Local Metabolic Rate and Left Ventricular Oxygen Consumption in the Intact Dog Heart

Abstract

Myocardial heat production was measured with thermistors in mid-portions of the left ventricular wall during 2- to 10-second occlusions of left coronary artery. Following left coronary occlusion, a linear rise in mycocardial temperature of 2 to 10 seconds' duration presaged left ventricular dilation and a fall in myocardial oxygen tension. The initial rate of temperature rise (δT/δt (°C/min)) was used to calculate metabolic heat production: δ=(δT/δt)⁻s⁻ 100, where δ is in cal/min ⁻100 g, s = specific heat of the tissue. During control periods, δ averaged 42 ± 4 cal/min-100 g. Myocardial oxygen consumption (MVO2), determined simultaneously, was equivalent to 47 ± 4 cal/min-100 g. A linear relationship was obtained between δ and MVO₂ over a wide range of metabolic rates induced by i.v. infusion of noradrenaline, isoproterenol, or angiotensin, and by bleeding. The present results confirm that myocardial oxygen consumption accounts for virtually all energy produced by the heart.

Key Words:

• External work
• local metabolic rate
• myocardial calorimetry
• myocardial drug effect
• myocardial fibre length
• myocardial ischemia
• myocardial metabolism
• myocardial oxygen tension
• myocardial temperature