**4. Cardiovascular Biomarkers**

Several biomarkers are currently used in the diagnosis and monitoring of cardiac disease.

Electrocardiogram and cardiac imaging are routinely used to detect the onset of DCM and its progression [5]. These non-invasive tests provide useful information about left and right ventricular function, both systolic and diastolic.

In addition, serum biomarkers provided to be very useful to characterize HF and are currently used to assess the functional status in adult and pediatric patients. In particular, serum levels of cardiac troponin I and T are known to be associated to the extension of myocardial damage, but there are conflicting results about their diagnostic and prognostic implications in the DMD DCM [18–20]. Recently, Voleti et al. [21] demonstrated that troponin I levels were significantly elevated in subjects with mild late gadolinium enhancement (LGE) compared to those without LGE. Interestingly, there was a lack of positive association between troponin levels and moderate-to-severe LGE probably because of a decreased enzyme leak at later stages of the disease, when most of myocardium has already been substituted by fibrofatty tissue. Hence, Troponin I could provide useful information to monitor patients in the clinical practice and further studies are required [21].

Elevation of left atrial pressure as result of left ventricular dysfunction and pulmonary hypertension caused by impairment of the respiratory muscles are considered to be involved in the mechanism of increased values of plasma natriuretic peptide in patients with DMD. A moderate or marked elevation in plasma alpha-ANP levels in patients with terminal DMD were found as a sign of a poor prognosis and may be a useful index for the management of the disease [22]. Villa et al. [23] reported a significant correlation between cystatin C, eGFR with cardiac dysfunction, providing for the first time a novel marker to evidence cardio-renal syndrome in patients with DMD.
