Left Ventricular Noncompaction Suggests Myopathy

Suggests Myopathy To the Editor: We read with interest the article on left ventricular noncompaction (LVNC) in children by Pignatelli et al,1 who found that LVNC has a good prognosis and that LV systolic function may undulate between deterioration and recovery.1 The report raises several concerns: Thirteen of the 36 patients (36%) were suspected of having mitochondrial myopathy (MM), although only 5 underwent muscle biopsy. Muscle biopsy is an absolute requisite for diagnosing MM. Essential also are biochemical and genetic investigations, but abnormal biochemical investigations were reported only in a single patient. “Mitochondrial structural abnormalities with inclusion bodies” on electron-microscopy are non-specific and are found as well in other neuromuscular disorders (NMD).2 LVNC has been repeatedly reported in MM under the terms LV hypertrabeculation and isolated LV trabeculations.3 The underlying cause of LVNC is heterogeneous. Besides Barth syndrome and dystrobrevinopathy, LVNC is associated with myotonic dystrophy type-1, M. Pompe, cypher gene mutations, Becker muscular dystrophy, myoadenylate deaminase deficiency, and other rare genetic disorders.4 Coenzyme Q10, thiamine, riboflavin, and carnitine are not established therapy for MM. Uncritical administration of an obscure “metabolic cocktail” may have side effects, particularly in a disorder whose pathogenesis is not fully understood, and may be expensive. No data are presented on creatine-kinase, electromyography, nerve conduction studies, and imaging investigations, which may be abnormal in NMD. As LVNC has been reported to occur familially and is frequently associated with NMD, relatives of the 36 children should also have undergone neurologic investigation. In patients with LVNC but without NMD, muscle biopsy will be normal; therefore, endomyocardial biopsy remains a diagnostic option in these cases. What was the indication for echocardiography in 3 asymptomatic and 1 dysmorphic patient(s)? Was it possible to calculate the ejection fraction in all patients, despite the heavily trabeculated ventricles? Restrictive filling-pattern is characterized by increased, not decreased, E/A ratio.5 In adults, LVNC is predominately located in the lateral and anterior wall and the apex, sparing the interventricular septum.4 Was this distribution also found in children? How do the authors explain undulation of the left ventricular function? Could this finding be due to effective cardiac therapy or interobserver-variability? Did the authors observe growth or regression of LVNC in any of the patients? In how many patients did cardiac magnetic resonance imaging confirm LVNC? Why was acetyl salicylic acid given? The statement that undulation of LV function is responsible for the occurrence of LVNC in adulthood is not substantiated by the data presented. Because NMD are found in 82% of adults with LVNC,4 children with LVNC also require thorough neurological investigation.