Prevalence of right ventricular perfusion defects after inferior myocardial infarction assessed by low-level exercise with technetium 99m sestamibi tomographic myocardial imaging

To assess the prevalence of right ventricular perfusion defects after a recent inferior wall myocardial infarction, 33 patients were studied 6 to 14 days after infarction with low-level exercise testing and technetium 99m ( eemTc) sestamibi (SPECT) imaging. Twenty-two control subjects with a <5% likelihood of coronary artery disease undergoing exercise 99mT~ sestamibi imaging were also studied. For each image the right ventricle was computer isolated from reconstructed transverse cardiac slices, followed by reorientation into oblique slices. Both right and left ventricular images were visually assessed for defects. A quantitative method of defect detection was also applied to the right ventricle. For the right ventricle, 100% of the stress images and 96% of the rest images were adequate for interpretation. Right ventricular stress perfusion defects were identified in 10 (30%) of 33 patients with recent inferior infarction, with 50% completely or partially normalizing on rest images, consistent with ischemia. Of 14 patients with left ventricular inferoseptal defects, eight (57%) had right ventricular defects compared with 2 (11%) of 19 without inferoseptal defects (p < 0.005). We concluded that the right ventricle can be adequately assessed for perfusion defects by means of exercise with 99mT~ sestamibi SPECT imaging. Defects of the right ventricle after inferior myocardial infarction occur frequently, and many have evidence of ischemia. Right ventricular perfusion defects are closely associated with left ventricular inferoseptal defects. (AM HEART J 1994;127:797-604.)

Mark I. Travin, MD, Robert D. Malkin, MD, Carol Ewing Garber, PhD, Debra E. Messinger, CNMT, Donna J. Cloutier, BS, and Gary V. Heller, MD, PhD Pawtucket and Providence, R. I.

In patients with an inferior wall myocardial infarc- tion, the right ventricle is involved in 30 % to 55 % of cases. l-5 Right ventricular involvement has been as- sociated with an increase in acute and chronic mor- bidity. 6 7 Thus identification of right ventricular perfusion abnormalities in patients with myocardial in- farction is important and could alter both the immed- iate and long-term management of these patients8

Because the right ventricle is anatomically com- plex and relatively small compared with the left ven-

From the Nuclear Cardiology Laboratory, Division of Cardiology, Memorial Hospital of Rhode Island; the Division of Cardiology, Roger Williams Gen- eral Hospital, and Brown University School of Medicine.

Received for publication April 5, 1993; accepted Aug. 6, 1993.

Reprint requests: Mark I. Travin, MD, Division of Cardiology, Roger Williams Medical Center, 825 Chalkstone Ave., Providence, RI 02908.

Copyright @ 1994 by Mosby-Yem Book, Inc.

0002.8703/94/$3.00 + 0 4/l/52146

tricle, imaging of this chamber with thallium-201 has been difficult. DePuey et a1.g found that myocardial imaging with technetium 99m (ggmTc) sestamibi was superior to thallium-201 for identifying right ven- tricular perfusion defects in both stress and rest sin- gle photon emission computed tomographic (SPECT) images. The purpose of this study was to further as- sess the ability of ggmT~ sestamibi to evaluate right ventricular perfusion and to determine the preva- lence of right ventricular perfusion defects during low-level exercise testing after recent inferior myo- cardial infarction.

METHODS Study design and patient selection. All patients who

had a recent inferior myocardial infarction at either Me- morial Hospital of Rhode Island or Roger Williams Med- ical Center were screened for participation in the study. Entry criteria included all of the following: ECG evidence

797

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of acute inferior myocardial infarction, creatine kinase peak in excess of 1.5 times the normal value with an MB fraction 16%) the ability to undergo low-level exercise testing, and absence of chest pain 48 hours before testing. Patients with unstable angina, Killip class III or IV congestive heart failure, and those who had a previous re- vascularization procedure (transluminal coronary artery angioplasty or coronary artery bypass surgery) were ex- cluded. Patients who qualified underwent low-level exer- cise testing with ggmT~ sestamibi SPECT myocardial imaging 6 to 14 days after infarction and constituted group A. Exercise testing consisted of a same-day rest-stress pro- tocol with ggmTc sestamibi imaging and a modified Bruce protocol in which patients exercised to a maximum of stage II (12 minutes) or until 70 % of the maximal predicted heart rate was achieved.

