Patent Publication Number: US-2019175206-A1

Title: Method and devices for using vibrational energy for cardiac lead removal

Description:
FIELD OF INVENTION 
     The present invention relates generally to methods and devices for use in separating an implanted cardiac lead from encapsulating tissue in the body of a patient. More particularly, the invention relates to devices with a vibrating tip/ring for ablating and separating tissue attached to leads, and for removing leads. 
     BACKGROUND OF THE INVENTION 
     Cardiac rhythm disorders such as atrial fibrillation, tachycardia or sudden cardiac arrest are often treated by stimulation therapy using cardiac pacing. Cardiac pacing systems typically include a timing device and a lead, which are placed inside the body of a patient. 
     One part of the system is the pulse generator containing electric circuits and a battery, usually placed under the skin on the wall of the chest beneath the collarbone. Another part of the system includes the wires, or leads, which run between the pulse generator and the heart. 
     In a pacemaker, these leads allow the device to increase the heart rate by delivering small timed bursts of electric energy to make the heart beat faster. In a defibrillator, the lead has special coils to allow the device to deliver a high-energy shock and convert potentially dangerous rapid rhythms (ventricular tachycardia or fibrillation) back to a normal rhythm. Additionally, the leads may transmit information about the heart&#39;s electrical activity to the pacemaker. 
     Cardiac pacemakers are typically implanted in a subcutaneous tissue pocket in the chest wall of a patient. A pacemaker lead extends from the pacemaker through a vein into a chamber of the patient&#39;s heart. The pacemaker lead commonly includes a conductor, such as an electrical wire/coil, for conducting electrical signals (such as stimulating and/or sensing signals) between the pacemaker and the heart. Leads for defibrillators are generally similar to pacemaker leads, and are positioned about the heart. Defibrillator leads may be affixed either internally or externally of the heart. 
     Within a relatively short time after a lead is implanted into the body, the body&#39;s natural healing process forms scar tissue and often calcifications along the lead. Although leads are designed to be implanted permanently in the body, over time these leads must be removed, or extracted due to numerous reasons, including but not limited to, infections, lead age, and lead malfunction. Therefore, removal of lead may be desirable and often necessary. 
     Removing an electrical lead from the heart, however, is not only expensive and time consuming, but poses numerous risks to the patient, such as injury to cardiac tissue and excessive bleeding. To avoid possible complications, some useless or otherwise inoperable cardiac leads are simply left in the patient when the pacemaker or defibrillator is removed or replaced. However, such a practice can incur the risk of an undetected lead thrombosis, which can result in stroke, heart attack, pulmonary embolism or infections. 
     Surgical removal of a heart lead may require open heart surgery which is accompanied by significant risk and cost to the patient, as well as a potential for unintended complications. 
     A variety of methods and apparatuses have been proposed as alternatives to open heart surgeries, and describe manual or mechanical devices that are used for removing an implanted cardiac lead. Others describe non-mechanical techniques, such as laser extraction or radio-frequency extraction. 
     Ultrasound energy has also been also proposed to remove leads. U.S. Pat. No. 6,241,691 (Tu et al.) discloses the use of a catheter with an ultrasound transducer tip where the transducer is located at the distal end of the catheter to ablate tissue at high frequencies above 1 MHz. 
     While the prior art devices have been found to be reasonably effective in removing leads surrounded by soft or scarred tissue, however, calcifications of the lead encapsulating tissue continue to be a challenge. It is difficult to cut calcified tissue by mechanical means such as rotating cutters or lasers. Ultrasound energy at frequencies above 100 kHz is also ineffective due to very small tip displacement and the creation of heat. In addition, lead removal using these less-invasive and non-surgical methods lacks a suitable or direct visualization when a lead is being separated or cut from a tissue. Even if the lead removal procedure is performed under x-ray, it is an intuitive approach without clearly seeing exactly what is being cut. 
     Considering the fact that almost 50% of the lead encapsulating tissue involves hardened tissue and calcifications, in some cases, physicians encounter particularly challenging myocardial perforations while removing lead, often causing internal bleedings. If such bleeding is not addressed quickly by a cardiosurgical team, it may result in patient death. Since the less-invasive procedures are typically performed by a cardiologist, handling such life-threatening myocardial perforation emergencies is outside of their skills and expertise, and require surgical repair. Also, patients with lead encapsulating calcific tissue must often undergo surgical procedure. 
