Background: Cardiac complications, such as myocardial disease and arrhythmias, are frequent and may be severe in patients with mitochondrial disease. We sought to determine the prevalence and the prognostic value of cardiac abnormalities in a series of patients carrying the m.8344 A>G mutation.
Methods: We retrospectively collected data concerning a cohort of patients carrying the m.8344A>G mutation. Patients systematically underwent neurologic examination, muscular biopsy, measurement of forced vital capacity, and cardiac evaluation including electrocardiogram, echocardiography, and 24-hour ambulatory electrocardiogram at diagnosis. Neurologic and cardiac evaluations were repeated during follow-up at least every 2 years.
Results: Eighteen patients (mean age 39.3 +/- 17.3 years, 10 women) from 8 families were investigated. Mean follow-up duration was 5.0 +/- 2.7 years. Cardiac abnormalities were identified at diagnosis in 8 patients (44.4%, age 39.1 +/- 17.7 years), including dilated cardiomyopathy in 4, Wolff-Parkinson-White syndrome in 3, incomplete left bundle branch block in 1, and ventricular premature beats in 1. Two additional patients developed left ventricular dysfunction during follow-up and 2 patients died due to heart failure. Subgroup analyses identified early age at disease onset as the only factor significantly associated with myocardial dysfunction.
Conclusions: We identified a high prevalence of ventricular dysfunction and Wolff-Parkinson-White syndrome. Myocardial involvement was associated with an increased risk of cardiac death due to heart failure, suggesting that cardiac investigations should be systematically considered in patients carrying the m.8344A>G mutation.