Patent Publication Number: US-2020297416-A1

Title: Septotomy Catheter for Aortic Dissection

Description:
RELATED INVENTIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 15/602,516, filed May 23, 2017 (now U.S. Pat. No. 10,610,295); which application is a continuation of U.S. application Ser. No. 15/131,504, filed Apr. 18, 2016 (now U.S. Pat. No. 9,681,915); which application is a continuation-in-part of U.S. application Ser. No. 14/591,642, filed Jan. 7, 2015. U.S. application Ser. No. 15/131,504, also claims benefit of priority of U.S. Provisional Application Ser. No. 62/300,252, filed Feb. 26, 2016. The above-identified related applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to medical methods and devices for treating aortic dissections; and more particularly for safely cutting the septum of an aortic dissection. 
     BACKGROUND OF THE INVENTION 
     Aortic dissection is an uncommon but often lethal condition where the inner layer of the aorta separates from the outer layer, creating a double channel. The moving septum thus created disrupts the flow of blood to the legs and viscera. Additionally, the thin outer wall resulting from the delamination of the aorta often develops into an aneurysm that may eventually rupture. 
     Generally, a dissection starts by a tear involving the inner layer of the aorta that causes the inner layer to separate from the outer layer over part of the circumference of the aorta. Upon dissection, a new channel is formed between the separated outer and inner layers of the blood vessel wall of the aorta. This results in the aorta having two channels instead of one. The inner layer of the blood vessel wall that has separated is called the septum (or the flap) and separates the two channels. 
     One of the two channels formed in a dissection continues to function as a blood vessel, allowing the blood to flow through it. This channel is called the “true lumen.” The newly formed second channel through which blood also flows is called the “false lumen.” The true and false lumens communicate proximally through a proximal tear and distally through one or possibly various existing distal tears. In some dissections, there is no distal tear. 
     A dissection which involves the thoracic aorta is called a “thoracic aortic dissection.” There are two types. Type A dissections involve a dissection in the ascending aorta, while type B dissections involve any segment of the descending aorta. Type A dissections require immediate surgery. Management of type B dissections is the subject of controversy. Some doctors advocate temporary medical management, while others advocate immediate stent-grafting. In cases where the septum is blocking an opening of a major artery supplying the viscera or the leg, urgent surgery may be required, and may be limited to a resection of part of the septum (fenestration) providing communication between the true and the false lumens. In a few cases, this needed communication can be achieved by perforating the septum and enlarging the resulting perforation with a balloon (balloon fenestration). 
     A variation of the balloon fenestration involves inserting and advancing two wires through the false and true lumen to a proximal point, and linking the two wires in some fashion to cut the septum with the resulting wire loop. This variation lacks control of the site and of the length of the tearing maneuver. These attempts have been complicated by anecdotal reports of high pressure of the false lumen channel with collapse of the true lumen and by detachment and folding of the septum, obstructing the outflow of the aorta. 
     One of the wires should be advanced into the true lumen, the other into the false lumen. Entering the false lumen would be easy if both lumens reach down to the femoral artery puncture site. If the false lumen ends proximal to the femoral artery, the false lumen could be engaged by penetrating the orifice of communication between the true and the false lumen, or by puncturing the septum as distally as possible, inserting a wire in the false lumen and dilating the orifice with a balloon to allow the septotomy cutter to engage the septum at this point. Both wires should come out of the body through the same orifice, either a cut-down in the common femoral artery or a sheath inserted in it. 
     Catheter based cutting methods and tools for aortic dissections are found in Bliss, US 2011/0118769. Bliss primarily teaches use of a movable cutting blade, where a U-shaped or hooked tool penetrates a septum, then hooks and cuts the septum in a proximal to distal direction by retracting a portion or entirety of the catheter, or by distally translating the cutting blade relative to the septum. The cutting of a septum of a aortic dissection, in a proximal to distal direction, is problematic. This type of cutting, by the pulling of the septum in a distal direction, using a fixed or movable blade, may result in sudden collapse of the true lumen with catastrophic consequences. Safe division of the septum requires distal to proximal cutting. 
     Bliss does suggest one embodiment of a catheter based cutting device intended to operate in a retrograde manner (i.e., cutting the septum from distal to proximal along the aortic dissection). The embodiment has fixed, passive, cutting blade fashioned from a small, standard surgical knife (razor blade) intended to be pushed proximally against the septum by an inner tubular component (actuator) of the catheter. This passive cutting blade does not permit a controlled septotomy. The actuator acts as a telescopic mechanism by sliding inside an outer tubular component of the catheter. The coaxial catheter system extends the length of the catheter and creates substantial friction during advancement of the catheter within the blood vessel. The friction naturally increases with any increase in diameter of the two tubular components. A catheter with inner and outer tubular components functioning telescopically does not have the flexibility to navigate the bends of the arterial system and, if some bending has been achieved, the friction between the two tubular components would increase dramatically. Further, the embodiment disclosed includes a distal end having a fixed “Y” assembly. A stationary cutting blade (razor blade) is adhered between diverging ends of two tubular components (or fixed arms) in a Y-shape. The resultantly immobile, Y-shaped distal end is a substantially large assembly for introduction into (and maneuverability within) a blood vessel. Further, maneuverability and control of the cutting assembly at the septum, during septum cutting, and the required pushing of a fixed, passive blade against the septum, makes this embodiment inoperable. 
