Patent Description:
Heart valve disease is a serious problem that involves the malfunction of one or more valves of the heart. The malfunction can manifest itself in a variety of manners. For example, valve stenosis is the calcification or narrowing of a native heart valve. As a result, the native heart valve is not able to completely open and blood flow through the native valve is impeded or restricted. Another example of heart valve disease is valve insufficiency. Valve insufficiency is the failure of a native heart valve to close properly to prevent leaking, or backflow, of blood through the valve.

Various methods have been developed to treat heart valve disease. Some of these methods require a balloon member that is expanded within the native heart valve. For example, a balloon member can be used in a valvuloplasty procedure where the balloon member is positioned within the native heart valve and expanded to increase the opening size (i.e., flow area) of the native heart valve and thereby improve blood flow. Another procedure that can be performed is a valve replacement, in which a native heart valve is replaced by an artificial heart valve. The implantation of an artificial heart valve in the heart can also involve the expansion of a balloon member in the valve annulus. For example, the balloon member can be used to increase the size of the native valve prior to implantation of the artificial valve and/or it can be used to expand and deploy the artificial valve itself.

Currently, a single balloon is typically used to deploy the heart valve or stent in minimally invasive cardiovascular procedures. The expansion of a balloon member within a native valve or other vascular passageway, however, can temporarily block or restrict blood flow through the passageway. Furthermore, in the case of valve replacement, the positioning of the artificial heart valve may be complicated by the buildup of pressure in the left ventricle. For example, the blocked blood flow will create a strong force against the balloon while the heart is still pumping during the procedure, decreasing the stability of the implant and making it difficult to position the heart valve. Accordingly, valvuloplasty and valve replacement procedures, and other similar procedures which utilize expandable balloon members, must generally be performed quickly so that the balloon member is inflated for only a brief period. Rapid ventricular pacing procedures may be employed to increase the stability, but this procedure can only be carried out for a limited time span.

In <CIT>, an inflatable balloon is disclosed, including a base balloon having a cylindrical section and a conical section and at least one circumferential fiber extending circumferentially around the conical section. The inflatable balloon includes a plurality of reinforcing strips in the conical section over the at least one circumferential fiber. Each reinforcing strip includes a plurality of fibers extending at an angle relative to the at least one fiber. Each reinforcing strip is positioned a set circumferential distance away from a neighboring reinforcing strip.

<CIT> discloses a sheath arrangement for spiral balloon catheters which is said to permit improved perfusion during dilation of a body vessel.

Further background for the present invention is provided by the medical devices disclosed in <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Accordingly, a need exists for improved devices that enable the patient's blood to flow through the passageway while the procedure is taking place. Such devices would increase the precision of device placement and reduce the risk of injury to the patient.

Disclosed herein are designs for improved inflatable structures for use during minimally invasive cardiovascular procedures. These inflatable structures facilitate the perfusion of blood through an anatomical structure, such as a heart valve, during the cardiovascular procedure. The inflatable structures are formed of a plurality of balloons arranged circumferentially around a central location or axis. The plurality of balloons in this arrangement thus form a lumen through which blood flows. Each balloon of the plurality is shaped or configured to stabilize the adjacent balloons, limiting their movement relative to each other. For example, some embodiments may feature balloons with a keystone shape that limits movement of the balloons inward toward the lumen. Some implementations can also include a support coil running through the lumen. The support coil holds the lumen to be open to perfusion even in the early stages of balloon inflation. Methods of using the inflatable structures are also disclosed herein.

One embodiment includes a balloon catheter for insertion into a body lumen with blood flowing therethrough. The balloon catheter includes an elongate member and a plurality of balloons. The elongate member defines an inflation lumen and has a proximal and distal ends. The plurality of balloons are coupled to the distal end of the elongate member. The balloons are also connected in fluid communication with the inflation lumen of the elongate member. Advantageously, the balloons are arranged radially about a central axis so as to form a lumen. The lumen extends along the central axis when the balloons are inflated. The lumen is configured to pass blood and thus provide perfusion for downstream tissues of the patient. Each of the balloons includes a non-circular cross-sectional shape having at least two substantially straight side portions extending radially relative to the central axis. Each substantially straight side portion at least partially abuts the substantially straight side portion of an adjacent one of the balloons. In this manner, this adjacent arrangement guards against movement of the balloons and interruption of the perfusion lumen.

The balloon catheter of the invention comprises an elongate, hollow structure having porosity. The hollow elongate structure is coupled to the distal end of the elongate member and extends along the central axis within the lumen between the balloons. The elongate hollow structure at least partially supports the balloons in both their crimped and inflated states. In one embodiment, the hollow elongate structure is a support coil, a braided tube or a selectively cut tube. The support coil can include a dumbbell shape that has bulbous regions at its ends and a tubular central region. The support coil can include a large pitch at the bulbous end regions to facilitate blood passage therethrough. In addition, the balloon catheter may include an implant, such as a prosthetic heart valve, crimped over the balloons and the tubular central region of the support coil.

