Abstract:
A therapeutic interventional device such as a balloon catheter is provided with a nozzle to induce a retrograde flow in the vessel by injecting fluid through the nozzle into the vessel. The retrograde flow can be used to clear debris from a distal protection device such as a filter or balloon and may additionally be used to clear the vessel of clot prior to the intervention.

Description:
CROSS REFERENCES  
       [0001]    The present invention claims the benefit of co-pending application 10/050,978 filed Jan. 18, 2002, entitled Fluidic Interventional Device and Method of Distal Protection, which is incorporated by reference herein in its entirety.  
         [0002]    The present application claims the benefit of provisional application 60/373,117 filed Apr. 17, 2002, entitled Filter Wire incorporated by reference in its entirety herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0003]    It is now widely recognized that cardiac interventions such as angioplasty can release an extraordinary amount of debris. If this debris flows downstream, it can clog vessels and propagate a cascade of injury. Although debris collection for the coronary arteries has been proposed, the primary application for “distal protection devices” is in saphenous vein graft interventions where occlusive material is friable and extensive, and in carotid interventions where the release of even small amounts of debris can lead to stroke or blindness and other neurological disorders.  
           [0004]    The two dominant forms of distal protection device under investigation today include the Percusurge guard wire, which is a elastomeric occlusion balloon on a wire which is used to traverse a stenotic lesion and is inflated to block flow. A cardiovascular intervention such as stent placement, angioplasty, or artherectomy or the like takes place behind the occlusion balloon and is typically delivered over the guide wire portion of the balloon system. Although such systems have been proven safe and effective and have been released for marketing, there are continuing issues of “halo” and balloon shadow. It appears from clinical investigation that the occlusive balloon itself moves slightly in the vessel trapping debris between the balloon and the blood vessel. On the distal or downstream side of the device, blood stagnates around the outer periphery of the balloon and in the instance of a long intervention or an unheprinized patient this adherent material may form a ring or halo and be sloughed off as the occlusion balloon is deflated. Although such balloon-based systems achieve 100 percent occlusion of the vessel during the intervention, they are unable to extract 100 percent of the released debris either because the debris is trapped by the balloon or formed behind the balloon. In these instances, no amount of straight aspiration or irrigation followed by aspiration will remove the debris. The system taught by the present application permits 100 percent removal of occlusive material with the obvious patient benefit.  
           [0005]    The alternative filter wire technology places a net or filter mesh distal across the lesion and material “created” or released during the intervention behind or proximal of the filter wire is collected in the filter wire basket. The typical filter wire has an approximately conical shape like a butterfly net and has sufficient volume to trap a relatively large amount of debris. However, there are instances where the quantity of debris or the quality of debris created during the intervention overwhelms the collection capacity of the filter wire and the filter wire itself becomes a total occlusion preventing the profusion of oxygenated blood to distal tissues. It is possible that the amount of debris is so large that the filter wire cannot be retrieved. The present invention permits the filter wire to be “emptied” peri-operatively which allows both profusion and retrieval. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a schematic diagram of a medical device in a vessel;  
         [0007]    [0007]FIG. 2 is a schematic diagram of a medical device in a vessel;  
         [0008]    [0008]FIG. 3 is a schematic diagram of a medical device in a vessel;  
         [0009]    [0009]FIG. 4 is a schematic diagram of a medical device in a vessel;  
         [0010]    [0010]FIG. 5 is a schematic diagram of a medical device in a vessel;  
         [0011]    [0011]FIG. 6 is a schematic diagram of a medical device in a vessel;  
         [0012]    [0012]FIG. 7 is a schematic diagram of a medical device in a vessel;  
         [0013]    [0013]FIG. 8 is a schematic diagram of a medical device in a vessel;  
         [0014]    [0014]FIG. 9 is a schematic diagram of a medical device in use in a vessel with a collection bag coupled to a guiding sheath. 
     
    
     DETAILED DESCRIPTION  
       [0015]    [0015]FIG. 1 shows a fluidic extraction nozzle  12  embodying the Coanda effect on a filter wire sheath  10 . In use the filter wire sheath  10  is advanced antegrade as indicated by arrow  14  toward the lesion  16 . With the extraction section  12  activated with heperinized saline or diluted contrast agent a flow is induced in the retrograde direction by primary jet  18  emerging from the extraction section  12 . Debris released by the initial crossing of the lesion  16  is propelled in the retrograde direction as indicated by particle and motion arrow  20 . These particles will be carried by the blood flow indicated by flow arrow  22 . These particles will be collected in bag  810  seen in FIG. 9  
         [0016]    [0016]FIG. 2 shows a stand-alone extraction catheter  30  carried by a rapid exchange lumen  32  on the guide wire shaft  31  of a filter wire device. In this embodiment the extraction section  12  causes a pressure difference across the filter wire basket  34 . The blood flows retrograde through the basket as indicated by arrow  38 . In this embodiment he retrograde flow is used to “empty” the basket. This allows the clinician to liberate and collect large quantities of debris without concern. The filter will not get too full to remove. The debris will be in the bag  810  (FIG. 9).  
         [0017]    [0017]FIG. 3 shows a filter wire  40  positioned to collect debris liberated by the angioplasty balloon  42 . It is important to note that while the therapy balloon  42  is inflated there is essentially no flow in the vessel  44 . The particulate typified by particle  46  is stagnant and not moving very far or very fast. If the extraction section  12  is turned on during the balloon inflation there will be a pressure difference created across the lesion  16 .  
         [0018]    When the balloon is deflated as seen in FIG. 4 the particulate moves retrograde as typified by particle  48 . In this instance the filter wire  40  acts as a safety net to capture debris in the unlikely event that the are not captured by retrograde flow.  
