The reversal of left ventricular hypertrophy with control of blood pressure in experimental hypertension
The precise mechanisms of hypertensive left ventricular hypertrophy and reversal with antihypertensive drugs are unclear and complex. Enalapril maleate (MK421) and hydrochlorothiazide (HTZ) were used to assess the control of hypertension, and reversal of left ventricular hypertrophy in Dahl sensitive (DS) and Dahl resistant (DR) rats given either a high (8% NaCl), or a low (0.4% NaCl) salt diet. Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), left ventricular weight/body weight (LVwt/Bwt) ratio were determined. Both drugs were effective in reducing blood pressure and left ventricular mass in DS rats placed on a high salt diet. For DR rats under the same conditions, only MK421 induced significant lowering of blood pressure. Neither drug caused significant change in ventricular mass. Both DS and DR rats on a low salt diet underwent significant blood pressure reduction with MK421 but not HTZ. Significant regression of the left ventricle was observed only in DS rats treated with MK421. Regression was not observed in DR rats even though MK421 reduced blood pressure to distinctly hypotensive levels. The dissociation of left ventricular mass and blood pressure control observed with both MK421 and HTZ suggests that pressure afterload is not the only factor involved in the pathophysiology of hypertensive cardiac hypertrophy. The mechanisms of anti-hypertensive drug action and salt intake both appear to play a significant if unexplained role.