In the study of 406 pattients with myotonic dystrophy, severe abnormality was defined by arrhythmia, PR interval of 240 msec before, QRS duration of 120 msec or more, or second degree or third degree atrioventricular block.
Results showed that patients with severe ECG abnormalities were 5.5 times more likely to die suddenly than the other study participants. Those with atrial tachyarrythmia were 9.3 times more likely to die.
Authors wrote: ‘Our study shows that adult patients with myotonic dystrophy type 1 are at high risk for sudden death. The presence of a severe ECG abnormality and a clinical diagnosis of atrial tachyarrhythmia were the only independent predictors of sudden death detected in our analysis.’
New England Journal of Medicine (2008) 358: 22-31