DEVELOPMENT OF THE ENDOVASCULAR THROMBOLYSIS SYSTEM WITH SHOCK WAVE

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Background and ObjectiveThere are several problems inherent in the treatment of cerebral embolisms, such as the narrow therapeutic time window and the severe side effects of fibrinolytic drugs. It is thusnecessary to develop a new method of removing a cerebral thrombus more rapidly using smaller amounts of fibrinolytics. In the present, we investigated a liquid jet induced by holmium (Ho) : YAG laser irradiation in water.Materials and MethodsIn this study, a pulsed Ho : YAG laser whose wavelength, pulse duration, and energy were 2.1 μm, 350 μs, and 350 mJ/pulse, respectively. Behavior of Ho : YAG laser induced bubble in a capillary tube filled with pure water was observed at various stand-off distances (L ; distance between the optical fiber end and the capillary exit). After that, a liquid-jet generator was made by insertion of an optical fiber (diameter : 0.6 mm) into a catheter (6Fr) filled with pure water. The maximum penetration depth of a liquid jet generated with this device int … More o a gelatin artificial thrombus was measured at various stand-off distances (L ; destance between the optical fiber end and catheter exit). Moreover, the phenomenon and the pressure around the catheter were observed with a shadowgraph and PVDF needle hydrophon, respectively. Based on these results, a stand-off distance of 13 mm was chosen to investigate the enhancement of urokinase (UK) efficacy by only a single operation of the liquid-jet device in artificial thrombi made of human blood.ResultsA laser-induced bubble in a capillary tube rapidly grew forward and generated a liquid jet. Maximum penetration depth with the liquid-jet generating catheter increased in proportion to L and reached a maximum value (9 mm) when L was around 13 mm. A shock wave whose overpressure at a point several mm away from the catheter exit was over 12MPa was captured with shadowgraph Fabrinolysis rates (%) after incubation with a small amount of UK for 10 min and 30 min were predominantly raised by a single use of the laser-induced liquid jet (5.4 ± 2.4 vs. 22.6 ± 6.1 and 7.3 ± 3.8 vs. 38.3 ± 5.6, respectively (mean ± SD, p<0.001)).ConclusionsHo : YAG laser irradiation within a capillary tube filled with water caused liquid jet formation, which promoted the effect of fibrinolytics. Moreover, this jet was accompanied with shock waves, which might enable to facilitate endovascular balloon angioplasty by cracking subintimal calcified lesions. The liquid jet generation system is so simple that will be applied to an endovascular system for cerebral fibrinolysis in the near future. Less