[Myocardial remodeling in chronic pressure or volume overload in the rat heart].

OBJECTIVE To compare cardiac structural changes in experimental pressure and volume overload models. METHODS The study analysis included renovascular hypertensive rats (RVH, n = 8), normotensive rats with volume overload caused by an aortocaval fistula (ACF, n = 10) and control rats (CONT, n = 8). After four weeks, tail cuff blood pressure (SBP) was recorded. Rats were killed, the hearts were excised and the right and left ventricles (RV&LV) were weighed (RVW&LVW). Using histological sections, myocyte cross sectional areas (MA). LV wall thickness (LVWT) LV cavity diameter (LVD), normalized LVWT (LVWT/LVD) and collagen volume fraction (CVF) were measured. The comparisons were made using the ANOVA and Tukey test for a significance level of 5%. RESULTS Tail cuff blood pressure (mmHg) was higher in the RVH group (RVH = 187 +/- 22; CONT = 125 +/- 10; ACF = 122 +/- 6, p < 0.05). LV hypertrophy was observed in the RVH and ACF groups. The ACF group presented a significant increase in size of LVD, compared to CONT and RVH. The absolute and normalized ventricular wall thickness were similar among the groups. The RVH group presented a significant increase in CVF compared to CONT group and ACF group. CONCLUSION Cardiac remodeling patterns following volume or pressure overload are distinct, suggesting that their implications on ventricular dysfunction are not interchangeable.