RESUMEN
A2-year-old cachectic cross-breed gelding was admitted to Veterinary Teaching Hospital of University of Tehran following the onset of a marked respiratory distress, coughing and ventral edema. Clinical examinations indicated harsh respiratory and expiratory sounds as well as jugular vein distention. The respiratory and heart rates were 35/min and 60 bpm, respectively. A grade III/IV pansystolic murmur with the PMI on the tricuspid valve, which could be heard on the left side, was detected. Sinus tachycardia was revealed by electrocardiography. Rupture of the chorda tendineae of the tricuspid valve, pulmonary artery regurgitation, pulmonary artery hypertension, tricuspid valve regurgitation, pulmonary artery, and right ventricular dilation were also found in echocardiography. These findings were confirmed at post mortem examinations. On the basis of the findings, chorda tendineae rapture of the tricuspid valve and right side heart failure due to primary pulmonary hypertension were diagnosed