EFFECT OF PROPRANOLOL ON REGIONAL MYOCARDIAL BLOOD-FLOW AND OXYGEN-CONSUMPTION

  • 1 January 1976
    • journal article
    • research article
    • Vol. 198  (2) , 435-443
Abstract
The effect of propranolol on regional myocardial blood flow and O2 consumption (M.ovrhdot.VO2) in the isolated supported dog heart preparation perfused at a constant coronary blood flow was determined. The transmural distribution of blood flow, determined by the radioactive microsphere technique, was expressed as the epicardial/endocardial blood flow ratio (epi/endo). Propranolol (0.5 mg/kg i.v.) significantly decreased heart rate and myocardial contractile force and increased coronary artery perfusion pressure due to an increase in coronary vascular resistance. These hemodynamic changes were accompanied by significant decreases in epi/endo (increased endocardial perfusion) and M.ovrhdot.VO2. Reduction of perfusion pressure to control by a decrease in total coronary blood flow produced no further change in epi/endo or M.ovrhdot.VO2. Increasing heart rate to control increased epi/endo to predrug levels. Contractile force and M.ovrhdot.VO2 remained reduced below control. Norepinephrine infusion (1 .mu.g/min intracoronary) significantly increased heart rate and contractile force and decreased perfusion pressure. These changes were accompanied by an increase in epi/endo and M.ovrhdot.VO2. Propranolol (0.5 mg/kg i.v.) abolished the response to norepinephrine. Propranolol may produce beneficial effects in angina pectoris by a decrease in epi/endo (via a reduction in heart rate) and M.ovrhdot.VO2 and by .beta. adrenergic blockade of the deleterious effects of catecholamines.