US20080171101A1

Movatterモバイル変換

Info

Publication number: US20080171101A1
Application number: US11/903,724
Authority: US
Inventors: Alan R. Rapacki; Dean F. Carson; A. Adam Sharkawy
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-09-10
Filing date: 2007-09-24
Publication date: 2008-07-17
Also published as: US20030015816A1; US6635214B2

Abstract

Methods and devices for manufacturing a conduit for placing a target vessel in fluid communication with a source of blood, such as a heart chamber containing blood. The conduit includes first and second portion adapted to be placed in fluid communication with a heart chamber and a target vessel. The conduit lies on the exterior of the myocardium between the blood source and the target vessel and delivers blood in multiple directions within the lumen of the target vessel. The conduit, which may be formed of any suitable synthetic vascular graft material, is generally T-shaped with the leg having two free ends disposed in the target vessel, preferably being secured thereto via a suture-free attachment. The conduit comprises vascular graft material and may be manufactured various ways, such as molding a conduit from any suitable biocompatible material or fabricating a conduit from one or more pieces of vascular graft material.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to methods and devices for manufacturing a conduit for placing a target vessel in fluid communication with a source of blood, and more particularly placing a coronary vessel in fluid communication with a heart chamber containing blood.

2. Description of Related Art

Despite the considerable advances that have been realized in cardiology and cardiovascular surgery, heart disease remains the leading cause of death throughout much of the world. Coronary artery disease, or arteriosclerosis, is the single leading cause of death in the United States today. As a result, those in the cardiovascular field continue to search for new and improved treatments.

Coronary artery disease is currently treated by interventional procedures such as percutaneous transluminal coronary angioplasty (PTCA), coronary stenting and atherectomy, as well as surgical procedures including coronary artery bypass grafting (CABG). The goal of these procedures is to reestablish or improve blood flow through occluded (or partially occluded) coronary arteries, and is accomplished, for example, by enlarging the blood flow lumen of the artery or forming a bypass that allows blood to circumvent the occlusion. What procedure(s) is used typically depends on the severity and location of the blockage(s). When successful, these procedures restore blood flow to myocardial tissue that had not been sufficiently perfused due to the occlusion.

An alternative, recently proposed treatment places the target vessel in fluid communication with a heart chamber containing blood, for example, the left ventricle. Blood flows from the ventricle into a conduit that is in fluid communication with the target vessel. Some of the challenges associated with these procedures include delivering and deploying the conduit in the patient's body, and in particular properly positioning the conduit with respect to the heart chamber and the target vessel.

The continued improvement and refinement of existing treatments and the search for new treatments are indicative of the significant effort that continues to be expended in order to develop better and more efficient ways of revascularizing the heart.

Accordingly, there is a need in the art for improved methods and devices that are capable of being used quickly, easily and in a repeatable manner to carry out cardiac revascularization successfully and economically. Consequently, there is a need in the art for methods and devices for manufacturing conduits that will meet one or more of these needs.

SUMMARY OF THE INVENTION

According to one embodiment of the invention, methods and devices are provided for manufacturing a conduit for use in placing a target vessel in fluid communication with a source of blood. One method includes steps of providing a biocompatible material suitable for use in delivering blood, and forming the biocompatible material into a conduit comprising first and second portions disposed transverse to each other and having lumens in fluid communication. The first conduit portion is formed with at least one inlet configured to be positioned in fluid communication with a heart chamber containing blood, and at least a part of the first conduit portion has sufficient rigidity to prevent collapse during myocardial contraction when disposed in or secured to myocardial tissue. The second conduit portion is formed with at least one outlet configured to be placed at least partially within the lumen of a target vessel in fluid communication with the vessel, and at least a part of the second conduit portion has sufficient resiliency to allow the second conduit portion to substantially conform to the contour of the target vessel.

Another method includes steps of providing a mold having a cavity configured to form a conduit including first and second portions disposed transverse to each other, wherein a conduit corresponding to the cavity is suitable for use in placing a source of blood in fluid communication with the lumen of a target vessel, placing a biocompatible moldable material in the mold cavity, subjecting the material to conditions that mold the material into a conduit having a desired configuration, and separating the mold and the conduit.

Another method includes step of providing a mold having a cavity including first and second portions disposed transverse to each other, positioning a mandrel in the mold cavity, the mandrel having first and second portions substantially corresponding to the first and second portions of the mold cavity, and forcing a moldable material into the mold cavity and around the first and second portions of the mandrel into the first and second portions of the mold cavity. The method further includes subjecting the material to conditions sufficient to set the material in a desired configuration, removing the mandrel from the mold, and separating the mandrel and the material to produce a conduit comprising first and second portions that are disposed transverse to each other and have lumens in fluid communication with each other.

Another method includes steps providing a mandrel including first and second portions disposed transverse to each other, the first and second portions of the mandrel defining at least one external surface corresponding to an interior surface of a desired conduit configuration, disposing a biocompatible moldable material on the external surface of the mandrel, subjecting the material to conditions that mold the material into a conduit having the desired configuration, and separating the conduit from the mandrel.

Still another method includes steps of forming biocompatible material into a conduit comprising first and second portions disposed transverse to each other and having lumens in fluid communication, forming the first conduit portion with at least one inlet configured to be placed in fluid communication with a heart chamber containing blood, and providing at least a part of the first conduit portion with sufficient rigidity to prevent collapse during myocardial contraction when disposed in or secured to myocardial tissue. The second conduit portion is formed with at least one outlet configured to be placed at least partially within the lumen of a target vessel in fluid communication with the vessel, and this step is carried out so as to form the first conduit portion with a full tubular configuration that extends substantially 360° in cross-section, and the second conduit portion with a partial tubular configuration that extends less than 360° in cross-section.

A mold constructed according to the invention includes a base defining a mold cavity, wherein the mold cavity has first and second portions configured to form a conduit including first and second portions, and wherein the first and second portions of the mold cavity are disposed transverse to each other to form a conduit with first and second conduit portions in fluid communication with each other and adapted to place the lumen of a target vessel in fluid communication with a heart chamber containing blood.

