Myocardial lactate extraction: Multi-determined metabolic function

Abstract

Myocardial lactate production indicates anaerobic metabolism resulting from hypoxia or anoxia. Clinically, myocardial lactate extraction of less than 10% has also been used as an indicator of ischemia. Sixteen healthy young male volunteers underwent coronary sinus and arterial catheterization. A coronary sinus pacing catheter was used to obtain blood samples and increase the heart rate to twice the resting rate. Hemodynamic measurements and blood samples for lactate, free fatty acids and glucose were obtained at rest and during pacing. Seven of 16 subjects (44%) had lactate extraction of less than 10% at rest and/or at maximal pacing. No subject produced lactate. There was no correlation between myocardial lactate extraction and arterial glucose. However, lactate extraction correlated inversely with the arterial levels of free fatty acids (r =-0.67; p < 0.01). In addition, a positive correlation was present between lactate extraction and the arterial lactate level (r = 0.78; p < 0.01). In conclusion, myocardial lactate extraction is dependent on multiple metabolic parameters and any absolute value short of production cannot be considered abnormal.