Boxers fainting from slow heart rate despite fast heart rhythm

Abstract

BACKGROUND: Syncope is a recognized problem in Boxers and often is the result of rapid ventricular tachycardia (VT). Affected dogs may have echocardiographic evidence of dilated cardiomyopathy, but frequently have normal echocardiograms. Although VT is probably the most common cause of syncope in Boxers, neurocardiogenic bradycardia can also occur. OBJECTIVE: We describe 7 Boxers with comorbid VT and neurocardiogenic bradycardia, wherein the syncope was secondary to bradycardia rather than VT. ANIMALS: Seven Boxers were selected from a larger population of Boxers with Holter-documented VT because these dogs had documented bradycardia at the time of syncope. METHODS: Retrospective study. RESULTS: Although all dogs had Holter-documented VT, the etiology of the syncopal episodes was consistent with neurocardiogenic bradycardia. CLINICAL IMPORTANCE: Neurocardiogenic bradycardia or VT can occur as isolated problems in Boxers. In some Boxers, VT and potential or manifest neurocardiogenic bradycardia coexist. The administration of a beta-blocker or sotalol to such dogs can aggravate or precipitate neurocardiogenic bradycardia-related syncope.