     What is needed is a catheter based cutting device operable in a retrograde manner, having a cutting assembly and cutting component that controls the site and length of the septum cut in both acute and chronic aortic dissection. In acute dissections, the device would equalize pressure between the true and the false lumens, potentially avoiding development of an aneurysm, as well as correcting malperfusion of the viscera or legs. Acute aortic dissections often require only a few centimeters of septum division to equalize pressure between the lumens, and to provide low resistance outflow of both lumens to avoid development of aneurysmal dilatation of the false lumen (e.g., 5-15 cm in the instance of cutting from the level of the aortic bifurcation to below the renal arteries). In chronic dissections, where different viscera may be perfused by either lumen, a cutting device is needed to convert the double lumen into a single one, where cutting the fibrous septum permits insertion of a branched endograft in a manner similar to that used in thoracoabdominal aneurysms. Also needed is a catheter based cutting device having no mechanical actuator, providing small profile construction, where the cutting component is an electrode or a fiber delivering energy that cuts the septum upon placement, without need for a mechanical push mechanism. As a result, the catheter can have a small diameter and increased flexibility which facilitates advancement of the catheter through a tortuous aorta. 
     SUMMARY OF THE INVENTION 
     The present invention solve the problems noted above, providing catheter-based cutting methods and devices operable in a retrograde manner (distal to proximal cutting), that controls the site and length of the septum cut in both acute and chronic aortic dissection. In acute dissection, the present catheter equalizes pressure between the true and false lumens, potentially avoiding the development of an aneurysm, as well as correcting malperfusion of the viscera or legs. In chronic dissections, where different viscera may be perfused by either lumen, the present catheter converts the double lumen into a single one, where cutting the fibrous septum permits insertion of a branched endografit in a manner similar to that used in thoracoabdominal aneurysms. The present catheter has no mechanical actuator and hence can be constructed with small profile. As a result, the present catheter has a small diameter with increased flexibility which facilitates advancement through tortuous aorta. 
     The catheter of the present invention avoids the need for a mechanical actuator which would need to be operated from the entry point of the catheter to its end, usually about 70-80 cm away, and allows the construction of a cutting catheter with a low profile since it does not need rigid mechanical actuators for the mechanical blade. The present catheter has the flexibility needed to accommodate the curves of the aortic and iliac arteries system. The bifid end of the catheter, when introduced, is collapsed and has the same diameter as the rest of the catheter. The two arms of the catheter only open when the wires that guide them diverge after encountering the lower end of the septum. 
     The present invention provides catheter-based cutting methods and devices operable to cut the septum of an aortic dissection (septotomy), whether the dissection is acute or chronic. The invention involves a septotomy catheter having a base section with a pair of bifid arms extending from a distal end of the base section. The catheter uses guide wires that extend through and beyond the arms to guide the septotomy catheter such that an area defined by a vertex formed by the two arms and base section of the catheter will engage a septum when the catheter is advanced, in a retrograde manner, in a blood vessel. At the vertex, where an end of the septum is engaged, a cutting component of the catheter cuts the septum as the catheter is proximally advanced using guide wires as essentially parallel rails. 
     The present invention includes various embodiments. In one aspect, a septotomy catheter is provided that includes a base section; two arms extending from a distal end of the base section; and a cutting component configured to span the two arms. In this aspect, the two arms can each comprise a slot therein, each slot housing a respective end of the cutting component. In this aspect, as an alternative, or in addition to, the two arms, when aligned with their longitudinal axes in parallel, can have an overall cross-sectional diameter no greater than a cross-sectional diameter of the base section; and the two arms, when aligned with their longitudinal axes in parallel, are configured to direct a septum between the arms toward a cutting surface of the cutting component, and the cutting component is configured to cut the septum. In this aspect, as an alternative, or in addition to, a space can exist between the two arms, at the distal end of the base section, between proximal ends of the two arms connected thereto; the cutting component is configured to span the space; and a cutting edge of the cutting component is operational whether the two arms are aligned with their longitudinal axes in parallel, or whether the two arms are separated, pulled apart to form a Y-shape with the base section. 
     In at least one embodiment, a septotomy catheter is provided that includes a base section having a communication lumen therethrough, two movable arms extending from a distal end of the base section, where each arm has a channel therethrough for a passage of a guide wire. With distal ends of the two movable arms separated, the two arms form a Y-shape with the base section. With distal ends of the two movable arms together, the two arms have a longitudinal profile, about a periphery thereof, identical to a longitudinal profile of the base section. The catheter also includes a non-mechanically actuated cutting component residing between the two arms in a vicinity of the distal end of the base section. The cutting component faces distally outward between the two arms with the distal ends of the two movable arms separated. 
