Variable thickness electrosurgical snare

An electrosurgical snare may include a conductive distal loop that includes an uninsulated thinner portion and an uninsulated thicker portion. Respective current densities over the outer surfaces of the thinner and thicker portions may cause the uninsulated thinner portion to immediately begin cutting tissue, while the uninsulated thicker portion may initially begin coagulating the tissue.

TECHNICAL FIELD

The present invention relates generally to medical devices and more particularly to an electrosurgical snare having an uninsulated variable thickness distal loop.

BACKGROUND

Endoscopic snares may be used for tissue resection at a treatment site within a patient. For example, tissue resection may be performed in the gastrointestinal (GI) anatomy of a patient during various procedures, such as endoscopic submucosal dissection (ESD), endoscopic mucosal resection (EMR), and polpectomies. Tissue resection may be performed “hot” (i.e., with application of radio frequency (RF) current) or “cold” (i.e., without application of RF current, or manual resection). During tissue resection, either hot or cold, a distal loop of the snare is placed around a targeted tissue and is then retracted, which applies circumferential force around the tissue. For hot snares, RF current is also applied to the tissue, which cuts the tissue.

Some electrosurgical snares that apply RF current to the targeted tissue have a distal loop that is uninsulated. As such, RF current that is supplied to the distal loop is spread out along the entire length of the exposed wire that is in contact with the tissue. In addition, the wire making up the distal loop may have a constant diameter or thickness, and so the RF current may be distributed evenly (i.e., the current density may be the same) over the portions of the distal loop in contact with the tissue since the thickness and corresponding surface area are the same. If power settings of the power source generating the RF current are too low, the current density over the portions of the distal loop in contact with the tissue may be correspondingly too low, which makes it difficult and/or time consuming to initiate cutting the targeted tissue.

In addition, when the current density is too low, rather than cut the tissue, the RF current may coagulate the tissue, which may leave a ring of coagulation, even when the targeted tissue is finally cut. The ring of coagulation may make it difficult for a pathologist or a histologist to determine margins of the lesion. Also, a portion of the ring of coagulation that is left as part of the tissue in vivo may slow down tissue regeneration to cover the exposed muscle bed, which could result in delayed perforations.

While circumferentially coagulating the targeted tissue for a prolonged period of time prior to cutting may be undesirable, immediately circumferentially cutting the tissue once the RF current is applied may also be undesirable as doing so may lead to excessive bleeding. Hence, achieving a suitable balance of cutting and coagulation circumferentially around the targeted tissue during the resection process may be desirable in order to avoid both excessive coagulation and excessive bleeding.

BRIEF SUMMARY

In a first aspect, an electrosurgical snare may include an elongate conductive member longitudinally extending from a proximal end to a distal end; and a conductive distal loop connected to the distal end of the elongate member. The distal loop may include a first uninsulated portion having a first outer diameter, and a second uninsulated portion having a second outer diameter. The second outer diameter may be greater than the first outer diameter.

In a second aspect, a method of performing tissue resection may include: delivering a conductive distal loop of an electrosurgical snare to a treatment site within a patient, where the distal loop may include a thinner uninsulated portion having a first outer diameter and a thicker uninsulated portion having a second outer diameter. The second outer diameter may be greater than the first outer diameter. The method may also include: positioning the distal loop around a target tissue portion of underlying tissue to be resected, contacting a first portion of the target tissue portion with the thinner uninsulated portion and a second portion of the target tissue with the thicker uninsulated portion, applying electrical current to the target tissue portion with both the thinner uninsulated portion and the thicker uninsulated portion of the distal loop, and retracting the distal loop into a lumen of an elongate tubular member upon applying electrical current to the target tissue portion.

In a third aspect, an electrosurgical device may include: an elongate tubular member longitudinally extending from a proximal portion to a distal portion, where the elongate tubular member may include a body and a lumen longitudinally extending in the body. The electrosurgical device may further include an electrosurgical snare longitudinally and movably disposed in the lumen. A distal conductive loop of the electrosurgical snare may include a thinner uninsulated portion and a thicker uninsulated portion.

