients with severe uncon- trolled hypertension; or patients who receive prolonged cardiopul- monary resuscitation. The fourth subgroup consists of patients with cardiogenic shock. Historical data suggest that the mortality rate of patients with cardiogenic shock is high (80% to 85% ).27” Data from the Gruppo Italian0 per lo Studio della Streptochinasi nellmfarcto Miocardio trial, which used intravenous streptokinase in patients with cardiogenic shock, did not show any significant reduction in mortality rates.27’ The earlier data from the intracoronary streptoki- nase registry had shown that in patients with cardiogenic shock the mortality rate is significantly reduced with successful thrombolysis as compared with failed thrombolysis (42% versus 84% mortality rate, r~espectively).27” This apparent discrepancy in results might be attrib- uted to route of drug administration, namely, intravenous versus in- tracoronary, or mechanical reperfusion with a guide wire that was used in many patients reported in the intracoronary streptokinase registry. The benefit of mechanical reperfusion in patients with car- diogenic shock was also demonstrated by Lee et a1.,273 who reported a reduction in the mortality rate to 17% with successful adjunct PICA, a decrease from the mortality rate of 75% in patients with failed reper- fusion with intravenous thrombolytic therapy. This immediate reduc- tion in the hospital mortality rate was also translated into long-term survival rates, with fewer occurrences of congestive heart failure and
Curr Probl Cardiol, May 1994 263
arrhythmia over a 2- to 4.5-year follow-up period.Z74 Thus infor- mation available from uncontrolled series of patients with cardio- genie shock would suggest that earlier mechanical reperfusion with direct PICA is a reasonable therapy in patients with cardiogenic shock.
As mentioned earlier, intravenous thrombolytic therapy results in successful reperfusion in 70% to 80% of patients early after throm- bolysis. In approximately 35% of patients, an underlying significant stenosis in the infarct-related artery remains that may contribute to recurrent ischemia, reinfarction, and reocc1usion.z75S276 Additional mechanical dilation of these lesions with balloon angioplasty to pro- vide more complete reperfusion and prevent recurrent ischemia and reocclusion was proposed as the reason to perform routine immedi- ate angioplasty. RCA in patients after successful thrombolysis can be divided into routine immediate or deferred empiric angioplasty and late elective angioplasty. Immediate PTCA is performed as soon as possible (within 1 to 2 hours after the administration of thrombo- lytic therapy) after successful thrombolysis. FTCA performed rou- tinely 18 hours to 7 days after successful thrombolysis is considered deferred empiric angioplasty. FI’CA performed after successful reper- fusion only in patients with demonstrable spontaneous or inducible ischemia by noninvasive testing is considered elective FICA. Three large-scale randomized controlled trials, namely, the Thrombolysis and Angioplasty in Myocardial Infarction trial, the European Coop- erative Study Group trial, and the Thrombolysis in Myocardial Infarc- tion trials, have addressed the issue of immediate PTCA versus de- layed FTCA (empiric or elective) or no PI’CA.31~277~278 All the trials showed no significant improvement in global left ventricular ejection fraction or late recovery of ejection fraction in patients undergoing immediate PTCA compared with patients who underwent delayed PICA, elective PICA, or no PTCA. In addition, both the Thrombolysis and Angioplasty in Myocardial Infarction phase 1 and the Thromboly- sis in Myocardial Infarction phase 2A trials showed a trend toward increased mortality rates, whereas the European Cooperative Study Group trial showed a statistically significant increase in the mortality rate of patients who underwent immediate FTCA as opposed to de- layed PTCA. Although the overall rate of referral to bypass surgery was similar in patients in the immediate and delayed angioplasty groups, the rate of emergency bypass surgery was significantly higher in patients undergoing immediate angioplasty. The reocclusion rate after successful thrombolysis has been reported to be 10% to 20%. The use of immediate or delayed PICA with successful thrombolysis did not appear to alter the reocclusion rate (11% to 12.5% with im- mediate and 11% to 14% with delayed FVCA). The advantages of de- layed angioplasty compared with immediate angioplasty may relate
264 Cum Probl Cardiol, May 1994
to late thrombolysis. The incidence of spontaneous thrombolysis is approximately 15% at 7 days after myocardial infarction.277 In addi- tion, angioplasty of a more stabilized plaque at the site of thrombo- sis could result in a decreased incidence of referral to emergency by- pass surgery in patients undergoing delayed RCA. In view of the lack of any demonstrable benefit and because of the significantly in- creased risk of complications and death, routine immediate PICA is contraindicated in patients who do not have symptoms after throm- bolytic therapy. Although no controlled trials of immediate RCA in patients with cardiogenic shock treated with thrombolytic therapy have been conducted, as discussed earlier uncontrolled series of pa- tients with cardiogenic shock have shown adjunct RCA to improve the in-hospital and long-term survival rates significantly as compared with patients treated with no thrombolysis or unsuccessful thrombolysis.272-274 Therefore immediate PICA is presently indicated only in patients with cardiogenic shock.