     In one or more embodiments, the cutting component spans the two movable arms when the arms are separated. In these embodiments, the cutting component resides perpendicularly to a longitudinal axis of the catheter. 
     In one or more embodiments, the two movable arms each further comprise a notch therein, each notch housing a respective end of the cutting component, each notch providing that the respective end of the cutting component is not exposed outside the catheter when the two arms are separated. With distal ends of the two arms together, the catheter completely houses the cutting component therein, whereby no part of the cutting component is exposed outside the catheter. 
     In one embodiment, the cutting component is an electrode spanning the two movable arms when separated, residing perpendicularly to a longitudinal axis of the catheter. The electrode is energized by radio-frequency (RF) current. The electrode can be a wire, bar, rod, flat sheet, blade or plate. If a flat sheet, plate or blade, the electrode can be entirely insulated except for a most distal portion thereof which is uninsulated. The insulation can be a medical grade epoxy. The uninsulated portion of the flat sheet, plate or blade, along a distal edge thereof, might resemble a wire or rod, or sharpened tip thin blade. The uninsulated portion spans the two movable arms when separated, residing perpendicularly to the longitudinal axis of the catheter. If a flat sheet, plate or blade, the longitudinal, insulated sides would reside inside respective notches of the two arms. 
     The radio-frequency (RF) current can be provided by a wire residing within the communication lumen of the base section. The RF energization can be monopolar or bipolar. 
     In another embodiment, the cutting component of the catheter is laser light generated by an excimer laser. An excimer laser fiber can reside within the communication lumen of the base section. The two bifid arms, with distal ends together, completely house the excimer laser fiber therein, whereby no part of the cutting component is exposed outside the catheter. In this embodiment, if notches are included in the two arms, each notch would house, and/or would be configured to provide unrestrained operation of, and laser light emission from, a distal end of the excimer laser fiber, in a vicinity of the base section, when the two arms are separated. 
     In another embodiment, the cutting component is an ultrasonic cutting blade, having a cutting edge facing distally and spanning the two movable arms when the arms are separated. An ultrasonic static motor can reside within the base section, along the communication lumen thereof. The cutting blade cuts by ultrasound energy and its high frequency vibration can be delivered by a minute piezoelectric ceramic energized through a thin electrical wire passing through the communication lumen of the base section. 
     In still another embodiment, the catheter can further include two base section channels extending through an entirety of the base section. The base section channels are parallel to the communication lumen, with each base section channel communicating with a respective channel of the arm to provide passage of two guide wires, one guide wire per channel, through an entirety of the catheter. 
     A method of treating an aortic dissection is also provided, using an embodiment of the septotomy catheter. The method involves inserting two guide wires into an arterial system. Moving the two guide wires proximally, into a descending aorta, where the two guide wires are substantially parallel to one another and spaced apart a distance. A septum of the aortic dissection is then penetrated, with a first of the two guide wires, into a false lumen of the aortic dissection, distal of a proximal tear of the aortic dissection, at a certain location. At this certain penetration location, the guide wires become more separated from one another. The two guide wires are moved further proximally, toward the proximal tear, with the first guide wire in the false lumen and a second guide wire in a true lumen of the aortic dissection, with septum of the aortic dissection between the two guide wires. The guide wires remain spaced apart, proximal of the certain location of septum penetration, at least the distance or greater; 
     The method then includes inserting a distal end of the septotomy catheter over the guide wires, one guide wire in each of the two channels of the septotomy catheter. The septotomy catheter is moved proximally in the arterial system, with guide wires passing therethrough, toward the aortic dissection, the septotomy catheter tracking the substantially parallel guide wires and remaining closed, with the distal ends of the arms together, completely housing the cutting component therein, whereby no part of the cutting component is exposed outside the catheter. The septum of the aortic dissection is then penetrated with one of the movable arms, into the false lumen thereof, at the certain location, while the one of the movable arms tracks the first guide wire into the false lumen and then proximally thereof and the other of the movable arms tracks the second guide wire proximally in the true lumen. At the certain location, the distal ends of the two movable arms separate, forming a Y-shape with the base section to expose the cutting component outside the catheter, from between the movable arms, with the cutting component facing distally relative to the catheter. The septotomy catheter is moved further proximally, with arms separated. The catheter receives the septum between the separated arms, where the separated arms, with catheter moving proximally, direct a distal end of the septum into the cutting component. The septum is cut a desired distance determined by further proximal movement of the catheter. During the method, the cutting component is energized only upon receipt of the septum between the separated arms, with septum in close proximity to the cutting component. 
