Devices and methods for lead extraction

An improved lead extraction system using a rotatable hole saw electrode with a sharp cutting edge that is useful for the extraction and the removal of unwanted lead by a minimal invasive procedure. A lead extraction system suitable for radiofrequency ablation of scar tissues surrounding the implanted lead, is comprised of an outer catheter sheath and an inner delivery catheter having a distal end, a proximal end and at least one lumen extending therebetween, wherein a locking stylet is provided. In one embodiment, the lead extraction system has fluid infusion and irrigation means at its distal tip section and a rotatable hole saw electrode for loosening the target scar tissue by applying radiofrequency energy and cooled fluid to the said electrode and its contacted tissue.

FIELD OF THE INVENTION 
The present invention generally relates to the improved system for cardiac 
lead extraction. More particularly, this invention relates to a catheter 
system and to methods for removing an implanted endocardial pacemaker lead 
and/or an implanted transvenous defibrillation lead from the 
cardiovascular system of a patient using a rotatable hole saw electrode 
and RF energy. 
BACKGROUND OF THE INVENTION 
Symptoms of abnormal heart rhythms are generally referred to as cardiac 
arrhythmias. An abnormally rapid rhythm is referred to as tachycardia, 
while the arrhythmia rates below the normal rhythm are termed bradycardia. 
Various factors affect the human heart rate and contribute to the changes 
of rate from what is termed the normal sinus rate range. These rates 
generally range in adults from 60 to 100 beats per minute. The heart 
includes a number of normal pathways which are responsible for the 
propagation of electrical signals from the upper to lower chambers, which 
are necessary for performing normal systole and diastole function. 
Treatment of arrhythmias may be accomplished by a variety of approaches, 
including drugs, surgery, implantable pacemakers/defibriliators, and 
catheter ablation. While drugs may be the treatment of choice for many 
patients, they only mask the symptoms and do not cure the underlying 
causes. Surgical and catheter-based treatments can only cure some simple 
cases. Implantable devices correct the arrhythmia and prevent it from 
occurring unexpectedly. 
Cardiac pacemakers, chronically implanted within a patient's body, and 
connected to the heart by at least one lead, are frequently used to 
control bradycardiac conditions. Recently, implantable 
cardioverter-defibrillators, also implanted chronically in a patient's 
body and connected to the heart by at least one lead, can be used to 
control tachyarrhythmias and life-threatening fibrillations. There are 
generally two different types of body implantable leads used with cardiac 
pacemakers: one type, which requires surgery to expose the myocardial 
tissue, whereby an electrode is affixed to the epicardial tissue; the 
second type, which can be inserted through a body vessel, such as a vein, 
into the heart where an electrode contacts the endocardiac tissue. In the 
second type, the endocardial lead is often secured to the heart through 
the endocardial lining by a helix, hook, or tines affixed to the distal 
end of the lead. When the end of the lead contacts the lining of the heart 
at a desired location, the lead may be secured in place by utilizing lead 
securing means, such as screwing the helix into the heart tissue, 
anchoring the hook or engaging the tines. 
Similarly, cardioverter defibrillators have used both epicardial leads, 
that is, leads with electrodes attached to the outside of the heart, and 
endocardial leads, that is, leads inserted into the heart through a body 
vessel. 
With either pacing or defibrillation endocardial leads, fibrotic tissue may 
eventually encapsulate the leads, especially in areas where there is low 
velocity blood flow. When small diameter veins, through which the lead 
passes, become occluded with fibrotic tissue, the separation of the lead 
from the vein is difficult and can cause severe damage or destruction to 
the vein. Furthermore, separation may not be possible without constricting 
the movement of the lead. 
In most cases, an endocardial lead will outlast its associated implanted 
device. However, the lead may become inoperative, or another type of lead 
may be required. Frequently, the existing lead is left in place, and an 
additional lead is implanted, rather than risking the removal of the old 
lead, which was now bonded to the surrounding tissue. Leaving the 
implanted lead in place, however, particularly in the heart, may further 
restrict the operation of various heart valves through which the lead 
passes. If several leads are left in place, operative procedures of the 
heart and its efficiency may be impaired. 
In addition, infection may occasionally develop in or around a lead, 
requiring surgical removal In some cases, surgical removal may involve 
open heart surgery with its accompanying complications, risks, and costs. 