DETAILED DESCRIPTION

The present description describes medical devices and related systems and methods that include an electrosurgical snare that has a distal loop having multiple uninsulated portions, where at least one of the uninsulated portions has an outer diameter or thickness that is greater than an outer diameter or thickness of another of the uninsulated portions. The thicker portion may have a correspondingly larger surface area than the thinner portion.

During a tissue resection procedure of a target tissue portion from underlying tissue, both the portion with the larger diameter and the tissue with the smaller diameter may initially contact the target tissue portion. When electrical current is delivered to the distal loop, the current density over the thicker portion may be smaller than the current density over the thinner portion. As a result, a part of the target tissue portion contacting the thicker portion of the distal loop may begin being coagulated while a part of the target tissue portion contacting the thinner portion of the distal loop may begin being cut. The distal loop may be retracted, causing the thinner portion to continue to cut more tissue while less and less of the thicker portion contacts the tissue. Parts of the target tissue portion that were initially coagulated may not bleed as much when they are subsequently cut, as opposed to if those parts were cut without ever being coagulated.

FIG. 1shows a top view of an electrosurgical snare100longitudinally extending from a proximal portion102to a distal portion104. The snare100may include an elongate conductive member106that longitudinally extends from a proximal end108to a distal end110. The snare100may also include a conductive distal loop112connected to the distal end110of the elongate member106. The distal loop112may include a plurality of portions, including a first portion114and a second portion116having different outer diameters or thicknesses from each other. In particular, the first portion114may have a smaller diameter and/or may be thinner than the second portion116. For clarity, the first portion114and the second portion116are hereafter referred to as the thinner portion114and the thicker portion116, respectively.

Both the thinner portion114and the thicker portion116may be uninsulated. That is, both the thinner portion114and the thicker portion116may not be covered by an insulating material. Instead, the conductive outer surfaces of the thinner and thicker portions114,116may be exposed to and capable of contacting their outer surroundings.

For the example configuration of the distal loop112shown inFIG. 1, the thinner portion114may be a single segment that extends from a first end118to a second end120. The thinner portion114may be completely uninsulated and have the same or substantially the same diameter or thickness from the first end118to the second end120. In addition, the thicker portion116may include two segments, including a first segment122that extends from a first end124to a second end126, and a second segment128that extends from a first end130to a second end132. The first ends124,130of the first and second segments122,128may connected to each other and/or each be connected to the distal end110of the elongate member106or otherwise extend from the distal end110. From the distal end110, each of the first and second segments122,128may branch away from each other and extend separately to different ends118,120of the thinner portion114. As shown inFIG. 1, the second end126of the first segment122may be connected to the first end118of the thinner portion114, and the second end132of the second segment may be connected to the second end120of the thinner portion114. Additionally, like the single-segmented thinner portion114, the first and second segments122,128may be completely uninsulated and have the same or substantially the same diameter or thickness as they extend from their respective first ends124,130to respective second ends126,132.

In addition, for the example configuration of the distal loop112, the thinner portion114may include an apex or cutting tip134of the distal loop112. The apex134may be the portion of the distal loop112that biases a target tissue portion in the direction in which the snare100is being withdrawn to resect the tissue. For the example configuration shown inFIG. 1, during a resection procedure, the distal loop112may be proximally withdrawn to resect a target tissue portion, and the apex134may include a distal-most tip that proximally biases the target tissue portion as the distal loop112is proximally withdrawn. Additionally, the inner-part or surface of the apex may be the last part of the distal loop112to contact and cut target tissue during a resection operation. For the configuration shown inFIG. 1, the inner-part or surface of the apex134may include a V-shaped or other-similar shaped surface to grasp or secure the target tissue in contact with the thinner portion114as the distal loop112is proximally retracted during the resection operation. Additionally,FIG. 1shows the apex134being centrally located along the thinner portion114—i.e., the length from the apex134to the first end118is about the same as the length from the apex134to the second end120. For alternative configurations, the apex134may be an off-centered part of the thinner portion134—i.e., the length from the apex134to the first end118may be different (longer or shorter) than the length from the apex134to the second end120.

