Abstract:
An aortic flow diverter or filter is described that diverts particles away from the carotid vessels and right subclavian artery. The diverter includes a stent-like portion formed from a plurality of braided or woven wires that can radially self-expand. The stent-like portion is generally tubular and is fixed over the distal end of a catheter or shaft. A sheath is located over both the catheter and stent-like portion, maintaining the stent-like portion in a compressed configuration. When withdrawn proximally, the sheath releases the stent-like portion, allowing it to expand against the walls of the vessel.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/833,223 filed Jun. 10, 2013 entitled Methods and Devices for Embolic Protection, which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    As the world population continues to age, cardiovascular procedures will grow in frequency and complexity. In order to improve the safety and efficacy of such procedures, the complication of embolism associated with those procedures must be addressed. 
         [0003]    An embolism is when thrombus or atheroma or calcium breaks loose from a patient&#39;s vasculature during a procedure and migrates distally and lodges in a peripheral vessel causing ischemic injury to the end organ. 
         [0004]    A particularly acute complication is a cerebral embolism where an emboli lodges in one of the arteries of the brain and thus causes an injury to the brain. Accordingly, in a preferred embodiment, the invention focuses primarily on cerebral protection during heart operations such as coronary artery bypass surgery (CABG) and valve replacement, the latter being performed either by open chest surgery or through percutaneous delivery, e.g., trans-catheter aortic valve replacement (TAVR). 
         [0005]    Traditional cerebral protection during open or closed heart procedures has involved administration of blood thinners (e.g. anticoagulants). However, this approach is directed more to the risk that arises due to the bleeding caused by surgical incisions. Such blood thinners do not address complications where the embolism is not responsive to anticoagulation. 
         [0006]    Other methods include the use of aortic cannulas which have filters incorporated (e.g., Embolex) in the aorta as a way of protecting the brain. However, the large size and rigidity of these cannulas make them somewhat cumbersome. 
         [0007]    More recently, in connection with TAVR procedures, surgeons have used diverters or filtration devices such as CLARET and EMBRELLA. Information regarding these devices are described and explained in the following references:
       1. “Embolic Protection during TAVI Embrella,” Nikos Werner, Universitätsklinikum Bonn, Bonn, Germany, CS Frankfurt 2012.   2. “Brain Damage—Will Embolic Protection Devices Reduce Strokes After TAVR?”, Andreas Baumback, MD, FRCP, FESC, Bristol Heart Institute, University Hospitals Bristol, ICI 2012.   3. “CardioLogical Receives Patent for Aortic Embolic Protection Devices to Prevent During TAVR,”  Diagnostic and Interventional Cardiology,  Apr. 12, 2013, www.dicardiology.com/article/cardiological-receives-patent-aortic-embolic-protection-devices-prevent-during-tavr, accessed Apr. 28, 2013.   4. “Emboline,” www.emboline.com/technology.html, accessed Apr. 28, 2013.   5. “Intraprocedural Intraaortic Embolic Protection With the EmboIX Device in Patients Undergoing Transaortic Transcatheter Aortic Valve Implantation (TAo-EmboIX),” ClinicalTrials.gov, clinicaltrials.gov/ct2/show/NCT01735513, accessed Apr. 28, 2013.   6. “Embolic Protection Devices for TAVR Show Promise,” TCTMD,  The source for Interventional Cardiovascular News and Education,  www.tctmd.com/show.aspx?id=110221&amp;AspxAutoDetectCookieSupport=1, accessed Apr. 28, 2013.       
 
         [0014]    These devices can essentially be divided into two categories: 1. Flow diverters where the emboli are diverted from entering vessels, e.g., the cerebral vessels; and, 2. Filtration devices where the emboli are captured and removed from the blood stream entirely. 
         [0015]    The reliability and effectiveness of these devices is yet to be reliably verified. The need for some type of embolism protection, however, remains essential. Accordingly, there is an ongoing need for the development of systems and methods of protecting patients from emboli that are safe and effective. Accordingly, it is an object of the present invention to provide a system and method of more effectively providing protection from embolism to a patient during surgical procedures, and particularly protection from cerebral embolism. 
       SUMMARY OF THE INVENTION 
       [0016]    One embodiment of the present invention is directed to an aortic flow diverter or filter that diverts particles away from the carotid vessels and right subclavian artery. Preferably, the diverter includes a stent-like portion formed from a plurality of braided or woven wires that can radially self-expand. The stent-like portion is generally tubular and is fixed over the distal end of a catheter or shaft. A sheath is located over both the catheter and stent-like portion, maintaining the stent-like portion in a compressed configuration. When withdrawn proximally, the sheath releases the stent-like portion, allowing it to expand against the walls of the vessel. 
         [0017]    In one embodiment, the filter is positioned through the right subclavian artery, over the opening of the right common carotid artery and into the left common carotid artery. The sheath is withdrawn, allowing the stent-like portion to expand. A trans-catheter aortic valve replacement (or other similar procedure) is performed to repair or replace an aortic valve. Once the valve procedure is complete, the sheath is advanced over the stent-like portion and the filter is removed from the patient. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which: 
           [0019]      FIG. 1  is a rendering of one preferred embodiment of an aortic flow diverter (AFD) in accordance with the present invention shown being used during a TAVR procedure; 
           [0020]      FIGS. 2A-2F  are renderings of the various steps of deploying and retrieving an aortic flow diverter in accordance with one preferred embodiment of the present invention; 
           [0021]      FIGS. 3A-3B  are renderings of preferred embodiments of the working end of an aortic flow diverter in accordance with the present invention; 
           [0022]      FIG. 4  is a rendering of a preferred embodiment of the back end of an aortic flow diverter in accordance with the present invention; 
           [0023]      FIG. 5  is a rendering of a preferred embodiment of an aortic flow diverter in accordance with the present invention shown being used during a TAVR procedure; and, 
           [0024]      FIGS. 6A and 6B  is a rendering of a preferred embodiment of an aortic flow diverter. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
         [0026]    In accordance with one embodiment of the present invention, a dual layer self-expanding Nitinol frame stent-like device is used as a flow diverter during cardiovascular procedures to prevent cerebral embolism. 
         [0027]    Such a stent-like device used in the manner herein disclosed reduces the embolic load to the brain by effectively diverting the particles away from the carotid vessels and right subclavian artery. One reason that such effectiveness is obtained is because the device achieves superior wall apposition. 
         [0028]    Moreover, using a stent-like device (or other similarly configured device) in this manner is low profile and thus avoids taking up space in the femoral artery (which must remain open for TAVR devices  50 ) and avoids the aortic arch  16 . Hence, the device and technique substantially (if not completely) avoids impeding the valve replacement procedure. 
         [0029]    Referring to  FIG. 1 , an aortic flow diverter  100  having a double layer Nitinol retrievable self-expanding stent-like portion  104  is shown in its deployed state extending from the right subclavian artery  10 , over the opening of the right common carotid artery  12  and into the left common carotid artery  14 . This deployment is shown in the context of a TAVR procedure TAVR catheter  50 . However, the aortic flow diverter  100  can be used in any type of heart procedure including more traditional aortic valve replacement (AVR) procedures. 
         [0030]    Due to the flexibility and expandability of the woven/braided stent-like portion  104  of the diverter  100 , superior apposition of the diverter frame against the inner walls of the vessels is achieved. This ensures that a minimum number and minimum size of emboli are allowed into the cerebral arteries. Hence, the braiding and/or mesh characteristics of the woven/braided stent-like portion  104  of the diverter  100  divert such emboli away from the cerebral arteries. 
         [0031]    In a preferred embodiment the woven/braided stent-like portion  104  of the diverter  100  is a tubular, dual-layer, self-expanding, Nitinol frame stent-like member made by Microvention, Inc. under the name CASPER. A representation of this stent can be found in U.S. Publication No. 2012/0310319 entitled Stent, published Dec. 6, 2012, which is herein incorporated by reference in its entirety. 
         [0032]    Referring to  FIGS. 2A-2F , one embodiment of a method for deploying and retrieving an aortic flow diverter  100  in accordance with the present invention is disclosed. 
         [0033]    Referring to  FIG. 2A , a guidewire  102  is directed from the RSCA  10  to the LCCA  14  of the patient. In a preferred embodiment the guidewire  102  is a stiff 0.035″ Amplatz guidewire. A catheter  104  (e.g., a Simmons 2 catheter) is then delivered over the guidewire  102 . 
         [0034]    Referring to  FIG. 2B , a sheath  106  (e.g. 6F in size) containing the aortic flow diverter  100  compressed on a catheter shaft  108  of a delivery catheter  108  (shown in  FIGS. 3A and 3B ) is then placed over the guidewire  102 . The sheath  106  and catheter  108  are advanced over the guidewire, through the RSCA  10  to the LCCA  14  of the patient. In a preferred embodiment, the sheath  106  is a 6F Cook sheath or 6F Terumo Pinnacle sheath. 
         [0035]    Referring to  FIG. 2C , deployment of the aortic flow diverter  100  is initiated by withdrawing the sheath  106  to expose the tubular, stent-like portion  104  on the catheter shaft  120 , after purging the system of any air bubbles. 
