Chad Schmiedt 1, Heidi Kellum, Alfred M Legendre, Rebecca E Gompf, Janice M Bright, Christopher D Houle, Melissa Schutten, Rebecca Stepien

Background
Blastomycosis is a systemic fungal disease that commonly affects dogs, especially in endemic regions. While pulmonary, ocular, and osseous forms are well recognized, cardiovascular involvement is rare and poorly described. This retrospective study characterizes the clinical presentation, diagnostic findings, and outcomes of eight dogs with confirmed cardiovascular infection due to Blastomyces dermatitidis.

Methods
Medical records from two veterinary teaching hospitals were reviewed over a 22-year period to identify dogs with cardiovascular lesions attributed to Blastomyces. Data collected included history, clinical signs, diagnostic imaging, ECG, echocardiography, treatment, and postmortem findings when available.

Results
Eight dogs (median age 4.5 years) were identified, presenting with symptoms such as dyspnea, lethargy, anorexia, and syncope. Cardiovascular findings included myocarditis (4 dogs), pericarditis or epicarditis (2), and cardiac compression by granulomas (2). ECG abnormalities included third-degree AV block in one case. Echocardiography identified intracardiac masses or signs of pulmonary hypertension. Granulomatous lesions were confirmed histologically in several cases. Despite antifungal therapy, outcomes were poor: three dogs were euthanized, three died due to infection, and only two recovered with medical treatment. Cardiac lesions were associated with both new and recurrent infections, and postmortem findings confirmed extensive myocardial and vascular involvement in most cases.

Limitations
The small sample size and retrospective nature limit the study’s generalizability. Diagnostic and treatment protocols varied over the 22-year span, and cardiac blastomycosis may be underdiagnosed due to subtle clinical signs or absence of postmortem examination.

Conclusions
Cardiovascular involvement in canine blastomycosis, while rare, is clinically significant and may present with heart murmurs, arrhythmias, or signs of congestive heart failure. Dogs with systemic blastomycosis and cardiac signs should be evaluated for myocardial or pericardial disease. Prognosis is poor when myocardial involvement is present, emphasizing the need for early recognition and thorough cardiac evaluation in affected dogs.

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