Should ventricular fibrillation be induced prior to the infusion of cardioplegic solution?

The present study evaluates the metabolic effects on the left ventricular energy stores of a clinically used cardioplegic solution that was infused into the ascending aorta of pigs while the heart was either fibrillating (induced ventricular fibrillation) or in normal sinus rhythm prior to aortic clamping. Fibrillating hearts had lower stores of glycogen in the epicardium and endocardium compared with hearts in normal sinus rhythm. There was no difference in the stores of creatine phosphate between the hearts for both the epicardium and endocardium, but stores of adenosine triphosphate (ATP) in both layers were lower in fibrillating hearts. These results indicate that for ideal myocardial protection the cardioplegic solution should be infused while the heart is beating under cardiopulmonary bypass, and that ventricular fibrillation induced and maintained prior to cross-clamping may cause myocardial damage.