Mechanical versus chemical thrombolysis: an in vitro differentiation of thrombolytic mechanisms.

PURPOSE

To assess differing mechanisms of thrombolysis determining time to reperfusion, completeness of thrombus dissolution, and embolic potential.

MATERIALS AND METHODS

An in vitro perfusion model designed to mimic arterial flow conditions was created. Bifurcated limbs allowed continuous flow through one channel and the placement of radiolabeled (iodine-125) thrombus housed in a 5-cm segment of polytetrafluoroethylene graft in the other. The three experimental groups consisted of a standard continuous urokinase infusion, a pulsed pressurized injection of saline, and a similar injection with urokinase. A continuous infusion of 5% dextrose served as a control group. Time to reflow (as assessed with ultrasonic flow monitoring), completeness of thrombus dissolution (I-125 liberated into solution), and the number and size of embolic particles produced (detected by a series of graduated filter sizes) were analyzed.

RESULTS

Time to reflow was significantly faster for both groups when pressurized injections were used (P < .001). There was no reflow in the control arm at 90 minutes. Completeness of thrombus dissolution was higher when a continuous infusion of urokinase was used in comparison to either of the power injection groups or the control (P < .05). The amount of embolic debris produced was significantly lower with a continuous infusion of urokinase compared with either of the power lysis groups (P < .05), but significantly greater than the control arm (P < .001). The size of the embolic particles in the power pulsed lysis groups was significantly decreased by the addition of urokinase (P < .05).

CONCLUSIONS

Reflow is more rapidly established by the use of mechanical means. However, a less complete dissolution of thrombus in conjunction with a greater amount of embolic debris is achieved with this approach. The size of the embolic particles produced is reduced by the addition of a thrombolytic agent.