A Case A Week for Veterinarians: Solution for Case 14

Radiographs show reverse ‘D’ appearance of heart on VD/DV views. Enlargement of right ventricle on lateral view. Enlargement of main pulmonary artery and tortuous appearance of pulmonary arteries.

Diagnosis: Heartworm disease

Differentials for the signs presented:

Dilated Cardiomyopathy
Congestive Heart Failure (Right-sided)

Further diagnostic tests:

Heartworm snap test
Echocardiography
CBC, Chemistry and urinalysis.

Radiographic findings are suggestive of heartworm disease. 2/6 Right AV systolic murmur may be due to heartworm disease. Other causes of the murmur could be dilated cardiomyopathy or congestive heart failure. Murmurs are caused by turbulent blood flow through the heart and vessels, a grade 2 murmur is a faint murmur restricted to a localized area.

Dilated cardiomyopathy (DCM) is an acquired disease characterized by progressive loss of cardiac contractility, ultimately leading to both left and right-sided congestive heart failure. It was ruled out based on radiographic findings.

Congestive heart failure (CHF) results in pulmonary edema (left-sided heart failure) or ascites (right-sided heart failure). With DCM and CHF, tachycardia is usually present. The absence of pulmonary edema and/or ascites rule out dilated cardiomyopathy and congestive heart failure.

Definitive diagnosis is heartworm disease based on thoracic radiographs and a positive heartworm test.

Treatment:

Prednisone 0.5mg/kg PO EOD for 10 days to combat any inflammation and as preventative for pulmonary thromboembolism.
Immiticide treatment- alternative dosing: 1 injection of Melarsomine HCL 2.5mg/kg deep IM, repeat injection in 1 month with 2 injections 24 hours apart.
A month after the third injection, give heartworm prevention.
Heartworm test 4 months after second set of immiticide injections.
Monitor for pulmonary thromboembolism, possibly administer anticoagulants.
Strict cage rest while being treated.
Monitor heart rate, respiration and attitude.