Patent Description:
The most common cause of a stroke is an obstruction of an artery in the brain caused by lodgment of a blood clot. The clot or embolus dislodges from a source such as the heart or an artery in the neck, and travels into a brain artery. As the artery narrows, the clot eventually becomes fixed or stuck in position. Flow ceases to the region of the brain beyond the obstruction and severe damage often occurs. The brain is very unforgiving of lost blood flow. Many regions are supplied by only one source of blood, and the function of the brain is not replicated. Once a motor or speech area is lost, there is limited ability for other segments of the brain to take over the lost function.

The typical treatment for stroke was conservative, watchful therapy. With this approach the outcome can often be unsatisfactory. Another form of therapy involves the use of clot dissolving agents. However, these agents can only provide limited benefit.

More recently, important advances have occurred in catheterized blood clot removal techniques. Now, if stroke patients are brought to a catheterization laboratory ("cath lab") promptly after the clot has lodged, the clot may be removed to more quickly restore blood flow. In such cases the survival and functional status of these patients can dramatically improve. Instead of most patients either dying or being transferred to nursing facilities, most patients survive and can live independently.

The tools currently developed and available to remove blood clots in the brain are still in their early development. An important aspect of treatment can be the use of constant suction pressure at a location proximal to the blood clot coupled with stent-like blood clot retrievers ("stent-trievers") that physically trap the clots and allow removal. There is still considerable room for improvement in these devices. In addition, a meaningful percentage of patients who enter the cath lab for clot removal have no restoration of blood flow. More effective systems, devices and methods are necessary to treat these people.

One of the key challenges relates to the small blood vessels containing the blood clots. These blood vessels may have internal diameters of about <NUM> or less. The vessels are often deep inside the brain and the path to reach them is tortuous. These realities create great challenges. But the reward for solving these problems is immense for those unfortunate enough to suffer a stroke.

Most strokes are treated with constant suction pressure proximal to the clot. The suction is provided by a catheter placed near or proximate the clot. If this is not sufficient, or if the interventionist prefers, a guidewire is passed adjacent to or through the clot and then distally beyond the clot. This guidewire is then used to guide the delivery of a stent-triever inside a small catheter. A stent-triever is deployed adjacent to the clot and is used to trap and physically remove the clot. The stent-triever may cause complications by breaking up the blood clot into pieces that travel distally or downstream into even smaller brain vessels. This causes obstruction of distal blood vessels and can cause more brain damage and disability for the patient. It would be useful to remove the blood clot while minimizing further risk of such additional harm to the patient.

The stent-triever involves an additional step. The guidewire must be introduced into the blood vessel proximate the blood clot. A stent-triever is then passed over the guidewire to the site of the clot. It would be advantageous to provide devices that simplify this procedure.

Adding too much suction to a blood vessel may cause the vessel to collapse, making it even harder to remove the clot. Therefore, a physician using current systems, devices and methods based on constant suction fluid pressure must balance the need for using sufficient pressure to dislodge the blood clot with the competing need to avoid blood vessel collapse. Unfortunately, many cases can involve a blood clot that is securely attached to and/or lodged against the interior wall surface of the blood vessel making removal with current techniques very difficult or impossible. Aggressive use of current techniques in an effort to remove strongly adhered or lodged clots can result in complications harmful to the patient.

For these and other reasons, it would be desirable to provide systems, devices and methods for more effectively treating stroke by removing blood clots during a catheter procedure.

<CIT> discloses embolectomy catheters, rapid exchange microcatheters, systems and methods for removing clots or other obstructive matter (e.g., thrombus, thromboemboli, embolic fragments of atherosclerotic plaque, foreign objects, etc.) from blood vessels. In some embodiments, the embolectomy catheters are advanceable with or over a guidewire which has been pre-inserted through or around the clot. Also, in some embodiments, the embolectomy catheters include clot removal devices which are deployable from the catheter after the catheter has been advanced at least partially through the clot. The clot removal device may include a deployable wire nest that is designed to prevent a blood clot from passing therethrough. The delivery catheter may include telescoping inner and outer tubes, with the clot removal device being radially constrained by the outer tube. Retraction of the outer tube removes the constraint on the clot removal device and permits it to expand to its deployed configuration.

No surgical methods form part of the invention.

In a first illustrative embodiment, a system is provided for removing a blood clot from a blood vessel of the patient. The system comprises a catheter having a distal end portion. A fluid pressure delivery apparatus is operative to apply suction fluid pressure intravascularly through the distal end portion of the catheter to a proximal side of the blood clot. A blood clot retrieval element captures the blood clot in the blood vessel. A control is operatively coupled with the fluid pressure delivery apparatus and/or the catheter to repeatedly cycle the suction fluid pressure in the blood vessel between different pressure levels for assisting with dislodgement and removal of the blood clot.

Optionally, the system may further comprise a radially expandable distal seal deployable from the distal end portion of the catheter. The radially expandable seal includes a proximal end portion and a distal end portion and is configured to expand radially in use and engage with the interior wall surface of the blood vessel. The seal is open at its proximal end portion. As another option, the distal radially expandable seal may self-adjust in size to accommodate blood vessels of differing diameter. For example, this self-adjustment may occur as the blood clot is pulled proximally during removal and the blood vessel enlarges. In that case, the expandable seal will also enlarge in size to maintain the seal. A fluid pressure delivery apparatus may then apply positive fluid pressure intravascularly into an area of the blood vessel contained by the radially expandable seal. A control is operatively coupled with the fluid pressure delivery apparatus to repeatedly cycle the positive fluid pressure in the blood vessel between different pressure levels distal to the blood clot for assisting with dislodgement and removal of the blood clot.

In another illustrative embodiment, a system is provided for removing a blood clot from a blood vessel of the patient and includes a catheter with a distal end portion, a radially expandable seal, a fluid pressure delivery apparatus, and a blood clot retrieval element. The radially expandable seal is deployable from the distal end portion of the catheter and is configured to expand radially in use and engage with the interior wall surface of the blood vessel. The fluid pressure delivery apparatus applies fluid pressure intravascularly through the catheter to an area of the blood vessel between the radially expandable seal and the blood clot. The blood clot retrieval element captures the blood clot in the blood vessel. In this embodiment, the seal may be deployed proximal or distal to the blood clot, and in various embodiments, two seals may be deployed with one being deployed proximal to the blood clot and the other being deployed distal to the blood clot. As another option, one or both radially expandable seals may self-adjust in size to accommodate blood vessels of differing diameter. For example, this self-adjustment may occur as the blood clot is pulled proximally during removal and the blood vessel enlarges such that the seals will also enlarge in size to maintain engagement with the interior wall surface of the vessel.

In another illustrative embodiment, a system for removing a blood clot from a blood vessel of the patient is provided and includes a catheter having a distal end portion, a radially expandable seal, a fluid pressure delivery apparatus, and a control. The radially expandable seal is deployable from the distal end portion of the catheter and includes a proximal end portion and a distal end portion. The radially expandable seal is configured to expand radially in use on a distal side of the blood clot, and engage with the interior wall surface of the blood vessel. The seal is open at its proximal end portion. The fluid pressure delivery apparatus applies positive fluid pressure intravascularly into an area of the blood vessel between the radially expandable seal and the blood clot. The control is operatively coupled with the fluid pressure delivery apparatus to repeatedly cycle the positive fluid pressure in the blood vessel between different pressure levels distal to the blood clot for assisting with dislodgement and removal of blood clot.

In another illustrative embodiment a system for removing a blood clot from a blood vessel of the patient is provided and includes a catheter, a fluid pressure delivery apparatus, a blood clot retrieval element, and a radially expandable and emboli capturing element. The catheter has a distal end portion. The fluid pressure delivery apparatus applies fluid suction pressure intravascularly through the distal end portion of the catheter to a location in the blood vessel proximal to the blood clot. The blood clot retrieval element captures a dislodged blood clot in the blood vessel. The radially expandable emboli capturing element is deployable from the distal end portion of the catheter and includes a proximal end portion and a distal end portion. The radially expandable emboli capturing element is configured to expand radially in use and engage with the interior wall surface of the blood vessel. The emboli capturing element is open at its proximal end portion such that the proximal end portion can radially expand on a distal side of the blood clot to capture emboli and prevent the emboli from traveling in a distal direction through the blood vessel. As another option, the radially expandable emboli capturing element may self-adjust in size to accommodate blood vessels of differing diameter. For example, this self-adjustment may occur as the blood clot is pulled proximally during removal and the blood vessel enlarges. In that case, the expandable emboli capturing element will also enlarge in size to prevent escape of emboli in a distal direction.

In another illustrative embodiment an intravascular device is provided for removing a blood clot from a blood vessel. The device comprises an elongate intravascular element sized and configured to be introduced into the blood vessel. The elongate intravascular element includes a distal end portion. A radially expandable seal is carried at the distal end portion of the elongate intravascular element. The radially expandable seal includes a proximal end portion and a distal end portion and is configured to expand radially in use such that at least the proximal end portion or the distal end portion of the seal forms a fluid pressure seal against the interior wall surface of the blood vessel. In various embodiments, the elongate intravascular element may further comprise a catheter, such as a small diameter catheter or what is sometimes referred to herein as a "microcatheter. " A guidewire may be used to guide the microcatheter into position proximate the blood clot. In other embodiments, the elongate intravascular element is a guidewire. As another option, the radially expandable seal may self-adjust in size to accommodate blood vessels of differing diameter. For example, this self-adjustment may occur as the blood clot is pulled proximally during removal and the blood vessel enlarges. In that case, the expandable seal will also enlarge in size to maintain the seal.

In some embodiments, various options are available depending on the clinical needs of the patient and/or the desired surgical techniques of the physician. As examples, the radially expandable seal may be open at its distal end portion and the distal end portion may be sized and configured to provide a fluid pressure seal against the interior wall surface of the vessel to allow suction to be applied to a proximal side of the blood clot. In other embodiments the radially expandable seal is open at its proximal end portion and the proximal end portion is sized and configured to provide a fluid pressure seal against the interior wall surface of the blood vessel to allow positive fluid pressure to be applied to a distal side of the blood clot. As will be appreciated from further description provided below, the physician may choose a system that applies either suction pressure or positive pressure, or both suction pressure and positive pressure, proximal and/or distal to the blood clot for assisting with dislodgement and removal of the blood clot. As will be further described herein, the suction and/or positive fluid pressure may be constant pressure, cycled or pulsed pressure, or a combination of both during the clot dislodgement and removal procedure.

The radially expandable seal may take many possible forms depending on the desired characteristics and surgical techniques. For example, the radially expandable seal may comprise an elongate tubular shape for covering openings to one or more side vessel branches of the blood vessel. The radially expandable seal may be further configured to radially retract to allow for delivery through a delivery catheter to the site of the blood clot and then retracted or collapsed into the delivery catheter for removal. At least one tether may couple the radially expandable seal to the elongate intravascular element. The radially expandable seal may comprise a proximal end portion of various configurations, for use at a location distal to the blood clot. For example, the proximal end portion may be oriented either perpendicular to or generally at an acute angle relative to the longitudinal axis of the elongate intravascular element upon expansion of the radially expandable seal. Various shapes, such as sigmoid or other curved or straight lines may define the proximal end portion. The radially expandable seal may be formed in discrete, lengthwise extending sections. The radially expandable seal may be configured to unroll in a direction extending along the longitudinal axis of the elongate intravascular element during deployment and radial expansion of the seal. The radially expandable seal may expand from a location on the elongate intravascular element in opposite directions to at least partially surround the blood clot generally between the blood clot and the interior wall surface of the blood vessel.

