The effect of hypothermic ischemia on recovery of left ventricular function and preload reserve in the neonatal heart

Neonatal and adult myocardium respond differently to ischemia. In addition, the neonatal heart possesses a limited preload reserve. The effect of uninterrupted hypothermic ischemia on recovery of left ventricular function and preload reserve was studied in two groups of isolated rabbit hearts: group 1 (neonates, n = 8), 7 to 10 days old; group 2 (adults, n = 15), 6 to 12 months old. Peak left ventricular systolic pressure, the first derivative of left ventricular systolic pressure, and heart rate were measured at left ventricular pressures of 0, 5, 10, and 15 mm Hg before and after 120 minutes of global ischemia at 27° C. Before ischemia, left ventricular systolic pressure increased significantly at each increment of left ventricular end-diastolic pressure for both groups of hearts. After hypothermic ischemia, recovery of left ventricular systolic pressure was significantly reduced at each level of left ventricular end-diastolic pressure among neonatal hearts (range 75% to 79% of control values). The postischemic recovery of left ventricular systolic pressure in the adult hearts was markedly reduced from baseline values (range 43% to 53% of control values) and was significantly worse than that of neonatal hearts at each level of left ventricular end-diastolic pressure (p