Recovery from cardiac bypass and elective cardiac arrest. The metabolic consequences of various cardioplegic procedures in the isolated rat heart.

Abstract

Isolated perfused working rat hearts were subjected to elective cardiac arrest for 20 or 30 minutes. Various methods of arrest, either singly or in combination and with or without coronary perfusion, were studied. The functional recovery of the heart following the termination of arrest was related to the concentration of adenosine triphosphate (ATP) and creatine phosphate in the myocardium at the end of the period of arrest. In turn, these concentrations depended on the method used to induce arrest. Normothermic ischemic arrest or electrical fibrillation led to a marked reduction in high-energy phosphates and a poor functional recovery. In contrast, coronary perfusion with hypothermic solutions or solutions containing high concentrations of potassium induced arrest without depleting ATP or creatine phosphate. These procedures conferred considerable protection on the myocardium and thus permitted good recovery. The energy status and the recovery associated with ischemic arrest were improved by combining the ischemia with potassium-induced arrest, intermittent coronary perfusion, or hypothermia. In the latter instance, a time- and temperature-dependent relationship was demonstrated. The results stress the importance of maintaining ATP and creatine phosphate levels during arrest; such maintenance requires the provision of a continuous supply of oxygen and nutrient, which may perhaps be best achieved by ensuring continuous and adequate coronary perfusion.