Cardiac dysfunction and inefficiency after substrate-enriched warm blood cardioplegia.

Area of Science:

• Cardiovascular Physiology
• Cardiac Surgery
• Myocardial Protection

Background:

• Warm continuous antegrade blood cardioplegia (WCBC) is used in cardiac surgery.
• Substrate enrichment aims to improve myocardial protection during cardioplegia.
• Understanding the impact of prolonged WCBC on cardiac function is crucial.

Purpose of the Study:

• To assess the mechanical performance and mechanoenergetic efficiency after prolonged WCBC with substrate enrichment.
• To compare the effects of WCBC alone, WCBC with glucose-insulin-potassium (GIK), and WCBC with L-glutamine (GLN).

Main Methods:

• Three groups of pigs (n=7 each) received 3 hours of WCBC: alone, +GIK, or +GLN.
• Cardiac function (systolic/diastolic), pressure-volume area (PVA), and myocardial oxygen consumption (MVO(2)) were measured.
• Measurements were taken before and twice after WCBC using advanced hemodynamic monitoring.

Main Results:

• All groups showed significant decreases in left ventricular developed pressure, dP/dt(max), and preload recruitable stroke work post-WCBC.
• Mechanoenergetic efficiency (PVA/MVO(2)) significantly decreased in all groups.
• End-diastolic stiffness increased in WCBC and +GLN groups, but not in the +GIK group.

Conclusions:

• Prolonged WCBC, even with substrate enrichment, severely impairs cardiac contractile function and mechanoenergetic efficiency.
• Sustained normothermic hyperkalemic perfusion carries significant risks for myocardial performance.
• The glucose-insulin-potassium (GIK) substrate may offer some protection against increased end-diastolic stiffness.