Endoluminal tissue excision catheter

Abstract: An excision catheter comprises a cylindrical cutting head (22) with a rearwardly directed cutting edge (24). The catheter has a flexible nose (36) enabling the catheter to be fed into an artery over a pre-inserted guide wire which passes through the lumen (32) of the catheter. During insertion, the cutting edge (24) is shielded by the distal end (58) of an outer sleeve catheter (52). Following insertion, the sleeve (52) can be retracted to expose the cutting edge (24) of the cutting head (22). The cutting head is then pulled back through the obstructive tissue which accumulates in the tissue collection chamber (28) inside the cutting head (22). Prior to withdrawal, the open end of the cutting head can once again be sealed by retraction against the tip (58) of the outer sleeve (52), thus trapping the excised tissue in the chamber (28) for removal of that tissue from the body. Preferably means are provided for rotating the cutting head during the excision.

Description: This invention relates to an Endoluminal Tissue Excision Catheter (ETEC) for the excision of tissue within the lumen of a vessel in a human or animal. Although much of the description herein concerns atherectomy of plaque from within an artery, excision catheter device of this invention is applicable quite generally to the excision of any tissue from any vessel of a living body. There are numerous treatments to remove tissues from lumens within the vessels in a living body including surgical interventions such as endarterectomy and by-pass surgery using veins or artificial graft materials. Balloon angioplasty is becoming increasingly popular for the dilation of arterial stenoses without the excision of the plaque. More recently atherectomy, the excision from an artery of atheromatous plaque, has been successfully used to open arterial stenoses. In published UK Patent Application 2,044,103A there is described a device for removing plaque within an artery by drawing together two cutting edges that are initially placed on either side of an arterial stenosis. There are numerous disadvantages to that device, in particular: (1) two cutting edges are required which is more costly and complex compared to one cutting edge, and two edges require very precise alignment in order to properly cut without tearing, (2) there is no means to prevent dulling of the head's cutting edge 4 as it is pulled into the body 1, (3) no guide wire is provided to guide the cutting head to and through the stenosis, (4) the entire distal portion is rigid for a considerable length; explicitly the device lacks a long flexible tip thereby making it difficult for the catheter tip to pass through highly curved blood vessels, (5) there is no means for injecting contrast media, (6) there is no means for flushing out the excised tissue from the tissue collection chamber, and (7) there is no mechanism for rotation or mechanical vibration of the cutting edge so as to enhance the cutting action. In our U.S. Patent 4,765,332, we disclosed a retrograde cutting catheter that can be advanced over a guide wire with a single cutting edge that can be rotated or mechanically vibrated, and comprising a cut plaque collection chamber, but with no means to positively seal the cut plaque in the plaque collection chamber after it has been cut which is a feature of the present invention. In US-A-4867156 an excision catheter is shown having a rearwardly directed cutting edge in surrounding relationship to an excised tissue collection chamber. In that case the sheathing catheter carries at its distal end a cap which is engageable into the rearwardly open end of the tissue collection chamber. That end cap has a plain cylindrical surface. In accordance with the present invention, there is provided an excision catheter for excising tissue from within the lumen of a tubular vessel within the human or animal body, the catheter comprising a first tubular catheter member advanceable into the tubular vessel over a guide wire preinserted therein, said first catheter member carrying at its distal end a rearwardly open, hollow, rigid cylindrical cutting head advanceable into the tubular vessel to a location situated beyond the tissue to be excised, said cutting head having a rearwardly directed circular cutting edge at its proximal end and rearwardly open inner chamber for the collection of tissue excised from the lumen of the tubular vessel as the catheter is retracted back through the vessel in the opposite direction