PERCUTANEOUS AORTIC
`VALVE REPLACEMENT
`
`The aortic valve is a structure whose function is to direct the flow of blood from the left ventricle
`
`lt accomplishes this function by opening during the
`into the systemic circulation through the aortic artery.
`contraction of the left ventricle and closing when the left ventricle relaxes. The aortic valve is a tricuspid
`structure and each cusp folds up toward the aorta during the contraction phase and then fold back against
`each other in the relaxation phase. (figure 1 shm ' a picture) However, the aortic valve is a complex
`structure with integral relationships beyond merely a three leaflet valve. For instance, each leaflet sits
`directly opposite an outpouching of the proximal aorta. This dilated segment is called the sinus of valsalva.,
`and it is this anatomic relationship that assist the valve to open and close repetitively while minimizing the
`stress upon any point within this valvular apparatus. Further, the proximal porion of the aortic valve is
`highly elastic and with this elasticity it can dilate during the contracion phase of the left ventricle.
`Historically. it has been theorized that this reduces the amount of work that the left ventricle performs. As
`with anything in nature it is much more complex. The valvular structures are integrally related to the
`coronary arteries. The function of the coronary arteries are to supply blood supply to the heart. These. as
`represented in figure 2, are located within 2 of the sinuses. In a normally functioning valve, the cusps
`open widely to allow the unimpeded transference of blood, and then close tightly not allowing any to
`regurgitate back into the left ventricle. When there is significant restriction to blood flow, this is called
`stenosis and when it allows blood back into the left ventricle it is regurgitation. Thus, each component
`plays a vital role in the function and durability of the valve.
`The first components of the valve 1 would like to discuss are the leaflets. Interestingly. the
`number of the leaflets within a normal aortic valve does not vary to a significant degree. When there are
`less than three valves. the valve undergoes rapid stenosis and restriction. Among congenital alterations
`upon the valve number the most frequently encountered is a bicuspid aortic valve. This condition is the
`most common defect that is survived into adult hood. However, this valve predictably becomes more and
`more stenotic and regurgitant by the 4‘h and 5"h decade. Unfortunately, this usually results in the need for
`surgical replacement. A unicusped valve rarely survives beyond the first year of life. (figures 3 and 4).
`Rarely a quadricusped valve will be shown to survive into adulthood. This design also results in marked
`stenosis.
`Further, the cusps are shaped in a defined convexity. This design permits the dispersion of
`pressure over a larger surface area. This dispersion resists the exhaustion of the valve in any one particlular
`place. Moreover. this curvature allows the leaflet to reverse curvature. An ability needed in order to fold
`and allow the maximum opening diameter during contraction. Finally; a curved design allows a
`redundancy in thc coaptation site of the leaflets. The area of coaptation is the edge of the valves that must
`meet and close in order for there not to be regurgitation. Hence, both the number of leaflets and their
`overall shape is important in the function and durability of the valve.
`
`As mentioned earlier. the valve leaflets have a direct relationship to the sinus’s of valsalva. The
`sinus diameter is almost twice that of the aorta. This cavity plays an important role in the mechanism of
`valve closure (referenced Mano Thubrikar). A11 oblique section through the leaflet-sinus assembly shows
`this remarkable relationship. (figure4) . This section reveals that the sinus and leaflet form a circle when
`the valve is in a closed position. Furthermore, it is angulated to a degree as to allow pressure transduction
`along the entire surface of this unit. This suggest that the shape of the leaflet~sinus assembly is important I
`determining how stresses are developed within the valve.
`it is also this relationship that allows the valves
`to close without pulling upon the aortic valve as has been suggested. Finally, this relationship of the
`sinuses and valve allow for the proper flow of blood in the coronary ostia.
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`NORRED EXHIBIT 2047 - Page 1
`Medtronic, Inc., Medtronic Vascular, Inc.,
`& Medtronic Corevalve, LLC
`
`v. Troy R. Norred, MD.
`Case |PR2014-00110
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`NORRED EXHIBIT 2047 - Page 2
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