Patent Description:
The present invention relates to an intravascular medical system. In particular, the present invention is directed to an improved balloon guide catheter with positive venting of residual air trapped therein while being prepped by the physician or interventionalist prior to being introduced into the body.

Catheters are widely used today in connection with a variety of intravascular medical procedures or treatments. One such widely adopted use or application of an intravascular catheter is in a thrombectomy medical procedure following an acute ischemic stroke (AIS) in which a sheath guide catheter (non-balloon guide catheter) or balloon guide catheter is introduced into the internal carotid artery to serve as a conduit for ancillary devices such as guidewire(s), microcatheter(s), stentriever(s) or intermediate catheter(s). The sheath guide catheter (non-balloon guide catheter) maintains access to the intended treatment location within a blood vessel and shortens procedural times by facilitating multiple passes with ancillary devices to the treatment location. Use of a balloon guide catheter provides the additional benefit, once inflated to an expanded state, of arresting blood flow and achieving complete apposition of the vessel. The blood flow arrest offers extra security in limiting the blood pressure exerted on the clot as well as maximizing the suction performance during aspiration stage, as the stentriever and/or direct aspiration catheter retracts back into the balloon guide catheter with the captured clot. While such benefits are readily apparent and clinically proven, use of a balloon guide catheter requires somewhat arduous prepping steps be followed in ridding the inflating lumen of residual air to be replaced with inflating medium both in the inflating lumen and the balloon. These prepping steps performed prior to the introduction of the balloon guide catheter into the body deter some physicians or interventionalists from using a balloon guide catheter altogether despite such advantages, instead choosing to employ a sheath guide catheter (non-balloon guide catheter) that doesn't require such prepping steps.

Prior to being introduced into the target vessel of the body, a conventional balloon guide catheter is prepped by the physician or interventionalist following a multi-step process to properly purge residual air trapped therein. This preparatory procedure typically calls for applying a vacuum or negative pressure at an inflation port to remove the residual air, followed immediately thereafter by dispensing of an inflation medium back into the catheter. This inflation lumen vacuum procedure may be required to be repeated multiple times to insure complete expulsion of the residual air. If the purging steps are not followed correctly or skipped over entirely, the residual air in the balloon guide catheter may be exhausted into the blood vessel, in the event of a balloon failure, having a dangerous and harmful effect on the patient. <CIT> describes a balloon catheter having a purge hole provided in the distal end side of, and at the location close to the end of, a catheter main body covered by a balloon. <CIT> describes a self-venting balloon dilatation catheter. <CIT> describes a balloon guiding sheath. <CIT> describes a catheter purge device. <CIT> describes a stretch valve balloon catheter.

It is therefore desirable to streamline the number of steps or actions to purge residual air from the balloon guide catheter increasing its desirability and ease of use while optimizing time efficiency as well reducing the potential for human error.

The invention is defined by independent claims <NUM> and <NUM>. Embodiments of the invention are defined by the dependent claims. An aspect of the present invention is directed to an improved balloon guide catheter that minimizes the number of prepping steps or actions to rid the device of residual air.

Another aspect of the present invention relates to an improved balloon guide catheter with positive venting.

Yet another aspect of the present invention is directed to an improved balloon guide catheter in which the location of the exhaust and inflating vents ensures that inflation of the balloon with inflating medium occur only upon full and complete bleeding of the residual air from the inflating lumen.

Still another aspect of the present invention relates to an improved guide catheter in which the inflating medium serves a dual function or purpose, initially to purge the residual air from the inflating lumen and, once bled, thereafter to inflate the balloon.

While yet another aspect of the present invention is directed to an improved balloon guide catheter that when prepped by the physician or interventionalist is visibly verifiable that the balloon has been properly purged of residual air prior to introduction into the patient.

It is yet another aspect of the present invention to provide an improved balloon guide catheter with positive venting in which residual air is purged prior to introduction into the body, thereby eliminating the need for a vacuum or negative pressure during prepping.

An aspect of the present invention is directed to a balloon guide catheter including a catheter shaft having an outer surface, a proximal end, and an opposite distal end. The catheter shaft has a main lumen defined therein extending axially therethrough from the proximal end to the distal end. The main shaft is configured to receive a guidewire therein; the catheter shaft having an inflation lumen defined axially therein arranged semi-encircling the main lumen; the inflation lumen having an inlet vent defined radially outward from the catheter shaft and at least one exhaust vent disposed proximate the distal end of the catheter shaft, wherein the at least one exhaust vent being disposed longitudinally through a distal terminating end of the inflation lumen or radially inward in fluid communication with the main lumen. The catheter further includes a porous membrane disposed at the at least one exhaust vent, wherein the porous membrane having a plurality of holes defined therein sized to permit only gas to pass therethrough. In addition, the catheter also has an expandable balloon secured about the outer surface of the catheter shaft proximate the distal end of the catheter shaft and coinciding with the inlet vent.

