Beneficial Effects of the Coronary Collateral Circulation on Tachycardia-Induced Myocardial Ischemia during Experimental Coronary Stenosis

摘要

This study was designed to determine whether coronary collaterals have preventive effects on tachycardia-induced myocardial ischemia under partial restriction of proximal coronary artery inflow. Studies were carried out in dogs with developed coronary collaterals and control dogs. ST-elevation in epicardial and intramyocardial electrograms was used for assessing the degree of regional myocardial ischemia. In control dogs with coronary constriction (80% reduction of i.d.) pacing-induced tachycardia produced significant ST-elevation, 1.48±0.17mV in the inner layer and 0.79±0.29mV in the middle layer at a cardiac rate of 150/min, 3.58±0.38mV in the inner layer, 2.73±0.38mV in the middle layer, and 1.93±0.36mV in the outer layer at a rate of 180/min. In dogs with moderate collaterals ST-segment elevation was only 1.41±0.18mV in the inner layer and 0.96±0.24mV in the middle layer at a rate of 180/min. In dogs with abundant collaterals there was no significant ST-elevation during tachycardia. These findings indicate that blood supply to the affected myocardium via developed collaterals is sufficient to meet graded increases in metabolic requirements under the condition of limited coronary flow reserve in an experimental model simulating angina pectoris.