Cumulative troponin T release after acute myocardial infarction. Influence of reperfusion

For troponin T a characteristic biphasic change in the plasma time-concentration curve has been described, especially in patients with early reperfusion after thrombolytic therapy. As troponin T is bound to myofibrillar structures, treatment strategy or treatment outcome could influence the cumulative plasma release of this protein in a different way compared to the cumulative release of free cytoplasmic cardiac enzymes. The present study is the first study comparing the total quantity of troponin T released by the heart during the first 168 hours after acute myocardial infarction, both in patients treated with thrombolytic therapy (n = 16) and in patients not treated with thrombolytic therapy (n = 7). On the basis of clinical symptoms and coronary arteriogram within 24 hours, the patients treated with thrombolytic therapy were divided into two groups, reperfused (n = 9) and non-reperfused (n = 7). In the patients not treated with thrombolytic therapy, absence of spontaneous early reperfusion was judged only from clinical symptoms. Cumulative troponin T release into plasma was compared to the cumulative release of the cytoplasmic cardiac enzymes creatine kinase (EC 2.7.3.2) and hydroxybutyrate dehydrogenase (EC 1.1.1.27). Cumulative release, i. e., infarct size, was calculated using a two-compartment model for circulating proteins. Mean tissue contents, per gram wet weight, of 156 U/g for hydroxybutyrate dehydrogenase, 2.163 U/g for creatine kinase and 234 microg/g for troponin T, were used to express infarct size in gram-equivalents of healthy myocardium per litre plasma (g-eq/l). Release rates were represented by the ratio of cumulative quantities released in 10 hours and 72 hours for creatine kinase and hydroxybutyrate dehydrogenase and in 10 hours and 168 hours for troponin T.

- Plasma time-concentration curves and release rates of troponin T in patients treated with thrombolytic therapy showing reperfusion differ significantly from those of patients not treated with thrombolytic therapy, showing no reperfusion. - Creatine kinase and hydroxybutyrate dehydrogenase release is completed within 72-100 hours in all patients, whereas troponin T release still continues after 168 hours. - Cumulative troponin T release at 168 hours is only a fraction (around 8%) of cumulative cytoplasmic enzyme release and the percentage released is not influenced by the treatment strategy or outcome, i. e., vessel patency. - Although troponin T release is only a fraction of the cumulative enzyme release (infarct size) there is a highly significant correlation between both, independent of the treatment strategy or treatment outcome.