MYOCARDIAL ischemia occurs whenever there exists a discrepancy between the available oxygen supply and the work requirements of the heart muscle. The balance of these two factors is essential for cardiac function. An arterial blood flow below that customarily available for work performance results in myocardial ischemia.
As shown in table 1, a decrease in oxygen supply to the heart muscle may be absolute, owing to narrowing of arterial caliber by occlusive disease, prolonged spasm or a decrease in the oxygen-carrying capacity of the blood (anemia). The decrease may be relative when the arterial supply provided for the normal heart must serve a greater muscular mass than normal (as in cardiac hypertrophy) or when the energy requirements exceed the maximal capacity of the coronary bed. It is also possible that the utilization of available oxygen is impaired either because oxygen is offered to the tissues in nonutilizable form (as in
HECHT HH. CONCEPTS OF MYOCARDIAL ISCHEMIA. Arch Intern Med (Chic). 1949;84(5):711–729. doi:10.1001/archinte.1949.00230050047002
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