Delayed Opening of Patent Foramen Ovale in Recipients of Left Single Lung Transplant for Idiopathic Pulmonary Fibrosis

Abstract

<h3>Introduction</h3> Patent foramen ovale (PFO) is a common cardiac abnormality but rarely causes significant hemodynamic consequences in the absence of elevated right heart pressures. Cases of delayed reopening of PFO with right-to-left shunts have been reported following left single lung transplantation despite normal right heart pressures. This phenomenon occurs by redirection of blood flow through the inferior vena cava toward the PFO due to rightward mediastinal shift toward the fibrotic native lung following transplantation. <h3>Case Report</h3> Case1: A 72 year-old man with left single lung transplantation for idiopathic pulmonary fibrosis (IPF) developed new exertional hypoxemia on post-operative day (POD) 32. Pre-operative transthoracic echocardiogram (TTE) showed only intrapulmonic shunt, but no Valsalva maneuver was performed. Computed tomography (CT) scan of the chest demonstrated normal appearing allograft on the left and rightward mediastinal shift. Transbronchial biopsy showed no acute rejection. Perfusion scan showed the presence of a right-to-left shunt with tracer uptake of brain and kidneys and low likelihood for pulmonary embolism. TTE revealed a moderate PFO and normal right ventricular systolic pressure by echocardiographic criteria. Transesophageal echo (TEE) confirmed the presence of a large PFO. Hypoxemia resolved following percutaneous closure with a septal occluding device. Case 2: A 75 year-old man with PFO on pre-operative TTE underwent left single lung transplant for IPF. Post-operative course was complicated by exertional hypoxemia on POD 67. Workup included transbronchial biopsy without evidence of acute rejection and CT scan of the chest showing normal allograft on the left, new rightward mediastinal shift, and no pulmonary emboli. TTE showed a PFO at rest and TEE confirmed a large PFO with bidirectional flow. Right heart catheterization confirmed normal right-sided heart pressures prior to percutaneous PFO closure, resulting in resolution of hypoxemia. <h3>Summary</h3> Hypoxemia due to right-to-left shunting through a PFO is a possible post-operative complication of left single lung transplant for fibrotic disease even in the absence of elevated right-sided heart pressures. This can occur when a more compliant allograft causes mediastinal shift.