Rotary catheter for atherectomy system

Abstract: An atherectomy system (10) insertable into a human blood vessel (12) over a flexible guide-wire (17) for remotely cutting and removing an obstruction (15) therein, having a diametrical stabilized torque transmitting flexible rotary-catheter (19) equipped with a rotary coring means (22) at its distal end and a motor (24) connected to its proximal end.

Description: This invention relates to an atherectomy system. With age a large portion of the population develops arterial obstructions formed by fats, fibrous material and calcified deposits, resulting in a diminished blood circulation. These obstructions can induce blood clots which further diminish or block the blood flow. When this occurs in the coronary arteries serving the heart muscles it is referred to as a heart attack. Presently such obstructions are bypassed with a graft or they are treated by angioplasty using a catheter equipped with a balloon which is inserted, over a flexible guidewire, into the obstruction through the arterial system and then inflated to dilate the obstructions lumen. Problems with this treatment are that it injures the arterial wall and may burst it. In certain cases it is ineffective. It creates a rough lumen. It does not remove the obstructing material out of the vascular system and may even release obstruction material into the vascular system. Thus, angioplasty during a heart attack carries the risk of dislodging particles of the blood clot and allowing it to move down stream creating further, potentially critical, damage. EP-A-254414 discloses an atherectomy system insertable into a human blood vessel for coring and removing an obstruction therein comprising a flexible guidewire insertable into said blood vessel, a flexible rotary catheter having a continuous passage therethrough rotatably disposed and slidable over said flexible guidewire, said flexible rotary catheter having proximal and distal ends, a rotary coring means for cutting and ingesting obstruction material located at said distal end, a coupling means for rotating said flexible rotary catheter around said flexible guidewire located at said proximal end, means for diametrically stabilizing the flexible rotary catheter comprising a series of hoop members, and means for transmitting torque, said hoop members and the means for transmitting torque together forming a skeleton for said rotary catheter. EP-A-358825 also discloses an atherectomy system with a rotary catheter. However, it does not have a torque limiting clutch to protect the system and artery from various uncontrollable variations which can alter the torque transmission distribution pattern during an operating procedure. An objective of the present invention therefore is to provide a flexible torque transmitting rotary catheter for an atherectomy system which can be percutaneously or intra-operatively introduced into the vascular system for cutting and removing an obstruction therein. The flexible rotary catheter is insertable and rotatable over a flexible guidewire and transmits rotation and torque to rotary coring means at its distal end from a motor affixed to its proximal end. A further object of the present invention is to provide a flexible rotary catheter which will positively remove from the human body the obstruction material, including blood clots if present, while creating a smooth lumen, and minimizing injury to the blood vessels wall. A further object is to provide a system that can be used during a heart attack to provide immediate relief and a long term correction of the diseased arterial site. The flexible rotary catheter should lend itself to be producable in diameters down to around 1mm (millimeter) and a length of around a meter to be able to reach and enter small and remote blood vessels. Preferably, the procedure using the atherectomy system would resemble angioplasty so that present skills of the medical staff can be utilized. The flexible rotary catheter should be simultaneously flexible and capable of transmitting torque so that when it is introduced percutaneously to treat an obstruction in a remote artery, for example a coronary artery, it can assume a tortuous path of the vascular system including some sharp turns found in the coronary vascular system. The present invention overcomes the problems of the prior art by providing a series of connecting members to interconnect the hoop members to provide the means for transmitting torque and by providing a torque limiting clutch incorporated between the proximal large diameter and distal small diameter sections of said flexible rotary catheter. These and other objects of the invention will become apparent from the following description of preferred embodiments by way of example only with reference to the accompanying drawings. FIGURE 1 is a general view of an atherectomy