Cardiac function of children with Duchenne muscular dystrophy

Background:Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy. Clinical guidelines recommend that
evaluations for cardiomyopathy, arrhythmia, and heart failure be performed
upon diagnosisThe incidence of cardiomyopathy in DMD increases with age Early detection of muscular dystrophy associated cardiomyopathy is
important, because institution of cardioprotective medical therapies may slow
adverse remodeling and attenuate heart failure symptoms in these patients.
Aim: evaluation of cardiac function in children clinically suspected to have Duchenne muscular dystrophy.
Methods:28 male children who met criteria for diagnosis of Duchenne muscular dystrophy aged from 3 to 18 years compared to 47 healthy control children were approached to participate in the study and, after consent, were submitted to full clinical examination, blood samples were collected to determinate CPK (creatinine phosphokinase), Troponin I enzyme, Myoglobin and LDH (lactate dehydrogenase) enzyme level,echocardiography and 12-lead electrocardiogram were done.
Results:
28 Duchenne muscular dystrophy children and 47 age matched healthy male control children were included in the study. The mean age of study group was 7.29±3.24 years, and the mean age of the control group was 8.06±2. 86 years (p value 0 .28). 25% of cases had Positive family history of DMD. 35.7% of cases had positive consanguinity.all our  cases had elevated CPK  level (creatine phosphokinase)   .The mean  CPK level of cases  was 2495.79 ± 3457.02  While CPK level in controls was normal, (p value<0.0001). LDH level was elevated in 19 cases 67.86% of cases. The mean serum LDH level in DMD cases was 1232.07 ± 617.72. All control children have normal LDH level with mean 163.02 ± 109.62, (P value : <0.0001).The mean serum myoglobin level of (DMD) patients was higher relative to that of healthy controls   (but still within normal limits) 39.39  ± 7.25 versus 33.68 ±12.38 (ng/ml) respectively with statistically significant difference (P value: 0.01).There was no statistically significant difference between mean serum troponin I   level of DMD patients and that of controls 0 .03 ± 0.05 versus 0.01 ±0 .02  (U/L) respectively (p value: 0.37). Echocardiography of our patients revealed that one patient (3.57%)   had mild dilation of the left ventricular cavity which was statistically not significant, (P value: 0.37).7 cases (25%) of patients had low Ejection fraction (EF) and fraction shortening (FS) with mean (EF) 59.86 ± 10.20. All control children have normal EF with mean 73.30 ± 5.08 (P value : <0.0001). The mean FS was 20.29±5.59. All control children had normal (FS) with mean ±SD 36.17± 2.58 (P value : <0.0001). Electrocardiogram showed 28.57% of cases had sinus tachycardia with average heart rate (HR) 107 ±12.32 136. While 6.88% of controls had sinus tachycardia; (P value: 0.0001). Prolonged QTc interval was present  in39.29% of cases with a  mean of 431.39 ± 43.60 and that of controls was 415.17±25.2 (p value : <0.0001).  QTc duration of controls were normal for age. Other parameters of ECG were normal for age; no type of arrhythmia could be detected apart from sinus tachycardia.
Conclusion:ECG manifestations in children with DMD in the form of sinus tachycardia and prolonged QTC interval are an early alarm for developing cardiomyopathy before overt echocardiographic findings appear