     Many more lead removal procedures would be performed using less-invasive methods rather than surgery if new devices can safely ablate or separate lead encapsulating calcific tissue to further minimize or eliminate risk of myocardial perforations. Most of the less-invasive lead removal procedures are performed by a cardiologist, and handling such life-threatening myocardial perforation emergencies is outside of their expertise and require surgical repair. 
     Accordingly, there is a need for devices and methods that are capable of ablating, cutting or separating lead from the encapsulating calcific tissue while maintaining safety to a soft and healthy surrounding tissue. 
     SUMMARY OF THE INVENTION 
     Devices of the present invention to extract leads comprise a sheath assembly having a coaxial flexible tube that passes over the lead and/or the surrounding tissue. A cutting ring/tip is attached to the distal end of the sheath that may be vibrated and is aligned coaxially with the sheath. Upon advancement, the tip/ring cuts or separates the lead encapsulating tissue. 
     When the lead is encapsulated by soft tissue, the device of the present invention may be pushed distally around the lead to cut encapsulating tissue. In case the lead is encapsulated in a hardened calcific tissue, vibrational energy may be used to vibrate the ring/tip to further ablate calcifications and to facilitate lead separation from the encapsulating tissue. Once the lead is separated from the encapsulating tissue, it may be pulled by itself or by using a locking stylet outside the patient. 
     The vibrating cutting tip/ring of the present invention is capable of ablating hard tissue and calcifications, while providing safety to healthy tissue and promoting elasticity of soft tissue. This unique feature of using a vibrating cutting tip/ring for selective calcific tissue ablation, while leaving intact a healthy tissue, is utilized to separate leads from encapsulating tissue and may be helpful in reducing and minimizing myocardial perforations. If the vibrating cutting tip/ring faces a soft healthy myocardial tissue, it will not cut that tissue while still being capable of cutting and ablating hardened or calcific tissue that is encapsulating the lead. 
     Given the rising number of implanted transvenous pacemakers, ICDs, and CRT, transvenous lead extractions are going to be performed more frequently. To ensure safety and success, it is imperative to have better and safer devices, given the technical complexity and the risk of life-threatening complications that can arise. Old leads, calcifications, infections, and multiple leads make the procedure technically more difficult. Therefore, simplification of the lead removal procedure is another major objective of the present invention to avoid major complications and to ensure higher success rates. 
     “Vibrations” and ‘vibrational energy” have the same meaning and refer to physical vibrations of the tip/ring at the frequency range of 1 Hz to less than 1 MHz. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a lead extraction device according to one embodiment of the present invention. 
         FIG. 2  shows an alternative version of the lead extraction device with an inner sheath. 
         FIG. 3  illustrates the lead extraction device of  FIG. 1  introduced over the lead and positioned proximal to tissue that has encapsulated the lead. 
         FIG. 4  illustrates the lead extraction device positioned distal to the encapsulating tissue, and the lead separated from encapsulating tissue to be retrieved from the body. 
         FIG. 5  illustrates the ultrasound energy source as shown in  FIGS. 1  and  FIG. 3 . 
         FIG. 6  illustrates the ultrasound energy source as shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF DRAWINGS 
     The vibrational devices of the present invention are insertable into the human body and usable to deliver vibrational energy for the purpose of ablating obstructive material encapsulating cardiac leads. 
       FIG. 1  shows an overview of the lead extraction device  100  of the present invention. The lead extraction device  100  comprises a shaft  101  having a lumen  102 , a distal end  103  and a proximal end  104 . A tubular metallic tip/ring  105  or tip having an inner aperture  106  is positioned on the distal end  103  of the shaft  101  and aligned coaxially with the lumen  102  of the shaft  101 . A vibrational wire  107  having a distal end  108  and a proximal end  109  is extended longitudinally within the lumen  102 . The distal end  108  of the wire  107  is attached to the tip/ring  105  while the proximal end  109  of the wire  107  is extended outside the shaft  101  and provides connection to a vibrational energy source  110 . 
     A dual arm Y-connector  111  is attached to the proximal end  104  of the shaft  101 . The dual arm Y-connector  111  comprises a vibrational energy delivery port  112 , a lead exit port  113  and a suction port  114 . A secondary lumen  115  having a distal end  116  and a proximal end  117  is extended within the shaft  101  and houses the wire  107 . The distal end  116  of the lumen  115  is terminated at the vicinity of the tip  105 . The lumen  115  comprises a side connector  118  to receive cooling irrigant  119  that is to be delivered along the wire  107  during the delivery of vibrational energy from the vibrational energy source  110  to the tip/ring  105 . The cooling irrigant  119  exits at the distal end  116  of the lumen  115 . 
