The EVR valve is a self-expanding transcatheter aortic bioprosthesis designed by Medtronic. Its new design reduces paravalvular leaks, has an extended sealing skirt, and offers a lower insertion profile for transfemoral access in challenging anatomy. It also has an improved rate of device success. A long-term follow-up is needed to determine the effectiveness of this device.
The EVR valve is a two-part system composed of a bobbin and an encapsulated solenoid assembly. The bobbin is made of non-magnetic nylon-tape material. It has a central bore 36 and a magnetic pole piece 34 that extends through the hollow central core of the bobbin. The central bore provides a communication pathway between the bobbin and the EVR chamber 82. The inner diameter of the lower connecting flange 78 of the solenoid housing 72 is greater than the diameter of the armature 46.
In the closed valve position, a preloaded armature spring urges the armature toward the open valve position. At low duty cycles, the output flow is non-linear. This is because the movable diaphragm valve assembly is urged downward by the coil spring. This is a common characteristic of conventional flow regulators. It is necessary to precisely calibrate the flow regulator to ensure that the output is within a specified range. This process may require the use of an electronic flow regulator. These regulators are available in a number of different designs. They can be configured to accommodate net build EVR valves.
The armature has a series of radially-spaced notches 86 along its peripheral edge. A thin layer of adsorptive material 45 is disposed over the armature. The outer diameter of the armature is 18F, which is much smaller than the 22F diameter of the 18F sheath used for CV implantation.
The EVR valve is connected to the vacuum regulator valve 14. A bobbin is inserted into the upper valve housing 26. The armature of the valve is secured to the encapsulated solenoid assembly 24. The lower connecting flange 78 is retained in an external cavity 80 in the upper valve housing.
The encapsulated bobbin has an air inlet 38 and a vacuum inlet 37. The vacuum inlet 37 is a passageway for the air flowing in from the atmosphere. The evr valve valve is actuated by the air flow passing through the EVR chamber 82. The vacuum pressure tends to maintain the armature 46 in the “open” valve position.
The encapsulated bobbin is encapsulated in a circular-shaped cavity defined by the inner diameter of the lower connecting flange of the solenoid housing. The armature is enclosed by an annular filter ring 170 that attenuates the vacuum signal supplied to the vacuum regulator valve 14. The vacuum inlet is also a passageway for the air flowing out of the reference chamber 108. The damping ring 110 is positioned above the vacuum inlet and inhibits oscillation of the movable diaphragm assembly 92. The valve is designed to be actuated at a minimum flow rate during the “start-to-open” duty cycle.