The radially expandable seal may be separable from the elongate intravascular element, especially when the elongate intravascular element is a standard catheter. This form of separable seal may be pushed to the distal end portion of the elongate intravascular element and secured in place at the distal end portion. In other embodiments, the radially expandable seal is fixed for delivery with the elongate intravascular element, such as by being formed integrally with the elongate intravascular element, e.g., a catheter.

The radially expandable seal may further include a reinforcing structure, such as a radially expandable stent structure. The radially expandable seal may self-expand in a radial direction as the radially expandable seal is directed out from a delivery catheter. As another option, the radially expandable seal may self-adjust in size to accommodate blood vessels of differing diameter. For example, this self-adjustment may be provided by adding a spring-bias or resilient feature to the seal, such as one or more super-elastic wire elements that will maintain and adjust the radial expansion such that the seal engages the interior wall surface of the vessel even as the vessel diameter changes. Depending on the needs of the application, the material forming the radially expandable seal may take many forms. In cases in which the radially expandable seal must provide a robust fluid pressure seal, the seal may be formed from a membrane material that is highly flexible but imperforate. In other applications where the fluid pressure seal need not be extremely robust, or when the seal is used as an emboli capturing element, a mesh or stent-like structure may be used to accomplish the objectives.

The systems and devices of the many embodiments may further include other optional components and/or features. For example, a guide may be positioned at the distal end portion of the elongate intravascular element. The guide may include at least one guiding portion to steer a second elongate intravascular element sideward toward a periphery of the blood clot. The device may further comprise an inflatable balloon element carrying the guide. The elongate intravascular element may include at least one fluid channel for communicating a fluid pressure change within the blood vessel proximal to and/or distal to the blood clot. The elongate intravascular element may further comprise a plurality of perforations in the distal end portion communicating with the at least one fluid channel. The perforations may be contained in an area of the radially expandable seal to expand the radially expandable seal upon direction of positive fluid pressure through the perforations. The device may further comprise a radially expandable blood clot retrieval element for engaging and retrieving the blood clot in a proximal direction within the blood vessel. The device may further comprise a plurality of expandable projections carried by the elongate intravascular element for engaging and assisting removal of the blood clot. The elongate intravascular element may further include a non-linear section for engaging generally between the blood clot and the interior wall surface of the blood vessel. The non-linear section may further comprise a generally sinusoidal or helical section. The device may further include a positive pressure tube for delivering positive fluid pressure proximate the blood clot to thereby assist with removal of the blood clot. An elongate blood clot dislodging element may be provided and configured to extend between the blood clot and the interior wall surface of the blood vessel for dislodging the blood clot from the interior wall surface. A guide may be provided and configured to direct the elongate blood clot dislodging element sideward generally toward a periphery of the blood clot.

In other aspects and illustrative embodiments methods of removing a blood clot from a blood vessel of the patient are provided. For example, in one general method suction fluid pressure is applied within the blood vessel on the proximal side of the blood clot. The suction fluid pressure is repeatedly cycled between different pressure levels proximal to the blood clot for assisting with dislodgement and removal of the blood clot using a pulling force. The blood clot is dislodged from an interior wall surface of the blood vessel, and the blood clot is removed from the blood vessel with a catheter.

Various secondary features and steps of the method may be provided. For example, the suction fluid pressure may be cycled at a frequency exceeding <NUM>. The amplitude or difference between the higher and lower pressures may, for example, be <NUM> Hg or more. Generally, fluid pressures may be used in accordance with any levels deemed not to be harmful to the patient. This may include fluid pressures above, at, or below the normal blood pressure range for the patient. The method may further comprise using a tool to assist with dislodging the blood clot from the interior wall surface of the blood vessel. The method may further comprise using a retrieval tool to remove the blood clot from the blood vessel. The suction fluid pressure may be repeatedly cycled in a pressure range below the normal blood pressure range of the patient. Removing the blood clot may further comprise directing the blood clot into and through the catheter. Alternatively, removing the blood clot may further comprise retaining the blood clot at the distal end portion of the catheter and then withdrawing the catheter from the blood vessel.

Another method in accordance with an illustrative embodiment comprises deploying a radially expandable seal in engagement with an interior wall surface of the blood vessel proximate the blood clot. Fluid pressure is then applied in an area of the blood vessel between the radially expandable seal and the blood clot to at least assist with this engaging the blood clot from the interior wall surface. The blood clot is then removed from the vessel with the catheter.

In secondary or optional steps of the method, any of the other features as discussed herein may be employed. For example, the steps of deploying the radially expandable seal and applying fluid pressure may respectively further comprise engaging the expanded seal on a proximal side of the blood clot, and applying suction fluid pressure. In another optional aspect, applying suction fluid pressure may further comprise applying constant fluid pressure and/or cycled or pulsed suction fluid pressure. When cycling the suction fluid pressure, the suction fluid pressure may be cycled in a range below the normal blood pressure of the patient. Alternatively, or additionally, the steps of deploying the radially expandable seal and applying fluid pressure may respectively further comprise engaging an expanded seal on a distal side of the blood clot, and applying positive fluid pressure. Again, this positive fluid pressure may be comprised of constant fluid pressure and/or cycled or pulsed fluid pressure. When cycling the positive fluid pressure, the cycled fluid pressure may be in a range above the normal blood pressure of the patient.

Another method in accordance with an illustrative embodiment involves deploying a radially expandable emboli capturing element in engagement with an interior wall surface of the blood vessel distal to the blood clot. This element may also be referred to as a "seal" even though it may not provide any fluid sealing function but, instead, seals the vessel distal to the blood clot against emboli migrating distally and causing further stroke. Suction fluid pressure is applied in an area of the blood vessel proximal to the blood clot to at least assist with disengaging the blood clot from the interior wall surface. The blood clot is then removed from the blood vessel with the catheter. In this embodiment, the radially expandable emboli capturing element is used to capture emboli that may travel in a distal direction during the method or procedure. Any of the secondary or other optional features or steps discussed above or in the detailed description to follow may be used in this method, as well as in any other disclosed methods.

Various other aspects, advantages, features, or combinations of features and/or steps will be appreciated from the detailed description of the illustrative embodiments to follow, taken in conjunction with the accompanying drawings.

The detailed description herein serves to describe non-limiting embodiments or examples involving various inventive concepts and uses reference numbers for ease of understanding these examples. Common reference numbers between the figures refer to common features and structure having the same or similar functions, as will be understood. While various figures will have common reference numbers referring to such common features and structure, for purposes of conciseness, later figure descriptions will not necessarily repeat a discussion of these features and structure.

<FIG> illustrate an obstruction or blood clot <NUM> in a blood vessel <NUM> having an interior wall surface 12a. The blood vessel <NUM> can comprise a proximal portion <NUM> and a distal portion <NUM>, and can contain the blood clot <NUM> in the vessel between the portions <NUM>, <NUM>. As used herein, the term "blood clot" means any obstruction or clot material impeding the flow of blood in the vessel <NUM> regardless of the material forming the obstruction. An illustrative embodiment or example of a clot removal system is shown and includes an elongate intravascular element in the form of a suction catheter <NUM>. The suction catheter <NUM> can comprise a distal end <NUM>, which in turn can comprise a mouth or seal <NUM>. The distal end <NUM> of the suction catheter <NUM> is circular. The mouth or seal <NUM> can be funnel-shaped and radially expandable by having a stent-like structure which can self-expand upon being directed out from a delivery catheter (not shown). During an operation to remove the blood clot <NUM>, a user inserts the distal end <NUM> of the suction catheter in its unexpanded form into the blood vessel <NUM> through the proximal portion <NUM>. The mouth or seal <NUM> can be expanded radially to contact the interior wall 12a of the blood vessel <NUM> and create a seal against fluid flow at the proximal side of the blood clot <NUM>. Next, a guidewire <NUM> can be passed through the length of the suction catheter <NUM> out of the mouth or seal <NUM> and directed distally beyond the clot <NUM> (<FIG>). The guidewire <NUM> can comprise a thin and radially expandable distal seal membrane <NUM> at its distal end portion 18a. The guidewire <NUM> can comprise a wire core that is made of a small hollow tube with one or more slots or slits (not shown) cut into at least the distal end portion 18a to allow the guidewire <NUM> to bend or flex easily. The hollow tube can also contain a solid core wire that fills the lumen or void of the tube. In some embodiments, the wire core can be solid but flexible, and wrapped around helically by thin, flexible wire. The guidewire <NUM> can comprise a U-shaped tip (not shown) that also has an internal wire with wraps of wire surrounding it. This prevents the distal tip 18a of the guidewire <NUM> from penetrating through the wall of the vessel <NUM>. In some embodiments, the hollow guidewire <NUM> is not filled with a solid core wire but, instead, is open to allow transmission of fluid, such as CO<NUM>, to create a change in pressure within the blood vessel <NUM>. In some embodiments, the outer surface of the guidewire <NUM> can be coated with a low friction material that helps in directing the wire and avoiding clotting.

As shown in <FIG>, a system can comprise a guidewire <NUM> connected to a pressure source <NUM>. The guidewire <NUM> can be passed through a mouth <NUM> of a suction catheter <NUM> and stopped on a distal side of a blood clot <NUM>. The mouth or seal <NUM> can be expanded to create a seal against a blood vessel wall at a proximal side of the blood clot <NUM>. The guidewire <NUM> can comprise a distal seal or membrane <NUM>, and perforations <NUM> of any desired number, shape and/or configuration at its distal end portion 18a. For example, the perforations <NUM> can be substituted by one or more slits or slots in the guidewire distal end portion 18a within the inflation or expansion area of the seal <NUM>. The perforations <NUM> are located proximal to the attachment point of the distal seal <NUM> to the guidewire <NUM> or other elongate intravascular element. The seal <NUM> can comprise many embodiments. In some embodiments, the distal seal or membrane can be expanded radially to create a seal at the distal side of the blood clot <NUM>. The proximal end of the seal can be open to the blood clot <NUM>.

A pressure source <NUM> can release CO<NUM> <NUM> out of the perforations <NUM> on guidewire to positively pressurize the distal seal or membrane <NUM> by pressure on the distal side of the clot <NUM>. Applying positive pressure instead of suction within a vessel <NUM> may avoid collapse of the vessel <NUM> and allow easier removal of blood clots <NUM>. Applying positive pressure within the vessel <NUM> distal to the clot <NUM> can radially expand the vessel <NUM>, free the clot <NUM> from its lodged location against the interior wall surface 12a of the vessel <NUM>, and force the clot <NUM> in a proximal direction back to the suction catheter <NUM> which can provide relative negative pressure at its own funnel-shaped distal end <NUM>.