     The lead port  113  of the dual arm Y-connector is constructed as the exit for lead during lead removal. The suction port  114  of the dual arm Y-connector  111  is designated for aspiration of cooling irrigant  119  and any tissue or debris created during the lead removal and as described and shown in  FIG. 3 . The suction port  114  may be connected to any aspiration pump or any suitable syringe. A Tuohy-Borst adapter  120  is attached to the lead exit port  113  of the dual arm Y-connector  110  and provides an internal seal to aspirate cooling irrigant  119  and debris of cut tissue while proceeding with lead removal. 
     The shaft  101  of the lead removal device  100  may a flexible, pushable, and torqueable elongate body such that it is configured to be slid though the vasculature of the patient and around lead placed inside the body. The shaft  101  may be composed of a polymer or flexible metallic alloy and may include a plurality of slits along its surface for improving flexibility. 
     The tubular tip/ring  105  disposed at the distal end  102  of the shaft  101  is configured to mechanically cut tissue as it is pushed distally and/or when it is pushed and rotated. In addition, the tubular tip/ring  105  which is attached to the wire  107  may be vibrated by vibrational energy delivered via the wire  107  from the vibrational energy source  110  to the tip/ring  105 . The tip/ring  105  is made of metal or metal alloy including but not limited to SST, Titanium, Aluminum, Nitinol and other similar materials. The wire  107  may be made of metal or metal alloys including SST, Titanium, Nitinol and other similar materials. Two or more vibrational wires  107  may be attached to the tubular tip/ring  105  if needed (not shown). 
     The cutting tip/ring  105  is circumferential and may include a serrated or sharp continuous edge  121  which functions as a cutting element when it is pushed and/or rotated and/or vibrated. The tip/ring  105  may define an outer diameter that is the same as, or similar to, the outer diameter of the shaft  101  so as to be flush with the outer surface of the shaft  101 . 
     During the delivery of vibrational energy to the cutting tip/ring  105 , the tip/ring  105  will vibrate or move back and forth at the assigned frequency. It is desirable that longitudinal displacement of the cutting tip/ring  105  is more than 5 microns (pick to pick). Such minimum displacement of the cutting tip/ring  105  is needed to provide a minimum ablation efficacy required to further facilitate separation of lead encapsulating tissue. 
     The wire  107  is attached in an off-centered manner with respect to the cutting tip/ring  105 , thereby allowing the removed lead to be placed through the inner aperture  106 . The saline cooling irrigant  119  is delivered into the port  118  located at the proximal end  117  of the lumen  115  and serves for cooling the vibrational wire during delivery of vibrational energy from the vibrational energy source  110  to the cutting tip/ring  105 . The cooling irrigant exits at the distal end  116  of the lumen  115 . The saline cooling irrigant  119  also helps flush removed tissue and is aspirated via the aspiration port  114  outside the body. 
     The cutting tip/ring  105  can be configured with a smaller-diameter proximal region  122  that is stepped down from a distal region that includes the distal edge  121 . The cutting tip/ring  105  may be affixed to the distal end  103  of the shaft  101  at the proximal region  122  by any suitable methods including but not limited to glue bonding, fusing and other similar techniques. Also, the cutting tip/ring  105  may be at least partially located within the distal end  103  of the shaft  101 , and allowed to be free floating or vibrating, during the delivery of vibrational energy. 
     The secondary lumen  115  is extended longitudinally within the shaft  101 . The vibrational wire  107  is extended inside the lumen  115 . The lumen  115  is at least partially positioned at an off-centered location within the shaft  101 . The lumen  115  may be attached internally at one or more locations  123  to the shaft  101  to avoid any blocking of inner lumen  102  of the shaft  101 , and to minimize potential interference while introducing leads inside the inner lumen  102  during lead removal as described in  FIG. 3 . 
     The secondary lumen  115  may in one embodiment comprise a tubing inside the shaft  101 . In another embodiment, a multi-lumen shaft can be provided where a first lumen serves as functions of the inner lumen  102 , and a second lumen serves the function of the secondary lumen  115  function. 
     The off-centered positioning of the vibrational wire  107  within the shaft  101  allows for the provision of a larger or more spacious inner lumen  102 , so that the inner lumen  102  can more effectively receive leads while maintaining the smallest overall outer diameter OD possible. Off-centered attachment of the vibrational wire  107  to the tip  105  also preserves the largest possible opening  106  within the tip  105 . Also, placement of the secondary lumen  115  over the vibrational wire  107  in an off-centered arrangement allows cooling irrigant  119  to exclusively surround the vibrational wire instead of filling the entire inner lumen  102  of the shaft  101 . 
