Early cardiac evaluation in children with non-specific mitochondrial disease with isolated mitochondrial respiratory chain complex i defect

Aims: We evaluated echocardiography and electrocardiography (ECG) results in children with non-specific mitochondrial disease (MD) in order to study early cardiac involvement, a well-known complication of the disease. Methods: Among non-specific MD children whose isolated mitochondrial respiratory chain complex I defect was confirmed by muscle biopsy and satisfied the criteria of MD, 27 who had no cardiac symptoms were evaluated by echocardiography and ECG. Results: Three (11.1%) out of the 27 non-specific MD patients had left ventricular ejection fraction of less than 55% and two of them (7.4%) had fractional shortening of less than 26%. ECG abnormalities were observed in 16 of the non-specific MD patients (59.3%). Prolongation of heart rate-corrected QT interval was seen in 11 (40.7%) and widening of the QRS interval in eight (29.6%). Left ventricular ejection fraction and fractional shortening of the patients were significantly decreased compared with those in the control group while heart rate-corrected QT interval was prolonged in the former group. QRS interval was more widened in non-specific MD patients, but without statistical significance. Conclusion: The potentially severe cardiac involvement observed in our subjects suggests that early cardiac evaluation after confirming the diagnosis of MD and regular follow-up tests should be strongly recommended in children even in cases without typical cardiac manifestations.