    
    
     
       BRIEF DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
       The present invention will be better understood with reference to the following description taken in combination with the drawings. For the purpose of illustration, there are shown in the drawings certain embodiments of the present invention. In the drawings, like numerals indicate like elements throughout. It should be understood, however, that the invention is not limited to the precise arrangements, dimensions, and instruments shown: 
         FIG. 1  illustrates a view of a catheter within a blood vessel (the blood vessel shown in section), the catheter traversing over guidewires and shown in a closed, non-cutting configuration, in accordance with one embodiment of the present invention; 
         FIG. 2  illustrates a view of the catheter of  FIG. 1 , still within the blood vessel and traversing guidewires, now with distal arms opening and separated, while guided by the guide wires, providing that a cutting component within the arms receive and engage an edge end of a septum; 
         FIG. 3  illustrates a cross-section of one embodiment of the catheter of the present invention, where the cutting component is a RF energized electrode, and further showing internal components and operation of the catheter; 
         FIG. 4  illustrates a cross-section of another embodiment of the catheter of the present invention, where the cutting component is a ultrasound energized cutting blade, and further showing internal components and operation of the catheter; 
         FIG. 5  illustrates a cross-section of a Type B aortic dissection, showing guide wire insertion (one guide wire in a true lumen and one guide wire in a false lumen), with an embodiment of the catheter of the present invention traversing over the guidewires, the catheter shown in a closed, non-cutting configuration; 
         FIG. 6  illustrates a cross-section of a Type B aortic dissection, again showing guide wires inserted, with an embodiment of the catheter of the present invention tracking the guidewires, the catheter now with distal arms separated, while guided by the guide wires, revealing a cutting component therein, the arms receiving for cutting a septum of the aortic dissection; 
         FIG. 7  illustrates an alternative feature of a catheter embodiment of the present invention, and further showing (via see-through arm portions) aspects of the present invention; and 
         FIG. 8  illustrates an alternative feature of a catheter embodiment of the present invention, showing flexible wings extending axially from a base section of the catheter, proximal to the cutting component, to assist alignment of the catheter, and the cutting component, within the aorta and toward a center axis of the septum. 
         FIG. 9  illustrates a perspective view of still another embodiment of the catheter of the present invention, where the cutting component is an electrode blade, and distal arms of the catheter each transition from a semi-circular shape in cross-section to a circular shape in cross-section; 
         FIG. 10  illustrates a top view of the embodiment of  FIG. 9 ; 
         FIG. 11  illustrates a cross-section of the top view shown in  FIG. 9 ; 
         FIG. 12  illustrates a blade embodiment of a cutting component of the embodiment of  FIG. 9 ; 
         FIG. 13  illustrates a cross-section of the catheter embodiment of  FIG. 9 , taken at line  13 - 13  in  FIG. 11 ; and 
         FIG. 14  illustrates a cross-sectional side view of the embodiment of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The catheter of the present invention is used for cutting a septum in an aortic dissection, whether acute (where the septum is thin and mobile) or chronic (where the septum is thick and immobile). The catheter can, for instance, be inserted into a dissected aorta in the treatment of Type B thoracic aortic dissections. The figures show the device as described below, and use the same reference numeral for the same element in each drawing. When referring to the catheter of the present invention, an end of the catheter remaining outside the patient is referred to as the proximal end, and an end of the catheter comprising the cutting assembly is referred to as the distal end. When referring to the aortic dissection, the septum thereof, and surgical activity around the septum, an end of the dissection closest to the heart is referred to as the proximal end, and an end furthest from the heart is referred to as the distal end (bottom of page of  FIGS. 5 and 6 ). 
       FIGS. 1 and 2  show a septotomy catheter  10  within a blood vessel, typically an aorta A. The catheter  10  has a base section  12  from which a pair of movable and/or flexible arms (or distal tips, or tips)  14 ,  16  extend. Note that the flexible arms  14 ,  16  could be rigid or semi-rigid, or could have a portion thereof that is rigid or semi-rigid, and a portion that is flexible and/or movable.  FIG. 1  shows the catheter  10  being advanced in the aorta A in a proximal direction, from a femoral artery toward the heart.  FIG. 2  shows the catheter  10  after advancement in the Aorta A and upon separation of the movable arms  14 ,  16  resulting in a distal end of the catheter  10  assuming a general Y-shape.  FIGS. 3 and 4  illustrate embodiments of the catheter  10  in cross-section, better showing internal components and operation of the catheter. 
     Located at a vertex  18  of the catheter  10  is a cutting assembly  20 , formed at the distal end of the base section  12  and the proximal end of the two arms  14 ,  16 . The cutting assembly  20  is preferably non-mechanically actuated (e.g., not micro-scissors, a moving blade, a jigsaw or serrated wires). A septum cutting component  22  of the cutting assembly  20  spans the vertex  18  of the catheter  10 , perpendicular to a longitudinal axis of the catheter  10 . Each end of the septum cutting component  22 , and also a respective adjacent, longitudinal side of the cutting assembly  20  or cutting component  22 , resides inside a notch, slot or trough  24  within each of the two arms  14 ,  16 . The notch  24  provides that the cutting assembly  20 , and particularly the ends (or longitudinal sides) of the septum cutting component  22 , are protected by (e.g., completely enclosed within) the notches  24  and by the two arms  14 ,  16  (as shown in  FIG. 1 ). When open, the arms  14 ,  16  receive the septum S and direct the septum S to the cutting component  22 . The catheter  10  is snugly configured, with each end of the perpendicularly spanning cutting component  22  nestled within the notch  24  of each arm  14 ,  16 , so that the septum S, if abutting an arm  14 ,  16 , during use, is movably directed along the arm to the cutting component  22 . The septum does not snag at the juncture of the cutting component  22  and respective arm  14 ,  16 , due to the direct transition of arm  14 ,  16  to cutting component  22 . Overall, a profile of the closed, cutting end of the catheter  10  (i.e., the distal end of the catheter  10 , including the two arms  14 ,  16  and the vertex  18 ) has the same profile as the remaining base section  12  of the catheter  10  (as shown in  FIG. 1 ). 
