Ischemic heart disease
Sergio Caravita, MD, PhD
Department of Management, Information and Production Engineering, University of Bergamo
Cardiology Unit, IRCCS Istituto Auxologico Italiano San Luca Hospital, Milano
16/03/2020
Myocardial ischemia
The coronary circulation provides oxygen and metabolicsubstrates to maintain cardiac function (and proper cardiacfunction is crucial to sustain peripheral metabolic demands)
Cardiac function rapidly adapts to face changes in peripheral demands, and coronary artery flow should followaccordingly
An imbalance between myocardial metabolic demands and myocardial oxygen supply determines myocardial ischemia, with a consequent reduction in cardiac contractility, vulnerability to arrhythmyas, myocardial infarction and eventually death
Factors affecting myocardial oxygensupply/demand
Cardinal symptom:chest pain
Chest pain, pressure or discomfort
(Atypical presentations in diabetics)
Consequences of myocardial ischemia
Hochman J. Circulation 2003;107:2998
Acute coronary syndromes vs chronic coronary artery disease
Acute coronary syndromes
Medical emergency
Acute onset of symptoms that may do not resolve spontaneously
Acute occlusion or subocclusion of a coronary artery
Need for a rapid diagnosis using easily and widely available tools
- Clinical history (risk factors , onset of symptoms, characteristics of pain…)
- EKG
- Echocardiography
- Cardiac biomarkers (troponins)
- Coronary angiography
Need for prompt intervention, according to clinical presentation and type of ACS
Acute coronary syndromes (ACS)
Three clinical syndromes:
STEMI: ST-elevation myocardial infarction
NSTEMI: non-ST elevation myocardial infarction
UA: unstable angina
Acute coronary syndromes (ACS)
STEMI ST elevation myocardial infarction
STEMI
nearly always caused by coronary plaque rupture resulting thrombosis formation occluding a coronary artery
Generally transmural infarction
Acute phase
Necrosis
The site of ST elevation allows to diagnose the site of myocardial infarction
- ST elevation in lateral leads lateral MI
- ST elevation in anterior leads anterior MI
- …
Left ventricular infero-posterior wallRight ventricle
Left ventricular postero-lateral wall
Left ventricular anterior wall and apex
Echocardiography
Confirms the site of myocardial infarction (hypo- or a-kinetic area corresponding to the territory of a coronary artery)
Echocardiography
Confirms the site of myocardial infarction (hypo- or a-kinetic area corresponding to the territory of a coronary artery)
https://www.youtube.com/watch?v=CM9TmiHpKMA
Verifies the absence of complications (rupture) or of other mimickers (aorticdissection, pulmonary embolism, pericardial effusion…)
Cardiac biomarkers (troponins)
Cardiac-specific biomarkers
If released in the bloodstream in a patient with acute chest pain troponins allows to confirm the diagnosis
Acute chest pain
EKG alterations
(echocardiographic alterations)
(troponins)
STEMI
Coronary angiography
Coronary angiography
Coronary angiography is a procedure that uses catheters, contrast material and x-rays to see how blood flows through the coronary arteries
https://www.youtube.com/watch?v=F2bJFDvDVxg
Coronary angiography in STEMI
https://www.acc.org/education-and-meetings/patient-case-quizzes/a-57yo-caucasian-male-smoker-presents-with-chest-discomfort-and-throat-pressure
Treatment of STEMI
TIME IS MUSCLE !!!!! Need for rapid treatment of the culprit lesion and vessel reperfusion
Medical therapy:
- Antiplatelet drugs (aspirin…)
- Anticoagulant drugs
- Coronary vasodilators (nitrates)
- Management of pain (opioids)
- Oxygen (if O2 desaturation)
Interventional therapy
- Percutaneous coronary intervention (PCI): angioplasty + stent ASAP !!!
- Coronary artery by-pass grafting
PCI in STEMI
Angioplasty (balloon dilation of the lesion)
Positioning of a stent: a tube-shaped device, placed in the coronary arteries, to keep the arteries open in the treatment of coronary heart disease
https://www.youtube.com/watch?v=36_qHWLFzI0
PCI vs CABG
ACS NSTEMINon ST elevation myocardial infarction
NSTEMI/UA
Generally suboccluded artery, instable plaque
Generally in patients with multivessel disease
Generally non-transmural infarction
Diagnosis as for STEMI (clinical presentation, EKG, +/- echo; troponin)
Need to stabilize the patient (and the plaque):
- Antiplatelet drugs
- Anticoagulant drugs
- Coronary vasodilators
- Management of pain
Need to perform a coronary angiography within 72h (generally in 24-48h) according to patient’s risk profile
Treatment as for STEMI (PCI, CABG)
Acute coronary syndromes vs chronic coronary artery disease
Factors affecting myocardial oxygensupply/demand
FIXED, CHRONIC STENOSIS
STRESS SITUATIONS(exercise, emotions, tachycardia, cold)
Cardinal symptom:chest pain
Chest pain, pressure or discomfort
(Atypical symptoms in diabetics)
CHRONIC ANGINA: reproducibly occurring during stress (e.g. running, walking rapidly, walking after eating, walking in coldenvironments…)
Chronic coronary artery disease
Stable plaque, fixed stenosis, chronic setting no need to hurry
Resting coronary flow is maintained until there is an approximately 90% reduction of coronary arterial flow.
The ability to maintain the maximum flow (termed coronary flow reserve) is impaired with approximately 50% coronary stenosis. An increase in coronary flow can be achieved by increased oxygen demand with exercise (treadmill or bicycle), b-adrenergic agonist (dobutamine) or by direct vasodilator (adenosine, dipyridamole).
