Comprehensive non-invasive assessment of electrocardiographic abnormalities and cardiac arrhythmias in patients with genetically confirmed mitochondrial diseases.

BACKGROUND There is limited data on cardiac arrhythmias and ventricular repolarization and dispersion abnormalities in patients with mitochondrial diseases (MitD). METHODS Consecutive 40 patients with genetically proven MitD and 35 healthy controls were studied. Among other examinations all subjects underwent 24-h Holter recording and 12‑lead electrocardiography (ECG) with corrected QT (QTc), QT dispersion (QTd), Tp-e and Tp-e/QT ratio assessment. RESULTS Patients with MitD were 55.4 ± 15.7 years old, the disease duration was 18.5 ± 10.3 years, presented 6 clinical syndromes while mitochondrial and nuclear DNA type of mutation was present in 40 and 60% of cases, respectively. In MitD more frequently 1st degree atrioventricular block and intraventricular conduction defects were observed and also QRS complex duration was increased. Mean values of QTc (p = 0.001), QTd (p = 0.02), Tp-e (p < 0.00001) and Tp-e/QT (p < 0.00001) were significantly higher in MitD than in controls. Correlations between disease duration and PR interval duration (p = 0.003) and Creatine Kinase MB isoenzyme activity (p = 0.02) were found. No differences in depolarization and dispersion parameters were observed according to type of mutation or dominant clinical syndromes. In addition to supraventricular extrasystoles, nonsustained supraventricular tachycardias occurred more frequently in MitD (in 45.0 vs 14.3%, p = 0.0004). Ventricular arrhythmias were rare and observed almost exclusively in subjects with mitochondrial DNA mutation. CONCLUSIONS In contrast to healthy controls, in MitD patients intraventricular, repolarization and dispersion disturbances were more frequently observed. In addition to bradyarrhythmias observed in some defined MitD syndromes, supraventricular rather than ventricular arrhythmias are more common.