Summary
The relationship between lytic state variables and ex vivo clot lysability was investigated
in blood drawn from patients during streptokinase administration for acute myocardial
infarction. A lytic state was already evident after 5 min of treatment and after 20
min the plasminogen concentration had decreased to 24%, antiplasmin to 7% and fibrinogen
0.2 g/1. Lysis of radiolabeled retracted clots in the patient plasmas decreased from
37 ± 8% after 5 min to 21 ± 8% at 10 min and was significantly lower (8 ± 9%, p <0.005)
in samples drawn at 20, 40 and 80 min. Clot lysability correlated positively with
the plasminogen concentration (r = 0.78, p = 0.003), but not with plasmin activity.
Suspension of radiolabeled clots in normal plasma pre-exposed to 250 U/ml two-chain
urokinase for varying time to induce an in vitro lytic state was also associated with
decreasing clot lysability in direct proportion with the duration of prior plasma
exposure to urokinase. The decreased lysability correlated with the time-dependent
reduction in plasminogen concentration (r = 0.88, p <0.0005). Thus, clot lysability
decreases in conjunction with the development of the lytic state and the associated
plasminogen depletion. The lytic state may therefore limit reperfusion during thrombolytic
treatment.
