Relationship between 12-lead ECG and CTG expansion in myotonic dystrophy after 10 years of follow-up

Background. Myotonic dystrophy type 1 (DM1) is an autosomical dominant multisystemic disorder, with a frequent cardiac involvement, characterized mainly by an impairment of the conduction system and arrhythmias. Genetic transmission is due to a CTGn polynucleotide expansion on chromosome 19 (19q13.3), which shows in-vitro instability. Objective.To value the ECG differences and the CTG expansion size after 10 years, in a group of ten patients affected with DM1. Materials and methods. We genetically re-tested and value the surface-ECGs of ten DM1 patients (3 females, 7 males) after 10 years. Our patients were subgrouped on their expansion size as follows: E1 (<150 CTG), E2 (150-1000 CTG), E3 (>1000 CTG). Results. Our data show an increase of CTGn expansion in 7 patients; decrease in 1 patients; two were stable; in one patients the exact CTGn expansion size was unknown.Percent variation of CTG size ranged from 130,3% to -33,3% (mean value 36,1; standard deviation 55,8). Six patients show a worsening in electrical conduction on 12-leads ECG (AVB I, LAFB, LBBB); 4 ECG were unchanged. Conclusions. After ten years, a new genetic test and, a surface 12-leads ECG were performed in ten DM1 patients. ECG alterations (expecially sub hissian) seem be correlated to the variation of CTG expansion size without confounding factor of the age.