     In one embodiment, the cutting assembly  20  is radio-frequency (RF) energized, and the septum cutting component  22  is an electrode. The electrode can be a wire, bar, rod, sheet, blade or plate. If a conductive sheet or plate, much of the sheet or plate can be insulated (except for a most distal portion thereof). A remaining, uninsulated portion of the electrode would likely resemble a wire, bar or rod spanning the vertex  18  of the catheter  10 , perpendicular to the longitudinal axis of the catheter  10 . In this instance, longitudinal sides of the sheet or plate would reside inside the notch or trough  24  within each of the two arms  14 ,  16 . 
     The RF energization can be monopolar or bipolar. In monopolar use, the active electrode  22  is placed at the cutting site, and a return electrode pad is attached to the patient (not shown). High frequency electrical current flows from a generator (not shown), to the electrode  22 , through to target tissue, to the patient return pad, and back to the generator. The catheter  10  includes a communication lumen  26  for the traversing therethrough of a RF current wire  28  (as shown in  FIG. 3 ). In a bipolar embodiment, usually lower voltages are employed, thereby less energy is required. A return electrode or pad must therefore be much closer to the active electrode, and to the cutting site. RF current is restricted to tissue between the active and return electrodes, thereby giving better control over the targeted area and preventing possible current damage to surrounding sensitive tissue. 
     In another embodiment, the cutting assembly  20  employs an ultrasonic static motor  30  and the septum cutting component  22  is an ultrasonic cutting blade (as shown in  FIG. 4 ). The ultrasonic motor  30  can take the form of a piezoelectric device (ceramic PTZ disks) connected to cutting component  22 , energized through a thin conductor (wire) imbedded in the catheter that delivers electric current. The ultrasonic motor  30  is preferably housed within base section  2 . The ultrasonic static motor transforms electrical voltage into high-frequency (approximately 50,000 Hertz) vibration, and the vibration is transmitted to the cutting component  22  and causes the blade to cut through the septum on contact. 
     In still another embodiment, the cutting assembly  20  employs an excimer laser (or exciplex laser), where the septum cutting component  22  is the generated laser light in the ultraviolet range (not shown). The excimer laser fiber travels through the communication lumen  26  of the catheter  10 . The high-power ultraviolet output of excimer lasers are useful and efficient for delicate surgeries, as the laser can make clean, precise cuts in tissue. 
     As better illustrated in  FIGS. 3 and 4 , but also shown in  FIGS. 1 and 2 , a pair of guide wires  32  traverse the catheter  10  through channels  34 , one guide wire  32  per channel  34 . Each guide wire  32  passes through a respective channel  34  in the base section  12  and then separate, with one guide wire  32  traversing through one channel  34  in each of the arms  14 ,  16 . Preferably, the guide wires  32  traverse channels  34  of the catheter  10  linearly, proximally to distally (relative to the catheter) in a single direction (i.e., no looping or doubling back). 
       FIGS. 5 and 6  illustrate a cross-section of a Type B aortic dissection, a method of treating aortic dissection, a method for septum cutting, and for use of the catheter  10 . Shown are an ascending aorta AA, descending aorta DA, femoral artery FA, renal arteries RA, septum S, proximal tear PT, true lumen TL, and false lumen FL. When referring to the aortic dissection, the septum S thereof, and surgical activity involving the septum S, an end of the dissection closest to the heart is referred to as the proximal end, and an end furthest from the heart is referred to as the distal end (bottom of page). 
     Now referring to  FIGS. 5 and 6 , the guide wires  32  are first inserted into the blood vessel, at the femoral artery, and advanced in a proximal direction, along the aorta A, toward a point of aortic dissection. Since the guide wires  32  are constrained by the blood vessel walls A, the guide wires  32  are roughly parallel to each other, and parallel to the axis of the blood vessel. Upon reaching a point of aortic dissection, one guide wire  32  is inserted (penetrated) through a septum S of the aortic dissection, into a false lumen FL thereof. The other guide wire  32  is equally advanced, but remains in a true lumen TL of the aorta (alongside the dissection). 