In another aspect, the straight side portions of the balloons may converge toward each other (in a cross-section) as they extend toward the central axis. This forms a wedge or keystone shape that stabilizes the balloons within the radially adjacent arrangement.

In other aspects, the non-circular cross-sectional shape may further comprise an inner portion and an outer portion. The inner portion extends between a radially inward end of the at least two substantially straight side portions. And, the outer portion extends between a radially outward end of the at least two substantially straight side portions. The inner portion can be positioned adjacent to the inner lumen so as to define a portion of the inner lumen. The outer portion can be longer than the inner portion and the cross-sectional shape can be a keystone shape.

In another aspect, the ends of the balloons can have spaces defined between them. The spaces connect the lumen between the balloons and the blood in the body lumen in fluid communication. For example, the ends of the balloons can taper to tubes with small enough diameters to define the spaces between them. The small diameter tubes can be combined into a manifold that is connected in communication with the inflation lumen of the elongate member. The manifold separates and distributes fluid for inflation of the balloons through their small diameter tubes.

In yet another aspect, the balloon catheter can include a plurality of interlocking mechanisms positioned between adjacent pairs of the balloons. The interlocking mechanisms can include, for example, corresponding U-shaped protrusions and recesses formed on the straight sides of the balloons.

The balloons catheter can also include a surrogate valve configured to block spaces defined between the ends of the balloons. This prevents backflow of blood through the lumen between the balloons. The surrogate valve can include a plurality of leaflets configured to extend over the spaces during backflow of blood. The leaflets can be further configured to deflect away from the spaces during forward flow of blood.

A method of using a balloon catheter of one embodiment includes extending an elongate member through an opening in a patient until a distal end of the elongate member reaches a procedure site. Fluid is flowed through an inflation lumen into a plurality of balloons coupled to the distal end of the elongate member at the procedure site. The balloons are inflated in a circumferentially adjacent arrangement to form a perfusion lumen extending along an axis about which the balloons are arranged. Stability of the balloon arrangement is maintained by abutting radially extending straight sides of the balloons against each other. Blood is perfused from one end of the circumferentially adjacent arrangement of balloons, through the perfusion lumen and to the other end of the circumferentially adjacent arrangement of balloons. In some implementations, the procedure site is a cardiovascular structure which is accessed transapically, transfemorally, or transaortically.

The method can also include, when inflating the balloons, defining spaces between the balloons at one end and at the other end of the arrangement and perfusing blood through the spaces into the perfusion lumen.

The method can further include expanding a prosthetic heart valve by exerting a force on a frame of the heart valve by inflating the balloons.

Also, the method can further include supporting the balloons on a helically wound coil extending through the perfusion lumen. The blood can also be perfused through the helically wound coil within the lumen.

The following description of certain examples of a medical apparatus (e.g., a balloon catheter assembly) should not be used to limit the scope of the medical apparatus as defined in the claims. Other examples, features, aspects, embodiments, and advantages of the medical apparatus as defined in the claims will become apparent to those skilled in the art from the following description. As will be realized, the medical apparatus as defined in the claims is capable of additional aspects, all without departing from the scope of the claims.

Disclosed herein are inflatable structures for increasing perfusion during minimally-invasive cardiovascular procedures, increasing blood flow through the procedure site and/or reducing the need for rapid ventricular pacing. For example, the inflatable structures can be used in procedures for minimally invasive transcatheter heart valve replacement (TAVR), such as the procedures described in <CIT>.

Other balloons have been designed to enhance perfusion during cardiovascular procedures by incorporating a central lumen through which blood can flow during the procedure. Current perfusion balloon designs, such as the one described in <CIT>, include multiple balloons positioned radially around a central lumen. However, these balloons are cylindrical in shape, and can slip into the central lumen when the native annulus or valve applies a force upon the structure. Without being wed to theory, the inventors believe the movements are caused by a lack of contact between the balloons. The inflated cylindrical balloons are only in contact with each other in a line along the vertex of each diameter, making it easy for them to slip into the central lumen.

Generally, the inflatable structures disclosed herein facilitate the perfusion of blood through an anatomical structure, such as a heart valve, during a procedure. The inflatable structures are formed of a plurality of balloons arranged radially around a central opening. In particular, the plurality of balloons are arranged to form a lumen through which blood flows. The individual balloons of the plurality have a shape that facilitates the arrangement. For example, the individual balloons can have a keystone or wedge-like shape when viewed in cross section. The keystone or wedge-like shape limits the extent that individual balloons can move inward toward the lumen. Some embodiments can also include a support coil running through the lumen to maintain the open configuration of the lumen in the early stages of inflation of the balloons. Methods of using the inflatable structures are also disclosed herein.

<FIG> illustrate a delivery catheter assembly <NUM> including a delivery sheath <NUM> for delivering a prosthetic implant <NUM>, such as a prosthetic heart valve, to a patient. It should be understood that the delivery assembly <NUM> described herein is exemplary only, and that other similar delivery systems can of course be used. The delivery assembly <NUM> generally includes a steerable guide catheter <NUM> and a balloon catheter <NUM> extending through the guide catheter <NUM>. The guide catheter <NUM> can also be referred to as a flex catheter, a delivery catheter, or a main catheter. The use of the term main catheter should be understood, however, to include flex or guide catheters, as well as other catheters that do not have the ability to flex or guide through a patient's vasculature.

