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2019-02-28

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AVNeo (Aortic Valve Neo-cuspidization)

Introduction

AVNeo seeks to provide a biocompatible treatment for aortic valve disease. Aortic valve disease is conventionally treated surgically with a prosthetic valve. Prosthetic valves are costly, leading to a worldwide economic burden on healthcare. The durability of biological valves are also still under question. The largest effect to patients following mechanical valve operations is the need to take anticoagulant drugs for the rest of their lives, causing great strain on quality of life. The popularity of TAVR is also on the rise, but facility startup costs, post procedural complication management issues, continue to present resistance to its position as a “go to” treatment for aortic valve disease.

History

AVNeo (Aortic Valve Neo-Cuspidization) started in Japan from 2007. The treatment has been carried out worldwide with 2000+ cases. Favorable outcomes have been reported in conference presentations and articles (Ref. 1 and 2).

The initial cases are nearing 10 years (Ref. 2). Currently, more than 40 facilities in Japan, and more than 20 facilities globally have started AVNeo and the numbers are increasing.

The concepts of AVNeo

Use of autologous pericardium

＊ No immunal rejection issues with autologous pericardium
＊ Stronger leaflet when using autologous pericardium
＊ Reasonable price

Calcification is less likely to occur using autologous tissue.

Dialysis patients are prone to valve calcification. However, there is one report of no calcification in dialysis patients who underwent AVNeo (Ref.3). In an ex-vivo study, the strength of glutaraldehyde-treated autologous pericardium is reported to be about 4 times higher than other valves (Graph: Ref.4).

Preserved physiological movement of the aorta

The AVNeo seeks to preserve the natural movement of the aorta. When the aorta contracts and expands during a cardiac cycle, the aortic leaflets also contract and expand in a dynamic movement.
The video below depicts the natural movement of the aorta.

• • 1．Following the AVNeo procedure, the annulus expands with the expansion of the aorta, ensuring a larger effective valve area. Postoperative low pressure gradients are maintained even in narrow annulus.

• • 2． When the valve closes, returning flow is absorbed in the entire aortic root, thus mechanical stress is on the leaflets is reduced.

There is no natural movement with prosthetic valve replacement surgery. Natural contraction and expansion of the aortic root is lost, because movement of the annulus is fixed. As a result, the effective valve area is reduced and postoperative pressure gradients are higher compared to cases where AVNeo were performed (Ref 5).

The following is an echo video of a normal aortic valve (left), an echo image of an aortic valve following AVNeo (right). (Spectrum tracking analysis of the annulus) There are no significant differences.

Valve design—Less likely to cause postoperative of AR

In most cases, the height of commissures and the height of leaflet contact points in normal valves vary from patient to patient; even between patients with similar annular diameters.

• • • If the contact point of leaflet is low → free edge is longer (Blue line)
    • If the contact point of leaflet is high → free edge is shorter (Orange line)

Since the leaflet’s contact points and the height of each commissure are on the same plane, “the distance of each commissure” and “distance of the free edge of the leaflet” corresponds 1:1. Therefore, free edge distance can be determined easily by measuring commissural distance.

On the other hand, the lengths of each leaflet and the proportions differ for each individual. The free edge of the leaflet should be carefully constructed adjusting the height when suturing in order to make the three leaflets the same height. Therefore, it is possible to achieve longer cooptation, and postoperative AR is less likely to occur.

Overview of Step by Step AVneo Procedure (details to be provided during actual training)

• • • 1．Harvesting autologous pericardium

      Harvest a section of 7 cm x 8 cm autologous pericardium. The pericardium is affixed to the provided plate with slight tension using sutures. Adipose tissue is removed from the harvested pericardium.

• • • 2．Glutaraldehyde treatment

      The harvested pericardium is placed on the plate with visceral surface facing the plate, and the rough surface upward. The pericardium is affixed with slight tension in order to prevent wrinkling following chemical fixation with glutaraldehyde. Remove fat tissue from the autologous pericardium, and immerse in glutaraldehyde (0.6%) for 10 minutes.

• • • 3．Rinsing process

      Remove the pericardium from the plate, and rinse the glutaraldehyde in saline. Rinse for 6 minutes, 3 times (total 18 minutes).

• • • 4．Measuring the distance between commissures

      Clamp the aorta, expose the aortic valve, then remove the leaflets. Use the Sizer to measure the commissures.
      During the sizing process, align the edge of the sizer to the position of the commissure, repeating for all commissures. It is important to stay close to the aortic wall when sizing. Repeat the measurement until the 2 edges of one sizer matches 2 commissures (or the extension line). After determining the size of each leaflet, mark the center of each leaflet on the annulus. Measure and note the sizes of the LCC, RCC and NCC.

• • • 5．Trimming pericardium

      Wipe off moisture from the rinsed pericardium with gauze, then place it on the included plate, with the rough surface facing the plate and smooth surface exposed.
      The three leaflets are designed using the included template, pen, paper (or sterilized paper ). Mark the paper using the template. The pericardium close to diaphragm is the thickest and is used to make a larger leaflet.
      After drawing the outer periphery, draw the “dot” on the extension wing, draw longer lines in the center of leaflet, and draw other “dots” in accordance with the template. Both sides of the leaflet must have 5mm wing extensions. Using the provided petri dish, soak the leaflets in saline until use.

• • • 6．Suturing leaflets

      The smooth surface, or marked side of the leaflets should face the left ventricular.
      The needle should follow the path:
      smooth surface of leaflet → bottom of annulus → top of annulus. (4-0 Proline TF)
      First, pass the needle though both the dot in the center of the leaflet and corresponding
      dot in the center of annulus. The suture is tied with three knots. Each bite through the leaflet should be at 5mm intervals, and at 1mm intervals on the annulus.
      At the point where the remaining portions for the leaflet become slightly longer or close to the remaining length of the annulus, the bites should become equidistant, 1:1 . A “big bite” should be taken at the second to last dot. The final suture on the cusp is always 5mm from the edge. After the needle passes through the last dot, straighten the needle using a needle holder. The needle should pass through the aortic wall 2mm below the uppermost point of the commissure.

• • • 7．Construct the commissure

      Construct the commissure using 4-0 Proline RB-1 (17mm, 90cm).
      The following four points must be penetrated – one midpoint between the free edge and the previous stitch (approx. 2.5mm from the edge) at a height near the native commissure, and also the sutured point at the at top corner of the wing extension.  Then the aortic wall must be penetrated with 4 sutures facing outside of the aortic wall. The distance between the two lower 2 penetration points for the pledgets is narrow; on the contrary, the distance between the 2 higher penetration holes for the pledgets is wider. It is important to make sure that the wings are securely attached to the aortic wall before knotting. After knotting 8 times on the upper sutures, lower sutures are knotted 8 times.

• • • 8．Completion of the procedure

      Repeat Step 6 (Suturing the Leaflets) and Step 7 (Constructing the Commissure) three times, and the procedure is complete.