WO2012024257A2

WO2012024257A2 - Braided aortic root graft and method of valve-sparing

Info

Publication number: WO2012024257A2
Application number: PCT/US2011/047849
Authority: WO
Inventors: John T.M. Wright
Original assignee: Genesee Biomedical, Inc.
Priority date: 2010-08-17
Filing date: 2011-08-16
Publication date: 2012-02-23
Also published as: WO2012024257A3

Abstract

Embodiments provide methods and apparatus for surgically replacing an aortic root without replacement of the aortic valve (a valve-sparing aortic root replacement procedure). The apparatus for use during such a procedure is an aortic root graft having a braided tubular graft structure and a woven tubular graft portion. Embodiments provide for grafting, by anastomosis, the braided tubular graft to remnants of the aortic wall to which the aortic valves are connected, or to remnants of the aortic valve leaflets. An adjustable circular band element is positioned and attached to the braided tubular graft structure at the level of the sino-tubular junction to define a circle of selected adjustable diameter. The woven tubular graft portion is subsequently anastomosed to each of the aorta and the braided tubular root graft structure. The diameter of adjustable circular band element is adjusted to ensure proper coaptation of the aortic valve leaflets.

Description

BRAIDED AORTIC ROOT GRAFT AND METHOD OF VALVE-SPARING

TECHNICAL FIELD

[0001] The embodiments disclosed herein are directed toward methods and apparatus for an aortic root graft procedure.

BACKGROUND

[0002] Valve-sparing aortic root replacement (also known as the David procedure) is a cardiac surgery procedure involving replacement of the aortic root without replacement of the aortic valve. Valve-sparing aortic replacement has evolved into an increasingly accepted alternative to composite replacement of both the aortic root and valve. Preservation of the native valve has the obvious advantage of obviating the need for anticoagulation therapy, and there is increasing evidence that it minimizes the overall incidence of valve-related

complications. Valve-sparing aortic root replacement is indicated where a patient has dilated sinuses of Valsalva, or effacement of the sinotubular (ST) junction with an ascending aortic aneurysm (or a combination of both).

[0003] In a conventional aortic valve sparing operation, diseased aortic and root tissue is excised. A short woven graft is trimmed to approximate the position, but not shape, of the sinuses and fenestratrations are made through the graft for the coronary "buttons." The relatively short woven graft is then sutured to the aortic root. Aortic remnants of the valve cusps are sewn to the root graft. A relatively longer woven graft is then anastomosed to the aorta. Subsequently, the longer woven aortic graft is then anastomosed to the shorter root graft.

[0004] When using a woven root graft, the surgeon has to judge the diameter of the sinotubular junction (STJd) correctly. If the STJd is oversized the aortic valve will be regurgitant and if the STJd is undersized buckling of valve leaflets occurs. Both defects usually need to be corrected before closing the patient.

[0005] The present invention is directed toward overcoming one or more of the problems discussed above.

SUMMARY OF THE EMBODIMENTS

[0006] An embodiment disclosed herein is a synthetic aortic root graft comprising a braided tubular root graft structure and a substantially circular band defining an adjustable circular diameter operatively associated with an exterior surface of the braided tubular root graft. The synthetic aortic root graft may further comprise a woven tubular aortic graft portion, which in use will be joined to the aorta away from the aortic root, and joined to the braided tubular root graft toward the root.

[0007] The adjustable circular band element may be implemented with any suitable band which may be positioned around the braided portion of the root graft at the level of the sino- tubular junction to define a circle of selected adjustable diameter. In one embodiment, the circular band comprises a linearly compressible tube around the graft and at least one suture operatively associated with the linearly compressible tube to provide for the reduction of the diameter of the circle defined by the band. The adjustable circular band element may be, but is not limited to, an adjustable circular band element as described in U.S. Application No.

12/693,193, published as U.S. Patent Publication No. 2010/0191254 Al, to Wright, filed January 25, 2010 entitled "Band Forming Apparatus," which is hereby incorporated by reference in its entirety.

[0008] In one specific example, the synthetic aortic root graft may be fabricated from a braided tubular material which may be formed and then heat set as a manufacturing step. In particular, the inflow portion and outflow portion of the graft may be initially set to have anatomically suitable diameters or cross sectional shapes for proper attachment to the relevant anatomical structures. In addition, a portion of the graft may be heat set into a desired complex shape. For example, the inflow portion of the root graft may be heat set into a shape which approximates the shape of typical normal sinuses of Valsalva.