Another method according to the invention includes steps of providing first and second hollow members each of which has a lumen, forming an opening that extends into the lumen of the first hollow member, positioning one of the first and second ends of the second hollow member adjacent the opening in the first hollow member, and joining the one end of the second hollow member to the first hollow member with the lumens of the first and second hollow members sealed together in fluid communication.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following detailed description of preferred embodiments thereof, taken in conjunction with the accompanying drawing figures, wherein:

FIG. 1 is a front elevation view of a conduit constructed according to one embodiment of the invention for placing a source of blood in fluid communication with a target vessel;

FIG. 1A is a transverse sectional view taken along line A-A inFIG. 1;

FIG. 1B is a plan view of the conduit shown inFIG. 1;

FIG. 2 is a perspective view of a conduit constructed according to another embodiment of the invention for placing a target vessel in fluid communication with a source of blood;

FIG. 2A is a transverse sectional view taken along line A-A inFIG. 2;

FIG. 3A is a perspective anterior view of a heart with an occluded coronary artery and a conduit constructed according to the invention;

FIG. 3B is a perspective view of the heart shown inFIG. 3A after the conduit has been deployed to bypass the occluded artery;

FIG. 3C is an enlarged, fragmentary sectional view of the heart and conduit illustrated inFIG. 3B;

FIG. 4 is a perspective view of a conduit constructed according to another embodiment of the invention for placing a target vessel in fluid communication with a source of blood;

FIG. 5 is an enlarged, fragmentary sectional view of the heart illustrated inFIG. 3A showing the conduit ofFIG. 4 positioned in the coronary artery;

FIG. 6 is an exploded perspective view of a mold and a mandrel for forming a conduit according to one embodiment of the invention, the conduit being sized and configured for use in placing a target vessel of a patient's vascular system in fluid communication with a source of blood;

FIG. 6A is a longitudinal sectional view taken along line A-A inFIG. 6;

FIG. 7 is an exploded perspective view of a portion of the mandrel shown inFIG. 6;

FIG. 8 is an exploded perspective view of the mold shown inFIG. 6, including fasteners for securing the mold portions together;

FIG. 9 is a perspective assembled view of the mold showing a moldable material and the mandrel disposed therein;

FIG. 10 is a perspective view of the mold illustrated inFIG. 6 showing the moldable material being injected into the mold cavity;

FIG. 11 is a perspective view showing the mold illustrated inFIG. 10 being separated to remove the mandrel;

FIG. 12 is a perspective view of the mandrel and the molded preform disposed on the mandrel;

FIG. 13 is a perspective view of the mandrel and molded preform illustrated inFIG. 12 after a reinforcing component has been placed on the preform;

FIG. 14 is an exploded perspective view of another mold constructed according to the invention the mold being sized and configured to receive the mandrel and preform illustrated inFIG. 13;

FIG. 15 is a perspective view showing moldable material being injected into the mold illustrated inFIG. 14 to form the preform into a conduit;

FIGS. 15A and 15B are transverse sectional views taken, respectively, along lines A-A and B-B inFIG. 15;

FIG. 15C is a longitudinal sectional view taken along line C-C inFIG. 15;

FIG. 16 is a perspective view of the mandrel and conduit after they have been removed from the mold shown inFIG. 15;

FIG. 17 is a perspective view of the conduit after it has been removed from the mandrel shown inFIG. 16;

FIG. 17A is a longitudinal sectional view taken along line A-A inFIG. 17;

FIG. 18 is an exploded perspective view of components for forming a conduit according to another embodiment of the invention, the components being formed into a desired configuration;

FIG. 19 is an exploded perspective view of a mandrel assembly including two mandrels for use in forming the conduit;

FIG. 20 is an exploded perspective view illustrating the components shown inFIG. 18 mounted on the mandrels shown inFIG. 19;

FIG. 21 is a perspective view of the mandrels and components shown inFIG. 20 placed together;

FIG. 22 is a perspective view showing the mandrels illustrated inFIG. 21 being separated;

FIG. 23 is an exploded assembled view of the formed conduit after bonding the conduit components and removing the mandrels;

FIG. 24 is an exploded assembled view of an alternative mandrel assembly for use in forming a conduit according to the invention;

FIG. 25 is an exploded perspective view showing the mandrels ofFIG. 24 being placed in the conduit ofFIG. 23;

FIG. 26 is a perspective view of the mandrels fully positioned in the conduit shown inFIG. 25;

FIGS. 27 and 28 are perspective views of conduits constructed according to alternative embodiments of the invention;

FIGS. 29 and 30 are perspective views showing several conduit manufacturing steps according to another embodiment of the invention;

FIG. 30A is a longitudinal sectional view taken through an end of the conduit shown inFIG. 30;

FIG. 31 schematically illustrates the formation of a conduit according to another embodiment of the invention;

FIG. 32 is an end elevation view of the conduit shown inFIG. 31;

FIGS. 33A-33D are, respectively, front elevation, plan, and side and rear elevation views of a mandrel used to form a conduit according to another embodiment of the invention; and

FIGS. 34A-34E are elevation views schematically illustrating the mandrel shown inFIGS. 33A-33D being used to form a conduit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides methods and devices for manufacturing a conduit that is placed in a patient's body to establish a flow path between a source of blood and a target vessel of the patient's vascular system. In a preferred application, the source of blood is a heart chamber containing oxygenated blood and the target vessel is a coronary artery or vein. It will be recognized, however, that the conduit may be used to form a blood flow path between other hollow body structures. Also, as used herein, source of blood refers to any blood-containing structure, while oxygenated blood refers to blood containing some level of oxygen. The conduit may be used to bypass a partial or complete occlusion in the target vessel; alternatively or additionally, the conduit may be used to supplement blood flow (native or other) that is already present in the target vessel.

The Figures show several conduit configurations in order to describe various aspects of exemplary embodiments of the present invention. It will be recognized, though, that these conduits represent only a few of the numerous constructions that may be manufactured according to the principles of the invention. For example, the conduit may be manufactured so as to have any of the constructions described in co-pending, commonly owned application Ser. No. ______, filed Sep. 10, 1999, (Attorney Docket No. 010) and entitled “Conduits For Use in Placing a Target Vessel in Fluid Communication With a Source of Blood,” the entire subject matter of which is incorporated herein by reference.

