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

sergio.caravita@unibg.it

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: ?