Dog with heart blockage caused by a tumor in the left ventricle

Abstract

This is the first description of a left ventricular inflow tract obstruction secondary to a myxoma in a dog. A 4 yr old, male fox terrier presented with a 1 mo history of cough and exercise intolerance. Expiratory dyspnea, pulmonary crackles, irregular cardiac rhythm, and a grade 4/6 pansystolic cardiac murmur over the left cardiac apex were the most important features on physical examination. The electrocardiogram revealed atrial fibrillation. Thoracic radiographs showed left-sided cardiac enlargement and mild pulmonary edema, especially in the hilar area. Two-dimensional transthoracic echocardiography showed severe left atrial dilation and a homogenous, echodense mass involving both leaflets of the mitral valve and the posteromedial papillary muscle, inducing mitral stenosis. Spectral Doppler echocardiography was consistent with severe left ventricular inflow tract obstruction secondary to a mass. Therapy for congestive heart failure was prescribed. Follow-up examinations of the dog 1 mo, 2 mo, and 6 mo after diagnosis showed an improvement in clinical signs, but similar echocardiographic features. Eleven months after diagnosis, the dog was euthanized at the owner's request because of recurrent congestive heart failure. The postmortem examination showed the cardiac tumor was consistent with a myxoma.