The EVR valve is a transcatheter aortic bioprosthesis that is self-expanding. Compared to the Medtronic CoreValve (CV), the EVR has a smaller entry vessel and a lower insertion profile. These characteristics provide improved vascular access, making it possible for transfemoral treatment in patients with difficult iliofemoral anatomy.
The EVR has a chamber 82 which selectively communicates with the air inlet 38 via a central bore 36. The chamber is sized to limit lateral movement of the armature 46. This allows for the establishment of a balanced vacuum within the chamber. A damping ring 110 is sized to attenuate the vacuum signal supplied to the vacuum regulator valve 14. It also reduces the oscillation of the diaphragm valve assembly 92.
The EVR valve is controlled by the engine control unit 22. It has a solenoid assembly 24 which exerts a magnetic attractive force on the armature 46. This force is activated by a preloaded armature spring. The amount of force exerted by the spring is adjusted to the minimum flow rate required at the “start-to-open” duty cycle. This preload is a critical element in the sensitive calibration of the device.
A damping ring 110 is sized and designed to attenuate the vacuum signal supplied by the vacuum regulator valve. The ring contains one or more damping orifices 120 which are sized to reduce the pressure within the chamber.
The EVR valve can be dismantled and the internal parts replaced for service. A test drive can be performed to check the performance of the device. Before testing the device, remove the vacuum hose and diaphragm. If the EVR is positioned at a supra-annular position, the test can be done using a guidewire. The evr valve valve can be recaptured during the test.
The EVR valve has a lower incidence of mild paravalvular regurgitation compared to CV. In addition, the EVR device has a higher success rate. The presence of more than mild aortic regurgitation was reported to have a negative effect on the prognosis of the patient. This has resulted in the need for more permanent pacing. Having a more streamlined range makes it more likely that the right valve will be available.
The EVR valve can be installed and removed quickly and easily. Unlike conventional valves, it is not necessary to de-solder the valve. It is also easy to replace the internal parts when needed. The insertion profile of the EVR is much smaller than the CV, enabling transfemoral access. The device is compatible with various refrigerants.
The EVR has the potential to help prevent the incidence of new permanent pacemaker implantations. This is a positive development for patients who have been experiencing frequent need for permanent pacing. The EVR device may be used in patients with complex iliofemoral anatomy, which requires careful and precise implantation.
The long term clinical outcome of the device is good. This is especially true for the group that received the device on the first attempt. The second trial was carried out in January 2013 and resulted in more successful devices. The clinical outcomes for these patients were similar to those in the CV group. However, the EVR prosthesis has a shorter insertion profile and is more suitable for challenging anatomy.