to the direction of insertion, a tubular, sheathing catheter member coaxially sheathing the first catheter and carrying at its distal end a plug member which is engageable in the proximal end of the tissue collection chamber so as to close the tissue collection chamber in the cutting head prior to the withdrawal of the catheter and cutting head from the tubular vessel, but after the said retraction of said cutting head through said tissue, and thereby to seal the excised tissue in the collection chamber, characterised in that the plug on the distal end of the sheathing catheter member has a cylindrical proximal portion connected to the distal end of the sheathing catheter and a conical distal end or nose portion which tapers to a minimum diameter at the distal end of the plug, that minimum diameter being less than the diameter of the cutting edge and the diameter of the cutting edge being less than that of the cylindrical proximal portion of the plug so that the distal end of the plug can be engaged in the rearwardly open end of the tissue collection chamber and when so engaged the tapered surface of the plug engages the proximal end of the cutting head around its full circumference with said cylindrical proximal portion of the plug serving to space the cutting edge from the interior wall of the lumen. An embodiment of the present invention, the Endoluminal Tissue Excision Catheter system (abbreviated herein to ETEC), thus comprises a pull-back catheter of the type described in US-A-4765332, but in which the collection chamber for the excised tissue can be positively sealed by retraction against a tapered plug carried by the distal end of the closing or outer sheathing catheter prior to withdrawal of the ETEC from the body, that tapered plug serving to space that cutting edge a small distance from the internal wall of the lumen, and thus preventing accidental damage to the lumen during insertion and withdrawal of the catheter. More specifically in accordance with the invention, the plug on the distal end of the sheathing catheter has a cylindrical proximal portion, the diameter of which is approximately equal to the diameter of the cutting head and a tapering distal end or nose portion which engages into and seals the open end of the tissue collection chamber with the cutting edge engaging the tapering surface of that distal end portion throughout a full 360° arc. Preferably the ETEC has a flexible plastic tip which facilitates entry over a guide wire into the lumen of a vessel such as an artery. While it is being pushed forward through an arterial stenosis (or any obstructive tissue) the ETEC would be closed, i.e. the single cutting edge of the cut/collect catheter portion of the ETEC system would be in contact with the distal end of a closing catheter that surrounds most of the length of the cut/collect catheter. After ETEC's distal end is passed beyond the tissue to be excised, the closing catheter would then be pulled back so as to expose the single cutting blade. The cutting blade would then be pulled back (typically while rotating) and the excised tissue would collect into a tissue collection chamber until the blade was in contact again with the tapering surface of the end plug carried by the distal end of the closing catheter. Thus the cut tissue is completely contained and the cutting edge is protected. The entire ETEC system is then withdrawn from the vessel, and the excised tissue can be flushed from the tissue collection chamber. ETEC's of sequentially larger diameter would be used until the largest catheter diameter that is used is just slightly smaller than the unoccluded luminal diameter of the vessel from which the tissue is being excised. In the preferred construction any time when the catheter is in the vessel, contrast media can be injected from the closing catheter's distal end, and fluoroscopy can then be used to define the state of the vessel. Other features of the present invention will become apparent from the following description of the preferred embodiment made with reference to the accompanying drawings, in which, Figure 1 is a cross section of the distal end of the ETEC in a closed position. Figure 1a is an enlarged cross-sectional view of one side of the cutting edge showing how it makes contact with the distal end of the cut/collect catheter. Figure 2 is a transverse cross section of the ETEC at position 2-2 of Figure 1. Figure 3 is a partial section of the proximal end of the ETEC system. Figure 4 shows a partial section of the rotator which is used to spin the cut/collect catheter portion of the ETEC system. Figure 5 is a cross section of the distal end of the ETEC in an open position showing cutting and collecting of stenotic plaque. Figure 1 is a longitudinal cross-sectional view of the distal end of the ETEC system 10 which consists of a cut/collect catheter 20 and a closing catheter 50. The cut/collect catheter 20 has a cutting cylinder 22 with a cutting edge 24 at its proximal end and which cylinder 22 encloses a tissue collection chamber 28 where the cut tissue is collected. Inside the chamber 28 is a cylinder support 30 that (as also seen in FIG. 2 which is the section at 2-2 of FIG. 1) has two passagways 34 that allow fluid communication between the interior lumen 32 of the support 30 and the collection chamber 28. The support 30 would typically be spot welded at one or more points to the cylinder 22. The cutting cylinder's distal end 26 is formed with indentations to securely hold onto a flexible plastic tip 36 which has a lumen 38 that is in fluid communication with the lumen 32. The proximal end of the cylinder support 30 is welded to the distal end of a metal cannula 40 which has an interior lumen 42 as shown in FIG. 1. The proximal end of the cannula 40 is attached to the distal end of a plastic torqueing cylinder 44 which has a central lumen 46 which is in fluid communication with the other interior lumens of the ETEC 10. A machined cut-out 48 in the cannula 40 provides a secure mechanical attachment of the torqueing cylinder 44 to the cannula 40. A separate non-spinning washer cylinder 49 surrounds the metal cannula. Its function is to remain stationary relative to the tissue being excised while the cutting cylinder 22 is being rotated. The distal end of the closing catheter 50 is also shown in FIG. 1. The closing catheter cylinder 52 surrounds the torqueing cylinder 44 of the cut/collect catheter. A passageway 54 is formed between the outer surface of the torqueing cylinder 44 and the inner surface of the closing catheter cylinder 52. Solutions such as contrast media or medication can be injected at the proximal end of the closing catheter 50 (see FIG. 3) and that liquid will then enter an artery or other body vessel through one or more vent holes 56 at the distal end of the closing catheter 50. Connected to the distal end of the cylinder 52 is a metal tip or plug 58. This plug has a cylindrical proximal end portion connected to the distal end of the cylindrical catheter 52 and a tapering distal end or nose portion that engages into and seals the open end of the tissue collection chamber 28, and when so engaged the tapering nose of the plug makes contact with the cutting end of the cutting cylinder 22 around a full circle 25, shown in Figure 1a. The outer surface of the cylindrical proximal end portion of the plug has a diameter that is approximately equal to the external diameter of the cylindrical cutting head 22, so that when the catheter system is inserted into or withdrawn from the lumen of the artery A (see Figure 5) before and after the excision of the stenotic plaque P, respectively, that cylindrical surface of the plug engages the wall of the artery and serves to space the cutting edge 24 of the cutting cylinder 22 a small distance from the interior wall of the lumen, thus to further prevent the cutting edge damaging the wall of the lumen during the insertion and withdrawal of the cutting head. As shown in enlarged detail in Figure 1a the tapered distal end portion of the metal tip 58 provides a tapered conical surface 58a which has a smaller apex angle as compared to the apex angle of the cone 22a on the inner surface at the proximal end of the cutting cylinder 22. This construction prevents the edge 24 from coming in contact with the metal tip 58. Thus the edge 24 is not made dull by contacting the metal tip 58. This assures that the tissue collection chamber 28 can be closed off thus securing the excised tissue within, yet, the device can be used repeatedly without dulling the cutting edge 24. An alternative design (not shown) would be to have a plastic end for the cylinder 52 into which the edge 24 could be imbedded without becoming dull. Figure 2, a transverse cross section at position 2-2 of Figure 1, shows the detail of the two fluid passageways 34, the lumen 32 and the connection of the support 30 to the cutting cylinder 22. Figure 3 is a partial cross section of the proximal end of the ETEC system 10. To the left in Figure 3 is shown a cross section of