       FIG. 2  shows an alternative version of a lead extraction device  200  comprising an outer shaft  201  having a distal end  202 , a proximal end  203 , and a longitudinally extending lumen  204 . An inner shaft  205  has a distal end  206 , a proximal end  207  and a lumen  208  extending longitudinally therethrough. The inner shaft  205  is positioned inside the lumen  204  of the outer shaft  201 . A tubular metal tip/ring  209  having a circumferential aperture  210  is disposed at the distal end  202  of the outer shaft  201  and at the distal end  206  of the inner shaft  205 . The tip/ring  209  is aligned coaxially with the inner lumen  208  of the inner shaft  205  such that it is suitable to receive lead to be extracted into the aperture  210  and along the lumen  208  of the inner shaft  205 . 
     Two vibrational wires  211  and  212  are extended between the inner shaft  205  and the outer shaft  201 . The wires  211  and  212  are attached to the tip/ring  209  on one end and to a vibrational energy source  213  on the other end (not shown). Multiple numbers of vibrational wires may be disposed between the inner shaft  205  and the outer shaft  201  and attached in a similar fashion if needed. If multiple wires are used, it is preferable that these wires are spaced in a symmetrical fashion: for example, if two wires are used, these wires should be at the opposite sides, approximately 180 degrees apart. If three wires are used, it is preferable to space them apart by 120 degrees, and so on. 
     The tip/ring  209  can be configured with a smaller-diameter proximal region that is stepped down from a distal region. The tip/ring  209  may be free floating while positioned within the distal end  202  of the shaft  201  and on the distal end  206  of the inner shaft  205 . Alternatively, the tip/ring  209  may be affixed to the distal end  202  of the outer shaft  201  while free floating on the distal end  206  of the inner shaft  205  (not shown). Furthermore, the tip/ring  209  may be affixed to the distal end  206  of the inner shaft  205  while free floating on the distal end  202  of the outer shaft  201  (not shown). Also, the tip/ring  209  may be affixed to both distal ends  206  and  202  of the inner shaft  205  and outer shaft  201 , respectively (not shown). 
     The proximal end  203  of the outer shaft  201  is attached to a dual Y-connector  214  having a lead exit port  215 , an aspiration port  216  and a vibrational wire exit port  217 . In addition, a Touhy-Borst adapter  218  is attached to the lead exit port  215  to provide an internal seal to aspirate debris and tissue cut while proceeding with lead removal. 
     A tubing  219  is positioned within the dual Y-connector  214  and extends outside the dual Y-connector  214  to house the wires  211  and  212 , and is attached to the sonic connector  220 . The sonic connector  220  attaches both wires  211  and  212  to the vibrational energy source  213 . The additional side connector  221  is placed distally on the tubing  219  to provide an irrigation entry  222 . The cooling irrigant introduced through the entry  222  is infused into the port  221  and is delivered between the inner shaft  205  and the outer shaft  201  towards the tip/ring  209 . The irrigation exits near the tip/ring  209  and may be aspirated into the inner lumen  205  towards the aspiration port  216  and outside the body. Alternatively, the tip/ring  209  may include radial holes (not shown) to allow the irrigant to exit the tip/ring  209  into the aperture  210  and be further aspirated into the inner lumen  205 . 
     The shape and size of the lead removal devices  100  and  200 , as well as the tips/rings  105  and  209  shown in  FIGS. 1 and 2  are merely exemplary, and are not limited to any particular sizes, dimensions, configurations or shapes shown. 
       FIG. 3  is a schematic view of a pacemaker lead  300  having a distal end  301  and a proximal end  302 , and located in the vein  303  of a human being. The very distal and terminating electrode of the lead  300  is anchored distally to the ventricular heart chamber (not shown). The lead  300  is enclosed within the encapsulated tissue  304  to the wall of the vein  301 . Such encapsulating tissue  304  often makes it difficult to apply conventional techniques for removing the lead  300 . 
     At the beginning of the lead removal procedure, the lead  300  is detached, cut from the pacemaker or defibrillator device (not shown). An initial extraction of the lead  300  can be performed by simply pulling the proximal end  302  of the lead  300 . The entire body of the lead  300  can also be rotated to facilitate lead retraction. If the lead  300  does not move freely, a locking stylet  305  (e.g., Liberator Universal Locking Stylet, Cook Medical, Bloomington, Ind.) can be used to aid with traction. Manual pulling of the lead  300 , including use of the locking stylet, are well known in the art and will not be further described. 
