Myocardial metabolism in cyanotic congenital heart disease studied by arteriovenous differences of lactate, phosphate, and potassium at rest and during atrial pacing.

To study myocardial metabolism in chronic hypoxia due to cyanotic congenital heart disease, coronary arteriovenous differences of lactate (L), pyruvate (P), inorganic phosphate (Pi) and potassium (K) were measured in 14 cyanotic patients and seven controls, at rest and during atrial pacing. At rest, there was no difference in any parameter between cyanotic and noncyanotic patients. During atrial pacing (150-175/min) for 10 min, a moderate drop in L-extraction occurred in the control patients with some increase in L/P ratio in coronary venous blood. Cyanotic patients fell into two groups: in nine (group I), the arterial oxygen saturation (SaO2) dropped with pacing. Their L-extraction fell sharply, from 28.1 +/- 3.12 to --2.8 5.51 and L production occurred in five. There was a significance increase in coronary venous L/P ratio. Five cyanotic patients (group II) showed no drop in SaO2 with pacing, and L extraction as well as L/P ratio remained stable. Uptake of Pi was noted in all patients at rest, during pacing this disappeared in controls and group I cyanotics but not in group II. No K changes were seen in any patient. Thus, myocardial metabolism is normal at rest in patients with cyanotic CHD; during atrial pacing, a shift toward anaerobic metabolism occurs if SaO2 drops; cyanotic patients whose SaO2 remains stable appear to withstand pacing better than controls.