Regression of left ventricular hypertrophy in two-kidney, one clip Goldblatt hypertension

The effect of regression of left ventricular hypertrophy (LVH) on ventricular performance was studied in two-kidney, one clip Goldblatt hypertensive rats (2K1C) treated with methyldopa or by unclipping. Sham operations were performed in a total of 21 rats; 12 and nine were studied after 4 and 6 weeks, respectively. Hypertension was induced in 38 additional rats. Of these, 11 were studied at 4 weeks. Cardiac index was measured by electromagnetic flowmetry under light ether anesthesia, and ventricular performance was assessed by rapid intravenous saline infusion. Of the remaining 27 hypertensive rats at 4 weeks postclipping, 10 were treated with methyldopa (400 mg/kg/day) and nine were unclipped; eight were left untreated as controls. Two weeks thereafter, ventricular performance was determined as described above. When expressed as the relationship between cardiac index and LV end-diastolic pressure, ventricular performance tended to be depressed in 2K1C. Ventricular performance, mean arterial pressure, and LV-to-body weight ratio returned to control in unclipped rats. Whereas methyldopa resulted in regressed LVH, its effect on mean arterial pressure and total peripheral resistance was not as marked as unclipping, both remaining significantly increased (p less than 0.001). The disparate effects of unclipping and methyldopa on systemic hemodynamics indicate that the improved ventricular performance with methyldopa was related more to its effect on LVH, suggesting that in these animals regression of LVH was associated with improved ventricular performance.