Effect of digitoxin on cardiac hypertrophy induced by pericardiectomy and exercise.

Removal of the pericardium in combination with a mild exercise programme of swimming resulted in a significant increase in heart weight and heart weight/body weight ratio of young rats. Heart weight/body weight ratios were 3.46+/-0.25 in the sedentary control animals, 4.16+/-0.26 in pericardiectomized animals swimming 2 h each day, and 4.60+/-0.22 in pericardiectomized animals swimming 6h/d. The effect of pericardiectomy on the development of cardiac hypertrophy is additive to that of mild exercise (2h/d) but not to prolonged exercise (6h/d). The administration of digitoxin significantly decreased the development of cardiac hypertrophy in pericardiectomized animals that were exercised for 2 h/d but not those exercised for 6 h/d. These findings further substantiate the physiological effect on the heart of the pericardium. The effects of pericardiectomy should be considered in experimental studies of cardiac hypertrophy and in clinical studies involving cardiac surgery.