Effects on infarct size and on arrhythmias by controlling reflow after myocardial ischaemia in pigs

Part of the myocardial damage after an ischaemic period might be related to the reperfusion conditions. Many abrupt changes occurring in the heart dur ing reperfusion may add to the damage during the preceding ischaemic period , and increase in infarct size. In this study we tested the hypothesis that infarct size and occurrence of ventricular arrhythmias might be reduced by restricting reflow after an ischaemic period. Seventeen pigs underwent 45 min of total occlusion of the left anterior descending coronary artery with an hydraulic occluder. In the intervention group reperfusion was restricte d to 50% of baseline during the first minute, to 100% during the next minut e, kept constant for 1 min, and thereafter allowed to increase by 50% of ba seline flow every minute until free reflow. In the control group reflow was not restricted. Arrhythmias were recorded. After 2.5 h of reperfusion the heart was excised. Infarct size was measured by using triphenyltetrazolium chloride (delineation of necrosis), fluorescent microspheres (delineation o f area at risk) and planimetry. No reduction in infarct size (% of area at risk) was found between the intervention group and the control group (75.9 +/- 5.3% vs. 72.4 +/- 4.3%). The incidence of ventricular arrhythmias and v entricular fibrillation were not found to be different between the groups d uring reperfusion. Hemodynamic parameters were not significantly different between the two groups. Our data indicate that no substantial protection ag ainst myocardial infarct or ventricular arrhythmias could be achieved by co ntrolling reflow using the present protocol after a period of myocardial is chaemia in pigs. Accordingly, our data do not support the notion that contr ol of reflow may be beneficial when treating coronary artery occlusion with percutaneous coronary angioplasty (PCA).