These risks are significant for the endocardial pacemaker lead. Because 
the endocardial defibrillation lead is larger and more complex, the 
complications associated with the removal of a defibrillation lead can be 
even greater. 
Extraction of chronically implanted leads has been difficult in the past. 
The problems may include lead fragility and scar tissue encountered along 
the vein, as well as within the heart. Intravascular countertraction 
techniques using locking stylets and sheaths via the implant vein, or 
sheaths, snares, and retrieval baskets via the femoral vein have been 
described in the literature. Among them, scar tissue was the primary 
reason for partial or failed removal of a lead. Scar tissue was usually 
present in multiple locations; the venous entry/subclavian area and the 
ventricle were the most frequent sites. 
Several methods for the removal of pacemaker leads have heretofore been 
proposed. One method involves a lead removal tool that utilizes a hollow, 
rigid tube and beveled rod tip for engaging and deforming the coil 
structure of the heart lead. However, if such a lead can not be removed 
because of some complication, the tip of the tool is nevertheless locked 
in place and could not be removed from the lead. Consequently, both the 
tool and the lead would have to be surgically removed. Moreover, the rigid 
tube of the tool could easily puncture a blood vessel or a heart cavity 
wall. 
Another method for transvenously extracting a lead involves manual 
manipulation without the use of an external tool. However, such a method 
is not possible if the lead has become encapsulated in a blood vessel. 
Moreover, this method puts excessive strain and tension on the 
polyurethane or silicone insulation surrounding most pacemaker leads. 
Should the lead break, the broken inner coil and insulation could damage 
the heart or surrounding blood vessels. Surgical removal of the broken 
lead would be imperative. Moreover, if the pacemaker lead included tines, 
a cork screw, or another fixation device at the tip, pulling on the lead 
could seriously damage the wall of the heart. 
Another technique has been proposed in U.S. Pat. No. 4,943,289. This method 
generally includes the use of a stiffening stylet, which can be inserted 
into the lead, and then engages the inner coil of the lead near the tip, 
allowing tension to be applied through the stiffening stylet close to the 
tip of the lead. This technique also uses a pair telescopic flexible tubes 
that are positioned over the lead to free fibrotic connections until the 
tubes are close to the distal tip of the lead. In a related U.S. Pat No. 
5,632,749, Goode et al. teaches the use of an anchoring project or 
expandable means associated with the apparatus for lead extraction. 
Another method has been proposed in U.S. Pat. No. 5,620,451. In this 
patent, Rosborough teaches the use of a flexible coil of flattened ribbon, 
whereby a cutting surface is provided at the distal end of the coil. It is 
also disclosed that the coil is radiopaque so that its use may be observed 
in the body by fluoroscopy or other suitable means. 
What is particular interest to the present invention are radiofrequency 
(RF) ablation protocols, which have been proven to be highly effective in 
tissue ablation, while exposing a patient to minimal side effects and 
risks. Radiofrequency energy is also used in cutting the tissue, or 
separating implant parts and other substrates. Through a combination of 
the mechanical rotating force and the radiofrequency energy on a 
catheter-based device, extraction and removal of an implanted lead becomes 
feasible and less difficult. 
There is therefore a need for a device which comprises a rotatable catheter 
shaft having a sharp cutting edge with RF energy delivery capability, that 
is useful for extraction and removal of undesired lead by minimally 
invasive procedures. It would be desirable for such a system to cut 
through the scars along an implanted lead by utilizing sharp edges of the 
electrode above-mentioned with assistance of RF energy for improved lead 
removal. 
SUMMARY OF THE INVENTION 
In general, it is an objective of the present invention to provide an 
improved system for lead removal of both heart pacemaker leads and 
cardioverter-defibrillator endocardial leads. It is another objective of 
the present invention to provide an improved lead extraction system with 
the means of a hole saw electrode, which can be used in ablating an 
undesired tissue mass, such as scar tissue or a fibrotic attachment at the 
venous entry/subclavian area and the ventricle surrounding an implanted 
lead in a minimally invasive manner. Also, another objective of the 
present invention is to provide a lead extraction system to irrigate the 
scar tissue site during the lead extraction. 
