Antemortem diagnosis of a ventricular septal defect in a California sea lion Zalophus californianus

A yearling California sea lion Zalophus californianus stranded in poor body condition, and on physical examination a heart murmur was audible bilaterally. The sea lion was diagnosed with a left-to-right shunting membranous ventricular septal defect (VSD) using B-mode, color-flow Doppler and continuous-wave Doppler echocardiography. A left-to-right intracardiac shunting lesion was confirmed during cardiac angiographic computed tomography. The VSD defect was verified during the necropsy examination. On histologic examination concurrent mild multifocal myocarditis with focal mild ventricular free-wall myocardial necrosis were identified. A specific cause for the myocarditis and myocardial necrosis was not found, and association with the VSD and resultant myocardial dysfunction was presumed. This is the first report of the antemortem diagnosis of a VSD in a marine mammal and the first report of a VSD in a California sea lion.