Electrocardiographic abnormalities and sudden death in myotonic dystrophy type 1.
BACKGROUND
Sudden death can occur as a consequence of cardiac-conduction abnormalities in the neuromuscular disease myotonic dystrophy type 1. The determinants of the risk of sudden death remain imprecise.


METHODS
We assessed whether the electrocardiogram (ECG) was useful in predicting sudden death in 406 adult patients with genetically confirmed myotonic dystrophy type 1. A patient was characterized as having a severe abnormality if the ECG had at least one of the following features: rhythm other than sinus, PR interval of 240 msec or more, QRS duration of 120 msec or more, or second-degree or third-degree atrioventricular block.


RESULTS
Patients with severe abnormalities according to the entry ECG were older than patients without severe abnormalities, had more severe skeletal-muscle impairment, and were more likely to have heart failure, left ventricular systolic dysfunction, or atrial tachyarrhythmia. Such patients were more likely to receive a pacemaker or an implantable cardioverter-defibrillator during the follow-up period. During a mean follow-up period of 5.7 years, 81 patients died; there were 27 sudden deaths, 32 deaths from progressive neuromuscular respiratory failure, 5 nonsudden deaths from cardiac causes, and 17 deaths from other causes. Among the 17 patients who died suddenly in whom postcollapse rhythm was evaluated, a ventricular tachyarrhythmia was observed in 9. A severe ECG abnormality (relative risk, 3.30; 95% confidence interval [CI], 1.24 to 8.78) and a clinical diagnosis of atrial tachyarrhythmia (relative risk, 5.18; 95% CI, 2.28 to 11.77) were independent risk factors for sudden death.


CONCLUSIONS
Patients with adult myotonic dystrophy type 1 are at high risk for arrhythmias and sudden death. A severe abnormality on the ECG and a diagnosis of an atrial tachyarrhythmia predict sudden death. (ClinicalTrials.gov number, NCT00622453.)
Department of Medicine, Krannert Institute of Cardiology, Indiana University, Indianapolis 46202, USA. wgroh@iupui.edu
William J
WJ
Groh
Miriam R
MR
Groh
Chandan
C
Saha
John C
JC
Kincaid
Zachary
Z
Simmons
Emma
E
Ciafaloni
Rahman
R
Pourmand
Richard F
RF
Otten
Deepak
D
Bhakta
Girish V
GV
Nair
Mohammad M
MM
Marashdeh
Douglas P
DP
Zipes
Robert M
RM
Pascuzzi
D000328:Adult; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000209:etiology; D002423:Cause of Death; D016757:Death, Sudden, Cardiac / Q000209:etiology*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000150:complications* / Q000401:mortality; D011379:Prognosis; D012307:Risk Factors; D013610:Tachycardia / Q000175:diagnosis / Q000209:etiology