In its most preferred form, the conduit of the invention include a first conduit portion having at least one inlet adapted to be placed in communication with a source of blood and a second portion having at least one outlet adapted to be placed in communication with the lumen of a target vessel. The first and second conduit portions may be defined by a single unitary member or several members that are attached or formed into a desired configuration. The first and second conduit portions are transverse to each other and have lumens that meet at a junction. For example, the first and second conduit portions have respective axes that extend transversely to each other to form a predetermined angle, the angle preferably being within a desired range that achieves acceptable flow characteristics.

FIGS. 1 and 2 will be discussed in some detail for sake of explanation and clarity. Referring toFIGS. 1,1A and1B, aconduit10 includes afirst conduit portion12 and asecond conduit portion14. Thefirst conduit portion12 has aninlet16 that is placed in fluid communication with a source of blood, and thesecond conduit portion14 has a pair ofoutlets18 that are placed in fluid communication with a target vessel. It will be appreciated that thefirst conduit portion12 may have more than one inlet and thesecond conduit portion14 may have one, two or more outlets. The first and

second conduit portions

12,14 have lumens in fluid communication with each other.

Theconduit10 is generally T-shaped with the first and

second conduit portions

12,14 meeting at ajunction20 such that their respective axes a, b are substantially perpendicular. It should be noted, though, that according to the invention the axes a, b of the first and

second conduit portions

12,14 could be disposed non-perpendicularly. For example, rather than forming a 90° (or substantially 90°) angle, the axes a, b could extend transversely to each other to form an acute or obtuse angle (depending on which side the angle is measured with respect to axis a inFIG. 1).

Thefirst conduit portion12 has afree end22 defining theinlet16 while thesecond conduit portion14 has a pair of free ends24 defining theoutlets18. The free ends22,24 may be integral extensions of their respective conduit portions or they may comprise separate members secured to the conduit. One or more of the free ends22,24 may be beveled (or otherwise configured) for easier introduction into the target vessel. The ends22,24 of the

conduit portions

12,14 are preferably formed of a flexible, relatively atraumatic material that will not damage the endothelial cells lining the intimal surface of the target vessel, particularly during placement of the device.

Theconduit inlet16 oroutlets18 may be located at positions other than those shown in the Figures, e.g., at one or more points along the length of the conduit. Similarly, in the illustrated embodiment the first conduit portion12 (axis a) is offset in that it does not bisect the second conduit portion14 (axis b); this provides the second conduit portion with different size legs extending away from the first conduit portion. Configuring the target vessel portion of theconduit10 with shorter and longer legs may be useful in introducing the conduit into the target vessel. It should nonetheless be recognized that thefirst conduit portion12 may be centrally located along the axis b of thesecond conduit portion14 to provide legs of equal length, or it may be offset from the axis b a greater distance than shown inFIG. 1.

According to one preferred embodiment, the methods and devices of the invention are used to form a conduit that is provided with a reinforcing component having sufficient strength to ensure that the conduit remains open during use by preventing or reducing the likelihood of the conduit kinking or collapsing. The reinforcing component may be integrally formed with the conduit or it may comprise a separate member secured thereto. One embodiment of a reinforcingcomponent26 is shown inFIG. 1 (in phantom) and comprises a plurality ofcoils28 which extend over the first and

second conduit portions

12,14. As seen fromFIG. 1A, the reinforcingcomponent26 is preferably encased in the body of theconduit10 which prevents contact between tissue and the reinforcingcoils28.

In the illustrated embodiment, the spacing, as well as the size and material of construction, of thecoils28 may be used to determine the amount of structural support provided by the reinforcingcomponent26. As such, these variables may be selected to produce a conduit having desired characteristics. For example, one of the first and

second conduit portions

12,14 may be made more rigid or flexible than the other by varying the pitch of the coils, the thickness of the wire forming the coils, the material forming the coils, etc., on the portions. Further, the reinforcingcomponent26 may comprise a single coil, a first coil for the first conduit portion and a second coil for the second conduit portion, a first coil for the first conduit portion and two separate coils for the two free legs of the second conduit portion, etc. Finally, it will be noted that the reinforcing component may have a non-coiled configuration, e.g., a stent or stent-like construction, and may comprise a single member or a plurality of discrete members.

Thesecond conduit portion14 is relatively flexible to allow it to yield slightly and follow the contour of the target vessel (not shown) while being placed therein. Thefirst conduit portion12 may be more rigid than thesecond conduit portion14, particularly if the blood source is a heart chamber and thefirst conduit portion12 is placed in (or secured to) myocardial tissue. In this case, thefirst conduit portion12 would preferably be relatively rigid to remain open during myocardial contraction. Thejunction20 of the first and

second conduit portions

12,14 is essentially unreinforced in the embodiment shown inFIGS. 1 and 1A, but it could be stiffened, e.g., by disposing one ormore coils28 of the reinforcingcomponent26 at or adjacent thejunction20.

Whereas the conduit10 (without the reinforcing component26) is formed of one piece of material, theconduit30 shown inFIG. 2 is formed of discrete pieces of material. Theconduit30 includes afirst conduit portion32 and asecond conduit portion34 which correspond to the first and second conduit portions of the previous embodiments. Thefirst conduit portion32 has at least oneinlet36 while thesecond conduit portion64 has at least oneoutlet38. The

conduit portions

32,34 are joined at ajunction40 by suitable means, e.g., adhesives, thermal bonding, mechanical attachment, etc., which are described further below. Thefirst conduit portion32 has afree end42 defining aninlet36 and thesecond conduit portion34 has free ends44 defining twooutlets38.

As described further below, thefirst conduit portion32 of this embodiment has anopposite end46 which is bifurcated into twoflaps48 each of which is secured to theconduit portion34 by any suitable means. The edges of theflaps48 may be tapered or feathered (as shown) to make a smooth transition with the exterior of thesecond conduit portion34, thereby minimizing the amount of material to be introduced into the lumen of the target vessel. It also may be preferable to minimize the wall thickness of the material used to form the conduit to further reduce the amount of material that must be accommodated in the target vessel lumen, without sacrificing preferential blood flow characteristics or the structural integrity of the conduit.

The illustratedconduit30 may include a reinforcing component such as26 that is coupled to or formed with the body of the conduit. Alternatively, as shown in phantom inFIG. 2A, theconduit30 could include a reinforcing layer R. The layer R could be a mechanical component secured to the conduit or a chemical substance that is partially or completely applied to the exterior (or interior) of the conduit wall.

An exemplary manner in which the conduits of the invention may be used to establish a blood flow path between a target vessel and a source of blood will be explained briefly with respect toFIGS. 3A-3C.FIG. 3A is an anterior view of a heart H showing the left ventricle LV, right ventricle RV, right atrium RA, aorta A, pulmonary trunk PT and pulmonary veins PV. The left coronary artery, including its left anterior descending branch LAD, is visible in this view, as is the right coronary artery RCA. Also shown is a diagonal branch D of the LAD. The coronary arteries run along the myocardium and deliver oxygenated blood to the myocardial tissue. An occlusion or stenosis O partially (or completely) obstructs the lumen of the LAD, which results in inadequate or no blood flow to the myocardial tissue fed by the portion of the LAD that is downstream of the occlusion O.

FIG. 3A also shows aconduit50 which is constructed according to the invention and is positioned adjacent the heart H. Theconduit50 includes first and

second conduit portions

52,54 adapted to be placed in communication with a heart chamber and a target vessel, respectively. Theconduit50 includes adevice56 for establishing communication with a heart chamber while securing the conduit in the desired position, as well as a reinforcing component for supporting the walls of the conduit. Thedevice56 is described in the aforementioned co-pending application the subject matter of which has been incorporated herein by reference.

FIG. 3B depicts the heart H shown inFIG. 3A after theconduit50 has been deployed. Thedevice56 is inserted into the tissue of the myocardium so that its distal end is in fluid communication with the left ventricle LV. Thefirst conduit portion52 extends from thedevice56 to the LAD, and thesecond conduit portion54 enters the LAD at a location distal to the occlusion O, theportion54 contacting and sealing against the luminal surface of the vessel wall. As a result, blood flows from the left ventricle LV into theconduit50 and the LAD to perfuse myocardial tissue distal to the occlusion O.

FIG. 3C is an enlarged view of a portion of the heart H shown inFIG. 3B. Thedevice56 is shown positioned in the myocardium M so as to communicate with the left ventricle LV. Thedevice56 is preferably sized so as to extend completely through the myocardium M and project into the left ventricle LV, slightly beyond the exterior of the myocardium. Alternatively, thedevice56 could terminate within the myocardium with a distal segment of thefirst conduit portion52 extending into the left ventricle, or thedevice56 omitted and thefirst conduit portion52 positioned in the myocardium. In any case, as explained in the aforementioned co-pending application, it may be desirable to first measure the thickness of the myocardium, either approximately or precisely, at the area that will receive the device56 (or the distal segment of the first conduit portion52). Thedevice56 may then be placed with its ends properly positioned with respect to the left ventricle and the exterior of the myocardium.

Thesecond conduit portion54 includes twooutlets58 placed in the lumen of the LAD through an incision I; in the illustrated embodiment, theconduit portion54 is secured in place by suture S. Thesecond conduit portion54 will typically be placed in the target vessel distal to the occlusion by a distance that permits easier introduction into the lumen, as opposed to entering a diseased or stenosed section of the vessel. This results in a space located between the occlusion O and theconduit outlet58 that is disposed nearest the occlusion (the outlet to the left inFIG. 4C). Thus, if the conduit does not provide blood flow toward the occlusion O, this space, and more particularly the myocardial tissue fed by this section of the LAD, may become ischemic, particularly if the occlusion totally blocks any native flow through the vessel from an upstream source.

Accordingly, as explained in the aforementioned co-pending application, the conduits of the invention are preferably configured to deliver blood into the target vessel in multiple directions to fully revascularize the myocardial tissue perfused by the vessel. As shown inFIG. 3C, blood flows into thesecond conduit portion54 and exits theoutlets58 in more than one direction, as indicated by the arrows. The illustrated directions are along a common axis and opposite each other, but it will be recognized that this is only one possible arrangement to achieve multidirectional flow in the target vessel.

FIG. 4 shows aconduit60 constructed according to another embodiment of the invention. Theconduit60 includes afirst conduit portion62 and asecond conduit portion64, thedevice56 being coupled to theportion64. Thefirst conduit portion62 has aninlet66 and includesmultiple bends68a,68bwhich serve to align thesecond conduit portion64 with the axis of the target vessel. Theconduit60 is generally L-shaped andsecond conduit portion64 has an outlet that directs blood into the target vessel. Thebends68a,68bmay be imparted to theconduit60 in various manners. For example, a mandrel having a shape and size complementary to that of theconduit60 may be dipped in a suitable biocompatible material, e.g., silicone, and then heated or subjected to other conditions to cause the material to set and form the desired conduit configuration. Two or more bends are imparted to the conduit and preferably lie in two different transverse planes, for example, substantially perpendicular planes as shown inFIG. 4. It should be recognized that the particular angle(s) selected, as well as the overall configuration of the conduit, may be varied from that depicted depending on the application and user preference.

FIG. 5 shows theconduit60 positioned in the target vessel (the LAD in the illustrated embodiment) and the heart chamber (the left ventricle) in the same manner as theconduit50 shown inFIGS. 3A-3C. As shown, themultiple bends68a,68bof thesecond conduit portion64 direct its outlets generally along the axis of the target vessel, although alternative configurations could be used as well. One benefit of this embodiment is that when used in an external manner (i.e., a significant portion of the conduit is exterior to the myocardium) the configuration allows the conduit to be placed through the myocardium at a location that is spaced from the coronary vessel. This is contrast to placing a conduit so that it passes transmurally through the myocardium and the inner or posterior wall of the target vessel to deliver blood into the vessel lumen. This embodiment thus provides flexibility insofar as the portion of the conduit communicating with the heart chamber may be placed through the myocardium at different locations while still accessing the target vessel in the desired manner, which may be useful in situations that present limited access to the heart or target vessels.

It will be appreciated that the size of the conduit and thus the methods and for manufacturing the conduits will vary depending on the application. In short, each conduit portion has a length, a diameter (or a different dimension if the cross-section is non-circular) and a wall thickness, and the methods and devices of the invention may be utilized and modified to control one or more of these dimensions, for example, to obtain desired flow characteristics or adapt the conduit to a given application.