FIGS. 2-9show other example configurations of distal loops having a thinner portion and a thicker portion, each of which may be connected to the distal end110of the elongate member106instead of the distal loop112. Referring toFIG. 2, a distal loop212may include first ends224,230of first and second segments222,228of an uninsulated thicker portion216that are not directly connected to the distal end110of the elongate member106. Instead, the distal loop212may include a third uninsulated segment236that connects the first end224of the first segment222to the distal end110, and an uninsulated fourth segment238that connects the first end230of the second segment228to the distal end110, where each of the third segment236and a fourth segment238has a diameter that is less than the diameter of the thicker portion216.

Referring toFIG. 3, for another example distal loop configuration, a distal loop312may include first ends324,330of first and second segments322,328of an uninsulated thicker portion316that are not directly connected to the distal end110of the elongate member106. Instead, the distal loop312may include a first insulated segment340that connects the first end324of the first segment322to the distal end110, and a second insulated segment342that connects the first end330of the second segment328to the distal end110. By being insulated, the first and second insulated segments340,342may have an outer surface that is not capable of delivering electrical current to tissue they are in contact with. However, the first and second insulated segments340,342may have conductive cores that communicate the electrical current from the elongate member106to the uninsulated thicker portion316of the distal loop312.

Referring toFIG. 4, for another example distal loop configuration, a distal loop412may include a thicker portion416having a variable diameter or thickness. For configurations where the diameter or thickness varies, the diameter or thickness may be the average diameter or thickness over its length. In addition or alternatively, a minimum diameter or thickness of the thicker portion416may be greater than a maximum diameter or thickness of the thinner portion414.

Referring toFIG. 5, for another example distal loop configuration, a thicker portion of a distal loop512may include a plurality of uninsulated segments544separated from each other by one or more insulated segments546.

Referring toFIG. 6, for another example distal loop configuration, a thinner portion of a distal loop612may include a plurality of segments, including a first segment614that includes an apex634of the distal loop612and at least one additional segment separate or discontinuous from the first segment614that separates and/or is disposed in between two segments of a thicker portion. For example, as shown inFIG. 6, a second thinner segment648discontinuous from the first thinner segment614may separate and/or be disposed in between a first thicker segment650and a second thicker segment652, and a third thinner segment654discontinuous from the first thinner segment614may separate and/or be disposed in between a third thicker segment656and a fourth thicker segment658.

The example distal loops112,212,312,412,512, and612shown inFIGS. 1-6have an oval-shaped loop. However, shapes for the distal loop other than oval-shaped may be possible. For example,FIG. 7shows an example distal loop712having a hexagonal shape. As another example,FIG. 8shows an example distal loop812having a duck-billed shape. Other shapes for the distal loop may be possible.

In addition, in each of the example distal loops112,212,312,412,512,612,712, and812shown inFIGS. 1-8, the apex is part of the thinner portion.FIGS. 9 and 10show other embodiments where the apex is part of the thicker portion. Referring toFIG. 9, a distal loop912is similar to the distal loop112ofFIG. 1, except that thinner and thicker portions914,916are reversed from the thinner and thicker portion114,116ofFIG. 1. The thicker portion916may be a single segment that includes an apex934, whereas the thinner portion914may include two segments, including a first segment922and a second segment928each connected to the distal end110of the elongate conductive member106, and branching away from each other as they distally extend separately to different ends918,920of the thicker portion916.

Referring toFIG. 10, for another example distal loop configuration, a thicker portion1016of a distal loop1012may include an apex1034as well as other portions of the distal loop1012, except for a thinner portion1014, which may include a single segment extending in between the distal portion110and the apex1034.

The example configurations for a distal loop of a snare shown and described with reference toFIGS. 1-10are non-limiting examples. Other distal loop configurations may be possible, including those that combine the different features of the different distal loop configurations shown and described with reference toFIGS. 1-10.

