Serum cardiac troponin I is a candidate biomarker for cardiomyopathy in Duchenne and Becker muscular dystrophies

INTRODUCTION/AIMS: Serum cardiac troponin I (cTnI), its relation to cardiomyopathy, and the contribution of the ACTN3 genotype to serum levels of cTnI in Duchenne and Becker muscular dystrophy (DMD and BMD, respectively) remain unknown. In this study we aimed to reveal the characteristics of cTnI, assess whether cTnI is a biomarker for cardiomyopathy in these dystrophinopathies, and evaluate the contribution of the ACTN3 genotype to the serum levels of cTnI in DMD patients. METHODS: Serum cTnI values obtained from 127 DMD and 47 BMD patients were analyzed retrospectively. The relationship between cTnI and echocardiography data or the ACTN3 XX genotype was assessed. RESULTS: The cTnI levels and proportion of patients with abnormal cTnI levels were significantly higher among DMD patients than BMD, especially in the second decade of life. In DMD, the cTnI level reached a maximum at 13 years, and left ventricular ejection fraction (LVEF) became abnormal approximately 1 year subsequently. In BMD, the cTnI level peaked at the age of 14 years, and LVEF became abnormal 3 years later. Decreased LVEF was observed after cTnI elevation in both populations. cTnI levels by age in DMD patients with the ACTN3 XX genotype tended to increase significantly and early. DISCUSSION: Myocardial injury indicated by cTnI elevation was more common and severe in DMD patients. cTnI elevation preceding cardiac dysfunction may represent an early phase of cardiomyopathy progression and may be a biomarker for early detection of cardiomyopathy in these dystrophinopathies. The ACTN3 XX genotype may be a risk factor for early myocardial injury.