Metabolic aspects of myocardial disease and a role for L-carnitine in the treatment of childhood cardiomyopathy

Objectives. A multicenter retrospective study was conducted to investigate the possible metabolic causes of pediatric cardiomyopathy and evaluate the outcome of patients treated with L-carnitine. Methods. Seventy- six patients diagnosed with cardiomyopathy were treated with L-carnitine in addition to conventional cardiac treatment, and 145 patients were treated with conventional treatment only. There were 101 males and 120 females between 1 day and 18 years old. Cardiomyopathy diagnoses included dilated (148 patients), hypertrophic (42 patients), restrictive (16 patients), mixed diagnosis (11 patients), and 4 with an unknown type. Of 76 L-carnitine- treated patients, 29 (38%) had evidence to suggest a disorder of metabolism, and of 145 control patients, 15 (10%) were suspected to have a disorder of metabolism. These metabolic disorders were thought to be the cause for the cardiomyopathy of the patients. The duration of L-carnitine treatment ranged from 2 weeks to >1 year. Information was collected on length of survival (time-to-event), clinical outcome, echocardiogram parameters, and clinical assessments. Data were collected at intervals from baseline to study endpoint, death, transplant, or last known follow-up visit. Results. L- Carnitine-treated patients were younger than control patients and had poorer clinical functioning at baseline, yet they demonstrated lower mortality and a level of clinical functioning and clinical severity comparable to control patients on conventional therapy by the end of the study. An analysis of the interaction between clinical outcome and concomitant medications unexpectedly revealed that the population of patients treated with angiotensin-converting enzyme (ACE) inhibitors (40% of patients) had significantly poorer survival (although their greater likelihood for poor survival may possibly have made them more likely to receive ACE inhibitors). Conclusion. Results suggest that L-carnitine provides clinical benefit in treating pediatric cardiomyopathy. There is a need for further exploration of potential explanatory factors for the higher mortality observed in the population of patients treated with ACE inhibitors.