Transapical balloon dilation of cor triatriatum sinister in a cat.

A hybrid surgical approach was utilized to address cor triatriatum sinister in a 10-month-old castrated male domestic shorthair cat. Prior to surgery, open-mouth breathing occurred with exertion. The procedure was guided by transesophageal echocardiography and fluoroscopy. A minithoracotomy was performed, and the left atrial membrane was accessed via an introducer placed through the left ventricular apex. Sequential balloon dilations were performed, and the mean transmembrane gradient under anesthesia was reduced from 16 mmHg to 2.23 mmHg. Four months after surgery, the transmembrane mean gradient remained lower than prior to intervention. The cat tolerated surgery well and remains free of clinical signs nine months after surgery.