Researchers have found that clinically significant findings of cardiac arrhythmia, as measured by Holter findings, are rare even among young Duchenne muscular dystrophy (DMD) patients with moderate cardiac dysfunction. The study, titled “Ambulatory Monitoring and Arrhythmic Outcomes in Pediatric and Adolescent Patients With Duchenne Muscular Dystrophy”, was published in the Journal of the American Heart Association.
Duchenne muscular dystrophy (DMD) is a muscular degeneration disorder caused by mutations in dystrophin. Though the potential for development of dilated cardiomyopathy in DMD has been known for decades, advances in respiratory care have improved life expectancy but also resulted in an almost uniform progression to dilated cardiomyopathy in long-term survivors.
To describe the frequency of significant Holter findings in patients with DMD, and to examine the association between cardiac function and arrhythmia burden, David Spar, MD, from the Cincinnati Children’s Hospital Medical Center and colleagues conducted a retrospective study in DMD patients who received a Holter (a portable device for continuously monitoring electrical activity in the cardiovascular system) between 2010 and 2014. The Holter test is usually performed after an electrocardiogram does not deliver enough information on a patient’s heart condition. All patients were classified based on left ventricular ejection fraction (LVEF), a measurement of the percentage of blood leaving the heart each time it contracts: ≥55%, 35% to 54%, and <35%. Holter findings analysed included atrial tachycardia, ventricular tachycardia, and atrial fibrillation/flutter.
A total of 442 Holter findings in 235 patients with DMD (mean age 14 years) were included in the statistical analysis.
The results revealed that patients with LVEF <35% had more arrhythmias, including nonsustained atrial tachycardia, frequent premature ventricular contractions, ventricular couplets/triplets, and nonsustained ventricular tachycardia, in comparison with the other groups. LVEF <35% was found to be a predictor of clinically significant Holter results. Four patients had a change in medication in the LVEF <35% group, nine in the ≥55% group, and four in the 35% to 54% groups.
Based on these findings researchers concluded that, “Sudden cardiac events are rare in DMD patients with an LVEF >35%. Significant Holter findings are rare in patients with DMD who have an LVEF >35%, and cardiac dysfunction appears to predict significant Holter findings. Holter monitoring is highest yield among DMD patients with cardiac dysfunction. Future studies should focus on patients with greater cardiac dysfunction or symptoms, as the arrhythmia burden appears small in DMD patients without severe dysfunction and without clinical symptoms.”