Left ventricular heat production during induced tachycardia in the intact dog

¹ Cardiovascular Research Laboratory, Department of Medicine, University of Wisconsin Medical School, Madison, Wisconsin

It is well established that heart rate is a determinant of myocardial oxygen consumption. However, it has not been demonstrated that the increase of oxygen consumption at faster rates actually represents loss of energy, degraded as heat. Control measurements of systemic and coronary hemodynamic and metabolic parameters and left ventricular heat production (measured by a recently reported method) were obtained in 10 dogs. Tachycardia was then induced electrically and the same parameters redetermined. Significant increases occurred in coronary blood flow, cardiac metabolic rate of oxygen, and left ventricular heat production. The elevated myocardial oxygen consumption at higher rates is associated with increased heat production.

Key Words: myocardial calorimetry during induced tachycardia • LV heat production and cardiac rate

Submitted on August 31, 1964