Tricuspid atresia with atrial and ventricular septal defects in a foal

Tricuspid atresia or the right atrio-ventricular atresia, with concurrent atrial and ventricular septal defects, a rare congenital cardiac anomaly, was diagnosed in a three month old Arabian foal from Kuwait. The foal had been weak and cyanotic since birth, sometimes becoming dyspneic when stressed. Necropsy revealed a dilated and hypertrophied left ventricle and a small sized right ventricle. The right atrio-ventricular valve was absent. Mitral valve was wide and insufficient to retain blood in the left auricle. A septal defect connected the right and left auricles. Similarly, the right and left ventricles communicated via a large kidney shaped septal defect, located immediately below the aortic valve. These cardiac anomalies resulted in chronic venous congestion and cardiac cirrhosis, with effusions in the pleural and peritoneal cavities. The factors involved in the pathogenesis are discussed.