One or more pressure sources and controls <NUM> are provided, such as schematically shown in <FIG> for providing and controlling the suction and/or positive fluid pressure provided as disclosed herein and/or providing other control and operational functions. Although the pressure source/control <NUM> is not illustrated in every embodiment, for conciseness, it will be appreciated that every embodiment of system disclosed herein preferably includes components for providing negative and/or positive pressure and one or more controls <NUM> associated with the source (e.g., one or more pumps), and/or associated with the elongate intravascular element (e.g., a catheter and/or guidewire) delivering the pressure. The control <NUM> may also provide other capabilities. Vessels that are ischemic may be prone to spasm. Positive fluid pressure may help to expand the vessel <NUM> and improve the chance of clot removal. Pressurizing the blood vessel <NUM> distal to the clot <NUM>, and suctioning or aspirating the blood clot <NUM> proximal to the clot <NUM> may be a successful combination of actions to remove a clot <NUM> - as a large pressure gradient can be produced.

As used herein, the term "fluid" means a liquid, a gas, or a combination of liquid and gas. Liquids may be any desired biocompatible liquid. Gas such as air, CO<NUM>, O<NUM>, an anesthetic gas or any other biocompatible gas can be used and may provide protection against brain injury. CO<NUM> is absorbed very rapidly inside the body and may be a very good gas to use for pressurization. CO<NUM> can be nontoxic and is often available in hospitals in tanks and/or in other gas supplies. It can also be generated locally by adding an acid to bicarbonate. Nitric oxide is a powerful vasodilator gas. It may be useful to pressurize and physically and chemically dilate blood vessels. Aerosolized drugs can also be delivered. These could be used to dilate the vessel <NUM> and protect the brain. Fluids with medications could also be directed into the vessel <NUM>, such as in the examples shown and/or otherwise described herein.

The distal guidewire membrane <NUM> seals anywhere along its length generally, but is open at its proximal end in this embodiment. The gas or other fluid such as delivered through perforations <NUM> may be continuous (constant) or pulsed (cycled) at one or more desired frequencies and amplitudes of pressure, such as controlled by the pressure source/control <NUM>. The fluid pressure may be directed slowly to avoid vessel over-distention and rupture. Slow pressurization can avoid these undesirable effects. The pressure will generally be equal at the opposite ends of the guidewire <NUM> so adding gas or fluid slowly should be safe. The fluid should distend or radially expand the vessel <NUM> at the location of the applied pressure, thereby assisting to free or at least loosen the clot <NUM> from the vessel wall surface 12a, and force the clot <NUM> in a proximal direction back to the suction catheter <NUM> which is providing relative negative pressure at its own funnel-shaped distal end <NUM>. One or both of the suction and positive fluid pressure levels and/or type (e.g., constant pressure and/or pulsed or cycled pressure) may be adjusted during the procedure as desired or deemed necessary by the physician or in accordance with an algorithm.

<FIG> illustrates removal of a blood clot <NUM> from a blood vessel <NUM> with a system comprising a stent-triever <NUM>. In some embodiments, the system can further comprise a pressure source <NUM> that provides a positive pressure in addition to a negative pressure or suction provided by the catheter <NUM>. In certain embodiments, the pressure source may not provide a positive pressure. The stent-triever <NUM> can comprise a guidewire <NUM> and a mesh <NUM> proximal to the distal end of the guidewire <NUM>. When deployed, the guidewire <NUM> can be passed through the catheter <NUM> to the distal side of the blood clot <NUM> and the mesh <NUM> can be located near the site of clot <NUM>. When the pressure source <NUM> applies suction through the catheter <NUM> to dislodge the blood clot <NUM>, the mesh <NUM> can physically trap the blood clot <NUM>, allowing for easier removal. In some embodiments, a positive pressure can be applied from a pressure source <NUM> through guidewire <NUM> to help in dislodging the blood clot <NUM>. The guidewire <NUM> can further comprise a seal <NUM>. The seal <NUM> can comprise many embodiments. In some embodiments, the seal can be proximally open-ended and flexible. The seal can be expanded to help protect against broken pieces of clot <NUM> or emboli traveling distally, such as into the brain of the patient.

Here, a balloon-shaped or more spherical radially expandable seal 20a is shown with an annular hole or aperture <NUM> at its proximal end. The balloon membrane 20a or seal may have one hole or multiple holes <NUM>, especially proximally. The end of the membrane 20a near the perforations <NUM> may expand first (for example, by being more compliant) and the other, more proximal portion with the hole <NUM> may expand at a later time or subsequently. The balloon-shaped membrane 20a can seal the blood vessel <NUM> where the contacts the vessel wall surface 12a (<FIG>). The membrane 20a can help to prevent broken pieces of blood clot <NUM> from traveling distally. Suction is applied through the catheter <NUM> to dislodge and remove the blood clot <NUM>. As a user removes guidewire <NUM> after the procedure, the membrane 20a may invert such that the membrane may or may not contact the interior wall 12a of blood vessel, allowing for easier removal of the guidewire <NUM> (<FIG>).

These figures illustrate that a distal seal or membrane 20b may be elongate or tubular so as to cover or overlap intersections or openings of side vessel branches 12b communicating with the main vessel <NUM> containing the clot <NUM>. This keeps the fluid <NUM> from leaking out through side branches 12b and causing the main vessel <NUM> lose positive pressure. Shape variations for the distal seal 20b or membrane, such as generally cylindrical or other shapes, may provide additional assistance. Also, different thicknesses of the membrane 20b and differences in the flexibility or compliance may assist to ensure that the membrane 20b inflates near the fluid source hole or holes <NUM> first, and before the remainder of the membrane 20b inflates or expands.

Here, the clot <NUM> is shown to be forced into the distal end of the suction catheter <NUM> for removal purposes. The membrane or seal 20b is allowed to depressurize and to invert for removal purposes. If the gas used for positive pressurization is CO<NUM>, it should absorb in a short period of time. When the clot <NUM> is removed, there is no longer a closed space around the membrane 20b and the gas or other fluid may escape. Imaging of the clot <NUM> is useful, with CO<NUM>, for example, on one side of the clot <NUM> and dye on the other, as CO<NUM> can be seen on X-ray as a lucent area. This may highlight the distal end of the clot <NUM>, and dye shows the proximal end.

Here, the inflating or expanding distal membrane 20c is shown as an elongate tube also acting as a piston against a distal end of the clot <NUM>. For example, a tubular membrane 20c that sequentially inflates in a direction toward the clot <NUM> (proximally) and pushes the clot <NUM> in a proximal direction toward the suction catheter <NUM> may be used. This is better illustrated and described below. The membrane or seal 20c may be fashioned to impact the clot <NUM> in a manner similar to a piston. The open, proximal end of the seal 20c is attached to the guidewire <NUM> by one or more tethers <NUM>.

As shown in this figure, the membrane 20c may not invert for removal purposes. Here, the tethers <NUM> allow the seal 20c to be pulled into the suction catheter <NUM> in a proximal direction. A noninverting membrane may be beneficial as it can continue to prevent migration of clot material downstream into the brain vessels even during removal.

Here, the proximal, open end <NUM> of a radially expandable distal seal 20d is oriented generally at an acute angle to the longitudinal axis of the elongate intravascular element e.g., guidewire <NUM>. In other words, the proximal, open end <NUM> is bevel shaped. The bevel shape may be a linear or straight cut end, or it may be of any curved or other shape. The radially expandable seal or tubular element 20d in this embodiment, is shown as attached to the elongate intravascular element guidewire <NUM> by a single tether <NUM>. Optionally, multiple tethers <NUM> may be used. In either case, the tether(s) <NUM> may be integrally formed with the membrane or seal 20d, or may be separate and then suitably attached to the seal 20d and to the elongate intravascular element or guidewire <NUM>, such as with adhesive. The elongate tubular seal 20d may be formed by cutting a tube to form an opening at the proximal end <NUM> of a desired shape. The tubular seal may comprise a suitable flexible frame, such as formed by super-elastic wire elements (e.g., see <FIG>). This would assist with support and self-adjusted expansion in a radial direction to accommodate different sized blood vessels <NUM>. The generally bevel-shaped proximal end <NUM> assists with automatically collapsing and withdrawing the seal/tube 20d into the catheter <NUM> at the end of the procedure.

In this embodiment, as generally mentioned with respect to <FIG>, the open proximal end <NUM> has a generally beveled shape, but the shape is curvilinear or sigmoid. The tether <NUM> is integrally formed from the seal/ 20e during manufacture to simplify the manufacturing process. In addition, a flexible frame is provided for the seal/tube structure 20e and includes a ring-shaped support element <NUM> affixed at the open, proximal end <NUM>. The ring-shaped structure <NUM> may be formed from a super-elastic wire, for example. When the ring-shaped wire <NUM> sits in a vessel <NUM> having the typical circular cross-sectional shape, it will be oriented obliquely where its diameter is greater than the internal diameter of the vessel <NUM>. However, as the vessel internal diameter increases, the wire <NUM> will re-orient itself to be less oblique and maintain engagement with the internal wall surface 12a of the vessel <NUM>. The reverse will occur as the vessel diameter decreases. This results in a self-adjusting size feature for the distal seal 20e.

Here, a double membrane 20f is shown and occludes the vessel <NUM> sequentially. For example, there may be a first, more spherical distal balloon section 20f1 and then a second, elongate tubular or generally cylindrical proximal section 20f2 that expands due to the introduction of fluid through perforations <NUM>. Other shapes may be used for a "piston effect" to remove the clot <NUM>.

These figures illustrate that the balloon or membrane seal <NUM> may unravel at its open proximal end so that it is used as a "piston. " The unravelling may be variable. The length of the clot <NUM> generally is unknown and, therefore, as the guidewire <NUM> passes distally beyond the clot <NUM> the unraveling balloon may expand to adjust the distance to the clot <NUM>.

<FIG> show another embodiment of the tubular, distal seal <NUM> that can be unfolded or unrolled in a proximal direction. The folded seal may be expanded in a proximal direction as the guidewire <NUM> passes distally beyond the clot <NUM>, so that one or more unravelling proximal end portions of the seal <NUM> can contact the blood clot <NUM>, forcing the clot <NUM> in a proximal direction to assist with dislodgement and/or removal.

Guidewire <NUM> may comprise a tip that bends into a J-shape. This is to avoid puncturing a vessel <NUM> as the distal end of the guidewire <NUM> is directed through the vessel <NUM> or vessel structures of the patient. However, the guidewire <NUM> must pass around the clot <NUM>. Sometimes, the physician cannot pass the wire distally beyond the clot <NUM> as blood flow forced the clot <NUM> farther and farther into a tapering vessel lumen. The vessel <NUM> may also go into spasm. Therefore, it would be useful to be able to stabilize and guide a guidewire <NUM> to allow it to be directed more accurately between the vessel wall surface 12a and the clot <NUM> when that clot <NUM> is tightly fitted into the vessel <NUM>. This embodiment provides a guide <NUM>, which may be either a mechanical device or a balloon-type structure, or a combination of both, at the distal end of the suction catheter <NUM> to help guide the wire past the clot <NUM>. The guidewire <NUM> and guide <NUM> can both be positioned within the catheter <NUM> with the guidewire <NUM> passing between the catheter and the guide <NUM> (<FIG>). The guide <NUM> includes a guide portion that may be a channel <NUM> for receiving and steering the guidewire <NUM> in a sideward direction toward a periphery of the clot <NUM>. The guide <NUM> further includes an inflatable portion <NUM> that is inflated for use as shown, and deflated for delivery and removal through catheter <NUM>. <FIG> respectively illustrate positive pressure pushing and negative pressure suctioning of the clot <NUM> into the distal end of the suction catheter <NUM>, and then subsequent removal of the clot <NUM> and distal seal <NUM> or membrane through the suction catheter <NUM>.

