Myotonic dystrophy type 1 (DM1) is a neurologic disorder with known cardiac involvement, including left ventricular systolic dysfunction (LVSD), heart failure (HF), atrioventricular and intraventricular conduction system disease, and sudden death. We studied the prevalence of these conditions and associated findings in a large population with DM1.

History, physical examination, genetic testing, and electrocardiography were performed on 406 patients with DM1, and cardiac imaging was performed on 180 (44.3%) of these patients.

Left ventricular systolic dysfunction and clinical HF were found in 34 (18.9%) of 180 and in 23 (5.7%) of 406 of enrolled subjects, respectively, yielding an overall prevalence of LVSD/HF in 41 (10.1%) of 406. Increasing age, male sex, electrocardiographic conduction abnormalities, presence of atrial and ventricular arrhythmias, and implanted devices were all significantly associated with LVSD/HF, whereas cytosine-thiamine-guanine repeat length and neuromuscular severity score were not. The interval ≥240 milliseconds (relative risk 4.1, 95% CI 1.7-9.6, P = .001) and QRS duration ≥120 milliseconds (relative risk 4.2, 95% CI 2.0-8.5, P < .001) were significant predictors of LVSD/HF. The presence of LVSD/HF was also significantly associated with all-cause death (relative risk 3.9, 95% CI 2.3-6.4, P < .001) and cardiac death (relative risk 5.7, 95% CI 2.6-12.4, P < .001).

A significant prevalence of LVSD/HF exists in patients with DM1. The presence of LVSD/HF in DM1 is significantly associated with all-cause and cardiac death.