Coronary vasodilatory action after a single dose of nicorandil

Coronary hemodynamics and vasodilatory effects on major epicardial arteries were investigated after a single dose of nicorandil in 22 patients undergoing cardiac catheterization for suspected coronary artery disease. Nicorandil, 20 mg, was administered sublingually to 11 consecutive patients and 40 mg to 11 others. Systemic blood pressure decreased significantly without affecting the heart rate. Coronary sinus blood flow did not change significantly. As the mean aortic pressure decreased significantly by 13% after 20 mg and 21% after 40 mg of nicorandil, the calculated coronary vascular resistance decreased but did not reach statistical significance. There was a decrease in myocardial oxygen consumption (-14% and -22%, respectively), and this was consistent with a significant decrease in the calculated pressure-rate product of 19% and 24%, respectively. A total of 103 selected coronary segments, including 17 stenotic segments, were analyzed quantitatively using a computer-assisted coronary angiography analysis system. After 20 or 40 mg of nicorandil, a significant increase of the mean diameter was observed in the proximal (+9% and +7%), midportion (+10% and +11%) and distal (+15% and +13%) parts of the left anterior descending coronary artery. Corresponding values for the proximal (+13% and +10%) and distal (+10% and +15%) segments of the circumflex artery were observed. An increase in the obstruction diameter was also observed in all but 3 of the analyzed stenotic segments. The results demonstrate that nicorandil, in the route and doses used, causes a significant vasodilatation in the major epicardial coronary segments, including most stenotic segments, and decreases the myocardial oxygen demand with little effect on the resistance vessels.