Comparison of the metabolic response of the hypertrophic and the normal heart to hypothermic cardioplegia. The effect of temperature

The aim of this study was to test for metabolic differences in the response of hypertrophic and normal hearts to hypothermic cardioplegia. Hypertrophic dog hearts and normal control hearts were subjected to 6 hours of hypothermic cardioplegia with the St. Thomas' Hospital solution. Levels before arrest of subepicardial and subendocardial adenosine triphosphate, creatine phosphate, and lactate in eight hypertrophic hearts were the same as those levels in 12 normal hearts. In hypertrophic hearts, but not in normal hearts, the induction of arrest was slow and was associated with an 11% increase in adenosine triphosphate levels, a 59% decrease in creatine phosphate levels, and a 12-fold increase in lactate levels. Seven hypertrophic hearts and eight normal hearts were studied during 6 hours of arrest and showed no further differences in metabolic response. Reducing the myocardial temperature from 20 degrees C to 12 degrees C slowed the rate of depletion of adenosine triphosphate and the rate of accumulation of lactate in both groups. We conclude that in the nonfailing, severely hypertrophic heart, levels before arrest of high-energy phosphates and lactate are normal, but that marked biochemical changes may occur if the induction of arrest is prolonged because of underdosing with cardioplegic solution. Cooling from 20 degrees C to 12 degrees C improves myocardial preservation in both hypertrophic and normal hearts.