A still further aspect of the present invention is directed to a method of manufacture of a positive distal vented balloon guide catheter. The method including the steps of forming a tubular main liner to form a main lumen axially therethrough; the formed tubular main liner having an etched region and a polymeric strike layer at selected surfaces. A first opening is punched radially through the formed tubular main liner that serves as a radial exhaust vent in fluid communication with the main lumen defined axially therethrough. A provided microporous membrane etched and having a polymeric strike layer at selected sections of both surfaces of the microporous membrane is positioned to cover the punched exhaust vent defined in the formed tubular main liner. The formed tubular main liner is laminated to attached together with the microporous membrane under an application of heat. Thereafter, a polymer jacket is positioned over the laminated assembly including the mandrel, the formed tubular main liner, and the microporous membrane; and heat shrink is applied to cause reflow of the polymer jacket bonding the polymer jacket to the etched/strike layer of the microporous membrane as well as to the etched/strike layer of the formed tubular main liner. In a similar fashion a tubular inflation liner is formed having an inflation lumen axially therethrough; the formed tubular inflation liner having an etched region and a polymeric strike layer at selected surfaces. A second opening s punched radially through the formed tubular inflation liner that serves as a radial exhaust vent in fluid communication with the inflation lumen defined axially therethrough. The second opening of the formed tubular inflation liner is positioned longitudinally relative to the first opening of the formed tubular main liner. At least one jacket is applied about the formed tubular inflation liner. Heat shrink is then applied to cause reflow of the at least one outer jacket forming a fused assembly to the braid, the formed tubular inflation liner to the formed tubular main liner. Thereafter the heat shrink is removed prior to attaching a balloon about the fused assembly. Optionally, prior to the step of positioning the second opening of the formed tubular inflation liner longitudinally relative to the first opening of the formed tubular main liner, the method may further include applying a braid or coil wound about: (i) the formed tubular main liner, not including the formed tubular inflation liner; (ii) the formed tubular main liner and including the formed tubular inflation liner; or (iii) the formed tubular main liner, wherein a part of the braid is wrapped about the formed tubular inflation liner, while another part of the braid is disposed between the formed tubular main liner and the formed tubular inflation liner.

Different embodiments are defined in the appended dependent claims.

The foregoing and other features of the present invention will be more readily apparent from the following detailed description and drawings illustrative of the invention wherein like reference numbers refer to similar elements throughout the several views and in which:.

The terms "distal" or "proximal" are used in the following description with respect to a position or direction relative to the treating physician or medical interventionalist. "Distal" or "distally" are a position distant from or in a direction away from the physician or interventionalist. "Proximal" or "proximally" or "proximate" are a position near or in a direction toward the physician or medical interventionalist. The terms "occlusion", "clot" or "blockage" are used interchangeably.

Conventional balloon catheters have a coaxial design wherein a central lumen disposed centrally of the balloon catheter receives a guidewire therethrough while an inflation lumen is disposed coaxially about and completely/fully encircling the central lumen. The present inventive balloon guide catheter is designed so that the inflation lumen partially-encircles or semi-encircles the main lumen, i.e., the inflation lumen does not completely encircle the inflation lumen. Moreover, the center of the inflation lumen may, but need not necessarily, share the same center as that of the main lumen. <FIG> is an alternative configuration of an exemplary radial cross-sectional view of the present inventive catheter illustrating the semi-encircling inflation lumen and main/guide lumen eccentrically arranged (the two lumens not sharing the same center, not concentric), whereas <FIG> is another configuration of an exemplary radial cross-sectional view of the present inventive catheter depicting the semi-encircling inflation lumen and main/guide lumen concentrically arranged (the two lumens sharing the same center).

