5.11 Endocardial cushion defect
Endocardial cushion defects cover a spectrum of abnormalities including ostium primum ASDs, VSDs, and malformed tricuspid and mitral valves. A cleft in the septal mitral leaflet may be present. The haemodynamic effects of the anomaly are variable but will include volume overload of the left side of the heart due to mitral regurgitation and the presence of the VSD. Cyanosis may be present. Affected foals are weak, stunted, and usually show signs of CHF. The diagnosis is made on echocardiography or post-mortem examination. The prognosis is hopeless.