FACTORS INFLUENCING THE LYSIS OF EX-VIVO HUMAN THROMBI

The lysis of human ex vivo thrombi was studied in vitro in relation to their age, the thrombolytic agent (streptokinase, urokinase or t-PA), the thrombolytic milieu (plasma or buffer) and the addition of lys-pl asminogen (lys-p/g). Fourteen arterial and 16 venous thrombi were obta ined at autopsies or operations. The probable thrombi age was estimate d by the time interval from the onset of clinical symptoms and in vivo imaging to removal. Pieces of the thrombi, weighing approximately 250 mg, were exposed to lysis in 2 ml volumes of plasma or buffer; and th e extent of lysis was measured by the decrease of the wet weight of th rombi over a period of 24 h. A nonsignificantly better lysis (from 5-1 5% with different agents) was found in fresh arterial and venous throm bi (age of less than 1 week, median value 2 days) in comparison to age d thrombi (older than 1 month, median value 9 weeks). All three thromb olytic agents were equally effective towards fresh and aged thrombi. T he substitution of consumed plasminogen by lys-plg improved the lysis; excellent improvement was obtained when intermittent addition of acti vator and lys-plg was applied. Finally, we found that lysis of ex vivo thrombi in buffer milieu significantly exceeded that in plasma milieu . In conclusion, the general belief in the decrease of thrombus lysabi lity during the course of several months ageing was not confirmed by t his study. The lysis of ex vivo thrombi could be substantially improve d by supplementing consumed plasminogen or by replacing lytic milieu f rom plasma to buffer. These findings in ex vivo thrombi might have pot ential value for the improvement of clinical thrombolysis.