When traversing a tortious path through the vessel of the body, the presently arranged inflation lumen provides improved deliverability by providing a shaft that may be connected throughout the shaft, a connectivity that is not provided with completely/fully encircling concentric (coaxial) conventional designs as concentric designs must be substantially unconnected between outer and inner shafts to provide a concentric lumen. Moreover, the conventional concentric (coaxial) design of the inflation lumen about the central lumen takes up a great deal of valuable cross section area between the inner surface and the outer surface of the catheter, that extends in a substantially uniform manner about the circumference of the catheter when compared to the present inventive partially/semi-encircling design which may have varied wall thickness between the inner surface and the outer surface of the catheter, that varies about the circumference of the catheter and allows for a reduced cross sectional area between the inner surface and the outer surface of the catheter. This variation in wall thickness about the circumference of the catheter allows for a larger inner diameter for a given outer diameter when compared to a conventional fully/completely encircling coaxial design because less material is required to define the inflation/deflation lumen for a given lumen cross sectional area. Ideally, the inner diameter of the present inventive partially/semi-encircling design maintains circularity throughout the catheter shaft to accommodate ancillary devices which mostly maintain circularity longitudinally and the outer surface deviates from circularity to slight ovality in order to accommodate the inflation/deflation lumen. The larger inner diameter for a given outer diameter allows the present inventive catheter to receive ancillary devices with larger outer diameters than would be otherwise accommodated with fully/completely encircling concentric designs with the same given outer diameter. Further, the larger inner diameter of the present inventive design will allow for greater aspiration (co-aspiration with an intermediate catheter) flow rates for a given aspiration vacuum pressure. The greater aspiration flow rate serves to enhance flow reversal within the target treatment location and applies a greater suction force to the face of a clot in the vessel aiding in successful retrieval of the clot with aspiration alone or in conjunction with a stent retriever. It is appreciated that the inner and outer surfaces of the present inventive partially/semi-encircling design may both have ovality. Additional embodiments that maintain outer circularity with inner ovality may also be envisaged. Embodiments with inner ovality will be advantageous in a balloon guide catheter when combined with an inner intermediate catheter having circularity because the extra volume provided between the inner oval cross section of the balloon guide catheter and the outer circular cross section of the intermediate catheter provides additional cross section area between the catheters that can be utilized for aspiration flow. Therefore, when accommodating a given intermediate catheter with outer circularity in balloon guide catheters with a given outer diameter, a balloon guide catheter with an inner ovality will allow for greater aspiration flow rates compared to a balloon guide catheter with an inner circularity, especially so for a concentric design as it will also require a greater cross-sectional area for the wall thickness of the catheter to accommodate the inflation/deflation lumen.

Referring to the longitudinal cross-sectional view depicted in <FIG>, the present inventive positive venting balloon guide catheter eliminates the need for a vacuum or negative pressure typically required when prepping conventional devices. The inventive balloon guide catheter includes a catheter shaft or body <NUM> having a main/central lumen <NUM> defined longitudinally therethrough for receiving a guidewire or other ancillary device. Also defined in the catheter shaft or body <NUM> is an inflation lumen <NUM> disposed radially outward from and partially/semi-encircling the main/central lumen <NUM> (but not sharing a common center), as illustrated in the radial cross-sectional view in <FIG>. A proximal end of the inflation lumen is in fluid communication with an inflation port <NUM>. As shown in <FIG>, inflation port <NUM> is typically angled radially outward relative to that of the catheter body <NUM>. A manual device (e.g., a syringe) <NUM> or an automated pressure device can be attached at a proximal inflation port <NUM> to generate a positive pressure by dispensing an inflation medium (e.g., liquid) into the inflation lumen <NUM>. The inflation medium is preferably a liquid solution, such as a solution containing water, distilled water, deionized water, heparin, saline, contrast medium/agent or some combination thereof. In a preferred embodiment the inflation medium is a solution of contrast medium and saline, most preferably a solution of a <NUM>:<NUM> ratio of contrast medium to saline. The inflation medium solution is typically stored at room temperature.

The inflation lumen <NUM> has one or more exhaust vents defined therein. These exhaust vents may be configured to expunge/purge residual air trapped in the inflation lumen in a radial direction, a longitudinal direction or both. In the example shown in <FIG>, residual air is purged out from two exhaust vents <NUM>, <NUM>', both disposed towards a distal end <NUM> of the catheter. One of the exhaust vents <NUM> is disposed proximally of a distal tip or end <NUM> of the catheter and defined radially inward in the catheter shaft or body <NUM> serving as a conduit for fluid communication of the purged residual air between the inflation lumen <NUM> and the main/central lumen <NUM>. The other exhaust vent <NUM>' is arranged longitudinally at the distal tip or end <NUM> of the inflation lumen <NUM>. It is contemplated and within the intended scope of the present invention to alternatively have either a radial exhaust vent or a longitudinal exhaust vent, rather than both. Moreover, if the balloon catheter has a radial exhaust vent more than one may be provided, as desired.