The guide catheter <NUM> and the balloon catheter <NUM> illustrated in <FIG> are adapted to slide longitudinally relative to each other to facilitate delivery and positioning of prosthetic heart valve <NUM> at an implantation site in a patient's body, as described in detail below.

The guide catheter <NUM> includes a handle portion <NUM> and an elongated guide tube, or shaft, <NUM> extending from handle portion <NUM> (<FIG> shows the delivery apparatus without the guide tube <NUM> for purposes of illustration. <FIG> shows the guide tube <NUM> extending from the handle portion <NUM> over the balloon catheter <NUM>. The balloon catheter <NUM> includes a proximal portion <NUM> (<FIG>) adjacent handle portion <NUM> and an elongated shaft <NUM> that extends from the proximal portion <NUM> and through handle portion <NUM> and guide tube <NUM>. The handle portion <NUM> can include a side arm <NUM> having an internal passage which fluidly communicates with a lumen defined by the handle portion <NUM>.

An inflatable balloon <NUM> is mounted at the distal end of balloon catheter <NUM>. As shown in <FIG>, the delivery assembly <NUM> is configured to mount the prosthetic heart valve <NUM> in a crimped state proximal to the balloon <NUM> for insertion of the delivery assembly <NUM> and prosthetic heart valve <NUM> into a patient's vasculature, which is described in detail in <CIT> (<CIT>). Because prosthetic heart valve <NUM> is crimped at a location different from the location of balloon <NUM> (e.g., in this case prosthetic heart valve <NUM> desirably is crimped proximal to balloon <NUM>), prosthetic heart valve <NUM> can be crimped to a lower profile than would be possible if prosthetic heart valve <NUM> was crimped on top of balloon <NUM>. This lower profile permits the surgeon to more easily navigate the delivery assembly <NUM> (including crimped prosthetic heart valve <NUM>) through a patient's vasculature to the treatment location. The lower profile of the crimped prosthetic heart valve <NUM> is particularly helpful when navigating through portions of the patient's vasculature which are particularly narrow, such as the iliac artery. The lower profile also allows for treatment of a wider population of patients, with enhanced safety.

<FIG> also illustrates an expandable sheath <NUM> that extends over the guide tube <NUM> and the elongated shaft <NUM> of the balloon catheter <NUM>. The expandable sheath <NUM> has a lumen to guide passage of the prosthetic heart valve <NUM>. At a proximal end the expandable sheath <NUM> includes a hemostasis valve that prevents leakage of pressurized blood. The delivery assembly <NUM> also includes a hub <NUM> for connecting with the proximal end of the expandable sheath <NUM> (shown in <FIG>).

Generally, during use, the expandable sheath <NUM> is passed through the skin of patient (usually over a guidewire) such that the distal end region of the expandable sheath <NUM> is inserted into a vessel, such as a femoral artery, and then advanced to a wider vessel, such as the abdominal aorta. The delivery assembly <NUM> is then inserted into the expandable sheath <NUM>, by first inserting the nose piece <NUM> through the hemostasis valve at the proximal end of the sheath <NUM>. The steerable guide tube <NUM> is used to advance the balloon catheter <NUM> shaft <NUM> and prosthetic heart valve <NUM> through to and out of the end of the sheath <NUM>. During the advancement of the prosthetic heart valve <NUM> through the sheath <NUM>, the prosthetic heart valve <NUM> exerts a radially outwardly directed force on the sheath <NUM>, causing it to expand. As the prosthetic heart valve <NUM> passes through the expandable sheath <NUM>, the sheath <NUM> returns to its original, non-expanded configuration. When the delivery assembly <NUM> is at the desired procedure site, the prosthetic heart valve <NUM> is expanded (for example, by balloon inflation or by self-expansion) to implant the device in the patient's body. If the prosthetic heart valve <NUM> is positioned proximally to the balloon <NUM> to reduce the profile of the delivery assembly <NUM> (as shown in <FIG>), the balloon <NUM> can be retracted proximally with respect to the prosthetic heart valve <NUM>, slipping into the lumen of the prosthetic heart valve <NUM> to enable balloon <NUM> inflation.

<FIG> shows sectional view of a vessel containing the balloon catheter <NUM> with the prosthetic implant <NUM> mounted upon the inflatable structure <NUM>. In this example, the prosthetic implant <NUM> is a prosthetic heart valve. The inflatable structure <NUM> and prosthetic heart valve <NUM> have been routed through the patient's blood vessel <NUM> for positioning within the patient's native cardiac valve annulus <NUM> schematically represented by thickened wall structure of the vessel. In <FIG>, the inflatable structure <NUM> is not yet inflated and the prosthetic heart valve <NUM> is not yet expanded. The large arrows indicate the flow of blood around the exterior surfaces of the inflatable structure <NUM> and the prosthetic heart valve <NUM>. As it is not inflated, the balloon catheter <NUM> is not substantially interfering with blood flow.