The image results of the study patients were compared with findings in a control group (group B) of 22 patients undergoing symptom-limited exercise ggmT~ sestamibi SPECT imaging who, according to clinical and EGG crite- ria, had a <5% likelihood of coronary artery disease.‘O In group B 45 % of the patients were men, with a mean age of 51.6 ? 15.0 years. All had normal left ventricular perfusion images on visual analysis by two experienced nuclear car- diologists.

Exercise and imaging protocols. Patients in group A underwent l-day rest and stress ggmT~ sestamibi SPECT myocardial imaging 6 to 14 days after myocardial infarc- tion. Approximately 7.8 mCi (per 70 kg) of ggmTc sestamibi was injected at rest after a 4-hour fast with imaging performed 1 hour later. Exercise testing with a modified Bruce protocol was conducted 3 to 4 hours after the rest injection with 22 mCi (per 70 kg) of ggmT~ sestamibi injected at peak exercise, 1 minute before termination. Ex- ercise was stopped for any of the following reasons: occur- rence of progressive angina, achievement of 70% of the maximal predicted heart rate, ECG changes of 20.2 mV of horizontal or downsloping ST-segment depression, fatigue, or completion of stage II of the protocol (12 minutes of ex- ercise). Imaging was begun 30 to 60 minutes after the stress injection.

Patients in group B completed exercise with either a l-day rest-stress or a 2-day protocol. For the 2-day studies, 15 to 22 mCi of ggmT~ sestamibi was injected at rest and imaging was performed 60 to 90 minutes later. On a sepa- rate day patients underwent exercise testing with a stan- dard Bruce protocol, with 15 to 22 mCi of ggmT~ sestamibi injected 1 minute before peak exercise. Image acquisition was begun 30 to 60 minutes after exercise.

SPECT myocardial imaging procedure. A rotating, large field-of-view gamma camera (ADAC ARC-4000, ADAC Laboratories, Milpitas, Calif.) equipped with 61 photomultiplier tubes, a 0.25-inch thick sodium iodide crystal, and a high-resolution, parallel-hole collimator was used for all studies, with tomographic acquisition and pro- cessing. Images were acquired in a 180-degree arc consist- ing of 64 views. For each view, data were acquired for 25 seconds at rest and for 20 seconds with stress, beginning at

the 45-degree right anterior oblique position. Each image was corrected for nonuniformity with a 30-million count image performed weekly with ggmT~ as the flood source. The mechanical center of rotation was determined weekly from the projection data and allowed for proper alignment of detector data with respect to the reconstruction matrix.

All images were reconstructed with filtered backprojec- tion resulting in transverse cardiac slices. A Butterworth filter with a 0.5 cycles/cm cutoff frequency and order of 10 was used for all images except exercise stress images from patients in group A, for which a Butterworth filter with a 0.66 cycles/cm cutoff frequency and order of 7 was used to account for residual photon activity from previous same- day rest images. All transverse images were then reoriented into standard short-axis, vertical long-axis, and horizontal long-axis slices, each 6 mm thick.

Right ventricular image processing. For all transverse cardiac images, a region of interest was drawn around the right ventricle from the slice in which the right ventricle was best seen by means of a method similar to that described by DePuey et a1.9 This permitted good visualiza- tion of the right ventricle by excluding the photon-dense left ventricle. The resulting isolated right ventricular transverse images were reoriented into short-axis, vertical long-axis, and horizontal long-axis slices, each 6 mm thick.

Visual analysis of the right and left ventricles. All right and left ventricular images from both groups were read vi- sually without knowledge of clinical data or identity of the patients. Isolated right ventricular images were assessed by dividing two short-axis slices at separate ventricular levels, mid short axis and basal short axis, into three equal segments: anterior, lateral, and inferior (Fig. 1). Each right ventricular segment was scored, based on its photon activ- ity, from 0 to 4 as follows: 0 = normal; 1 = mild reduction; 2 = moderate reduction; 3 = severe reduction; 4 = absent activity. A score of two or higher was considered abnormal. and differences of opinion were resolved by consensus.

