A 10-year-old, spayed Labrador retriever crossbreed with acute-onset weakness and lethargy was presented on emergency to a referral institution.
The dog had no history of travel or trauma and was current on vaccinations and appropriate parasite control. At presentation, it was recumbent but conscious and responsive.
Examination findings included muffled heart sounds, poor peripheral pulses, pale mucous membranes with a CRT of 2 seconds, rectal temperature of 98.7°F, and distal extremities cool to the touch. ECG suggested ventricular premature contractions. Echocardiography revealed pericardial effusion and a right atrial mass (Figure 1).