Case Study

Degenerative mitral valve disease in a 15 year old MN Australian Shepherd

A 15-year-old MN Australian shepherd was presented for evaluation of recent onset heart murmur with no overt clinical signs of heart failure.

A 15-year-old MN Australian shepherd was presented for evaluation of recent onset heart murmur with no overt clinical signs of heart failure.

Sonographic Differential Diagnosis

Degenerative mitral valve disease causing volume overload, moderate to severe mitral insufficiency and left atrial enlargement. Based on the ACVIM consensus statement, this is stage B2 (murmur and chamber enlargement).

Image Interpretation

This echocardiogram shows a volume overloaded left ventricle, moderately thickened mitral valve leaflets (the anterior leaflet prolapsing into the left atrium) and a moderately enlarged left atrium. Color Doppler reveals a moderate to severe mitral insufficiency, with very mild pulmonary and tricuspid regurgitation. There does not appear to be systolic dysfunction present since the movement of the interventricular septum and posterior wall is quite symmetric on M-Mode, and there is no septum hyperkinesia present. Flows across the left ventricular outflow tract and right ventricular outflow tract are normal but systolic ejection time (and volume) could be reduced (early closure of the AV on M-Mode).

DX

Degenerative mitral valve disease

Outcome

Triple therapy would be recommended (furosemide at a dosage of 1 mg/kg bid). Spironolactone may be added, but the evidence behind it’s use is not very strong. I would rescan the dog two months after initiation of therapy.

Comments

There is no consensus on how to treat these patients. But most cardiologists recommend initiation of treatment in dogs when left atrial size is over 1.8 x AO, and there is marked left ventricular overload present. Early radiographic and clinical signs of heart failure can be difficult to ascertain in an old dog. It is likely that this dog is going to develop CHF in the near future.