A microporous membrane <NUM> covers each of the exhaust vents <NUM>, <NUM>', wherein the pores of the microporous membrane are sized to permit only the passage of gas (e.g., residual air) therethrough, liquid (inflation medium) dispensed through the inflation lumen is prevented from permeating through the porous membrane allowing the pressure within the inflating lumen to build-up and inflate the balloon as the volume within the balloon fills with the inflation medium. Preferably, the microporous membrane is a certain grade (based on porosity and thickness) of sintered polytetrafluoroethylene (PTFE), for example, sintered polytetrafluoroethylene (ePTFE), that permits the passage of air molecules therethrough but acts as a barrier to larger molecules such as water, saline and contrast medium because of two attributes, (i) hydrophobic membrane and (ii) molar volume. The membrane is hydrophobic in nature and allows the membrane to repel relatively high tension (polar) fluids even with the presence of small pores in a non-pressurized system. Gases on the other hand pass easily through such membranes under very relatively low pressures. For instance, water vapor will pass through the ePTFE microporous membrane, however it is time dependent. With regards to the second factor, the size of the water and contrast medium molecules are greater than the air molecules permitting the air molecule to pass through the membrane containing numerous small pore sizes. In relation to the present invention, the relative sizes of the molecules are the dominant characteristic at play within this application time-frame of injecting fluid through a lumen, where air is expelled through a microporous membrane under relatively high pressure. The micropores of the ePTFE microporous membrane vary in size and are preferably in the size range of approximately <NUM> to approximately <NUM>, more preferably in the size range of approximately <NUM> to approximately100µm. <FIG> is an enlarged view of the dashed area 1C in <FIG> that clearly shows the microporous membrane <NUM> covering the radially disposed exhaust vent <NUM>. In <FIG> the microporous membrane <NUM> is disposed radially outward of the central lumen <NUM> (i.e., within the inflation lumen <NUM>). As desired, the microporous membrane may be disposed within the inflation lumen (<FIG>); the microporous membrane may be disposed entirely within the wall between the central and inflation lumens <NUM>, <NUM>, respectively; or a combination thereof in which a first portion of the microporous membrane extends radially inward into the wall between the inflation and central lumens while a second portion of the microporous membrane extends radially outward into the inflation lumen. Preferably, no portion of the microporous membrane extends radially inward into the central lumen since this could potentially result in a snag when passing therethrough an ancillary device.

The inflation lumen <NUM> extends axially through the catheter body <NUM> from proximate its proximal end <NUM> to its opposite distal tip or end <NUM>. An inflation/inlet vent <NUM> is defined radially outward through the catheter body <NUM> and serves as a conduit for the inflation medium between the inflation lumen <NUM> and a balloon <NUM> covering the inflation vent <NUM>. Balloon <NUM> is bonded or adhered to an outer surface of a distal portion of the catheter body <NUM> forming a seal over the inflation vent <NUM>. In the deflated state shown in <FIG>, the balloon <NUM> rests in physical contact against the inflation vent <NUM> temporarily preventing the passage of the inflation medium therethrough until the built-up pressure in the inflation lumen <NUM> exceeds a predetermined pressure of the opposing force exerted by the balloon <NUM>.

The embodiment shown in <FIG> depict the present inventive balloon catheter having a single inflation lumen. It is possible and within the intended scope of the present invention to have more than one inflation lumen. <FIG> depicts a dual inflation lumen design <NUM>', <NUM>" wherein the two inflation lumens are arranged side-by-side. In the first inflation lumen <NUM>', fluid flows through the lumen from the proximal end to the distal end, whereas fluid flows in an opposite direction through the second inflation lumen <NUM>" from the distal end to the proximal end. Another configuration of the dual inflation lumen design is shown in <FIG>. Here the dual inflation lumens are disposed one above and the other below the main/central lumen. That is, a first inflation lumen <NUM>' is arranged above the main/central lumen <NUM>, while the second inflation lumen <NUM>" is disposed below the main/central lumen <NUM>. The first inflation lumen <NUM>' having fluid flowing therethrough from the distal end to the proximal end has a microporous membrane <NUM> at the port so that residual gas is able to pass, but inflation medium is prohibited from passage through the membrane causing the balloon to inflate when the residual air has been purged, expelled or flushed from the system.

Perspective and longitudinal cross-sectional views of the assembled catheter in accordance with the present invention are depicted in <FIG>, respectively. While <FIG> depict a series of sequential steps or stages during assembly and manufacture of the catheter shown in <FIG>. Initially, in <FIG>, the main/central lumen <NUM> may be formed by wrapping a main/central liner <NUM> (e.g., made of PTFE) about a mandrel <NUM> to produce a formed main/central tube. Preferably, the mandrel <NUM> is a Silver Plated Coated (SPC) mandrel dipped with a PTFE layer (typically, approximately <NUM>,<NUM> (<NUM>") approximately <NUM>,<NUM> (<NUM>")) in wall thickness and is thereafter etched. A polymeric strike layer (e.g., a polyether block amide (PEBAX®) or urethane material) is coated over the etched PTFE. The wall thickness of the polymeric strike layer may be a few thousandths of an inch, but for this application a thickness of approximately <NUM>,<NUM> (<NUM>") would be sufficient to communicate and adhere with the reflowing polymer jacket materials, as described in detail below. Alternatively, a preformed tube may be used as the main/central tube. A first hole or opening is radially punched through the formed tubular main/central inner liner <NUM> (PTFE on the SPC mandrel) that serves as the radial exhaust vent <NUM> into the main/central lumen <NUM>. A selected grade (based on desired porosity & thickness) of sintered PTFE forming the microporous membrane <NUM> is cut either from a patch or from a tubular configuration for easier mounting and locating around the mandrel <NUM> and formed tubular main/central inner liner <NUM>. Selected sections of or the entire surface of the microporous membrane <NUM> on both sides may be treated (e. , etched using conventional techniques) to promote the application of a thin polymeric strike layer at selected sections or edges of the microporous membrane <NUM>, the microporous membrane forming an intrinsic weld with the catheter polymeric substrates along the polymeric strike layer. Like the microporous membrane, the formed tubular PTFE main/central inner liner <NUM> is also treated (e.g., etched) and is prepped with a polymeric strike layer. Referring to <FIG>, the cut microporous membrane <NUM> is positioned, preferably centered, over the punched exhaust vent <NUM> defined in the formed tubular PTFE main/central inner liner <NUM>. Thereafter, the formed tubular PTFE main/central inner liner <NUM> is attached (e.g., welded or bonded) together with the cut microporous membrane <NUM> under the application of heat during the laminating construction processing steps of the catheter.

