Coronary blood flow during the development and regression of left ventricular hypertrophy in renovascular hypertensive rats

Left ventricular (LV) coronary flow (CF) was determined by left atrial injection of microspheres in conscious rats during the development and after the reversal of LV hypertrophy in 2-kidney, 1-clip Goldblatt hypertension. Two groups of untreated renal hypertensive rats (RHR) were studied, the first (RHR1, n = 17) at 10 weeks and the second (RHR2, n = 9) at 24 weeks after clipping. Beginning 9 weeks after clipping, 2 other groups were treated either with captopril (40 to 60 mg/kg/day) in drinking water (RHR-C, n = 8) or left nephrectomy (RHR-N, n = 9) and followed for 15 weeks. Sham-operated animals followed for similar periods of time served as controls (Sham-1, n = 12, as a control for RHR1, and Sham-2, n = 11, as a control for RHR2). In all groups, LV mass increased or decreased in close correlation with changes in arterial blood pressure, and minimal total LV coronary resistance remained unchanged. The development of hypertrophy was associated with a tendency toward reduction in CF reserve (defined as maximal CF/unit mass); this flow reserve was restored with reversal of hypertrophy. The importance of the relation between pressure and LV mass as a determinant of CF reserve was investigated in a second study in which this relation was changed by altering the periods of captopril therapy; in these cases, CF reserve correlated significantly with the ratio of arterial pressure to LV mass (r = 0.76, n = 12, p less than 0.01). The results suggest that maintenance of CF reserve in LV hypertrophy depends on an appropriate balance between arterial pressure and LV mass, and might be disturbed by antihypertensive therapy that leaves LV hypertrophy unchanged.