These views better illustrate the use of a guide <NUM>. The guide <NUM> may be passed through the suction catheter <NUM> in a deflated state, then inflated for use at the site of the clot <NUM>, and then deflated again and removed. The guide <NUM> may straighten the U-shaped or J-shaped distal end of the guidewire <NUM> and brings it directly adjacent the clot <NUM> so that the distal end of the guidewire <NUM> can find the space between the clot <NUM> and the interior wall surface 12a of the vessel <NUM>. The channel <NUM>, or other guide portion such as an indentation, may be used to help steer the guidewire past the clot <NUM>. This may be used when the guidewire <NUM> will not pass through the clot <NUM> or between the clot <NUM> and the vessel wall surface 12a, or it may be used in every case.

These figures illustrate the use of an alternative guide <NUM>', having a guide channel <NUM>' defined by rails or other structure, for receiving and steering an elongate intravascular element in the form of a distal guidewire <NUM>. The guide <NUM>' would be best removed before suction is applied by the catheter <NUM> as it may otherwise block the effects of the suction. The guide <NUM>' may be mechanically collapsible for suitable delivery and removal through the catheter. The guide <NUM>' may use the funnel-shaped seal <NUM> as a part of the channel <NUM>'.

The previous figures show an elongate intravascular element in the form of a guidewire <NUM> with a distal membrane added to provide a seal of various desirable but merely illustrative forms. The distal ends of the seal can be attached to the microcatheter <NUM> while the proximal ends are left unattached such that when the membrane is expanded, it can be partially open through the unattached ends. Guidewires are generally constructed with steel and it may be difficult to reliably make holes in the side of the guidewire <NUM> to deliver fluid. It may be more useful to construct one or more systems generally described above from a catheter in place of or in addition to a guidewire <NUM>.

A catheter is generally made from a polymeric material. This would better allow suitable fluid apertures to be formed in the wall of the catheter. The catheter also generally has a larger diameter than a guidewire <NUM>, but catheters are routinely directed alongside and past clots when stent-trievers <NUM> are delivered through the catheters.

<FIG> shows a microcatheter <NUM> with a radially expandable seal membrane 20b attached at its distal end portion. It will be appreciated that any other configuration of the seal 20b may be used instead. There are holes or apertures <NUM> in the microcatheter <NUM> under or within the area of the expanded membrane 20b to infuse fluid such as gas. <FIG> also shows that a small guidewire tip <NUM> extends beyond the distal end of the microcatheter <NUM> to help deliver the microcatheter <NUM> beyond the clot <NUM>. This may be a guidewire portion suitably affixed to the distal end of the microcatheter, or may be the tip portion of a more conventional guidewire extending the length of the microcatheter <NUM>. To avoid a "step up" at the junction of the guidewire tip with the catheter, there may need to be a filler placed at the junction such as a glue or polymer to smooth the transition. Also, the guidewire tip <NUM> and/or the microcatheter distal tip 26a could comprise tapers that are matched so there is a minimal transition. The microcatheter <NUM> is inserted and extends distally beyond the clot <NUM> as shown and described previously.

<FIG> shows that the microcatheter <NUM> has been passed distally beyond the clot <NUM>. Fluid is infused through side holes <NUM> to expand the membrane 20b and create a seal against the interior wall surface 12a of the vessel <NUM> so that positive pressure can be applied in a proximal direction to extract the clot <NUM>. The number of side holes <NUM> can be varied. Additional holes (not shown) can also be placed in the microcatheter <NUM> between the clot <NUM> and the vessel wall surface 12a to help liberate the clot <NUM> from a strong attachment to the vessel wall surface 12a. It may be useful to rotate the microcatheter <NUM> to help separate the clot <NUM> circumferentially so it is free for removal. To encourage the catheter <NUM> to encircle the clot <NUM> when it is turned, the catheter <NUM> could be made with a gentle spiral or turn or a bend along its length. Vibration applied to the catheter <NUM> may assist clot separation. Oscillation of the pressure and fluid infusion may help to separate the clot <NUM> from the vessel wall surface 12a. Positive pressure is applied distal to the clot <NUM> (such as gas infusion shown by arrows) and suction is applied through the suction catheter <NUM> (vacuum). The clot <NUM> can then be removed. As described previously, variations and oscillations (i.e., cycling or pulsing the pressure) in the pressure (positive pressure and/or suction) on each side of the clot <NUM> may be useful in removing the clot <NUM>.

This figure shows a device similar to the one shown in <FIG>. This microcatheter <NUM> has a guidewire <NUM> is passed through the length of the device. The guidewire <NUM> also serves to seal the distal end 26a of the catheter <NUM> so that positive pressure can be developed inside the catheter <NUM> to pressurize the seal membrane 20b. There is space <NUM> between the guidewire <NUM> and the inside of the catheter <NUM> to inject fluid such as gas to expand and pressurize the membrane 20b. The infused gas presses the radially expandable membrane 20b against the vessel wall surface 12a to create a seal and allow pressure to be generated to push the clot <NUM> proximally. In performing the procedure, the guidewire <NUM> first could be directed distally beyond the clot <NUM>. The catheter <NUM> could then be fed over the guidewire <NUM> distally beyond the clot <NUM>. Gas could then be infused as shown and described at the location distal to the clot <NUM>.

Construction of a system to remove clot <NUM> in which a guidewire type element or a catheter type element is part of the system could be difficult, expensive and perhaps unstable in some situations. As an option, the elongate intravascular element could be a standard microcatheter <NUM> and the lumen of the standard microcatheter <NUM> could be used as a flow channel to inflate or radially expand a distal seal or membrane <NUM> and positively pressurize the area between the <NUM> and the clot <NUM>. It may be less expensive and easier to attach a membrane <NUM> to a guidewire <NUM> and pass this beyond the clot <NUM>. This would be a relatively simple device to create. A relatively cylindrical seal or membrane <NUM> could be attached to a guidewire <NUM> near its distal tip and sealed to guidewire <NUM>. The guidewire <NUM> with the attached membrane <NUM> is contained and delivered from inside a microcatheter <NUM>, as shown in this figure. The guidewire <NUM> and microcatheter <NUM> are further contained and delivered from inside the suction catheter <NUM> and proximal to the clot <NUM>. It will be appreciated that any other suitable delivery component(s) and method may be used instead for inserting and operating the microcatheter <NUM>.

This figure shows the guidewire <NUM> (with attached seal or membrane <NUM>) inside the microcatheter <NUM>. These devices have been directed distally beyond the clot <NUM>. The membrane <NUM> is inside the microcatheter <NUM> during the delivery to make it easy to insert distally beyond the clot <NUM>.

The guidewire <NUM> with the attached seal or membrane <NUM> is pushed out of the microcatheter <NUM> at a location distal to the clot <NUM>. The membrane <NUM> is fashioned so that its open, proximal end is stiffer than its distal end and springs radially outward or open once outside of the microcatheter <NUM>. To encourage the proximal end of the membrane <NUM> to open, a tiny super-elastic spring element (not shown) could be attached to the proximal end of the membrane <NUM> to help it maintain the shape shown in the figure. Previous figures shown and described herein have shown tethers <NUM> that are used to close the membrane <NUM>, and these could be used in this embodiment as well. The tether(s) <NUM> could be stiff and made of fine wires that are pushed or otherwise moved to open the membrane <NUM>.

The microcatheter <NUM> is then pushed toward the end of the guidewire <NUM> under the membrane or seal <NUM> to further open the seal into engagement with the interior wall surface 12a of the vessel <NUM>.

Fluid, such as CO<NUM> gas or another fluid, is then injected through the microcatheter <NUM> and out the distal end thereof to more fully expand the membrane <NUM> in a radial direction to form a fluid seal between the membrane <NUM> and the interior wall surface 12a, and positively pressurize the area distal to the clot <NUM>. There is enough space between the wire <NUM> and the inside of the catheter <NUM> to inject gas or other fluid. The advantage of this alternative is that no side holes are needed in a catheter or guidewire. A guidewire 3can be made with an attached membrane or seal <NUM> as shown in the figures. The membrane <NUM> can be compressed and folded to deliver it from inside the microcatheter <NUM>.

In this figure an alternative way of deploying the membrane or seal <NUM> is shown. The system comprises a guidewire <NUM> with an attached membrane <NUM> which is folded or collapsed on top of the microcatheter <NUM>. The tip of the microcatheter <NUM> is advanced under the membrane <NUM> and close to the point of the attachment of the membrane <NUM> with the guidewire <NUM>. At this point, the membrane <NUM> is located radially outside the microcatheter <NUM>. The microcatheter <NUM> and the guidewire <NUM> are pushed distally beyond the clot <NUM>. In a typical situation, there is an abrupt diameter change where the guidewire <NUM> passes through the microcatheter <NUM> and this can make directing the catheter <NUM> more difficult. The membrane or seal <NUM> is located to smooth the passage of the microcatheter <NUM> by covering this transition. An advantage to this arrangement is that the microcatheter <NUM> does not have to be advanced inside the seal or membrane <NUM>. The membrane construction is more simple and the risk of the microcatheter <NUM> missing the inside of the membrane <NUM> to inflate the membrane <NUM> is eliminated.

This figure shows that gas or other fluid has been infused through the microcatheter <NUM>. The gas comes out the distal tip 26a of the microcatheter <NUM> which is deep inside the membrane <NUM>. This expands the membrane <NUM> and creates a distal seal <NUM>. Pressure on the system then encourages the clot <NUM> to exit the vessel <NUM>.

Once the membrane <NUM> is deployed by injecting CO<NUM> or other fluid, the microcatheter <NUM> may be moved toward the clot <NUM> and the tip of the microcatheter <NUM> may be brought back into the clot <NUM> - between the clot <NUM> and the vessel wall surface 12a. CO<NUM> or other fluid may be injected to help separate the clot <NUM> from the vessel wall surface 12a. As explained previously, the CO<NUM> could be pulsed with oscillations in pressure to help detach the clot <NUM> from the vessel wall surface 12a. As with all other embodiments, the pressure could instead be constant or nearly constant, or a combination of pulsed and constant pressure may be used during different portions of the procedure. Also, vibration could be applied to the wire <NUM> or the catheter <NUM> to rapidly move the clot <NUM> and the vessel wall surface 12a and help to free the clot <NUM>. The combination of fluid infusion, vibration and/or oscillation of pressure may be very useful.

As also discussed herein, positive pressure and suction can be provided proximal to the clot <NUM> through the suction catheter <NUM>. Pulsations in the vacuum and positive pressure may enhance the effectiveness of this clot removal system. The microcatheter <NUM> and/or the guidewire <NUM> could comprise one or more steps. In this case, when the catheter <NUM> is rotated it would tend to encircle the clot <NUM> to separate it from the vessel wall surface 12a.