Visual analysis of the left ventricle was performed by di- viding three short-axis slices at separate ventricular levels (apical, mid, and basal) into six segments: anterior, an- teroseptal, inferoseptal, inferior, inferolateral, and high lateral. The apex was assessed from the long-axis view at the midventricular level and was divided into anterior and inferior segments (Fig. 1). The photon activity for each left ventricular segment was scored from 0 to 4, as described for the right ventricle, with a score of ~2 considered abnormal.

Quantitativeanalysisof therightventricle.Quantitative analysis of the right ventricle was also performed as described elsewhere.” Based on a technique described by DePuey et a1.,9 all but the right ventricle was computer masked, leaving a visually enhanced right ventricular transverse image. Reorientation of this right ventricular image was performed to obtain oblique right ventricular slices. Similar to what was done for the left ventricle, a semicircular polar coordinate map of the right ventricle was constructed. Five circumferential count profile curves were derived from concentric stress semicircular short-axis right ventricular slices. Each curve was normalized to the high-

Volume 127, Number 4, Part 1 American Heari Journd Travin et al. 799

RtGHTVENTRKXlAR SEGMENTS

1

2 6

@

3 5 4

APICAL SHoflT AXIS

1

t

2

3

MID wof4T AXIS BASAL SHORT AXIS

LEFT VENlMCUlAR SEGMENTS

7

6 12

@

9 11

10

MID SHORT AXIS BASAL SHORT AXIS VERTICAL LONG AXIS

Fig. 1. Visual scoring system used for analysis of right (top) and left (bottom) ventricles. For right ven- tricle, apex was eliminated leaving six segments to be scored (using 0 to 3 system). Left ventricular scoring system consisted of 20 segments (1 to 20), each scored 0 to 3 in severity.

est pixel count for that particular curve. Values were obtained for 10 equidistant points on each curve, yielding 50 points. Each point was assigned a normal value based on mean values from the 22 control patients in group B. A right ventricular quantitative defect for patients in group A was defined as 15 contiguous points with values >2.5 standard deviations below the mean. Determination of both the presence of a right ventricular defect, as well as its poten- tial normalization at rest, was made from combined visual and quantitative analysis. For 31 of the 33 patients in group A, the presence or absence of a right ventricular perfusion defect by visual analysis was supported by the quantitative method. In two cases of a discrepancy between visual and quantitative results, the final decisions was made by con- sensus.

Table I. Clinical characteristics in 33 patients with inferior myocardial infarction

Clinical characteristics Age (yr) Sex (male/female) Peak creatine kinase (I Units/L Q-wave infarction Thrombolytic therapy Previous myocardial infarction

61 + 12

20 (61%)/13 (40%) 1,605 + 1,346

26 (79%) 16 (48%)

3 (9%)

Statistical analysis. Comparisons of the demographic data between patients with and without right ventricular infarction were made with an independent-samples Stu- dent’s t test for ratio-scale data and a Mann-Whitney U test for ordinal scale data.12 Comparisons of the imaging data relative to adequacy and defects were made with the Mann-Whitney U test. Statistical significance was set at p 5 0.05.

RESULTS

with ggmT~ sestamibi imaging 6 to 14 days after infe- rior myocardial infarction, are outlined in Table I. The ability to adequately visualize and interpret the right ventricular images of these patients, as well as those of the control group (group B), is shown in Ta- ble II. All 55 stress images and 53 of 55 rest images (stress images were normal for the other two) were judged adequate for interpretation. Thus stress im- aging with ggmT~ sestamibi provided satisfactory as- sessment of 98% (108/110) of the right ventricular images, allowing consistent assessment of right ven- tricular perfusion in these patients.

The clinical characteristics of the 33 patients in Of the 33 patients with recent inferior infarction, group A, who underwent low-level exercise testing 10 (30 % ) were found to have right ventricular perfu-

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Table II. Image adequacy for right ventricular interpreta- tion during visual analysis

Patient image n Adequate

Study (group A) Stress Rest

Control (group B) Stress Rest

33 33 (100%)

33 32 (97%)

22 22 (100%)

22 21 (95%)

Table IV. Relationship between left and right ventricular defects in patients with recent inferior myocardial infarction

n Right ventricular

defect n (PO)

Inferoseptal defect Present 14 8 (57)* Absent 19 2 (11)

n, Number of patients with percentage of total in parenthesis. *p < 0.005 when compared with defects absent.

