What is the most common cause of ischemia due to atherosclerotic disease in an adult patient with risk factors for atherosclerotic disease, specifically which arteries are involved?

The Most Common Cause of Ischemia is Atherosclerotic Disease of the Epicardial Arteries

The correct answer is (c) Epicardial arteries. Atherosclerotic disease predominantly affects the large epicardial coronary arteries (right coronary artery, left main, left anterior descending, and left circumflex), which are the primary site of plaque formation leading to myocardial ischemia 1.

Anatomical and Pathophysiological Basis

Atherosclerosis is fundamentally a disease of large and medium-sized epicardial arteries, not the smaller subendocardial or penetrating vessels. The major epicardial coronary arteries are where atherosclerotic plaques develop and cause clinically significant stenosis 2.

Why Epicardial Arteries Are the Primary Target

• Coronary atherosclerosis affects all four major epicardial arteries (right, left main, left anterior descending, and left circumflex) in a diffuse and extensive process among patients with symptomatic or fatal myocardial ischemia 2
• The entire lengths of epicardial arteries are involved with atherosclerotic plaque, though plaque size varies from segment to segment 2
• Epicardial stenosis is the dominant mechanism causing reduced coronary flow and myocardial ischemia in stable coronary disease 3

Clinical Manifestations

The atherosclerotic involvement of epicardial arteries leads to:

• Stable angina from fixed stenotic lesions causing supply-demand mismatch 3
• Acute coronary syndromes from plaque rupture and thrombosis in epicardial vessels 3
• Myocardial infarction when epicardial artery occlusion occurs 3

Why Other Options Are Incorrect

Subendocardial and Endocardial Vessels

• These are not primary sites of atherosclerotic disease but rather the regions most vulnerable to ischemia when epicardial flow is compromised
• The subendocardium suffers first during ischemia due to higher wall stress and lower perfusion pressure, but this is a consequence of epicardial disease, not the cause

Penetrating Arteries

• Small penetrating arteries (such as lenticulostriate arteries) are affected by lipohyalinosis from hypertension, not typical atherosclerosis 4
• These vessels cause lacunar strokes in the brain, not the typical ischemic heart disease pattern
• Penetrating coronary arteries can be compressed by hypertrophied myocardium but are not the primary site of atherosclerotic plaque formation 5

Clinical Implications

Understanding that epicardial arteries are the primary target of atherosclerosis guides all diagnostic and therapeutic strategies:

• Coronary angiography visualizes epicardial vessels to identify obstructive lesions 5
• Revascularization procedures (PCI and CABG) target epicardial stenoses 5
• Medical therapy aims to stabilize epicardial plaques and prevent thrombotic complications 1