Coronary Atherosclerosis

The most common cause of death from cardiovascular disease is coronary atherosclerosis. Approximately half the individuals with coronary artery disease die suddenly. Sudden death is, in fact, the initial symptom in approximately 25% of individuals dying of coronary atherosclerosis. In the authors' experience, coronary artery disease accounts for 76.3% of adults' dying suddenly and unexpectedly of cardiovascular disease who come to autopsy. The frequency will change to some degree depending on the population handled by a particular office and the criteria used for selection of cases for autopsy.

In contrast to the number of individuals who die in the hospital of coronary artery disease, in a medical examiner's office, acute coronary thrombosis and acute myocardial infarcts are the exception rather than the rule. In a study of 500 consecutive autopsies of individuals aged 20-99 years who died suddenly and unexpectedly of coronary artery disease, only 67 (13.4%) showed acute thromboses, grossly.3 The left coronary artery and its branches showed a slightly higher incidence of thrombosis compared with the right. The low incidence of thrombosis in individuals' dying suddenly is in agreement with other authorities. In contrast, studies of hospitalized patients show a high rate of thrombosis — 87.3% by DeWood et al.4 Gross myocardial scarring representing previous areas of old infarction has been reported as being present in 34.8% of individuals dying suddenly, with 8.4% demonstrating evidence of acute myocardial infarction, grossly.

What is present in all deaths due to coronary atherosclerosis is severe atherosclerosis of the coronary vessels. Significant obstruction of the coronary artery lumen usually requires 75% narrowing of the lumen (Figure 3.1). In individuals with hypertensive cardiovascular disease, one often does not see the classical eccentric narrowing due to plaque formation of pure coronary atherosclerosis, but rather concentric thickening of the walls by atherosclerotic deposits. In individuals older than 60 years of age, the coronary arteries may present yet another picture. While the lumina are patent, the vessels are rigid calcified tubes because of calcium deposits in the walls of the vessels.

In some individuals, while the epicardial coronary arteries appear non-occluded, microscopic examination of the myocardium reveals severe, occlusive dysplasia of the intramural coronary arteries.5 The dysplasia is characterized by severe medial thickening, with smooth muscle disorganization and marked luminal narrowing. Burke and Virmani describe four sudden deaths due to this entity in young (12-31 years) individuals. 5

In most individuals who die suddenly and unexpectedly of atherosclerosis of the coronary arteries, at least two vessels are involved. Occasionally, an

Figure 3.1 Left anterior descending coronary artery of 21-year-old male with 75% narrowing of lumen due to atherosclerosis.

individual will die with single vessel disease with a single strategically located atherosclerotic plaque. This plaque, which produces at least 75% narrowing of the lumen, is usually found in the proximal portion of the left anterior descending coronary artery (the "widow-maker") almost immediately after its origin. This is an extremely critical point in this vessel, in that the left coronary artery begins supplying significant myocardial tissue shortly after its origin. In contrast, the right coronary artery does not supply any significant amount of myocardial tissue until it gives off the posterior descending vessel. In a study of 451 deaths due to CAD, in 54 of the cases (11.9%) significant disease was confined to one vessel. The vessel was the left anterior descending coronary in 40 cases; the circumflex in 4 and the right coronary in 10.

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