PREVENTION OF ARTERIAL REOCCLUSION AFTER THROMBOLYSIS WITH RECOMBINANT LIPOPROTEIN ASSOCIATED COAGULATION INHIBITOR

Background. This study was designed to determine whether arterial reocclusion after thrombolysis can be prevented by lipoprotein-associated coagulation inhibitor (LACI), a physiological inhibitor of tissue factor-induced coagulation mediated by the extrinsic pathway. Methods and Results. Thrombosis was induced in femoral arteries of anesthetized dogs with the use of anodal current to elicit extensive vascular injury and formation of platelet-rich thrombi in one artery and with thrombogenic copper wire to elicit fibrin-rich thrombi without appreciable vascular injury in the contralateral artery. Recanalization of both vessels was induced with t-PA (1.7 mg/kg i.v. over 1 hour) and verified with Doppler flow probes. Reocclusion occurred within 2 hours in seven of seven arteries with electrical injury-induced thrombosis and in four of seven arteries with copper wire-induced thrombosis in the absence of LACI. In dogs given infusions of recombinant DNA-produced LACI (225-mu-g/kg over 15 minutes, followed by 4-mu-g/kg/min i.v.) after completion of the infusion of t-PA, no reocclusion occurred during the 2-hour interval of observation in any of the five arteries subjected to electrical injury (p < 0.001), and cyclic partial occlusions were nearly abolished (0.4 +/- 0.4/hr in LACI-treated dogs compared with 13.7 +/- 5.5/hr in saline-treated dogs, p < 0.0001). In contrast, reocclusion occurred in two of five arteries with indwelling copper wires, and cyclic partial occlusions were unaffected despite LACI. LACI prolonged the partial thromboplastin time modestly (1.7 +/- 0.2 x baseline) but did not affect platelet counts or aggregation assessed ex vivo. Conclusions. Inhibition of the extrinsic pathway of coagulation with LACI prevents thrombotic arterial reocclusion after thrombolysis in vessels subjected to extensive vascular injury. Our results demonstrate that activation of the extrinsic pathway plays a critical role in thrombotic reocclusion and that LACI provides a highly targeted approach to facilitate sustained recanalization without directly inhibiting platelets.