Patent Application
20120109148
The present invention relates generally to devices to remove implantable medical devices from a patient and, in particular, to such devices to remove implantable medical devices.
Electrically active implantable medical devices such as pacemakers and cardioverter/defibrillators are well known in the art. Such implantable medical devices commonly and historically have been configured to be implanted within the patient some distance away from the heart of the patient. Pacemakers have traditionally been positioned in the musculature or other tissue of the patient's shoulder below the collar bone. Cardioverter/defibrillators are typically implanted either in the patient's side or, with recent advances in miniaturization, in the patient's shoulder. By utilizing transvenous leads to position electrodes within and in proximity of the heart, such implantable medical devices may be so positioned away from the heart and still be configured to treat cardiac conditions.
Because such implantable medical devices are positioned in the patient's shoulder or other relatively accessible location in the patient's body, implantation and explantation of such implantable medical devices may be relatively straight forward. In particular, because such implantable medical devices are both implanted at a relatively shallow depth and are of a size which is relatively easily manipulable for a medical professional, such implantable medical devices have not commonly required specialized tools for removal from the patient. Such devices may be relatively straightforwardly removed from the patient by accessing the device surgically, securing the device in the hands, disconnecting the implantable medical device from the transvenous leads and removing the implantable medical device from the patient.
Recently, however, miniaturization of implantable cardiac devices, particularly pacemakers, has allowed devices to be manufactured of a size small enough to permit implantation of the device within the heart of the patient or within other organs or parts of the body with similar space constraints, such as the epicardium, the pericardium, the lungs and the peripheral vascular system. Such developments may reduce the discomfort a patient may experience having an implantable medical device implanted at a relatively shallow depth in their shoulder and obviate the need for invasive transvenous leads. Pacemakers with these qualities may be referred to as leadless pacemakers. However, while the musculature and tissue of the shoulder may provide relatively easy physical access to a leadless pacemaker or other leadless implantable medical device, locating the leadless pacemaker in the heart of the patient may make the leadless pacemaker considerably more challenging to physically access for implantation and removal from the patient relative to a device positioned in the patient's shoulder.
Removal of a leadless pacemaker from the patient's heart may be desirable when, for instance, the power source of the leadless pacemaker has been or is about to be exhausted or in the event of patient discomfort. The same principle applies to other implantable medical devices. In addition, beyond the challenges posed by being relatively more difficult to physically access, once access to the heart of the patient or other space-constricted organ or portion of the patient's body has been gained, the leadless pacemaker must be secured and extracted. Because implantable medical devices implanted in the heart are fixed to some extent within the heart, the implantable medical device will tend to move within the patient with the beating and other movement of the heart. Thus, physically securing the implantable medical device for removal may be challenging. In addition, because the implantable medical device is so fixed within the heart there may be a tendency to resist removal.
An implantable medical device implantation and extraction system has been developed to address these challenges. A catheter with a longitudinal lumen has been configured to be passed through the vasculature of the patient and placed in proximity of the implantable medical device within the heart of the patient. A magnetic element is configured to pass through the lumen of the catheter and in proximity of the implantable medical device. A magnet on the magnetic element is configured to magnetically attract and secure the implantable medical device. Because of the magnetic attraction, the implantable medical device may be secured in spite of the movement of the heart. After the implantable device is secured with the magnet, the implantable medical device may be extracted from the tissue of the heart and withdrawn into the lumen of the catheter. Additional instruments, such as a snare having a lasso or other mechanical grappling device and instruments to cut away encapsulation tissue, may be passed through the lumen of the catheter in order to aid extract the implantable medical device from the tissue of the patient.
In an embodiment, a medical device system has an implantable medical device, a catheter and a magnetic element. The implantable medical device has a fixation member operatively coupled to the housing having an engaged state configured to engage tissue of a patient, the medical device being magnetically attractable. The catheter has a lumen and a distal portion configured for insertion in proximity of the implantable medical device. The magnetic element is configured to pass through the lumen of the catheter and to magnetically engage the implantable medical device when inserted toward the distal portion of the catheter.
In an embodiment, the magnetic element is configured to disengage the fixation member of the implantable medical device from the tissue of the patient
In an embodiment, a magnetic attraction between the magnetic element and the implantable medical device is sufficient to extract the implantable medical device as the magnetic element is extracted.