[0009] Another aspect is a method of sparing an aortic valve by implanting an artificial aortic root graft. The method comprises providing a braided tubular root graft as described above, joining the braided tubular root graft to aortic remnants of the aortic valve leaflets and associating a band having an adjustable diameter with the outside of the braided tubular root graft at the level of the sino-tubular junction. The method further includes adjusting the diameter of the adjustable band, thereby adjusting the diameter of the braided tubular root graft to produce a desired level of aortic valve leaflet coaptation.

[0010] The described method may also comprise the steps of providing a woven tubular aortic graft, joining the woven tubular aortic graft to the aorta and joining the woven tubular graft to the braided tubular root graft.

[0011] Another aspect is a method of manufacturing a synthetic aortic root graft. This method comprises providing a length of low porosity braided tube suitable for heat setting, and configuring the braided tube to have an inflow diameter and an outflow diameter, wherein the inflow diameter is less than the outflow diameter. The method may also include heat setting the inflow region of the braided tube to approximate the shape of normal sinuses of Valsalva. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Fig. 1 is a front cross-section of a disclosed aortic root graft and associated anatomical structures.

[0013] Fig. 2 is a plan cross-section of the aortic root graft of Fig. 1 along the A-A plane, and associated anatomical structures.

[0014] Fig. 3 is a simplified schematic diagram showing the construction of a braided tube.

DETAILED DESCRIPTION

[0015] Unless otherwise indicated, all numbers expressing quantities of ingredients, dimensions reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about."

[0016] In this application and the claims, the use of the singular includes the plural unless specifically stated otherwise. In addition, use of "or" means "and/or" unless stated otherwise. Moreover, the use of the term "including," as well as other forms, such as "includes" and "included," is not limiting. Also, terms such as "element" or "component" encompass both elements and components comprising one unit and elements and components that comprise more than one unit unless specifically stated otherwise.

[0017] The disclosed embodiments include a novel device and novel surgical methods for aortic valve sparing operations in patients with degenerative aortic disease. The disclosed graft is suitable for use where the sinuses of Valsalva and portions of the ascending aorta are replaced but the aortic valve leaflets are preserved. The disclosed embodiments allow for simple adjustment of the sino-tubular diameter under post bypass transesophageal echocardiography (TEE) to achieve ideal leaflet coaptation. The disclosed methods and apparatus provide the first known approach to aortic valve sparing root reconstruction surgery which allows post bypass fine tuning adjustment under echo visualization to achieve an optimal sino-tubular diameter to optimize aortic valve function.

[0018] Fig. 1 shows a cross-sectional view of an aortic root 100 surrounding an aortic valve 125 provided with braided aortic root graft 105 including an adjustable constrictor, more particularly an adjustable diameter band 130 with drawstring 135 disposed therein, and a woven ascending aortic graft 115. Fig. 2 shows a cross-sectional plan view taken along the A-A plane of Fig. 1 As shown in Figs. 1 and 2, the disclosed aortic root graft 105 comprises one or more layers of low porosity braided tube 110 having a selected suitable inflow diameter. For example, in one embodiment, this may be a single layer, in another embodiment, this may be two layers, and, in other embodiments, this may be three or more layers. In one embodiment, a suitable inflow diameter is a 25 mm inflow diameter. The low porosity braided tube 110 also may be selected or formed to have a desired outflow diameter which is greater than the inflow diameter. For example, the low porosity braided tube 110 may be expanded in the outflow region to have a 32mm outflow diameter. The low porosity braided tube can be made of any suitable biocompatible, heat setable material, for example polyethertetraphylate (polyester).

[0019] As used herein, a braided tube is defined as a tube comprising fibers braided together. Typically, braiding involves interlinking fibers 310a in a helical or other pattern that extends substantially lengthwise along the perimeter of the tube 310, as shown in the highly simplified schematic representation of Fig. 3. The use of braided lengthwise fibers 310a to form a tube 310 ensures that a braided tube may have its diameter at a selected point along the tube length widened or reduced, within limits, without buckling.

[0020] The braided tube 110 may be fabricated from a material which can be heat set during manufacture, such as polyester. Thus, the low porosity braided tube 110 may be heat set during manufacture to have approximately the shape of three typical normal sinuses of Valsava. The tube 110 may also be outwardly flared above the sino-tubular junction. Because the graft is of braided construction, its diameter is readily adjustable, unlike a woven graft that is of a fixed diameter. In particular, a conventional woven graft generally involves fibers or threads that are woven together such that the fibers defining the tube walls cross each other, typically at right angles. Lengthwise elements are customarily called warp and crosswise elements are called weft, or filling. Because of the presence of crosswise fibers, the variability of the cross sectional diameter of a woven tube is limited by the elasticity of the weft, which is often quite limited for the materials used in the woven tubing of a conventional root graft. The dimensional stability of a woven graft is advantageous in certain instances, such as when joined to the aorta, where proper sizing is relatively straightforward and stability is important. On the other hand a woven graft significantly complicates or eliminates the possibility of fine tuning valve coaptation or advanced graft shaping techniques as described above. The braided aortic root graft 105 will also include an adjustable constrictor, which may be in the form or a band 130 which defines an adjustable circular diameter as described below.

[0021] A braided aortic root graft 105 prepared as described above may be implanted as follows: following excision of diseased tissue of the sinuses of Valsalva and the aorta, the aortic root graft 105 is sewn in place and the aortic remnants 120 of the valve leaflets are sewn to the braided braded tube 110 without regard to the final degree of leaflet coaptation. Some surgeons may prefer to implant the braided tube by attaching the aortic remnants to cylindrical bottom of the braided tube. Other surgeons may prefer to trim the bottom of the braided tube to match the aortic remnants. Should the surgeon prefer to cut the tube bottom to match the remnants, the surgeon should use heated cutting device that will cauterize the cut edges to prevent fraying of the cut portions. For example, a hot wire cutter might be used. The two coronary buttons are anastomosed. A conventional woven upper end 115 may be attached to or anastomosed to healthy aortic tissue as usual. The woven upper aortic graft 115 is then attached to or anastomosed to the braided tube 110. As used herein "anastomosed" contemplates attachment in any suitable manner, such as by sutures.

[0022] Prior to implanting the low porosity braided tube it may be pretreated to render impermeable to blood by known techniques. For example, the low porosity braided tube can be impregnated with a hemostatic agent such as collagen. Alternatively, a thin walled silicon rubber layer could be associated with the braided tube. As a further alternative, the braided tube could be preclotted by impregnation with a small amount the patient's blood prior to the bloods treatment with heparin or some other anti-coagulant.

[0023] In addition, an adjustable constrictor in the form of a substantially circular adjustable band 130 is placed on the outside of the aortic root graft 105 at the level of the sino- tubular junction. The adjustable band 130 defines a substantially circular diameter around the braded tube 110 of the braided aortic root graft 105. The adjustable band 130 may be any type of suitable band which provides for the adjustment of the substantially circular diameter defined by the band 130. For example, the adjustable band may be, but is not limited to a PTFE band containing a drawstring 135 as described in U.S. patent application 12/693,193, entitled BAND FORMING APPARATUS, filed January 25, 2010, the contents of which application are incorporated herein for all matters disclosed therein. The adjustable band 130 may be retained against the outer surface of the braided tubular aortic root graft 110 by a select number, for example, three equally spaced sutures 140 that encircle the band 130 and are attached to the aortic root graft 105 (see Fig. 1). The material from which the band 130 is fabricated may be tubular. In one embodiment, the band 130 will be fabricated from tubular PTFE having for example an outside tube diameter of 3.8mm, a lumen of about 1.8mm, and a length of about 90 mm. The band 130 will typically be linearly compressible. A small orifice 130a may be located in the wall of a tubular band 130 midway between its ends. In this specific band embodiment, the first end of a long size 2 braided polyester suture is threaded through the mid-orifice 130a with the help of a simple "U" shaped tool of 0.25mm diameter stainless steel wire (not shown) to exit at one end of the tube. The exiting first end of the long suture is passed around the braided aortic root graft 105 and using the "U" tool and inserted into the second end of the PTFE tube 130 to then emerge from the orifice 130a.

[0024] Pulling on the two suture ends causes the PTFE tube 130 to form a circular loop. Further tightening reduces the diameter of the sino-tubular junction as shown in Fig. 2. After placement of the adjustable diameter band 130, heart-lung bypass may be terminated, and under transesophageal echocardiography (TEE), the drawstrings 135 or comparable band diameter adjusting apparatus are adjusted to produce good leaflet coaptation and minimize aortic regurgitation. The drawstrings are then tied into a suitable knot 135a.

[0025] The disclosed devices and method have the potential to eliminate the need for additional surgical intervention to correct defects of the repair, reduce pump bypass time and to allow fine tuning of aortic valve leaflet coaptation, thus potentially improving operative results.

