Favorable effects of therapy on cardiac performance in spontaneously hypertensive rats.

To determine whether chronic antihypertensive therapy reduces cardiac mass and improves performance in spontaneously hypertensive rats (SHR) with marked left ventricular hypertrophy and evidence of cardiac dysfunction, 12-mo-old male and female SHR and age- and sex-matched normotensive rats (NORM) were treated for 6 mo with either tap water or tap water containing hydralazine or guanethidine. Cardiac performance was assessed by the peak stroke volume and cardiac indices attained during volume loading and by the maximum left ventricular pressure developed during an aortic occlusion. Passive diastolic pressure-volume curves were obtained in the potassium-arrested heart. Treatment prevented the progression of left ventricular hypertrophy in SHR and the marked deterioration in peak pumping ability observed in untreated male SHR and the modest impairment observed in female SHR. The peak developed pressure of both the male and female treated SHR was reduced toward that of NORM and was associated with a reduction in the left ventricular mass-to-volume ratio toward that of NORM. Thus chronic therapy with either hydralazine or guanethidine reduced cardiac mass and prevented the deterioration in cardiac pumping performance observed in SHR with sustained hypertension and marked cardiac hypertrophy.