In an embodiment, the magnetic attraction between the magnetic element and the implantable medical device is at least four Newtons.
In an embodiment, the fixation member is at least one tine having a fixation force securing the at least one tine to the tissue of the patient and wherein the magnetic attraction between the magnetic element and the implantable medical device is greater than the fixation force.
In an embodiment, the fixation member has an engaged state engaged with the tissue of the patient while implanted and an unengaged state unengaged with the tissue of the patient and wherein the fixation member changes from the engaged state to the unengaged state by operation of the magnetic element.
In an embodiment, the fixation member is located proximate a distal portion of the implantable medical device.
In an embodiment, a proximal portion of the implantable medical device is magnetically attractable to the magnetic element.
In an embodiment, the system additionally has a snare having a distal portion and configured for insertion, the snare having a mechanical engaging member proximate the distal portion of the snare, the snare being configured to pass through the catheter and mechanically engage the implantable medical device
In an embodiment, the snare is configured to pass through the catheter and mechanically engage the implantable medical device while the magnetic element has magnetically engaged the implantable medical device.
In an embodiment, when the magnetic element is magnetically engaged with the implantable medical device, the magnetic element provides, at least in part, a physical guide for the snare to mechanically engage the implantable medical device.
In an embodiment, the fixation member has at least one tine having a fixation force securing the at least one tine to the tissue of the patient and wherein the mechanical engaging member mechanically engages the implantable medical device proximate the second portion of the implantable medical device with a connection force greater than the fixation force of the at least one tine.
In an embodiment, the mechanical engaging member comprises a lasso.
In an embodiment, the fixation member is located proximate a first end of the implantable medical device and wherein the implantable medical device further comprises a magnetic component positioned proximate a second end of the implantable medical device opposite the first end providing the magnetic attraction.
In an embodiment, the magnetic component of the implantable medical device comprises a magnet.
In an embodiment, the catheter and the magnetic element are configured to be inserted transvenously.
In an embodiment, a medical device extraction system for a implantable medical device having a fixation member operatively coupled to the housing having an engaged state configured to engage tissue of a patient, the medical device being magnetically attractable, has a catheter and a magnetic element. The catheter has a lumen and a distal portion configured for insertion in a proximity of the implantable medical device. The magnetic element is configured to pass through the lumen of the catheter and to magnetically engage the implantable medical device when inserted toward the distal portion of the catheter.
In an embodiment, a method extracts a magnetically attractable implantable medical device having a fixation member operatively coupled to the housing having an engaged state configured to engage tissue of a patient. A catheter having a lumen and a distal portion is inserted in proximity of the implantable medical device. A magnetic element is inserted through the lumen of the catheter. The implantable medical device is magnetically engaged when the magnetic element is inserted toward the distal portion of the catheter. The implantable medical device is removed by extracting the magnetic element.
In an embodiment, after the magnetically engaging step, the fixation member of the implantable medical device is disengaged from the tissue of the patient.
In an embodiment, the removing step is accomplished with the magnetic attraction between the magnetic element and the implantable medical device being sufficient to hold the implantable medical device as the magnetic element is extracted.
In an embodiment, after the magnetic element is magnetically engaged, the implantable medical device is mechanically engaged with a snare inserted through the lumen of the catheter.
In an embodiment, the inserting a catheter step, the inserting a magnetic element step and the removing step are performed transvenously.
As illustrated, housing 34 is generally cylindrical, though alternative configurations are also envisioned. In various embodiments, housing 34 is made of non-corrosive materials. In an embodiment, housing 34 is made of titanium. In alternative embodiments, housing 34 is made of ferrous or other magnetically attractive materials. In such embodiments, housing 34 may be covered in a non-bioreactive or non-corrosive material to make leadless pacemaker 32 safe for implantation in heart 10. Electrode 36 is configured to deliver pacing energy generated by the therapy circuitry and the internal power source to heart 10. Additional electrodes 36 may be positioned as needed on housing 34 to deliver a therapeutic output to heart 10.
