Magnetic Resonance Imaging of Right Ventricular Morphology and Function in Boxer Dogs with Arrhythmogenic Right Ventricular Cardiomyopathy

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disease characterized by fibrofatty replacement of the right ventricle and ventricular tachyarrhythmias, reported most commonly in the Boxer dog. Although ARVC is characterized as a myocardial disease, the impact of the disease on the function of the right ventricle has not been well studied. OBJECTIVE: To noninvasively evaluate the function and anatomy of the right ventricle in Boxer dogs with ARVC. ANIMALS: Five adult Boxer dogs with ARVC and 5 healthy size-matched hound dogs. METHODS: Magnetic resonance imaging was performed on an ECG-gated conventional 1.5-T scanner using dark blood imaging and cine acquisitions. Images were evaluated by delineation of endocardial right and left ventricular contours in the end-diastolic and end-systolic phases of each slice. Right and left end-systolic and end-diastolic volumes were generated using Simpson's rule and ejection fraction was calculated. Images were evaluated for right ventricular (RV) aneurysms and wall motion abnormalities. Spin echo images were reviewed for the presence of RV myocardial fatty replacement or scar. RESULTS: RV ejection fraction was significantly lower in Boxers with ARVC compared with the controls (ARVC 34%+/- 11 control 53%+/- 10, P < .01). There was an RV aneurysm in 1 dog with ARVC but not in any of the controls. RV myocardial gross fatty changes were not observed in dogs of either group. CONCLUSIONS AND CLINICAL IMPORTANCE: These findings could be interpreted to suggest that arrhythmias and myocardial dysfunction precede the development of morphological abnormalities in dogs with ARVC.