<FIG> shows another sectional view of the blood vessel <NUM> where the inflatable structure <NUM> has been inflated and the prosthetic heart valve <NUM> expanded within the native cardiac valve annulus <NUM>. The inflatable structure <NUM> includes a plurality of radially arranged balloons <NUM> that form a lumen <NUM> that facilitates passage of blood flow even after inflation, as shown in the cross sectional view of <FIG> (taken along section line 2C-2C of <FIG>). In particular, <FIG> shows a shaded area in the lumen <NUM> representing blood flow through the lumen.

In <FIG>, the black arrows represent the blood flowing in between the ends of the balloons <NUM> which are spaced apart from each other in the inflatable structure <NUM>. In particular, the balloons <NUM> have a smaller diameter, tapering structure at their ends that results in openings <NUM> between them providing access for the blood from outside the inflatable structure <NUM> to the central lumen <NUM>.

Referring again to <FIG>, the balloons <NUM> can be shaped to facilitate preservation of their arrangement around the central lumen <NUM>. In one aspect, the individual balloons <NUM> have a keystone or wedge-like cross-sectional shape that provide flat, radially oriented surfaces. These surfaces thus allow the balloons <NUM> to be arranged like pie pieces in a stable cylindrical configuration. Thus, advantageously, the keystone or wedge-like shape limits the extent that individual balloons <NUM> can move inward toward the lumen <NUM>.

The inflatable structure <NUM> can be formed by placing the individual balloons <NUM> into parallel fluid communication with the distal end of the balloon catheter <NUM>. For example, the proximal ends <NUM> of the individual balloons <NUM>, each with an inflation lumen extending therethrough, are heat fused to the distal end of balloon catheter <NUM> to create a sealed joint. The sealed joint contains the bundled ends with the inflation lumens of each balloon <NUM> converging at the inflation lumen of the balloon catheter <NUM> into a manifold configuration so that fluid can move between the balloon catheter <NUM> and the inflation lumens of the balloons <NUM>.

As shown in <FIG>, the balloons <NUM> can be collectively pleated and folded and crimped to a relatively small profile for delivery to the site of the procedure. For example, the crimped assembly can take on a profile that can be navigated through a range of vasculature and to the implantation site. The route of navigation can, for example, be transfemoral, transapical, or transaortic. Once the site of the procedure is reached, fluid (liquid or gas) is routed through balloon catheter <NUM>, through the sealed joint at the distal end of the balloon catheter <NUM> which separates and directs the fluid into each of the plurality of balloons <NUM> individually. In some implementations of the method, the balloons <NUM> can inflate simultaneously for a uniform shape change, such as into the radially arranged inflatable structure <NUM> shown in <FIG>.

In some methods, an implantable device, such as a replacement heart valve or other implant, is positioned around the outer perimeter of the inflatable structure <NUM> during navigation through the patient's vasculature. Inflation of the inflatable structure <NUM> causes expansion of the heart valve or other implant. Other medical implants that can be delivered using the inflatable structure <NUM> include, for example, stents or annuloplasty devices. However, the inflatable structure <NUM> can be used without delivering an implant, for example, to widen a narrowed or blocked blood vessel or a stenosed native heart valve.

As shown in <FIG>, which is a partial cross-section of the inflatable structure <NUM> and prosthetic heart valve <NUM> taken along section line 2D-2D of <FIG>, the balloon catheter <NUM> can include a support coil <NUM> extending through the lumen <NUM> and over the guidewire <NUM>. The support coil <NUM> has a wire or other linear, elongate material wound in a helical direction along the elongate axis <NUM> of the balloon catheter <NUM>.

<FIG> shows the support coil <NUM> separated from the inflatable structure <NUM>. The support coil <NUM> has a dumbbell shape with a tubular central region <NUM> connecting bulbous end regions <NUM>. The central region <NUM> of the support coil <NUM> has a dense pitch to provide support and narrower diameter than the end regions <NUM> to provide clearance for crimping on of the prosthetic heart valve <NUM>. The central region's <NUM> smaller diameter thus helps to keep the overall profile of the balloon catheter <NUM> low when a prosthetic heart valve <NUM> is crimped or compressed thereon.

The diameter of each end region <NUM> thus increases progressively until reaching a maximum diameter and then decreases progressively back to approximately a diameter matching the diameter of the central region <NUM>. The pitch of end regions <NUM> is less dense to facilitate blood flow through the wires and into the lumen <NUM>. In addition, the larger diameter portions of end regions <NUM> help to prevent the ends of the balloons <NUM> from blocking blood flow through lumen <NUM>. The inflatable structure's <NUM> lumen <NUM> is kept widened or flared at the ends by the progressively expanding diameter of the end regions <NUM>.

