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.