Natural history of cardiac involvement in myotonic dystrophy: Correlation with CTG repeats

The authors prospectively studied the natural course of cardiac involvement and its relationship to cytosine-thymine-guanine (CTG) expansion in 50 pat ients with myotonic dystrophy who were submitted to periodic cardiovascular EKG and EKG-Holter monitoring during a median follow-up of 56 months. Nine teen patients (38%) developed major EKG changes. CTG length was not correla ted with the frequency of EKG abnormalities, but was inversely correlated w ith the age at onset of EKG abnormalities (p < 0.0001). CTG length influenc es the timing of cardiac complications in myotonic dystrophy.