Complete atrioventricular block in a dog with myxomatous mitral valve disease and echocardiographic limitations
Case report
DOI:
https://doi.org/10.31533/pubvet.v20n6e1973Keywords:
Cardiac arrhythmia, congestive heart failure, dog, echocardiographyAbstract
The objective of this study was to report a complex case of multimodal management and diagnostic discordance among imaging modalities in a canine patient. A 13-year-old female Poodle was presented with chronic dry cough, dyspnea, tachypnea, a grade IV/VI holosystolic murmur over the mitral valve area, and severe bradycardia. Electrocardiography revealed a supra-Hisian complete atrioventricular block (cAVB), with a ventricular rate of 49 beats per minute. Thoracic radiography demonstrated severe cardiomegaly, with a Vertebral Heart Score (VHS) of 12.4 vertebrae, a caudodorsal alveolar pulmonary pattern consistent with cardiogenic pulmonary edema, and hepatomegaly. Biochemical analysis and abdominal ultrasonography confirmed secondary congestive hepatopathy, accompanied by marked elevations in liver enzyme activities. Conversely, echocardiography revealed morphologic parameters within normal limits, including a left atrium-to-aorta (LA/Ao) ratio of 1.23 and a normalized left ventricular internal diameter in diastole (LVIDdn) of 1.87, falsely suggesting ACVIM stage B1 myxomatous mitral valve disease (MMVD), despite exhibiting hyperdynamic ejection fraction (85%) and fractional shortening (53%). Treatment for congestive heart failure (CHF) was instituted according to the American College of Veterinary Internal Medicine (ACVIM) guidelines using torasemide (0.2 mg/kg), pimobendan (0.25 mg/kg), spironolactone (2 mg/kg), and benazepril (0.5 mg/kg) every 12 hours, combined with hepatoprotective therapy. After seven days of treatment, the patient showed complete resolution of the cough and normalization of the resting respiratory pattern. In conclusion, severe bradycardia resulting from cAVB alters diastolic and capillary pressure dynamics, potentially masking conventional echocardiographic indices of cardiac remodeling in MMVD. These findings highlight the primacy of clinical assessment and the need for an integrated, multimodal diagnostic approach in dogs with complex cardiac disease.
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