ABSTRACT
A 5-year-old, 7.9 kg castrated male Miniature Dachsund presented with heart enlargement on radiography. The dog was asymptomatic. Echocardiography revealed a tubular structure running along the posterior wall of the left atrium and connecting to the right atrium on the caudal side of the left atrium and annulus, which was presumed to be a dilated coronary sinus. After confirming a shunt between the left atrium and coronary sinus by cardiovascular catheterization, an unroofed coronary sinus was diagnosed. Open-heart surgery using cardiopulmonary bypass was performed through left atriotomy. The defect between the left atrium and the coronary sinus was closed by suturing. The cardiac enlargement improved after surgery. The dog was still alive 1227 days after surgery without clinical signs.
