Don't Take My Breath Away: A Case of High-Risk Pulmonary Embolism in the Setting of Patent Foramen Ovale Requiring Extracorporeal Membrane Oxygenation

Abstract

INTRODUCTION: Pulmonary emboli precipitate cardiovascular collapse by mechanical obstruction of the right ventricular outflow tract and pulmonary artery vasoconstriction, leading to right ventricular overload. The presence of a patent foramen ovale (PFO) can subvert this typical physiology by creating a right-to-left shunt, permitting left ventricular filling and near-normal cardiac output. However, this also causes intracardiac mixing of oxygenated and deoxygenated blood, which can further worsen hypoxemia. Here, we present a patient with saddle pulmonary emboli who was incidentally found to have a PFO due to persistent hypoxemia. CASE PRESENTATION:A 67-year-old man with a past medical history of coronary artery disease, alcohol abuse, hypertension, hyperlipidemia, and obstructive sleep apnea presented with word-finding difficulty and behavioral changes. He was found to have acute occlusion of the bilateral middle cerebral arteries, requiring mechanical thrombectomy. He was recovering successfully when he suddenly developed dyspnea and lightheadedness with exertion, which rapidly progressed to mechanical ventilation. He remained hypoxic on optimal ventilator settings and inhaled nitric oxide, prompting suspicion for acute pulmonary embolism. Chest x-ray was unchanged. EKG showed inferior ST-segment elevations, and a trans-thoracic echocardiogram revealed a newly dilated and overloaded right ventricle with an underfilled left ventricle, as well as McConnell's sign. Transesophageal echocardiogram showed a saddle pulmonary embolus and an incidental PFO with right-to-left shunting. Veno-venous extracorporeal membrane oxygenation (ECMO) was initiated as a bridge to mechanical thrombectomy. His course was complicated by cardiogenic shock, septic shock, and progression of his initial ischemic stroke. Encephalopathy remained a barrier to extubation.DISCUSSION: Recent studies have recognized ECMO as a promising adjunctive therapy for pulmonary emboli for those who are too unstable for surgical thrombectomy or who have contraindications to systemic thrombolysis. Our patient was not a candidate for thrombolysis given his recent stroke. His PFO, while beneficial in preventing florid cardiogenic shock by offloading the right ventricle, caused hypoxemia refractory to mechanical ventilation alone. As such, ECMO was a crucial temporizing measure until the patient was stable enough for surgical thrombectomy.CONCLUSIONS: This case highlights, prompt recognition of intracardiac shunts in cases of refractory hypoxemia, and the importance of early identification of patients who need advanced intervention such as ECMO.