Intraoperative changes in coronary resistance during aortic valve replacement.

Area of Science:

• Cardiovascular Surgery
• Cardiac Anesthesia
• Vascular Physiology

Background:

• Aortic valve replacement necessitates managing myocardial protection during aortic cross-clamping.
• Coronary perfusion strategies aim to maintain adequate blood flow to the myocardium.
• Understanding coronary vascular resistance (CVR) dynamics post-ischemia is vital for optimizing perfusion protocols.

Purpose of the Study:

• To investigate the impact of varying anoxic durations on coronary vascular resistance following aortic valve replacement.
• To determine the optimal timing for initiating coronary perfusion to minimize adverse effects on myocardial blood flow.

Main Methods:

• Continuous constant-pressure coronary perfusion at 32°C was employed in 10 patients undergoing aortic valve replacement.
• Coronary vascular resistance was measured after initiating coronary flow.
• The influence of short, moderate, and long anoxic periods preceding reperfusion on CVR was assessed.

Main Results:

• Coronary vascular resistance was initially low, increasing to a plateau post-perfusion.
• The time to reach the resistance plateau was shorter after shorter anoxic periods.
• Initial post-ischemic resistance was significantly higher after prolonged anoxia, persisting throughout perfusion.
• Total coronary resistance tripled, while flow halved within 30 minutes of reperfusion.

Conclusions:

• Initiating coronary perfusion promptly after aortic cross-clamping is essential.
• Delayed perfusion significantly increases initial coronary vascular resistance.
• Early reperfusion mitigates prolonged increases in vascular resistance and ensures adequate myocardial flow.