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The effect of Beta Blockers in Dogs with SAS | VetGirl Veterinary CE Podcasts

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In this VETgirl podcast, we review subaortic stenosis (SAS) in dogs, and whether or not the affect of certain cardiac medications (e.g., specifically beta-blockers) affect the overall survival. Subaortic stenosis, more commonly causes SAS, is a common congenital cardiac condition in dogs; it is characterized by a fibrous ring/ridge of tissue below the aortic valve, causing narrowing of this region and secondary pressure overload to the left ventricle. The severity of SAS is determined by the left ventricular-to-aorta pressure gradient (PG), with severe pressure gradients considered to be ≥ 80 mm Hg. In general, the prognosis for mild to moderate SAS is generally considered significantly better than for severe SAS with minimal treatment initiated for the former group. In cases with severe SAS, prior data is limited to a single, small study that reported a 19 month median survival.1,2 As a result, the overall long-term prognosis for severe SAS has been considered to be poor. Treatment of severe SAS has been limited to:

  • Medical therapy (including cardiac medications like beta-blockers). The goal of beta-blocker therapy is to slow the heart rate and force of contraction, thus reducing overall myocardial workload and stress.
  • Miscellaneous therapy (including non-cutting balloon valvuloplasty). Unfortunately, balloon valvuloplasty has showed no difference in survival times compared with beta blocker therapy alone.

In this podcast, we review the recent findings of a study by Eason et al, where they retrospectively evaluated 50 dogs with severe SAS. Approximately half the group (n=27) received beta-blocker therapy (with a median dose of 0.55 mg/kg PO BID), while the remaining group acted as the control group (and were untreated). Overall, what they found was that beta-blocker therapy did not appear to improve survival in dogs with severe SAS. This study did find that dogs with lower pressure gradients had a markedly improved median survival time (8.3 years as compared to 2.8 years).

There were some significant limitations of this study, as the group size was small (n=50), and it was retrospective in nature. That said, while this study didn’t find any difference between beta-blocker treated groups versus control groups, they found some good news: the overall median survival times in both groups are significantly longer than those previously reported. So, don’t give up on those severe SAS dogs yet – no need for a beta-blocker necessarily, but don’t euthanize them right away, as they can survive longer than previously suspected. The identification of a significant difference in survival at a pressure gradient cutoff of 133 mm Hg may carry highly useful prognostic importance and warrant reclassification of what is generally considered to be severe (> 80 mm Hg) SAS in dogs.

Errata:

In the podcast, we say “Overall, what they found contradicted previous studies: beta-blocker therapy did not appear to improve survival in dogs with severe SAS.” This should have been read as “Overall, what they found was that beta-blocker therapy did not appear to improve survival in dogs with severe SAS.”

References:

1. Kienle RD, Thomas WP, Pion PD. The natural clinical history of canine congenital subaortic stenosis. J Vet Int Med 1994;8(6):423-31.

2. Meurs KM, Lehmkuhl LB, Bonagura JD. Survival times in dogs with severe subvalvular aortic stenosis treated with balloon valvuloplasty or atenolol. J Am Vet Med Assoc 2005;227(3):420–4.

1. Eason BD, Fine DM, Leeder D, et al. Influence of Beta Blockers on Survival in Dogs with Severe Subaortic Stenosis. J Vet Int Med 2014;28(3):857-862.

 

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