     Thus, both guide wires  32  have entered the femoral artery FA through the same puncture or through an introducer sheath inserted into the artery. Both guidewires  32  are fully advanced within the aorta A to a final location, with one guide wire  32  inserted through the septum S into the false lumen FL and one guide wire  32  in the true lumen TL. A final location of the guide wires  32  extend beyond a point where a cutting of the septum will cease (with one guide wire  32  on each side of the septum S along the dissection). The proximal ends of the guidewires  32 , remaining outside the body, are then fed into the channel(s)  34  at a distal end of the catheter  10 . The catheter  10  is inserted in the sheath and pushed along the vessel, tracking and moving along (over) the guide wires  32 , as the guide wires  32  pass through the channels  34 . As the catheter  10  is advanced within the aorta A, along the parallel guide wires  18 , prior to reaching the aortic dissection, the catheter  10  remains in a closed, non-cutting configuration, with cutting component  22  non-exposed (as shown in  FIGS. 1 and 5 ). Shortly, the catheter  10  approaches a distal end of the septum S of the aortic dissection, at the point where one guide wire  18  penetrates through the septum S. 
     The arms  14 ,  16  of the catheter  10  do not diverge into a Y-shape (and thus revealing the cutting component  22 ) until the guide wires  32  separate at the lower edge (distal end) of the septum S (at the point where one guide wire  18  penetrates through the septum S) As shown in  FIG. 6 , the catheter  10  tracks the guide wires  32 , the arms  14 ,  16  separate, forming a Y-shape, with one arm  14  disposed in the true lumen TL and another arm  16  disposed in the false lumen FL. The septum S is now located between the arms  14 ,  16 , and is directed by the arms  14 ,  16  into the cutting component  22  while the catheter  10  is continually advanced toward the heart (in a proximal direction relative to the dissection). 
     Referring to  FIG. 6 , as the catheter  10  continues proximal advancement (by continually tracking the guide wires  32  previously placed in the aorta A), the cutting component  22  proximally moves and cuts along the length of septum S. The catheter  10  follows the guide wires  32 , thereby directing the path (and the opening and closing) of the arms  14 ,  16 . When open, the arms  14 ,  16  receive the septum S and direct the septum S to the cutting component  22 . In all embodiments, the catheter  10  is snugly configured, with each end of the cutting component  22  nestled within the notch  24  of each arm  14 ,  16 , so that the septum S, if abutting an arm  14 ,  16 , is movably directed along the arm to the cutting component  22 . The septum does not snag at the juncture of the cutting component  22  and respective arm  14 ,  16 . 
     As noted, acute aortic dissections often require only a few centimeters of septum division to equalize pressure between the lumens, and to provide low resistance outflow of both lumens to avoid development of aneurysmal dilatation of the false lumen (e.g., 5-15 cm in the instance of cutting from the level of the aortic bifurcation to below the renal arteries).  FIGS. 5 and 6  illustrate an instance of aortic dissection where guide wire  32  penetration of the septum S occurs, generally, at the femoral or external iliac level C 1  (i.e., cutting start point C 1 ). Cutting of the septum S begins at point C 1  and ceases below the renal arteries RA, at C 2  (i.e., cutting end point C 2 ). In chronic dissections, where different viscera may be perfused by either lumen, septum cutting is needed to convert the double lumen into a single one, and cutting the fibrous septum may be required to the proximal tear PT. 
     After a suitable length of septum S cutting is complete, the cutting component is de-energized, and the catheter  10  is withdrawn, in a distal direction, from the blood vessel. Any remaining septum S is undisturbed. As noted, the methods and device of the present invention teach septum S cutting in a retrograde manner (from distal to proximal along the aortic dissection), which is the only safe, effective way to divide the septum S. Dividing a septum from a proximal to distal point, by pulling or retraction of a catheter device, may result in sudden collapse of the true lumen, sometimes with catastrophic consequences. 
       FIG. 7  illustrates an alternative embodiment of the catheter  10 , where each of the guide wires  32  extend and traverse through a longitudinal channel  34  residing only in a respective arm  14 ,  16 . To better illustrate this alternative feature, and other features within the arms  14 ,  16 ,  FIG. 7  provides see-through capability of the arms  14 ,  16  of the catheter  10 . 
     In the  FIG. 7  embodiment, each channel  34  (and therefore each guide wire  32  during catheter use) exits the respective arm  14 ,  16  at a proximal end  36  thereof, in a vicinity of the cutting component  22 . The guide wires  32  are thereafter located exterior to the catheter  10 , alongside and parallel to the base section  2 . The channel  34  of this alternative embodiment may exit the proximal end  36  of the arm  14 ,  16  at a location longitudinally distal to the cutting component  22 , longitudinally proximal to the cutting component  22 , and/or at an angle relative to the longitudinal axis of the catheter  10 , to ensure that the catheter  10 , when in a closed, non-cutting configuration (with cutting component  22  non-exposed), has arms  14 ,  16  completely abutting one another (similar to that shown in  FIG. 1 ). 
