Metabolic Cardiomyopathy and Mitochondrial Disorders in the Pediatric Intensive Care Unit

Abstract

ur patient, a 10 year-old boy with a past medical history significant for Pearson’s anemia, Addison’s disease, retinitis pigmentosa, ataxia, and sensorineural hearing loss, came to the pediatric intensive care unit with cardiogenic shock. He was born at 34 weeks gestational age with an uneventful delivery and had mild developmental delay. There was o family history for cardiac or genetic abnormalities. Pearson’s anemia was diagnosed when he was 4 months old, and he equired chronic transfusion therapy and monthly erythropoietin injections until age 3 years, when his disorder went into pontaneous remission. When he was 4 years old, Addison’s disease was diagnosed after a hospitalization for diarrhea and yponatremia. With the exception of an appendectomy for acute appendicitis, he had no other surgical history. His home edications included sodium bicarbonate, magnesium, calcium, potassium, enalapril, and spironolactone for his renal disorder; e was maintained on physiologic doses of prednisone for his Addison’s disease. On the day of admission, he was found unresponsive in his bed with labored breathing and generalized pallor. Paramedics ound the child unresponsive to painful stimuli. Rhythm strip revealed bradycardia and complete heart block. He was started on n isoproterenol infusion because of bradycardia and was then transported to the pediatric intensive care unit. On arrival, he was ound to be tachypneic with a Kussmal breathing pattern and bradycardic. His skin was pale and lips were dry. Results of an bdominal examination were significant for hepatomegaly with liver edge palpable 4 cm below the right costal margin. Capillary efill time was prolonged to 4 seconds with weak distal pulses. His mental status was significant for intermittent moaning, asking or his mother, and requesting water. Mildly enlarged cardiac shadow with bilateral alveolar infiltrates was demonstrated with chest radiography. An electroardiogram was performed (Figure), and moderate left ventricular dilation with reduced systolic function and mild tricuspid and itral valve regurgitation were demonstrated. Laboratory evaluation results were significant for arterial blood gas pH of 7.22, aCO2 5.2 torr, with a base deficit of 25. The serum chemistry results showed a serum bicarbonate level of 5.3 mEq/L, a lucose level of 245 mg/dL, a lactate level of 12 meq/L, and an ammonia level of 53 mol/L. Urine testing results were positive or ketones and glucose. The results of the remainder of laboratory studies, including complete blood count, liver enzymes, ilirubin, and coagulation studies, were normal. In the next several hours, he progressed to respiratory failure from pulmonary edema, requiring intubation and mechanical entilation. He was started on stress-dose steroids because of home steroid use and multiple inotropic agents to augment cardiac utput. Transcutaneous pacing was attempted, and intermittent capture was achieved at ventricular rates of 80, 90, and 100 beats er minute; however, there was no significant improvement in his hemodynamic condition. With further titration of his cardiac edications, including isoproterenol, milrinone, epinephrine, and dobutamine, his heodynamics improved in the subsequent 24 hours of hospitalization. Temporary transvenous ventricular pacing was initiated, which facilitated weaning off ll inotropes, and he was successfully extubated. Coenzyme Q10 and carnitine supplementaions were added, and a muscle biopsy was sent for mitochondrial analysis. Despite being etabolically stable, he remained in complete heart block, requiring placement of a permanent ransvenous dual-chamber pacemaker. His home medications were resumed, and he was ischarged to home at his neurologic baseline.