Ischemic heart disease – etiology, classification, etiology, pathogenesis, and clinical manifestations.
Ischemic heart disease (IHD) — also called coronary artery disease (CAD) — is a group of heart disorders caused by an imbalance between myocardial oxygen supply and demand, almost always due to coronary artery atherosclerosis, resulting in myocardial ischemia.
Etiology
Primary cause
Atherosclerosis of coronary arteries (most common).
Predisposing (risk) factors
Non- modifiable
Age.
Male sex.
Family history/ genetic predisposition.
Modifiable
Hyperlipidemia (high LDL, low HDL).
Hypertension.
Smoking.
Diabetes mellitus.
Obesity, metabolic syndrome.
Sedentary lifestyle.
Classification
- 1 Chronic coronary syndromes (stable)
Stable angina pectoris.
Silent (asymptomatic) ischemia.
Ischemic cardiomyopathy.
- 2 Acute coronary syndromes (ACS)
Unstable angina.
Non- ST- segment elevation myocardial infarction (NSTEMI).
ST- segment elevation myocardial infarction (STEMI).
Sudden cardiac death.
Pathogenesis
Atherosclerotic plaque formation
- Endothelial injury → lipid accumulation → foam cell formation → fatty streak.
- Smooth muscle migration, collagen deposition → fibrous cap → mature atheromatous plaque.
Plaque evolution and complications
Stable plaques: thick fibrous cap, small lipid core → cause stable angina (predictable effort- related pain).
Unstable/vulnerable plaques: thin fibrous cap, large lipid core → prone to rupture.
Acute plaque change
Plaque rupture or erosion → exposure of subendothelial collagen and necrotic core → platelet adhesion and activation → thrombus formation.
Thrombus consequences
Partial occlusion → unstable angina, NSTEMI.
Complete occlusion → STEMI.
Other mechanisms contributing to ischemia
Vasospasm (Prinzmetal angina).
Embolism.
Coronary microvascular dysfunction.
Clinical manifestations
Stable angina pectoris
Episodic chest pain, usually on exertion or emotional stress.
Relieved by rest or nitroglycerin.
Pain: substernal, may radiate to left arm, neck, jaw.
Unstable angina
Increased frequency, severity, or occurs at rest.
Precursor to infarction (part of ACS).
Myocardial infarction (MI)
Severe, prolonged chest pain (not relieved by rest).
Sweating, nausea, dyspnea.
Can lead to arrhythmias, heart failure, shock.
Silent ischemia
No symptoms; common in diabetics and elderly.
Ischemic cardiomyopathy
Chronic ischemia → myocardial fibrosis → heart failure symptoms ( dyspnea, fatigue).