Effect of nicorandil, a K+ATP -channel opener, on coronary capillary architecture and volume after early myocardial ischemia-reperfusion--a 3-dimensional confocal laser microscopic study--.

Background: Previous experimental and clinical studies have reported that nicorandil, an adenosine triphosphate (ATP)-sensitive K+ channel opener, exerts a beneficial effect on microvascular function and clinical outcome after myocardial ischemia. The present study assessed whether intravenous administration of nicorandil affects the 3-dimensional (3-D) architectural characteristics of capillaries and their volume after early myocardial reperfusion.

Methods And Results: Using the hearts of open-chest anesthetized rats, the left anterior descending artery was occluded for 7 min followed by reperfusion. Nicorandil or saline was infused intravenously during occlusion and reperfusion. The entire coronary microvasculature was filled with contrast medium after the hearts were arrested. Capillaries were observed 3-dimensionally by confocal laser scanning microscopy in both the control area and reperfused area of all samples. The capillary volume fraction was computed from the 3-D images. The reperfused area in both the nicorandil and saline groups showed characteristic architectural changes of the capillaries. Capillary volume fraction in the reperfused area was significantly reduced in saline group, compared with nicorandil group [12.7+/-7.2% vs 18.1 +/-5.3% (p<0.01)].

Conclusions: Intravenous nicorandil administration has a beneficial effect on capillary damage after reperfusion.