Table Ill. Clinical characteristics of patients with right ventricular myocardial perfusion defects assessed with ggmT~ sestamibi imaging

ventricular defect had a right ventricular defect (p < 0.005). All patients with a right ventricular de- fect also had a left ventricular abnormality.

Right ventricular perfusion defect

Present Absent (n = 10; 30%) (n = 23; 70%) p Value

infarction CK-MB

Age (yd

13.8 k 3

62 + 15

12.3 r 6.4

61 +- 10

NS

NS Peak CK (W/L) 1,276 t 1,114 1,748 f 1,434 NS Q-wave infarction 9 (90%) 17 (74%) NS Thrombolytic therapy 5 (31%) 11 (69%) NS

Prior myocardial 0 3 (13%) NS

Examnles of right ventricular images areshown in

”

Figs. 2 and 3. In Fig. 2 the images ari from a patient

”

in group B (control) with a <5% possibility of coro- narv arterv disease. Both the right and left ventricles are illustrated after rest and stress. All images were considered normal. A second patient is shown in Fig. 3. This patient underwent low-level exercise testing 11 days after inferior myocardial infarction. The

Clinical characteristics

CK, Creatine kinase; MB, myocardial isoenzyme; NS, not significant.

sion defects (Table III). All defects involved at least the inferior segment of the right ventricle, and none extended to the anterior segment. No significant dif- ferences between patients who had right ventricular defects and those who did not were found with respect to age, peak creatine kinase value, incidence of Q-wave infarctions, use of thrombolytic therapy, prior myocardial infarction, or incidence of hypoten- sion with clear lungs on hospital presentation. Among the 10 patients with stress perfusion defects of the right ventricle, five (50%) had either complete or partial normalization of defects on rest images, sug- gesting ischemia. The presence of either angina or ECG changes during exercise testing in the patients with fixed versus ischemic right ventricular defects was similar.

The characteristics of the left ventricular perfusion defects after inferior myocardial infarction were ex- amined. Left ventricular perfusion defects were found in 28 (89 % ) of 33 patients. The defects were divided into the following three categories: 14 were infer- oseptal defects, eight were primarily inferior defects, and six were inferolateral defects. As shown in Table IV, 57 % of patients with an inferoseptal left ventric- ular defect also had a right ventricular defect, whereas only 11% of patients without an inferoseptal left

right ventricular stress images demonstrated a marked reduction in photon activity in the inferior wall of the right ventricle, with partial normalization at rest. The left ventricular images revealed a par- tially normalizing inferoseptal defect.

DISCUSSION

This study evaluated the ability of low-level exer- cise with ggmT~ sestamibi SPECT myocardial perfu- sion imaging to detect right ventricular perfusion defects in patients after a recent inferior myocardial infarction. Both stress and rest right ventricular im- ages could be adequately interpreted 98% of the time. Right ventricular perfusion defects were found in 30% of the stress studies in patients with inferior myocardial infarction, with 50% having evidence of ischemia. Right ventricular defects were associated with inferoseptal defects of the left ventricle.

Visualization of the right ventricle. Heretofore, poor visualization of the right ventricle with thallium-201 imaging has limited the routine assessment of right ventricular perfusion defects.13-I6 In two studies by Brown et a1.,14, l5 the right ventricle was not visual- ized in 18 % and 11% , respectively, of the images ob- tained. Wackers et al. l3 described difficulties in obtaining right ventricular images at rest with thal- lium-201.13 In contrast, DePuey et al9 directly com- pared results of thallium-201 and ggmT~ sestamibi SPECT imaging in the same patients and found the latter to result in better visualization of both rest and stress images, allowing consistent identification of

Volume 127, Number 4, Part 1 American Heart Journal Travin et al. 801

Fig. 2. Right and left ventricular images after exercise stress and rest in a normal subject (group B). Right ventricular image displayed is after masking of left ventricle for image enhancement.

defects and ischemia. The present study extends the right ventricular defects (43%). The present study, work of DePuey et a1.g in that a very high percentage confined to patients with recent inferior myocardial of rest images, as well as all stress studies, were well infarction, found a similar (50%) prevalence of visualized and allowed detection of right ventricular ischemia in patients with right ventricular perfusion ischemia. defects.

