Different responses in adult and neonatal hearts to changes in coronary perfusion pressure.

The influence of coronary perfusion pressure on neonatal heart function has not been evaluated. We compared the coronary perfusion pressure–cardiac function relationship between neonatal and adult hearts. Neonatal and adult rabbit hearts were examined. The coronary perfusion pressure was changed in increments of 10 mmHg. Coronary blood flow and left ventricular functions were measured at each coronary perfusion pressure. Autoregulatory capacity for coronary blood flow was quantified by calculating the autoregulation index. In neonatal hearts, left ventricular developed pressure was decreased at high perfusion pressure, whereas in adult hearts left ventricular developed pressure increased at high perfusion pressure. In neonatal hearts, left ventricular enddiastolic pressure was elevated at both low and high perfusion pressure, whereas in adult hearts left ventricular enddiastolic pressure remained constant at all perfusion pressures. Adult hearts exhibited coronary blood flow autoregulation in the perfusion pressure range between 40 and 90 mmHg. In contrast, neonatal hearts did not show autoregulation in any perfusion pressure range. In neonatal hearts, both low and high perfusion pressure caused deterioration in ventricular function attributable to the immaturity of coronary autoregulatory capacity. We conclude that coronary perfusion pressure should be controlled within a narrow range for neonates.