Radiography and Echocardiography

Radiography

Generalized cardiomegaly is usually evident, although left-heart enlargement may predominate. Cardiomegaly may be severe enough to mimic the globoid cardiac silhouette typical of large pericardial effusions. In contrast, Doberman Pinschers and some Boxers appear to have mainly left atrial enlargement without marked cardiomegaly. The stage of disease, chest conformation, and hydration status influence these radiographic findings.

Distended pulmonary veins and pulmonary interstitial or alveolar opacities, especially in the hilar and dorsocaudal regions, indicate the presence of left heart failure and pulmonary edema. Some dogs have asymmetric or widespread distribution of pulmonary edema infiltrates. Pleural effusial, distention of the caudal vena cava, hepatomegaly, and ascites usually accompany right-sided heart failure.

Echocardiography

Echocardiography is the best means of assessing cardiac chamber dimensions and myocardial function and for differentiating pericardial effusion or chronic valvular insufficiency from DCM. Dilated cardiac chmbers and poor systolic ventricular wall and septal motion are characteristic findings in DCM. All chambers are usually affected, but right atrial and ventricular dimensions may appear normal, especially in Dobermans and Boxers. Left ventricular systolic dimension is increased, and fractional shortening is decreased.

Other common features are a wide mitral valve E point-septal separation and reduced aortic root motion. Left ventricular free-wall and septal thickness are normal to decreased. Mild to moderate AV valve regurgitation may be seen with Doppler ecocardiography. Dobutamine stress testing may provide insight as to the presence of early myocardial dysfunction in dogs thought to be at risk for DCM, but further research is needed to define the clinical applicability and optimal dosage for this more clearly.