December 17, 2015Open Access

Atrial Fibrillation as a Prognostic Indicator in Medium to Large‐Sized Dogs with Myxomatous Mitral Valvular Degeneration and Congestive Heart Failure

SJSeungWoo JungAuburn University WSWei SunThird Affiliated Hospital of Southern Medical University LGLeigh G. GriffithsMayo Clinic

Key Result

Atrial fibrillation in dogs with myxomatous mitral valvular degeneration and CHF is associated with a median survival time of 142 days, compared to 234 days without AF (HR 2.544).

Structured PICO

Does atrial fibrillation worsen survival in medium to large-sized dogs with myxomatous mitral valvular degeneration and congestive heart failure?

Population

64 client-owned medium to large-sized dogs (>15 kg) with myxomatous mitral valvular degeneration (MMVD) and congestive heart failure (CHF). Median age 11 years, 38 male/26 female. Median body weight 24 kg.

Intervention

Presence of atrial fibrillation (AF) (n=33) and subsequent rate control strategies (diltiazem alone or diltiazem plus digoxin)

Comparator

Dogs without atrial fibrillation (n=31) (for prognostic impact); inadequate rate control or diltiazem alone (for treatment impact)

Outcome

Cardiac-related death (composite of death that resulted from sudden death or euthanasia related with worsening or refractory CHF)hard clinical

In medium to large-sized dogs with MMVD and CHF, the development of atrial fibrillation significantly worsens survival, though adequate rate control (<160 bpm) with combination therapy may prolong survival.

Main Result

Absolute Event Rate: 0% vs 0%

Abstract

Background The prevalence and prognostic importance of atrial fibrillation ( AF ) on survival in nonsmall breed dogs with myxomatous mitral valvular disease ( MMVD ) and congestive heart failure ( CHF ) remain unknown. Aim To identify the prevalence of AF in nonsmall breed dogs with CHF because of MMVD and to characterize the impact of AF on survival outcome. Animal Sixty‐four client‐owned dogs (>15 kg) with MMVD and CHF . Methods Retrospective review of medical records for dogs weighing >15 kg with MMVD treated for CHF . Results Thirty‐three dogs presented with AF or developed AF during follow‐up examinations, and 31 dogs were free of AF until cardiac‐related death. For dogs with AF , median survival time ( MST ) was 142 days (range: 9–478) while dogs without AF lived 234 days (range: 13–879 days). AF increased risk of cardiac‐related death ( HR = 2.544; 95% CI = 1.41–4.59; P = .0019) when compared to dogs without AF . MST was significantly prolonged for dogs with AF whose rates were adequately controlled (<160 bpm; 171 days; n = 13) when compared to dogs that failed to respond to negative chronotropic agents (61 days; n = 20; P = .032). The administration of combination treatment (diltiazem and digoxin) significantly decreased median HR to 144 bpm (range: 84–218 bpm) in dogs with AF and significantly prolonged MST (diltiazem+digoxin: 130 days versus diltiazem: 35 days, P = .0241) when compared to diltiazem alone. Conclusions and Clinical Importance Inadequately controlled AF is associated with a higher rate of mortality. Optimization of therapeutic strategies for the rate control of AF remains determined.

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