The Effect of Free Fatty Acids

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