Coronary venous retroinfusion of felodipine reducing infarct size without affecting regional myocardial blood flow

Effects on the ischaemic and reperfused myocardium of felodipine, a vasoselective calcium blocker, retrogradely infused into the coronary vein was investigated in a porcine model. Sixteen open-chest pigs underwent 45 min of myocardial ischaemia by occlusion of the left anterior descending coronary artery followed by 4 h of reperfusion. Either felodipine (felo-retro group, 7 nmol.kg-1: n = 6) or the corresponding amount of vehicle (vehicle group: n = 5) was retroinfused over 30 min starting 5 min prior to reperfusion. In a third group, the same amount of felodipine was administered intravenously (felo-i.v. group n = 5). Myocardial regional blood flow was measured with radioactive microspheres prior to ischaemia and at different times of reperfusion. Infarction size, expressed as a percentage of the area at risk, was significantly reduced to 62 +/- 12% in the felo-retro group as compared to 86 +/- 12% (P < 0.05) and 94 +/- 5% (P < 0.05) in the vehicle and felo-i.v. group, respectively. Following an early hyperaemia, the regional blood flow decreased uniformly in the reperfused myocardium in all three groups and there were no significant differences between the groups at any period of reperfusion. In conclusion, felodipine retroinfused into the coronary vein could salvage ischaemic and reperfused myocardium without affecting the regional blood flow. The mechanism of this protective effect should be explained by factors other than an increased myocardial blood flow during reperfusion.