Patent Publication Number: US-2013245654-A1

Title: Atherectomy device supported by fluid bearings

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 13/438,282 filed on Apr. 3, 2012, which is a continuation of U.S. patent application Ser. No. 12/373,461 filed on Jan. 12, 2009, which is a national phase application based on PCT/EP2007/056499 filed on Jun. 28, 2007, which claims priority to GB Patent Application No. 0613979.4 filed on Jul. 13, 2006. The contents of these prior applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present invention provides a rotational atherectomy device for removing a stenotic lesion from within a vessel of a patient. More specifically, the invention relates to a rotational atherectomy device for removing or reducing stenotic lesions in blood vessels such as a human artery by rotating an abrasive element within the vessel to partially or completely ablate the unwanted material. 
     2. Description of Related Art 
     Atherosclerosis, the clogging of arteries, is a leading cause of coronary heart disease. Blood flow through the peripheral arteries (e.g., carotid, femoral, renal, etc.), is similarly affected by the development of atherosclerotic blockages. A conventional method of removing or reducing blockages in blood vessels is known as rotational atherectomy. A long guidewire is advanced into the diseased blood vessel and across the stenotic lesion. A hollow drive shaft is then advanced over the guidewire. The distal end of the drive shaft terminates in a burr provided with an abrasive surface formed from diamond grit or diamond particles. The burr is positioned against the occlusion and the drive shaft rotated at extremely high speeds (e.g., 20,000-160,000 rpm). As the burr rotates, the physician slowly advances it so that the abrasive surface of the burr scrapes against the occluding tissue and disintegrates it, reducing the occlusion and improving the blood flow through the vessel. Such a method and a device for performing the method are described in, for example, U.S. Pat. No. 4,990,134 to Auth. It is also known from U.S. Pat. No. 6,132,444 to Shturman (the instant inventor) et al, to provide a drive shaft with an abrasive element eccentrically positioned proximally to and spaced away from the distal end of the drive shaft. 
     Rotational angioplasty (atherectomy) is frequently used to remove atherosclerotic or other blocking material from stenotic (blocked) coronary arteries and other blood vessels. However, a disadvantage with this technique is that abraded particles can migrate along the blood vessel distally and block very small diameter vessels including capillaries of the heart muscle itself The effect of the particulate debris produced by this procedure is of major concern to physicians who practice in this field. Clearly, the existence of particulate matter in the blood stream is undesirable and can cause potentially life-threatening complications, especially if the particles are over a certain size. 
     Although the potentially detrimental effect caused by the presence of abraded particles in the blood vessels is reduced if they are very small microparticles, it is much more preferable to remove from the treated blood vessel any debris abraded or otherwise released from the stenotic lesion during treatment and thereby prevent migration of debris to other locations along the treated blood vessel. 
     A rotational atherectomy device, described in U.S. Pat. No. 5,681,336 (to Clement et al), has been proposed which attempts to prevent migration of abraded particles along the blood stream by removing the ablated material from the blood vessel whilst the device is in use. The rotational atherectomy device known from U.S. Pat. No. 5,681,336 (to Clement et al.) has a complicated construction and is difficult to manufacture on a commercial scale. 
     A number of disadvantages associated with the known rotational atherectomy devices have been addressed in WO 2006/126076, WO 2006/126175 and WO 2006/126176 to Shturman (the instant inventor). The present invention seeks to further improve rotational atherectomy devices known from these documents and other disadvantages associated with known atherectomy devices. 
     Two most preferred embodiments of the Rotational Atherectomy Device with Solid Support Elements are described in WO 2006/126076. Both embodiments comprise an abrasive element and a pair of solid support elements mounted to a hollow drive shaft formed from a torque transmitting coil and a fluid impermeable membrane. In both preferred embodiments, the abrasive element is located proximal to and spaced away from the distal end. The solid support elements described in WO 2006/126076 are rounded. One of them is located at the distal end of the drive shaft and is referred to as the distal solid support element. The other is located proximal to and spaced away from the abrasive element and is referred to as the proximal distal support element. 
     In one embodiment of the invention described in WO 2006/126076, the abrasive element has its centre of mass spaced away from the longitudinal or rotational axis of the drive shaft. In that embodiment, both the distal and the proximal solid support elements also have their centres of mass spaced radially away from the longitudinal or rotational axis of the drive shaft, the centre of mass of each of the two solid support elements being located diametrically opposite to the centre of mass of the abrasive clement with respect to the longitudinal axis of the drive shaft so that the distal and proximal solid support elements act as counterweights with respect to the abrasive element when the drive shaft rotates. Most preferably, the distal and proximal solid support elements are located in the same longitudinal plane as the centre of mass of the abrasive element, the longitudinal plane extending through the longitudinal or rotational axis of the drive shaft. 