For any of the previously-described example distal loop configurations, the thinner uninsulated portion and the thicker uninsulated portion may each have an associated diameter or thickness. For each of the uninsulated portions, if the associated diameter or thickness varies over its length, then the associated diameter or thickness may be the average diameter or thickness over the length. At a minimum, a ratio of the diameter or thickness of the thicker uninsulated portion to the diameter or thickness of the thinner portion may be greater than one-to-one. For some example configurations, the diameter or thickness ratio may be in a range from about one and one-tenth to one (1.1:1) to ten-to-one (10:1). For a particular configuration, the diameter of the thinner portion may be about 0.005 inches (about 0.127 millimeters) and the diameter of the thicker portion may be about 0.025 inches (about 0.635 millimeters).

In addition or alternatively, for any of the previously-described example distal loop configurations, the thinner uninsulated portion and the thicker uninsulated portion may each have an associated surface area of its respective outer surface. Where an uninsulated portion includes multiple segments, the surface area for that uninsulated portion may be a total surface area, which may be the sum of the surface areas of the segments. At a minimum, a ratio of the surface area of the thicker uninsulated portion to the surface area of the thinner uninsulated portion may be greater than one-to-one. For some example configurations, the surface area ratio may be in a range from about one and one-tenth to one (1.1:1) to ten-to-one (10:1).

In addition or alternatively, for any of the previously-described example distal loop configurations, the thinner uninsulated portion and the thicker uninsulated portion may each have an associated length. Where an uninsulated portion includes multiple segments, the length for that uninsulated portion may be a total length, which may be the sum of the lengths of the segments. At a minimum, a ratio of the length of the thicker uninsulated portion to the length of the thinner uninsulated portion may be greater than or equal to one-to-one. For some example configuration, the length ratio may be in a range from about one-to-one (1:1) to four-to-one (4:1).

FIGS. 11 and 12show cross-sectional views of example cross-sections of thicker uninsulated portions1100,1200, respectively, each of which may be representative of a cross-section for any of the thicker portions shown and described with reference toFIGS. 1-10. Referring toFIG. 11, the thicker uninsulated portion1100may be made of a single conductive material, which may be the same as or different from the conductive material used for the thinner uninsulated portion. Referring toFIG. 12, the thicker uninsulated portion1200may be made of a plurality of different conductive materials. For example, the thicker uninsulated portion1200may include an inner conductive core1202made of a first conductive material, and a second outer conductive member1204made of a second conductive material. For some example configurations, the second conductive material for the outer member1204may have a higher resistivity than the first conductive material for the inner core1202. Additionally, the inner core1202may be made of the same conductive material as the thinner uninsulated portion. The higher resistivity of the second conductive material of the outer member compared to the first conductive material of the inner core and thinner uninsulated portion may provide an increased current density of current flowing along the outer surface of the thinner uninsulated portion relative to the current density of current flowing along the outer surface of the thicker uninsulated portion.

FIG. 13shows a partial cross-sectional side view of a medical system1300, such as an endoscopic medical system, with which the electrosurgical snare100may be implemented.FIG. 13shows the electrosurgical snare100as having the configuration of the distal loop112as shown and described with respect toFIG. 1, although a snare having any of the other distal loop configurations212-1012shown and described with respect toFIGS. 2-10may be similarly included as part of the medical system1300.

In addition to the medical snare100, the medical system1300may include an elongate tubular member1302, such as a catheter, endoscope, or other similar elongate tubular structure, that extends from a proximal portion1304to a distal portion1306. The tubular member102may include a body1308extending from the proximal portion1304to the distal portion1306, and a lumen1310longitudinally extending in the body1308(For purposes of clarity, the lumen1310is not shown extending in the proximal portion1304). For some example configurations, the lumen1310may be a single lumen of the tubular member1302. For other example configurations, the lumen1310may be one of a plurality of lumens of the tubular member1302.

The electrosurgical snare100may be longitudinally and movably disposed in the lumen1310. In particular, the snare100may be movable between an undeployed position and a deployed position. In the undeployed, the distal loop112may be disposed in the lumen1310at the distal portion1306. In the deployed position, the distal loop may be disposed outside of the lumen1310past a distal end1312of the tubular member1302.FIG. 12shows the electrosurgical snare100in the deployed position.