As shown in <FIG>, using a wire braiding machine, a braid or a coil <NUM> is tightly applied or wound about the assembled SPC dipped mandrel <NUM> with the formed tubular ePTFE main/central liner <NUM> and ePTFE microporous membrane patch <NUM>. Braid <NUM> provides both structural support as well as retaining the ePTFE microporous membrane patch <NUM> to the tubular formed ePTFE main/central liner <NUM>. Thereafter, a polymer jacket material <NUM> with a skived port is located directly over the skive. In <FIG>, heat shrink tubing is positioned over the assembly, then heat is applied to get the materials to reflow and bond together, thereafter the heat shrink tubing is removed. Preferably, fluorinated ethylene propylene (FEP) heat shrink is slid over the assembly and heat is applied to cause reflow of the polymer jacket material <NUM> to bond to the braid, etch/strike portion of the membrane as well as to the strike layer covering the PTFE.

A separately formed inflation liner <NUM> (e.g., PTFE) is wrapped about its own internal mandrel (e.g., SPC mandrel) forms the inflation lumen <NUM>, as shown in <FIG>. The formed tubular inflation liner may be positioned above the braid, below the braid or between the braid strands (i.e., part of the braid is above the formed tubular inflation liner, while another part of the braid is below the formed tubular inflation liner). Alternatively, a preformed tube may be used as the formed tubular inflation liner. The formed tubular ePTFE inflation liner may be positioned longitudinally relative to the formed tubular main/central liner. In one configuration the formed tubular inflation liner and main/central liner are arranged such that the ePTFE microporous membrane <NUM> and the exhaust vent <NUM> to the balloon <NUM> are substantially radially aligned with the radial exhaust vent <NUM> (as shown in <FIG>). Alternatively, as illustrated in <FIG>, the microporous membrane <NUM> and inflation vent <NUM>, need not be radially aligned with the radial exhaust vent <NUM>. The assembled outer jackets, braid, inflation lumen and liner are fused together during reflow when subject to FEP heat shrink processing. Prior to attachment of the balloon the FEP heat shrink is removed. The balloon <NUM> in <FIG> is positioned over the fused assembly of the outer jackets, braid, inflation lumen and liner so that the balloon covers the inlet vent <NUM>. Then the balloon is heat welded at both ends to create an intrinsic weld with the outer surface of the catheter shaft or body <NUM>.

Referring to <FIG> several additional thermoplastic outer tubes, sleeves or jackets (<NUM>, <NUM>', <NUM>") with varying shore hardness may be positioned over the respective main/central liner <NUM>, braid <NUM>, and inflation liner <NUM> to tailor the finished catheters stiffness profile as desired. The jackets are placed one after another to vary the stiffness of the catheter along its length. Jackets of different hardness are arranged over the central lumen, braid and inflation lumen assembly, each jacket disposed longitudinally serially one butted up against (in physical contact with) the next jacket, or a space may be left for material to flow into between adjacent jackets. The longitudinally disposed singular outer jackets allow for a lower profile wall thickness which is a function of how low a wall thickness that can be extruded for a particular material. These jackets are reflowed through the braid pattern and bond with the strike layers of the central and inflation lumens. The reflow process includes threading a FEP heat shrink tube over the assembly, applying heat to reflow the jackets, and removing the FEP heat shrink afterwards. The balloon is then heat welded to the assembly. Radially disposed outer jackets are possible.

