1 Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet2 Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet3 unknown4 Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet5 Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet
A cross-sectional study
BACKGROUND: Patients with myotonic dystrophy type 1 (DM1) have a three-fold higher risk of sudden cardiac death (SCD) than age-matched healthy controls. Despite numerous attempts to define the cardiac phenotype and natural history, existing literature suffers from low power, selection-bias and lack of controls. Thus, the optimal strategy for assessing cardiac involvement in DM1 is unclear. METHOD: In this large single-centre study, we evaluated 129 unselected DM1 patients (49.6% men), mean (SD) age 44 (14.7) years with family history, physical examination, electrocardiogram (ECG), echocardiography, Holter-monitoring and muscle strength testing. RESULTS: Cardiac involvement was found in 71 patients (55%) and included: 1) Conduction abnormalities: atrio-ventricular block grade I (AVB grade I) (23.6%), AVB grade II (5.6%), right/left bundle branch block (5.5/3.2%) and prolonged QTc (7.2%); 2) arrhythmias: atrial fibrillation/flutter (4.1%), other supraventricular tachyarrhythmia (7.3%) and non-sustained ventricular tachycardia (4.1%); and 3) structural abnormalities: left ventricular systolic dysfunction (20.6%) and reduced global longitudinal strain (21.7%). A normal ECG was not significantly associated with normal findings on Holter-monitoring or echocardiography. Patients with abnormal cardiac findings had weaker muscle strength than those with normal cardiac findings: ankle dorsal flexion (median (range) 4.5 (0-5) vs. 5.0 (2.5-5), p=0.004) and handgrip (median 4.0 (0-5) vs. 4.50 (2-5), p=0.02). CONCLUSION: The cardiac phenotype of DM1 includes a high prevalence of conduction disorders, arrhythmias and risk factors of SCD. Systematic cardiac screening with ECG, Holter-monitoring and echocardiography is needed in order to make a proper characterization of cardiac involvement in DM1.
International Journal of Cardiology, 2014, Vol 174, Issue 1, p. 31-36