Prevalence of right ventricular perfusion defects in patients with inferior myocardial infarction. Previous reports in which other methods such as autopsy, gated blood pool imaging, and ggmT~ pyrophosphate imaging were used have shown a 25 % to 37 % prev- alence of right ventricular abnormalities after infe- rior myocardial infarction.16-lg Findings in the present study are consistent with those of previous studies in that 30 % of patients had right ventricular perfusion defects.

Identification of &hernia. Because of the limitations previously discussed, reports of right ventricular is- chemia are rare. Brown et a1.,15 with the use of pla- nar thallium-201 imaging, observed that 44% of nonselected patients with right ventricular defects had evidence of ischemia.15 DePuey et a1.,g by means of exercise with ggmT~ sestamibi SPECT imaging, described ischemia in three of seven patients with

Association of right ventricular defects with infer- oseptal defects of the left ventricle. Results of the present study suggest that right ventricular perfu- sion defects are closely associated with defects of the inferior left ventricular septum. This is consistent with autopsy results and previous thallium-201 im- aging studies.l* 161 20* 21 The right ventricle is predom- inantly supplied by branches of the right coronary artery, which in 77 % to 90 % of patients also perfuses the inferior portion of the septum via the posterior descending artery. It follows that in patients with right dominant circulation, a stenosis of the proximal right coronary artery would often impair perfusion of both the right ventricle and the inferior septum.

Clinical utility of right ventricular perfusion imaging after myocardial infarction. The presence of right ven- tricular involvement from acute myocardial infarc- tion has been previously associated with postinfarc-

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American Heart Journal

Fig. 3. Images after low-level exercise stress and rest performed 11 days after inferior myocardial infarc- tion. Right ventricular images are illustrated after masking of left ventricle. Right ventricular image dem- onstrates perfusion defect in inferior portion, with partial improvement at rest. Left ventricular image, dis- played on right panels, demonstrates inferoseptal defect, also with partial improvement at rest.

tion angina, heart block, ventricular arrhythmias, systemic hypotension and, in the subset of patients with left ventricular dysfunction, a threefold increase in l-year mortality. 3-6 Although bedside techniques or invasive procedures may be helpful in the detec- tion of right ventricular involvement, a simple non- invasive technique for doing so would be of benefit. Myocardial perfusion imaging with technetium com- pounds has been shown in this study to permit clear, consistent visualization of the right ventricle 6 to 14 days after the acute event, allowing reliable detection of infarction and ischemia. Perfusion imaging with pharmacologic stress-inducing agents such as dipy- ridamole may permit even earlier (24 to 96 hours af- ter presentation) assessment of right ventricular is- chemialinfarction, similar to what has been shown for the left ventricle.22

The current study did not find the presence alone of a right ventricular sestamibi defect to be associ- ated with clinical evidence of right ventricular in- farction. Indeed results of studies by Wackers et al.lg

in which ggmT~ pyrophosphate imaging of the right ventricle was performed, have suggested that the ex- tent of right ventricular damage may determine the presence or absence of typical clinical symptoms.

Although the major determinant of prognosis after myocardial infarction is the extent of left ventricular disease, several studies suggest that in patients with severe left ventricular dysfunction, added right ven- tricular involvement worsens the prognosis. Dell’Italia et a1.23 found that patients with right ven- tricular infarction and severe left ventricular dys- function or ischemia were at higher risk for death. Shah et a1.6 found that for postinfarction patients with a left ventricular ejection fraction of less than 38%) the additional presence of right ventricular in- volvement increased the l-year mortality rate from 25 % to 75 % .‘j Nevertheless, a large comprehensive study examining the prognostic implications of postinfarction right ventricular ischemia and infarc- tion, as determined by radionuclide myocardial per- fusion imaging, has yet to be undertaken.

