Mitral annular disjunction prevalence in 403 dogs referred for cardiac assessment (the MAD dog study).

Introduction/objectives: Mitral annular disjunction (MAD) is common in humans and is associated with myxomatous mitral valve disease (MMVD), mitral valve prolapse, and arrhythmias. It is poorly described in dogs, and its prevalence is unknown. The objective of this study is to establish the prevalence of MAD in a population of dogs referred for cardiac examination.

Animals, methods and materials: A total of 415 dogs were screened. Over one year, dogs referred for cardiac assessment were prospectively enrolled. Age, breed, body weight, electrocardiography, and echocardiography were recorded. Dogs with systolic loss of continuity between the basal segment of the left ventricular posterior wall and the mitral valve (in right parasternal long-axis echocardiography) were considered to suffer from MAD.

Results: Four hundred three dogs were included in the study. Seven dogs exhibited MAD. All MAD dogs had MMVD. No normal dogs exhibited MAD. The overall prevalence of MAD was 1.7%. The prevalence of MAD in dogs with MMVD was 2.5%. The prevalence of MAD in dogs with mitral valve prolapse was also 2.5%. No MAD dogs exhibited arrhythmias. The presence of MAD was associated with lower body weight.

Study limitations: Single-operator bias and evolving diagnostic criteria for MAD in people complicate the interpretation of study results.

Conclusions: Mitral annular disjunction is uncommon in dogs referred for cardiac evaluation and could only be identified in dogs suffering from MMVD. No arrhythmias were found in MAD dogs.