The microcatheter <NUM> could comprise oscillations also with a slightly serpentine shape or with U-shaped turns. The configuration would be designed generally to deviate from the line of the central axis of the catheter <NUM>. For example, the deviations could alternate left and right or side-to-side similar to the teeth of a saw. The result would be to allow the microcatheter <NUM> to be rotated and/or otherwise moved relative to the clot <NUM> such that it helps separate the clot <NUM> from the vessel wall surface 12a by forcing the catheter <NUM> gradually between the clot <NUM> and the vessel wall surface 12a during rotation. An example is further discussed and shown herein.

The microcatheter <NUM> could also be moved back and forth over the clot <NUM> to help free or dislodge the clot <NUM>. Combining negative or suction pressure, positive pressure, oscillation or pulsing of suction and/or positive pressure and/or vibration may be used. Also, rotation of one or more components around the clot <NUM> may help for the guidewire <NUM> or the catheter to travel around the circumference of the clot <NUM> and help to remove it.

A control <NUM> (such as illustrated in <FIG>) may be provided for various purposes with respect to any and/or all embodiments. For example, the control <NUM> may provide for pressure level changes, frequency and amplitude variations in the pulsing or and oscillations of pressure, type of pressure (suction and/or positive pressure), provision of vibrations and/or other aspects directly relevant to clot removal techniques. In addition or alternatively, the control <NUM> could measure blood loss to ensure that the patient does not lose too much blood during the procedure, and/or a control <NUM> could measure pressure in the system in order to monitor status of the clot <NUM>. In this latter regard, zero pressure could indicate that the clot <NUM> is secured against the distal end of the suction catheter <NUM>, while continuous suction pressure of a certain level may indicate that the clot <NUM> is traveling proximally through the suction catheter <NUM> during removal. The vibration could be applied to any device near the clot <NUM> - the suction catheter <NUM>, the microcatheter <NUM> and/or the guidewire <NUM>.

CO<NUM> is absorbed rapidly. But it is possible that gas could remain under the membrane <NUM> where the gas does not contact tissue to absorb it. To remove the catheter system after clot removal, suction could be applied to the end of the microcatheter <NUM> to remove the gas under the membrane <NUM>. This will flatten the membrane <NUM> and make removal easier. Suction can be applied to the microcatheter <NUM> of any of the described variations to help collapse the membrane <NUM> and remove it.

These figures show side holes <NUM> in the microcatheter <NUM>. The microcatheter <NUM> could be withdrawn proximally such that the side holes <NUM> are at the location of the clot <NUM>. Or, the microcatheter <NUM> could be designed as shown in <FIG> such that proximal movement of the microcatheter <NUM> is not needed to align holes 35a with the clot location, e.g., between the clot <NUM> and the vessel wall surface 12a. This will allow for the infusion of gas or other fluid between the clot <NUM> and the vessel wall surface 12a.

As further shown in <FIG>, inflatable blades or fins <NUM> could be manufactured on the sides of the microcatheter <NUM>. They could be inflated by additional side holes in the microcatheter <NUM> located under the fins or blades <NUM>. These fins or blades could be made from small membranes that sit flat against the catheter <NUM> for insertion. The holes 35a could communicate with the holes <NUM> in the microcatheter <NUM> distally beyond the clot <NUM>. When the distal holes <NUM> pressurize the area distally beyond the clot <NUM>, the fins or blades <NUM> will begin to expand. The fins or blades <NUM> may be approximately <NUM> to <NUM> in size. The fins or blades <NUM> could be arranged like cleats on a shoe around the catheter <NUM>. They could also form a structure such as a screw or helix that helps to engage the clot <NUM> and so the clot <NUM> can be pulled out proximally when the catheter <NUM> is pulled back. The fins or blades <NUM> could also be filled by a separate channel (not shown) so that they are not dependent or related to the use of holes <NUM> distally beyond the clot <NUM>. The projections, such as fins or blades <NUM>, may comprise any useful shape and the microcatheter <NUM> could help to trap clot <NUM>. The projections <NUM> may also help to separate the clot <NUM> from the vessel wall surface 12a.

This figure shows a proximal seal membrane <NUM> that is delivered on the microcatheter <NUM>. The microcatheter <NUM> sits inside the suction catheter <NUM>. A wire <NUM> with a membrane <NUM> to seal distally has been passed beyond the clot <NUM>. The membrane seal <NUM> may be expanded by a super-elastic frame that opens the seal. The membrane seal <NUM> could be expanded by positive pressure - by injecting fluid through the microcatheter <NUM>. For delivery, the membrane <NUM> or seal could be inverted inside the microcatheter <NUM> and pushed out of the microcatheter <NUM> with a guidewire or stylet (not shown).

As shown in this figure, the proximal seal or membrane <NUM> has created a seal against the interior wall surface 12a of the vessel <NUM>, such as previously shown and described.

As further shown in this figure, the distal seal <NUM> or membrane, as shown previously, is folded upon itself. As gas or other fluid is directed from inside the wire <NUM>, the membrane <NUM> expands and begins to unroll. The membrane <NUM> eventually contacts the clot <NUM> and pushes the clot <NUM> in a proximal direction toward the suction catheter <NUM>.

As shown, the clot <NUM> has been pushed into the receiving end of the proximal membrane <NUM>. The proximal membrane <NUM> wraps around the clot <NUM> and helps to keep the clot <NUM> intact as it is pulled into the suction or vacuum catheter <NUM>. This reduces the risk of clot break up and embolization of particles more distally in the brain. It could also be useful to have a longer proximal membrane <NUM>. A clot <NUM> is often at least <NUM> in length. A membrane <NUM> that could fully contain the clot <NUM> and then sealed at the end by the unfolded distal seal membrane <NUM> would be completely contained and safe from embolization during removal.

As shown in this figure, the proximal seal <NUM> is attached to the suction catheter <NUM>. It will be appreciated that the proximal seal or membrane <NUM> can take on many different shapes and sizes. For example, the proximal seal <NUM> could be longer than shown, and may be inverted inside the suction catheter <NUM> for delivery, and then pushed out for sealing. This figure also shows a clot <NUM> and a wire <NUM> carrying a distal membrane seal <NUM> before its deployment, e.g., rolled up or otherwise collapsed.

The proximal membrane seal <NUM> has been activated. Only a small amount of pressure may be needed to radially expand or unfurl this seal <NUM>.

A microcatheter <NUM> has been advanced along the wire with the folded membrane <NUM>. CO<NUM> or other fluid may be used for inflation and the membrane <NUM> is expanded as shown.

As in the prior series <NUM> figures, the distal membrane <NUM> pushes the clot <NUM> into the proximal membrane <NUM> or at least toward the proximal membrane <NUM>. Alternatively, the combined proximal suction force and distal pushing force can result in proximal movement of the clot <NUM>. The clot <NUM> can then be removed.

There can also be positive pressure applied distal to the clot <NUM>, i.e., in a proximal direction to help push the clot <NUM> in the proximal direction. The combination of positive pressure distal to the clot <NUM> and suction proximal to the clot <NUM> can also be very useful in clot extraction.

The suction and/or positive pressure can be altered, such as by being cycled or pulsed. The change in suction could be gentle or abrupt. It could be used in a repeated cycle or a variable cycle or any variation in suction and/or positive pressure that helps to dislodge clot <NUM>. The suction and/or positive pressure may be applied in any pressure pattern. The positive pressure and suction can be adjusted simultaneously or as desired (cycles or pulses, pressure level or other variables) to produce the best arrangement to remove clot <NUM>.

It can also be helpful to apply positive pressure both proximal and distal to the clot <NUM>. This could help expand the vessel <NUM> and separate the clot <NUM> from the wall surface 12a of the vessel <NUM>. Clot <NUM> inside a vessel <NUM> tends to become adherent to the vessel wall surface 12a. By stretching the vessel <NUM> with positive pressure, the vessel <NUM> can expand and at least part or even all of the clot <NUM> can be separated from the vessel wall surface 12a.

A device that is advanced down an existing or more conventional suction catheter that has a radially expandable seal such as the funnel-shaped distal end <NUM> shown, and helps to apply a seal at the end of the suction catheter <NUM> is advantageous. The funnel-shaped seal <NUM> could be made from shape memory or super-elastic material that collapses for insertion and opens for sealing. The shape memory or super-elastic material, such as NITINOL, may comprise a sealing membrane or cover material to produce a complete seal. The sealing material could be a plastic, such as ePTFE. A separate device like this would allow interventional radiologists and neurologists to use their existing suction catheters and then add the seal separately after the suction catheter <NUM> has been brought into place.

This figure shows the microcatheter <NUM> with a non-linear section <NUM> which, in this illustrative embodiment, is spiral or helical shaped. Rotation of the microcatheter <NUM>, such as while the microcatheter <NUM> is directed distally past the clot <NUM>, can help disengage the clot <NUM> from the interior wall surface 12a of the vessel <NUM>, making removal of the clot <NUM> easier.

Previous figures in the above-incorporated applications have shown inflatable or otherwise radially expandable membranes or seals <NUM> through <NUM> that provide a seal for positive pressurization at a location distal or beyond the clot <NUM> in a vessel <NUM>. The distal membrane or seal can be delivered on an elongate intravascular element, such as a guidewire type structure or a catheter type structure.

As the distal membrane or seal is pressurized, one risk is that the fluid escapes distally and the seal fails to sufficiently form. A number of options to avoid this are described herein, such as double membranes, shaped membranes with a small proximal opening, etc..

Another option shown in this series of figures is to use the clot <NUM> to close the open proximal end of a distal membrane or seal 20i. Here, the membrane 20i is advanced so that the proximal (open) end of the membrane 20i is trapped between the interior vessel wall surface 12a and the clot <NUM>. This closes the proximal end of the membrane 20i so that when it is inflated by fluid, the membrane 20i is guaranteed to expand and form a seal.

<FIG> also show a suction catheter <NUM> with an attached or integrated funnel-shaped seal <NUM> to create a seal with the vessel <NUM> and improve the suction to remove the clot <NUM>. Another manner of creating this proximal seal <NUM> would be to use a conventional off-the-shelf cylindrical suction catheter, and then add the funnel-shaped seal <NUM> during the surgical intervention. This option is described more fully below. The proximal seal <NUM> could be attached to a long wire to advance it down the suction catheter <NUM>. The seal <NUM> could be made with an expandable frame of NITINOL or other shape memory material. A membrane cover could be added to enhance the seal. The shape memory mesh itself may be adequate to seal if the mesh is dense, but the addition of a solid or fluid impervious covering may create a more robust fluid pressure seal. A distal seal membrane 20i, as shown, is collapsed against the microcatheter <NUM> so that it can be delivered distally beyond the clot <NUM> in a vessel <NUM> of the patient.

This figure shows fluid being infused inside the membrane 20i. The fluid fills the membrane 20i distal to the clot <NUM> and expands the membrane 20i against the vessel wall surface 12a - producing a seal and ensuring that the membrane 20i is fully expanded and fluid does not escape distally to any significant extent.

Once the membrane seal 20i is filled distal to the clot <NUM>, additional fluid is introduced. The membrane 20i begins to wrap around the clot <NUM>. This is important because the movement of the membrane 20i around the clot <NUM> will help to separate the clot <NUM> from the vessel wall surface 12a. As explained previously, separating clot <NUM> from the vessel wall surface 12a is very important as it frees any attachments between the clot <NUM> and the vessel wall surface 12a to facilitate clot removal. This improves the chance that the clot <NUM> can be extracted. The arrow in the figure shows the course the membrane 20i will take enveloping the clot <NUM>.