     In another embodiment described in WO 2006/126076, the abrasive element and the solid support elements have their centres of mass coaxial with the longitudinal or rotational axis of the fluid impermeable drive shaft. 
     In both embodiments described in WO 2006/126076, pressurised fluid enters treated vessel only through a distal end opening of the fluid impermeable lumen of the drive shaft. 
     SUMMARY 
     According to the invention, there is provided a rotational atherectomy device for removing a stenotic tissue from a vessel of a patient, the device comprising a rotatable, flexible, hollow drive shaft having a distal end, an abrasive element mounted to the drive shaft proximal to and spaced away from a distal solid support element mounted at the distal end of the drive shaft, the distal solid support element having a rounded outer surface and comprising an outflow channel extending through the solid distal support element, the outflow channel having an outflow opening in said rounded outer surface, the drive shaft comprising a torque transmitting coil and at least one fluid impermeable membrane forming a fluid impermeable lumen for the antegrade flow of fluid along the torque transmitting coil into the outflow channel of the solid distal support element such that, during rotation of the drive shaft, said outflow opening of the outflow channel is facing an inner surface of a vessel being treated so that a flow of fluid out of said outflow opening forms a layer of fluid between the solid distal support element and a wall of the treated vessel, said layer of fluid forming a fluid bearing between the rotating solid distal support element and the wall of the treated vessel. 
     In a preferred embodiment, the fluid impermeable drive shaft is provided with a solid proximal support element located proximal to and spaced away from the abrasive element, the membrane that forms a fluid impermeable lumen for the antegrade flow of fluid along the torque transmitting coil into the outflow channel of the distal solid support element also forming a lumen for the antegrade flow of fluid along the torque transmitting coil into an outflow channel extending through said solid proximal support element, the solid proximal support element having a rounded outer surface, said outflow channel having an outflow opening in the rounded outer surface of the solid proximal support element such that, during rotation of the drive shaft, said outflow opening on the outer surface of the solid proximal support element is facing an inner surface of a treated vessel so that a flow of fluid out of said outflow opening forms a layer of fluid between the solid proximal support element and a wall of the treated vessel, said layer of fluid forming a fluid bearing between the rotating solid proximal support element and the wall of the treated vessel. 
     In one embodiment, the drive shaft preferably has a longitudinal axis and the solid distal support element has a centre of mass which is coaxial with the longitudinal axis of the drive shaft, said distal support element having a plurality of outflow channels that extend through the distal support element in a radially outward direction with respect to the longitudinal axis of the drive shaft and have their outflow openings spaced around the circumference of the solid distal support element such that, during rotation of the drive shaft, a flow of fluid through the outflow openings forms a layer of fluid between the solid distal support element and a wall of the vessel being treated, said layer of fluid forming a fluid bearing between the rotating solid distal support element and the wall of the vessel being treated. In this embodiment, the centre of mass of the abrasive element may either be coaxial with the longitudinal axis of the drive shaft or, spaced radially away from the longitudinal axis of the drive shaft. 
     In an embodiment where there is a solid proximal support element, the solid proximal support element may have a centre of mass coaxial with the longitudinal axis of the drive shaft, said proximal support element having a plurality of outflow channels extending through the solid proximal support element in a radially outward direction with respect to the longitudinal axis of the drive shaft and having their outflow openings located around the circumference of the solid proximal support element such that, during rotation of the drive shaft, a flow of fluid out of the outflow openings forms a layer of fluid between the solid proximal support element and a wall of the vessel being treated, said layer of fluid forming a fluid bearing between the rotating solid proximal support element and the wall of the vessel being treated. In this embodiment, the centre of mass of the abrasive element may either be coaxial with the longitudinal axis of the drive shaft or, spaced radially away from the longitudinal axis of the drive shaft. 
     In one embodiment, the solid distal support element may have its centre of mass spaced radially away from the longitudinal axis of the drive shaft in one direction so that it acts as a counterweight to the abrasive element, which has its centre of mass spaced radially away from the longitudinal axis of the drive shaft in a diametrically opposite direction. 
