- Troponin T and I assays show decreased concentrations in heparin plasma compared with serum: lower recoveries in early than in late phases of myocardial injury. Gerhardt, W., Nordin, G., Herbert, A.K., Burzell, B.L., Isaksson, A., Gustavsson, E., Haglund, S., Müller-Bardorff, M., Katus, H.A. Clin. Chem. (2000)