Abnormalities in the coronary circulation that occur as a consequence of cardiac hypertrophy.

Myocardial ischemia is frequently observed in patients with cardiac hypertrophy even when the conduit coronary arteries are normal. Recent studies indicate that impaired coronary reserve in hypertrophied hearts probably occurs because growth of the coronary bed does not keep pace with increases in cardiac mass. The imbalance between vascular proliferation and muscle growth is probably most severe when cardiac hypertrophy is produced by pressure overload. Experimental studies also suggest that abnormalities intrinsic to pressure-hypertrophied heart muscle (decreased capillary density; decreased coronary reserve; electrophysiologic abnormalities) adversely affect the response of the enlarged heart to sudden coronary occlusion. When animals with hypertension and left ventricular hypertrophy are subjected to sudden coronary occlusion, the incidence of sudden cardiac death is increased severalfold and infarct size is substantially augmented. These observations suggest that abnormalities in the coronary microcirculation that accompany cardiac hypertrophy play a significant role in the pathogenesis of the complications associated with cardiac hypertrophy.