     In an embodiment in which the abrasive element has its centre of mass spaced radially away from a longitudinal axis of the drive shaft, the centres of mass of both distal and proximal solid support elements may be spaced radially away from a longitudinal axis of the drive shaft but in a direction diametrically opposite to the direction in which the abrasive element is spaced radially away from the longitudinal axis of the drive shaft so that the distal and proximal solid support elements act as counterweights to the abrasive element. 
     It will be appreciated that there may be a plurality of outflow channels in the solid distal support element in any of the embodiments of the invention. 
     It should be emphasized that the present invention covers two most preferred embodiments in one of which the solid support elements are asymmetrical with respect to the longitudinal axis of the drive shaft. In the other preferred embodiment, the solid support elements are symmetric with respect to the longitudinal axis of the drive shaft. However, it will be appreciated that, in all the embodiments, the asymmetric and symmetric solid support elements comprise outflow channels located such that, in the rotating drive shaft, fluid flowing out of said channels forms fluid bearings between outer walls of said solid support elements and the wall of the treated vessel. 
     It should be noted that throughout this specification, reference is made to “distal” and “proximal” ends and to flow of fluid in an “antegrade” and “retrograde” direction. For the avoidance of doubt, the distal end is considered to refer to the end of the device which is inserted into the vessel in the body of the patient and the proximal end is the end of the device which remains outside the body of the patient and which can be connected to a handle assembly for both rotating and longitudinally moving the drive shaft within the treated vessel. “Antegrade” flow refers to a direction of flow from the proximal towards the distal end of the device. Similarly, “retrograde” flow refers to a direction of flow in the opposite direction, i.e. from the distal towards the proximal end of the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates in a longitudinal cross-section a distal portion of one preferred embodiment of the rotational atherectomy device of the invention, this embodiment comprising asymmetric solid support elements and illustrating the location of outflow channels which extend through said solid support elements; 
         FIG. 2  illustrates the device of  FIG. 1  located in a vessel being treated and shows how the device can be used to abrade a stenotic lesion while forming fluid bearings between rounded outer surfaces of asymmetric solid support elements located distal and proximal to the abrasive element; 
         FIG. 3  illustrates in a longitudinal cross-section a distal portion of one preferred embodiment of the rotational atherectomy device of the invention, this embodiment comprising symmetric solid support elements located distal and proximal to the symmetric abrasive element and illustrates location of outflow channels which extend through said solid support elements; and 
         FIG. 4  illustrates the device of  FIG. 3  located in a vessel being treated and shows how the device can be used to abrade a stenotic lesion in a curved vessel. This Figure also shows how fluid bearings are formed between the rounded outer surfaces of symmetric solid support elements and the wall of the treated vessel. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIGS. 1 to 4 , the antegrade flow of fluid is indicated by arrows “FF” and the flow of fluid in a retrograde direction is indicated by arrows marked “R”. Abraded particles AP abraded from the stenotic lesion  330  are aspirated into a lumen of a drive shaft sheath  400  so that the retrograde flowing fluid and the abraded particles entrained in said fluid can be removed from the treated vessel and out of the patient&#39;s body. 
     Referring to the drawings, there is shown a rotational atherectomy device for removing a stenotic lesion from within a vessel of a patient using an abrasive element mounted to a rotatable, flexible, hollow drive shaft formed by a torque transmitting coil and a fluid impermeable membrane. The drive shaft has a longitudinal axis of rotation and is provided with two rounded solid support elements. Each of the two solid support elements is spaced away from the abrasive element and includes at least one outflow channel which is directed radially outward and communicates a lumen of the drive shaft with a vascular space of the treated vessel, one of said solid support elements is a distal solid support element and is located at a distal end of the drive shaft and the other is a proximal solid support element and is located proximal to the abrasive element. 
     In a preferred embodiment, each of the distal and proximal solid support elements has a rounded surface and is spaced equally from the abrasive element which extends around the entire circumference of the drive shaft. 
     In one embodiment of the invention the abrasive element and each of the two solid support elements are symmetric with respect to the rotational (longitudinal) axis of the drive shaft. In another embodiment of the invention the abrasive element and the solid support elements have their centres of mass spaced radially away from the rotational (longitudinal) axis of the drive shaft. 
