TNNI3 and familial dilated cardiomyopathy: Both cardiac troponin I (cTnI) and cardiac troponin T (cTnT) are components of myocardial troponin-tropomyosin complex and elevated serum levels are observed in dilated cardiomyopathy (DCM) patients due to myocardial necrosis, apoptosis or myocardial leakage.