ANTIBODIES AGAINST THE FIBRIN BETA-CHAIN AMINO-TERMINUS DETECT ACTIVECANINE VENOUS THROMBI

Background This study was performed to determine whether antibodies ag ainst the amino-terminus of the beta-chain of fibrin (anti-beta) could noninvasively distinguish actively enlarging thrombi from thrombi sta bilized with anticoagulants. Methods and Results Dogs with unilateral femoral vein thrombi were allocated into three groups: (1) no anticoag ulation, (2) intravenous heparin maintained in the ''therapeutic'' ran ge (0.2 to 0.5 U/mL plasma), and (3) ''excess'' heparin, maintained at >1.0 U/mL plasma. Thrombolysis was suppressed with tranexamic acid. I n-111-labeled anti-beta was infused, and gamma scans of the legs were performed at regular intervals for 24 hours. Scans were interpreted in a blinded fashion. In addition, for each scan, the number of gamma co unts from the femoral area on the thrombosed side was compared with th e contralateral side. Clot/blood isotope density was determined postmo rtem. Leg thrombi in the noanticoagulation group were 100% detectable, mean (+/-SD) relative count in the thrombosed femoral area was 186% ( +/-30%) of the contralateral side, and clot/blood ratio was 14.7 (+/-2 .0). Thrombi in the therapeutic heparin group were only 75% detectable , relative counts in the thrombosed femoral areas decreased to 125% (/-20%), and clot/blood ratio declined to 11.3 (+/-3.5). In the ''exces s heparin'' group, leg thrombi were only 50% detectable, the thrombose d femoral area had relative counts of 118%+/-17%, and the clot/blood r atio fell to 7.8+/-1.9. Conclusions Radiolabeled anti-beta noninvasive ly distinguishes propagating thrombi from those stabilized by anticoag ulants. They may be useful for detecting thrombosis clinically as well as for monitoring the efficacy of anticoagulation.