Induced Tachycardia: Its Effect upon the Coronary Hemodynamics, Myocardial Metabolism and Cardiac Efficiency of the Intact Dog12

Abstract

Cardiac output (Fick), and coronary blood flow (N2O Fick) were increased before and after the induction of tachycardia by pacemaker. No striking changes occurred in the systemic or pulmonary hemodynamics except a fall in stroke volume. Coronary blood flow increased from 81 to 148 ml/100 g/myocardium/minute, and cardiac metabolic rates for O2 and CO2 increased two-fold. Stroke myocardial O2 consumption was unchanged. Calculated cardiac efficiency fell significantly from 24% to 12%.