The medical system1300may further include a handle assembly1314coupled to a proximal end1316of the tubular member1302. The handle assembly1314may be operatively coupled to the proximal end108of the elongate member106, and configured to move the snare100between the deployed and undeployed positions.FIG. 13shows the handle assembly1314configured as a three-ringed structure for gripping by an operator of the medical system1300, although other configurations for the handle assembly1314may be possible.

In addition, the medical system1300may include a power source1318, such as a radio frequency (RF) generator or an electrosurgical unit (ESU), electrically coupled to the electrosurgical snare100. As shown inFIG. 13, the electrosurgical snare100may be electrically coupled to the power source1318via the handle assembly1314, which may include a conductive member1320integrated with the three-ring assembly an electrical cabling1322that electrically couples the handle assembly1314with an active port1324of the power source1318.

The electrosurgical snare100may be part of an active path that supplies electrical current to a target tissue portion of underlying tissue at a treatment site within a patient to perform an electrosurgical procedure on the target tissue portion. The power source1318, when activated, may deliver the electrical current to the electrosurgical snare100. For the configuration shown inFIG. 13, the electrosurgical snare100may be electrically coupled to the power source1318in a monopolar configuration, in which a return path for the medical system1300may include a neutral electrode (not shown) positioned on the patient and electrically coupled to a return port1326of the power source1318. For other example configurations, the electrosurgical snare100may have a bipolar configuration with the power source1318, in which the return path may extend within and/or alongside the elongate tubular member1302back to the return port1326.

Additionally, other example medical systems may include more or fewer than the components shown inFIG. 13. For example, an electrosurgical medical device may include the electrosurgical snare100and the elongate tubular member1302, and may or may not include the handle assembly1314. The electrosurgical medical device may be removably connected with the power source1318and/or may perform several electrosurgical procedures with different power sources. Various configurations or combinations of the example medical system1300and/or various systems in which the electrosurgical snare100may be implemented may be possible.

The following describes an example method of performing a tissue resection operation using the medical system1300. Description of the method is made with reference toFIGS. 13, 14A-E, and15A-E. Referring toFIG. 13, the tissue resection operation may be performed to remove a target tissue portion1330of underlying tissue1332at a treatment site1328within a patient. The target tissue portion1230may be a polyp, pseudopolyp, or other raised portion of tissue for which a snare may be suitable for its removal and/or resection.

FIG. 13shows the distal portion1306of the tubular member1302along with the distal loop112delivered to the treatment site1328.FIGS. 14A-14Eshow a top view of the distal loop112, the distal portion1306of the tubular member1302, and a cross-section of a base portion1334of the target tissue portion1330taken along line14-14during the resection operation.FIGS. 15A-15Ecorrespond toFIGS. 14A-14E, and show a side view of the distal loop112during the resection operation of the target tissue portion1330.

As shown inFIGS. 14A and 14A, the distal loop112may be positioned around the base portion1334of the target tissue portion1330. As shown inFIGS. 14B and 15B, the distal loop112and distal portion1306may be moved to secure the distal loop112around the base portion1334and/or to optimize the amount of contact each of the thinner portion114and the thicker portion116of the distal loop112makes with the target tissue portion1330.

After positioning the distal loop112in a desired position around the base portion1334, the power source1318may be activated, and electrical current may be delivered from the power source1318, through the elongate conductive member106of the snare100, to the distal loop112, which may apply the electrical current to the base portion1334. Additionally, the surface area of the thinner portion114may be in a range such that application of the electrical current to the base portion1334by the thinner portion114has the effect of cutting the part of the base portion1334in contact with the thinner portion114. Further, the surface area of the thicker portion116may be in a range such that application of the electrical current to the base portion1334by the thicker portion116has the effect of coagulating the part of the base portion1334in contact with the thicker portion116.

Referring toFIGS. 14C and 15C, upon activation of the power source1318and application of the electrical current to the base portion1334of the target tissue1330, the handle assembly1314may be operated to retract the distal loop112to within the lumen1310. As shown inFIG. 13C, as the distal loop112is retracted to within the lumen1310, the diameter of the distal loop112may decrease, collapsing the distal loop112inward. For some example methods, the thicker portion116may begin cutting the base portion1334it comes into contact with after the initial application of the electrical current. For other example methods, the thicker portion116may continue to coagulate the tissue it contacts. However, the base portion1334may be squeezed inwardly or compressed due to the shrinking size of the distal loop112, decreasing the circumference and/or cross-section of the base portion1334and allowing the thinner portion114to cut more and more of the base portion1334as the distal loop112is retracted. The darker shading with the dotted lines outside of the distal loop112shows an area1336of the base portion1334remaining with the underlying tissue1332after cutting, and the lighter shading inside the loop112shows an area1338of the base portion1334that has not yet been cut.