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Study limitations. The present study was limited to patients with inferior myocardial infarction. As such the prevalence of right ventricular defects in other types of infarction was not assessed. In addition, the relationship of the right ventricle to surrounding structures may be a technically limiting feature in the accurate assessment of defects. For example, the apex of the right ventricle was found to be difficult to evaluate because of overlap from the photon-dense left ventricle and was not included in the quantitative analysis. Similarly, overlap of counts from the liver may interfere with assessment of the inferior right ventricular wall. Finally, because of recent infarction, the exercise protocol used in this study was submax- imal. Although this form of exercise has been shown by Gibson et a1.24 and others25-27 to be predictive of future cardiac events, it may have underestimated the true percentage of patients with right ventricular ischemia.

Conclusions. Right ventricular perfusion defects may be adequately assessed by means of ggmT~ ses- tamibi SPECT myocardial perfusion imaging. After inferior myocardial infarction right ventricular de- fects are present in approximately one third of patients, with half of the defects showing evidence of ischemia. In this population right ventricular perfu- sion defects were closely associated with perfusion defects involving the inferoseptal wall of the left ventricle.

We thank Karen Poissant for her assistance in the preparation of the manuscript and Lynn Sillaman, CNMT, and Tina Cameron, RN, for technical assistance.

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Olschewski M, Just H. Right ventricular infarction as an in- dependent predictor of prognosis after acute inferior myocar- dial infarction. N Engl J Med 1993;328:981-8. Backes RJ, Gibbons RJ. Utility of technetium-99m sestamibi SPECT imaging in the evaluation of right ventricular involve- ment during an acute myocardial infarction [Abstract]. J Am Co11 Cardiol 1991;32:929. DePuey EG, Jones ME, Garcia EV. Evaluation of right ven- tricular regional perfusion with technetium-99m-sestamibi SPECT. J Nucl Med 1991;32:1199-205. Diamond GA, Forrester JS. Analysis of probability as an aid in the clinical diagnosis of coronary artery disease. N Engl J Med 1979;300:1350-8. Travin MI, Malkin RD, Garber CE, Messinger DE, Cloutier DJ, Heller GV. Quantitative detection of right ventricular perfusion defects in technetium-99m sestamibi SPECT im- ages [Abstract]. J Am Co11 Cardiol 1993;21:249A. Woolson RF. Statistical methods for the analysis of biomed- ical data. New York: John Wiley & Sons, 1987:156-62,366-70. Wackers FJ, Klay JW, Laks H, Schnitzer J, Zaret BL, Geha AS. Pathophysiologic correlates of right ventricular thallium- 201 uptake in the canine model. Circulation 1981;64:1256-64. Brown KA. Boucher CA. Okada RD. Strauss HW. Pohost G. Initial and delayed right ventricular thallium-201 rest imaging following dipyridamole-induced coronary vasodilation: rela- tionship to right coronary artery pathoanatomy. AM HEART J 1982;103:1019-24. Brown KA, Boucher CA, Okada RD, Strauss HW, McKusick KA, Pohost GM. Serial right ventricular thallium-201 imaging after exercise: relation to anatomy of the right coronary artery. Am J Cardiol 1982;50:1217-22. Isner JM. Right ventricular myocardial infarction. JAMA 1988;259:712-8. Shah PK, Maddahi J, Berman DS, Pichler M, Swan HJC. Scintigraphically detected predominant right ventricular dys- function in acute myocardial infarction: clinical and hemody- namic correlates and implications for therapy and prognosis. J Am Co11 Cardiol 1985;6:1264-72. Kotler J, Trobaugh GB, Williams DL, Gustafson DE, Tutt RC. Demonstration of a right ventricular infarction with tomo- graphic thallium myocardial imaging. J Nucl Med 1982; 23:1111-3. Wackers FJ, Lie KI, Sokole EB, Res J, Van der Schoot JB, Durrer D. Prevalence of right ventricular involvement in infe- rior wall infarction assessed with myocardial imaging with thallium-201 and technetium-99m pyrophosphate. Am J Car- diol 1978;42:358-62. Gutman J, Brachman M, Rozanski A, Maddahi J, Waxman A, Berman DS. Enhanced detection of proximal right coronary artery stenosis with the additional analysis of right ventricu- lar thallium-201 uptake in stress scintigrams. Am J Cardiol 1983;51:1256-60. - Brachman M, Rozanski A, Charuzi Y, Maddahi J, Waxman AD, Berman DS. Thallium-201 stress redistribution abnor- malities of the right ventricle: a manifestation of proximal right coronary artery stenosis. AM HEART J 1981;10%288-91. Brown KA. O’Meara J. Chambers CE. Plante DA. Abilitv of dipyridamole-thallium~201 scintigraphy in the prediction of future cardiac events after acute myocardial infarction to pre- dict in-hospital and late recurrent myocardial ischemic events. Am J Cardiol 1990;65:160-7. Dell’Italia LJ, Lembo NJ, Starling MR, Crawford MH, Sim- mons RS. Lasher JC. Blumhardt R. Lancaster J. O’Rourke RA. Hemodynamically important right ventricular’infarction: follow-up evaluation of right ventricular systolic function at rest and during exercise with radionuclide ventriculography and respiratory gas exchange. Circulation 1987;75:996-1003. Gibson RS, Watson DD, Craddock GB, Crampton RS, Kaiser DL, Denny MJ, Beller GA. Prediction of cardiac events after uncomplicated myocardial infarction: a prospective study comparing predischarge exercise thallium-201 scintigraphy and coronary angiography. Circulation 1983;68:321-36.