Deferred PICA may be subdivided into empiric PICA and elective PICA. The invasive strategy of routine cardiac catheterization and an- gioplasty after 18 hours to 7 days was compared with elective con- servative use of angioplasty only in patients with demonstrable spon- taneous or inducible ischemia in two large randomized trials: the Thrombolysis in Myocardial Infarction phase 2B trial and the Should We Intervene Following Thrombolysis trial.32,27s The primary end points in both studies, mortality and reinfarction rates, were similar at 6 weeks and 12 weeks in both conservative and invasive strategies. The resting left ventricular ejection fraction at hospital discharge and at the end of the study period was also found to be similar in both groups. The rate f o referral for emergency bypass surgery was 3% to 5%. By the nature of the study design, recurrent ischemia was more common in the conservative group who did not undergo routine an- gioplasty than in the invasive group, although without any increased risk of complications. Although it appears that routine delayed an- gioplasty is associated with a similar risk of complications as com- pared with elective PICA, it offers no advantage in terms of survival or risk of recurrent infarction and may be more expensive, as sug- gested by the cost analysis in Thrombolysis in Myocardial Infarction phase 2B trial. However, the cost analysis benefit for conservative strategy did not include the cost of close follow-up, recurrent hospi- talization for ischemia, and subsequent coronary angiography and angioplasty for the treatment of recurrent ischemia and infarction. Therefore, at present, RCA after successful thrombolysis in uncom- plicated acute myocardial infarction should be reserved for patients with postinfarction angina, severe left ventricular dysfunction, and significant myocardial ischemia detected by noninvasive testing be- fore hospital discharge. A subgroup analysis from the Thrombolysis
Curr Probl Cardiol, May 1994 266
in Myocardial Infarction phase 2B trial may suggest a beneficial ef- fect of routine deferred angiography and angioplasty in patients with prior myocardial infarction?”
Of patients treated with thrombolytic therapy for acute myocardial infarction, 20% to 30% fail to recanalize the occluded artery. This group of patients has a significantly poorer prognosis.z81 The imme- diate use of angioplasty to salvage myocardium in these circum- stances is referred to as rescue angioplasty.z81~283 The identification of patients who do not sustain successful reperfusion by clinical and electrocardiographic criteria is poor, with only moderate sensitivity and poor specificity.284 In the Thrombolysis and Angioplasty in Myo- cardial Infarction phase 1 study,Z85 improvement in the initial chest pain symptoms predicted patency of the infarct-related artery in ap- proximately 70% of patients, whereas complete resolution predicted infarct artery patency in approximately 80% of patients. However, in patients with angiographic reperfusion, improvement in chest pain occurred in approximately 50% of patients, and complete resolution of chest pain occurred in approximately 30% of patients. Similarly, improvements in initial ST segment elevation predicted infarct artery patency in 84% of patients, and complete resolution of ST segment elevation predicted patency of the infarct-related artery in 96% of the patients. However, the specificity of these criteria is also low in pa- tients with an angiographic patent infarct-related artery where im- provement in ST segment elevation or complete resolution of ST seg- ment was observed in only 38% and 6% of patients, respectively.
Coronary angiography appears to be the only reliable means of identifying failed reperfusion. However, coronary angiography is not routinely performed now in patients receiving thrombolytic therapy for acute myocardial infarction. Future development of noninvasive tests, such as analysis of creatine kinase isoenzymes containing M and B subunits or on-line monitoring of ST segment changes, may allow for rapid early detection of failed reperfusion and for the de- termination of whether angiography and rescue angioplasty are needed. The limited available data at present suggest that the proce- dural success rate of rescue angioplasty is lower than direct angio- plasty or elective angioplasty (70% to 80% versus 90%0), and reocclu- sion rates and mortality rates are higher than in patients undergoing direct or primary angioplasty.281~z83’286’287 However, recently pub- lished results from the Randomized Evaluation of Salvage Angioplasty with Combined Utilization of Endpoints trial reported a procedural success rate of 95% ?’ In that study 150 patients with acute anterior myocardial infarction who were treated with thrombolytic therapy and found to have persistent occlusion with a Thrombolysis in Myo- cardial Infarction grade 0 or 1 flow within 1.5 to 8 hours of the onset of chest pain were randomized to either no angioplasty or rescue an- gioplasty. No difference was observed in the resting ejection fraction
266 Curr Probl Cardiol, May 16%
at 30 days, the primary end point of the study. However, the com- bined end point of the mortality rate and congestive heart failure with class 3 or 4 symptoms were significantly reduced in patients who un- derwent rescue angioplasty.
b P.M. SHAH: The authors, who have considerable experience in this field, have provided an up-to-date review of the current status of angioplasty. I cannot help but feel that angioplasty may ultimately be relegated to a passing phase of thera- peutic adventure unless we can (1) understand the precise mechanism of suc- cussful dilatation, (2) control the level of injury or dissection needed for a suc- cessful outcome, (3) understand the precise mechanisms of restenosis, and (4) develop strategies to prevent restenosis. Unless these goals are realized, angio- plasty may well be demoted to a procedure of second choice and may ultimately become little more than a footnote in history.
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