Hydrochlorothiazide improves ventricular compliance and thus performance without reducing hypertrophy in renal artery stenosis in rats

The effect of hydrochlorothiazide (1 mg/kg per day) on left ventricular (LV) mass and systolic and diastolic function was investigated in two- kidney, one clip (2K1C) renovascular hypertensive rats. Hydrochlorothiazide was administered from 8 weeks, and LV mass and function were measured at 16 weeks after surgery to induce hypertension. Cardiac performance was determined from cardiac output, stroke volume (per 100 g of body weight), and stroke work (per gram of LV weight) versus LV end-diastolic pressure (LVEDP) and versus LV strain relations in anesthetized open-chest, ventilated rats. LV compliance was determined from the LVEDP versus strain relation. Strain was calculated from LV end-diastolic short-axis diameter values. Hydrochlorothiazide reduced systolic blood pressure in 2K1C rats to levels similar to those in sham-operated controls (sham) at 12 weeks after surgery. A reduced afterload failed to influence LV mass, as left LV hypertrophy developed to the same extent in treated 2K1C rats. 2K1C hypertension produced abnormal cardiac performance with altered cardiac output, stroke volume, and stroke work versus LVEDP relations (stroke work versus LVEDP, intercept of 2K1C versus sham, p<0.001). This was attributed to a decreased ventricular compliance (strain versus LVEDP, slope of 2K1C versus sham, p<0.001). In contrast, hydrochlorothiazide improved ventricular compliance (strain versus LVEDP, slope of 2K1C versus 2K1C hydrochlorothiazide, p<0.01) and thus returned the stroke work versus LVEDP relation to sham values (intercept of 2K1C versus 2K1C hydrochlorothiazide, p<0.001). We conclude that hydrochlorothiazide reduces blood pressure but not the development of ventricular hypertrophy in 2K1C rats. Although a reduced blood pressure did not produce regression of ventricular hypertrophy, it was associated with an improved ventricular compliance and thus performance. This study underscores the value of equating changes in ventricular hypertrophy with changes in cardiac function when the value of antihypertensive agents is being assessed.