Effects of Coronary Artery Occlusion in Animals with Hypertension and Left Ventricular Hypertrophy

Abstract

Chronic arterial hypertension (HT) and left ventricular hypertrophy (LVH) increase the morbidity and mortality of acute myocardial infarction in patients. In this article, we discuss earlier studies from Koyanagi et al. in our laboratory that showed that when animals with chronic HT and LVH (HT-LVH) were subjected to acute coronary artery occlusion (CAO), there was a 3.5-fold increase in mortality and a 35% increase in infarct size expressed as a percent of the area at risk. We subsequently determined the effect of HT-LVH on the wavefront of myocardial infarction. Dogs were made hypertensive using a single-kidney, single-clip model of renovascular hypertension that produced mean arterial blood pressure (BP) = 141 +/- 3 mm Hg and left ventricular:body weight = 5.8 +/- 0.1 g/kg (p less than 0.05 vs. control animals). Conscious animals with HT-LVH and control animals were subjected to 1 or 3 h of CAO. Infarct and risk areas were measured using triphenyltetrazolium chloride (TTC) stain and barium angiography, respectively. The results suggested that the wavefront of infarction was accelerated in animals with HT-LVH. Further studies suggested that the wavefront of myocardial infarction could be markedly retarded by normalizing blood pressure (nitroprusside) 1 h following CAO. Recent studies in an animal model of HT-LVH suggested that electrophysiological abnormalities occur when these animals were subjected to CAO. Sixty-five percent of animals with HT-LVH had sudden death during CAO compared to 27% of the control group. We studied whether chronic beta-adrenergic blockade would reduce mortality associated with CAO in animals with HT-LVH.(ABSTRACT TRUNCATED AT 250 WORDS)