Patent Publication Number: US-2020289796-A1

Title: Transseptal Puncture Apparatus and Method for Using the Same

Description:
RELATED U.S. PATENT DOCUMENTS 
     This application claims pursuant to 35 USC 120 priority to, the benefit of and is a divisional application of U.S. Patent application Ser. No. 15/811,080, filed on Nov. 13, 2017, which is in turn a divisional application of U.S. Pat. No. 9,821,145 and which is incorporated herein in its entirety by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention generally relates to a device for performing an intracardiac transseptal puncture procedure. 
     BACKGROUND OF THE INVENTION 
     Septal puncture through an intact atrial septum from the right atrium to the left atrium is often necessary. This is traditionally performed using rigid, long needles, such as Brockenbrough or Ross needles. In all types of septal puncture, the needle that is used to puncture the atrial septum poses a high risk of inadvertent puncture through tissue other than the septum primum, for example, the atrial free wall, posing a significant risk to the patient. For patent foramen ovale (PFO) closure, this risk is potentially even higher, due to the fact that the septal tissue is defective and often thinning, and may stretch an even greater amount during the puncture procedure, bringing the tip of the needle dangerously close to the atrial free wall or the left atrial appendage. 
     The currently offered SafeSept® Transseptal Guidewire by Pressure Products Medical Supplies Inc. provides a sharp but atraumatic curved guidewire that is fed through a sharp transseptal needle disposed within an introducer. The introducer includes an outer sheath and a tapered dilator which telescopes out of the sheath. The transseptal needle in turn is disposed into the dilator. The tapered dilator is used to tent the septum without the needle extending beyond the distal tip of the tapered dilator, the sharp guidewire is advanced out of the dilator to penetrate the septum as its column is supported by the needle. Because of the columnar support, the guidewire is able to penetrate the septum without bending or buckling the otherwise flexible guidewire. Without such columnar support, the guidewire would not have the columnar strength to be pushed through the septum. Once the guidewire has penetrated the septum, the sharp needle is advanced out of the dilator over the guidewire through the septum into the left atrium. The dilator is advanced over the needle, then the sheath is advanced over the dilator into the left atrium. With the sheath safely in place, the tapered dilator, needle, and guidewire are removed so that a catheter or other cardiac instrument may be introduced into the left atrium through the sheath. 
     In the SafeSept® Transseptal Guidewire Needle Free produced by Pressure Products the method of septal penetration is the same as with the SafeSept® Transseptal Guidewire, but no transseptal needle is provided. Only the atraumatic sharp guidewire is used to penetrate the septum and the tapered dilator is advanced over the guidewire into the left atrium. Because no needle is employed, it is possible that both the tapered dilator and sheath may be able to be advanced through the septum by the use of an oscillating rotation of the tapered dilator and/or sheath as it is being advanced. 
     SUMMARY OF THE INVENTION 
     The illustrated embodiments include a transseptal instrument for accessing a cardiac septal wall within a heart which includes a flexible introducer having an interior lumen, a distal curve, and a distal taper; and a cannula having an interior lumen, a distal curve, and a distal blunt end, the cannula being telescopically disposed into the flexible introducer. The flexible introducer has insufficient columnar strength and unsuitable shape for accessing a predetermined location on the cardiac septal wall when the cannula is not disposed within the interior lumen of the introducer and in close proximity to the distal taper thereof, but is able to access the predetermined location on the cardiac septal wall when the cannula is disposed within the interior lumen of the introducer and in close proximity to the distal taper thereof. 
     The flexible introducer includes a blunt tapered end outer sheath and a blunt tapered end dilator telescopically disposed in the outer sheath. Throughout the balance of this specification, reference shall be made to a blunt needle, although the term blunt dilator could be applied with equal accuracy in cases where only one of the two components is used. Therefore, wherever below “blunt needle” is used, it should be understood that a “blunt dilator” could be used instead. 
     In one embodiment the cannula is nontapered and is nonextendable beyond the distal taper of the introducer. 
     In another embodiment the cannula is tapered and is nonextendable beyond the distal taper of the introducer. 
     In another embodiment the cannula is tapered or necked down and is extendable beyond of the distal taper of the introducer. 
     In another embodiment the cannula is nontapered or necked down and is extendable beyond of the distal taper of the introducer. 
     The transseptal instrument further includes a sharp end floppy guidewire telescopically disposed within the interior lumen of the cannula. The guidewire is prebiased to assume an atraumatic configuration when unsupported, but has sufficient columnar strength when supported to be capable of being pushed through a tough fibrous septal wall. 
     In one embodiment the guidewire when first extended beyond the distal blunt end of the cannula is supported by the cannula. 
     In another embodiment the guidewire when first extended beyond the distal taper of the introducer is supported by the cannula and/or distal taper of the introducer. 
     The illustrated embodiments thus include a transseptal instrument for accessing a cardiac septal wall within a heart which includes a flexible introducer having an interior lumen, a distal curve, and a distal taper; a proximal hub; a valve included within the hub; and a cannula coupled to the proximal hub and valve, the cannula having an interior lumen, a distal curve, and a distal blunt end. The cannula is telescopically disposed into a flexible introducer. The introducer has an interior lumen with a first proximal lumen inner diameter and a second smaller distal lumen inner diameter, a distal curve, and a distal taper. The distal blunt end of the cannula is able to pass through the first proximal lumen diameter but not though the second smaller distal lumen diameter of the introducer. The flexible introducer is characterized by insufficient columnar strength and unsuitable curve shape to access the cardiac septal wall unless the cannula is disposed within the lumen having the first proximal lumen inner diameter. 
     The flexible introducer includes a blunt end outer sheath having the first proximal lumen inner diameter, and a blunt end tapered dilator telescopically disposed in the outer sheath having the second smaller distal lumen inner diameter. 
     The transseptal instrument further includes a sharp end floppy guidewire telescopically disposed within the interior lumen of the cannula, the guidewire being prebiased to assume an atraumatic configuration when unsupported, but to have sufficient columnar strength when supported to be capable of being pushed through the septal wall. 
     The guidewire when first extended beyond the distal blunt end of the cannula is supported by the cannula. 
     The guidewire when first extended beyond the distal taper of the introducer is supported by the cannula and/or distal taper of the introducer. 
     The illustrated embodiments are thus also understood to include a transseptal instrument for accessing a cardiac septal wall within a heart which includes a flexible introducer having an interior lumen, a distal curve, and a distal taper; a proximal hub; a valve included within the hub; and a cannula coupled to a proximal hub and valve, the cannula having an interior lumen, a distal curve, and a distal blunt end. The cannula is telescopically disposed into the flexible introducer. The introducer has a stepped interior lumen with a first proximal lumen inner diameter and a second smaller distal lumen inner diameter, or an interior lumen having a tapered inner diameter. The introducer also has a distal curve, and an exterior distal taper. The distal blunt end cannula is stepped or distally tapered so as to be able to pass through the first proximal lumen diameter and the second smaller distal lumen diameter of the introducer to extend beyond the distal taper of the introducer or beyond the portion of the interior lumen having a tapered inner diameter. The flexible introducer is characterized by insufficient columnar strength and unsuitable curve shape to access the cardiac septal wall unless the cannula is disposed within the lumen having the first proximal lumen inner diameter or possibly within the interior lumen having a tapered inner diameter. 
     The flexible introducer includes a blunt taper end outer sheath having the first proximal lumen inner diameter, and a blunt tapered end dilator telescopically disposed in the outer sheath and having the second smaller distal lumen inner diameter or having the interior lumen with a tapered inner diameter. 
     The transseptal instrument further includes a sharp end floppy guidewire telescopically disposed within the interior lumen of the cannula, the guidewire being prebiased to assume an atraumatic configuration when unsupported, but to have sufficient columnar strength when supported to be capable of being pushed through the septal wall. 
     The guidewire when first extended beyond the distal blunt end of the cannula is supported by the cannula. 
     The guidewire when first extended beyond the exterior distal taper of the introducer is supported by the cannula and/or the interior lumen having a tapered inner diameter. 
