ABSTRACT
Patent foramen ovale (PFO) is a frequent congenital anomaly, but massive right-to-left shunt (RTLS) is normally prevented by higher pressures in left heart chambers. However, mechanical ventilation with positive end-expiratory pressure (PEEP) can significantly increase right atrial pressure, accentuating the RTLS, mainly after major cardiothoracic surgery. We report a patient admitted to the intensive care unit after cardiac surgery. Pre- and intraoperative transesophageal echocardiography only described an aneurysmal interatrial septum with no shunt. However, high-PEEP ventilation induced a paradoxical response with life-threatening hypoxemia, triggering further echocardiographic evaluation, revealing massive RTLS across a stretch PFO. Provocative maneuvers (Valsalva/PEEP) significantly increase echocardiographic sensitivity, unmasking silent PFO. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:58-61, 2017.
