163: THINK INSIDE THE BOX: ACUTE MITRAL REGURGITATION MASQUERADING AS PEDIATRIC ARDS

Abstract

Introduction: Acute mitral regurgitation (MR) due to papillary muscle rupture is a recognized complication of adult myocardial infarction but is rare in pediatrics. Presenting with dyspnea, acute pulmonary edema, and shock, acute MR can mimic acute respiratory distress syndrome (ARDS). Accurate and timely diagnosis is critical, as acute MR is a surgical emergency with high mortality risk. Description: A previously healthy 12-year-old male presented to the emergency department with one day of emesis, palpitations, and dyspnea. He was tachypneic, tachycardic, and hypoxemic and received supplemental oxygen and a 20 ml/kg fluid bolus. Chest radiograph showed bilateral infiltrates, point-of-care ultrasound (POCUS) was concerning for pneumonia, and antibiotics were given. POCUS also showed hyperdynamic left and normal right ventricular systolic function without pericardial effusion. He developed rapidly progressive hypoxic respiratory failure and was intubated. Intubation was notable for copious pink, frothy secretions. After PICU admission, he had progressive hemodynamic instability and rising lactate requiring escalation of vasopressors and inotropes. A complete echocardiogram showed mild MR and normal function. Due to rising mean airway pressure and worsening oxygenation index, he was cannulated to veno-venous extracorporeal membrane oxygenation. Repeat echocardiogram post-cannulation showed moderate to severe MR, prolapse of the anterior mitral leaflet, a prominent round papillary muscle, moderate left atrial dilation, mild-moderate left ventricular dilation, and hyperdynamic LV systolic function. Trans-esophageal echocardiogram confirmed diagnosis of acute MR due to papillary muscle rupture. He underwent mitral valve replacement with a St. Jude prosthetic mechanical valve. Pathologic evaluation of excised tissue showed lymphocytic myocarditis, endocardial inflammation, and patchy fibrosis. Rheumatologic evaluation is ongoing, and patient was discharged in good condition. Discussion: We report a rare presentation of lymphocytic myocarditis with papillary muscle rupture and acute MR. The presentation mimicked a rapid progression of pediatric ARDS, and highlights that a high index of suspicion is required to ensure timely diagnosis of this life-threatening process.