In one embodiment, a lead extraction system is comprised of an outer 
catheter sheath and an inner delivery catheter. The catheter sheath is 
semi-flexible, strong and non-conductive, so that the lead extraction 
system can follow the implanted lead to its distal end where scar tissue 
is attached, and extract that lead out of a patient. The catheter sheath 
comprises a distal end, a proximal end, and at least one lumen extended 
therebetween. The delivery catheter has a distal tip section, distal end, 
proximal end, and at least one lumen extended therebetween. A handle is 
secured to the proximal end of the delivery catheter and the catheter 
sheath. The delivery catheter contains a rotatable hole saw electrode at 
its distal end. The rotating action of the delivery catheter is controlled 
at the proximal end of the handle by a rotating mechanism. The delivery 
catheter can be advanced along the lead to the scar tissue site to 
dislodge the lead from the said scar tissue by an advancing mechanism at 
the handle. 
The electrode deployment means of the delivery catheter includes a 
retractable tip section that comprises a hole saw electrode, having a 
sharp end. In one embodiment, the sharp end has a relatively straight 
edge. In an alternate embodiment, the sharp end comprises a plurality of 
sharp points at its edge. In general, the hole saw electrode has a 
conductive surface for RF energy delivery while the remaining portion of 
the delivery catheter is not conductive. The tip section has a 
non-deployed state, when the delivery catheter is positioned inside the 
catheter sheath. This non-deployed state is maintained during the 
insertion operation of the lead extraction system into the patient, and 
during withdrawal of the system from the patient. 
The tip section of the delivery catheter has a deployed state when it is 
advanced out of the distal end of the said catheter sheath. Deployment of 
the tip section is accomplished by a pushing action on a push-pull 
mechanism on the handle. Under the deployed state, the delivery catheter 
has excellent torqueability and also has rotation capability. The degree 
of deployment is controlled by the pushing action at the push-pull 
mechanism on the handle and is proportional to the pushing distance on the 
push-pull plunger which is quantifiable. The rotation of the delivery 
catheter can be accomplished either manually, mechanically or 
electromechanically from a rotating means located at the proximal end of 
the handle. 
The deployed hole saw electrode defines an ablation target of the scar 
tissue covering the implanted lead. The sharp end of the electrode is 
positioned to directly face the target scar tissue. The said electrode is 
rotatable and is capable of heating the tissue via RF energy. The 
advancing operation of the tip section of the delivery catheter is 
accomplished by pulling back the outer catheter sheath relative to the tip 
section of the said delivery catheter, so that the tip of the said hole 
saw electrode firmly contacts and grasps the target scar tissue during an 
ablation procedure. The degree of advancement is mainly controlled by the 
pulling action at the push-pull mechanism on the handle. 
A conducting wire which is secured to the base of the hole saw electrode 
means, passes through the lumen of the delivery catheter and through the 
interior void of the handle, and is thereafter secured to a contact pin of 
the connector at the proximal end of the handle. Therefrom, the conducting 
wire is connected to an external RF generator for RF energy delivery. 
During lead extraction operations, the lead extraction system, comprised of 
an outer catheter sheath and an inner delivery catheter, is inserted into 
the body through a natural body opening by sliding over an existing lead. 
After the system approaches the target scar tissue mass to be treated, the 
tip section of the delivery catheter is deployed by being pushed out of 
the catheter sheath from a push-pull mechanism at the handle. Once 
positioned, the sharp ends of the hole saw electrode encircles the tissue 
mass. By a simultaneous or alternate mode, gradually pushing forward the 
delivery catheter against the tissue mass, rotating the hole saw 
electrode, and applying RF energy, the target tissue mass is loosened as a 
result of a combination of the RF energy, mechanical cutting, and the 
rotating forces of the sharp ends of the hole saw electrode. 
A fluid source is positioned at the proximal end of the handle for 
supplying a fluid flow through the lumen of the said delivery catheter to 
the tip section, which contains a fluid vent opening. Therefore, at 
ablation time, the tip section with the hole saw electrode is positioned 
against the tissues to be ablated. The fluid is continuously or 
intermittently supplied through the opening to cover and rinse the tissue 
contact site of the electrodes so that the impedance rise at the contact 
site is substantially reduced. The appropriate fluid flow rate for fluid 
irrigation is preferably in the range of 5 cc/min to 20 cc/min. By cooling 
off the electrode during RF energy delivery, results in optimal ablation 
efficiency results, and efficient cutting loosens the scar tissues 
surrounding the implanted lead. Therapeutic fluid can also be supplied 
through the existing fluid by conveying/irrigation means. 
