Abstract 1656: Adverse Effect of Early and Late Long-term Beta-blockade on Left Ventricular Remodeling, Function and Mortality in Chronic Organic Mitral Regurgitation
Background: Early prophylactic use of beta-blockers in the treatment of patients with chronic organic mitral regurgitation (MR) is controversial. We hypothesized that the effect of early and late long-term beta-blockade on left ventricular (LV) remodeling and function could be different in chronic organic MR.
Methods: Moderate to severe chronic organic MR was surgically induced in 68 rats, which were randomized into three groups: 1) non-beta-blockade (n=22), early (n=22) and late long-term beta-blockade (n=24) groups. Carvedilol was started at 2 weeks after the MR induction and administrated for 35 weeks in the early long-term beta-blockade group. In the late beta-blockade group, carvedilol was administrated at 24 weeks after the MR induction. LV end-systolic dimension (LVESD), end-systolic volume (LVESV) and fractional shortening (LVFS) were assessed by echocardiography at baseline and 1, 6, 12, 24 and 36 weeks.
Results: There were no differences in heart rate, LVESD and LVESV and LVFS among the three groups at baseline. However, heart rates were significantly lower in the beta-blockade groups. LVESD and LVESV were significantly larger and LVFS was significantly lower in the early and late long-term beta-blockade groups than that in the non-beta-blockade group (Table⇓, comparisons with the non-beta-blockade group, *p<0.05, **p<0.01). The all-cause mortality tended to be higher in the early long-term beta-blockade group.
Conclusion: Early and late beta-blockade showed no beneficial effect on LV remodeling and function in chronic organic MR. Depressed LV systolic function and increased mortality associated with the early long-term beta-blockade in chronic organic MR warrant further investigation.
This research has received full or partial funding support from the American Heart Association, National Center.