Interatrial block to predict atrial fibrillation in myotonic dystrophy type 1.

Paroxysmal atrial fibrillation frequently occurs in Myotonic dystrophy type 1 (DM1) patients. Interatrial block is recognized as predictor of atrial arrhythmias, particularly atrial fibrillation (AF). The aim of this study was to evaluate the role of interatrial block in predicting the onset of atrial fibrillation during 2-year follow-up in DM1 patients who underwent pacemaker implantation for conduction system disorders. The study prospectively enrolled 70 DM1 patients (aged 36-69; 31 M) who underwent pacemaker implantation for cardiac rhythm abnormalities in accordance with the current guidelines. All DM1 patients underwent 12-lead surface ECG, 2D color Doppler echocardiogram and device interrogation at implantation, one month after and every six months thereafter for a minimum of 2-year follow-up. 12-lead surface ECGs were analyzed to diagnose interatrial block (IAB), defined as a P-wave duration ≥120 ms without (partial IAB) or with (advanced IAB) biphasic morphology (±) in the inferior leads. Device interrogation was performed to evaluate the development of new onset atrial high rate electrograms compatible with paroxysmal atrial fibrillation episodes. Interatrial block was detected in 22 patients (31.4%): 18 partial (25.7%) and 4 advanced (5.7%). During follow-up, AF episodes were detected in 18 DM1 patients (25.7%). The study population was divided into 2 groups according to the presence of AF (AF+ Group vs AF- Group). The AF+ Group was older and showed higher prevalence of IAB than the AF- Group. IAB was found to be independent predictor of AF in DM1 population (P < 0.001). A cut-off value of 121 ms for IAB had a sensitivity of 83.3% and specificity of 90.3% in identifying DM1 patients at high risk of developing AF. Interatrial block represents an independent predictor of AF occurrence in our DM1 population with conduction disturbances who had previously undergone pacemaker implantation.