Percutaneous balloon angioplasty as a treatment for cor triatriatum sinister in a cat

A 17-week-old, 2.7-kg cat was presented for management of congestive heart failure due to cor triatriatum sinister. Despite aggressive management for congestive heart failure with escalating diuretic doses, the cat remained symptomatic with exercise intolerance and dyspnea. Percutaneous transseptal balloon dilatation was scheduled. Computed tomography was performed prior to the procedure to aid in planning, which confirmed echocardiographic findings and excluded concurrent congenital defects. A transseptal puncture was performed under general anesthesia, and the cor triatriatum sinister membrane was crossed with a guidewire, allowing subsequent inflation with a 4-mm cutting balloon, followed by inflation of a 10-mm low-pressure balloon across the membrane. This resulted in marked improvement in pressure gradient across the membrane. Pulmonary venous puncture resulting in a mediastinal thrombus was the only complication encountered but was self-limiting and did not require any intervention. Diuretics were discontinued at a two-week recheck, and echocardiography confirmed resolution of the transmembrane gradient. A recheck echocardiogram nine weeks postoperatively, however, revealed restenosis of the membrane. Clinical signs of congestive heart failure were recurrent, requiring reinstitution of diuretic therapy. Percutaneous correction of cor triatriatum sinister is a technically challenging but feasible treatment option in small animals, though further investigation is needed to determine if restenosis is a common and/or preventable outcome.