QT dispersion in patients with Duchenne-type progressive muscular dystrophy

Background A high degree of QT dispersion is a risk factor for arrhythmic s udden death in patients with myocardial infarction and cardiomyopathy. Duch enne-type progressive muscular dystrophy (DMD) is also associated with the development of ventricular arrhythmias. The purpose of this study was to de termine the relationship between QT interval dispersion and ventricular arr hythmias in patients with DMD. Methods Sixty-seven patients with DMD were studied. Standard 12-lead electr ocardiograms and 24-hour Holter electracardiograms were recorded, and the Q T interval was determined in every lead of the standard electrocardiogram t o determine the QT dispersion. QT dispersion was compared with the frequenc y of ventricular arrhythmias and the severity of skeletal muscle damage on the basis of the Swinyard and Deaver 8-stage scale. Results QT dispersion in all 67 patients averaged 54 +/- 18 ms. The QT disp ersion was 49 +/- 16 ms in stage 5 patients, 61 +/- 22 ms in stage 6 patien ts, 52 +/- 17 ms in stage 7 patients, and 56 +/- 17 ms in stage 8 patients. Ventricular arrhythmias Of Lown grade III or higher were observed in 3 of 35 patients with QT dispersion <60 ms and in 14 of 32 patients with QT disp ersion greater than or equal to 60 ms. Logistic regression analysis demonst rated that QT dispersion is an independent risk factor for ventricular arrh ythmias of grade III or higher in patients with DMD. Conclusions The incidence of ventricular arrhythmias of Lown grade III or h igher was greater in patients with QT dispersion greater than or equal to 6 0 ms than in patients with QT dispersion greater than or equal to 60 ms. QT dispersion therefore is a risk factor for serious ventricular arrhythmias in patients with DMD.