system being inserted into an obstructed human coronary artery. The atherectomy system is introduced into the vascular system percutaneously at the groin area and is snaked through the arterial system to reach the work site where the obstruction is about to be removed; FIGURE 2 is a cross sectional view of the proximal and distal ends of the atherectomy system with its distal end inserted into an obstructed coronary artery. The general positioning of the parts corresponds to their position in Figure 1. Due to space limitations on the drawing sheets a segment or segments of the atherectomy system and flexible rotary catheter are omitted and in Figure 2 the mid section of the system is represented by a phantom line; FIGURE 3 is a partially sectioned view of a first embodiment of a flexible rotary catheter; FIGURE 4 is a skeleton member of the flexible rotary catheter of the first embodiment in its flat position before it has been rolled to form the intermittent tube shown in Figure 3; FIGURE 5 is an end view of the first embodiment viewed along line 5-5 marked on Figure 3; FIGURE 6 is a cross sectional view of the first embodiment as viewed along line 6-6 marked on Figure 3; FIGURE 7 is a cross sectional view of the first embodiment as viewed along line 7-7 marked on Figure 3; FIGURE 8 is a partially sectioned view of a second embodiment of a flexible rotary catheter; and FIGURE 9 is a cross sectional view of the second embodiment as viewed along line 9-9 marked on Figure 8. Figure 1 shows a general view of an atherectomy system 10 which is percutaneously introduced into a human femoral artery 11 at the groin area, and its distal end is snaked through the arterial system to reach a work site in a coronary artery 12. Figure 2 shows an enlarged cross sectional view of a proximal end 13 and of a distal end 14, of the system 10. The distal end is inserted into the diseased coronary artery 12 (as shown in Figure 2 the atherectomy system comprises several elongated parts in a nested relationship, and their ends shall be referred to as "distal" meaning the end which goes into the vessel and "proximal" meaning the other end, thus, "distal direction" or "distally" shall indicate a general direction from the proximal end to the distal end, and "proximal direction" or "proximally" shall refer to an opposite direction. It should also be noted that the same numbers are used to indicate the same items through the Figures) containing a blood clot 15' seated on an atherosclerotic obstruction 15. The mid portion of the atherectomy system is represented by a phantom line 16. The system 10 comprises a flexible guidewire 17 having a section at its distal end shaped as an auger 18. The flexible guidewire is designed to be insertable through the human vascular system. A flexible rotary catheter 19 has a wall 20 defining a longitudinal channel 21. The catheter 19 is rotatable and slidable over the flexible guidewire 17. A rotary coring means in the form of a tubular blade 22 is located at the distal end of the flexible rotary catheter 19. The tubular blade 22 defines a through hole 23 which forms with the channel 21 a continuous passage for accepting the obstruction material ingested into the through hole (the term rotary coring means as used herein refers to a tubular blade with a smooth or toothed cutting edge, as shown in the drawings accompanying this application or to coring means such as a blade with inwardly bent teeth or to a heated tubular blade, an expandable tubular blade or a radiation emitting blade. Some of these rotary coring means are incorporated into, or are part of, the distal end of the flexible rotary catheter and have no discrete internal wall of their own, in which case the continuous passage consists of the channel 21). A motor 24 has a hollow tapered shaft 25 which couples it to the proximal end of the flexible rotary catheter through a matching tapered seat 30 for rotating it around the flexible guidewire 17. A sleeve 26 introduces the flexible rotary catheter into the vascular system and may be extended distally to separate the arterial wall from the rotating catheter and to deliver contrast and/or irrigating fluid to the work site. The sleeve 26 may be formed to a desired shape and serve as a guiding catheter and assist in guiding the system through the vascular system to the work site. A port 27 is provided to accept fluids for delivery through the sleeves distal end and a seal 31 prevents the fluids from escaping out of the proximal end of the sleeve. A rotary joint 28 has a port 29 which is connected through the hollow shaft 25 to the channel 21 and can be used for delivering fluids to the work site or for creating a negative pressure in the channel 21 to assist in drawing the obstruction material proximally. The flexible guidewire slidably passes through a close fitting hole formed at the proximal