Cardiac Troponin I (cTnI)

Cardiac Troponin I (cTnI) is a cardiac muscle protein with a molecular weight of 22,5 kilodaltons. Together with troponin T (TnT) and troponin C (TnC), TnI forms a troponin complex in heart to play a fundamental role in the transmission of intracellular calcium signal actin-myosin interaction. Although troponin I is also found in skeletal muscle, cardiac troponin I (cTnI) has additional amino acid residues on its N-terminal which distinguishes it from its skeletal muscle form making cTnI a specific marker for indicating cardiac infarction. cTnI is released rapidly into blood stream soon after the onset of acute myocardial infarction (AMI) . Its release pattern is similar to CK-MB (4-6 hours after the onset of AMI) . However, CK-MB level returns to normal after 36-48 hours, when levels of cTnI remains elevated for up to 6-10 days. The level of cTnI is below 0,06 ng/mL in average in healthy people, and also not detected in the patients with skeletal muscle injury. Therefore, cTnI is a specific marker for diagnosis of AMI patients. The level of cTnI may reach 100-1300 ng/mL in some AMI patients.