The membrane 20i has occluded the vessel <NUM> distal to the clot <NUM>. The membrane 20i is shown wrapping around the clot <NUM> and separating the clot <NUM> from the wall surface 12a at least part of the way around the vessel <NUM>. The membrane 20i is shown open at the proximal end. The membrane 20i could actually be closed (as indicated in the figure) or partially closed at the proximal end to help ensure that it wraps around the clot <NUM> to the fullest extent possible before fluid begins to escape proximally.

It may also be useful to fully expand the membrane 20i and keep infusing fluid. The infused fluid can help to separate the clot <NUM> not contacted by the membrane 20i. As explained previously positive pressure may be applied proximal to the clot <NUM> from the suction catheter <NUM> or otherwise to radially expand the vessel <NUM> and help separate clot <NUM> from the vessel wall surface 12a. The membrane 20i that wraps around the clot <NUM> could be wide enough to fully wrap around the clot <NUM>. Also, pulsing/varying/cycling positive pressure and/or suction on each side of the clot <NUM> may also be useful in extracting clot <NUM>.

Another way to ensure the membrane 20i fills and occludes the distal portion of the vessel <NUM> would be to deliver the membrane 20i out of a microcatheter <NUM> so that it is only partly deployed (for example, half-way deployed). This would trap fluid and inflate the membrane 20i. After the membrane 20i is expanded, the rest of the membrane 20i could be extruded out of the microcatheter <NUM>. The microcatheter <NUM> could be slowly withdrawn allowing the membrane 20i to sequentially wrap around the clot <NUM> as the microcatheter <NUM> is withdrawn. In other words, an initial amount of fluid is introduced and this fluid fills or expands the membrane 20i at the distal end of the device. The catheter <NUM> is then withdrawn a few millimeters and an additional amount of fluid is introduced into the area contained by the membrane 20i. The membrane 20i wraps around more clot. The process is repeated until all the clot <NUM> is separated from the vessel wall surface 12a.

This figure is a cross-sectional view showing initial insertion of the microcatheter <NUM> alongside the clot <NUM> and initial deployment of the annular seal membrane 20i.

This figure is a cross-sectional view of the membrane 20i wrapping around the clot <NUM> during further deployment as compared to <FIG>. The membrane 20i is inflated and sequentially extends around the clot <NUM> as more fluid is introduced. The shape of the membrane 20i can be sized so that the membrane 20i even fully envelops and wraps around the clot <NUM>. This would separate the clot <NUM> circumferentially from the vessel wall surface 12a. It would also result in the clot <NUM> being fully enveloped by the membrane 20i. This could allow the clot <NUM> to be removed inside a "cocoon" like membrane enclosure that prevents the clot <NUM> fragmenting as it is kept in one piece for removal. The dotted lines show a variation of the membrane 20i that could fully wrap around the clot <NUM>.

This membrane 20i is shown attached to a microcatheter <NUM>. A guidewire type structure or other type of elongate intravascular element could instead be used to attach a membrane 20i to produce a similar device. The arrows in <FIG> and <FIG> show suction being applied from the suction catheter <NUM> to remove the clot <NUM> once it has been freed partly or completely from the vessel wall surface 12a. Again, the funnel-shaped seal <NUM> proximate a distal end of the suction catheter <NUM> may be integral or otherwise affixed for delivery with the suction catheter <NUM>, or it may be delivered as a separate component in which case the suction catheter <NUM> itself may be of a conventional type.

This shows the general shape of the membrane seal 20i. The distal end <NUM> is tapered. It can comprise a more pointed tip, a rounded tip or any useful shape such as a bullet type shape. At a proximal portion <NUM>, the membrane 20i is more of a cylinder shape. Proximally, the membrane 20i might be useful to have a wider cylinder to wrap around more clot <NUM>.

These figures show a device similar to the previous arrangement. Here, a membrane 20j wraps around the clot <NUM> but the membrane 20j is closed at its ends. The membrane 20j that wraps around the clot <NUM> is coupled to or otherwise carried on a microcatheter <NUM>, a guidewire <NUM> or other form of elongate intravascular element. In this regard, with respect to all embodiments the form of elongate intravascular element may take on many variations. There are openings <NUM> in the guidewire or catheter that communicate with the space inside the membrane 20j, so that fluid can be introduced down the catheter or guidewire to expand the membrane 20j.

In <FIG>, the membrane 20j has been expanded and it has wrapped around and enveloped the clot <NUM>. The clot <NUM> is shown inside the membrane 20j in dashed lines. The ends of the membrane 20j are shown open. It would also be possible to have the inflated membrane 20j closed at one or both ends of the clot <NUM> to prevent any part of the clot <NUM> from escaping.

This figure shows a transverse cross section of the membrane seal 20j wrapping around the clot <NUM>.

In this variation of <FIG>, the membrane 20j has "welds" or attachments <NUM> that keep the membrane 20j in a flat shape as it expands. This will help to make sure the membrane 20j wraps around the clot <NUM> circumferentially. These attachments <NUM> could be point attachments or lines or circles or any useful shape to achieve this result. The figure shows the "weld points" <NUM> in dashed lines.

This shows a side view of a microcatheter <NUM> or guidewire <NUM> that is in a form allowing it to be inserted inside a patient. An inflatable membrane <NUM> has a connection to a lumen that allows the membrane <NUM> to be expanded once inside a patient's blood vessel (not shown).

This figure shows the membrane <NUM> expanded. The membrane <NUM> forms a closed space that can retain introduced fluid. The membrane <NUM> communicates with the microcatheter lumen for filling with the fluid. The figure shows weld points <NUM> of various shapes that keep the membrane <NUM> from expanding to a more spherical shape. In general this membrane <NUM> expands in a plane that can be used to separate the clot <NUM> from the vessel wall surface 12a (see other figures herein).

The weld shapes can vary to help maintain the shape of the inflated membrane <NUM>. It may also be useful for the membrane <NUM> to inflate into a cylindrical shape so that it generally inflates following the interior wall surface 12a of the vessel <NUM> and holds the clot <NUM> inside. This could be accomplished by making one side of the membrane <NUM> shorter than the other, or by adjusting the welds to guide the inflated structure into a cylindrical or other tubular shape. Once the clot <NUM> is contained inside the membrane <NUM> it will help prevent emboli from traveling distally and causing stroke or damage downstream in the brain. In this regard, the membrane <NUM> acts as a radially expandable seal.

This figure shows a cross section view of the expanded membrane <NUM>. Weld points <NUM> serve to control the expanded shape of the membrane <NUM>, i.e., a generally cylindrical shape for enveloping the clot <NUM>.

This figure again shows a clot extraction device or membrane <NUM> that is in a collapsed state ideal for insertion inside a patient. An elongate intravascular element, such as a guidewire or a microcatheter <NUM>, provides a channel to fill the membrane <NUM> with fluid. The elongate intravascular element, e.g., guidewire <NUM>, communicates with one or more interior voids or spaces in the membrane <NUM> for inflating the initially closed or collapsed membrane <NUM>.

The prior <FIG> show a membrane <NUM> designed to wrap around clot <NUM>. It may be difficult to collapse this extensive membrane <NUM> for insertion, as there is a large amount of membrane <NUM> to collapse. <FIG> shows a membrane <NUM> with numerous sealed cut outs separated by fluidly connected series of link elements <NUM> inflated from the central lumen of the guidewire or microcatheter <NUM>. The inflatable link elements <NUM> may be shaped in three dimensions to form a tube or cylinder to wrap around the clot <NUM>. The shape of pentagons and hexagons is shown here, but any shape of this type of lattice structure may be used. An advantage of the open lattice is reduced material to allow crimping for delivery.

It should be noted that this same shape of device could be constructed without needing a fluid inflation. The lattice could be constructed from a collapsible material such as NITINOL or other super-elastic material. The lattice could be crimped inside a catheter for delivery, and may self-expand into this shape once released from the catheter.

This figure shows the device inside a vessel <NUM>, inflated and wrapping around a clot <NUM>. The device is mounted on a combined guidewire and microcatheter <NUM>. An attachment at the distal tip 26a of the catheter <NUM> to the guidewire <NUM> produces a seal that prevents leakage of the introduced fluid at the tip.

The microcatheter <NUM> is hollow and allows fluid to fill the membrane <NUM> that wraps around the clot <NUM>. The membrane <NUM> is fluidly coupled to the lumen of the microcatheter <NUM> in a manner that allows fluid to fill, i.e., expand the membrane <NUM> generally as described herein.

The membrane <NUM> that wraps around the clot <NUM> could form an enclosure at either or both of the proximal or distal ends. This would further help keep pieces of the clot <NUM> from escaping.

The figure also shows an arrow showing the microcatheter <NUM> being withdrawn to remove the clot <NUM> inside the enclosed inflated membrane structure.

There is a suction catheter <NUM> with a funnel-shaped proximal seal <NUM> or mouth. The assembly <NUM>, <NUM>, <NUM> can be pulled through the suction catheter <NUM> if desired. The arrow shows the direction of travel of the microcatheter <NUM> to remove the clot <NUM> inside the lattice structure. Alternatively, as with all other embodiments, the clot <NUM> may affix itself to the distal tip or end of the suction catheter <NUM> and the suction catheter <NUM> may then be withdrawn with the attached clot <NUM>.

This figure shows another way to remove clot <NUM> from a vessel <NUM>. A suction catheter <NUM> with a funnel mouth <NUM> is shown proximal to the clot <NUM>, and constructed such as in any of the manners described herein. The clot <NUM> is impacted in the vessel <NUM>. A microcatheter tip 26a has been passed distally beyond the clot <NUM>. This microcatheter <NUM> has a guidewire tip <NUM>. The microcatheter <NUM> has a hollow lumen to fill a clot extraction or removal device <NUM> with fluid. It should be noted that the device core or spine could be constructed from a guidewire entirely, or from a microcatheter without a tip of guidewire. Inflatable structures are shown and may comprise an annular inflatable membrane <NUM>. The membrane <NUM> may entrap and/or surround the clot <NUM>.

This figure shows the annular inflatable membrane <NUM> expanded. When expanded, the membrane <NUM> forms "fingers" <NUM> that wrap around the clot <NUM> and contain it. The fingers <NUM> expand toward the clot <NUM> and then wrap around as shown to contain the clot <NUM>. Alternatively (not shown in the figure), the fingers <NUM> could be inserted and fully expanded along the length of the microcatheter spine or core, so as to then wrap around the clot <NUM> as they are inflated. Proximal and distal membrane portions <NUM>, <NUM> could be continuous (i.e., joined proximal and distal finger segments). When inflated, the fingers <NUM> would completely cover and trap the clot <NUM> for sealing purposes. The figure shows an arrow indicating that the clot <NUM> is being pulled out.