[0026] Various embodiments of the disclosure could also include permutations of the various elements recited in the claims as if each dependent claim was a multiple dependent claim incorporating the limitations of each of the preceding dependent claims as well as the independent claims. Such permutations are expressly within the scope of this disclosure.

[0027] While the invention has been particularly shown and described with reference to a number of embodiments, it would be understood by those skilled in the art that changes in the form and details may be made to the various embodiments disclosed herein without departing from the spirit and scope of the invention and that the various embodiments disclosed herein are not intended to act as limitations on the scope of the claims. All references cited herein are incorporated in their entirety by reference.

Claims

CLAIMS What is claimed is:

1. A synthetic aortic root graft comprising:

a braided tubular root graft; and

a substantially circular band defining an adjustable circular diameter operatively associated with the braided tubular root graft.

2. The synthetic aortic root graft of claim 1 , further comprising a woven tubular aortic graft joined to the braided tubular aortic root graft.

3. The synthetic aortic root graft of claim 1, wherein the braided tubular aortic root graft comprises one or more layers of low porosity material.

4. The synthetic aortic root graft of claim 1 , further comprising the braided tubular root graft defining an inlet portion shaped to approximate the shape of typical normal sinuses of Valsalva.

5. The synthetic aortic root graft of claim 4, wherein the braided tubular aortic root graft comprises a material, which may be formed and then heat set, and wherein the inlet portion of the aortic root graft is heat set into a shape which approximates the shape of typical normal sinuses of Valsalva.

6. The synthetic aortic root graft of claim 1, wherein the circular band comprises:

a linearly compressible tube; and

at least one suture operatively associated with the linearly compressible tube to provide for the reduction of the diameter of the circle defined by the band.

7. The synthetic aortic root graft of claim 1 wherein the braided tubular root graft is impregnated with a hemostatic agent.

8. The synthetic aortic root graft of claim 1 wherein the braided tubular root graft is soaked with a patient's blood prior to administration of an anti-coagulant to the blood.

9. A method of sparing an aortic valve comprising:

providing a braided tubular aortic root graft;

joining the braided tubular aortic root graft to aortic remnants of aortic valve leaflets; operatively associating an adjustable band having an adjustable diameter with the outside of the braided tubular aortic root graft at the level of the sino-tubular junction; and

adjusting the diameter of the adjustable band, thereby adjusting the diameter of the braided tubular aortic root graft at the level of the sino-tubular junction to produce a desired level of aortic valve leaflet coaptation.

10. The method of claim 7, further comprising:

providing a woven tubular aortic graft;

joining the woven tubular aortic graft to the aorta; and

joining the woven tubular aortic graft to the braided tubular aortic root graft.

11. The method of claim 9, wherein at least one of joining the braided tubular aortic root graft to aortic remnants, joining the woven tubular aortic graft to the aorta, and joining the woven tubular aortic graft to the braided tubular aortic root graft includes utilizing a process of anastomosis.

12. The method of claim 9, further comprising excising diseased tissue of the sinuses of Valsalva and the aorta.

13. The method of claim 9 further comprising prior to joining the braided tubular aortic root graft to the aortic remnants, rendering the braided tubular aortic root impermeable to blood.

14. The method of claim 13 wherein the braided tubular aortic root is rendered impermeable to blood by impregnating it with a hemostatic agent.

15. The method of claim 13 wherein the braided tubular aortic root is rendered impermeable to blood by impregnating it with a patient' s blood prior to administration of an anti-coagulant to the blood.

16. The method of claim 9 further comprising prior to joining the braided tubular aortic root graft to the aortic remnants, cutting the end of the braided tubular aortic root graft to match the aortic remnants.

17. The method of claim 16 wherein the cutting is performed with a cauterizing cutting tool to prevent fraying of the braided tubular aortic root graft.

18. A method of manufacturing a synthetic aortic root graft comprising:

providing a length of low porosity braided tube suitable for heat setting;

configuring the braided tube to have an inflow diameter and an outflow diameter; wherein the inflow diameter is less than the outflow diameter; and

heat setting an inflow region of the braided tube to approximate the shape of normal sinuses of Valsalva.

19. The method of claim 18 further comprising providing a substantially circular band defining an adjustable circular diameter in operative association with the braided tubular root graft, whereby an inner diameter of the braided tube can be selectively adjusted.

20. The method of claim 19 further comprising providing a woven tubular aortic graft and joining the woven tubular aortic graft to an outflow end of the braided tubular aortic root graft.