Acute hypoxemia due to right-to-left shunt via a patent foramen ovale during left internal thoracic artery to left anterior descending artery anastomosis in off-pump coronary artery bypass grafting: a case report

Background: A right-to-left shunt via a patent foramen ovale (PFO) during off-pump coronary artery bypass (OPCAB) may result in difficulties in oxygenation and circulatory management. We herein present a case of a marked shunt via a PFO during OPCAB. Case presentation: A 74-year-old man who had aortic root enlargement, compressing the right atrium, and an atrial septal aneurysm, underwent OPCAB. When the heart was fixed for the anastomosis of the left anterior descending artery, sudden hypoxemia and hypotension were observed. Intraoperative transesophageal echocardiography (TEE) showed a right-to-left shunt via a PFO that was unnoticed preoperatively. After the anastomosis was completed, TEE revealed no shunt through the PFO. Conclusions: We should check for a PFO in case of an atrial septal aneurysm. Compression of the right atrium is considered an important anatomical risk of the right-to-left shunt in OPCAB.