Supraventricular and Ventricular Arrhythmias Are Related to the Type of Myotonic Dystrophy but Not to Disease Duration or Neurological Status.

Patients with myotonic muscular dystrophy (dystrophia myotonica, DM) are at risk of sudden cardiac death due to diverse arrhythmias, especially progressive atrioventricular (AV) conduction abnormalities. However, there are limited data on supraventricular and potentially life-threatening ventricular arrhythmias, especially according to type 1 and type 2 DM.A group of 94 unselected consecutive patients with genetically confirmed DM and 45 healthy controls underwent electrocardiography, echocardiography, and 24-hour Holter monitoring. DM1 was diagnosed in 51, while DM2 in 43 patients (with mean age of 37.3 ± 12.5 and 48.3 ± 13.3 years, respectively).DM1 subjects presented more frequently intraventricular conduction defects (29.4% vs 6.6%, P = 0.0003) and first-degree AV block (25.0% vs 4.6%, P = 0.008) than DM2 patients. Nonsustained supraventricular tachycardia (37.2% vs 3.8%, P = 0.001) and nonsustained ventricular tachycardia and/or R-on-T ventricular beats (23.2% vs 7.8%, P = 0.04) were more frequently observed in DM2 than in DM1. No relationship between disease duration and neurological status and occurrence of arrhythmias was observed. Multivariate analysis showed that independent predictor for bradyarrhythmias occurrence was DM1 only (odds ratio [OR] 6.4, 95% confidence interval [CI] 2.0-20.8, P = 0.002), while for supraventricular or ventricular arrhythmias occurrence it was DM2 (OR 4.1, 95% CI 1.5-11.4, P = 0.007) and increased age (OR 1.09, 95% CI 1.05-1.15, P < 0.0001).In the relatively large groups of DM1 and DM2 patients, we observed frequent various arrhythmias, which warrant their close cardiac monitoring. DM1 subjects when compared to DM2 presented more frequently intraventricular and AV conduction defects. However, all types of tachyarrhythmias (except atrial fibrillation) were more frequently observed in DM2 patients.