Right-to-Left Shunt via a Patent Foramen Ovale Triggered by Constrictive Pericarditis With Right Heart Compression: A Case Report

We report a rare case of a right-to-left shunt through a patent foramen ovale (PFO) triggered by constrictive pericarditis secondary to an organized pericardial hematoma. A 72-year-old woman presented with thoracic back pain and subsequently developed persistent hypoxemia following idiopathic pericarditis. Despite appropriate anti-inflammatory and antimicrobial therapy, she experienced a cerebral embolism involving the right middle cerebral artery territory on hospital day 50. Imaging studies revealed a pericardial effusion compressing the right heart. Intraoperative transesophageal echocardiography confirmed a right-to-left shunt through a PFO. Surgical evacuation of the organized pericardial hematoma relieved right heart compression, normalized intracardiac pressures, and resolved the shunt. The pericardium was markedly thickened and adherent to the right ventricle with a fibrotic hematoma, and histopathology revealed fibrotic thickening with inflammatory infiltration and hemosiderin deposition. The patient's respiratory status gradually improved, and she was discharged home without the recurrence of paradoxical cerebral embolism. This case highlights a rare pathophysiological mechanism in which constrictive pericarditis elevates right atrial pressure, unmasking a previously silent PFO and resulting in paradoxical embolism and refractory hypoxemia. Constrictive pericarditis should be considered a potential trigger for right-to-left shunting in patients with unexplained hypoxemia or cryptogenic stroke.