     The illustrated embodiments of the invention further extend to a method including the steps of: telescopically disposing a blunt end cannula into a flexible introducer having an interior lumen, a distal curve, and a distal taper to define a predetermined shape and steerability to at least a distal portion of the introducer, where the flexible introducer has insufficient columnar strength and unsuitable shape for accessing a selected location on the cardiac septal wall when the cannula is not disposed within the interior lumen of the introducer and in close proximity to the distal taper thereof, but is able to access the predetermined location on the cardiac septal wall when the cannula is disposed within the interior lumen of the introducer and in close proximity to the distal taper thereof; intravascularly accessing a right atrium of a patient&#39;s heart with the introducer; steering the distal taper of the introducer to the selected location on a septal wall of the heart to tent the septal wall at the selected location; advancing a sharp ended floppy guidewire telescopically disposed within an interior lumen of the cannula while being supported by the cannula to provide sufficient columnar strength to the floppy guidewire to allow it to be pushed through the septal wall into a left atrium of the patient&#39;s heart; and advancing the sharp ended floppy guidewire beyond any support by the cannula to configure the sharp ended floppy guidewire into a prebiased atraumatic shape. 
     The method further includes the step of advancing the cannula through the septal wall over the guidewire. 
     The method further includes advancing the introducer through the septal wall over the cannula. 
     The method further includes advancing the introducer through the septal wall over the guidewire while leaving the cannula telescopically retained in the introducer. 
     In one aspect, the invention relates to a device for puncturing the atrial septum of a patient. In one embodiment of the invention, the device includes an outer needle with a blunt distal end and a lumen longitudinally defined therethrough and a guidewire axially disposed in the lumen of the needle. In one embodiment, the guidewire has a proximal portion, an intermediate portion, and a distal portion, wherein the intermediate portion is more flexible than either the proximal portion or the distal portion of the guidewire. 
     In an embodiment, the intermediate portion is a segment that is approximately 20 mm from the distal end of the guidewire. The intermediate portion may be, for example, 3 mm in length. In an embodiment, the intermediate portion has a waist. The waist of the intermediate portion is, for example, about 0.2 mm in diameter. In a particular embodiment, the intermediate portion of the guidewire may be made of a polymer. 
     In another embodiment, the guidewire has a distal portion and a proximal portion, wherein the distal portion is more flexible than the proximal portion. In another embodiment, the guidewire is flexible in both the distal portion and the proximal portion (e.g., has homogeneous flexibility). 
     As another feature, the distal portion of the guidewire has a distal portion that deviates from the linear path of the guidewire such as, for example, a taper, a bend, a curve, a cork screw or a hook. In a particular embodiment, the tip of the guidewire is turned inward during the delivery procedure to avoid the risk of inadvertent puncture of tissue. In another embodiment, the guidewire contains a portion that has a different thickness or diameter than the rest of the guidewire such as, for example, a tapered portion, whereby the guidewire is tapered from one thickness to another. 
     In an embodiment, the distal portion of the cannula is more flexible than the proximal portion of the cannula. 
     In still another embodiment, the device includes a cannula with a blunt distal end and a lumen axially disposed therethrough and a pump for introducing a high pressure jet spray through the lumen of the cannula. 
     In a further embodiment of the invention, the device has a cannula with a blunt distal end and an insulating material for insulating the length of the proximal and intermediate portion, leaving the distal tip of the cannula uninsulated. As an additional feature, the device may include unipolar electrodes or, alternatively, the device may include bipolar electrodes. 
     In another aspect, the invention provides a method for puncturing the atrial septum of a patient&#39;s heart by accessing the right atrium via a vessel. The method includes introducing into the right atrium a transseptal puncture device that includes a cannula with a blunt distal end and a lumen longitudinally defined therethrough and a guidewire axially disposed in the lumen of the cannula, the guidewire having a proximal portion, a distal portion, and an intermediate portion that is more flexible than the proximal portion or the distal portion. The blunt needle is contacted with the atrial septum and the guidewire is pushed through the septum in advance of the blunt needle. A delivery sheath is then positioned using a standard catheterization laboratory technique in the left atrium and the transseptal puncture device is withdrawn from the patient&#39;s body. 
     In another aspect, the invention provides a method for puncturing the atrial septum of a patient&#39;s heart by accessing the right atrium via a vessel. The method includes introducing into the right atrium a transseptal puncture device that includes a blunt needle with a blunt distal end and a lumen longitudinally disposed therethrough and a guidewire axially disposed in the lumen of the blunt needle, the guidewire having a proximal portion and a distal portion, wherein the distal portion is more flexible than the proximal portion. The blunt, needle is first contacted with the atrial septum. The guidewire is then pushed through the septum in advance of the blunt needle. A delivery sheath is positioned in the left atrium and the transseptal puncture device is withdrawn from the patient&#39;s body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like reference numbers generally refer to the same parts throughout the different, views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. 
         FIG. 1  is a plan view of a transseptal puncture device according to an illustrative embodiment of the invention. 
         FIG. 2  is a longitudinal plan view of the distal end of a transseptal puncture device according to an illustrative embodiment of the invention. 
         FIG. 3  is a cross sectional view of the distal end of a transseptal puncture device taken along lines  3 - 3  in  FIG. 2 . 
         FIG. 4A  is a longitudinal view of the distal end of a guidewire of a transseptal puncture device according to an illustrative embodiment of the invention in which the intermediate portion contains a waist. 
         FIG. 4B  is an exploded view of the intermediate portion of  FIG. 4A . 
         FIG. 5  is a longitudinal view of the distal end of a guidewire of a transseptal puncture device according to another illustrative embodiment of the invention in which the guidewire has a tapered intermediate portion. 
         FIG. 6  is a longitudinal view of the distal end of a guidewire of a transseptal puncture device according to another illustrative embodiment of the invention, in which the guidewire has an intermediate portion. 
         FIG. 7  is a longitudinal view of the distal end of a guidewire of a transseptal puncture device according to another illustrative embodiment of the invention in which the distal tip of the guidewire is bent. 
         FIG. 8  is a longitudinal view of the distal end of a guidewire of a transseptal puncture device according to another illustrative embodiment of the invention in which the distal end of the guidewire has a hook. 
         FIG. 9 a -9 g    depicts the steps in an illustrative method for puncturing an atrial septum with an illustrative transseptal puncture device according to the invention. 
         FIG. 10  is a fragmented illustration of a septal puncture apparatus according to an illustrative embodiment of the invention. 
         FIG. 11  is a schematic side view of a portion of a septal puncture apparatus including, a set of flexible members according to an illustrative embodiment of the invention. 
         FIG. 12A  is a schematic side view of a portion of an embodiment of a septal puncture apparatus including a set of flexible members partially extended from an elongate member. 
         FIG. 12B  is a schematic side view of the flexible members of  FIG. 12A  fully extended from the opening in the elongate member. 
         FIG. 13  is a schematic side view of another embodiment of a set of flexible members according to the invention. 
         FIG. 14A  is a schematic side view of an embodiment of a flexible member according to the invention. 
         FIG. 14B  is a schematic end-on view of the flexible member of  FIG. 14A . 
         FIG. 15A  is a schematic side view of an embodiment of a flexible member according to the invention. 
         FIG. 15B  is a schematic end-on view of the flexible member of  FIG. 15A . 
         FIG. 16A  is a schematic side view of an embodiment of a set of flexible members, a cutting member, and an elongate member of a portion of a septal puncture apparatus according to the invention. 
         FIG. 16B  is an illustration of the set of flexible members and the cutting member extended out of the elongate member of  FIG. 16A . 
         FIG. 17  is a partially broken-away view of a heart depicting a portion of a septal puncture apparatus, according to the invention, on a second side of the septal wall. 
         FIG. 18A  is a cross-sectional view of a septal wall of a heart depicting a set of flexible members located outside an opening in an end of an elongate member, according to an illustrative embodiment of the invention. 