     Each outflow channel has its own axis and each of the solid support elements has at least one outflow channel located such that its axis comprises an acute angle of at least seventy five (75) degrees with the longitudinal (rotational) axis of the drive shaft. In a preferred embodiment each of the solid support elements has at least one outflow channel located such that its axis comprises an angle of about (90) degrees with the longitudinal (rotational) axis of the drive shaft. In the most preferred embodiment of the invention each of the symmetric solid support elements has at least a few outflow channels equally spaced around the maximum circumference of the support element, each of said outflow channels having an axis which comprises an angle of about ninety (90) degrees with the longitudinal (rotational) axis of the drive shaft. In any of the preferred embodiments of the invention at least one outflow channel is located such that in a rotating drive shaft fluid which flows through the outflow channel along its axis forms at least a thin layer of fluid between the solid support element and the wall of the treated vessel. 
       FIG. 1  illustrates, in a longitudinal cross-section, a distal portion of one preferred embodiment of the rotational atherectomy device of an embodiment of the invention. The rotational atherectomy device is comprised of an asymmetric abrasive element  101  which extends around the entire circumference of the drive shaft  2  proximal to and spaced away from a distal end  6  of the drive shaft. The fluid impermeable drive shaft  2  is comprised by a fluid impermeable membrane  3  which lines a torque transmitting coil  4 . Both the torque transmitting coil  4  and the fluid impermeable membrane  3  extend distally beyond the abrasive element  101 . 
       FIG. 1  illustrates an asymmetric distal support element  10  which has its centre of mass spaced radially away from the longitudinal (rotational) axis W-W of the drive shaft  2 . The Figure illustrates that at least one outflow channel  20  which extends through a heavier portion  60  of the asymmetric distal support element  10 , the axis K-K of the outflow channel  20  comprises an acute angle a of about ninety (90) degrees with the longitudinal (rotational) axis W-W of the drive shaft. However, it will be appreciated that there may be a plurality of outflow channels  20  and the axes of these channels may form an acute angle of up to 30 degrees with axis K-K of the most important outflow channel. Its axis K-K being oriented perpendicular to the longitudinal axis of the drive shaft. In the most preferred embodiment of the invention, axis K-K of at least one outflow channel  20  passes through or close to the centre of mass of the asymmetric distal solid support element. 
       FIGS. 1 and 2  illustrate that a portion of flushing fluid FF flowing in an antegrade direction through the drive shaft  2  is redirected through the outflow channel  20  into a vascular space of the treated vessel. 
       FIG. 2  illustrates that in a rotating drive shaft centrifugal force attempts to press a rotating asymmetric solid distal support element  10  against the wall  300  of the treated vessel but fluid exiting through the outflow channel  20  along its axis K-K and forms an acute angle β of over 75 degrees with an inner surface of a wall  300  of the treated vessel so that fluid flowing through the outflow channel  20  forms a thin layer of fluid between the solid support element  10  and an inner surface of the treated vessel. This thin layer of fluid acts as a fluid bearing between the asymmetric distal solid support element  10  and a wall  300  of the treated vessel. At least a portion of fluid flowing through the outflow channel  20  flows in a retrograde direction, as indicated by arrows marked “R”, and entrains abraded particles AP removed from the stenotic lesion  330 . The retrograde flowing flushing fluid R and entrained abraded particles AP are aspirated into a lumen of the drive shaft sheath  400 . 
       FIG. 1  illustrates an asymmetric proximal support element  10   p  which has its centre of mass spaced radially away from the longitudinal (rotational) axis W-W of the drive shaft  2 . The Figure illustrates that at least one outflow channel  20   p  extends through a heavier portion  60   p  of the asymmetric proximal support element  10   p.  The outflow channel  20   p  has an axis L-L which forms an acute angle a of about ninety (90) degrees with the longitudinal (rotational) axis W-W of the drive shaft. However, it will be appreciated that there may be a plurality of outflow channels  20   p  and the axes of these channels may form an acute angle of up to 30 degrees with axis L-L of the most important outflow channel that has its axis L-L oriented perpendicular to the longitudinal axis of the drive shaft. 
       FIGS. 1 and 2  illustrate that a portion of flushing fluid FF flowing in an antegrade direction through the drive shaft  2  is redirected through the outflow channel  20   p  into a vascular space of the treated vessel. 
       FIG. 2  illustrates that in a rotating drive shaft centrifugal force attempts to press a rotating asymmetric solid proximal support element  10   p  against the wall  300  of the treated vessel but fluid exiting through the outflow channel  20   p  along its axis L-L forms an angle β of about ninety (90) degrees with an inner surface of a wall  300  of the treated vessel so that fluid flowing through the outflow channel  20   p  forms a thin layer of fluid between the solid support element  10   p  and an inner surface of the treated vessel. This thin layer of fluid acts as a fluid beating between the asymmetric distal solid support element  10   p  and a wall  300  of the treated vessel. 
