Decreased postoperative myocardial fatty acid oxidation.

Area of Science:

• Cardiology
• Metabolic Research
• Surgical Science

Background:

• Myocardial substrate utilization after cardioplegic arrest for coronary bypass surgery is not well understood.
• Elevated post-arrest arterial fatty acid levels suggest potential for myocardial uptake and reperfusion injury.
• Fatty acid accumulation without oxidation may be detrimental to the heart.

Purpose of the Study:

• To evaluate perioperative fatty acid metabolism in patients undergoing coronary bypass surgery.
• To compare myocardial substrate preferences following blood versus crystalloid cardioplegia.
• To investigate the heart's ability to extract and oxidize fatty acids after cardioplegic arrest.

Main Methods:

• 18 patients undergoing elective coronary bypass surgery were randomized to blood or crystalloid cardioplegia.
• 14C-labeled palmitate was infused, and arterial/coronary sinus samples were analyzed.
• Myocardial extraction and oxidation of fatty acids were calculated pre- and post-arrest.

Main Results:

• Both cardioplegia types induced myocardial release of lactate and glycerol, indicating glycolysis and lipolysis.
• Myocardial oxygen consumption and substrate utilization (lactate, glucose, fatty acids) were minimal post-arrest.
• Fatty acid oxidation was minimal with blood cardioplegia and undetectable with crystalloid cardioplegia.
• The heart extracted fatty acids but did not metabolize them aerobically post-arrest.

Conclusions:

• The heart's capacity to oxidize exogenous fatty acids is significantly impaired after cardioplegic arrest.
• Altered myocardial substrate preferences may occur during reperfusion following coronary bypass surgery.
• Fatty acid accumulation without oxidation post-arrest could be deleterious, potentially contributing to reperfusion injury.