Influence of beta blockers on survival in dogs with severe subaortic stenosis

Background: Subaortic stenosis (SAS) is one of the most common congenital cardiac defects in dogs. Severe SAS frequently is treated with a beta adrenergic receptor blocker (beta blocker), but this approach largely is empirical. Objective: To determine the influence of beta blocker treatment on survival time in dogs with severe SAS. Methods: Retrospective review of medical records of dogs diagnosed with severe, uncomplicated SAS (pressure gradient [PG] ≥80mmHg) between 1999 and 2011. Results: Fifty dogs met the inclusion criteria. Twenty-seven dogs were treated with a beta blocker and 23 received no treatment. Median age at diagnosis was significantly greater in the untreated group (1.2 versus 0.6years, respectively; P=.03). Median PG at diagnosis did not differ between the treated and untreated groups (127 versus 121mmHg, respectively; P=.2). Cox proportional hazards regression was used to identify the influence of PG at diagnosis, age at diagnosis, and beta blocker treatment on survival. In the all-cause multivariate mortality analysis, only age at diagnosis (P=.02) and PG at diagnosis (P=.03) affected survival time. In the cardiac mortality analysis, only PG influenced survival time (P=.03). Treatment with a beta blocker did not influence survival time in either the all-cause (P=.93) or cardiac-cause (P=.97) mortality analyses. Conclusions: Beta blocker treatment did not influence survival in dogs with severe SAS in our study, and a higher PG at diagnosis was associated with increased risk of death.