This figure shows a variation on the inflatable finger structure shown in the prior figures. A clot <NUM> is inside a vessel <NUM> and a funnel-shaped seal <NUM> and suction catheter <NUM> are proximal to the clot <NUM> as previously described. A core or spine is shown composed of a hollow and fillable microcatheter <NUM> with a guidewire tip <NUM>. Fine rods <NUM>, composed of polymer gas fillable tubes or most likely composed of wire or also polymers like suture material (such as polypropylene), extend between inflatable bulbous ends <NUM>, <NUM>. At their ends, the rods <NUM> engage with or attach to the inflatable bulbous ends <NUM>, <NUM>. To help splay open the rods <NUM>, the rods <NUM> may wrap over the distal end of the inflatable bulbous ends <NUM>, <NUM>. The rods <NUM> are collapsed against the spine provided by the catheter <NUM>.

The inflatable ends <NUM>, <NUM> are expanded. The rods <NUM> sweep around the interior perimeter of the vessel <NUM> and scrape the clot <NUM> from the vessel wall surface 12a. The inflatable ends <NUM>, <NUM> may also expand the vessel wall to help the rods <NUM> wrap around the clot <NUM>. The rods <NUM> are shown surrounding the clot <NUM> and trapping the clot <NUM> inside for extraction. The rods <NUM> have been moved into position by the inflation of the inflatable bulbous ends <NUM>, <NUM>. The inflation carries the rods <NUM> around the clot <NUM>. The clot <NUM> can be extracted in or attached to the distal end of the suction catheter <NUM>.

This cross-sectional view shows one of the inflatable bulbous ends <NUM> with a microcatheter <NUM> attached. The rods <NUM> are shown in a radially expanded position to surround the clot <NUM>. The rods <NUM> may be located or wrapped over the ends <NUM>, <NUM>.

This variation of a membrane 20o shows inflatable bulbous ends <NUM>, <NUM> that do not wrap around the microcatheter <NUM>. The inflatable bulbous ends <NUM>, <NUM> move wires or rods <NUM> which can be inflatable or just composed of metal wire or polymer wire to wrap around the clot <NUM>. There is a fluid connection between the catheter <NUM> and the bulbous ends <NUM>, <NUM> to allow them to be filled with fluid and expanded in the positions shown to seal the vessel <NUM> on opposite proximal and distal ends of the clot <NUM>.

Rods that wrap around clot <NUM> can be activated by means other than fluid inflation. In these figures, a clot extraction device is shown as including rods <NUM> that a wrap around a clot <NUM> are carried inside a microcatheter <NUM> with a guidewire tip <NUM>. The rods <NUM> are attached at each end to a collapsible stent <NUM>, <NUM> (with one stent at each end of the rods). The proximal and distal stents <NUM>, <NUM> are collapsed inside the microcatheter <NUM> for insertion. The microcatheter <NUM> can be withdrawn allowing the stents <NUM>, <NUM> to self-expand. In this regard, any of the stents or stent-like structures described herein may be of the self-expanding type. The stents <NUM>, <NUM> and their attachment to the rods <NUM> expand and wrap the rods <NUM> around the clot <NUM>. The stents <NUM>, <NUM> could be made of shape memory material like NITINOL, or any other super-elastic material that automatically expand to the desired shape when released from a catheter.

This separates the clot <NUM> from the vessel wall surface 12a, and then the rods <NUM> trap the clot <NUM> inside. The open stents <NUM>, <NUM> can also help with clot extraction. They can comprise tapered ends to allow the stent to be pulled back to remove the clot <NUM> easily. The stents <NUM>, <NUM> could be shaped differently. Any stent variation that moves the rods <NUM> around the stent would be satisfactory. The microcatheter <NUM> could be removed once the stent is deployed. Then the stent/rod device could be pulled to remove the clot <NUM>. Not shown in the figures is a pull wire to withdraw the trapped clot <NUM>. Ideally, the proximal end of the proximal stent <NUM> has a wire (not shown) attached to its end and this wire would pass through the suction catheter <NUM> so that the interventionist could pull on the wire and retrieve the clot <NUM>.

It would be helpful for the stents <NUM>, <NUM> at opposite ends of the clot <NUM> to expand following the inner lumen of the vessel <NUM> and along a curved wall of the vessel <NUM>. Since these stents <NUM>, <NUM> carry the rods <NUM>, this will ensure the clot <NUM> is separated by the rods <NUM> from the vessel wall surface 12a and that the rods <NUM> will entrap the clot <NUM>. These cross-sectional views show the stent <NUM> unfolding in a circumferential pattern to carry the rods <NUM> around the perimeter of the clot <NUM>.

Using rods (wire, polymer etc.) to wrap around a clot <NUM> is useful to separate clot <NUM> from the wall surface 12a of the vessel <NUM> and trap it for removal. The prior series <NUM> figures show a pair of expandable stents <NUM>, <NUM> that carry the rods <NUM> so they wrap around the clot <NUM>. <FIG> show an alternative to stents or fluid inflation. This system uses two loops <NUM>, <NUM> - respectively located at proximal and distal positions and separated by rods or wires <NUM>. The loops <NUM>, <NUM> could self-activate as the system is released from inside a microcatheter <NUM> or other elongate intravascular element. The loops <NUM>, <NUM> instead could be activated by a pull wire (not shown) so that the loops <NUM>, <NUM> move into the active position. The loops <NUM>, <NUM> could be formed from wire, such as stainless steel or from shape memory material, such as NITINOL or other super-elastic material.

In <FIG>, the microcatheter <NUM> is still in place. If the system was delivered from inside the microcatheter <NUM> instead of carried by the microcatheter <NUM>, the microcatheter <NUM> may be removed. The loops <NUM>, <NUM> perform the same or similar function as the stents <NUM>, <NUM>. The loops <NUM>, <NUM> guide the rods <NUM> around the clot <NUM> to separate and extract the clot <NUM>. Also shown is an optional distal membrane or seal <NUM>, such as a bag-like component that is attached to the distal loop <NUM> to ensure that debris or clot material does not pass downstream from the clot <NUM>.

These figures show an alternative funnel-shaped distal end configuration <NUM> for the suction catheter <NUM>. Instead of a stent activation, there is a wire loop or hoop <NUM> that flips into position and opens up the funnel mouth or proximal seal <NUM>. The seal <NUM> is, in this embodiment, a separate component from the suction catheter <NUM> and pushed into place at the distal end of the suction catheter <NUM> where the wire loop <NUM> is activated to secure the proximal membrane or seal <NUM> to the distal end portion of the suction catheter <NUM>. This progression of the seal is shown in these figures. The funnel-shaped seal <NUM> then performs the functions as described herein.

This figure shows a clot <NUM> trapped in a vessel <NUM>. A conventional cylindrical suction catheter <NUM> has been advanced proximate the clot <NUM>. If suction is applied to a standard catheter some of the suction will be lost because there is no occlusion of the vessel <NUM>. It would be very useful to.

Typical suction catheters are very carefully engineered to be ultra-thin yet able to withstand suction without collapse. Also, these catheters must be maneuverable through vessels that are small and at a long distance from the operators. Interventionists become very facile manipulating these catheters and custom manufacturing a suction catheter <NUM> with a funnel-shaped distal end <NUM> may disrupt the deliverability of the suction catheter <NUM>. Thus, adding a funnel-shaped radially expandable seal tip <NUM> to an existing catheter may be a better alternative.

This figure shows a collapsed tube <NUM>, formed from a shape memory material such as NITINOL, or other suitable material, with a radially expandable seal <NUM> or funnel mouth and a cylindrical body. The figure shows a membrane or cover material on the funnel-shaped portion or mouth <NUM>. This covering material is optional but it can improve the seal. A fine layer of GORE-TEX/ePTFE may be a good choice but other materials could be used such as biologic materials (pericardium) or other polymers. There is a push wire <NUM> attached to the stent structure <NUM> to allow the stent structure <NUM> to be inserted and removed. The stent structure or tube <NUM> is shown inside a catheter <NUM> (dotted). It may be possible to insert this device without a catheter - such as from directly inside the suction catheter <NUM>.

The funnel tip <NUM> is being extruded out the end of the suction catheter <NUM>. It is more specifically extending from a microcatheter <NUM>. It may be possible to deliver this funnel tip <NUM> directly down the suction catheter <NUM>. The funnel-shaped seal <NUM> forms or takes the illustrated shape in a self-expanding manner due to the preformed shape allowed by the use of shape memory material. The membrane is shown over the shape memory material stent but it could be inside the stent or it could be between the wires of the stent.

The funnel stent-like seal <NUM> has been fully deployed. The arrow shows suction being applied by the suction catheter <NUM>. The funnel mouth <NUM> has formed a seal by radially expanding in engagement against the interior wall surface 12a of the vessel <NUM>. The funnel-shaped seal <NUM> has thereby increased the suction surface area to allow greater pull force on the clot <NUM>. The funnel-shaped seal <NUM> may also stretch the vessel wall slightly during this step to help separate clot <NUM> from the vessel wall surface 12a. The funnel-shaped seal <NUM> could be withdrawn inside the suction catheter <NUM>. Or the funnel tip <NUM> could be left in place inside the suction catheter <NUM> and the entire catheter system withdrawn together.

The distal end of the funnel-shaped seal <NUM> is shown flat, e.g., perpendicular to a lengthwise axis of the catheter <NUM>. The distal end of the seal <NUM> could instead comprise any other desired shape, such as flat but angled relative to the perpendicular direction, and/or including any other shapes or distal end configurations. For example, there may be one or more indentations on the distal end, such as one or more U-shaped indentations. Such a shape may allow the distal end to better wrap around or otherwise make engagement between the clot <NUM> and the vessel wall surface 12a. One or more U-shaped or other suitably shaped indentations or recesses that open in a distal direction could allow at least part of the funnel-shaped seal <NUM> to separate clot <NUM> from the wall surface 12a while another part of the clot <NUM> would sit inside the seal <NUM>.

These figures show the use of positive pressure (e.g., injection of fluid) between the clot <NUM> and the vessel wall surface 12a to separate the clot <NUM> from the vessel wall surface 12a. This positive pressure is directed through a microcatheter <NUM>. Then, the positive pressure catheter <NUM> may be extended beyond the clot <NUM>, as shown in <FIG> and a distal funnel-shaped or tubular seal <NUM> is deployed. Further positive pressure and/or suction applied proximal to the clot <NUM> causes the clot <NUM> to move proximally for capture and extraction. One or more physically (as opposed to fluidically) operating tools may be used to help with clot separation from the vessel wall surface 12a and/or extraction. One example would be to form a distal end portion (i.e., distal to the clot <NUM>) of the positive pressure tube or catheter <NUM> into an S-shape or other non-linear shape that will help separate the clot <NUM> from the vessel wall surface 12a upon rotation and proximal movement alongside the clot <NUM>. A wire <NUM> or similar element may be used to rotate the catheter <NUM> around the clot <NUM> to separate the clot <NUM> from the vessel wall surface 12a.

