Prevalence and Prognostic Role of L Wave and Selected Clinical and Echocardiographic Variables in Dogs with Atrial Fibrillation.

Abstract Background Information regarding the frequency of L waves and their prognostic relevance in dogs with secondary atrial fibrillation (AF) is limited. Hypothesis/Objectives To determine whether L waves occur and ascertain their prognostic role, as well as the role of other clinical and echocardiographic variables in dogs with AF. Animals Fifty‐five dogs with AF associated with myxomatous mitral valve disease or dilated cardiomyopathy. Methods Retrospective, multicenter observational study. In addition to L waves analysis, other clinical and echocardiographic variables, including type of antiarrhythmic treatment, were evaluated. A survival analysis was performed to test for predictors of cardiac death and all‐cause mortality using Cox proportional hazards regression models. Results L waves were evident in 33/55 dogs (60%, 95% confidence interval [CI] = 47%‐72%) but their presence did not influence outcome. Increased left ventricular end‐systolic diameter normalized for body weight (LVSDn) was a significant predictor of both cardiac death (hazard ratio [HR] = 4.41, 95% CI = 1.18‐16.54; P = .03) and all‐cause mortality (HR = 9.39, 95% CI = 2.49‐35.32; P < .001). Heart rate assessed during echocardiography (Echo‐HR) represented an additional significant predictor of cardiac death (HR = 1.01, 95% CI = 1.00‐1.01; P = .04) and all‐cause mortality (HR = 1.01, 95% CI = 1.00‐1.01; P = .04). Conclusions and Clinical Importance L waves occurred frequently in dogs with AF, but held no prognostic relevance. Conversely, LVSDn and Echo‐HR represented independent predictors of negative outcome in these animals.