       FIG. 3  illustrates a symmetric distal support element  10   s.  The centre of mass of the symmetric distal support element  10   s  coincides with the longitudinal (rotational) axis W-W of the drive shaft  2 . In a preferred embodiment of the invention at least a few outflow channels  20   s  should extend radially outward through the symmetric distal support element  10   s  communicating a fluid impermeable lumen of the drive shaft  2  with a vascular space of the treated vessel. Preferably said outflow channels  20   s  should be equally spaced around the maximum diameter circumference of the symmetric distal solid support element  20   s.    FIG. 3  illustrates that an axis M-M of at least one outflow channel  20   s  comprises an acute angle of over seventy five (75) degrees with the longitudinal (rotational) axis W-W of the drive shaft  2 . In the preferred embodiment axis M-M of the outflow channel  20   s  forms an angle a of about ninety (90) degrees with the longitudinal (rotational) axis W-W of the drive shaft. 
       FIGS. 3 and 4  illustrate that a portion of flushing fluid FF flowing in an antegrade direction through the drive shaft  2  is redirected through the outflow channels  20   s  into a vascular space of the treated vessel. 
       FIG. 4  illustrates that, in a curved vessel, the drive shaft  2  attempts to maintain its straight configuration and therefore attempts to press both of the solid symmetric support elements towards the outer curvature of the vessel and the symmetric abrasive element  102  towards the inner curvature of the vessel. 
       FIG. 4  illustrates that in a rotating drive shaft the axis M-M of the outflow channel  20   s  forms an angle β of about ninety (90) degrees with an inner surface of a wall  300  of the treated vessel so that fluid flowing through the outflow channel  20   s  along its axis M-M forms a thin layer of fluid between the solid support element  10   s  and an inner surface of the treated vessel. This thin layer of fluid acts as a fluid bearing between the solid support element  10   s  and a wall  300  of the treated vessel. At least a portion of the fluid flowing through the outflow channels  20  is flowing in a retrograde direction R and entrains abraded particles AP removed (abraded) by the symmetric abrasive element  102  from the stenotic lesion  360  located on the inner curvature of the vessel  300 . The retrograde flowing flushing fluid R is aspirated into a lumen of the drive shaft sheath  400 . 
       FIG. 3  illustrates a symmetric proximal support element  10   sp . The centre of mass of the symmetric proximal support element  10   sp  coincides with the longitudinal (rotational) axis of the drive shaft  2 . In a preferred embodiment of the invention at least a few outflow channels  20   sp should extend radially outward through the symmetric proximal support element  10   sp communicating a fluid impermeable lumen of the drive shaft  2  with a vascular space of the treated vessel. Preferably said outflow channels  20   sp  should be equally spaced around the maximum diameter circumference of the symmetric distal solid support element  20   sp .  FIG. 3  illustrates that an axis N-N of at least one outflow channel  20   sp  comprises an acute angle of at least seventy five (75) degrees with the longitudinal (rotational) axis W-W of the drive shaft  2 . In the preferred embodiment axis N-N of the outflow channels  20   sp  forms an angle a of about ninety (90) degrees with the longitudinal (rotational) axis W-W of the drive shaft.  FIGS. 3 and 4  illustrate that a portion of flushing fluid FF flowing in an antegrade direction through the drive shaft  2  is redirected through the outflow channel  20   sp  into a vascular space of the treated vessel. 
       FIG. 4  illustrates that in a rotating drive shaft the axis N-N of the outflow channel  20   sp  forms an angle β of about ninety (90) degrees with an inner surface of a wall  300  of the treated vessel so that fluid flowing through the outflow channel  20   sp  along its axis N-N forms a thin layer of fluid between the proximal solid support element  10   sp  and an inner surface of the treated vessel. This thin layer of fluid acts as a fluid bearing between the proximal solid support element  10   sp and a wall  300  of the treated vessel. 
       FIG. 3  illustrates an embodiment in which a fluid impermeable membrane lines the torque transmitting coil. In an alternative embodiment, illustrated in  FIG. 4 , the fluid impermeable membrane is disposed around the torque transmitting coil. 
     It will be appreciated that the device with symmetric support elements is not intended to be exclusively used in curved vessels but can also be used successfully in straight vessels. 
     Many modifications and variations of the invention falling within the terms of the following claims will be apparent to a person skilled in the art and the foregoing description should be regarded as a description of the preferred embodiments only.