Once the components have been assembled and positioned as desired, an insert is preferably placed to prevent sealing of the opening during heating and thereby maintain fluid communication in the following areas: (i) at the end of the inflation lumen; (ii) between the balloon and the inflation lumen; (iii) as well as between the inflation lumen and the PTFE microporous membrane. Heat is applied whereby the thermoplastic materials reflow to form a secure assembly while the insert prohibits sealing of the communication channels. Lastly, the insert is removed and the balloon <NUM> is assembled (e.g., heat welded) to the secure assembly. In the configuration in <FIG>, a distal end of the balloon <NUM> is sealed within the wall of the catheter (i.e., between the PTFE central liner and the outer jacket). Thereafter, the balloon <NUM> is inverted and its proximal end is laser welded to the outer surface of the assembled catheter body. In an alternative configuration depicted in <FIG>, rather than wrap around the distal end or tip <NUM>, the balloon is laser welded to the outer surface of the catheter shaft at both its proximal and distal ends. A luer or other connector <NUM> may be attached to the proximal end of the assembled catheter.

The location of the inflation/exhaust vents encourages full venting of the residual air and only when the residual air has been fully bled, will the balloon inflate with the inflation medium initially used to bleed the catheter of residual air. To facilitate this, the inflation port size and exhaust vent size is preferably optimized so that the pressure required to inflate the balloon is greater than the pressure required to vent residual air.

In <FIG>, braid <NUM> is wound about the outer perimeter of the assembled formed tubular PTFE main/central liner and ePTFE microporous membrane secured thereto to retain the microporous membrane in position. The ePTFE microporous membrane may otherwise be positioned over the braid, that is, the braid wrapped about the outer perimeter of the formed tubular main/central liner entirely radially inward (i.e., under/beneath) of the formed tubular inflation liner. While in another design the braid may be wrapped about the outer perimeter of the assembled formed tubular PTFE main/central liner, ePTFE microporous membrane and formed tubular inflation liner. In still yet another configuration, one part of the braid may be wound radially inward (i.e., under/beneath) the formed tubular inflation liner (i.e., between the formed tubular inflation liner and the formed tubular main/central liner) and another part radially outward (i.e., over/above) the formed tubular inflation liner (as shown in <FIG>).

The present inventive balloon guide catheter with positive venting is prepped by a physician or interventionalist prior to introduction into the body. Specifically, a syringe <NUM> containing an inflation medium is connected to the inflation lumen <NUM> via the inflation port <NUM>. As the physician or interventionalist dispenses the inflation medium into the inflation lumen <NUM> using the syringe <NUM> the residual air therein is pushed by the inflation medium through the inflation lumen <NUM> in a distal direction. Since the residual air is positively pushed through the inflation lumen by the inflation medium the need for a vacuum or negative pressure to purge the residual air from the catheter is eliminated. In greater detail, initially, when the balloon is deflated and tightly wrapped in physical contact against the outer surface of the catheter body, the residual air follows the route or path of least resistance passing through the microporous membrane <NUM> and exiting from the catheter body through the exhaust openings <NUM>, <NUM>'. As the inflation medium is introduced into the inflation port, only the residual gas (e.g., air) permeates through the microporous membranes <NUM> and outward through the respective radially and longitudinally configured exhaust openings <NUM>, <NUM>'. Since the microporous membranes <NUM> prohibit the liquid inflation medium from permeating therethrough, initially due to the fact that the residual gas (e.g., air) previously trapped inside the catheter passes through the porous membranes and outward from the exhaust openings <NUM>, <NUM>' the pressure in the inflation lumen <NUM> remains somewhat equalized or constant. However, once the residual gas (e.g., air) in the catheter has been bled, continued dispensing of the pressurized inflation medium into the inflation lumen causes a build-up of pressure at the inflation opening <NUM> exerting a radially outward force on the balloon <NUM> causing it to expand radially outward as it fills with the inflation medium. <FIG> depicts balloon <NUM> while in a deflated state; whereas <FIG> depicts the balloon while in a fully inflated state, once the residual air has been purged from the catheter and the inflation medium has completely filled the balloon.

Only one inflation opening <NUM> is shown in <FIG>, but more than one inflation opening is contemplated and within the intended scope of the present invention for faster inflation/expansion of the balloon <NUM>. While in a deflated state (as seen in <FIG>), balloon <NUM> is in physical contact with the outer surface of the catheter body sealing the inflation opening <NUM> closed so that the flushing medium is unable to pass therethrough until the pressure exerted on the balloon at the inflation opening <NUM> exceeds a predetermined threshold.

