Effect of prolonged postischemic perfusion on neonatal hearts

Recent research on myocardial preservation has emphasized the importance of events occurring early in the reperfusion period, which may be of less importance to myocardial outcome in the neonate. We therefore wished to study the contribution of prolonged postischemic perfusion. This situation may occur during repair of congenital heart defects when in an attempt to reduce the period of aortic cross-clamp, the surgeon completes right-sided repairs on a beating empty heart. We used an isolated working rabbit heart model to compare recovery after various periods of ischemia and postischemic perfusion. After 30 min in the working heart mode, hemodynamic measurements were made. The hearts were then rendered globally ischemic, with the exception of cardioplegia. At the conclusion of the ischemic period, the hearts were returned to the 37 degrees C chamber, and reperfused with buffer. After 30 or 60 min retrograde perfusion, the hearts were converted to the working mode again. The working heart period continued until the heart was no longer able to overcome its afterload ("pump failure"). We recorded the time to this point as survival time. Hearts were divided into four groups: Group I (n = 12), 60 min ischemia, 30 min nonworking perfusion; Group II (n = 11), 90 min ischemia, 30 min nonworking perfusion; Group III (n = 8), 60 min ischemia, 60 min nonworking perfusion; and Group IV (n = 11), 0 min ischemia, 130 min nonworking perfusion. Multivariate analysis showed that four factors influenced survival time: aortic flow, age, left ventricular end-diastolic pressure, and mean aortic pressure. Group II did not vary significantly from Group I.(ABSTRACT TRUNCATED AT 250 WORDS)