Age differences in effects of hypothermic ischemia on endothelial and ventricular function

Area of Science:

• Cardiovascular Physiology
• Neonatal Cardiology
• Ischemia-Reperfusion Injury

Background:

• Immature myocardium exhibits greater tolerance to ischemic events.
• Previous research links impaired endothelial function to reduced ventricular contractility post-ischemia.
• Coronary endothelium plays a significant role in ischemia and reperfusion injury in neonatal hearts.

Purpose of the Study:

• To investigate differences in endothelial and ventricular function between immature and mature hearts post-hypothermic cardioplegic ischemia.
• To assess the recovery of cardiac function and coronary blood flow in neonatal, infant, and adult hearts after ischemia.
• To determine the role of coronary endothelium in reperfusion injury across different age groups.

Main Methods:

• Isolated blood-perfused lamb and sheep hearts from three age groups (neonatal, infant, adult) were subjected to 2 hours of 15°C cardioplegic ischemia.
• Post-ischemic recovery of left ventricular systolic and diastolic functions and coronary blood flow was evaluated.
• Endothelial function was assessed by measuring the coronary vasodilator response to acetylcholine during reperfusion.

Main Results:

• Neonatal and infant hearts demonstrated significantly improved recovery of left ventricular systolic and diastolic functions and coronary blood flow at 30 minutes of reperfusion.
• Post-ischemic endothelial function, assessed via acetylcholine response, was superior in neonatal and infant hearts compared to adult hearts (p < 0.05).

Conclusions:

• Immature hearts exhibit enhanced recovery of endothelial function, coronary blood flow, and ventricular function following hypothermic ischemia and reperfusion compared to adult hearts.
• These findings support the concept that the coronary vascular bed is crucial in mitigating reperfusion injury in both immature and mature hearts.