the torquing catheter 44 having an interior lumen 46 and the closing catheter cylinder 52. A plastic Luer fitting 51 is moulded onto the proximal end of the catheter 52. The two finger wings 53 are available to prevent rotation of the fitting 51 when the nut 55 is tightened. The nut 55 and sealing gland 57 are part of a Touhy-Borst fitting 58 which is used to seal off the proximal end of the passageway 54. A side-port 63 in the Touhy-Borst fitting 58 allows a syringe (not shown) to be connected for distally injecting contrast media through the distal vent hole(s) 56. Either a check valve or a single-port or a multiple-port stop cock can be connected at the side-port 63 to seal off the back flow of blood when the distal end of the ETEC 10 is placed in an artery. The sealing gland 57 in the Touhy-Borst fitting 58 seals against the outer surface of the torqueing cylinder 44. A Luer fitting 60 with two finger wings 62 is molded onto the proximal end of the torqueing cylinder 44. Since there is a passageway through the center of the entire ETEC 10, a guide wire can be inserted through the proximal end of the fitting 60 and then can be advanced until the distal end of the guide wire passes through the flexible tip 36 (see FIG. 1). Thus, a guide wire (as shown partially in FIG. 5) can first be advanced within the lumen of a human (or animal) vessel and the entire ETEC system 10 can then be advanced over the guide wire to that site in the vessel where tissue is to be excised. As seen in FIG. 3 the proximal end of the ETEC 10 is designed so that there is a gap G between the proximal surface 59 of the Touhy-Borst fitting 58 and the distal surface 61 of the Luer fitting 60. This gap G determines the maximum distance that the cutting edge 24 of the cut/collect catheter 20 (see FIG. 5) can be separated from the metal tip 58 of the closing catheter 50. This gap G would typically be between 1 and 30 mm long. FIG. 4 shows a rotator 70 which has a case 71 which encloses a battery 72 and a d-c motor-gear reducer assembly 73. When the switch 82 on top of the case 71 is pressed, the battery is electrically connected to the motor assembly 73 which causes rotation of the motor shaft onto which is mounted the small spur gear 74 which in turn rotates the large spur gear 75 which is mechanically joined to the rotating tube 76. The rotating tube 76 is attached at its distal end to a Luer fitting 79 which can be securely connected to the Luer fitting 60 (Figure 3) located at the proximal end of the cut/collect catheter 20. When connected, these fittings provide a mechanical connection which is also a fluid seal. At its proximal end, rotating tube 76 nests into a rear cylinder 77 which does not rotate. The proximal end of the cylinder 77 has a sealing gland 78 that seals against the guide wire 80 to prevent the distal top of the guide wire 80 from whipping around in the vessel when the cut/collect catheter 20 is being rotated. As can be seen in Figure 4, the guide wire passes through the entire length of the rotator 70 as well as extending through the entire length of the ETEC 10. The torque vs rotational speed curve of the rotator is such that at essentially zero torque, the rotating cylinder 76 (and therefore the cut/collect catheter 20) would rotate at approximately a resistive torque, as would be experienced when it cuts through highly calcified plaque or when the edge 24 engages the metal tip 58, the rotation rate slows considerably. The slower rotation rate is detected by the ETEC operator as a decreased audible tone which indicates that the cut is completed or that there is more resistive torque being experienced by the cutting edge 24. This feature of a detectable audible tone which depends upon the resistive torque provides valuable information to the operator when performing tissue excision from a vessel. Figure 5 shows the excision catheter system of Figure 1 in the open position and with the distal end of the cut/collect catheter 20 advanced over a guide wire 80 beyond a stenotic plaque P within a human artery A. Figure 5 shows the cutting edge 24 of the cylinder 22 being pulled back into the plaque P. During pullback, the cutting cylinder 22 could typically be rotated at approximately 2000 RPM while the closing catheter is not rotated. Thus, for most of the length of the ETEC 10 within the vessel, there is no rotating friction of any catheter outer surface against the vessel wall. This reduces the trauma to the vessel wall during the tissue excision procedure. The metal cannula 