Myocardial balance of inorganic phosphate and enzymes in man. Effects of tachycardia and ischemia.

The effects of atrial pacing on the cardiac balance of inorganic phosphate (Pi) were studied during control, atrial pacing, and recovery periods in 29 patients. Group A (n= 18) who had roentgenographically demonstrated coronary artery disease (CAD) developed angina during pacing, and showed mean myocardial lactate (L) production, abnormal left ventricular end-diastolic pressure (LVEDP) and ST segment depression. Group NA (n = 11), composed of six patients with CAD and five subjects with no demonstrable cardiac disease, had normal lactate metabolism, LVEDP, and ST segments during pacing. In addition, blood levels of two enzymes were determined: creatine phosphokinase (CPK) in nine patients of Group A and six patients of Group NA, and glutamic oxaloacetic transaminase (GOT) in eight patients of each group. During control, small uptake of Pi was observed in both groups. During pacing, Group A showed first a fall and then abolition of mean Pi uptake, and during the early recovery period,