         [0036]    Referring to  FIG. 2D , further deployment of the diverter  100  is shown as the sheath  106  continues to be retracted. As the stent-like portion  104  is exposed, it self-expands radially against the walls of the vessels. Also shown are the initial steps of a TAVR procedure where a TAVR catheter  50  is advanced through the femoral artery and into the aorta  11 . 
         [0037]    Referring to  FIG. 2E , full deployment of the stent-like portion  104  of the diverter  100  is depicted, as the sheath  106  is retracted into the RSCA  10 . Due to the wall apposition of the stent-like portion  104 , any emboli resulting from the TAVR procedure are diverted away from the cerebral arteries. 
         [0038]    Referring to  FIG. 2F , the diverter  100  is retrieved by advancing the sheath  106  in a distal direction and thereby causing the stent-like portion  104  to be contracted inwardly on to the catheter shaft  120 . Once the stent-like portion  104  is fully captured in the sheath  106 , the entire apparatus (i.e., the sheath  106 , catheter  108 , diverter  100 , and guidewire  102 ) is removed from the patient. 
         [0039]    Referring to  FIG. 3A , the distal working end of the diverter  100 , catheter  108 , and sheath  106  in the closed position is shown. As can be seen, the sheath fully captures the stent-like portion  104  of the diverter  100 . A nose cone  114  at the distal end of the catheter shaft  120  allows smooth advancement of the device into the carotid vessels. In order to ensure proper placement of the diverter  100 , radiopaque markers  112  are disposed on the proximal and/or distal ends of the stent portion of the stent-like portion  104 . Additionally, the sheath  106  may include a monorail opening  106 A near its distal end for over-the-wire use. 
         [0040]    Referring to  FIG. 3B , the working end of the diverter  100  in the open position is shown. As can be seen, the sheath  106  has been withdrawn proximally, thus allowing the stent-like portion  104  to expand. The nosecone  114  is separated from the distal end of the stent-like portion  104  of the diverter  100  by the radial expansion of the stent-like portion  104  peeling away from the shaft  120 . The proximal portion of the stent-like portion  104 , however, remains fused (e.g., by an adhesive, metal band, or welding) at point  104 A on the shaft  120 , preventing it from opening and allowing the stent-like portion  104  to be easily retrieved. 
         [0041]    Preferably, the stent-like portion is woven or braided with at least two different diameter wires. For example, larger diameter wires  156  (e.g., 0.002-0.004 inches) can form a more rigid framework while smaller diameter wires  158  (e.g., 0.0010-0.0020 inches) can be woven to form a relatively small pour size (e.g. 150-200 microns). Preferably, both of these wires are made from Nitinol and are electropolished. These wires  156  and  158  can be woven into a single layer or the larger diameter wires  156  can be woven into an outer layer and the smaller diameter wires can be woven into an inner layer that is physically connected to the outer layer at various locations. 
         [0042]    Referring to  FIG. 4 , the back end of the sheath  106  is connected with a traditional Touhey Borst adapter  122 . The shaft  120  and stent-like portion  104  are movable in and out of the adapter  122  over the guide wire  102  into and out of the vessels as needed. 
         [0043]    Referring to  FIGS. 5 ,  6 A, and  6 B, another embodiment of a diverter  150  is shown wherein the stent-like portion  152  has a tapered and/or closed distal end  154 A just below the nosecone with which it is fused to provide distal filtration. The proximal end is similar to that shown in  FIG. 4 , in which the sheath  106  is connected to a Touhey Borst via a hub  115 . Additionally, the inner shaft  120  may include a handle  123 . 
         [0044]    In one embodiment, the pore size or cell size of the outer layer of the dual layer stent be 200-250 microns. This pore/cell size together with the radial expansion characteristics of inner frame/layer of the dual layer stent provides both the radial strength needed to give radial conformity and yet is still deliverable as well as maximize flow diversion. Small pore size reduces the particles that enter the stent and cerebral vessels during the filtration process. 
         [0045]    In a preferred embodiment, e.g., see  FIG. 5 , the distal end of an outer layer of the dual layer stent is closed just beyond the inner layer. This configuration provides supplemental filtration of the left carotid artery and traps any material that enters the first layer of the dual layer stent. In another embodiment, the distal end of the outer layer remains open while the distal end of the inner layer is closed. 
         [0046]    In another embodiment, the distal end of the stent-like portion can include a plurality of anchors to help maintain its position within the left common carotid artery. For example, such anchors could include a plurality of spikes, hooks, coils, or similar structures that are radially disposed on an outer surface of the stent-like portion. 
         [0047]    In another embodiment, the stent-like portion has a length between 3-12 inches. 
         [0048]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.