       FIG. 7  also illustrates respective notches  24  in each arm  14 ,  16  of the catheter  10 , showing well-defined longitudinal wells or troughs that house a respective end of each cutting component  22 , and that house respective sides of each cutting component  22  (or that house insulated portions of the cutting component, or that house and insulate wires feeding an electrode cutting component  22 , all comprised within the cutting assembly  20 ). 
       FIG. 8  illustrates another alternative feature of the catheter  10 . A distal end of the catheter  10  can include one or more flexible wings  40 , preferably small, on an outer aspect of the base section  12 , proximal to the cutting assembly  20 , to better align the catheter  10 , and the cutting component  22 , within the aorta A and toward a center axis of the septum S. Further, and preferably smaller, flexible wings  40  could extend from the arms  14 ,  16 . The flexible wings  40  may have a fixed shape, or may be collapsible, providing that the wings  40  can be carried on or inside the catheter  10  until the diameter of the lumen into which the catheter  10  is advanced permits its passive extending (or un-flexing). The flexible wings  40 , illustrated in  FIG. 8 , form of a loop made of the material similar to that of the catheter  10 . This alternative feature can be used when the catheter  10  is introduced into the blood vessel by insertion through a hollow outer catheter, introducer element, or similar body. In this instance, when the catheter  10  protrudes from the introducer element, the flexible wings  40  expand (open or axially extend). When the catheter  10  is withdrawn from the blood vessel, back into the introducer element, the wings  40  would fold forward onto the outer walls of the base section  12  or the arms  14 ,  16 . 
       FIGS. 9-14  illustrate a further alternative embodiment of the catheter  10 , having a differently shaped distal end portion, and where the distal end portion of the catheter  10  comprises two or three sections.  FIG. 9  illustrates a perspective view of the catheter  10 ;  FIG. 10  a top view;  FIG. 11  a cross-sectional top view;  FIG. 12  illustrates a blade embodiment of the cutting component  22 ;  FIG. 13  is a cross-sectional view of the catheter taken at line  13 - 13  in  FIG. 11 ; and  FIG. 14  is a cross-sectional side view. 
     In this illustrated embodiment, a distal end portion  50  comprises three sections. A proximal most distal end section  52  is circular in cross-section, but could comprise an oval or other shape in cross-section. A middle distal end section  54  comprises, at a proximal end thereof, two semi-circular portions in cross-section that each distally transition (taper) into a shape of a distal most distal end section  56 . The distal most distal end section  56  comprises two portions, or channels, which can have various shapes in cross-section. As illustrated, the two semi-circular portions in cross-section (of the middle distal end section  54 ) each distally transition (taper) into a circular portion in cross-section which extend into the distal most distal end section  56  (distal tips). As illustrated, the distal most distal end section  56  comprises two channels having a rounded, or circular, shape in cross-section, but each could comprise an oval or other shape. The distal end portion  50  can be injection molded. Any of the three sections of the distal end portion  50  (but, primarily, the distal most distal end section  56 ) can be made radiopaque, for example, with an addition of barium filler to the catheter materials. Or, any of the desired sections of the distal end portion  50  can be marked with traces, bands, rings, or ink that is radiopaque, such as gold, silver, platinum, iridium or tungsten. 
     In this embodiment, the cutting component  22  is an electrode blade. The blade is partially located within the proximal most distal end section  52  and the middle distal end section  54 . The cutting component  22  resides within a slot  24  (rectangular in cross-section) in the proximal most distal end section  52  (see  FIG. 13 ), which may resemble a notch, slot or trough  24  within each of the individual arms  14 ,  16  of the middle distal end section  54 . The slot  24  could take other shapes, and/or could extend to (and be open through) an outer perimeter of the catheter  10 . 
     The cutting component  22  preferably has a cutting surface (at a distal end thereof) that is perpendicular to a longitudinal axis of the catheter  10 . Each end of the cutting surface, and each adjacent longitudinal side of the cutting component  22 , resides inside the slot, notch or trough  24 . The slot  24  provides that the non-cutting ends and sides of the cutting component  22  are protected by (e.g., completely enclosed within) the notches  24  whether or not the two arms  14 ,  16  are straight (at rest) or separated (pulled apart to form a Y-shape with the base section  12 ). 
     In the middle distal end section  54 , the two, semi-circular cross-sectional portions do not comprise, in a total circular diameter, an entirety of the total circular diameter of the cross-section of the proximal most distal end section  52 . In view of this, a rectangular reveal  57  (or space) is located between the two semi-circular portions of the middle distal end section  54  (see, particularly,  FIG. 13 ). Accordingly, in this embodiment, the flexible (movable) arms  14 ,  16  do not require opening (or spreading apart to form a Y-shape with the base section  12 ) to expose at least a portion of the cutting component  22 . Note that the arms  14 ,  16  (i.e., the middle distal end section  54  and the distal most distal end section  56 ) could also be rigid or semi-rigid, or have a portion thereof that is rigid or semi-rigid, and a portion thereof that is flexible and/or movable. 
