Age, conduction defects and restrictive lung disease independently predict cardiac events and death in myotonic dystrophy.

OBJECTIVE

The aim of the study was to identify, in addition to conduction defects, possible predictors of cardiac events and death in patients with myotonic dystrophy (DM1).

METHODS AND DESIGN

A retrospective observational cohort study was undertaken. Baseline clinical and non-invasive cardiac and respiratory investigations were obtained from 107 DM1 patients, who were regularly re-examined. Primary end-points were occurrence of cardiac events (pacemaker implantation or tachyarrhythmia) or death. Probability of an event was calculated using the Kaplan-Meier method, while contributing factors were assessed using univariate and multivariate (Cox model) analyses.

RESULTS

Cardiac events occurred in 34 patients (29%). Age, muscular impairment, infantile onset, restrictive lung disease (RLD), ECG conduction defects, left ventricular ejection fraction (LVEF) below 50%, and arrhythmia detected during Holter monitoring were predictors of cardiac events. Multivariate analysis indicated that age, RLD, ECG conduction defects, Holter arrhythmia and LVEF remained independent predictors. Probability of cardiac events was 2.5% (5%CI: 0-7%) at 1 year and 6% (5%CI: 0-14%) at 3 years in patients younger than 42 years with normal ECG, Holter, LVEF and lung volumes. Advancing age, distal or proximal weakness and RLD characterized all non-survivors (n=14).

CONCLUSION

Cardiac events or death are predicted not only by conduction defects or cardiomyopathy in DM1, but also by RLD, muscular disability and advancing age. Addition of these criteria should modulate time intervals for patient follow-up examinations. In young patients with normal baseline investigations, screening investigations every 2 or 3 years seem to be sufficient.