In order to attain complete seal of catheter sheath hole just after catheter intervention, we applied laser welding technique. We employed combination of diode laser (wavelength: 810nm) irradiation and indocyanine green stain to enhance heat generation on the stained surface. We studied laser sealing of catheter sheath hole on an ex vivo vascular model using porcine carotid artery.
We successfully demonstrated the sheath hole closure in this welding in the model with 1.8W, 8s diode laser irradiation. In this case, we estimated 78 °C of the maximum temperature at welding surface by thermal conduction calculation. Collagen fiber melting was found in welding region.
To know vascular wall at the fiber tip to perform laser welding in blind procedure, we constructed fiber-optic backscattering light measurement system. We used green He-Ne laser light (543nm) to distinguish hemoglobin concentration in the tissue. We obtained tissue discrimination at fiber tip in blind procedure. We think our particular laser welding in combination with novel tissue discrimination technique at the fiber tip may attain the catheter sheath hole closure with sufficient mechanical strength in blind procedure.
To develop the catheter-based laser vascular welding device against aortic dissection, we studied fundamental characteristics of the laser vascular welding for aorta dissection model in vitro with the scattering light monitoring to obtain welding proceedings. We employed the laser vascular welding by means of the combination of the diode laser irradiation and indocyanine green (ICG) stain to the dissected vessel surface in a swine aortic dissection model to obtain localized heat generation on the surface. The forward and backward scattering lights of the diode laser from the welding portion were measured during the laser irradiation. The breaking stresses of the welded aortic pieces were measured. The breaking stress of 170gf/cm2 obtained with the 425W/cm2, 2.4s irradiation may be strong enough to the successful therapy for aortic dissection regarding to the dissecting force caused by blood flow. By analyzing forward and backward scattering lights, we could observe the occurrence of water evaporation in the welding portion, the bleaching of the ICG and the carbonization of the welding portion. Then we could monitor the proceedings of the welding process. The temperature estimation of the welding portion and the microscopic observation revealed that the mechanism of our welding may be basically elastic fiber entwining. We think our vascular welding with the scattering light monitoring of the welding process has the potential to apply catheter-based therapy for aortic dissection.