To date, this possibility appears to be unrealistic. However, it has been postulated that, at least in patients with acute myocardial infarction, hemostatic plugs are likely to be older than the thrombi responsible for the acute occlusion of the coronary artery.
Kanamasa et al assessed in dogs whether the relative rate of lysis of fresh and old thrombi could be influenced by the rapidity of rt-PA administration. They found that 24-h-old thrombi were lysed to a significantly greater extent when the same 1-mg/kg dose of rt-PA was given over 180 min rather than 30 min. The capacity to lyse fresh thrombi was enhanced with the shorter rt-PA regimen. This finding, if confirmed in clinical situations, would allow a certain selectivity in directing bolus rt-PA administration toward thrombi with some extent of preservation of hemostatic plugs.
In conclusion, theoretical considerations and the available experimental and clinical data suggest that infusion of rt-PA over a short period of time would result in a favorable benefit-risk ratio. We have performed experimental studies to optimize bolus rt-PA treatment.
Strategies to Optimize Bolus rt-PA Treatment
In animal models, fibrin still accumulates on lysing venous thrombi during effective thrombolysis. It has become evident that success or failure of therapeutic thrombolysis depends on the balance between dissolution and formation of the thrombus, rather than on the intensity of fibrinolysis alone.