One or more tines 38 create a fixation member and are configured to engage tissue in heart 10 to secure leadless pacemaker 32 within heart 10. In various embodiments, alternative fixation members may be applied as known in the art, including screws and helixes. In the illustrated embodiment, tines 38 are positioned proximate first end 39 of leadless pacemaker 32. In various embodiments, tines 38 are configured to ensnare chordae tendineae 24 within right ventricle 20, securing leadless pacemaker 32 within heart 10. Alternatively, tines 38 may engage cardiac tissue in or around tricuspid valve 22, left ventricle 28 or elsewhere in heart 10. In further alternative embodiments, tines 38 may engage tissue in the epicardial space, lung and vasculature. When engaged with chordae tendineae 24 or any patient tissue, tines 38 exert a fixation force which maintains leadless pacemaker 32 within heart 10. In various embodiments, tines 38 are made from material which is flexible to achieve multiple positions but resiliently biased in a configuration which allows tines 38 to be ensnared in chordae tendineae 24 or other tissue of heart 10. In various embodiments, tines 38 are formed from a shape memory alloy. In an embodiment, tines 38 are fanned from Nitinol.
Projection 40, e.g., a post, incorporates magnet 42 and indentation 44. As illustrated, projection 40 is generally cylindrical and positioned proximate second end 41 of leadless pacemaker 32. In alternative embodiments, projection 40, along with indentation 44, are alternatively shaped to facilitate a mechanical or connection force with an implantable medical device system discussed in detail below. In alternative embodiments, indentation 44 is not incorporated in projection 40. In alternative embodiments, projection 40 is not incorporated in leadless pacemaker 32. In such embodiments, magnet 42 is incorporated into housing 34. In further alternative embodiments where housing 34 is ferrous or which otherwise creates a magnetic attraction with a magnet, magnet 42 is not incorporated. Alternatively, magnet 42 is substituted with a magnetic component which is attracted to a magnet but which is not itself a magnet. In various such embodiments, projection 40 and indentation 44 are incorporated in leadless pacemaker 32. In alternative embodiments, projection 40 and/or indentation 44 are not incorporated in leadless pacemaker 32.
Catheter 48 is sized to pass through superior vena cava 16 or inferior vena cava 18 and right atrium 14 and into right ventricle 20. In an embodiment, catheter 48 is approximately one hundred twenty (120) centimeters long and a maximum external diameter at fairing 54 of 0.73 centimeters. In an embodiment, lumen 56 has a width of 0.20 centimeters along body catheter 52 and 0.68 centimeters within fairing 54. In various embodiments, catheter 48 is made from materials including, but not limited to, polytetrafluoroethylene, polyether block amide, stainless steel and tungsten.
Element 50 is configured to secure leadless pacemaker 32 using magnet 58 positioned on distal tip 60 of element 50. In various embodiments, magnet 58 is made from neodymium, iron and boron. Alternatively, magnet 58 is made from any material which may be developed to create a magnetic attraction with magnet 42 of leadless pacemaker 32 sufficient to secure leadless pacemaker 32 to element 50. In an embodiment, magnet 58 is an electromagnet. In embodiments where leadless pacemaker 32 does not incorporate magnet 42, magnet 58 of element 50 is strong enough to engage the magnetic material of leadless pacemaker 32 to element 50.
In various embodiments, magnet 58 is a bar magnet or elongate magnet with opposing poles. In various such embodiments, magnet 42 of leadless pacemaker 32 is also a bar magnet or elongate magnet with opposing poles. Where both magnet 42 and magnet 58 are bar or elongate magnets, magnets 42 and 58 may be rotationally fixed with respect to one another when magnetically engaged. In alternative embodiments, magnets 42 and 58 are not bar magnets but are sufficiently strong as to prevent rotation with respect to one another when magnetically engaged. In such embodiments, element 50 may be utilized to rotate leadless pacemaker 32, for instance, when tines 38 or an alternative fixation member such as a screw or helix, may be secured to, or disengaged from cardiac tissue through rotation.
As illustrated, for explantation, element 50 has magnet 58 strong enough to engage leadless pacemaker 32 with a magnetic force stronger than the fixation force between tines 38 and chordae tendineae 24. For implantation, element 50 has magnet 58 weak enough to disengage magnet 58 from leadless pacemaker 32 without disengaging leadless pacemaker 32 from cardiac tissue. In various embodiments, each tine 38 creates a fixation force of approximately one Newton. In embodiments with four tines 38, then, for implantation magnet 58 creates less magnetic attraction with leadless pacemaker 32 than one-quarter (ΒΌ) Newtons, while for explantation magnet 58 creates greater than four (4) Newtons of magnetic attraction with leadless pacemaker 32.