end of the rotary joint 28. Figure 3 shows a first embodiment of a flexible rotary catheter 33 having means for diametrical stabilization of the flexible rotary catheter while transmitting torque and being bent, as for example when cleaning an obstruction located in the coronary arteries illustrated in Figure 2. The diametrical stabilizing means is in the form of a series of hoop members 34 connected one to the other by the torque transmitting means in the form of strips 35. Collectively the hoops 34 and strips 35 form a skeleton of the flexible rotary catheter on which a plastic wall 38 is formed to define a channel 39. Figure 4 shows a shape cut out of a flat thin material such as stainless steel sheet, including horizontal strips 34' interconnected by the inclined strips 35. At a later stage the horizontal strips 34' are folded and their ends bonded, or welded, to form the diametrical rigid hoops. As shown in Figure 5 the ends of the strips 34' can be made to butt and bond along the inclined line 40 to avoid local double thickness of the hoop at the point of connection. The hoops rigidity can be enhanced by giving them a slight arced cross section as shown in Figure 3. The thin strips 35 bend easily, but only in one direction, therefore they are phased at third of a circle intervals, as shown in Figure 3 so that every three consecutive hoops act as a miniature universal joint that can bend in any direction while transmitting rotation and torque. During the manufacturing process, while the material is still flat, as shown in Figure 4, it can be readily access with tools and dies, and straight or inwardly bent teeth or paddles 52 can be relatively easily fabricated in it. The paddles can be formed by cutting a rectangular slot 53 along three of its sides and bending the material inwards around the fourth side which is left intact. The paddles 52 assist in pulling the obstruction material proximally in the flexible rotary catheter 33 by turning the cut obstruction material that enters the through hole around the stationary auger, and also by being inclined themselves the paddles operate as inclined planes to move the material proximally in the flexible rotary catheter 33. The coring action which takes place at the distal end of the flexible rotary catheter requires a certain amount of net torque and rotation, however, due to frictional losses along the length of the flexible rotary catheter the gross torque that is required at its proximal end is substantially larger than the net torque. To withstand the gross torque the shaft may be strengthened by, as shown in Figure 4, horizontal strips 36 and vertical strips 37 being made longer and wider, respectively, increasing the flexible rotary catheter diameter (see Figure 3) and torque transmitting capacity (from hereon the distal small diameter and proximal larger diameter sections of the flexible rotary catheter will be referred to as the neck and shaft sections, respectively). Since the shaft is often disposed in relatively straight arteries, its increased stiffness is acceptable. To further protect the system and the artery from various unpredictable and uncontrollable variations that may occur during an individual procedure (such as changes in coefficient of friction between the rotating parts of the system and the stationary parts of the system or of the artery, or changes in the forces inducing the friction which may occur due to misalignment of parts of the system, or a spasm in the artery which may lock the artery onto the flexible rotary catheter and alter the pattern of torque distribution along the flexible rotary catheter) a torque limiting clutch is incorporated between the shaft and the neck. Figure 8 shows a second embodiment of a flexible rotary catheter 88 wherein the hoop members are a few closely spaced windings 41 connected one to the other by a widely spaced partial winding 42. The closely spaced windings 41 can be brazed together to increase their diametrical stability. The widely spaced partial windings 42 serve to transmit torque from one hoop to the other and increase the flexibility of the rotary catheter. The windings 41,42 and 48 (which is the continuation of the windings in the shaft section) form a skeleton to which a rotary coring means, in the form of a tubular toothed blade 43, is brazed. The flexible rotary catheter 88 comprises a neck section which extends from the blade 43 down to a point 44 at which point the rotary catheter diameter increases to form a shaft section 45 with an increased torque transmitting capacity. A plastic wall 46 is formed to complete the flexible rotary catheters structure and define a channel 49 therein. The fact that the skeleton of the second embodiment is made of a continuous wire simplifies the handling and fabrication of the flexible rotary catheter, however, notwithstanding this, individual