The conduit is preferably sized and configured to form a blood flow path that is equal or substantially equal, in volume of blood carried, to the blood flow path defined by the native vessel. In other words, the conduit preferably defines an inner diameter that equals or substantially equals the inner diameter of the native vessel. As a result, when placed in the target vessel the conduit allows a sufficient volume of blood to flow through the target vessel. If the target vessel is a coronary artery, this ensures that blood will flow to the distal vasculature and perfuse the myocardial tissue. Some preferred materials of construction as well as ranges for various dimensions of the conduits are provided in the aforementioned, co-pending application entitled “Conduits For Use in Placing a Target Vessel in Fluid Communication With a Source of Blood” (Attorney Docket No. 010).

Referring now toFIGS. 6 through 17A, one embodiment for manufacturing a conduit according to the invention will be described, the conduit being suitable for use in placing a target vessel of a patient's vascular system in fluid communication with a source of blood. This embodiment uses a molding process to form a conduit having a desired configuration. In particular, the illustrated process can be characterized as an injection molding process in that a moldable material is injected into a mold cavity having a predetermined configuration. It will be appreciated that injection molding (either the same as or varied from that shown in the Figures) is only one possible type of molding procedure that may be used according to this embodiment of the invention.

FIGS. 6 and 6A show amold80 including twomold halves82 which define opposingfaces84 and are adapted to receive amandrel86. The mold halves82 includerespective mold cavities88 which are sized and configured to form a conduit having a predetermined size and shape. In the illustrated embodiment thecavities88 are mirror images of each other and form a closed cavity when mated. Eachcavity88 includes first and second portions corresponding to first and second portions of the conduit. In particular, themold cavity88 of eachmold half82 has afirst portion90 that communicates with and is disposed transverse to asecond portion92, as does thecavity88 of the other mold half82 (not shown in the Figures). While the illustrated embodiment includes twomold halves82, it will be recognized that the mold may comprise a different number of components.

The first and

second portions

90,92 of eachmold cavity88 are preferably provided with one ormore channels94 to vent air and allow excess molding material to flow out of themold80. Eachmold cavity88 also has aninlet96 into which moldable material is injected, theinlet96 being tapered or necked down at anarea98 communicating with thesecond portion92 of thecavity88. SeeFIG. 6A. As described below in connection with the Examples, themold80 may be formed of any suitable material, for example, a metal such as steel or aluminum, or a nonmetallic material. The mold cavities88 may be milled or otherwise formed in the mold according to desired specifications.

Themandrel86 has first and

second portions

100,102 which are received in the first and

second portions

90,92 of eachmold cavity88. More specifically, in addition to themold cavity88, eachmold half82 includes agroove104 for receiving part of thefirst mandrel portion100, and a pair ofgrooves106 for receiving part of thesecond mandrel portion102. The

grooves

104,106 extend from the

mold cavity portions

90,92 and are sized to receive part of the

respective mandrel portions

100,102 in surface-to-surface contact when themold80 is assembled. The

portions

90,92, in contrast, are larger than the

mandrel portions

100,102 and

grooves

104,106, as described below regarding FIGS.15 and15A-15C. As a result, when themandrel86 is placed in themold80, an annular space is defined between the

mandrel portions

100,102 and the

cavity portions

90,92 to receive the moldable material.FIG. 7 shows a preferred mandrel configuration wherein the

portions

100,102 are designed to fit snugly together with a minimal profile at theirjunction108. The

mandrel portions

100,102 are separated for easy removal from the finished conduit.

FIG. 8 shows the mold halves82 (without the mandrel) along with an exemplary means for aligning and securing the halves together. Onemold half82 is provided withdowel pins110 which are received in correspondingbores112 formed in the other mold half. The twomold halves82 are also provided with mating bores114 that receive threadedfasteners116. Thefasteners116 are used to force the mold halves82 together with theirfaces84 tightly sealed to prevent leakage from the mold (beyond that provided by the channels94). It will be appreciated that alternative or additional means for aligning the mold halves82 could be used, e.g., a frame that engages the exterior of themold80. Similarly, the mold halves82 may be forced together by alternative or additional means, e.g., a clamp or vise that engages the exterior of themold80.

FIG. 9 shows the mold halves82 andmandrel86 assembled with the ends of the first and

second mandrel portions

100,102 held in the

grooves

104,106. In the illustrated embodiment the ends of the

mandrel portions

100,102 extend beyond the mold halves82, but they could instead terminate at or within the mold halves. A release agent is preferably placed on the exterior surface of the mandrel to aid in removing the conduit. A suitable moldable material M is injected into the mold, as can be seen in theinlet96 inFIG. 9. A plunger P (or other suitable means) is used to inject the material M into the mold to completely fill thecavity88 around themandrel86.FIG. 10 shows the plunger P inserted and a resulting flash F of material M flowing out of thechannels94.

Themold80 is then subjected to suitable conditions, for example, maintained at a predetermined temperature for a sufficient amount of time, in order to set the material M in the desired configuration. Upon completion of this step, the mold halves82 are separated, as shown inFIG. 11. The flash F is trimmed and themandrel86 is removed from the mold halves82 along with a moldedpreform118 now carried by the mandrel, as shown inFIG. 12. Thepreform118 has first and

second portions

120,122, respectively supported by the first and

second portions

100,102 of themandrel86. At this point, if desired, thepreform118 may be removed by disassembling themandrel86 and subjected to final processing to form a conduit, for example, removing any excess material M, applying any desired coating(s), such as antithrombogenic or antibacterial materials, and packaging and sterilizing, such as by placing the device in a Tyvek® pouch that is sterilized by ethylene oxide or gamma radiation. The finished conduit is sterile and ready to be used as a blood delivery device during a cardiovascular procedure.

According to a preferred embodiment of the invention, though, thepreform118, prior to final processing, is provided with a reinforcing component to add a desired amount of rigidity to prevent or reduce the likelihood of the conduit collapsing or kinking during use.FIG. 13 shows one possible reinforcingcomponent124 which is in the form of a wire coil wrapped around all (or alternatively a part of) thepreform118. The wire may be secured to thepreform118 by adhesive or other means in order to remain in place during further processing of the conduit. It will be understood that a component other than wire may be used to reinforce the conduit, for example, as discussed above with respect to the embodiments ofFIGS. 1 and 2.