In the embodiment of system 146, lumen 56 of catheter 48 is sized to admit and allow to move longitudinally both element 50 and snare 162. In various embodiments, element 50 may provide a guide or rail for snare 162. In an embodiment, element 50 acts as a guide by circumscribing lasso 164 around element 50. As in system 46, element 50 is configured to magnetically engage leadless pacemaker 32 in order to fix leadless pacemaker 32 with respect to system 146. Then snare 162 may be extended through lumen 56 and around protrusion 40.
As illustrated in
In various embodiments of system 146, snare 162 is comprised of the same materials as element 50. In various embodiments, lasso 164 is made from nitinol, stainless steel and gold. Lasso 164 is contractable around projection 40 by manipulating a proximal end of lasso 164 (not pictured) which extends through snare 162 and which is manipulable by a user. By pulling on the proximal end of lasso 162, lasso 162 may be tightened about projection 40 so as to exert the mechanical or connection force on projection 40.
In alternative embodiments in which projection 40 is not incorporated into leadless pacemaker 32, lasso 164 may be tightened about any part of housing 34. In such embodiments, it may be relatively more difficult for lasso 164 to exert a mechanical or connection force than where projection 40 with indentation 44 is provided, though by applying relatively greater force to lasso 164 than may be applied to projection 40 with indentation 44, sufficient mechanical or connection force may be exerted on leadless pacemaker to disengage tines 38 from cardiac tissue.
Magnet 58 is then used to magnetically engage (804) magnet 42 of leadless pacemaker 32 when element 50 projects through or approaches opening 57 at distal end 59 of catheter. Optionally, and in embodiments incorporating system 146 with snare 162, lasso 164 is utilized to mechanically engage (806) leadless pacemaker 32, in various embodiments projection 40 at indentation 44. Tines 38 are disengaged (808) from cardiac tissue and leadless pacemaker 32 is removed (810) from heart 10 by extracting element 50 and, in embodiments with snare 162, snare 162 through catheter 48. In embodiments with fairing 54, leadless pacemaker 32 is withdrawn into fairing 54 and catheter 48 is removed. In embodiments without fairing 54, element 50 (and optionally snare 162) are removed the length of lumen 56 in order to extract leadless pacemaker 32, whereupon catheter 48 is extracted from the patient.
Magnetic element 50 is inserted (904) into lumen 56 of catheter 48. In various embodiments, the insertion (900, 904) of catheter 48 and element 50 occur simultaneously. In one such embodiment, simultaneous insertion occurs by inserting element 50 into lumen 56 prior to inserting either catheter 48 or element 50, and then inserting both catheter 48 and element 50 into the patient at the same time. Magnetic element 50 magnetically engages (906) leadless pacemaker 32. The insertion (900) of catheter 48, the insertion (902) of leadless pacemaker 32 into lumen 56, the insertion (904) of magnetic element 50 into lumen 56 and the magnetic engagement (906) of leadless pacemaker 32 with magnetic element 50 may occur in any sequence convenient for use.
Leadless pacemaker 32 is egested (908) from catheter 48, in an embodiment by causing magnetic element 50 to exert a pushing force on leadless pacemaker 32. As leadless pacemaker 32 emerges from catheter 48, tines 38 engage chordae tendineae 24. Magnetic element 50 is disengaged (910) from leadless pacemaker 32, and catheter 48 and magnetic element 50 are withdrawn (912) from the patient, leaving leadless pacemaker 32 engaged with cardiac tissue. Optionally, prior to disengaging (910) magnetic element 50 from leadless pacemaker 32, the engagement of tines 38 with chordae tendineae 24 may be tested (912) by exerting a pulling force on leadless pacemaker 32 less than the magnetic attraction between magnet 58 and leadless pacemaker 32. If tines 38 do not separate from chordae tendineae 24 then leadless pacemaker may be deemed successfully implanted.
Thus, embodiments of the medical device extraction system and method are disclosed. One skilled in the art will appreciate that the present invention can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the present invention is limited only by the claims that follow.