Chronic coronary artery disease: diagnosis
Stress tests or anatomical imaging techniques for diagnosis, according to pre-test probabilityof disease
Stress tests (EKG, echo, scintigraphy, MRI)
- Exercise stress
- Pharmacological stress
- Dobutamine (inotropism and chronotropism)
- Dypiridamole (coronary vasodilation)
- Adenosine (coronary vasodilation)
Anatomical imaging techniques
- Coronary computed tomography (non-invasive)
- Coronary angiography (invasive)
Exercise EKG
Need for a maximal, symptom limited effort where > 85% of maximal heart rate is reachedWe look for downsloping ST-segment depression and symptomsEasy to perform, costless, widely availableRelatively low sensitivity and low specificity
Exercise stress or pharmacologicalstress echo
https://www.youtube.com/watch?v=UXMJkYg0DhY
3’50’’
We look for wall motion abnormalities occurring during pharmacological or physicalstress, which are not present at rest
Good sensitivity and specificity
Need for a good acoustic window
Myocardial perfusion single photon emission-computed tomography
Radioactive tracer
We look for abnormal cardiac distribution of the tracer during stress, which resolvesat rest
Good sensitivity and specificity for heterogeneous coronary artery stenosis (3-vessel disease may not be properly diagnosed)
Low availability (need for Nuclear Medicine)
Cardiac MRI
We look for perfusion abnormalities occurring during stress (coronary flow reserve)
High sensitivity and specificity for CAD
Coronary computed tomographyangiography
Anatomical, CT-based, reconstruction of coronary arteries
Optimal in case of low pre-test probability of CAD
Poor visualization of stenosis if high calcium burden
Coronary angiography
Coronary intravascular ultrasound (IVUS)
Intravascular ultrasound (IVUS) is an intravascular imaging modality primarily used in interventional cardiology to characterize lesion morphology, quantify plaque burden, guide stent sizing, assess stent expansion, and identify procedural complications.
Using a dedicated catheter with ultrasound-based technology an image is obtainable from inside an artery producing cross-sectional images with a 360-degree view of the vessel. This technology overcomes many of the limitations of angiography, which utilizes x-ray technology to produce a 2-dimensional lumenogram of a 3-dimensional structure.
Rather than assessing the vessel from the outside as with angiography, IVUS provides the assessment from within the vessel.
Intravascular ultrasound of a coronary artery allows for identification and delineation of the lumen and the 3 layers of the arterial wall: the inner tunica intima, the muscular tunica media, and the outer tunica adventitia.
It can be especially useful in situations in which angiographic imaging is considered unreliable
Coronary intravascular ultrasound (IVUS)
Coronaryoptical computed tomography (OCT)
OCT catheters contain a single optical fiber that emits infrared light. OCTs measure the echo time delay and the signal intensity after its reflection or back-scattering from the coronary wall structures while simultaneously operating a pull-back along the coronary artery, and thus performing a scan of the segment of interest
The main applications of the OCT system are:
- Atherosclerotic plaque assessment
- Stent struts coverage and apposition assessment, and in stent restenosis evaluation
- PCI guide and optimisation
Coronaryoptical computed tomography (OCT)
Coronary angiography additional techniques: fractional flow reserve (FFR)
Coronary angiography additional techniques: fractional flow reserve (FFR)
Fractional flow reserve is defined as the pressure after (distal to) a stenosis relative to the pressure before the stenosis.
The result is an absolute number; an FFR of 0.80 means that a given stenosis causes a 20% drop in blood pressure. In other words, FFR expresses the maximal flow down a vessel in the presence of a stenosis compared to the maximal flow in the hypothetical absence of the stenosis.
FFR allows to determine the physiologic and hemodynamic significance of an angiographically intermediate coronary stenosis
Coronary angiography additional techniques: fractional flow reserve (FFR)
Treatment of chronic coronary arterydisease
Medical therapy (antiplatelet drugs, antiischemic drugs, control of risk factors)
PCI vs CABG
Exceptions to atherosclerotic coronaryartery disease
Coronary artery dissection
Coronary artery spasm
Microvascular dysfunction
Coronary artery dissection
Spontaneous coronary artery dissection (SCAD) is defined as an epicardialcoronary artery dissection that is not associated with atherosclerosis or trauma and not iatrogenic. The predominant mechanism of myocardial injury occurring as a result of SCAD is coronary artery obstruction caused by formation of an intramural hematoma (IMH) or intimal disruption rather than atherosclerotic plaque rupture or intraluminal thrombus.
Accounting for ACS in young women
Spontaneous coronary artery dissection is characterized by the spontaneous formation of an intramural hematoma, which can lead to compression of the true lumen and myocardial infarction.
No antiplatelet/anticoagulant drugs!!!
Coronary artery spasm (CAS)
The term coronary artery spasm (CAS) refers to a sudden, intense vasoconstriction of an epicardial coronary artery that causes vessel occlusion or near occlusion.
CAS had been thought to occur at a site of organic stenosis of a major coronary artery.
However, CAS appears in angiographically normal arteries as well and often diffusely involves the entire arterial tree and may even migrate from site to site
Treatment:
coronary vasodilators
Coronary artery microvasculardysfunction
Coronary artery microvasculardysfunction (CMD)
The aetiologies of CMD may be heterogeneous; several structural (e.g. vascularremodelling, vascular rarefaction, extramural compression, etc.) and functional [e.g. endothelial dysfunction, vascular smooth muscle cell dysfunction, and microvascularspasm, etc.] alterations have been proposed for the pathophysiological mechanismsof CMD
In the absence of coronary obstruction, CFR, the ratio of coronary flow achieved at maximal coronary vasodilation to flow under baseline conditions, reflects coronary microvascular function such that a reduced CFR indicates CMD
Treatment: ?