FIG. 14 shows anothermold130 having a construction essentially the same as themold80. Themold130 hasmold halves132 withmating surfaces134 andmold cavities136. Themold cavities136 are larger than the mold cavities88 (of the mold80) in order to accommodate thepreform118 and the reinforcingcomponent124, both of which are now carried by themandrel86, while still providing an annular space around the reinforcing component into which the material M can flow. The mold halves132 have grooves138 (not visible inFIG. 14) corresponding to thegrooves104 ofmold80 for receiving the

portions

100,102 of the mandrel.

FIG. 15 shows the mold halves132 assembled with themandrel86 and the reinforcedpreform118 disposed therein. The plunger P is shown injecting the material M into themold130 with material flash F flowing out of the mold.FIG. 15A is a sectional view through themold130 showing moldable material M filling the annular space between themandrel portion100 and afirst cavity portion140.FIG. 15B is a sectional view through themold130 showing part of thefirst mandrel portion100 in surface-to-surface contact with thegroove138.FIG. 15C is a sectional view through the mold showing thegroove138 holding part of thefirst mandrel portion100, thegroove144 holding part of thesecond mandrel portion102, and the first and

second cavity portions

140,142 filled with material M.

The material M is injected and flows around thepreform118 and the reinforcing component124 (omitted fromFIG. 15A for clarity) to fill themold cavity136. Themold130 is then subjected to suitable conditions to set the material M, as explained above with respect to the steps illustrated inFIGS. 11-12. Next, as shown inFIG. 16, the reinforcedconduit146 and themandrel86 are removed from themold130. As seen fromFIG. 15, the secondmold cavity portion142 may have tapered ends so that thesecond conduit portion150 has tapered or beveled ends (as does thesecond portion14 of theconduit10 shown inFIG. 1).

Referring toFIG. 16, the

mandrel portions

100,102 are then separated and removed from theconduit146. As shown inFIG. 17, theconduit146 includes first and

second conduit portions

148,150 that essentially correspond to the

conduit portions

12,14 of the embodiment shown inFIG. 1. The construction of the illustratedconduit146 can be seen inFIG. 17A and includes thepreform118, the reinforcingcomponent124, and alayer152 of material M (applied inFIG. 15). Also shown is alayer154 of adhesive, for example, silicone, which is preferably, though not necessarily, applied to thepreform118 to retain the reinforcingcomponent124 in position, as explained above.

Turning now toFIGS. 18-26, another embodiment for manufacturing a conduit suitable for use in placing a target vessel in fluid communication with a source of blood will be described. This embodiment forms the conduit from one or more pieces of biocompatible material suitable for use in blood contacting applications. The illustrated embodiment forms a conduit from two pieces of material; it will, however, be appreciated that the conduit may comprise fewer or more material pieces. Additionally, it should be appreciated that the specific means by which the material pieces are joined in the illustrated embodiment is exemplary and the invention encompasses alternative means as will be recognized by persons skilled in the art.

FIG. 18 shows first and second

hollow members

160,162 which are sized and configured for use in placing a coronary blood vessel in fluid communication with a heart chamber containing blood. Thefirst member160 has anend164 defining aninlet166 and thesecond member162 has twoends168 definingoutlets170. The other ends of the

members

160,162 are attached during formation and result in the conduit construction shown inFIG. 2.FIG. 19 shows two

mandrels

172,174 suitable for use in supporting the

members

160,162 during processing. Themandrel172 has afree end176 and anotherend178 with atongue180. Themandrel174 has twofree ends182 and anotch184 configured to receive thetongue180. Themandrel172 is adapted to be placed in the firsthollow member160 and themandrel174 is adapted to be placed in the secondhollow member162, preferably via a tight sliding fit.

FIG. 20 shows the

mandrels

172,174 inserted into the first and second

hollow members

160,162. Thetongue180 of themandrel172 extends to the end of thehollow member160 betweenbifurcated flaps186, while thenotch184 of themandrel174 is aligned with a window188 formed in the secondhollow member162.FIG. 21 shows the

mandrels

172,174 assembled with the first and second

hollow members

160,162 engaged adjacent thetongue180 and thenotch184 of the mandrels. Theflaps186 extend partially around the exterior of the secondhollow member162; they could alternatively extend fully around themember162.

In the illustrated embodiment, prior to placing theflaps186 of thehollow member160 against themember162, a suitable adhesive (indicated schematically at190 inFIG. 20) is applied to one or both of the hollow members. The

mandrels

172,174 are then moved to the position shown inFIG. 21. The adhesive (or alternative securing means) is subjected to conditions that allow it to bond the first and second hollow members. Next, the

mandrels

172,174 are disassembled, as illustrated inFIG. 22. This results in theconduit192 shown inFIG. 23, which includes first andsecond conduit portions194,196 (defined by thehollow members160,162) secured at ajunction198.

Theconduit192 is ready to be subjected to final processing, for example, trimming or removing any excess material from the conduit and applying any desired coating(s) to the conduit portions, such as anti-thrombogenic or anti-bacterial coatings. The conduit is then ready for packaging and sterilization, for instance, by placing the conduit in a Tyvek pouch the is subjected to ethylene oxide or gamma radiation sterilization. The finished conduit is sterile and ready to be used as a blood delivery device during a cardiovascular procedure.

FIG. 24 shows amandrel assembly200 including first and

second portions

202,204 having a desired size and shape for supporting and imparting a particular configuration to the conduit. Themandrel assembly200 is shown inFIG. 25 along with theconduit192. Themandrel portion204 comprises two elements removably secured to each other by a threadedpost206 and bore208, the post passing through abore210 in themandrel portion202 to secure theassembly200.FIG. 26 shows themandrel assembly200 supporting theconduit192. The illustratedmandrel assembly200 has a round exterior, although other shapes could of course be used, to support similarly or differently configured conduits.

FIG. 27 shows a further optional step in manufacturing theconduit192, which is shown supported by the

mandrel portions

202,204. Thejunction198 between the first and

second conduit portions

194,196 is provided with a reinforcingcomponent212. Thecomponent212 is a reinforcing strap wrapped partially or completely around theconduit junction198.FIG. 28 shows yet another optional step in which an alternative reinforcingcomponent214 is used to strengthen theconduit junction198. Thecomponent214 includesbifurcated flaps216 sized and configured to closely engage the exterior surface of theconduit junction198. Theflaps216 preferably extend away from theflaps186 of thefirst conduit portion194. This strengthens thejunction198 and enhances hemostasis in use by sealing against the target vessel wall.

