Effects of chronic hypertension and left ventricular hypertrophy on the incidence of sudden cardiac death after coronary artery occlusion in conscious dogs.

Abstract

When acute myocardial infarction occurs in patients with hypertension and left ventricular hypertrophy (LVH), the incidence of sudden cardiac death increases markedly. Possible explanations include increased size of the occluded vascular bed secondary to more extensive atherosclerotic coronary vascular disease in the presence of hypertension, decreased coronary reserve secondary to LVH, and intrinsic electrophysiologic abnormalities in hypertrophied cardiac muscle. To explore these possibilities, we produced acute circumflex coronary occlusion during the resting, conscious state in 32 control dogs and in 28 dogs with hypertensive LVH. Before coronary occlusion, mean arterial pressure was 96 +/- 0.1 mm Hg in control dogs and 125 +/- 5 mm Hg in dogs with hypertensive LVH (p less than 0.01). The control left ventricular/body weight ratio was 4.5 +/- 0.1 g/kg, compared with 6.1 +/- 0.1 g/kg in hypertensive LVH (p less than 0.01). Cumulative mortality at 6, 24 and 48 hours was 9%, 13% and 16% in control dogs and 32%, 43% and 54%, respectively, in dogs with hypertensive LVH (all p less than 0.01 vs control). The perfusion fields of the occluded vessel defined by postmortem coronary angiography were similar in the two groups (31 +/- 2% of left ventricular mass for control vs 29 +/- 2% for hypertensive LVH). Thus, the increased incidence of sudden cardiac death after coronary artery occlusion in hypertensive LVH dogs cannot be explained by increased size of the occluded vascular bed and is probably related to the decreased coronary reserve or intrinsic electrophysiologic abnormalities that characterize pressure-induced hypertrophied cardiac muscle.