CARDIAC ABNORMALITIES AND CYTOSINE-THYMINE-GUANINE TRINUCLEOTIDE REPEATS IN MYOTONIC-DYSTROPHY

This study investigated the correlation between cardiac abnormalities and cytosine-thymine-guanine (CTG) trinucleotide repeat expansion in p atients with myotonic dystrophy (MD). We studied 18 patients with the adult form of classical MD and 18 age-matched control subjects. In pat ients with MD, left ventricular systolic function at rest was not diff erent From that in normal subjects. On the other hand, of Doppler para meters of diastolic function, mitral inflow peak early velocity and at rial velocity were significantly lower, and deceleration rime and isov olumic relaxation time were significantly longer in patients with MD c ompared with normal controls. No significant correlation was observed between these diastolic parameters and CTG repeat expansion in the pat ients, although the parameters showed a positive correlation with age and neurologic symptom duration. Electrocardiographic conduction abnor malities were detected in 42% of patients. These patients showed a sig nificantly longer symptom duration, although the size of CTG repeats w as not different between the patients with and without conduction abno rmalities. This study demonstrated that, in patients with MD, signific ant alterations in ventricular diastolic function (myocardial myotonia ) occur in addition to conduction abnormalities. The size of CTG expan sion is not a predictor of these cardiac involvements.