An alternative configuration of the main/central lumen <NUM> and partially/semi-encircling inflation lumen <NUM> of the present inventive balloon guide catheter is shown in <FIG>, wherein the balloon is in an inflated state. Once again inflation medium is received in the proximal end <NUM> and purged or expelled from the distal end <NUM>. Balloon <NUM> is laser welded at its proximal end directly to the catheter shaft or body <NUM>, while at its opposite distal end of the balloon <NUM> distal pores <NUM> (e.g., a microporous membrane or a plurality of longitudinal openings) are disposed at the interface between the balloon and outer surface of the catheter body. Microporous membrane <NUM> is similar to that described in detail with respect to the previous embodiments and allows only the passage of a residual gas (e.g., residual air) therethrough, prohibiting passage of any liquid/solution (e.g., inflation medium). A bump, projection, protrusion or other raised surface <NUM> extends radially outward from the outer surface of the catheter body and is located proximally of the microporous membrane <NUM>. During prepping of the balloon guide catheter prior to insertion into the blood vessel, the device is positioned with the distal end pointing upwards. When inflation medium is injected through the inflation lumen, residual gas is directed over the bump <NUM> with a slight expansion in the balloon <NUM> and exits through the microporous membrane <NUM>. Once the air has escaped, the passage of inflation medium is blocked by the microporous membrane <NUM> and the balloon <NUM> fully inflates with increasing pressure. However, the physician or interventionalist need only partially inflate the balloon <NUM> until there is no residual gas visible within the balloon. Prior to insertion into the body, inflation medium is retracted back into the syringe under negative pressure/vacuum and the balloon <NUM> deflates. The balloon <NUM> while in a deflated state forms a seal against the bump, projection or protrusion <NUM> preventing the passage of gas in a proximal direction back into the balloon, thereby maintaining the lumen purged of air in a deflated state prior to insertion into the body.

In yet a further modification of the configuration of the balloon catheter in accordance with the present invention, the assembled catheter body at its distal end may be configured to have an expandable distal end or tip <NUM> as depicted in <FIG>. The expandable distal end or tip being in an expanded state having a larger diameter when the balloon is inflated, relative to the smaller diameter of the expandable distal end or tip of the catheter while in a compressed state when the balloon is deflated. Specifically, the expandable distal end or tip <NUM> is divided into a plurality of separable expandable fingers <NUM> radially compressible together by an over molded balloon <NUM>. In this particular configuration, rather than substantially conform to the outer contour of the expandable fingers, while in an inflated state the over molded balloon instead is pulled taught across and is in physical contact only with the tips or ends of the fingers (no physical contact of the balloon between the fingers). In the configuration shown in <FIG>, the balloon is only welded or secured about the outer perimeter of the catheter shaft distally of the porous membrane <NUM> coinciding with punch hole through main liner <NUM> and outer jacket <NUM>. Other methods of attachment are contemplated and within the intended scope of the present invention for securing the balloon around the expandable separable fingers such as adhesive bonding or thermal fusion, as described in detail further. The expandable distal end or tip <NUM> of the catheter may be divided into any number of two or more expandable separable fingers <NUM>, as desired. The more fingers <NUM>, the shorter the distance that the expandable material between adjacent separable fingers needs to spread apart from one another when the balloon of the catheter is inflated with the inflation medium. The less fingers <NUM>, the larger the diameter that the fingers will expand to. The space between fingers can be adjusted, as desired. That is, the space between adjacent fingers may be increased to allow for sufficient expandable material such that the force to expand the material is relatively low; the space between adjacent fingers may be reduced such that the expandable material reaches maximum expansion at a predetermined diameter. The fingers may optionally include features that aid in minimizing lateral bending forces to optimize flexibility when navigating through tortuous paths.

Prior to dispensing the inflation medium into the inflation lumen <NUM>, the balloon <NUM> is in a deflated state and the expandable distal end or tip <NUM> of the catheter is in a radially compressed state, as seen in <FIG>. While in this radially compressed state, adjacent fingers <NUM> have the smallest distance separation therebetween such that the outer diameter of the distal end or tip is less than or equal to the outer diameter of the remaining portion of the catheter. While the balloon <NUM> is in a deflated state it is pulled taught in physical contact against the bump <NUM> serving as a deflating seal to prohibit passage of residual gas (e.g., air) through the exhaust vent <NUM> in a proximal direction back into the balloon <NUM>.

Referring to <FIG>, during inflation, balloon <NUM> expands radially and contracts longitudinally thereby with it pulling the expandable distal tip <NUM> proximally and enlarging the distance separation between adjacent fingers <NUM>. With such enlarged distal end or tip a wider mouth is provided on the distal end of the catheter for aspiration and affording greater aspiration force when engaged with a clot. Once the clot is engaged, aspiration force may be maintained while the balloon is deflated and the distal mouth compresses the clot radially to assist in gripping the clot for extraction through a larger guide or balloon guide catheter. The balloon may vary in thickness, as desired, in defining the specific expansion profile of the balloon and expandable distal end or tip <NUM>.

