Mechanism of increase of myocardial oxygen uptake produced by catecholamines¹

¹ Cardiology Branch, National Heart Institute, National Institutes of Health, Bethesda, Maryland

The relative roles of augmented hemodynamic performance and direct stimulation of oxidative metabolism in mediating the increase of myocardial oxygen uptake (MVo₂) produced by catecholamines have been examined in an isolated canine heart preparation. The responses of MVo₂ to graded doses of isoproterenol, norepinephrine, or epinephrine were determined before and after the induction of cardiac arrest with potassium. Although increases of MVo₂ occurred in the arrested state with the larger doses of the amines, they constituted only a small fraction, generally between 5 and 20%, of the increases produced by the same doses of amines when the hearts were beating. It is concluded that while large doses of catecholamines can increase oxidative metabolism of the nonbeating heart by a small amount, the increases of MVo₂ produced by catecholamines in the beating heart are due in large part to the hemodynamic alterations which the amines induce.

Key Words: myocardial O₂ consumption • myocardial metabolism • norepinephrine • epinephrine • isoproterenol

Submitted on March 23, 1965