COMPARATIVE-STUDY ON THE EFFECTS OF INTRACORONARY NICORANDIL AND NITROGLYCERIN IN ISCHEMIC, REPERFUSED PORCINE HEARTS

The direct cardioprotective properties of nitroglycerin and nicorandil were compared in regionally ischaemic (45 min), reperfused (24 h) por cine hearts. Intracoronary treatments, which were started 15 min prior to occlusion of the distal left anterior descending coronary artery ( LAD), were continuously administered for 105 min. The following equi-h ypotensive drug dosages were used in nine pigs each; nitroglycerin 6 m u g.kg(-1 x) min before ischaemia and during 45 min of reperfusion, 0. 6 mu g.kg(-1) min during ischaemia; nicorandil 5 mu g.kg(-1) x min bef ore ischaemia and during 45 min of reperfusion, and 0.5 mu g.kg(-1 x) min during ischaemia. Nine control animals were treated with isotonic sodium hydrochloride solution (1 ml.min(-1)). Despite comparable effec ts on blood pressure, intracoronary nicorandil, in contrast to intraco ronary nitroglycerin, did not increase heart rate. Although neither dr ug affected coronary blood flow significantly, nicorandil substantiall y reduced regional myocardial oxygen consumption before coronary arter y occlusion (-37+/-22%, P=0.003 vs control group, P=0.01 vs nitroglyce rin treatment). Infarct sizes (tetrazolium method) after 45 min of isc haemia and 24 h of reperfusion were significantly decreased by nicoran dil (control group 76.9+/-19%, nicorandil group 49.3+/-24%, P=0.012) w hereas nitroglycerin exhibited a borderline effect (62.5+/-15%, P=0.05 4). Both treatments resulted in improved regional systolic shortening of the reperfused segment at the end of the experiments but this was n ot significant. At these drug dosages the direct cardioprotective acti on of nicorandil is slightly superior to nitroglycerin. This may be as cribed to its K-channel opening property associated with reduced regio nal myocardial oxygen consumption before the onset of ischaemia.