Ischemic Heart Disease Flashcards
what is ISH/CAD? what is angina ?
Coronary artery disease (CAD): ischemic heart disease due to narrowing or blockage of coronary arteries, most commonly due to atherosclerosis, resulting in a mismatch between myocardial oxygen supply and demand
Angina: chest pain caused by myocardial ischemia (necrosis of myocytes has not yet occurred) due to narrowing (e.g., thrombus) or spasm (e.g., Prinzmetal angina) of the coronary artery
Stable angina: a type of angina that occurs upon exertion, mental stress, and/or exposure to cold and usually subsides within 20 minutes of rest or after administration of nitroglycerin
what is coronary steal syndrome?
-Definition: a phenomenon of vasodilator-induced alteration of coronary blood flow in patients with coronary atherosclerosis resulting in myocardial ischemia and symptoms of angina
-Pathomechanism
Long-standing CAD requires maximal coronary arterial dilation distal to the stenosis to maintain normal myocardial function.
In CAD, the affected coronary artery is maximally dilated distal to the stenosis to compensate for the reduced blood flow
If a vasodilator (e.g., dipyridamole) is administered, the subsequent vasodilation of healthy vessels causes these to “steal” blood from the stenotic blood vessels, resulting in poststenotic myocardial ischemia.
-Clinical relevance
Coronary steal is the underlying mechanism of pharmacological stress testing.
Administration of vasodilators (e.g., dipyridamole) → coronary vasodilation → decreased hydrostatic pressure in the normal coronary arteries → blood shunting back to well-perfused myocardium → decreased flow to the ischemic myocardium → myocardial ischemia downstream to the pathologically dilated vessels → angina pectoris and/or ECG changes
what are the types of ischemia?
- Reversible ischemia: Tissue is ischemic but not irreversibly dead and, therefore, still potentially salvageable.
- Hibernating myocardium: a state in which myocardial tissue has persistently impaired contractility due to repetitive or persistent ischemia
- Partially or completely reversible when adequate oxygen supply is restored (e.g., after angioplasty or coronary artery bypass grafting)
- Seen in angina pectoris, left ventricular dysfunction, and/or heart failure - Irreversible ischemia
what are the clinical features of cad?
1.Angina:
Angina is the cardinal symptom of CAD. Patients with CAD usually become symptomatic when the degree of coronary stenosis reaches ≥ 70%.
Typically retrosternal chest pain or pressure
Pain may radiate to the left arm, neck, jaw, epigastric region, or back.
Pain is not affected by body position or respiration.
No chest wall tenderness
May gradually increase in intensity
May present as gastrointestinal discomfort
May be absent, especially in geriatric and diabetic patients.
Dyspnea
Dizzinesss, palpitations
Restlessness, anxiety
Autonomic symptoms (e.g., diaphoresis, nausea, vomiting, syncope)
- Stable angina
Symptoms are reproducible/predictable
Symptoms often subside within minutes with rest or after administration of nitroglycerin
Common triggers include mental/physical stress or exposure to cold
explain vasospastic angina?
Angina caused by transient coronary spasms
Not affected by exertion (may also occur at rest)
Typically occurs early in the morning
Epidemiology [9]
Average age of onset: 50 years
-Etiology
Cigarette smoking; use of stimulants (e.g., cocaine, amphetamines), alcohol, or triptans
Stress, hyperventilation, exposure to cold
Associated with other vasospastic disorders (e.g., Raynaud phenomenon, migraine headaches)
Common atherosclerotic risk factors (except smoking) do not apply to vasospastic angina.
-Diagnostics
Reversible ST elevation on ECG
No troponin I or troponin T elevations on serial measurements
Coronary spasms on angiography confirm the diagnosis.
-Treatment
Lifestyle modification (especially smoking cessation)
Calcium channel blockers (CCBs): first-line agents for acute attacks and prophylaxis
Long-acting nitrates
Avoid beta-blockers
how do you diagnose CAD?
- Pre test probability of CAD:
Probability of CAD Low (< 10%) Noncardiac chest pain in: Men < 40 years Women < 60 years Atypical angina in women < 50 years No further diagnostic tests are recommended
Intermediate (10–90%) Noncardiac chest pain in: Men ≥ 40 years Women ≥ 60 years Atypical angina in: Women ≥ 50 years Men of all ages Typical angina in: Women < 60 years Men < 40 years Cardiac stress test Pharmacological testing (or exercise ECG) Nuclear stress test Dobutamine stress echocardiography
High (> 90%) Typical angina in: Women ≥ 60 years Men ≥ 40 years Cardiac stress test Nuclear stress test Dobutamine stress echocardiography Coronary angiography
- Resting ECG:
Usually normal in stable angina
ST segment depression or T wave inversion/flattening indicates previous MI or unstable angina
3a. Cardiac exercise stress test: test of choice (preferred over pharmacological testing because exercise can achieve a higher level of strain)
The patient exercises until the target heart rate is achieved (e.g., on a treadmill).
