The effect of free fatty acids on myocardial oxygen consumption during pacing and catecholamine infusion in man

Abstract

The effect of myocardial uptake of free fatty acids (FFA(u)) on myocardial oxygen consumption (MV̇O2) in relation to increased heart rate and inotropic stimulation was determined in patients with coronary artery disease. Sub-maximal atrial pacing and isoproterenol stimulation increased MV̇O2 by 66% and 142%, respectively, at similar heart rates. Inhibition of lipolysis with β-pyridyl carbinol almost abolished FFA(u) and reduced MV̇O2 significantly. Increased heart rate contributed 47% and FFA(u) 50% of the raised MV̇O2 during catecholamine stimulation. During inhibition of lipolysis, the increased MV̇O2 attributed to inotropic stimulation was 30%. Augmentation of FFA(u) by trigylceride/herapin infusion increased MV̇O2 significantly above control levels, both during pacing and isoproterenol infusion. We conclude that MV̇O2 is closely correlated to FFA(u), catecholamines sensitize the heart to FFA, and increased FFA(u) account for a major part of the increased MV̇O2 during catecholamine stimulation. The importance of reducing heart rate and lipolysis to reduce myocardial oxygen requirements is emphasized.