40 is somewhat longer than the gap G as shown in FIG. 5. Thus, even a curved vessel will tend to be straightened within the gap G. Thus, as the cutting edge 24 is being pulled back toward the metal tip 58, this vessel straightening effect will tend to reduce the probability of perforating the vessel wall during the excision procedure. The cutting cylinder 22 is typically made from a hardened stainless cutlery steel such as Type 455. The remaining metal parts of ETEC 10 are typically made from a stainless steel such as Type 304 or 316. The plastic parts of the ETEC 10 are typically Nylon, or polyurethane or polyethylene, or other materials having similar properties. The method for performing the tissue excision is as follows: (1) The ETEC system with the cutting edge 24 held tight against the metal tip 58 and with the Touhy-Borst fitting 58 tightened would be advanced over a percutaneously inserted guide wire until the cutting edge 24 is advanced beyond the tissue to be excised. (2) The fitting 58 is then loosened and the closing catheter 50 is pulled back until the full gap G (see FIG. 5) is realized, i.e., the proximal end 59 of the fitting 58 is in contact with the distal end 61 of the Luer fitting 60. (3) The rotator 70 is advanced over the guide wire 80 and the Luer fitting 79 of the rotator 70 is attached to the Luer fitting 60 of the cut/collect catheter 20. (4) The rotator gland 78 is then tightened around the guide wire 80. (5) The rotator 70 is then turned on and simultaneously pulled back until the edge 24 is in contact with the metal tip 58. (6) The rotator 70 is then promptly turned off; the gland 78 is loosened and then the fitting 79 of the rotator 70 is disconnected from the Luer fitting 60, and the rotator 70 is pulled off the guide wire 80. (7) The gland 57 is then tightened and the ETEC 10 is pulled over the guide wire 80 and out of the living body. (8) The gland 57 is then loosened the closing catheter 50 is pulled back and a syringe (not shown) is then connected to the Luer fitting 60 while a finger is placed over the distal end of the flexible tip 36. (9) Fluid is then firmly squirted into the lumen 46 of the cylinder 44 which forces the collected tissue to be pushed out of the tissue collection chamber 28. The tissue thus collected can then be histologically examined. If there is a particularly long length of tissue to be excised from within the vessel, instead of merely pulling the cutting edge 24 back until it touches the stationary metal tip 58, the entire ETEC 10 can be pulled back while maintaining a fixed gap G between the cutting edge 24 and the metal tip 58. Once the desired length has been transversed by ETEC 10, then the metal tip 58 can be held fixed relative to the vessel while the cutting edge 24 is pulled back to it. This final closure provides containment of the cut tissue within the collection chamber 28. Although most of the discussion herein concerns the excision of plaque from a human artery, the design of the ETEC system is such that it is well suited to excise tissue from a variety of vessels from within a living body, for example for the purpose of biopsy. In one such use, the ETEC system could be advanced over a guide wire into a bile duct and there it could be used to obtain a tissue sample for biopsy. Further, excision of tissue from the urethra, ureter, fallopian tubes or other vessels of a living body could be readily accomplished with the ETEC system. Still further ETEC could be used to simultaneously remove thrombus and plaque in an early stage of myocardial infarction thus opening a clogged coronary artery for the free flow of blood. An anti-thrombogenic agent such as tPA could simultaneously be injected into the artery through the vent holes at the distal end of the closing catheter in order to efficiently dissolve any residual thrombus. The ETEC system could also be used to remove plaque that has been dissected off the wall of an artery subsequent to balloon angioplasty. Such action could readily be used to open a clogged artery and preclude the necessity for vascular surgery. Various other modifications, adaptions, and alternative designs are of course possible in light of the above teachings without departing from the scope of invention herein described and hereinafter claimed. In so far as the trade names Luer and Touhy-Borst used herein are or may be registered in one or more of the EPC member states designated in this application, then they are hereby acknowledged as being "Registered Trade Marks".