In some implementations, such as the one shown in <FIG>, the support coil <NUM> eliminates the need for guidewire tube <NUM>. The support coil <NUM> therefore provides a lumen <NUM> and a guidewire passage without increasing the profile of the inflatable structure <NUM>. For example, a support coil <NUM> with a <NUM> millimeters (<NUM> inch) wall thickness can replace an inner guidewire tube <NUM> with a wall thickness of <NUM> millimeters (<NUM> inch) and still have enough space for the passage of a guidewire <NUM> and blood perfusion during the initial stages of inflation.

The support coil <NUM> can be attached or coupled to the balloon catheter <NUM> in a number of ways. The end regions <NUM> of the support coil <NUM> can be glued, bonded, or heat fused either to the guidewire tube <NUM>, the balloons <NUM>, and/or the nose piece <NUM>. During construction, the support coil <NUM> can be spaced from the guidewire tube <NUM> to maintain the lumen <NUM> of the inflatable structure <NUM> in an open configuration even prior to inflation of the balloons <NUM>. The ability of the blood to perfuse the inflatable structure <NUM> through the support coil <NUM> prior to full inflation prevents the buildup of blood behind the structure <NUM>. This increases the stability of the structure within the procedure site during the positioning phases of the procedure.

<FIG> shows a cross-sectional schematic of the inflatable structure <NUM> of various embodiments during the early stages of inflation. Even a slight degree of inflation opens the lumen <NUM> to provide some passage for blood flow through the surrounding cardiovascular structure. For example, the opening of the lumen <NUM> enables blood to flow through the native heart valve and annulus during delivery and expansion of the prosthetic heart valve <NUM>. The support coil <NUM> helps to maintain the lumen <NUM> in an open state during the early inflation stages, increasing the stability of the structure by preventing a buildup of blood and a concomitant upstream pressure increase.

Although a coil is illustrated in the figures, the support coil <NUM> could be replaced with other elongate, hollow structures that have a porosity to allow or facilitate perfusion. The support coil <NUM> could be replaced with a braided tube or a selectively cut tube. For example, the tube could be pierced or cut to have pores, holes or slots or combinations thereof.

Because perfusion begins at the initial stages of inflation, an interventionist has more time to complete the procedure than if blood perfusion were blocked by a conventional balloon. The interventionist can inflate the balloons <NUM> slowly and carefully for improved anchoring of the implant to the valve annulus. Slow inflation is advantageous because it gives physician time to accurately position the prosthetic heart valve <NUM>. Slow inflation can also give time for calcified blood vessels to adjust to the round valve shape with minimal rupture of the surrounding tissue.

In some example methods, the transcatheter heart valve or other medical implant can be partially expanded by only partially inflating the inflatable structure <NUM>. This provides an opportunity for the interventionist to reposition the implant prior to completing the inflation and anchoring the implant to the tissue. Perfusion of the procedural site occurs during the repositioning of the device which results in increased safety for the patient.

Some embodiments, such as those shown in <FIG>, can include a surrogate valve <NUM> attached just proximal of the proximal ends of the balloons <NUM> for a transfemoral prosthetic aortic heart valve delivery procedure. The surrogate valve <NUM> mediates backflow of perfused blood in the distal direction (with respect to the catheter) upon inflation of the inflatable structure <NUM> and opening of the perfusion lumen <NUM>. As shown in <FIG>, the surrogate valve <NUM> has a plurality of leaflets <NUM> and a base <NUM>. The base <NUM> is positioned at the proximal end of the inflatable structure <NUM> and is attached to the balloon catheter <NUM>. The leaflets <NUM> extend over the outside of the balloons <NUM> and in particular can block the openings <NUM> between the proximal balloon ends.

In other embodiments, the surrogate valve <NUM> can be positioned inside the lumen <NUM> formed by plurality of balloons <NUM> of inflatable structure <NUM>. In this configuration, the leaflets <NUM> extend inside the openings <NUM>.

The position of the surrogate valve <NUM> along the length of the balloon catheter <NUM> can also be varied depending upon the desired procedure. For example, for a transapical prosthetic aortic heart valve delivery procedure, primary perfusion flow would be desired in the distal direction (with respect to the catheter). Thus, the surrogate valve <NUM> can be positioned at the distal end of the inflatable structure <NUM>-to collapse and block the openings <NUM> against retrograde flow in the proximal direction.

Regardless, the leaflets <NUM> of surrogate valve <NUM> take a closed position during diastole to prevent backflow of blood through the procedural site, as shown in <FIG>. During systole, the leaflets <NUM> of surrogate valve <NUM> are pushed open by the fluid pressure to permit perfusion of blood through the procedural site, as shown in <FIG>.

The surrogate valve <NUM> can be made with a range of thin, flexible and biologically compatible materials that can fold and bend under normal blood pressure. For example, the surrogate valve <NUM> can be constructed of the same material or structure as tissue-based or prosthetic valves intended for permanent implantation. In the illustrated embodiments, the leaflets <NUM> flare out into sets of three finger-like projections as they extend away from the base <NUM> and over the increasing diameter of the inflatable structure <NUM>. Multiple leaflets <NUM> are arranged around the peripheral circumference of the inflatable structure <NUM>.

Various additional embodiments of inflatable structures <NUM> are shown as simplified cross-sectional schematics in <FIG> to illustrate additional stable configurations that facilitate the balloons <NUM> maintaining their collective inflatable structure <NUM> with the central lumen <NUM>. In all of the <FIG>, the plurality of balloons <NUM> are arranged radially around the central axis <NUM>, forming the lumen <NUM>. The number of balloons <NUM> can vary - with the illustrated embodiments being six or eight balloons <NUM>. However, the inflatable structure <NUM> can be made up of as few as four balloons <NUM>, or as many as <NUM> balloons <NUM>.

Each of the balloons <NUM> of the inflatable structures <NUM> shown in the simplified cross sections of <FIG> is non-circular in cross-section. Each of the cross-sections shown has two substantially straight side portions <NUM>. The term "substantially straight side portion" is intended to describe a portion of an outer perimeter of a balloon <NUM> when viewed in cross-section. The substantially straight side portions <NUM> can also have a length in the axial direction. Some embodiments can have substantially straight side portions <NUM> along the entire length of the balloon <NUM>. Other embodiments can have substantially straight side portions <NUM> along only a part of the length of the balloon <NUM>.

When the inflated balloons <NUM> are radially arranged to form the larger inflatable structure <NUM>, each substantially straight side portion <NUM> abuts a substantially straight side portion <NUM> of an adjacent balloon <NUM>. This abutment prevents the balloons <NUM> from slipping into the lumen <NUM> of the inflatable structure <NUM>. While the cross-sections shown in <FIG> show balloons <NUM> with fully abutting substantially straight side portions <NUM>, in other embodiments the substantially straight side portions <NUM> can abut only partially. Some embodiments include balloons <NUM> with more than two substantially straight side portions <NUM>.

The cross section of each balloon <NUM> shown in <FIG> also has an inner portion <NUM> and an outer portion <NUM> extending between the at least two substantially straight side portions <NUM>. The length of the outer portion <NUM> is greater than the length of the inner portion <NUM>. This difference in width contributes to the wedge shape and further prevents the balloons <NUM> from slipping into the lumen <NUM> of the inflatable structure <NUM>.

In some embodiments, the balloons <NUM> are polygonal in cross-section. For example, the balloons <NUM> can be trapezoidal in cross-section, as shown in <FIG>. In some embodiments, such as those shown in <FIG>, the inner portion <NUM> of the balloon <NUM> curves inward into the lumen <NUM> of the inflatable structure <NUM>. In some embodiments, such as those shown in <FIG>, the inner portion <NUM> curves outward away from the lumen <NUM>. In some embodiments, such as those shown in <FIG>, the inner portion <NUM> is substantially straight.

The outer portion <NUM> of the cross-section of the balloon <NUM> can curve outward away from the lumen <NUM> so that when they are assembled and inflated into the inflatable structure <NUM> it will approximate a cylinder, as shown in <FIG>. The outer portion of the balloon <NUM> can also be substantially straight, as in <FIG>. The outer portion <NUM> can also curve inward toward the lumen <NUM> of the inflatable structure <NUM>. Generally, then, the outer portion <NUM> can be shaped to accommodate the expected geometry of the vasculature or other body lumen it is meant to expand into.

The size of the inflatable structures <NUM> can also vary depending up on the particular application. For example, for prosthetic heart valve implantation, the perimeter measured around the outer surface of the inflatable structure <NUM> can range from about <NUM> to <NUM> millimeters, for example, <NUM>, <NUM>, <NUM>, or <NUM> millimeters.

Some embodiments, such as the one shown in <FIG>, can include an outer layer of material <NUM> (such as a sock or sleeve) extending around the plurality of balloons <NUM>. The outer layer of material <NUM> prevents balloons <NUM> from moving away from the central axis <NUM> and disrupting the radial arrangement of the plurality of balloons <NUM>. The outer layer <NUM> can be formed of materials that are flexible and conforming, such as, for example, plastic film or woven mesh. Generally, the outer layer of material <NUM> is shaped to conform the balloons <NUM> or not interfere with the balloons <NUM> taking the desired shape of the inflatable structure <NUM>. The thickness of the outer layer of material <NUM> can be <NUM> millimeters (<NUM> inches) or less for relatively low impact on the profile of the delivery catheter assembly <NUM>.

Some embodiments, such as the one shown in <FIG>, include an inner layer of material <NUM> that separates the inner faces of the balloons <NUM> from the lumen <NUM> of the inflatable structure <NUM>. The inner layer of material <NUM> prevents balloons <NUM> from moving inward toward the central axis <NUM> and disrupting the radial arrangement of the plurality of balloons <NUM>. The inner layer of material <NUM> can be formed of materials that are flexible and conforming, such as, for example, plastic film or woven mesh. The thickness of the inner layer of material <NUM> can be <NUM> millimeters (<NUM> inches) or less to minimize reduction in the size of the lumen <NUM>.

