Application of shape memory alloy pressure-controlled vascular clamp for atraumatic vessel occlusion

Background: To realize atraumatic vessel occlusion, a new hemostatic clamp using superelastic shape memory alloy (SMA) as a pressure control limiter has been proposed. It was designed taking advantage of a unique mechanical property of SMA. The ability to control pressure with the newly designed SMA clamp was investigated. The traumatic effect on vessel walls was evaluated in order to confirm the SMA clamp's biological effect of protecting vessels from damage. Methods: Twenty-four pig thoracic aortas were divided into four groups: SMA group 1 (0.3 mm diameter SMA wire used), SMA group 2 (0.4 mm diameter SMA wire used), base model group (hemostatic clamp of Mimura type), and a control group. The biomechanical interaction between the pressure-controlled clamp and animal aortas was evaluated with a micropressure analyzing system. The atraumatic effect of the SMA clamp was examined on pig thoracic aortas in vitro and compared with that of its base model. The morphological injury of each vessel was evaluated after being clamped for 15 min. Results: Pressure saturation was shown in the displacement-pressure curve of the SMA clamp. In both SMA group 1 and SMA group 2, except for a slight imprint of compression in the intima, no obvious injury was observed, while in the base model group the endothelial laceration was observed when the clamp was closed to notch I. More serious injuries in the endothelial intima and media were observed when the clamp was closed to notches II and III. Conclusion: The effect of pressure-controlling SMA clamps on the in vitro vessel model was evaluated. Histological observation and the traumatic score proved that the safety of the clamps was improved with the new design of pressure control. This technique supplies an effective and applicable way of realizing atraumatic clamping.