hoop members can be used to stabilize the flexible rotary catheters diameter in which case the plastic wall itself transmits the torque. The present invention provides the physician with a method to immediately and effectively intervene in what is often referred to as a "heart attack" which is commonly caused by an obstruction made of a soft fresh blood clot formed on an atherosclerotic plaque which has developed for several years. Currently, the presence of the fresh blood clot, which has jelly like consistency, deters angioplasty since angioplasty may dislodge and release downstream some of the blood clots material causing additional arterial occlusions possibly at points which would be more difficult to treat or points where no alternate blood supply exists (at the point of the original obstruction, being an "old" obstruction, alternate blood supply may have developed). Currently, several pharmacologic treatments are being tested that dissolve the blood clot, after which angioplasty may be performed, however, because the present invention is effective in releasing and removing blood clots as well as atherosclerotic plaque it circumvents the delay and added risks that the pharmacologic treatment introduces, such as for example bleeding elsewhere. The process for removing an obstruction made of a soft blood clot 15' formed on an atherosclerotic plaque from a blood vessel 12, comprises the following steps: inserting into the blood vessel a flexible guidewire 17 and advancing it into the blood clot 15' which formed on the obstruction 15, inserting into the blood vessel, over the flexible guidewire, the flexible rotary catheter 19 having a proximal end 13 and a distal end 14 with a rotary coring means affixed thereto, advancing the distal end 14 to mechanically engage and unseat the blood clot 15' while applying suction to port 29 to suck the blood clot 15' into the through hole 23, advancing the rotary coring means to rotatably engage and cut the atherosclerotic plaque of the obstruction 15, removing the system with the blood clot and the atherosclerotic plaque out of the blood vessel 12.

Claims: An atherectomy system (10) insertable into a human blood vessel (11) for coring and removing an obstruction therein, comprising: a flexible guidewire (17) insertable into said blood vessel (11); a flexible rotary catheter (19) having a continuous passage therethrough rotatably disposed and slidable over said flexible guidewire (17), said flexible rotary catheter having proximal and distal ends (13,14); a rotary coring means (22) for cutting and ingesting obstruction material located at said distal end; a coupling means (25) for rotating said flexible rotary catheter (19) around said flexible guidewire (17) located at said proximal end, means for diametrically stabilizing the flexible rotary catheter comprising a series of hoop members (34), and means for transmitting torque, said hoop members (34) and the means for transmitting torque together forming a skeleton for said rotary catheter characterised in that said means for transmitting torque comprise a series of connecting members (35) interconnecting the hoop members (34) and a torque limiting clutch is incorporated between the proximal large diameter and distal small diameter sections of said flexible rotary catheter. An atherectomy system as claimed in claim 1 characterised in that said flexible rotary catheter is rotatably disposed in a sleeve (38). An atherectomy system as claimed in claim 1 or claim 2 characterised in that each torque transmitting connecting member is a strip member (35). An atherectomy system as claimed in claim 3, characterised in that the hoop members (34) are rolled horizontal strips (34') connected one to the other by the torque transmitting strip members (35). An atherectomy system as claimed in claim 3, characterised in that the hoop members (34) are closely spaced windings (41) and the connecting members which connect them together are widely spaced windings (42). An atherectomy system as claimed in any preceding claim characterised by a plastic wall (38) defining a fluid worthy channel through said flexible rotary catheter. An atherectomy system as claimed in claim 6 characterised in that said plastic wall (38) contains the means for diametrically stabilizing the flexible rotary catheter. An atherectomy system as claimed in any preceding claim characterised in that the rotary coring means is an integral part of the means for diametrically stabilizing said flexible rotary catheter. An atherectomy system as claimed in any preceding claim characterised in that the rotary coring means is an integral part of said means for transmitting torque.

Inventors: SHIBER SAMUEL, SHIBER, SAMUEL
Applicants: SHIBER SAMUEL, SHIBER, SAMUEL
Application year: 1990
Main classification: A61B17
IPC codes: F16D7, A61B19, A61B17, F16C1, A61B18