An Unusual Etiology of Cardiogenic Shock
An 11-year-old previously healthy female child presented to the emergency department for 4 days of cough, congestion, and malaise that progressed to dyspnea, pallor, cyanosis, and weakness. Over the prior several months, she had experienced intermittent swelling of her hands and lower extremities, worsening night sweats and posterior uveitis for which an infectious work-up was negative. On initial exam, she was dyspneic with poor perfusion as evident by cool extremities and poor capillary refill. Chest x-ray showed significant cardiomegaly (Figure 1). Electrocardiogram (ECG) showed sinus tachycardia with right atrial enlargement and left ventricular (LV) hypertrophy (Figure 2). Initial echocardiogram showed an ejection fraction of 10% without pericardial effusion, and her B-type natriuretic peptide was >5000 ng/L. She had an acute event consisting of a seizure and asystolic cardiac arrest and underwent 48 minutes of cardiopulmonary resuscitation. She underwent the hypothermia protocol for 48 hours and was transitioned to venoarterial (VA) extracorporeal membrane oxygenation (ECMO) for intractable low cardiac output and acidosis. She remained on VA ECMO for 4 days. After ECMO decannulation, her echocardiogram showed a moderately dilated LV with an ejection fraction of 15% and moderate to severe diastolic dysfunction (Figure 3) while on a milrinone drip of 0.75 mcg/kg/min. Cardiac transplantation work-up was initiated. While in the pediatric intensive care unit, she was noted to have systolic blood pressures up to 150 mmHg and diastolic blood pressures up to 96 mmHg despite several doses of intravenous hydralazine, and her heart rate was persistently 130-140 beats per minute. Magnetic resonance imaging of the brain showed evidence of several acute emboli without significant mass effect, midline shift, or hydrocephalus. Family history was notable for a mother with rheumatoid arthritis and maternal grandmother with hyperthyroidism. Her antinuclear antibody test was normal.
Figure 1: Chest X-Ray Shows Cardiomegaly
Figure 2: Twelve-Lead ECG Shows LV Hypertrophy With Strain Pattern and Right Atrial Enlargement
Figure 3: Apical 4-Chamber View Shows a Dilated and Hypertrophied LV
Which test is most likely to diagnose the cause of this patient's heart failure?