     As can be appreciated from  FIG. 10 , in this embodiment, with the arms  14 ,  16  remaining straight (i.e., in an at rest position, where a longitudinal axis of each arm  14 ,  16  is generally aligned with a longitudinal axis of the base section  12 ), a septum S can be located between the arms  14 ,  16 , and be directed by the arms  14 ,  16  into the cutting component  22  while the catheter  10  is continually advanced toward the heart. In this embodiment, therefore, the catheter is in a cutting position (is operational), with at least a portion of the cutting component  22  exposed between the arms  14 ,  16 , while no portion of the arms  14 ,  16  extend (or are spread) radially a distance greater than a diameter of the base section  12 . Accordingly, in this embodiment, the two arms, when aligned with their longitudinal axes in parallel, have an overall cross-sectional diameter no greater than a cross-sectional diameter of the base section. In other words, the two arms  14 ,  16 , when aligned with their longitudinal axes in parallel, have outer perimeters spaced apart a distance no greater than a cross-sectional diameter of the base section. 
       FIG. 12  illustrates a cutting component  22  of the present embodiment. In  FIG. 12 , a blade (electrode) is shown welded to an electrode trace  28 . The blade  22  and trace  28  can be  304  stainless steel. A most distal edge  23  of the blade is the cutting edge, or cutting portion, of the cutting component  22 . The cutting edge  23  can be beveled, as shown in  FIG. 12 . Ends  25  of the cutting portion  23  of the cutting component  22  can be housed within the slots  24  of the two arms  14 ,  16 . Where the cutting component  22  is in the form of an electrode blade, sides  27  of the blade can also remain housed within the slots  24  of the two arms  14 ,  16 . 
     The blade  22  and at least a portion of the electrode trace  28  can be coated (or insulated). The most distal edge  23  (cutting portion) of the blade remains uncoated (or is masked during the coating process to remain uncoated). 
     As detailed above,  FIG. 13  illustrates the two, semi-circular portions of the two arms  14 ,  16  have their flat, adjacently aligned sides separated by the reveal (or space)  57 . A portion of the cutting component  22  spans the reveal  57  while portions of the cutting component reside within the slots  24  of each of the two arms  14 ,  16 .  FIG. 13  also illustrates that the two guidewire channels  34 , in this embodiment, are located on one side of center of the catheter  10 , in cross-section, while the cutting component is located on the other side of center of the catheter  10 . That is, looking at a cross-section of the catheter  10  ( FIG. 13 ), the guidewire channels  34  are located in one hemisphere, and the cutting component  22  and communication lumen  26  are located in a second hemisphere. Finally, adjacent to the slot  24  of the cutting component,  FIG. 13  illustrates an adjacent crescent, or D-shaped, cavity  59 . The cavity  59  exists for distal end portion  50  molding purposes, and is not essential for catheter  10  use.  FIG. 11  shows that the cavity  59  does not extend distally to a distal end of the proximal most distal end section  52 . 
       FIG. 14  illustrates a cross-sectional side view of the  FIG. 9  embodiment.  FIG. 14  also illustrates that the two guidewire channels  34 , in this embodiment, are located on one side of center of the catheter  10 , in cross-section, while the cutting component is located on the other side of center of the catheter  10 . In  FIG. 14 , the guidewire channels  34  are seen on a left side of the catheter  10  (one hemisphere), and the cutting component  22  and communication lumen  26  are seen on a right side of the catheter  10  (a second hemisphere). Also,  FIG. 14  illustrates the crescent, or D-shaped, cavity  59 , the location thereof, and that the cavity  59  does not extend distally to a distal end of the proximal most distal end section  52 . 
     In one aspect of this embodiment, the catheter body  12  is 14 Fr. The two guidewire channels  34  are sized for 0.035″ or smaller guidewires, and the single communication lumen  26  houses the electrode trace  28 . The coated blade  22  and trace  28  ensure energy density. Use of the  FIGS. 9-14  embodiment of the catheter  10 , and guidewire advancement through the catheter  10 , is similar to the detailed descriptions provided above for the other catheter  10  embodiments. However, as just noted above in paragraphs [0064] and [0065], in the  FIGS. 9-14  embodiment of the catheter  10 , the arms  14 ,  16  (whether flexible, movable, rigid, semi-rigid, or a combination thereof) do not require opening (or a spreading apart to form a Y-shape with the base section  12 ) to expose at least a portion of the cutting component  22 . Accordingly, with the arms  14 ,  16  remaining straight (i.e., where a longitudinal axis of each arm  14 ,  16  is generally aligned with a longitudinal axis of the base section  12 ), a septum S can be located between the arms  14 ,  16 , and be directed by the arms  14 ,  16  into the cutting component  22  while the catheter  10  is continually advanced toward the heart. 
     These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. Accordingly, it will be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. For example, features detailed as included in certain specific embodiments above are recognized as interchangeable and possibly included in other detailed embodiments. Specific dimensions of any particular embodiment are described for illustration purposes only. It should therefore be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention.