A six-year-old male intact Labrador retriever with a history of recent importation from Taiwan, heartworm (Dirofilaria immitis) infection, and “slow-kill (Heartgard®) therapy” of approximate 4 month duration, was presented to the Cornell University Hospital for Animals for multiple episodes of collapse and hematochezia. On initial presentation, the patient was dull, had pale mucous membranes, and an elevated heart rate. Cardiothoracic auscultation revealed crackles in the dorsal lung fields and a right-sided heart murmur (grade IV-VI). Additional diagnostics confirmed the presence of heartworms in the main pulmonary arteries. Treatment with intravenous fluids, pimobendan, sildenafil, doxycycline, metronidazole, prednisone, clopidogrel and supplemental oxygen was implemented. The patient was discharged after a five day hospitalization, with instructions to return after four weeks of strict rest for initiation of adulticidal heartworm treatment.

This report highlights relevant clinical findings, diagnostics, and treatment protocol in a dog with clinical heartworm infection.