Effects of intracoronary infusion of nicardipine during silent ischaemia on myocardial metabolism and function

The effects of an intracoronary infusion of nicardipine (0.2 mg over 10 min) on myocardial substrate uptake and function were studied in 16 patients with coronary artery disease and angina pectoris. Silent ischaemia, demonstrated by myocardial lactate production, was induced twice by pacing below anginal threshold. Nicardipine or saline was randomly infused during the first or second pacing. During pacing with nicardipine, no systemic effect was noted but coronary sinus flow increased (+ 18%; P < 0.015) and myocardial oxygen uptake decreased by 12% (P < 0.025). Transcardiac lactate production did not improve (-8 to -10 μmol min^-1; NS) but net lactate uptake, estimated from radiolabelled lactate uptake, tended to rise and the glutamine uptake increased from 1.8 to 5.5 μmol min^-1 (P < 0.04). During recovery after pacing, lactate production decreased faster and LV peak (+) dP/dt and relaxation rate were significantly better after nicardipine infusion than after saline. Thus, during silent ischaemia induced by an increased oxygen demand, intracoronary nicardipine did not prevent lactate release but allowed a faster metabolic and functional recovery. These beneficial effects of nicardipine could be explained by an improved myocardial perfusion or by an effect on intracellular calcium homeostasis.