Treatment of supravalvular mitral stenosis in a kitten with hybrid balloon angioplasty.

Abstract

A five-month-old, 2.8-kg domestic shorthair cat was presented for further evaluation of supravalvular mitral stenosis and congestive heart failure. Thoracic radiography revealed severe cardiomegaly, pulmonary arterial and venous distention, and cardiogenic pulmonary edema. Thoracic echocardiography revealed a thick, perforate membrane within the left atrium, just dorsal to the mitral annulus. The majority of the left atrial body including the left auricle was dorsal to this membrane, consistent with the diagnosis of supravalvular mitral stenosis. Spontaneous echocardiographic contrast was observed within the left atrium. Left ventricular internal dimensions were reduced, and there was moderate concentric hypertrophy of the right ventricle with dilation of the main pulmonary artery. Medical management for congestive heart failure was initiated, and two days later, balloon angioplasty of the supravalvular mitral stenosis was performed successfully using a hybrid surgical approach. Transthoracic echocardiography performed the following day revealed an increase in the orifice diameter within the supravalvular stenotic membrane from 2.9 mm to 6.1 mm and improved left atrial outflow. At a scheduled recheck examination 6 months later, the owner reported a drastically improved activity level without any apparent clinical signs of heart disease. Transthoracic echocardiography revealed the orifice within the suprvalvular stenotic membrane was similar in diameter to the previous exam (6.0 mm), and there was resolution of the previously identified spontaneous echocardiographic contrast.