Asymptomatic Coronary Atherosclerosis
If the degree of arterial obstruction is moderate and does not significantly reduce the blood supply to the myocardium, the disease may never be suspected by the patient or the physician. Results of autopsy studies among persons dying of other causes indicate that this is a common situation. In fact, practically all men in the United States have evidence of coronary atherosclerosis by age 50; it is only the degree of involvement that varies.
Even if the coronary arteries are grossly narrowed by intimal plaques, it still does not follow that the disease will be clinically evident or produce symptoms. This paradox can be explained partly by the fact that as the coronary arteries gradually narrow small branches of these vessels may enlarge or new branches may form in order to bring more blood to the myocardium. This additional blood supply, called collateral circulation, is of great importance in determining the clinical effects of coronary atherosclerosis since this network of vessels is often substantial enough to maintain an adequate blood supply to portions of the myocardium despite the presence of advanced atherosclerosis in a major vessel. It is the total blood supply to the myocardium rather than the state of the main coronary arteries that determines whether the disease will be symptomatic. It is important to realize there is no definite correlation between the extent of coronary artery disease and symptoms. In fact, about 30% of patients who die of CHD experience ence no symptoms of the disease before the fatal event.
Symptomatic Coronary Disease
Coronary heart disease, by definition, implies that the myocardium is affected by inadequate coronary blood flow. The symptoms of CHD are due to myocardial oxygen deprivation and are manifested in progressive order of severity by three main clinical patterns: angina pectoris, intermediate coronary syndrome (unstable angina), and acute myocardial in- farction. Each of these syndromes is described separately in the following pages.
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