Electrocardiographic predictors of infrahissian conduction disturbances in myotonic dystrophy type 1

Aims The aim of this study was to determine electrocardiographic (ECG) criteria predicting abnormal infrahissian conduction in patients with myotonic dystrophy type 1 (DM1), as these criteria could be used to identify the need for an electrophysiological study (EPS). Methods and results A retrospective multicentre study was conducted including DM1-affected individuals who underwent EPS between 2007 and 2018. For each individual, EPS indication, His-ventricle (HV) interval, resting ECG parameters prior to EPS, left ventricular ejection fraction (LVEF), neurological status, and DM1 DNA analysis results were collected. Electrocardiographic parameters of patients with a normal HV interval were compared with ECG parameters of patients with a prolonged HV interval. Logistic regression was performed to determine predictors for a prolonged HV interval of ≥70 ms on EPS and diagnostic accuracy of ECG parameters was ascertained. Among 100 DM1-affected individuals undergoing EPS, 47 had a prolonged HV interval. The sole presence of a PR interval >200 ms [odds ratio (OR) 8.45, confidence interval (CI) 2.64–27.04] or a QRS complex >120 ms (OR 9.91, CI 3.53–27.80) on ECG were independent predictors of a prolonged HV interval. The combination of both parameters had a positive predictive value of 78% for delayed infrahissian conduction on EPS. His-ventricle interval was independent of DM1 genetic mutation size, neuromuscular status, and LVEF. Conclusion The combination of a prolonged PR interval and widened QRS complex on ECG accurately predicts abnormal infrahissian conduction on EPS in patients with DM1. These ECG parameters could be used as a screening tool to determine the need for referral to a specialized multidisciplinary neuromuscular team with EPS capacity.