Cardiac energy metabolism in patients with chest pain and normal coronary angiograms

In 70 patients (94% were a consecutive series) with angina pectoris and nor mal coronary angiograms, we measured cardiac exchange of lactate, glucose, free fatty acids (FFAs), glutamate, alanine, citrate, and oxygen together w ith coronary sinus blood flow and blood pressure in response to pacing (150 beats/min). Twelve patients had an abnormal exercise stress test; 26 devel oped ST depression and 46 had chest pain in response to pacing. Sixteen pat ients had no ST changes (exercise/pacing) and no pain during pacing. Pacing induced an increase in cardiac carbohydrate extraction and a decrease in F FA extraction in the entire group of patients. Less than 3% of patients had significant cardiac lactate release in response to pacing, and there were no consistent differences in the cardiac metabolic or hemodynamic responses between patient groups. The pacing-induced shift from FFA to carbohydrate extraction probably reflects the cardiac response to an acute workload. A d efinite sign of cardiac ischemia (lactate production) was a rare finding in these patients and not confined to the demonstration of electrocardiograph ic signs of ischemia. (C)2000 by Excerpta Medico, Inc.