Ischemic heart disease is responsible for 500,000 deaths a year in the United States—or 25–30% of all deaths—and is the leading cause of death in most developed countries.
Ischemic heart disease is caused by narrowing of one or more of the three major coronary artery branches (Figure 23-1). These are functional end-arteries, and sudden occlusion of any one leads to infarction in the area of supply. However, gradual narrowing may permit development of collaterals that are sufficient to prevent infarction.
Blood supply to the myocardium (A) and areas of infarction resulting from the most frequent sites of coronary artery occlusion (relative frequency expressed as a percentage). (B–D) The exact area of myocardium affected will vary depending on normal anatomic variation in blood supply and the extent of collateral circulation that exists at the time of coronary occlusion.
Atherosclerosis accounts for 98% of cases of ischemic heart disease. The risk factors for ischemic heart disease are the same as those for atherosclerosis (Chapter 20: The Blood Vessels).
Other rare causes of coronary artery narrowing include coronary artery spasm (Prinzmetal angina); coronary artery embolism, most commonly in infective endocarditis; coronary ostial narrowing in syphilis and Takayasu's aortitis; coronary ostial occlusion in aortic dissection of the aorta; and various types of arteritis involving the coronary arteries, including polyarteritis nodosa, thromboangiitis obliterans, and giant cell arteritis.
Ischemic heart disease may be manifested clinically in many ways (Figure 23-2). The more important ones—myocardial infarction, angina pectoris, sudden death, cardiac arrhythmias, and cardiac failure—are discussed below. An individual patient with ischemic heart disease may manifest more than one of these conditions.
Causes and clinical consequences of ischemic heart disease.
Approximately 1.5 million people in the United States suffer a myocardial infarction (heart attack) every year; of these, 25% die in the acute phase—half before they reach a hospital. Another 10% of patients die in the first year after surviving an infarct. Most patients are over 45 years of age, and men are affected three times more frequently than women, paralleling the incidence of atherosclerosis.
Except in those rare causes of nonatherosclerotic coronary artery narrowing listed above, most patients who suffer myocardial infarction have severe atherosclerotic narrowing of one or more coronary arteries (Figure 23-3; see also Chapter 20: The Blood Vessels). A fresh thrombus overlying an atherosclerotic plaque is found in 40–90% of cases (Figure 23-4), the frequency varying greatly in different studies. Thrombosis may be ...