IMMUNOELECTROPHORETIC CHARACTERIZATION OF SYSTEMIC FIBRINOGEN DURING THROMBOLYSIS OF PERIPHERAL ARTERIAL EMBOLI WITH tPA

Prompted by uncertainties over the possibility of ex-vivo alterations of fibrinogen in plasma samples from patients receiving thrombolytic agents, we sought to 1) use sodium dodecyl sulfate (SDS) and mild acidification to pH 5 as a general means for inhibiting post-sampling proteolysis, and 2) assess the chemical state of fibrinogen by immuno-electrophoretically profiling the molecular weight distribution of the fibrinogen-related antigens in the sample. Blood samples taken into EDTA and PPACK were immediately centrifuged, and plasma diluted 5X in 2% SDS and 0.04% monochloroacetic acid. Such samples showed no changes in molecular weight distribution of fibrinogen-related antigens over 7 days storage at room temperature when analyzed by SDS-eleetro-phoresis on 3% glyoxyl agarose foHowed by fixation with NaCNBHg₃ and staining with fluorescent, affinity-purified anti-fibrinogen antibody. The method of study was applied to 16 patients with occlusive peripheral arterial emboli, all of which were successfully treated by catheter-directed administration of tissue plasminogen activator (tPA). All patients presented abnormally high levels of degraded (predominantly 170-300 kD) and dimeric forms of fibrinogen both prior and subsequent to treatment, and only 3 of the 16 patients underwent appreciable change in content or composition of fibrinogen derivatives in course of treatment. Concentrations of dimers ranged from 6 to 23 percent of the total fibrinogen. De novo elevations in degraded forms of fibrinogen observed to accompany treatment of 3 patients were reflected in prolongation of thrombin time while tests of sulfite precipitation underwent relatively minor change. The more frequent absence of change in content of derivatives, particularly the dimeric forms suggestive of a coagulopathic process, indicated that they were derived systemically rather than from the occluding thrombus that was removed by treatment. The findings raise a prospect that the clinically significant thrombosis in these patients may be symptomatic of a much more generalized vascular coagulopathic process. The absence of measurable change in molecular composition of fibrinogen-related antigens in course of successful treatment of these patients attests to the efficacy of tPA as a thrombolytic agent. Support: NIH Grants HL-19361 and HL-19767.