Additionally,FIGS. 14C and 14Cshow coagulated tissue1340along parts of the edges of both the target tissue portion1330and the base portion1334remaining with the underlying tissue1332after cutting that were initially in contact with the thicker portion116upon application of the electrical current. Coagulating some of the base portion1334first before cutting may reduce the amount of bleeding during the resection process, compared to if the distal loop112only cut the tissue. At the same time, by initially cutting at least some of the base portion1334using the thinner portion114without first coagulating may provide an overall better tissue sample for histopathological evaluation, than if an entire ring of coagulation formed around the target tissue portion1330.

Further, as shown inFIGS. 14C and 15C, a ratio of the surface area of the thicker portion116in contact with the target tissue1330to the surface area of the thinner portion114in contact with the target tissue (i.e., the contact surface area ratio) may decrease as the distal loop112is withdrawn into the lumen and the amount of surface area of the thicker portion116in contact with the target tissue1330continually decreases as more and more of the distal loop112is retracted to within the lumen1310.FIGS. 14D and 15Dshow the thicker portion116no longer in contact with the base portion1334and a small amount of an area1338remaining to be cut in contact solely with the thinner portion114. As the distal loop112is being retracted, the apex134may grasp or secure the remaining parts of the base portion1334in contact with the thinner portion114.FIGS. 14E and 15Eshow the distal loop112being completely moved to within the lumen1310and the target tissue portion1330being completely resected from the underlying tissue1332.

The example method described with reference toFIGS. 13, 14A-E, and15A-E are described as being performed with a distal loop having a configuration where the apex134is part of the thinner portion114. As mentioned, other variable thickness distal loop configurations, such as those shown inFIGS. 2-10, may be used to similarly perform the resection method. For distal loop configurations where the apex is part of the thicker portion, such as those shown inFIGS. 9 and 10, the apex may begin coagulating the part of the target tissue portion1330it is in contact with, while the thinner portion of the distal loop may begin cutting the part(s) of the target tissue portion1330it is in contact with. When the resection method is performed with these distal loop configurations, as the distal loop is withdrawn to within the lumen1310, the amount of surface area of the thinner portion in contact with the target tissue portion1330decreases, causing the contact surface area ratio to increase. Eventually, only the thicker portion is in contact with an uncut portion of the target tissue portion1330. At some point, the contact surface area ratio is high enough that the thicker portion is cutting, rather than coagulating, the target tissue portion1330.

For some example methods, using a distal loop configuration where the apex is part of the thicker portion instead of the thinner portion may be advantageous, at least for visualization purposes. As shown inFIGS. 13, 14A-E, and15A-E, the apex134may be the distal-most portion of the distal loop112and furthest away from the distal end1312of the elongate tubular member1302when the distal loop112is positioned around the target tissue portion1330. Although not show, an imaging sensor or camera may be positioned near the distal end1312, such as one mounted on a distal end of an endoscope, and be configured to provide visualization access to an operator or physician of the resection method being performed. When the distal loop112is positioned around the target tissue portion1330as shown inFIGS. 13, 14A, 15A, the target tissue portion1330may block the imaging sensor from being able to visualize the thinner portion114. As such, when the cutting is being performed, the imaging sensor may not be able to visualize the thinner portion114cutting the target tissue portion1330, but may be able to visualize the thicker portion116coagulating the target tissue portion1330. In contrast, if the thicker portion includes the apex and the thinner portion include the other portions of the distal loop, such as the distal loop configuration shown inFIG. 9, then the imaging sensor may be able to visualize the cutting. Visualizing the cutting rather than the coagulating of the target tissue portion may be desirable during performance of at least some resecting methods.