Evaluation of the North Star Ambulatory Assessment scale and cardiac abnormalities in ambulant boys with Duchenne muscular dystrophy

Abstract

We evaluated ambulatory patients with Duchenne muscular dystrophy from the cardiovascular standpoint and studied the correlation between the results of electrocardiographic (ECG) findings, left ventricular ejection fraction (LVEF), troponin T and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels and patients' North Star Ambulatory Assessment scores. Fifty patients of ages 6-12 (8.9 ± 2.8) were enrolled in this cross-sectional study. Cardiac evaluation included electrocardiography, echocardiography and cardiac enzyme tests. North Star scores ranged from 6/34 to 34/34. Twenty-eight patients (56%) had ECG changes. The most frequently seen ECG abnormalities were short PR interval (14%, n= 7), right ventricular hypertrophy (16%, n= 8), prolonged QTc interval (10%, n= 5), prominent Q wave (10%, n= 5) and T wave inversion (44%, n= 22). In 10 patients (20%), LVEF was below 55%, troponin T and NT-proBNP levels were significantly elevated (P= 0.003 and P < 0.001, respectively). When North Star scores were compared to patients' age, enzyme levels, ECG and echocardiographic results, we discovered negative correlation with age (P < 0.001) and troponin T levels (P= 0.02) and positive correlation with LVEF (P= 0.02). Patients with North Star scores of ≤16 are more at risk of developing cardiomyopathies. Troponin T is a cardiac index that can be used for evaluating myopathic patients and it seems to be correlated with the proBNP levels and LVEF values.