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Does myocardial perfusion scintigraphy demonstrate clinical usefulness in patients with markedly positive exercise tests? An assessment of the method in a high-risk subset

To evaluate the clinical utility of perfusion scintigraphy in patients with markedly positive exercise ECGs, we studied 94 consecutive patients with markedly positive exercise ECGs; 74 of them were also studied with scintigraphy. Patients undergoing scintigraphy had an intermediate pretest likelihood of coronary disease and were divided into two groups: those with reversible defects involving one complete area or aspects of multiple vascular areas (group 1, 38 patients), and those with normal scintigrams and reversible defects in a limited aspect of one vascular area, isolated fixed defects, or both (group 2, 36 patients). Among all demographic and exercise variables, only a hypotensive or blunted blood pressure response and scintigraphic lung uptake or cavitary dilation, although insensitive, were more frequent in group 1 (all p < 0.05). All 36 patients in group 1 and 14 of 18 in group 2 who underwent coronary angiography had significant coronary lesions; 31 in group 1 but only seven in group 2 had multivessel disease (p < 0.05). Subsequently 32 patients in group 1 had revascularization compared with only two patients in group 2. Only one cardiac event was noted among 34 patients in group 2 who were followed for a mean of 38 months while they were being treated medically. However, four of nine patients in group 1 initially treated medically required late revascularization because of clinical progression of disease, and one patient died (p < 0.05). Compared with patients having scintigraphy, patients not imaged had a higher pretest likelihood of coronary disease, a higher incidence of angina, unstable angina, and induced angina, with a lower exercise time and time to ST depression (p < 0.05). All underwent angiography, and 16 had multivessel disease. Not all patients with markedly positive exercise ECGs were at similarly high coronary risk. Some with high-risk coronary anatomy were identified without the use of scintigraphy. In others, where diagnosis and prognosis were less clear, scintigraphy aided in the diagnosis and accurately identified a low-risk subgroup as did no other parameter. (AM HEART J 1994;127:804-16.)

Rajagopal Krishnan, MD, Jiyuan Lu, MD, Michael W. Dae, MD, and

Elias H. Botvinick, MD San Francisco, Calif.

From the Departments of Medicine, Cardiovascular Division, and Radiol- ogy, Nuclear Medicine Section, and the Cardiovascular Research Institute

Exercise testing has been widely used to detect cor-

of the Universitv of California. onary disease for more than 50 years.l A number of Supported in part by a grant from the Fannie E. Rippel Foundation, An- exercise and ECG parameters have been demon- nandale, N.J.

Received for publication Dec. 21, 1992; accepted Aug. 20, 1993.

Reprint requests: Elias H. Botvinick, MD, University of California, San Francisco, 505 Parnassus Ave., Box 0252, San Francisco, CA 94143.

Copyright z1 1994 by Mosby-Year Book, Inc. 000%8703/94/$3.00+0 4/l/52141

strated to predict the presence of coronary artery disease and to evaluate its related risk.2 A markedly ischemic ST-segment response, with early deep ST- segment depression during exercise, is recognized as an indicator of extensive high-risk coronary disease.3

804