Change in Systolic Loading Sequences Produced the Different Remodeling of Hypertrophic Left Ventricle in Rats

To study the effect of a change in systolic loading sequence on a development of LV hypertrophy due to pressure-overload, early systolic loading was produced by the coarctation of ascending aorta (ASC:n= 9) , and late systolic loading by the coarctation of abdominal aorta(ABD: n=8) in 6-week-old rats. Four weeks after operation, LV wt (ing)/ body wt(g) ratio increased both in ASC(2.4±0.1, p<.05) and in ABD (2.7±0.2, p<.05) compared with sham-operated group (Sham:n=9, 2.0±0.1). Peak LV pressure increased both in ASC and ABD (ASC:197±10 vs ABD:203±11mmHg, ns). We also measured LV wall thickness (W) and LV internal diameter (D) with sonomicrometry (20 MHz) , and W/D ratio was calculated as an index of eccentricity. In ASC, W/D ratio decreased compared with Sham(ASC: 0.6±0.1 vs Sham:1.1±0.2, p<.05) , indicating a development of eccentric LV hypertrophy, whereas no difference of W/D ratio was found between Sham and ABD. Collagen volume fraction (CVF: by image analyzer) in subendocardial region was higher in ABD (6.2±0.6 %) than in ASC(5.2±0.5 %, p<.05) with no significant difference in subepicardial CVF. Myocyte diameter was also larger in ABD (16.1±1.2 /μm) than in ASC(14.5±0.6 jum, p<.05). The levels of plasma angiotensin II and aldosterone at both 10 days and 4 weeks after surgery were not different among 3 groups. Our data demonstrate that different pressure-loading sequences during ventricular ejection might be an important mechanical factor for determining the type of remodeling in hypertrophic left ventricle.

左室駆出期 loading sepuence

高血圧

左室肥大

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