Impact of Beta Blockade on Prognosis in Patients With Chronic Severe Degenerative Mitral Regurgitation

Background: The impact of chronic beta blockade (BB) on cardiac events (CE) in patients (pts) with chronic severe mitral regurgitation (MR) has not been studied by randomized trials but is inferred as beneficial from observational data. However a recent randomized preclinical study demonstrated increased mortality with BB in MR. Methods: We retrospectively analyzed 45 consecutive study-eligible pts (age 49±12 yrs, 69% male) with isolated chronic severe non-ischemic MR without concomitant coronary disease, followed through 19 yrs, to assess impact of chronic BB use at entry on CE (death or indications for valve surgery). At entry, all pts were non-hypertensive (HTN) and free of surgical indications; 9 pts chronically received BB at entry (of whom 7 continued receiving BB throughout the study period). CE rate differences were assessed by Kaplan-Meier log rank comparison; 6 pts on non-selective BBs were analyzed separately on an exploratory basis. Cox model analysis was used to adjust for variations in other baseline covariates (age, gender, etiology, other cardiac drugs). Results: During follow-up, CE included: sudden death (1), heart failure (8), a-fib (6), left ventricular (LV) dimensions (IDs)>4.5cm (11), LV ejection fraction (EF)<60% (6), right ventricular (RV) EF<35% (2), combination CE (7). CE risk was 2-fold higher among pts receiving BB (Avg annual risk [AAR]= 15.28%) vs. those not receiving BB (AAR= 33.04%) (p<.05) (Figure). A > 3-fold relative CE risk was observed when pts on selective BB were excluded (AAR: BB vs no BB = 56.18% vs. 15.28%, p=.01). BB effects remained statistically significant (p<.05) when analyses were adjusted for other baseline covariates. Conclusions: Contrary to earlier observational data, in our series BB appears to increase CE risk in pts without HTN. Further research including larger numbers of MR pts, preferably via randomized design, is needed to clarify the discrepancy between the different findings among existing studies.