<FIG> is a radial cross-sectional view of the four fingers of the catheter in <FIG> along lines IV(C) - IV(C), while the fingers are in a compressed state (reduced diameter) and the balloon is deflated. Another view, in <FIG>, depicts an end view of the expandable distal tip in <FIG> and, in particular, the four fingers of the expandable distal end or tip in an expanded state (enlarged diameter) with the balloon inflated.

A restrictive band <NUM> may be disposed about the balloon proximally of the expandable distal end or tip <NUM> (<FIG>) to restrict radially the diameter of the balloon when inflated, as shown in <FIG>. If a radiopaque material is selected for the restrictive band <NUM>, the band may serve the dual function of a marker during navigation of the catheter to a target site in a vessel. Balloon <NUM> is adhered or secured proximally to the outer surface of the catheter shaft, distally encapsulating the fingers <NUM> without being secured in any manner (uncoupled) beneath the restrictive band <NUM>. Accordingly, during inflation/deflation of the balloon <NUM> with inflation medium any sliding movement of the balloon <NUM> beneath the restrictive band <NUM> is unhindered and permitted. As the balloon <NUM> is inflated with inflation medium the pressure within the balloon increases (as denoted by the "IP" arrows) causing the balloon to enlarge in diameter, in turn, applying tension (as denoted by the "T" arrows) to the balloon material causing the fingers to open or separate thereby increasing in diameter the expandable distal tip. Preferably, the expandable distal tip or end <NUM> expands to an outer diameter greater than the outer diameter of the inflated balloon.

Yet another alternative configuration of the expandable distal tip or end of the catheter is illustrated in <FIG>. In this particular design a proximal end of the balloon is secured to the outer surface of the catheter shaft proximate while the opposite end of the balloon is distally secured (e.g., bonded or welded) between the fingers. Such distal weld pattern (as denoted by the dashed lines) advantageously seals the balloon and promotes expansion of the fingers during inflation, as shown in <FIG> as well as the distal end view in <FIG> of distal expandable tip in <FIG>.

A last configuration of the expandable distal end or tip of the catheter is depicted in <FIG>, wherein the fingers are replaced with an expandable cage, mesh or braid <NUM>' attached to a distal end of the catheter shaft. The proximal end of the balloon <NUM> is secured to the outer surface of the catheter shaft while its opposite distal end encapsulates the braid <NUM>' and is coupled distally to the distal end of the main shaft via the braid. By selecting a particular braid pattern and the desired degree of expandability of the expandable balloon material over the expandable distal tip, the braid <NUM>' is pulled open (i.e., increases in diameter) as the balloon inflates/expands with inflation medium. It is noted that no portion of the formed tubular PTFE main/central liner is present at (i.e., not extend distally into) that portion of the distal end or tip of the catheter which is intended to expand (e.g., fingers <NUM> or braid <NUM>') as this would restrict the distal end or tip from expansion, however, the distal terminating end of the formed tubular PTFE main/central liner may extend axially to and hence reinforce a location at which the expandable distal end or tip is hingedly connected to the distal end of the catheter shaft. Furthermore, the distal end of the balloon may be inverted at the distal tip of the catheter where it extends proximally to encapsulate the braid.

In each of the inventive embodiments described herein, since residual air is exhausted distally from the catheter, the present inventive balloon catheter is to be prepped by purging the device prior to being introduced into the body. Failure to purge the catheter prior to introduction into the body will result in the exhausted residual air undesirably entering the vascular system potentially causing harm to the patient. The positive venting system associated with the present inventive balloon guide catheters simplifies the prepping steps for purging residual air from the device thereby minimizing barriers to use of the device by physicians or interventionalists.

Claim 1:
A balloon guide catheter comprising:
a catheter shaft (<NUM>) having an outer surface, a proximal end, and an opposite distal end; the catheter shaft (<NUM>) having a main lumen (<NUM>) defined therein extending axially therethrough from the proximal end to the distal end; the main shaft being configured to receive a guidewire therein; the catheter shaft (<NUM>) having an inflation lumen (<NUM>) defined axially therein arranged semi-encircling the main lumen (<NUM>); the inflation lumen (<NUM>) having an inlet vent (<NUM>) defined radially outward from the catheter shaft and at least one exhaust vent (<NUM>, <NUM>') disposed proximate the distal end of the catheter shaft (<NUM>); and characterized by the at least one exhaust vent (<NUM>, <NUM>') being disposed longitudinally through a distal terminating end of the inflation lumen or radially inward in fluid communication with the main lumen (<NUM>);
a porous membrane (<NUM>) disposed at the at least one exhaust vent (<NUM>, <NUM>'); the porous membrane (<NUM>) having a plurality of holes defined therein sized to permit only gas to pass therethrough; and
an expandable balloon (<NUM>) secured about the outer surface of the catheter shaft (<NUM>) proximate the distal end of the catheter shaft (<NUM>) and coinciding with the inlet vent (<NUM>).