Pump performance after regression of cardiac hypertrophy following treatment of hypertension with isradipine.

In view of the possibility that cardiac hypertrophy may be reversed by isradipine, we studied the effect of two different doses of isradipine (1.0 and 7.0 mg/kg per day) on relative cardiac weight in the rat. These doses have proved equipotent in lowering the blood pressure of the two-kidney, one clip model of hypertension. Untreated hypertensive rats had significantly greater cardiac weights than the untreated controls (3.16 +/- 0.06 versus 2.31 +/- 0.05 mg/g, P less than 0.001). Hypertrophy was still present in the group treated with isradipine at 1.0 mg/kg per day (3.17 +/- 0.07 versus 2.30 +/- 0.03 mg/g; P less than 0.001) but not with 7.0 mg/kg per day (2.55 +/- 0.17 versus 2.37 +/- 0.11 mg/g; NS). Functional studies revealed that reversal of cardiac hypertrophy did not affect cardiac performance compared with the ventricles with increased mass. These results suggest that reversal of left ventricular hypertrophy with isradipine is dependent on complex mechanisms, possibly unrelated to the unloading of the heart.