The inflatable structure <NUM>, as shown schematically in <FIG>, can include an attachment mechanism <NUM> positioned between the substantially straight side portions <NUM> of balloons <NUM>. The attachment mechanism <NUM> can be, for example, an adhesive, or string, a ribbon, a suture, a wire, or roughened surfaces, or any other mechanism that stabilizes the radial arrangement of the balloons <NUM>. The attachment mechanism <NUM> can be positioned between the sides of the balloon <NUM>, or it can span the inner faces or outer faces of the balloons <NUM>. The attachment mechanism <NUM> stabilizes the radial arrangement of the balloons <NUM> around the central axis <NUM> by further reducing a balloon's movement relative to the other balloons <NUM>.

<FIG> show perspective views of various types of balloons <NUM> separated from the larger inflatable structure <NUM>. In particular, the balloons <NUM> of<FIG> have varied shapes. <FIG>, for example, shows the balloon <NUM> having an inner face <NUM> that curves into the lumen <NUM> when assembled with other similar balloons <NUM> into the inflatable structure <NUM>. When assembled with other similarly constructed balloons <NUM> into the inflatable structure <NUM>, the inflatable structure <NUM> would have a cross-section reminiscent of <FIG>.

The balloon <NUM> also has a first end portion and a second end portion having substantially flat surfaces <NUM>. A balloon inflation leg <NUM> extends away from a first opening <NUM> on the first end portion of the balloon <NUM> and from a second opening (not shown) on the second end portion of the balloon <NUM>. In some embodiments, the balloon openings lie along a common axis extending through a center of the flat surfaces <NUM>. Alternatively, the balloon openings can be spaced away from the center or a common longitudinal axis depending upon inflation and manufacturing concerns. The openings and inflation leg <NUM> provide conduits for inflation fluid to flow from the inflation lumen <NUM> of the catheter to the interior of the balloon <NUM> and in reverse for deflation.

<FIG> shows another embodiment of the balloon <NUM> separate from the larger inflatable structure <NUM>. The balloon <NUM> of <FIG> also has the inner face <NUM> that curves into the lumen <NUM> of the larger inflatable structure <NUM>. When assembled with other balloons <NUM> into the inflatable structure <NUM>, the inflatable structure <NUM> would have a cross-section reminiscent of <FIG>. The balloon <NUM> also has a first end portion and a second end portion. The first end portion has a taper <NUM> that narrows extending away from the body portion <NUM> of the balloon <NUM>. One end portion can have the taper <NUM> while the other has a substantially flat surface <NUM>, as shown in <FIG>. Or, both end portions can have the taper <NUM>. The taper can mediate the material stress in the balloon <NUM> caused by a more sudden transition in diameter.

<FIG> show embodiments of balloons <NUM> with inner faces <NUM> that curve outward away from the lumen <NUM> of the larger inflatable structure <NUM>. When assembled with other balloons <NUM> into the inflatable structure <NUM>, the inflatable structure <NUM> would have a cross-section reminiscent of <FIG>. The balloon <NUM> of <FIG> has end portions with substantially flat surfaces <NUM>. The balloon <NUM> of <FIG> has a first end portion with the taper <NUM>, and a second end portion with a substantially flat surface <NUM>.

Body portions <NUM> of the balloon embodiments shown in <FIG> have consistent cross-sectional areas along the working lengths of the balloons <NUM>. However, in some embodiments, the cross-sectional area of the body portion <NUM> changes along the length of the balloon - such as by having a tapering body portion. The cross-sectional area of the body portion <NUM> can be larger than that of a tapered end portion, as seen in <FIG>. The cross-sectional area of the body portion <NUM> can also be less than the largest cross-sectional area of an end portion so as to form an enlarged end to help anchor the balloons <NUM> or to retain the implant. These variations can also be configured to fit the different expected sizes the body lumens or implants.

In some embodiments, the inflatable structure <NUM> can be made up of multiple groupings of balloons <NUM> positioned along the central axis of the larger inflatable structure <NUM>. For example, a first grouping or balloons <NUM> can be arranged radially about the central axis <NUM> of the larger inflatable structure <NUM>, and a second grouping of balloons <NUM> can be arranged radially about the central axis <NUM> and positioned longitudinally adjacent to the first grouping of balloons <NUM>. This allows, for example, building up the inflatable structure <NUM> to a desired diameter and length.

<FIG> shows a cross-section of another embodiment wherein the balloon <NUM> has webbing <NUM> extending through the interior portion <NUM> of the balloon <NUM>. In particular, the webbing <NUM> extends between and connects straight side portions <NUM>. <FIG> shows a cross-section of another inflatable structure <NUM> embodiment formed from balloons <NUM> with webbing <NUM> extending through their interior portions <NUM>.