A fluid conveying lumen is associated with the elongated delivery catheter, 
and is preferably disposed of within a separate lumen of the delivery 
catheter along the longitudinal axis thereof The lumen is adapted to 
communicate with the fluid supplying source, to convey fluid from the 
source and through the lumen to be discharged through the vent opening of 
the tip section and diffused out of the tip section containing the hole 
saw electrode. 
This invention also comprises a method and a system for controlling the 
flow rate of fluid through the lumen to optimize the cooling effect of the 
energy delivering electrode means of the lead extraction system The 
control system preferably regulates the flow rate based on signals 
representative of the temperature of the electrode tip and/or tissue 
impedance. 
In a further embodiment, the material of the electrode is selected from the 
group of platinum, iridim, gold, silver, stainless steel, and Nitinol. 
After the lead and its surrounding tissue is loosened, a locking stylet is 
used to engage the lead with the lead extraction system and the lead is 
removed by the said lead extraction system thereafter. 
The system and methods of the present invention have several significant 
advantages over the currently known lead extraction systems or methods. In 
particular, the rotatable hole saw electrode having RF ablation 
capabilities of this invention results in a more effective means for 
cutting loose the scar tissue and has a more effective means for removing 
the undesired lead from the implanted site.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
A lead extraction system constructed in accordance with the principles of 
the present invention is comprised of an outer catheter sheath and an 
inner delivery catheter wherein their proximal ends are secured to a 
handle. FIG. 1 shows an overall view of the lead extraction system having 
a catheter sheath 1, having a distal end 2, a proximal end 3, and at least 
one lumen extended therebetween. A handle 4 is attached to the proximal 
end 3 of the said catheter sheath 1. The delivery catheter, which is 
located within the lumen of said catheter sheath 1, has a distal tip 
section, distal end, proximal end, and at least a lumen extended 
therebetween. The proximal end of the delivery catheter is also secured to 
the handle 4, where there is a push-pull mechanism 5 on the handle 4. A 
pushing plunger 8 of the push-pull mechanism 5 is used to control the 
degree of the pushing action. A rotating means 6 is located at the 
proximal end of the handle 4. The connector means 7 for the conducting 
wire 13 to be used to transmit the RF energy is located at the very 
proximal end of the lead extraction system. A fluid irrigation means 9 
that contains an external fluid supply source is located close to the 
proximal end of the handle 4. 
FIG. 2 shows a cross-sectional view of the handle portion 4 of the lead 
extraction system, which is comprised of an outer catheter sheath I and an 
inner delivery catheter 10. The catheter sheath 1 can be pushed or pulled 
longitudinally, relative to the handle 4. However, it is maintained 
stationary circumferentially, relative to the handle. In other words, when 
the inner delivery catheter is rotated relative to the handle, the outer 
catheter sheath does not rotate at all. This is shown in FIG. 5 where the 
C--C section is illustrated. The delivery catheter 10 is secured to the 
rotating means 6 at the proximal end of the handle portion. The rotating 
means 6 has a plurality of fluid inlet ports 11. The fluid from an 
external fluid irrigation means 9 is introduced through an opening at the 
handle 4 and thereafter through the inlet ports 11 into the lumen of the 
rotating means 6. The fluid is confined by two O-rings 12 between the 
handle 4 and the rotating means 6. The fluid is further confined within 
the lumen of the delivery catheter 10 when the fluid flows down to the 
distal end of the said delivery catheter. 
FIG. 3 is a side view of the A--A section of FIG. 2, which shows the fluid 
conveying means of the delivery catheter 10. Two O-rings 12 are located 
between the handle 4 and the outer surface 15 of the rotating means 6. The 
rotating means 6 has a plurality of fluid inlet ports 11. A conducting 
wire 13 for RF energy transmission with its insulation 14 is located 
within the lumen of the rotating means 6. 
FIG. 4 is a side view of the B--B section of FIG. 2, which shows the O-ring 
portion between the outer catheter sheath 1 and the inner delivery 
catheter 10. An O-ring 16 is located between the outer surface 15 of the 
rotating means 6 and the proximal section of the catheter sheath 1. The 
rotating means 6 is firmly connected to the delivery catheter 10 so that a 
true 1:1 rotating ratio between the rotating means and the delivery 
catheter is maintained. 