         FIG. 18B  is a cross-sectional view of the flexible members of  FIG. 19A  in which a portion of the flexible members is located in contact with a first side of a septal wall and another portion of the flexible members is located in proximity to a second side of the septal wall. 
         FIG. 18C  is a cross-sectional view of the flexible members of  FIGS. 19A and 19B  in which a cutting member is extended from a lumen in the delivery member creating a hole through the septal wall. 
         FIG. 19  is a schematic side view of a flexible member, a cutting member, and an elongate member according to an illustrative embodiment of the invention. 
         FIGS. 20 a -20 d    are overall side views of the blunt, end cannula assembly with necked down distal portion of the improved embodiments.  FIG. 20 a    is a side plan view of the assembly with the distal insert showing the blunt end of the cannula in  FIG. 20 e    and the proximal inset showing the plan side view of the cannula valve and hub in  FIG. 20 b   . A side cross sectional view of the hub and assembly is depicted in  FIG. 20 c    with the proximal inset showing the hub with the valve in the open configuration in  FIG. 20   d.    
         FIGS. 21 a -21 d    are overall side views of the blunt end cannula assembly of the improved embodiments.  FIG. 21 a    is a side plan view of the assembly with the distal insert showing the blunt end of the cannula in  FIG. 21 e    and the proximal inset showing the plan side view of the valve and hub in  FIG. 21 b   . A side cross sectional view of the hub and assembly is depicted in  FIG. 21 c    with the proximal inset showing the hub with the valve in the open configuration in  FIG. 21   d.    
         FIG. 22  is a side cross sectional view of the introducer assembly in enlarged scale showing the blunt end dilator extending from the end of the introducer sheath and the cannula and guidewire disposed in the dilator in a more proximal position. 
         FIG. 23  shows the distal portion of the introducer assembly of  FIG. 22  in which the cannula has been advanced to a distal internal stop in the dilator carrying the sharp tip guidewire with it. 
         FIG. 24  is a side cross sectional view of the introducer assembly in enlarged scale showing the blunt end dilator extending from the end of the introducer sheath and the cannula and guidewire disposed in the dilator in a more proximal position in the embodiment where the cannula has a stepped-down outer diameter which will allow it to extend past the internal distal stop in the blunt end dilator. 
         FIG. 25  shows the distal portion of the introducer assembly of  FIG. 24  in which the cannula has been advanced past the distal internal stop in the dilator, extending from the distal end the blunt end dilator and carrying the sharp tip guidewire within it. 
         FIG. 26  shows the curved introducer assembly in the configuration of  FIG. 22  within the atrium of the heart with the blunt end dilator at or near a lower point on the septal wall distant from the target location at which septal penetration is desired. 
         FIG. 27  shows the introducer assembly of  FIG. 26  in which the cannula carrying the guidewire has been advanced until the distal end of the cannula meets the internal distal stop in the blunt end dilator, showing how the cannula gives a predetermined desired shape to the introducer assembly to bring the blunt end dilator to the desired position on the septal wall where penetration is desired. 
         FIG. 28  is a side cross sectional view of the introducer assembly of  FIG. 24  showing the blunt end dilator extending from the end of the introducer sheath and the cannula and guidewire disposed in the dilator in a more proximal position in the embodiment where the cannula has a stepped-down outer diameter which will allow it to extend past the internal distal stop in the blunt end dilator. 
         FIG. 29  shows the introducer assembly of  FIG. 28  in which the stepped-down cannula carrying the guidewire has been advanced through the internal distal stop in the blunt end dilator, showing how the cannula gives a predetermined desired shape to the introducer assembly to bring the blunt end cannula to the desired position on the septal wall where penetration is desired. 
         FIG. 30  shows the curved introducer assembly of  FIG. 27  in the desired position on the septal wall with the sharp tip guide wire advanced from the distal end of the blunt end dilator, across and through the septal wall into the opposing chamber in the heart. The guidewire has a distal curvature that bends back on itself to present a nontraumatic shape. 
         FIG. 31  shows the curved introducer assembly of  FIG. 29  in the desired position on the septal wall with the sharp tip guide wire advanced from the distal end of the blunt end dilator, across and through the septal wall into the opposing chamber in the heart. The guidewire has a distal curvature that bends back on itself to present a nontraumatic shape. The stepped-down cannula has been advanced to the distal end of the blunt end dilator, but not beyond its distal tip. 
         FIG. 32  is a side cross sectional view of the introducer assembly of  FIG. 30  after the blunt end dilator and introducer have been advanced over the guidewire through the septal wall and into the opposing heart chamber. 
         FIG. 33  is a side cross sectional view of the introducer assembly of  FIG. 31  after the blunt end cannula has been advanced over the guidewire through the septal wall and into the opposing heart chamber. The introducer is not at this point yet advanced through the septal wall. 
         FIG. 34  is a side cross sectional view of the introducer assembly of  FIG. 33  after the blunt end cannula, blunt end dilator and introducer have been advanced over the guidewire through the septal wall and into the opposing heart chamber. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention described herein relates to devices and methods for puncturing the atrial septum via the percutaneous route for access to the left atrium through the right atrium for diagnostic or therapeutic purposes. 
     Devices and methods for performing a transseptal puncture procedure using a device which includes either an untapered or tapered blunt end cannula disposed in an introducer carrying a sharp guidewire disposed longitudinally through the lumen of the blunt cannula, wherein the guidewire is flexible and has an atraumatic conformation at its tip. The cannula gives the more flexible introducer a defined shape and steerabilty allowing an ordinarily skilled physician to easily access a selected location on the septal wall of the heart for transseptal puncture and introducer placement thereacross without employing an exposed sharp end needle or cannula during the procedure. 
     In one aspect, the invention relates to a percutaneous device for making a transseptal puncture in the atrial septum of the heart.  FIG. 1  is a plan view of the transseptal puncture device according to an illustrative embodiment of the invention. The illustrative percutaneous device  10  includes a blunt dilator  12  including a lumen  13  axially disposed along the long axis of the blunt dilator  12  and including a blunt distal end  17  having an opening  18 . A second, inner sharp-tipped guidewire  14  is axially disposed within the lumen of the blunt dilator  12 . The blunt dilator  12  provides structural support for the inner guidewire  14  and also functions as a dilator for the hole created in the atrial wall by the inner guidewire  14 . The device  10  may further feature a transcutaneous intravascular sheath  22  through which the device  10  passes from outside the patient&#39;s, body through, a vessel, for example, the femoral vein, through the inferior vena cava to the right atrium, and a control handle  26  at the distal end  27  of the sheath  22 . The sheath and/or other components of the delivery system may be steerable by actuators (not shown) on the control handle  26  to aid in delivering the device along the tortuous vascular path leading to the patient&#39;s right atrium. In certain embodiments, the distal end  17  of the blunt dilator  12  is tapered toward the inner guidewire  14 , and the distal end  27  of the sheath  22  is tapered toward the blunt dilator  12 . 
     In an embodiment, the blunt dilator  12  is similar in size to a transseptal dilator, e.g., with an inner tip diameter of about 0.8 mm. The percutaneous device  10  also features a septal perforator, for example, an inner guidewire  14 . Alternatively, the septal perforator is a radio frequency electrode (not shown) that is coupled to the blunt dilator  12 , or is a high pressure jet spray (not shown) that is emitted from the opening  18  of the blunt dilator  12 . 
     In an embodiment depicted in  FIGS. 2 and 3 , the inner guidewire  14  includes a sharp tip  25  at a distal end  15  of the inner guidewire  14 . The inner guidewire  14  is axially disposed within the lumen  13  of the blunt dilator  12 . The inner guidewire  14  is reciprocally and axially moveable in the lumen  13  of the blunt dilator  12 . The inner guidewire  14  can be rotated as well. The distal end  15  of the inner guidewire  14  is extendable through the opening  18  at the distal end  17  of the blunt dilator  12 . The inner diameter of the lumen  13  of the blunt dilator  12  typically approximates the outer diameter of the inner guidewire  14 . 
     The blunt dilator  12  and the inner guidewire  14  are made from various metals such as, for example, nitinol, steel, or titanium, or alloys thereof or polymers such as polyimide, PEBAX, polyethylene, polytetrafluoroethylene (EPTFE), Fluorinated ethylene propylene (FEP), and polyurethane. In one embodiment, the inner guidewire  14  is solid to increase its sharpness. Alternatively the inner guidewire  14  is hollow. The use of the blunt dilator  12  for introducing the inner guidewire  14  into the patient&#39;s cardiac tissue is preferred. In another embodiment, a sheath that is made from material that provides sufficient support during the transseptal puncture procedure is used and the blunt dilator  12  may not be needed. 
       FIGS. 4A and 4B  are a longitudinal view and an exploded view, respectively, of the distal end of a guidewire of a transseptal puncture device according to another illustrative embodiment of the invention. The illustrative inner guidewire  14  includes a waist  30  near the distal end  15  of the inner guidewire  14 . The waist  30  is positioned on an intermediate portion  16  of the inner guidewire  14  that is narrower in diameter than the portion of the inner guidewire  14  that is proximal to the intermediate portion  16  and the portion of the inner guidewire  14  that is distal to the intermediate portion  16 . The waist  30  is thereby more flexible or bendable than the portions of the inner guidewire  14  that are proximal or distal to the waist  30 . In one embodiment, the distal portion  15  is more flexible than the proximal portion  11  of the inner guidewire  14 . The intermediate portion  16  having waist  30  is positioned about 5 mm to about 30 mm, preferably about 20 mm proximal to the distal end  15  of the inner guidewire  14 . In an embodiment, the diameter of the waist  30  ranges from about 0.1 mm to about 0.5 mm, e.g., if the waist is composed of a metal, while the diameter of the inner guidewire  14  proximal to the waist  30  ranges from about 0.35 mm to about 1.5 mm and the diameter of the inner guidewire  14  distal to the waist  30  ranges from about 0.2 mm to about 1 mm. In another embodiment, the diameter of the waist  30  ranges from about 0.1 to about 1 mm, e.g., if the waist is composed of a non-metal, such as, for example, a polymer, such as (PEBAX) or polyurethane, a plastic, rubber, or any other polymer deemed suitable to those skilled in the art, or if the waist is comprised of a radiopaque coil, or a combination of non-metals, metal coils, with or without a solid metal core. In that case, the diameter of the inner guidewire  14  proximal to the waist  30  ranges from about 0.5 mm to about 3.0 mm and the diameter of the inner guidewire  14  distal to the waist  30  ranges from about 0.2 mm to about 3.0 mm. For example, the diameter of the waist  30  is about 0.2 mm, the diameter of the inner guidewire  14  proximal to the waist  30  is about 1 mm and the diameter of the inner guidewire  14  distal to the waist  30  is about 0.4 mm. 
       FIG. 5  is a longitudinal view of the distal end of a guidewire of a transseptal puncture device according to another illustrative embodiment of the invention. In one embodiment, the inner guidewire  14  diameter is larger (e.g., 1 mm larger) at the proximal end of the inner guidewire  14  than the distal end  15 . Alternatively, the inner guidewire  14  diameter is larger throughout the length of the inner guidewire  14  except for the most distal about 20 mm of the distal end  15 . In one embodiment, the inner guidewire  14  contains a portion  31  at the distal end  15  that is tapered or the diameter of the inner guidewire  14  is gradually stepped down, for example, to a diameter of about 0.1 to about 0.25 mm, preferably about 0.2 mm, at a point “A” about 10 mm to about 20 mm proximal to the tip  25  of the guidewire  14 . In an embodiment, the diameter of the guidewire  14  from the tip  25  to the point “A” is uniform. In a particular embodiment, the distal about 10 mm of the inner guidewire  14  adjacent to the tip  25  has a diameter of about 0.2 mm. According to this embodiment of the invention, the distal end  15  of the inner guidewire  14  is thinner and therefore is more flexible than the proximal portion  11  of the inner guidewire  14 . In another embodiment the tapered or step-down portion  31  can extend to the tip  25  of the inner guidewire  14  and can be about 5 mm to about 30 mm long. 
       FIG. 6  is a longitudinal view of the distal end of a guidewire of a transseptal puncture device according to another illustrative embodiment of the invention. At a position about 5 mm to about 30 mm, preferably about 20 mm from the distal end  15 , the inner guidewire  14  includes an intermediate portion  16  manufactured from, or coated with, a material or treated such that the intermediate portion  16  is more likely to bend than the portions of the inner guidewire  14  that are proximal  11  and distal  15  to the intermediate portion  16 . For example, if the inner guidewire  14  is composed of nitinol, the intermediate portion  16  may be annealed at 500 degrees Centigrade for 10 minutes to relieve stress in otherwise superelastic nitinol wire in an as-drawn condition. Alternatively, the intermediate portion  16  may be made from a softer or more flexible material than the proximal portion  11  and distal portion  15  of the inner guidewire  14 . For example, the material of the intermediate portion  16  may be a polymer while the proximal portion  11  and distal portion  15  on the inner guidewire  14  are made from, for example, a rigid metal or, alternatively, a spring metal, polymer, or elastomer, a nickel titanium alloy or superelastic material such as nitinol. The intermediate portion  16  may be comprised of a coil, or a series of spaced bands, more specifically this coil or bands may be a radiopaque material such as gold, platinum, tungsten, iridium, palladium, or any other material easily visible with x-ray, ultrasound, MRI, or other imaging technique. The intermediate portion  16  may be welded to, crimped or attached by adhesives to the proximal portion  11  and distal portion  15  of the inner guidewire  14 . In one embodiment, the intermediate portion  16  is about 0.5 mm to about 30 mm, preferably about 2 mm in length. Alternatively, geometric modification may make the intermediate portion  16  more flexible, for example, by the introduction of slits, grooves, cut-aways, notches, dimples, or other modification that thins portions of the wall of the intermediate portion  16 . 
     In another embodiment (not shown), the distal, the proximal, and/or the intermediate portion (if present) of the inner guidewire  14  is flexible. 
       FIG. 7  is a longitudinal view of the distal end of a guidewire of a transseptal puncture device according to another illustrative embodiment of the invention. The distal end  15  of the illustrative inner guidewire  14  may be straight (e.g., 0 degrees) or is bent at an angle ranging from about &gt;0 degrees to about 270 degrees, preferably about 180 degrees relative to the long axis of the inner guidewire  14 . 
     Alternatively, referring to  FIG. 8 , when the distal end  15  of the inner guidewire  14  is not constrained within the lumen  13  of the blunt dilator  12 , the distal end  15  has an essentially non-traumatic conformation, such as a helical, curved, cork screw, or hook shape. For example, the diameter “B” of the loop that forms the hook  32  can be between about 5 mm and about 30 mm, preferably about 10 mm. When the distal end  15  is enclosed within the lumen  13  of the blunt dilator  12 , the entire length of the inner guidewire  14  is substantially straight and parallels the long axis of the blunt dilator  12 . 
     In an alternative embodiment of the transseptal puncture device, the guidewire is replaced by a pulsating high pressure saline jet (or other suitable fluid) (not shown) generated by a pump. The jet spray is directed to the atrial septum from the distal end of the blunt, cannula according to the invention and incises the tissue. The cannula is then gradually advanced through the incision. Because the incision is made gradually and slowly, the method is safer than the currently used methods, for example, because there is a reduced risk of trauma and/or bleeding. 
     In yet another embodiment of the transseptal puncture device, the blunt, dilator is replaced by a radio frequency (RF) apparatus (not shown). The cannula according to the invention is insulated except for the dilator tip. The alternating current travels down the dilator. Preferably, unipolar electrodes can be used for the dilator with grounding pads typically placed on the patient&#39;s thighs. Alternatively, a bipolar electrode system can be employed as well. The application of RF to the dilator increases the tissue temperature around the dilator tip to over 100 degrees C. Mechanical cohesion in the tissue is diminished and allows the dilator to be advanced as pressure is applied to the tissue by the dilator tip. Any other method producing heat (e.g., such as electrical resistance, laser, or ultrasound) can be potentially used instead of RF. As with the saline jet described above, the incision is created slowly therefore the risk of accidental puncture of tissue that is not targeted for incision is minimal. 
     In another aspect, the invention provides a method using a percutaneous approach for puncturing the atrial septum of a patient to treat, for example, patent foramen ovale or to gain access to the left atrium to ablate the left atrial appendage.  FIGS. 9A-9E  depict the steps of an illustrative method for puncturing an atrial septum with the transseptal puncture device according to the invention. The illustrative method includes the step of introducing an intravascular sheath  22  in a vessel to access the lumen of the right atrium  24 . In an embodiment, the sheath  22  is tapered to enhance advancement of the sheath  22  though the atrial septum  26 . Referring to  FIG. 9A , after the sheath  22  is properly positioned in the right atrium  24 , the blunt dilator  12  of the transseptal device  10  is advanced distally toward the atrial septum  26  and positioned against septum primum  26   a  at the puncture site. The blunt distal end  17  of the blunt dilator  12  is then pushed against septum primum  26   a  until some tenting, of the atrial septum  26  is visible. The tenting should be sufficient to correctly identify the puncture site in the septum primum  26   a . Alternatively, visualization techniques such as, three-dimensional echocardiogram, ultrasound, or magnetic resonance imaging can be used that may work without tenting. Some amount of tenting also assists with the puncture itself. 
     Referring to  FIG. 9B , once the blunt dilator  12  is positioned, the inner guidewire  14  is advanced relative to the blunt dilator  12  through the septum  26 . At its most distal position, about 10 mm of the inner guidewire  14  should extend from the distal end  17  of the blunt dilator  12 . Alternatively, the most distal position could be about 30 mm, if the distal portion  15  of the guidewire  14  had a hook shape, as is shown in  FIG. 8 . In an embodiment, the transition from the hook portion to the straight portion of the inner guidewire  14  is exposed. The blunt dilator  12  fol lows the path of the inner guidewire  14  to the septum  26 . Because of the fine diameter, extreme sharpness, and the added stiffness provided by the blunt dilator  12 , the inner guidewire  14  can be initially advanced into the septum  26 . The motion of the inner guidewire  14  may be forward, vibrating, reciprocating, linear, or rotational, for example. In one embodiment, movement of the inner guidewire  14  is accomplished manually. Alternatively, movement of the inner guidewire  14  may be automated and therefore require additional controls such as a robotically actuated guidewire to be attached to the delivery system components such as the sheath  22 . Such devices of the invention are easier for the doctor to manipulate and safer for the patient. 
     Referring now to  FIG. 9C , once the distal end  15  of the inner guidewire  14  is positioned within the septum  26 , the tissue provides support to the exposed part of the inner guidewire  14  until the whole tip of the inner guidewire  14  is delivered into the left atrium  28 . The guidewire  14  may be advanced approximately 10 cm to sufficiently see the guidewire  14  outside of the cardiac silhouette, typically within the pulmonary veins using x-ray imaging or other imaging techniques. Referring to  FIG. 9D , the blunt dilator  12  is advanced and positioned in the left atrium  28 . Referring to  FIG. 9E , standard catheterization laboratory procedures are utilized to place the sheath  22  within the left atrium  28 . Once the sheath  22  is in the left atrium  28 , the other components of the device, for example, the inner guidewire  14  and the blunt dilator  12 , can be completely removed from the sheath  22  and the sheath  22  can be used to deliver implants, for example, such as an atrial occluder for the treatment of a patent foramen ovale, sutures, or other intracardiac therapeutic devices. For example, referring to  FIG. 9F , one half of an occluder  30  is released from the sheath  22  and positioned in the left atrium  28 . Referring to  FIG. 9G , the sheath  22  is then withdrawn into the right atrium  24  and the other half of the occluder  30  is released and positioned in the right atrium  24 . In an embodiment, the inner guidewire  14  is left behind, traversing the puncture site, and acts to maintain the puncture site as well as to act as a guidewire (e.g., and the blunt dilator  12  is withdrawn). In another embodiment, the inner guidewire  14  is withdrawn, e.g., into the blunt dilator  12 . 
     The method for transseptal puncture using the transseptal device described herein is advantageous over conventional methods. For example, when using the devices and methods of the invention inadvertent contact of the inner guidewire  14  with the left atrial free wall (not shown) immediately after the septum  26  is punctured does not result in damage to or perforation of the left atrial free wall because the distal end  15  of the inner guidewire  14  is very flexible, as illustrated, for example, in  FIG. 4  and corresponding text, or has an alternative curved tip  25 , as illustrated, for example, in  FIG. 8  and corresponding text, when fully extended from the distal opening  18  of the blunt dilator  12 . When the distal end  15  of the inner guidewire  14  contacts the left atrial free wall, the distal end  15  of the inner guidewire  14  harmlessly bends rather than perforates the left atrial free wall. In one embodiment, the distal end  15  of the inner guidewire  14  bends because of the enhanced flexibility of the inner guidewire  14  at the intermediate portion  16 , as described above in connection with  FIGS. 4-8 , between the proximal portion  11  and distal portion  15  of the inner guidewire  14 . n an embodiment, perforation of the left atrial wall is avoided by modifying the shape of the inner guidewire  14  to form, for example, a hook or a bend. 
     Another advantage of the transseptal puncture devices described herein is the ability of the device to puncture through thick septum such as septum secundum. The transseptal puncture devices according to the invention can be used for remote suturing of a PFO or other defects that may be accessed percutaneously. 
     The transseptal puncture device according to the invention can also be used with various atrial septal defect locators such as those described in U.S. Ser. No. 10/660,444. For example, the locator may stabilize (e.g., constrain) the motion of the septa during insertion of the inner guidewire. Generally, a locator system includes a plurality of flexible members, at least one flexible member positionable on a side of the tissue opposite to another flexible member. 
       FIG. 10  illustrates a septal puncture apparatus  100  including three flexible members  142   a ,  142   b , and  142   c  (generally  142 ) coupled to a delivery member  120  for applying, e.g., a pressure or force to a region in a body by pushing, pulling, or restraining the tissue, thereby stabilizing the tissue. The flexible members  142   a ,  142   b , and  142   c  may be hexagonal in shape and coupled to a distal end  124  of the delivery member  120 , thereby forming, generally, a planar array  150 . The delivery member  120  is slideably receivable within a lumen  110  of the elongate member  104 . Instruments, e.g., the delivery member  120  and a cutting member  300  (e.g., a member that perforate the tissue, which can comprise, referring to  FIG. 1 , an inner guidewire  14  and/or an blunt dilator  12 , for example), are slideably receivable in the lumen  110  of the elongate member  104 . In this embodiment, the cutting member  300  is slideably receivable in a lumen  308  of the delivery member  120  and extends distally or withdraws proximally from an opening  312  at the distal end  124  of the delivery member  120 . 
       FIG. 10  also illustrates an exemplary interface  130  that permits controllers, for example, a set of apparatus controllers  134  and  138  to communicate with the elongate member  104  and the delivery member  120 , respectively. The exemplary controllers  134  and  138  extend, retract or otherwise manipulate, e.g., the elongate member  104  and the delivery member  120 , respectively. A single controller, could, alternatively, control all functions and operations of the tissue puncture apparatus  100  and the instruments disposed therein. 
     By way of example, the elongate member  104  and the delivery member  120  are flexible tubes fabricated from a biocompatible material, e.g., polyethylene, polyether-amide block co-polymer (PEBAX), polyurethane, or fluorinated ethylene propylene. 
     By way of example, the flexible members  142  are manufactured using nickel-titanium material, such as Nitinol.™. (Nitinol Devices and Components, Freemont, Calif.), or other shape memory alloy materials. The nickel-titanium wire, when properly manufactured, exhibits elastic properties for the wire to be manipulated (e.g., bent) by an operator and then returned to, substantially, the same shape the wire possessed prior to it being manipulated. 
     Alternatively,  FIG. 11  illustrates a portion of a septal puncture apparatus  100  including exemplary flexible members  142 ′ a  and  142 ′ b  which each include a leg such as a wire having a first end  204 ′ a  and  204 ′ b , respectively, joined to the distal end  124  of the delivery member  120 . Each of the flexible members  142 ′ a  and  142 ′ b  also have a second distal end  202 ′ a  and  202 ′ b , respectively, that is free, i.e., not joined to any other structure of the septal puncture apparatus  100 . The longitudinal axis of the flexible members  142 ′ a  and  142 ′ b  are oriented substantially parallel to the elongate member  104  when the flexible members  142 ′ a  and  142 ′ b  are located within the lumen  110  of the elongate member  104 . The flexible members  142 ′ a  and  142 ′ b  have a first portion  272   a  and  272   b , respectively and a second portion  270   a  and  270   b , respectively. The flexible members  142 ′ a  and  142 ′ b  are disposed within the lumen  110  in a contracted position such that the second ends  202 ′ a  and  202 ′ b  are directed distally towards the opening  112  in the distal end  106  of the elongate member  104 . The flexible members  142 ′ a  and  142 ′ b  are freed from the confines of the lumen  110  by moving the flexible members  142 ′ a  and  142 ′ b  between the contracted position illustrated, for example, in  FIG. 11  and an extended position, such as the extended position depicted in  FIG. 12B . After insertion into the lumen  110  of the elongate member  104 , the flexible members  142 ′ a  and  142 ′ b  apply a force to an inner surface  210  of the elongate member  104  in a first location  230   a  and  230   b , respectively, on the inner surface  210  of the lumen  110  that the flexible members  142 ′ a  and  142 ′ b  contact. 
     Referring now to  FIG. 12A , as the delivery member  120  is extended out of the opening  112  of the elongate member  104 , the second ends  202 ′ a  and  202 ′ b  of the flexible members  142 ′ a  and  142 ′ b , respectively, undergo an articulation and point, generally, in a proximal direction toward the handle (not, shown). Referring now to  FIG. 12B , the elongated delivery member  120  is further extended distally along the lengthwise dimension (in the positive direction along the X-axis) of the lumen  110  until the distal end  124  of the delivery member  120  emerges from the opening  112  of the elongate member  104 . The second ends  202 ′ a  and  202 ′ b  of the exemplary preshaped flexible members  142 ′ a  and  142 ′ b  respectively, undergo an additional articulation and as a result point, generally, towards one another. In this extended position, each of the flexible members  142 ′ a  and  142 ′ b  is substantially planar in shape. 
     Alternatively, the second ends, for example, the second ends  202 ′ a  and  202 ′ b , may have a different diameter than other locations along the length of the flexible elastic members  142 ′ a  and  142 ′ b . By way of example, an operator may select an apparatus having flexible members that have second ends  202 ′ a  and  202 ′ b  having a larger diameter to, for example, reduce trauma to tissue the second ends  202 ′ a  and  202 ′ b  contact during use. Alternatively, the second ends  202 ′ a  and  202 ′ b  may have a ball shaped tip. 
       FIG. 13  depicts exemplary flexible members  142 ″ a  and  142 ″ b  that include a first wire loop section  220   a  and a second loop section  220   b , respectively. The tip  406   a  and  406   b  of the loop sections  220   a  and  220   b , respectively, point, generally, towards one another and towards the delivery member  120 . Loop sections  220   a  and  220   b  may, alternatively, be oriented in a variety of directions (e.g., away from the delivery member  120  or at a 45 degree angle away from the delivery member  120 ). 
     Referring now to  FIGS. 14A and 14B , a septal puncture apparatus  100  includes a single flexible member  142 ′″ that has a middle section  540  located, generally, intermediate the first end  206  and the second end  208  of the flexible member  142 ′″. The flexible member  142 ′″ thereby forms a closed loop. In this embodiment, the flexible member  142 ′″ is configured so the middle section  540  is located, generally in the center of a plane defined by the flexible member  142 ′″ as illustrated by the end-on view of  FIG. 14B . In this configuration, the middle section  540  of the flexible member  142 ′″ aids with stiffening the flexible member  142 ′″, which minimizes bending when, for example, the flexible member  142 ′″ is used by an operator to apply forces to a tissue, e.g., the atrial septum. In this configuration, the flexible member  142  forms a closed loop that is sized and shaped, for example, to contact a first and second side of a tissue. 
     Referring now to  FIGS. 15A and 15B , the flexible elastic member  142 ″″ is a coil and has a spiral shape. By way of example, in use, a portion  1410  of the flexible member  142 ″″ can be located on a first side of a tissue and a portion  1420  of the flexible member  142 ″″ can be located on a second side of a tissue. For example, the flexible member  142 ″″ can be screwed through a tunnel or a hole, such as a defect in the atrial septum. Alternatively, the distal end  124  of the delivery member  120  may be located axially through, for example, a hole in a tissue such that the flexible member  142 ″″ may be withdrawn partially through the hole by a rotational (screw-like) motion of the delivery member  120  thereby locating the portion  1410  of the flexible member  142 ″″ on a first side of the tissue and the portion  1420  of the flexible member  142 ″″ on a second side of a tissue. 
     Referring to  FIG. 16A , the delivery member  120  is translated axially along the lengthwise dimension of the lumen  110  until the distal end  124  of the delivery member  120  emerges from an opening  112  in the elongate member  104  and the flexible members  142   a ,  142   b , and  142   c  transition from the contracted first position  330  shown in  FIG. 16A  to a second extended position  340  shown in  FIG. 16B . The exemplary flexible members  142   a ,  142   b , and  142   c  expand to assume, for example, substantially hexagonal shapes upon emerging from the opening  112  in the elongate member  104  and expanding. The extended flexible members  142   a ,  142   b , and  142   c  are substantially planar. The plane defines a plurality of axes that lie in the plane and the plurality of axes are non-parallel to (i.e., biased relative to) the elongate member  104 . An angle  344  defined by at least one of the plurality of axes of the plane of the flexible members  142   a ,  142   b , and  142   c  and the longitudinal axis of the elongate member  104  is typically specified (e.g., by an operator) such that the flexible members  142   a ,  142   b , and  142   c  are flush with tissue surface and are capable of applying a force across a large tissue area. For example, the angle  344  might be chosen to ensure the flexible members  142   a ,  142   b , and  142   c  conform to the shape of a tissue surface abutting the flexible members  142   a ,  142   b , and  142   c . If the force is applied, e.g., across a large tissue area the movement of the tissue in any location across the tissue area will be minimized. The flexible members  142   a ,  142   b , and  142   c  could, alternatively, be of any shape (e.g., polygonal, circular, or ellipsoidal) or of any quantity (e.g., one, two, or five) where the shape and/or quantity of the flexible members  142   a ,  142   b , and  142   c  are typically selected to distribute as much force as possible while still being able to fit within the lumen  110  of the elongate member  104  and emerge from or retract into the lumen  110 . 
     When the flexible members  142   a ,  142   b ,  142   c  are extended in the second expanded position  340  upon emerging from the opening  112 , the exemplary cutting member  300  extends axially in the lumen  308  of the delivery member  120  until a cutting tip  304  of the cutting member  300  emerges from the opening  312  in the distal end  124  of the delivery member  120 . The tip  304  of the cutting member  300  cuts the tissue in close proximity to the opening  312  of the delivery member  120 . 
     Referring now to  FIG. 17 , an operator introduces an elongate member  104  into the right atrium  748  of a heart  742  through the descending vena cava  750 . The elongate member  104  is advanced distally until the distal end  106  of the elongate member  104  passes through a defect  620  (for example, a patent foramen ovale) in the septum  740 . The distal end  106  of the elongate member  104  is shown at an angle  770  of a bout 45 degrees relative to the longitudinal axis of the elongate member  104  due to a bend  760  in the distal end of  106  of the elongate member  104 . The bend  760  in the elongate member  104  may be mechanically pre-formed or pre-bent at the angle  770  between about 0 degrees and about 180 degrees prior to insertion of the elongate member into the body. The bend  760  could, alternatively, be accomplished by heating a nickel-titanium material or other shape memory alloy located within the distal end  106  of the elongate member  104 . 
     The septal puncture apparatus shown in  FIGS. 18A, 18B, and 18C  includes two flexible members  142 ′ a  and  142 ′ b  coupled to the distal end  124  of the delivery member  120 . 
     The flexible members  142 ′ a  and  142 ′ b  are initially located within the lumen  110  of the elongate member  104 . An operator initially guides the distal end of  106  of the elongate member  104  through the defect (hole)  620  such that the distal end  106  is located on a second side  820  (in the left atria of the heart) of the septum secundum  600  and septum primum  610 . Now referring to  FIG. 18A , the operator then extends the flexible members  142 ′ a  and  142 ′ b  as described herein with respect to, for example,  FIGS. 12A and 12B . 
     With continued reference to  FIG. 18A , the elongate member  104  is retracted proximally until the distal end  106  of the elongate member  104  passes back through the defect  620  and is positioned on the first side  810  of the septum  740 . 
     The delivery member  120  is then retracted proximally so the second portions  270   a  and  270   b  of the flexible members  142 ′ a  and  142 ′ b  and the distal end  124  of the delivery member  120  are in close proximity to the defect  620 , the septum primum  610 , and the septum secundum  600  on the second side  820  of the septum  740 . 
     Now referring to  FIG. 18B , as the delivery member  120  is further retracted proximally such that the distal end  124  of the delivery member  120  is withdrawn through the defect  620  until it is in contact with or in close proximity to the first surface  880  of the septum primum  610  on the first side  810  of the septum primum  610 . The second portions  270   a  and  270   b  of the flexible members  142 ′ a  and  142 ′ b  are positioned, generally non-parallel to the longitudinal axis of the elongate member  104  and are in physical contact with at least the second surface  870  of the septum primum  610  on the second side  820  of the septum primum  610  and also partially located within the defect  620  in the septum  740 . The first portions  272   a  and  272   b  of the flexible members  142 ′ a  and  142 ′ b  are located on the first side  810  of the septum  740 . Accordingly, the flexible members  142 ′ a  and  142 ′ b  are sized and shaped for contact with the first side  810  and the second side  820  of the septum  740 . The flexible members  142 ′ a  and  142 ′ b  are thus capable of limiting movement of the septum primum  610 . Now referring to  FIG. 18C  the cutting member  300  is extended from the opening  312  in the distal end  124  of the delivery member  120 . The cutting tip  304  of the cutting member  300  introduces a hole  1005  (tissue opening) through the septum primum  610 . 
     Referring now to  FIG. 19 , an exemplary flexible member  142  is attached to the distal end  124  of the delivery member  120 , which extends from the opening  112  in the distal end  106  of the elongate member  104 . The delivery member  120  and the elongate member  142  are located on the first side  810  of the septum secundum  600 . The distal end  124  of the delivery member  120  is located in close proximity to the tissue surface of the septum secundum  600  on the first side  810  of the septum secundum  600 . The flexible member  142  extends through the hole  620  between the septum primum  610  and the septum secundum  600  from the first side  810  to the second side  820 . The first side  810  of the septum primum  610  opposes the second side  820  of the septum primum  610 . The flexible member  142  is positioned so that the second end  202  and second portion  270  of the flexible member  142  are located on the second side  820  of the septum secundum  600  and the first portion  272  of the flexible member  142  is located on the first side  810  of the septum secundum  600 . In this configuration, the flexible member  142  is thus capable of limiting movement of the septum secundum  600 . In this embodiment only the septum secundum  600  is secured to limit movement. In alternative embodiments, however, the septum secundum  600  and/or the septum primum  610  may be secured to limit movement. 
     Turning to  FIGS. 20 a -20 d    which show overall side views of the blunt end cannula assembly of the improved embodiments.  FIG. 20 a    is a side plan view of the cannula assembly  34  with the distal insert  33  showing the blunt end  37  of the curve  40  in  FIG. 20 e    and the proximal inset  75  showing the plan side view of the valve  41  and hub  43  in  FIG. 20 b   . A side cross sectional view of the hub  43  and assembly  34  is depicted in  FIG. 20 c    with the proximal inset  45  showing the hub  43  with the valve  41  in the open configuration in  FIG. 20 d   . The cannula assembly  34  comprises a tubular cannula  35  that may be metal, polymer, composite, or glass, though preferably stainless steel or nickel titanium alloy. The distal end of the tubular cannula  35  is necked down, tapered, or formed from two pieces so that the distal diameter is able to fit through the smaller diameter of an introducer dilator  55  ( FIG. 22 ). The proximal portion of the tubular cannula  35  is typically 18 gauge for adult sized systems and 19 gauge for pediatric systems, though may be as large as 12 gauge and as small as 30 gauge, whereas the distal necked down portion of the tubular cannula  35  is typically 21 gauge for adult sized systems and 22 gauge for pediatric systems, though may be as large as 15 gauge and as small as 36 gauge. The tubular cannula  35  inner diameter is a function of the cannula wall type which is typically regular wall (RW) or thin wall (TW) but may also be extra thin wall (ETW), ultrathin wall (UTW) or microthin wall (MTW) as provided by K-Tube Technologies in Poway, Calif. The inside surface finish of the tubular cannula  35  can be as low as 4 RMS (root mean square in micro-inches, which is a surface finish measurement based on the average of the peaks and valleys of the surface profile) to as high as 125 RMS, thong h preferably is fabricated by being plug drawn with a smoother &lt;32 RMS to facilitate insertion of devices through the cannula. The distal curve  40  serves to steer the introducer assembly  31  ( FIG. 22 ) to the desired anatomy of the heart. The curve radius is typically around 50 mm but my be as small as 25 mm and as large as 100 mm, with arclengths ranging from 10 mm to 100 mm but preferably between 35 to around 75 mm. Another aspect of the tubular cannula  35  is that it may be formable or malleable so that the end user can increase or decrease the amount of curve  40  depending on the specific anatomy of the patient. The proximal end of the tubular cannula  35  is coupled to a hub  43  such that rotation or motion of the hub  43  is precisely transmitted to the cannula  35 , and steering of the curve  40  may be accomplished by the user through manipulation of the hub  43 . Any suitable connection may be used between the cannula  35  and the hub  43 , though a press fit and adhesive are preferred, other methods such as solder, welding, compression fit, screws, or flaring may also be used, and the connection may be releasable if a single hub  43  is used with different lengths of cannula  35 . Typical lengths for the cannula  35  match the transseptal introducers currently available, and are 56 cm, 71 cm, 89 cm, 98 cm, and 101 cm, though it is conceived that any length suitable for reaching the heart from the groin, abdomen, or chest. The hub  43  may be made of metal, polymer, elastomer, composite, or ceramic, though it is most desirable to fabricate the hub from a polymer such as polycarbonate so that it can be transparent or translucent. A proximal Luer fitting on the hub  43  enables a fluid or pressure line to be releasably connected and be in fluid communication with the inner diameter of the tubular cannula  35 . Also in fluid communication with the hub  43  is a valve  41  which enables the fluid communication to be open or closed in a similar fashion to a stopcock. The fluid communication as shown in  FIG. 20 d    is a one way, on/off design, however it is also conceived to add additional ports to allow for additional devices and lines to be connected and be in fluid communication with the inner diameter of the tubular cannula  35 . Additional valves may also be provided on these additional ports so as to control fluid, air, blood flow through these ports. The valve  41  may be made of metal, polymer, elastomer, rubber, composite, or ceramic, though it is most desirable to fabricate the hub from a polymer such as high density polyethylene so that when mated with hub  43 , the valve  41 , which also incorporates a handle shape, may provide a hemostatic fluid tight connection. 
       FIGS. 21 a -21 d    are overall side views of the cannula assembly  36  of the improved embodiments.  FIG. 21 a    is a side plan view of the assembly  36  with the distal insert  49  showing the blunt end  47  of the curve  56  in  FIG. 21 e    and the proximal inset  51  showing the plan side view of the cannula valve and hub in  FIG. 21 b   . A side cross sectional view of the hub  43  and assembly  36  is depicted in  FIG. 21 c    with the proximal inset  53  showing the hub  43  with the valve  41  in the open configuration in  FIG. 21   d.    
       FIG. 22  is a side cross sectional view of the introducer assembly  31  in enlarged scale showing the blunt end dilator  55  extending from the end of the introducer sheath  57  and the cannula  39  and guidewire  59  disposed in the dilator  55  in a more proximal position. The untapered cannula  39  is used inside the introducer sheath  57  to shape the introducer assembly  31 , provide it with enhanced steerability, and to provide columnar support for both the introducer assembly  31  and the floppy guidewire  59  allowing it to be pushed through the septum and thereafter assume an atraumatic J-shaped configuration as it is advanced further. 
       FIG. 23  shows the distal portion of the introducer assembly  31  of  FIG. 22  in enlarged scale in which the cannula  39  has been advanced to a distal internal stop  61  in the dilator  55  carrying the sharp tip guidewire  59  with it. In this embodiment the cannula  39  cannot be advanced out of and beyond the distal end  63  of the blunt end dilator  55 . 
       FIG. 24  is a side cross sectional view of another embodiment of the introducer assembly  31  in enlarged scale showing the blunt end dilator  55  extending from the end of the introducer sheath  57  and a tapered cannula  39   a  and guidewire  59  disposed in the dilator  55  in a more proximal position in the embodiment where the cannula has a portion  65  with a stepped-down or tapered outer diameter which will allow it to extend past the internal distal stop  61  in the blunt end dilator  55 . It is also conceived that a stylet (not shown) may be used with the tapered cannula  39   a  in place of the sharp tip guidewire  59 , especially for placement of the tapered cannula  39   a  through the dilator  55 . A stylet (not shown) is useful as an obturator for the tapered cannula  39   a  as well as to prevent any skiving of the dilator  55  when the tapered cannula  39   a  is advanced through the curved portion. The stylet (not shown) may lock onto the proximal hub  43  ( FIG. 20 a   ) of the cannula assembly  34  ( FIG. 20 a   ) and may be made of metal, polymer, composite, or glass, though preferably from stainless steel or nickel titanium alloy. The distal end of the stylet may also be tapered or necked down so as to fit through the distal necked down or tapered portion  65  of the tapered cannula  39   a.    
       FIG. 25  shows the distal portion of the introducer assembly  31  of  FIG. 24  in enlarged scale in which the cannula  39   a  has been advanced past the distal internal stop  61  in the dilator  55 , extending from the distal end  63  the blunt end dilator  55  and carrying the sharp tip guidewire  59  within it. 
     The foregoing features can now be understood with respect to their operation and utility in the heart to effect a transseptal penetration using an introducer assembly  31  by viewing  FIGS. 26-34  in the sequence described below for both the untapered and tapered cannulas  39  and  39   a  respectively.  FIG. 26  shows the curved introducer assembly  31  in the configuration of  FIG. 22  with the untapered cannula  39  within the atrium of the heart with the blunt end dilator  55  at or near a lower point on the septal wall  67  distant from the target location at which septal penetration is desired. The cannula  39  is not proximate to the dilator tip  63  so the final intended shape has not been imparted to introducer assembly  31  by cannula  39  carrying guidewire  59 . 
       FIG. 27  shows the introducer assembly  31  of  FIG. 26  in which the cannula  39  carrying, the guidewire  59  has been advanced within introducer assembly  31  until the distal end  69  of the cannula  39  abuts the internal distal stop  61  in the blunt end dilator  55 , showing how the cannula  39  gives a predetermined desired shape to the introducer assembly  31  to bring the tip  63  of blunt end dilator  55  to the desired position on the septal wall  67  where penetration is desired and to allow the steerability of introducer assembly  31  so that it can be manipulated or steered as desired. At this point the introducer assembly  31  can be advanced as a whole to tent the septal wall  67  prior to penetration. 
       FIG. 30  shows the curved introducer assembly  31  of  FIG. 22  with the untapered cannula  39  in the desired position on the septal wall  67  with the sharp tip guide wire  59  advanced from the distal end  63  of the blunt end dilator  55 , across and through the septal wall  67  into the opposing chamber  71  in the heart. The guidewire  59  has a distal curvature  73  that bends back on itself to present a nontraumatic shape. Any advancement of guidewire  59  therefore will not result in further penetration into cardiac tissue. 
       FIG. 32  is a side cross sectional view of the introducer assembly  31  of  FIG. 30  after the blunt end dilator  55  and introducer sheath  57  have been advanced over the guidewire  59  with its atraumatic distal bend  73  through the septal wall  67  and into the opposing heart chamber  71 . Cannula  39  in this embodiment is necessarily retained within the dilator  55  and may or may not be located in chamber  71  depending on the degree of advance of introducer assembly  31  as a whole. 
       FIG. 28  is a side cross sectional view of the introducer assembly  31  of  FIG. 24  showing the blunt end dilator  55  extending from the end of the introducer sheath  57  and the cannula  39   a  and guidewire  59  disposed in the dilator  55  in a more proximal position in the embodiment where the cannula  39   a  has a portion  65  which has a stepped-down or tapered outer diameter which will allow it to extend past, the internal distal stop  61  in the blunt end dilator  55 . 
       FIG. 29  shows the introducer assembly  31  of  FIG. 28  in which the stepped-down cannula  39   a  carrying the guidewire  59  has been advanced through the internal distal stop  61  in the blunt, end dilator  55 , showing how the cannula  39   a  gives a predetermined desired shape to the introducer assembly to bring the blunt end cannula  39   a  to the desired position on the septal wall  67  where penetration is desired and to provide the needed steerability and column strength to do so. Again at this point in the procedure introducer assembly  31  can be advanced as a whole to tent septal wall  67  prior to and during penetration. 
       FIG. 31  shows the curved introducer assembly of  FIG. 29  in the desired position on the septal wall  67  with the sharp tip guide wire  59  advanced from the distal end  63  of the blunt end dilator  55 , across and through the septal wall  67  into the opposing chamber  71  in the heart. The guidewire  59  has a distal curvature  73  that bends back on itself to present a nontraumatic shape. The stepped-down cannula  39   a  has been advanced to the distal end  63  of the blunt end dilator  55 , but not beyond its distal tip  63 . 
       FIG. 33  is a side cross sectional view of the introducer assembly  31  of  FIG. 31  after the blunt end cannula  39   a  has been advanced over the guidewire  59  through the septal wall  67  and into the opposing heart chamber  71 . The introducer sheath  57 , and dilator  55  are not at this point yet advanced through the septal wall  67 . 
       FIG. 34  is a side cross sectional view of the introducer assembly  31  of  FIG. 33  after the blunt end cannula  39   a , blunt end dilator  55  and introducer sheath  57  have been advanced over the guidewire  59  through the septal wall  67  and into the opposing heart chamber  71 . The extent of advancement of cannula  39   a , dilator  55  and sheath  57  into chamber  71  is variable and determined according to the physician&#39;s choice. 
     Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the embodiments. Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the embodiments as defined by the following embodiments and its various embodiments. 
     Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not, be taken as limiting the embodiments as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the embodiments includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations. A teaching that two elements are combined in a claimed combination is further to be understood as also allowing for a claimed combination in which the two elements are not combined with each other, but may be used alone or combined in other combinations. The excision of any disclosed element of the embodiments is explicitly contemplated as within the scope of the embodiments. 
     The words used in this specification to describe the various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself. 
     The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Although elements may be described above as acting in certain combinations and even initially claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements. 
     The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptionally equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the embodiments.