Claims: An excision catheter for excising tissue from within the lumen of a tubular vessel within the human or animal body, the catheter comprising a first tubular catheter member (20) advanceable into the tubular vessel over a guide wire (80) preinserted therein, said first catheter member carrying at its distal end a rearwardly open, hollow, rigid cylindrical cutting head (22) advanceable into the tubular vessel to a location situated beyond the tissue to be excised, said cutting head (22) having a rearwardly directed circular cutting edge (24) at its proximal end and rearwardly open inner chamber (28) for the collection of tissue excised from the lumen of the tubular vessel as the catheter is retracted back through the vessel in the opposite direction to the direction of insertion, a tubular, sheathing catheter member (52) coaxially sheathing the first catheter (20) and carrying at its distal end a plug member (58) which is engageable in the proximal end of the tissue collection chamber (28) so as to close the tissue collection chamber (28) in the cutting head (22) prior to the withdrawal of the catheter and cutting head (22) from the tubular vessel, but after the said retraction of said cutting head (22) through said tissue, and thereby to seal the excised tissue in the collection chamber (28) characterised in that the plug (58) on the distal end of the sheathing catheter member (52) has a cylindrical proximal portion connected to the distal end of the sheathing catheter and a conical distal end or nose portion which tapers to a minimum diameter at the distal end of the plug, that minimum diameter being less than the diameter of the cutting edge (24) and the diameter of the cutting edge being less than that of the cylindrical proximal portion of the plug so that the distal end of the plug can be engaged in the rearwardly open end of the tissue collection chamber (28) and when so engaged the tapered surface of the plug engages the proximal end of the cutting head (22) around its full circumference with said cylindrical proximal portion of the plug serving to space the cutting edge from the interior wall of the lumen. An excision catheter according to claim 1, wherein the open end of the cylindrical cutting head (22) is chamfered (22a) to provide an annular rearwardly cutting edge (24) surrounding the open end of the cylinder. An excision catheter according to claim 2, wherein said plug (58) is a metal tip mounted on the distal end of the sheathing catheter (57) and wherein the angle of taper of the nose portion of the plug (58) is different from the angle of chamfer of the cutting edge (24) so as to prevent engagement of the cutting edge (24) with the metal plug (58) and consequent dulling of the cutting edge. An excision catheter according to claim 1, wherein the said plug (58) on the distal end of the sheathing catheter member (52) is of plastics material into which the cutting edge (24) of the cutting head (22) can be embedded without dulling of the cutting edge. An excision catheter according to any one of claims 1 to 4, wherein one or more passageways (34) is or are provided between the interior of said collection chamber (28) and the lumen (32) of the first catheter member (20) to permit flushing of the collected tissue from the collection chamber (28) after withdrawal of the catheter from the body. An excision catheter according to any one of claims 1 to 5, wherein the cutting head (22) carries an elongated hollow flexible tip (36) to ensure better tracking of the catheter over the guide wire (80) during insertion into the body. An excision catheter according to any one of claims 1 to 6, wherein the first catheter member (20) and the sheathing catheter member (52) are spaced one from the other to provide an annular passageway (54) for the passage of a contrast fluid or other fluid medium into the tubular vessel through exit ports (56) provided in the distal end of the sheathing catheter. An excision catheter according to claim 7, including a check valve or stop cock at the proximal end of the sheathing catheter member (52) to prevent back flow of blood or other body fluids through said annular passageway (54). An excision catheter according to any one of claims 1 to 8 including gap control means which limit the distance that the sheathing catheter member (52) can be retracted relative to the first catheter member (20) in order to expose the cutting edge (24) of the cutting head (22). An excision catheter according to any one of claims 1 to 9, wherein the cutting head (22) is non-rotatably mounted on the first catheter member (20) which is a torque transmitting catheter rotatably mounted in the sheathing catheter member (52), and rotary drive means (70) are provided connectable to the proximal end of the torque transmitting catheter (20) to rotate the cutting head (22) during the excision of said tissue. An excision catheter according to claim 10, wherein the rotary drive means (70) emits an audible tone which varies with the speed of rotation of the cutting head. An excision catheter according to claim 11, wherein said audible tone decreases in pitch with decreasing speed of rotation of the cutting head. An excision catheter according to claim 10, 11 or 12, wherein the rotary drive means (70) connectable to the proximal end of the torque transmitting catheter (20) has a passageway extending therethrough permitting the rotary drive means (70) to be threaded on the proximal end of the guide wire (80) for connecting the rotary drive to the torque transmitting catheter. An excision catheter according to claim 13, wherein the rotary drive means (70) comprises means (78) for gripping the guide wire (80) when threaded thereon to prevent the wire (80) from rotating as the rotary drive is operated.

Inventors: FISCHELL ROBERT E, FISCHELL TIM A, FISCHELL, ROBERT E., FISCHELL, TIM A.
Applicants: FISCHELL ROBERT, FISCHELL TIM A, FISCHELL, ROBERT E., FISCHELL, TIM A.
Application year: 1990
Main classification: A61B17
IPC codes: A61B17, A61M25