The cardiac troponin I (cTnI), one of the subunits of the troponin regulatory complex, binds to actin and inhibits interactions between actin and myosin. cTnI is highly sensitive and specific marker for myocardial injury and is useful in diagnosis and detection of reperfusion in acute myocardial infarction (AMI). In this study, we measured the serum concentration of cTnI according to serial time after chest pain in patients with AMI and compared serum concentration of cTnI with CK-MB and echocardiographic data to evaluate the significance of measuring serum concentration of cTnI in AMI.

The study was carried out on 16 patients with first attack of AMI within 6 hours of chest pain. All patients were performed thrombolytic therapy and reperfusion was confirmed by coronary angiography. Blood samples for measuring of CK-MB and cTnI were collected at 4-h intervals during the first 24 h, 12-h intervals until 48 h, and 24-h intervals until fourth days after hospitalization. Echocardiography were performed before thrombolytic therapy in all patients.

1) The mean age of subjects was 63.6±11.5 years (range:44 - 84 years) and 11 patients were men and 5 patients were women. The site of infarction was anterior in 11 patients and inferior in 5 patients. 2) The peak concentrations of CK-MB and cTnI were reached from 4-h to 12-h after admission in all patients (7.3±2.6-h, and 9.0±3.1-h, respectively), but there was no significant difference in peak time. 3) Serum concentration of CK-MB was normalized at 72-h after admission, but cTnI was remained in increased state until 96-h after admission. The numbers of the patients with above cutoff value of CK-MB and cTnI at different time after admission were significantly different after 72-h (p<0.05). 4) The peak cTnI and sigma cTnI level were significantly correlated with peak CK-MB and sigma CK-MB level, respectively (r² =0.7955, p<0.0001 and r² =0.6378, p=0.0002, respectively). 5) The ejection fraction was not correlated with peak cTnI concentration (r² =0.0948, p=0.2461) and sigma cTnI (r² =0.1867, p=0.0946). 6) The wall motion score index was not correlated with peak cTnI concentration (r² =0.2135, p=0.0716), but significantly correlated with sigma cTnI (r² =0.2540, p=0.0465).

The serum concentration of cTnI was useful in late diagnosis of AMI and cTnI release in patients with AMI was correlated with myocardial infarct size.