The Half-Life of Long Forms of Cardiac Troponin T.

BACKGROUND: Long forms of cardiac troponin T (cTnT) are promising markers that may differentiate myocardial infarction from other causes of acute and chronic myocardial injury. However, to understand the clinical utility of long cTnT, knowledge of the half-life (T½) is key. By using auto-transfusion in humans we determined the T½ of long forms of cTnT and compared long cTnT to a commercial high-sensitivity total cTnT assay. METHODS: Patients with ST-segment-elevation-myocardial infarction were included within 24 h after revascularization and underwent plasmapheresis to obtain plasma with a high cTnT concentration. After at least 3 weeks, patients returned for an autologous plasma re-transfusion followed by repeated blood sampling. A novel assay measured long cTnT and a commercially available assay measured total cTnT. RESULTS: We included 17 patients with median age 63 years (25th-75th percentiles 59-70), and 4 (24%) were female. The median concentrations after transfusion were 99 ng/L (54-125) for long cTnT vs 252 ng/L (233-322) for total cTnT. The median ratio of long cTnT to total cTnT was 0.39 (0.26-0.55) after transfusion and declined to 0.30 (0.20-0.44) after 60 min. Long cTnT displayed a 2-phase exponential decay, similar to what was observed for total cTnT but with shorter T½ both for the distribution phase [16 min (11-18) vs 22 min (20-24), P < 0.001] and the elimination phase [103 min (78-125) vs 133 min (114-168), P < 0.001]. CONCLUSION: The elimination of long forms of cTnT was faster than for total cTnT following re-transfusion. This understanding could aid in differentiating myocardial infarction from other causes of acute and chronic myocardial injury.