FIG. 5 is a side view of the C--C section of FIG. 2, which shows the 
attachment of the outer catheter sheath 1 and the handle 4 at the 
contacting joint 17. A pushing plunger 8 of the push-pull means 5 on the 
outer catheter sheath I is located adjacent to the handle 4. The catheter 
sheath can be pushed or pulled relative to the handle. However, the 
pushing plunger 8 on the catheter sheath 1 is interconnected with the 
handle 4 at the contacting joint 17 so that the catheter sheath can not 
rotate relative to the handle. 
FIG. 6 is a cross-sectional view of the distal tip section of the lead 
extraction system of the present invention. The catheter sheath 1 has a 
distal end 2 while the delivery catheter 10 comprises a distal tip section 
18, a distal end 19 and a hole saw electrode 20. Under a non-deployed 
state, the delivery catheter 10 is located within the lumen of the 
catheter sheath 1. Upon electrode deployment, the distal tip section 18 of 
the delivery catheter 10 is pushed out of the tip 2 of the catheter sheath 
1. To improve its flexibility and torqueability, a portion of the delivery 
catheter 10 can contain a coil wire 21, which can also serve as the 
transmission means for RF energy delivery to the electrode 20. 
FIG. 7 is a perspective view of one type of a hole saw electrode 20. The 
electrode is located at the distal tip section 18 of the delivery catheter 
10. The electrode portion is conductive and can deliver RF energy when it 
contacts the tissue. The sharp edge 22 of the hole saw electrode 20 is 
used to cut through the scar tissue associated with the implanted lead. 
The cutting operation is achieved by a combination of rotating the hole 
saw electrode, advancing the hole saw electrode, and/or heating the hole 
saw electrode. 
In a further embodiment, the lead extraction system may further comprise a 
stylet locking mechanism at the handle 4 for controlling the advancement 
and locking activities of the locking stylet of the delivery catheter 10. 
A stylet locking plunger of the locking mechanism at the handle is used to 
control the degree of the advancement of the locking stylet of the 
delivery catheter. The stylet locking mechanism on the lead extraction 
system is well-known to those who are skilled in the art. 
In an additional embodiment, the lead extraction system further comprises a 
temperature sensing and close-loop temperature control mechanism for the 
hole saw electrode having a temperature sensor mounted on the electrode 
close to the tissue contact site. Temperature sensing wires (not shown) 
along with a thermocouple or thermistor means is provided to transmit the 
temperature data from the tissue contact site to an external temperature 
measuring and control apparatus. An algorithm is equipped for the ablation 
system so that a close-loop temperature control is effective and the 
temperature data is relayed to an external RF generator (not shown) for 
controlled energy delivery. 
FIG. 8 is a close-up view of the lead extraction operation of the lead 
extraction system. An implanted lead 23 with its surrounding scar tissue 
24 is to be removed from the body of a patient. The hole saw electrode 20 
is positioned to have its sharp edge 22 contacting the scar tissue. The 
delivery catheter 10 is located within the lumen of the catheter sheath 1. 
The delivery catheter is capable of rotation, while the catheter sheath is 
stationary. By way of illustration, a lead extraction system of this 
invention is inserted along or is slid over the existing lead wire through 
a vein. The system is positioned near the target tissue site where the 
delivery catheter contacts the tissue. The delivery catheter is deployed 
and the sharp edge of the electrode firmly contacts the tissue to be 
ablated. By a combination of the following actions: gradually pushing 
forward the delivery catheter against the tissue mass, rotating the hole 
saw electrode, and applying RF energy to the hole saw electrode, the 
target tissue mass is loosened. Thereafter, the lead can then be removed 
with ease. 
From the foregoing, it should now be apparent that an improved lead 
extraction system comprised of a rotatable hole saw electrode with RF 
energy delivery capability has been disclosed for removing the implanted 
lead from a patient. While this invention has been described with 
reference to a specific embodiment, the description is illustrative of the 
invention and is not to be construed as limiting the invention. Various 
modifications and applications may occur to those skilled in the art 
without departing from the true spirit and scope of the invention as 
described by the appended claims.