         [0019]    [0019]FIG. 5 shows the system of FIG. 1 further including a therapy balloon  42  added to the delivery sheath  10 . This version uses an alternate design extraction section with a wall angle of about zero and a jet angle approaching 180 degrees. In this figure a pressure difference is created across the stenotic lesion  16  by the fluid ejected from extraction section  12 . The filter wire  40  is shown partly deployed to show the construction of the sheath.  
         [0020]    Turning to FIGS. 6 and 7 and  8  it is quite possible that effective distal protection of vessels can take place without the use of either filter or balloon occlusion devices as follows:  
         [0021]    [0021]FIG. 6 shows a conventional guidewire  80  traversing a lesion  16 . The extraction section  15  is injecting fluid  18  which may be dilute contrast agent or heprinized saline. As the lesion  16  is crossed the blood flow  82  induced by the retrograde flow  18  drags particles like particle  84  in the retrograde direction.  
         [0022]    [0022]FIG. 7 shows the therapy balloon  42  pushed across the lesion  16  and inflated. The author believes that the bulk of the particles created are created by balloon expansion. However the balloon  42  now occludes the vessel and the particles like particle  88  is motionless since there is no blood flow. The extraction section continues to pump but the retrograde flow stops and the contrast agent mixes with the blood and displaces it through a serial dilution process indicated by arrow  90 . The space behind the balloon fills with contrast agent and the doctor has a visual confirmation that the therapy balloon has occluded the vessel. It is important to note that the pressure gradient across the therapy balloon will induce retrograde flow as soon as the balloon is even slightly deflated as illustrated in FIG. 8.  
         [0023]    [0023]FIG. 8 shows the therapy balloon  42  in a collapsing condition which opens the vessel  44  permitting full retrograde flow as indicated by arrow  92 . Even particles that have migrated in the distal direction are captured and carried out to bag  802  by the injected flow  18 . The physician will see the contrast agent swept from view in the retrograde direction confirming adequate particulate capture. Doctors will think this is really cool and the patients get a great benefit at a very low cost.  
         [0024]    In the figures two different geometries of extraction sections are taught. Although these may be readily substituted for each other throughout the figures, they differ in some regards. The section illustrated generally as  12  consists of a set of radial projecting apertures which introduce fluid at a jet angle of approximately 90 degrees with the center axis of the catheter. A nubbin is located adjacent the slits and this nubbin guides the flow into the retrograde path. Such devices are further described elsewhere in my published patents and appear to be particularly useful when one desires to use contrast agent as the injectate to drive the extraction section. In these instances the volume between the aperture and the occlusion device which may be a therapy balloon or a distal occlusion balloon fills up quickly with contrast agent permitting the visualization of the lesion as well as the position of the occlusion element. If the occlusion element is deflated, then the contrast agent is swept from the system through the retrograde pumping action of the extraction section providing a visual confirmation fluroscopically of the extraction of debris. This is particularly helpful for balloon-based interventions where the occlusions prevent the introduction of contrast agent using conventional techniques. Physicians like the additional flexibility associated with being able to see what they&#39;re doing wherever they are in the course of the procedure. The nubbin of the extraction section is positioned with a wall angle of approximately 0 degrees that as the jet approaches the nubbin surface on a tangent. Other wall angles can be utilized and in particular a wall angle of about 45 degrees seems to promote a rapid filling of the treatment volume when injected with fluid.  
         [0025]    An alternative geometry for the Coanda extraction section is set forth on FIGS. 6,7 and  8  which show a cuff or cup over one or more apertures. In this construction injectate fluid enters the cuff from a lumen in the catheter body and squirts out the back. The jet angle is approximately 180 degrees while the wall angle is nearly 0 degrees as the jet attaches to the catheter shaft and flows in the retrograde direction. This geometry establishes a good pressure recovery for the energy within the jet and creates a perceptible pressure difference across the therapy balloon or the occlusion balloon. The mixing process is not as vigorous with this geometry and if it is used against a total occlusion, the treatment volume takes substantially longer to fill with contrast agent. It is likely that the optimal geometry is intermediate between a Coanda extraction section having a jet angle between 90 and 180degrees and a wall angle of between 0 and 45 degrees.  
         [0026]    [0026]FIG. 9 shows the overall context of the system where the patient&#39;s blood vessel  800  carries an interventional guide sheath  802  which in turn delivers an extraction catheter  804 . The extraction catheter may be delivered over a guide wire  806 , or it may be delivered without the benefit of a guide wire and lie loose in the extraction sheath  802 . Injectate is forced into the catheter  804  through an injector  810  which will typically be an angiographic power injector, although in certain versions hand injection may be useful as well. The extraction sheath and guide catheter sheath  802  together form a collection system which will terminate in a collection bag  810  placed bedside next to the patient. In general if this bag is placed below the patient, the patient will bleed into the bag through arterial pressure and gravitational siphon. If the bag is placed above the patient, debris and the like in the bag would be reintroduced into the patient. In most instances the Coanda extraction section on the extraction catheter  804  will produce an output pressure of several inches of water which will be sufficient to take material in the antegrade flow induced by the Coanda extraction section into the guide catheter  802  and deposit the material in the collection bag  810  where it can be examined and filtered to determine the content, nature and amount of debris recovered.  
         [0027]    To assist entry of debris into the open mouth of the guide catheter  802 , there are three solutions. First a balloon  850  may be used to seal the space between the vessel wall  44  and the catheter body. Next a supplemental pumping station may be placed in the lumen of the device  802 . The extraction section  13  may be powered at the same time as the more distal extraction section  12 . The two extractions sections  13  and  12  may be operated at different times and for different duration. A third solution is the application of suction from a syringe or the like to the lumen of the sheath device  802 . Any of these solutions may used separately or they may be combined in any permutation.