Clinical, electrocardiographic, and diagnostic imaging features and outcomes in cats with electrocardiographic diagnosis of ventricular pre-excitation: a retrospective study of 23 cases (2010–2022)

Introduction/Objectives: Ventricular pre-excitation (VPE) occurs when atrial electrical impulses prematurely excite the ventricles through an aberrant muscle bundle known as an accessory pathway (AP). Orthodromic atrioventricular reciprocating tachycardia is a re-entrant, narrow complex supraventricular tachycardia (SVT), maintained through retrograde conduction over an AP. The study aimed to describe patient signalments, clinical signs, electrocardiographic (ECG) and diagnostic imaging features, treatments, prognostic variables, and outcomes in cats with ECG diagnosis of VPE. Animals: Twenty-three cats diagnosed with VPE between January 2010 and August 2022 were included in this study. Materials and Methods: This was a multicenter, retrospective study with twenty-three cats diagnosed with VPE between January 2010 and August 2022. Ventricular pre-excitation diagnosis was based on ECG evidence of shortened PR interval, delta wave, and prolonged QRS duration. The median survival time (MST) was estimated by the Kaplan-Meier curve. Log-rank tests were performed to assess for an association between clinical signs or presence of structural heart disease on the MST. Results: Fourteen (60.8%) cats with VPE also had SVT documented on ECG, with 7 of 14 with ECG confirmation of orthodromic atrioventricular reciprocating tachycardia. Four (17.4%) cats had suspected AP-mediated tachyarrhythmia based on associated clinical signs. Common presenting signs included collapse (15/23; 65.2%) and respiratory distress (14/23; 60.8%). Five (21.7%) cats were asymptomatic. Heart rate during SVT ranged from 310 to 420 bpm (median: 375 bpm). Initial treatment included atenolol (10/18), sotalol (5/18), diltiazem (2/18), and amiodarone (1/18). From the date of diagnosis, MST was 1872 days (5.1 years). Conclusions: The majority of cats with VPE also had symptomatic SVT. The prognosis for cats with VPE is considered good with an MST of greater than five years.