- Argatroban, bivalirudin, and lepirudin do not decrease clot propagation and strength as effectively as heparin-activated antithrombin in vitro. Nielsen, V.G., Steenwyk, B.L., Gurley, W.Q., Pereira, S.J., Lell, W.A., Kirklin, J.K. J. Heart Lung Transplant. (2006)