     If such manual approaches in pulling the lead  300  and using the stylet  305  are not successful, the lead removal device  100  is inserted over the locking stylet  305  and the lead  300 , and positioned proximal to the encapsulating tissue  304 . Using the cutting ring  105  having aperture  106  and pushing the distal end  103  of the lead removal device  100  against the encapsulating tissue  304  may separate the lead  300  from the encapsulating tissue  304 . 
     Activation of vibrational energy from the energy source  110  will deliver vibrations via the proximal end  109  of the wire  107  (not shown) to the tip/ring  105  to further enhance separation and liberation of the lead  300  from the encapsulating tissue  304 . During the ablation of the encapsulating tissue  304  with the vibrating tip/ring  105 , additional approaches to separate the lead  300  from the encapsulating tissue  304  may be undertaken by further pulling the lead  300  proximally and outside the encapsulating tissue  304 . 
     Suction may be attached to the port  114  to aspirate the cut encapsulating tissue  304  and other created tissue residuals outside the body via the port  114 . 
       FIG. 4  illustrates the cutting tip/ring  105  and the distal end  103  of the lead extraction device  100  advanced distally through the encapsulating tissue  304 . The lead  300  is separated from the encapsulating tissue  304  and the distal end  301  of the lead  300  is separated from the ventricular heart chamber. 
       FIG. 5  illustrates an ultrasound energy source  110  as shown in  FIGS. 1 and 3 . The energy source  110  includes an ultrasound generator  500  and a piezoelectric transducer  501 , both located outside the human body. The ultrasonic generator  500  converts electrical power into high frequency current to drive the ultrasonic transducer  501 . The transducer  501  is made up of piezoelectric crystals and other active elements which expands and contracts when excited with a high frequency current, thus converting electrical energy to vibrations. 
     The proximal end  109  of the vibrational wire  107  is attached to the transducer  501  via a sonic connector  502 . The transducer  501  generates ultrasonic activity that produces vibrations and sound waves which are propagated from the transducer  501  via the sonic connector  502  into the proximal end  109  of the vibrational wire  107  to its distal end  108  that is attached to the tip  105  as shown in  FIG. 1 . 
       FIG. 6  illustrates an ultrasound energy source  213  as shown in  FIG. 2 . The energy source  213  is similar to the energy source  110  shown in  FIGS. 1 and 3  and includes an ultrasound generator  600  and a piezoelectric transducer  601 . The vibrational wires  211  and  212  are encapsulated together proximally within the sonic connector  220  which attaches both wires  211  and  212  to the piezoelectric transducer  601 . 
     The methods described herein employ a tissue cutting and ablation process that cuts a surrounding tissue during the delivery of vibrational energy to the tip/ring  105  and tip/ring  209 . When vibrational energy is delivered at a frequency range of 1 Hz to less than 1 MHz and at a power below 20 watts to tissue, plaque or calcifications, vibrational energy will transiently disrupt the integrity of the plaque and the cell membranes without creating permanent damage to the vessel wall, or to soft and healthy surrounding tissue. 
     In a typical embodiment of the invention, vibrating tip  105  or  209  is in contact with or in proximity to a treatment area within the vessel using a vibrational energy frequency of about 1 Hz to less than 1 MHz, preferably 1 kHz-100 kHz, and a power of less than about 20 watts is used to ablate scarred and calcific tissue. Power levels above 20 watts may cause permanent damage to the vessel wall such as thermal damage, necrosis and vessel rupture or perforations when vibrational energy is delivered by the lead removal device. 
     Vibrational energy is produced by the transducers  501  in  FIG. 5 and 601  in  FIG. 6  located outside the body and propagated via the vibrational wire  108  in  FIGS. 1 and 3 , and the wires  211  and  212  in  FIG. 2 , in form of longitudinal waves to the tip  105  in  FIG. 1  and the tip  209  in  FIG. 2 . Other ultrasound wave forms may be included such as surface waves and transverse waves but are less relevant in propagating ultrasound energy to generate needed displacement at the tip  105  in  FIG. 1  and the tip  209  in  FIG. 2 . 
     As used herein, “power” of the lead removal device delivering vibrational energy refers to watts of power delivered at the distal end of the tip/ring  105  and the tip/ring  209 . 
     Some theoretical considerations have been provided herein as to the mechanisms by which these therapeutic methods are effective; these considerations have been provided only for the purpose of conveying an understanding of the present invention, and do not limit the scope of the claims herein. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. It should be noted that the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims: