Ischemic heart disease (IHD)
Also known as: IHD, coronary artery disease, coronary heart disease
Ischemic heart disease (IHD) is a group of conditions caused by inadequate blood supply to the myocardium, most often from atherosclerotic narrowing of the coronary arteries. It encompasses angina pectoris, myocardial infarction, chronic ischemic heart disease, and sudden cardiac death.
Ischemic heart disease (IHD) — the abbreviation "IHD" is a staple of medical charts and exam questions — describes cardiac disease resulting from an imbalance between myocardial oxygen demand and supply. The dominant cause is atherosclerosis of the coronary arteries, which narrows the vessel lumen and limits blood flow to the heart muscle; plaque rupture with superimposed thrombosis produces the acute syndromes.
IHD is classically taught as four overlapping syndromes. Stable angina is chest pain on exertion, relieved by rest or nitroglycerin, typically appearing when a fixed plaque occludes roughly 70% or more of the lumen. Unstable angina is pain at rest or with accelerating frequency, usually from plaque disruption with incomplete occlusion. Myocardial infarction is frank myocyte death from prolonged ischemia, most often due to occlusive thrombus. Chronic ischemic heart disease and sudden cardiac death — commonly from a lethal arrhythmia such as ventricular fibrillation — round out the spectrum.
Clinically and epidemiologically, IHD is among the leading causes of death worldwide. Its major modifiable risk factors mirror those of atherosclerosis: hypertension, hyperlipidemia, diabetes, smoking, and obesity. Ischemia also underlies many arrhythmias, since infarcted or ischemic myocardium disrupts normal conduction.
USMLE Step 1 tests IHD heavily in cardiovascular pathology: the timeline of gross and microscopic changes after MI, the vessels most often occluded (LAD most common), complications by post-MI day, and ischemia-driven arrhythmias. Achievable's USMLE Step 1 course covers ischemic heart disease and arrhythmias in its cardiovascular pathology chapters.
Key takeaways
- IHD is myocardial disease caused by inadequate coronary blood supply, most often from coronary atherosclerosis.
- Its four classic syndromes are angina pectoris, myocardial infarction, chronic ischemic heart disease, and sudden cardiac death.
- Stable angina reflects fixed stenosis (about 70% or more occlusion); unstable angina and MI usually involve plaque rupture and thrombosis.
- Sudden cardiac death in IHD is most often due to a ventricular arrhythmia.
- Step 1 emphasizes post-MI histologic timelines, common culprit vessels, and MI complications.