Redesigning RHVs for Ischemic Thombectomies

Within their lifetimes, 1 in 4 adults over the age of 25 worldwide can expect to suffer a stroke–a blood clot which blocks the flow of oxygen to regions of the brain, causing loss of motor function or death if left untreated. In this project, our team works with the biomedical firm Imperative Care to optimize an existing suite of equipment for a stroke treatment called ischemic thrombectomy, in which a series of nested catheters which are inserted into the patient’s arterial tract at the groin, maneuvered to the location of the blood clot, and placed under aspiration via attachment to an external vacuum pump. Ideally, this results in either the ingestion and removal of the blood clot or it being corked at the catheter’s tip. Our focus concerns the functionality of the external valves that interface with these catheters, called rotating hemostatic valves (RHVs). The RHV’s intended function is to seal off the vacuum pressure inside each catheter from the atmosphere, while also allowing the surgeon fine control of the position of the catheter. In the case that vacuum pressure is not maintained in the catheter, the blood clot can become irretrievable and/or the surgery can become prolonged, resulting in potential neurological damage to the patient. Mitigation or elimination of this scenario was the primary technical requirement of our redesign.
Testing determined that vacuum pressure is gradually lost due to a taper at the catheter’s tip, partially re-pressurizing the RHV as the catheter is pulled out, if the gasket seal is not tightened enough. Our team then designed a prototype which incorporates an integrated, one-way ball valve, an ACME threadform, a smaller length than most existing models, and a texturized user-interface for gasket adjustment. The main redesign is the placement of the one-way ball-valve, which functions like an airlock: the physician retracts a catheter into the RHV, seals off all catheters still in use from the environmental pressure by turning the valve, and then can fully remove the desired catheter without any possibility of impacting upstream pressure. The physician can then re-insert the catheter by opening the one-way ball valve at their discretion.
The final prototype was manufactured with SLA 3D-printing and then evaluated testing: most tests were successful, with the exceptions likely resulting from wear on the prototype over repeated trials. While the resultant product is not immediately ready for implementation, successful proof of concept testing has been thoroughly demonstrated. If implemented, our RHV design could well improve surgical outcomes of ischemic thrombectomy.