Transesophageal echocardiographic and oxymetric evidence of intraoperative reversal of flow through a patent foramen ovale during an off-pump coronary artery bypass grafting

Mechanical stabilization of target coronary arteries in the beating heart has facilitated the practice of "off-pump" coronary artery bypass grafting. Exposing the target coronary artery for stabilization involves maneuvers that frequently cause hemodynamic alterations including decreased cardiac output and increased pulmonary artery and/or central venous pressures (CVP). The presence of a patent foramen ovale (PFO) in the setting of increased CVP may produce a right-to-left shunt through the PFO. We report a case of a patient undergoing off-pump coronary artery bypass grafting with a PFO with a left to right atrium shunt flow of 307 mL/min. During manipulation and elevation of the heart to expose the target vessel, the CVP increased from 15 to 30 mm Hg and the shunt through the PFO reversed direction, going from right to left atrium with a flow of 161 mL/min. Mixed venous oxygen saturation and the calculated shunt fraction decreased from 84% to 78% and 14% to 10%, respectively. All parameters returned to normal after the heart was lowered back inside the chest.