Abstract 15756: To Close or Not to Close: A Case of Multisystem Immune Checkpoint Inhibitor Toxicity and PFO

Abstract

Introduction: Recent emergence of immune checkpoint inhibitors (ICIs) in oncologic treatments has led to increasing research on their side effect profile. Myocarditis occurs in roughly 0.04-1.14% of patients treated with ICIs and is associated with up to 50% mortality. We present a case of multisystem ICI toxicity requiring comprehensive evaluation to ultimately reveal a PFO shunt as the cause of persistent hypoxemia. Case: A 67-year-old male with Stage IIIC cutaneous melanoma presented with non-radiating pleuritic chest pain, diplopia, dyspnea and syncope. ECG showed high grade AV block and right bundle branch block. Labs showed elevated troponin, creatinine kinase and inflammatory markers. An echocardiogram showed edematous myocardium, a small pericardial effusion, and akinetic apical/inferior septal segments. Despite diuresis, 5g of methylprednisolone, IV immunoglobulin plus mycophenolate and resolution of AV block, the patient had hypoxemia on 100% FiO2. He underwent a CTA (which ruled out PE and ICI-induced pneumonitis) and fluoroscopic sniff test (revealing bilateral moderate diaphragm paresis). A recent cardiac catheterization on prior admission showed no obstructive coronary disease. Arterial blood gas showed pO2 120 mmHg without hypercapnia on 100% FiO2. We suspected a shunt as the underlying cause and obtained a bubble study disclosing a large (> 25 bubble) PFO with right-to-left shunt. Results: Given the timing of symptoms, it was determined that pembrolizumab administration caused myocarditis and myositis with diaphragmatic paresis. In patients with pulmonary disease or diaphragmatic paresis, elevated intrathoracic and pulmonary artery pressures have been a proposed mechanism of acute worsening of right-to-left shunt resulting in hypoxemia. The patient underwent right heart catheterization and PFO closure using Gore Cardioform septal occluder with resolution of hypoxemia. A repeat echocardiogram obtained 1 month later was normal. Conclusion: All concerning clinical symptoms in the setting of ICI use require a thorough evaluation. In this case, persistent hypoxemia despite treatment for ICI toxicity unmasked a large PFO requiring closure. A multisystem approach should be used to assess suspected ICI myocarditis.