These figures show an illustrative method for removing a blood clot <NUM>. As shown in <FIG>, a suction catheter <NUM> is passed into the venous system of the patient to the site of the blood clot <NUM> as shown. The suction catheter <NUM> either includes a radially expandable seal <NUM> at its distal end, as shown, such as by having the seal <NUM> affixed thereto or integrally formed therewith, or the seal <NUM> is passed separately through the catheter and fixed in place, such as in a manner previously described or another suitable manner. As shown in <FIG>, a distal seal <NUM> is passed to a distal side of the clot <NUM> and pressurized with a fluid, as shown, such that the seal <NUM> radially expands and self-adjusts to seal against the interior wall surface 12a of the vessel <NUM>. The positive fluid pressure is then directed by the microcatheter <NUM> in a proximal direction push against the clot <NUM> and also radially expands or dilates the vessel <NUM> to stretch the vessel wall away from the clot <NUM>. See, <FIG>, <FIG>. For example, the clot <NUM> may be <NUM> long and <NUM> wide and it may be lodged in a vessel <NUM> wide. The vessel <NUM> should stretch to <NUM> - <NUM> wide and could separate the clot <NUM> from the vessel interior wall surface 12a most of the circumferential way. As shown in <FIG>, the clot <NUM> may be removed proximally with suction, combined with positive fluid pressure, as necessary or desired. As with all embodiments, the fluid suction and pressure may be constant, varied (cycled or pulsed), or both, depending on the needs of the case.

These figures show an illustrative method for removing a blood clot <NUM> that is similar to that shown in <FIG>, except that a mechanical clot dislodging device <NUM> is further used to help separate the clot <NUM> from the vessel interior wall surface 12a. As shown in <FIG>, a suction catheter <NUM> is passed into the venous system of the patient to the site of the blood clot <NUM> as shown. The suction catheter <NUM> may be constructed in one of the manners described above in connection with <FIG>, or in any other suitable manner. As shown in <FIG>, a distal seal <NUM> is passed to a distal side of the clot <NUM> and pressurized with a fluid, as shown, such that the <NUM> radially expands and self-adjusts to seal against the interior wall surface 12a of the vessel <NUM>. The positive fluid pressure is then directed proximally against the clot <NUM> and also radially expands or dilates the vessel <NUM> to stretch the vessel wall away from the clot <NUM> generally as described above in connection with the <FIG> series. For further assisting with separation of the clot <NUM> from the interior wall surface 12a, a circular or partially circular tipped element, such as a wire <NUM>, is passed back and forth along a periphery of the clot <NUM> as shown in <FIG>, preferably while suction and/or positive fluid pressure continues to be applied as illustrated. The curved wire or element <NUM> may have a radius of curvature greater than the internal radius of curvature of the vessel <NUM> to ensure that the wire or element <NUM> bears against the interior wall surface 12a slightly, and without damaging the vessel <NUM>. As shown in <FIG>, the clot <NUM> may be removed proximally with suction, combined with positive fluid pressure, as necessary or desired.

This series of figures is similar to the series of <FIG> and <FIG>, and repeated description is therefore unnecessary in regard to common steps that may be undertaken, consistent with the illustrations. The difference in <FIG> is that a guide <NUM> has been provided on the suction catheter <NUM>. This guide <NUM> may be provided on any other component used in the method, instead, and the location of the guide <NUM> on the suction catheter <NUM> is therefore just one example. The guide <NUM> comprises a channel provided at the distal end of the catheter <NUM> and, more specifically, in the radially expanded element or seal <NUM>. This guide <NUM> receives the elongate intravascular element in a manner that directs the distal end of the element <NUM> in a sideward direction toward a periphery of the blood clot <NUM>. The distal end of the guidewire <NUM> ideally passes generally between the periphery of the clot <NUM> and the interior wall surface 12a of the vessel <NUM> and exits on the distal side of the clot <NUM>, with the radially expandable seal <NUM> ready for deployment. The radially expandable seal <NUM> is then deployed in one of the manners previously described, as examples. The elongate intravascular element or guidewire <NUM> may then be used to inject positively pressurized fluid in a manner and for purposes previously described, or the element may instead be used as a component to capture emboli released from the clot <NUM> during the method of removal.

The description herein shows and describes clot removal devices that take advantage of pressure generated by a gas and/or other fluid such as a liquid. The gas could be air or any other useful gas. Helium is used in medical applications because of its low density and because it is easy to infuse in small catheters where the channel for infusion is small and long. The intra-aortic balloon pump uses this gas which can be shuttled very rapidly in and out of the balloon inside a patient due to its low viscosity. A mixture of gases such as CO<NUM> and Helium may be useful to maximize the absorption by tissue (CO<NUM>) and improve injectability (Helium).

A fluid such as saline or a dye can also be injected distal to the clot <NUM> to pressurize the membrane seals shown and described herein.

In one alternative method of operating the devices, positive fluid pressure may be applied only distally beyond the clot <NUM>. The positive fluid pressure may be pulsed or oscillated distally beyond the clot <NUM> or the pressure may be generally constant, or a combination of pulsed/oscillated fluid pressure and constant pressure may be used, as desired by the physician.

The clot <NUM> may become adherent to the intimal (interior) wall surface 12a of the blood vessel <NUM>. A positive fluid pressure can be applied proximal to the clot <NUM> to help stretch the vessel <NUM> and/or otherwise to free the clot <NUM>. Combined positive pressure proximal and distal to the clot <NUM> can potentially help free the clot <NUM> from the vessel wall surface 12a to help with extraction. Clot <NUM> that is inside an artery becomes quite adherent to the vessel wall surface 12a in a short time. It may be useful to oscillate/pulse/cycle the pressures distal and proximal to the clot <NUM> to loosen it for extraction. Or, suction applied proximal to the clot <NUM> can be alternated with cycled/pulsed positive fluid pressure distally to free and remove clots. Suction can also be used proximal to the clot <NUM> to remove the clot <NUM>. The suction can be oscillated/pulsed/cycled or constant depending on the combination of features used in accordance with this disclosure.

A combination of proximal and distal pressure manipulations (positive and negative, as well as oscillations in pressure) may indeed improve clot removal. Pressure can be constant or oscillated on each side of the clot <NUM> to help dislodge the clot <NUM>.

A control unit <NUM> can also be added to the system to control the pressures proximal to the clot <NUM> and the positive pressure distally beyond the clot <NUM>. This control unit <NUM> may consist of pumps and vacuums that can be used to deliver the ideal pressures and pressure fluctuations.

It may also be useful to have gas or other fluid(s) positively infused around the clot <NUM>. Holes in the pressure inflation catheter that is passed distally beyond the clot <NUM> may also include holes adjacent or proximate the clot <NUM> to impact the clot <NUM>. This may help to separate the clot <NUM> from the vessel wall surface 12a and help with clot removal. When removing a clot surgically, the surgeon has spatula-shaped tools to separate clot from the vessel wall. Gas infusion or other fluid infusion around the clot <NUM> may be advantageous for similar effect without similar risk of vessel damage.

To maintain ideal clot removal conditions, it may be useful to add pressure sensors to the control <NUM>. These sensors can be inside a control unit or attached to or included in the clot suction catheter <NUM> and the catheter that is placed distally beyond the clot <NUM>. Small micro-transducers can be added to the catheters at useful locations to help monitor the pressure inside the patient. A high pressure may lead to a vessel rupture. Too low a pressure may not provide adequate force to remove the clot <NUM>. Certain pressure levels may indicate a clot <NUM> has plugged the suction catheter <NUM> or that the clot <NUM> is traveling proximally through the suction catheter <NUM> during removal.

As described previously, CO<NUM> is a good imaging agent in radiology. When CO<NUM> is infused it provides a negative image as opposed to dyes (which typically contain iodine) which are positive images. The length of the clot <NUM> is often unknown because the dye stops at the clot <NUM>. By passing a catheter distally beyond the clot <NUM> and infusing CO<NUM> beyond the clot <NUM>, the distal side of the clot <NUM> can be imaged. This combination of imaging with dye on one side of the clot <NUM> (proximal) and CO<NUM> on the other side of the clot <NUM> (distal) may provide useful information on the length of the clot <NUM>. This can help to position the catheters and devices to optimize removal of the clot <NUM>.

The table below contains a number of features shown and/or described herein. Combinations of systems, devices and methods may be assembled by using at least one of the features listed in the table and/or by combining two or more features from the table. Note, "RES" refers to "radially expandable seal" such as the wide variety of proximal and distal membranes or seals shown and described herein. "EIE" refers to "elongate intravascular element" such as the suction catheter <NUM>, guidewire <NUM>, microcatheter <NUM> or other EIEs contemplated herein.

A non-limiting table of features in accordance with some embodiments of this disclosure is provided below. Some of the features relate to non-structural items such as suction and/or positive pressure delivery and control. These features are discussed throughout the present specification with regard to most embodiments. For example, some embodiments will include only suction pressure on the proximal side of the clot <NUM>. As one option, the structure in <FIG> may be used without the positive pressure supplied through guidewire <NUM>, but still using suction through catheter <NUM>. In this case, the distal seal <NUM> would be used as an emboli capturing element to trap emboli before they travel farther downstream into the brain. Other combinations of one or more pressure options from column <NUM> may be utilized to beneficial effect depending on the case. As also discussed throughout the specification, the user may choose from a variety of fluid options to deliver positive pressure proximate the clot <NUM>. Some options are listed in column <NUM> and may be used alone or in combination to the desired effect by the user. Distal RES options are listed in column <NUM> and, for example, are shown and described as various forms of seals or membranes throughout the specification. One or more distal seals, again, may or may not be combined with other features listed in the table. Proximal RES options are listed in column <NUM> and, for example, are shown and described as various forms of seal <NUM> throughout the specification. One or more of these proximal seals configurations <NUM>, again, may or may not be combined with other features listed in the table. Column <NUM> lists options for devices or components specially configured to assist with clot dislodgement and removal. For example, some specific examples are shown and described with respect to <FIG>, <FIG>, and Figure series <NUM> through <NUM> where several configurations for a distal membrane <NUM> are shown and described. Column <NUM> lists various options for guiding an EIE, such as a guidewire <NUM> or microcatheter <NUM> into position near the periphery of a clot <NUM> such that it may be directed past the clot <NUM> adjacent to the vessel wall surface 12a. Specific examples are shown and described in connection with <FIG>, <FIG>and <FIG>. Column <NUM> lists various control options that may be used alone or in combination with each other and with one or more of the other features/options listed in the table. In accordance with the concepts, the features in any given column (<NUM>-<NUM>) below may be utilized alone or in combination, or a feature or multiple features from two or more columns may be utilized in combination to dislodge and remove a clot <NUM>.

Claim 1:
A system for removing a blood clot (<NUM>) from a blood vessel (<NUM>) of a patient, comprising:
a catheter (<NUM>) having a distal end portion,
a radially expandable distal seal (<NUM>) deployable from the distal end portion of the catheter (<NUM>) and open at its proximal end portion, wherein the radially expandable distal seal (<NUM>) is configured to expand radially in use and provide a fluid pressure seal against and engage with the interior wall surface (12a) of the blood vessel (<NUM>) when radially expanded to allow pressure to be applied to the blood clot,
a fluid pressure delivery apparatus for applying fluid pressure intravascularly through the catheter (<NUM>) to an area of the blood vessel (<NUM>) between the radially expandable distal seal (<NUM>) and the blood clot (<NUM>) to (a) radially expand the radially expandable distal seal (<NUM>) to form and maintain a fluid pressure seal against the interior wall surface (12a) of the blood vessel (<NUM>), and (b) apply a pressure on the blood clot (<NUM>) in a proximal direction, and
a blood clot retrieval element to be disposed proximal to the blood clot (<NUM>) and for capturing the blood clot (<NUM>) in the blood vessel (<NUM>).