FIGS. 29,30 and30A illustrate an alternative method of reinforcing all or a portion of a conduit. Theconduit192 is used again for illustration and is supported by themandrel assembly200, as shown inFIG. 29. Reinforcingcomponents218 in the form of sleeves are slid over the ends of thesecond conduit portion196. Adhesive or other means for joining the components may be used. According to the illustrated embodiment, the reinforcingcomponents114 are arranged so as not to come into direct contact with the luminal surface of the target vessel wall. As shown inFIG. 30, the reinforcingcomponents218 are disposed on the exterior of thesecond conduit portion196, and the ends of the second conduit portion are everted at220 to capture the reinforcingcomponents218. This ensures that the material of the second conduit portion (which has beneficial blood interface characteristics) contacts the blood flowing through the target vessel, rather than the reinforcing components218 (FIG. 30A). It will be understood that while the illustrated reinforcing components are annular and extend around the circumference of the ends of the second conduit portion, they could instead extend around a portion of the ends of the conduit portion.

FIGS. 31 and 32 illustrate an exemplary method of manufacturing a conduit wherein the second portion (received in the target vessel) contacts less than the entire circumferential surface of the vessel wall. Theconduit10 shown inFIG. 1, with first and

second conduit portions

12,14, will be used for sake of example. In the process schematically illustrated inFIG. 31, a conduit is initially formed with a second portion defining a closed (or substantially closed) circumference, and is subjected to a material removal process. This process results in the second conduit portion defining less than a closed circumference, and thus contacting less than the entire luminal surface of the vessel wall when implanted. Further, the preferred conduit design leaves unblocked the posterior portion of the vessel wall and any septal perforators emanating from the section of the vessel being treated.

Avoiding or minimizing contact with the posterior wall is beneficial as it reduces the risk of dislodging stenotic material or otherwise damaging the vessel. However, as shown inFIG. 32, thesecond conduit portion14 may nonetheless be provided with a device that engages some of the luminal surface of the vessel wall. For example, thesecond conduit portion14 may include the reinforcingcomponent26 which extends beyond the edges E, as can be seen best fromFIG. 31. While the reinforcingcomponent26 is shown extending 360°, it may extend less than 360°.

The material may be removed by any suitable process, which will depend at least in part on the conduit material. For example, if the conduit, and in particular the second portion of the conduit, is formed of a relatively high durometer material, the process may comprise micro-abrasive media ablation techniques. It will be recognized that the procedure used to remove a desired amount of the material will depend at least in part on the specific material being used.

FIGS. 33A-33D and34A-34E show another embodiment for manufacturing a conduit suitable for use in placing a target vessel in fluid communication with a source of blood will be described. This embodiment forms the conduit by a dip molding process that uses a mandrel having a configuration matching the desired conduit configuration. As shown, amandrel230 is formed with first and

second portions

232,234 corresponding, respectively, to the first and second portions of the conduit to be formed. The first mandrel portion is curved as shown inFIG. 33A and includes abend236 which directs the remaining portion laterally away from anend238 of the mandrel portion232 (theend238 corresponding to the end of the conduit placed in the heart chamber). Thefirst mandrel portion232 includes asecond bend240 extending from thefirst bend238 to thesecond mandrel portion234. Thesecond bend240 forms a curved transition from thefirst bend238 to thesecond mandrel portion234 so as to align theportion234 substantially along the longitudinal axis of the target vessel. The mandrel may be formed of any suitable material, for example, steel.

FIGS. 34A-34E schematically illustrate using themandrel230 shown inFIGS. 33A-33D in a dip molding process to form a conduit for use in placing a target vessel in communication with a heart chamber containing blood. The mandrel230 (FIG.34A) is preferably treated with a mold release and then dipped into a container of moldable material, for example, NuSil MED-6210, commercially available from NuSil Technology of Carpinteria, Calif. The silicone is cured and produces a preform240 (FIG. 34B). The mandrel is preferably manipulated by being rotated in multiple directions to promote even flow of silicone and avoid bubbles or uneven dispersion on the mandrel. The mandrel and preform240 are dipped again and the silicone cured to produce a preform242 (FIG. 34C). A reinforcing component in the form of acoil spring246 is wrapped on the preform (FIG. 34D). The assembly is dipped again in silicone and then cured to produce a conduit248 (FIG. 34E).

It will be recognized that the illustrated injection and dip-molding procedures are exemplary only in that other molding procedures may be used to form the conduit. As an example, a suitable rotational molding process may be used to manufacture conduits according to the invention. Other molding processes may of course be used as well.

The methods and devices of the invention have been used to produce various types of conduits that have been implanted in animals and have successfully delivered blood from a source to a target vessel. In the animal studies the source of blood was the left ventricle and the target vessel was a coronary artery. Three examples are presented below.

Example 1

A first mold including two mold halves was machined from aluminum and had a configuration substantially the same as that shown inFIG. 6. The mold halves were connected via dowel pins and grooves were milled into the faces of the mold halves. The grooves defined a cavity with first and second portions disposed transverse to each other to form a conduit having the same configuration. The first and second cavity portions were sized to receive a steel mandrel, and the cavities and the mandrel substantially corresponded to those shown inFIG. 6

A light coating of spray-on mold release was applied to the mandrel, and the mandrel was placed in the mold halves which were then assembled. Silicone was used as the moldable material. Air was removed from the silicone by vacuum and ultrasonic agitation prior to injecting the silicone into the mold cavity. Next, approximately one cc of NuSil Med-4950 silicone was poured into the inlet of the mold to form the conduit preform (as this conduit included a reinforcing component), and a plunger was used to force the material further into the mold inlet. Air was removed from the mold by applying a vacuum, and then the plunger was used to further force the silicone into the mold cavity.