Maximum heart rate = 220 – age (in years)
Target heart rate = 85% of the maximum heart rate
-Contraindications
Acute myocardial infarction with elevated troponin levels and/or ST elevations (within the past 2 days)
Unstable angina pectoris or ST depressions at rest
Hemodynamically significant arrhythmias
Mental or physical impairment to exercise
b.Cardiac pharmacological stress test: performed if the patient is unable to exercise or has contraindications for exercising
Positive inotropic/chronotropic substances (e.g., dobutamine) or vasodilators (e.g., dipyridamole or adenosine) are administered to simulate the effect of exercise on the myocardium.
-Contraindications
For adenosine, dipyridamole
Active bronchospasm or reactive airway disease
Low
For dobutamine
Myocardial infarction within the last week
Unstable angina
Tachyarrhythmias
Preparation
If cardiac stress test is performed for primary diagnosis, withhold the following:
Beta blockers, CCBs, nitrates (48 hours)
Methylxanthines (especially if a pharmacological cardiac stress test is considered); caffeine (12 hours); aminophylline; dipyridamole
If a cardiac stress test is performed for treatment evaluation, medication can be continued.
Clinical findings
The following findings should prompt immediate interruption of stress testing:
New onset/intensification of chest pain
dyspnea
Decrease in systolic BP below the resting BP
ECG (detection method of choice)
Downsloping or horizontal ST depressions of ≥ 0.1 mV in the limb leads and ≥ 0.2 mV in the precordial leads
ST elevations ≥ 0.1 mV
Excessive or delayed increase in heart rate
Imaging: (echocardiography, myocardial perfusion imaging)
Used if the patient’s resting ECG cannot be interpreted
Echocardiography
Radionuclide myocardial perfusion imaging
when should a pt undergo cardiac cathterisation?
Patients with new-onset chest pain, ST-depression, hypotension, or arrhythmias should undergo cardiac catheterization.
-Indications
Persistent symptoms of angina despite appropriate therapy
Abnormal results of noninvasive testing
high clinical suspicion of CAD
-Advantages
Considered the gold standard of CAD diagnosis since it provides:
Information on several parameters; coronary blood flow; cardiac output
Direct visualization of coronary arteries (coronary angiography)
therapeutic intervention using percutaneous coronary intervention
what is the treatment of CAD?
- Approach:
All patients: risk factor reduction and antiplatelet drugs
Mild CAD: pharmacologic therapy
Moderate CAD: consider coronary angiography and percutaneous transluminal coronary angioplasty (PTCA)/percutaneous coronary intervention (PCI)
Severe CAD: coronary angiography and revascularization or coronary artery bypass grafting - Antianginal treatment
Goal: reduction of MVO2 (myocardial O2 demand)
This can be achieved by altering the following parameters that influence the extent of MVO2:
Blood pressure
Heart rate
Inotropy (contractility)
Ejection time
End-diastolic volume
First-line
Beta blockers (except in vasospastic angina)
Can reduce the frequency of coronary events
Partial beta agonists like pindolol and acebutolol should be used cautiously.
Nitrates
Suitable for relief of acute angina or for long-term treatment
Second-line
CCBs
Ranolazine: a metabolic modulator that reduces myocardial oxygen demand without altering the heart rate, blood pressure, contractility, and/or end-diastolic volume
stable angina that is refractory to first-line treatment
-Mechanism of action
Inhibition of late inward sodium channels on cardiac myocytes → reduced calcium influx (via sodium-calcium channel pump) → reduced wall stress and oxygen demand
Decreased rate of fatty acid beta-oxidation (aerobic process) with a simultaneous increase in glycolysis (anaerobic process)
Side effects
Nausea, constipation
Headache, dizziness
Combination therapy
Beta blocker PLUS nitrate
CCB (nondihydropyridine) PLUS nitrate (CCBs, such as verapamil, have a similar effect to beta blockers.)
3.Revascularization
Indications
Stable angina, in the presence of:
Activity-limiting symptoms despite optimal medical treatment
Contraindications to medical therapy
Stenosis of critical (e.g., LCA) or multiple coronary arteries
Acute coronary syndrome
Techniques
Percutaneous coronary intervention
Coronary artery bypass grafting
Percutaneous transluminal coronary angioplasty (PCTA)
what are the preventions of CAD?
Antiplatelet drugs
Aspirin or clopidogrel; for all patients with CAD
Arterial hypertension management
Beta blockers: first-line therapy
ACE-inhibitors: in post-MI patients
Diabetes mellitus: maintenance of HbA1c at < 7% levels
STATINS
what is the difference between unstable angina, NSTEMI and STEMI?
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