TEMPORARY LEUKOCYTE DEPLETION REDUCES VENTRICULAR DYSFUNCTION DURING PROLONGED POSTISCHEMIC REPERFUSION

Leukocyte depletion improves early postischemic ventricular performanc e in neonatal models of global myocardial ischemia. However, the rate of leukocyte reaccumulation after cardiopulmonary bypass and its subse quent impact on myocardial function is not known. This laboratory stud y examined the effect of leukocyte depletion on myocardial performance during the initial 6-hour period after bypass in an in situ, in vivo porcine model of neonatal cardiac surgery. Fifteen 3- to 5-day-old pig lets (eight control and seven leukocyte depleted animals) were instrum ented by placement of left ventricular short-axis sonomicrometry cryst als and an intraventricular micromanometer catheter. Mechanical leukoc yte depletion was achieved with Pall RC100 filters (Pall Biomedical, I nc., Fajardo, Puerto Rico) in the cardiopulmonary bypass circuit. Neon atal hearts were subjected to 90 minutes of hypothermic ischemia after a single dose of cold crystalloid cardioplegia. Two control animals d ied after the operation and were excluded from data analysis. Leukocyt e filtration reduced the granulocyte count during initial myocardial r eperfusion to 0.8% of control values. However, circulating granulocyte counts increased in leukocyte depleted animals throughout the postope rative period, reaching 68% of control values by 6 hours. Despite this rapid return of circulating granulocytes, animals subjected to leukoc yte depletion had significantly better preservation of left ventricula r performance (measured by preload recruitable stroke work, p less-tha n-or-equal-to 0.02 left ventricular systolic function (measured by end -systolic pressure-volume relationship, p less-than-or-equal-to 0.05), and ventricular compliance (p less-than-or-equal-to 0.04) during the experiment. These changes in ventricular function were associated with a significant increase in left ventricular water content (p less-than -or-equal-to 0.02) and tissue myeloperoxidase activity (p less-than-or -equal-to 0.005) in control animals compared with leukocyte depleted a nimals. This study demonstrates that leukocyte depletion during initia l reperfusion results in sustained improvement in postischemic left ve ntricular function despite the rapid return of granulocytes to the cir culation.