The silicone was cured by heating the mold to 150° C. for 1 hour. The mold cooled and the halves separated after trimming the excess material from the gates. The mandrel and molded conduit were removed and washed with water and alcohol and then allowed to dry. Next, a reinforcing component was added. Nitinol coils were prepared with both left and right-hand pitch directions for the different conduit portions from a length of nitinol wire. A first right-hand coil was wrapped around the first conduit portion and a second right-hand coil was wrapped around one leg of the second conduit portion, at the same pitch. A similarly sized left-hand coil was wrapped around the other leg of the second conduit portion at the same pitch (with the outermost ends of the coils boxed with a smaller pitch). The two coils were wrapped around the second conduit portion with one turn extending across the junction.

Before wrapping the coils, NuSil Med-6210 silicone was applied to the preform to help secure the coils to the conduit, as shown by the embodiment ofFIG. 17A. The coils were then wrapped and the mandrel placed in a second mold configured the same as the first mold but larger to accommodate the conduit preform and reinforcing component now carried by the mandrel. NuSil Med-4950 silicone was injected into the second mold and the mold was heated to set the silicone and bond the respective components, in accordance with the steps already used to produce the conduit preform. The mandrel was then removed and disassembled to allow the conduit and mandrel to be separated.

A device for establishing flow communication with a heart chamber, such as thedevice66 described above with respect toFIGS. 4A-4C, was secured to the distal end portion of the first portion of the conduit. The conduit was sterilized and ready for use by being implanted in an animal heart to deliver blood from a heart chamber, such as the left ventricle, to a target vessel, such as the left anterior descending coronary artery.

Example 2

Two tubular lengths of expanded PTFE (ePTFE) having a wall thickness of 0.008 inch and an internodal distance of 30 microns were formed substantially as the two conduit portions shown inFIG. 18. Mandrels were coated with a release agent and were used to support the two pieces of ePTFE while they were joined. Silicone was placed between the two portions at the junction and the silicone was cured in an oven at 150° for 2 hours to bond the two portions; the silicone, NuSil Med-6640 wicked between the nodes of the ePTFE and when cured bonded the pieces together to produce a conduit preform having two portions with lumens in fluid communication.

A reinforcing component was applied by wrapping a nitinol wire around the first and second conduit portions. The exterior surface of the conduit preform was coated with NuSil Med-4850 (LSR) silicone and the reinforcing wire was wrapped around the preform, embedding itself in the silicone. The silicone was then cured again in an oven at 150° for 1 hour. The resulting conduit included a layer of silicone over the coils of the reinforcing component to prevent their direct contact with animal tissue. The mandrels were disassembled and a device for communicating with a heart chamber was coupled to the first conduit portion. The device was then ready to be sterilized and placed in a target vessel of an animal heart.

It should be understood that reinforcing components, layers, etc., are preferred but not necessary, such components preferably taking the form of those disclosed in the aforementioned co-pending application (Attorney Docket No. 010). Also, if intended for use in an application with a heart chamber as the blood source, the conduit may be provided with a device for facilitating communication with the heart chamber, and preferably preventing or minimizing blockage of the conduit. Suitable devices are disclosed in disclosed in co-pending, commonly owned application Ser. No. 09/304,140, filed on May 3, 1999 and entitled “Methods and Devices for Placing a Conduit in Fluid Communication With a Target Vessel,” the entire subject matter of which is incorporated herein by reference.

The conduits manufactured according to the invention may include a valve or other means for controlling or regulating blood flow. Suitable valves, as well as means for measuring myocardial thickness or verifying entry into the heart chamber, are disclosed in application Ser. No. 09/023,492, filed on Feb. 13, 1998, and entitled “Methods and Devices Providing Transmyocardial Blood Flow to the Arterial Vascular System of the Heart,” the entire subject matter of which has been incorporated herein by reference. Likewise, the conduits may be provided with a reservoir for retaining and discharging blood in a desired manner.

The conduits of the invention may be manufactured as part of, or for coupling to, a conduit delivery device, such as that disclosed herein. The conduits and delivery devices manufactured according to the invention may be sized and configured differently from that specifically illustrated in the Figures. For instance, the cross-section of one or more portions of the conduit may be noncircular, e.g., elliptical, to better match the profile of the target vessel. As a further example, the delivery device may be relatively short with the shaft assembly substantially rigid for use in an open-chest procedure. Alternatively, the delivery device may be configured for use in either a minimally invasive or endovascular procedure, wherein the actuators for controlling the device components are located adjacent the proximal end of the device to allow remote deployment of the conduit, for example, as disclosed in the aforementioned, co-pending, commonly-owned application Ser. No. 09/304,140.

It will be appreciated that the features of the various embodiments of the invention may be used together or separately, while the manufacturing methods and devices disclosed herein may be modified or combined in whole or in part. As an example, more than one conduit may be formed as part of (or coupled to) a manifold that is placed in communication with one source of blood so as to deliver blood to multiple target vessels. The conduits and devices of the invention may include removable or detachable components, could be formed as disposable instruments, reusable instruments capable of being sterilized, or comprise a combination of disposable and reusable components.

Further, it will be understood that the invention may be used to manufacture conduits for use in specific types of medical procedures, for example, an open surgical procedure including a median sternotomy, a minimally invasive procedure utilizing one or more relatively small access openings or ports, or an endovascular procedure using peripheral access sites. Similarly, the conduits may be designed for use in beating heart procedures, stopped-heart procedures utilizing cardiopulmonary bypass (CPB), or procedures during which the heart is intermittently stopped and started.

The preferred embodiments of the invention are described above in detail for the purpose of setting forth a complete disclosure and for sake of explanation and clarity. It will be readily understood that the scope of the invention defined by the appended claims will encompass numerous changes and modifications.

Claims

1. A mold for forming a conduit for use in placing a target vessel of a patient's vascular system in fluid communication with a heart chamber containing blood, the mold comprising:

a base defining a mold cavity;

wherein the mold cavity has first and second portions configured to form a conduit including first and second portions;

wherein the first and second portions of the mold cavity are disposed transverse to each other to form a conduit with first and second conduit portions in fluid communication with each other and adapted to place the lumen of a target vessel in fluid communication with a heart chamber containing blood

2. The mold ofclaim 1, wherein the first and second portions of the mold cavity define a T-shaped conduit.

3. The mold ofclaim 1, in combination with a mandrel having first and second portions substantially corresponding to the first and second portions of the conduit and the mold cavity.