Hydralazine treatment in hypertensive rats reduced left ventricular weight by 17% (P<0.001) compared to untreated rats, but collagen volume fraction remained elevated at 9.9%.
Absolute Event Rate: 9.9% vs 13.7%
p-value: p=<.01
To determine if a remodeling of the collagen matrix would occur in the absence of hypertrophy and cell necrosis and if such a remodeling could alter active and passive stiffness of the intact myocardium, five rats with genetic hypertension (SHR) were treated (SHRT) with hydralazine for 32 weeks, beginning at four weeks of age, and compared to six age- and sex-matched SHR and seven Wistar-Kyoto genetic control rats (WKY). Left ventricular (LV) weight of SHRT was 17% lower (P less than .001) than that of SHR and 19% higher (P less than .01) than that of WKY. Collagen volume fraction of SHR (13.7 +/- 3.2%) and SHRT (9.9 +/- 1.8%) were greater (P less than .01) than WKY (5.0 +/- 1.9%). Diastolic and systolic stress-strain relations were determined in the isolated heart. A comparison of these relations revealed: 1) a 24% increase in passive stiffness for SHR and SHRT; and 2) a reduced zero-strain intercept (41% to 54%) and slope (36% to 48%) of the developed stress-strain relation for the SHRT. Thus, in SHR, collagen remodeling occurred in the absence of hypertrophy which suggests that the muscular and collagenous compartments of the myocardium are under separate controls. The excess accumulation of collagen in SHR and SHRT leads to abnormal passive stiffness, and the prevention of hypertrophy with hydralazine reduces active stiffness.
Narayan et al. (Fri,) conducted a other in Genetic hypertension (n=18). Hydralazine vs. Untreated SHR and WKY rats was evaluated on Collagen volume fraction (p=<.01). Hydralazine treatment in hypertensive rats reduced left ventricular weight by 17% (P<0.001) compared to untreated rats, but collagen volume fraction remained elevated at 9.9%.