Advantageously, the webbing <NUM> facilitates the retention of side portions <NUM> in a substantially straight configuration upon inflation. For example, <FIG> shows a cross section of an uninflated balloon <NUM> and <FIG> shows a cross section of the same balloon <NUM> after inflation. Upon inflation, the walls of the balloon <NUM> expand and the cross section becomes circular in shape. Meanwhile, the uninflated balloon <NUM> shown in <FIG> has webbing <NUM> extending through the interior portion <NUM>. Upon inflation, as shown in <FIG>, the side portions <NUM> of the balloon retain their substantially straight configuration. The balloon <NUM> can have more than one piece of webbing <NUM>, such as the two webs <NUM> of <FIG>, extending through its interior portion <NUM>. Additional webs <NUM> can be employed depending upon the desired allocation of their effect on the balloon shape. Various portions of the walls of the balloons <NUM> can be shaped - made flat or pinched, for example - through use of more webs to meet the varied shapes of patient lumens and/or of the implantable devices.

<FIG> schematically depict an inflatable structure <NUM> including a plurality of balloons <NUM> each including interlocking mechanisms that stabilize adjacent balloons <NUM> to limit movement. The interlocking mechanism includes a protrusion <NUM> extending from a substantially straight side portion <NUM> of a first balloon <NUM>. The protrusion <NUM> is shaped to nest within a recession <NUM> in the substantially straight side portion <NUM> of an adjacent, second balloon <NUM>. For example, the protrusion <NUM> in <FIG> has a U-shape with the rounded end pointing away from the straight side portion <NUM>. Correspondingly, the recession <NUM> has a U-shape with the rounded end pointing into the balloon <NUM>. The U-shape can be an extruded shape that extends the length of the balloon <NUM> body or it can be a cylinder topped with a rounded dome and corresponding features on the recession <NUM>.

Though the embodiment of <FIG> has only one protrusion and recession per balloon <NUM>, a balloon <NUM> can have multiple protrusions <NUM> corresponding to multiple recessions <NUM> on an adjacent balloon <NUM>. The multiple protrusions <NUM> and recessions <NUM> can be distributed radially between the adjacent balloon <NUM> surfaces. For example, in a cross-section such as the schematic of <FIG>, two, three or more protrusions <NUM> can be at radially spaced intervals along the adjacent side portions <NUM> of the balloons <NUM>. Multiple protrusions <NUM> and recessions <NUM> can also be distributed along the length of the balloons <NUM>.

The shapes and dimensions of the protrusion <NUM> and recession <NUM> can vary based on factors such as desired security and ease of interlock. The interlocking mechanism shown in <FIG> is dome shaped, which advantageously provides a large surface area for interlock of the balloons <NUM>. However, protrusion <NUM> and recession <NUM> could be shaped differently and still function to limit the movement of balloons <NUM> relative to each other. For example, the opposing side portions <NUM> of adjacent balloons <NUM> can have complementary zig zag sections configured to engage one another.

<FIG> shows a balloon mold <NUM> for fabricating the balloons <NUM> with interlocking mechanisms. The balloon mold <NUM> is constructed of two halves. The halves are joined together to form a cavity using, for example, press-fit pins and/or set screws. The cavity of the balloon mold <NUM> then has a shape defining the curved shapes of the inner portion <NUM> and outer portion <NUM>, the straight side portions <NUM> and the corresponding U-shaped protrusion <NUM> on one side and recession <NUM> on the other. The wall thickness is set by having a smaller profile but correspondingly shaped mandrel inserted through the cavity of the balloon mold <NUM>. The mandrel's size difference defines the wall thickness of the balloon <NUM> - a smaller mandrel results in a bigger wall thickness.

An extrusion process is performed by pressurizing a liquid polymer within a closed housing or tube having an opening within which is secured the periphery of the balloon mold <NUM> with the mandrel extending therethrough. As the pressure builds the liquid polymer pushes over the mandrel and under the edges defining the cavity to create a correspondingly shaped wall structure for the balloon. This shape can be then sealed off on its ends through conventional processes.

Claim 1:
A balloon catheter for insertion into a body lumen with blood flowing therethrough, the balloon catheter comprising:
an elongate member (<NUM>) defining an inflation lumen, the elongate member (<NUM>) having a proximal end and a distal end; and
a plurality of balloons (<NUM>) coupled to the distal end of the elongate member (<NUM>) and connected in fluid communication with the inflation lumen of the elongate member (<NUM>),
wherein the balloons (<NUM>) are arranged circumferentially about a central axis (<NUM>) so as to form a lumen (<NUM>) extending along the central axis (<NUM>) and wherein the lumen (<NUM>) is configured to allow passage of the blood therethrough,
wherein each of the balloons (<NUM>) comprises a non-circular cross-sectional shape having at least two substantially straight side portions (<NUM>) extending radially relative to the central axis (<NUM>), and
wherein each substantially straight side portion (<NUM>) at least partially abuts the substantially straight side portion (<NUM>) of an adjacent one of the balloons (<NUM>),
characterized in that the balloon catheter further comprises an elongate, hollow structure (<NUM>) having porosity and being coupled to the distal end of the elongate member (<NUM>), the hollow elongate structure (<NUM>) extending along the central axis (<NUM>) within the lumen (<NUM>) and at least partially supporting the balloons (<NUM>), wherein the porosity allows perfusion of blood through the lumen (<NUM>) prior to full inflation of the balloons (<NUM>).