Evaluation of repolarization abnormalities with 12-lead ECG and 24-hour Holter ECG monitoring in patients with Duchenne muscular dystrophy

Abstract

Background

Duchenne muscular dystrophy (DMD) is an inherited neuromuscular disorder causing progressive degeneration of skeletal and cardiac muscles due to dystrophin deficiency. Cardiac involvement ranges from mild to severe, including heart failure, arrhythmias, conduction defects, and sudden cardiac death.

Objective

This study aimed to evaluate early markers of cardiac repolarization abnormalities in DMD patients by analyzing standard 12‑lead ECG parameters—QT interval, corrected QT (QTc), T peak to T end (Tp-e), Tp-e/QT, and Tp-e/QTc ratios—and microvolt T-wave alternans (MTWA) from 24-h Holter monitoring.

Methods

Seventy-four individuals participated: 39 DMD patients and 35 age- and sex-matched healthy controls. Data on demographics, ambulation status, ECG, and Holter recordings were collected and compared. All participants underwent standard 12‑lead electrocardiography and 24-h Holter electrocardiogram monitoring. ECG measurements were performed manually by a blinded operator using standardized techniques. Holter recordings were collected and compared (analyzable data obtained from 33 patients and 34 controls). The QTc interval was calculated using Bazett's formula. Correlation analyses and statistical comparisons between groups were performed using appropriate parametric and non-parametric tests.

Results

DMD patients exhibited significantly higher resting heart rates. The Tp-e interval was similar between groups, while the QT interval was significantly shorter in the patient group, the QTc interval showed no significant difference between groups. Tp-e/QT ratio was higher in the patient group; Tp-e/QTc ratios showed no difference. The QTc interval was significantly prolonged in the non-ambulatory DMD group. MTWA values did not differ significantly between groups. Due to the limited sample size and absence of established pediatric reference values, MTWA findings must be considered inconclusive.

Conclusion

In conclusion, our study reveals subtle repolarization alterations in DMD patients, including elevated resting heart rate and a trend toward increased Tp-e/QT ratio. While these findings do not yet establish a definitive arrhythmic phenotype, they suggest the presence of early electrophysiological changes that may warrant longitudinal cardiac evaluation. Prospective follow-up studies are essential to determine the prognostic significance of these parameters and their relationship to clinical arrhythmic outcomes in the pediatric DMD population.