Cap for leaving lead of embedded type heart electric device in body
The cap for implantable cardiac electrical device leads addresses fluid ingress and clotting risks, and suppresses cardiac tissue heating by dispersing currents, ensuring safer lead retention in the body.
Patent Information
- Application Number
- JP2025077011
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-05-03
- Filing Date
- 2025-05-02
- Publication Date
- 2025-11-14
AI Technical Summary
Existing implantable cardiac electrical device leads left in the body are prone to bodily fluid ingress and blood clot formation, and expose cardiac tissue to heating risks during MRI due to induced currents.
A cap with a conductive outer surface portion connected to the metal connector and a flexible resin base to disperse induced currents, preventing fluid ingress and clotting while suppressing cardiac tissue heating.
Prevents bodily fluid ingress and blood clots, and significantly reduces cardiac tissue heating during MRI by dispersing currents, achieving safer lead retention.
Smart Images
Figure 2025169938000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a cap for retaining leads of an implantable cardiac electrical device within the body. [Background technology]
[0002] A typical implantable cardiac electrical device used for device treatment of arrhythmias caused by malfunction of the heart's electrical excitation consists of a main body (transmitter) with a built-in electric circuit and battery for generating electrical stimuli to be given to the heart, and a lead for transmitting the electrical stimuli generated in the main body to the heart. The lead of an implantable cardiac electrical device consisting of a main body and lead is made of an insulated electric wire (metal wire) with a metal electrode at one end that is attached to the heart to give electrical stimuli, and is connected to the main body by a connector at the other end.
[0003] When replacing the main body of an implantable cardiac electrical device, which consists of a main body and leads, for example, due to battery depletion, a new main body and new leads are used. The leads connected to the old main body have become adhered to the cardiac tissue, and forcibly removing them from the body could damage the heart, so they are often left in the body. In this case, if the leads are left in the body without any measures, there is a risk that body fluids will seep into the inside of the leads from the connector or that a blood clot will form around them. Therefore, the old leads to be left in the body are covered with a cap (insulating cap) made of flexible insulating resin, and the base is ligated to prevent body fluids from entering the inside of the cap.
[0004] For patients with residual leads (residual leads) undergoing MRI (Magnetic Resonance Imaging) examinations, the device's radio frequency (RF) magnetic field (ranging from tens to hundreds of megahertz) generates an induced electromotive force in the lead, which causes a current (induced current) to flow. Because the connector end is insulated, the induced current can be concentrated toward the electrode, potentially causing heating of the cardiac tissue to which the electrode is attached, resulting in cardiac damage. If the lead is left in the body without covering the connector with an insulating resin cap, leaving the metal parts, such as the connector pins, exposed, the induced current generated during the MRI examination and the current (conduction current) flowing in and out of the exposed metal parts of the connector and the electrodes at both ends of the lead can be dispersed to both ends of the lead, thereby suppressing heating of the cardiac tissue to which the electrodes are attached (see, for example, Non-Patent Document 1). However, leaving the lead inside the body with the metal part of the connector exposed is not clinically acceptable because, as mentioned above, there is a risk that body fluids may seep into the lead from the connector or that a blood clot may form around it. [Prior art documents] [Non-patent literature]
[0005] [Non-Patent Document 1] Mattei E, Gentili G, Censi F, Triventi M, Calcagnini G.2015.Impact of capped and uncapped leads abandoned on the heating of an MR-conditional pacemaker implant.Magn Reson Med 73:390-400. Summary of the Invention [Problem to be solved by the invention]
[0006] Therefore, the present invention aims to provide a cap that prevents bodily fluids from seeping into the lead from the connector or blood clots from forming around it, even when the lead of an implantable cardiac electrical device consisting of a main body and a lead is left inside the body, and that suppresses heating of the cardiac tissue to which the electrode is attached when a patient with a lead left inside the body undergoes an MRI examination. [Means for solving the problem]
[0007] The cap of the present invention, which was made in consideration of the above points and is intended to leave the lead of an implantable cardiac electrical device, which is composed of a main body and a lead, inside the body, is a cap for covering the connector for connecting the lead to the main body, as described in claim 1, and is configured so that at least a part of the outer surface is conductive with the metal part of the internal connector, and at least the base part is made of flexible resin. The cap according to claim 2 is the cap according to claim 1, wherein the ratio of the area of the portion that is electrically connected to the metal portion of the internal connector to the area of the entire outer surface is 5 to 75%. The cap according to claim 3 is the cap according to claim 1, wherein the outer surface is coated with a flexible resin. [Effects of the Invention]
[0008] According to the present invention, even if the leads of an implantable cardiac electrical device consisting of a main body and leads are left inside the body, it is possible to prevent bodily fluids from seeping into the inside of the leads from the connector and to prevent blood clots from forming around them, and it is possible to provide a cap that suppresses heating of the cardiac tissue to which the electrodes are attached when a patient with leads left inside the body undergoes an MRI examination. [Brief explanation of the drawings]
[0009] [Figure 1]This is a schematic diagram (with a see-through view of the inside) showing an example of the cap of the present invention in which a connector is inserted and the metal wire wound around the outer surface of the cap body made of flexible insulating resin is electrically connected to the metal part of the internal connector. [Figure 2] A schematic diagram of another example of the cap of the present invention (including a cross-sectional view of a key part showing the state in which a connector is inserted and the ring-shaped metal member that forms part of the main body of the cap is electrically connected to the metal part of the internal connector). DETAILED DESCRIPTION OF THE INVENTION
[0010] The cap for leaving the lead of an implantable cardiac electrical device consisting of a main body and a lead in the body of the present invention is a cap for covering the connector for connecting to the main body of the lead, and is configured so that at least a portion of the outer surface is conductive with the metal part of the internal connector, and at least the base portion is made of flexible resin.
[0011] The cap for retaining the lead of an implantable cardiac electrical device comprising a main body and a lead in the body of the present invention is a cap for covering the connector for connecting to the main body of the lead, and at least a portion of the outer surface is electrically conductive with the metal portion of the internal connector. Therefore, even though the connector is covered by the cap, at least a portion of the outer surface of the cap body is electrically conductive with the metal portion of the internal connector. In other words, a conductor is present not only at the electrode end of the lead but also at the connector end. Therefore, when a patient with a lead remaining in the body undergoes an MRI examination, induced currents and conducted currents can be dispersed to both ends of the lead, thereby suppressing heating of the cardiac tissue to which the electrode is attached. Furthermore, at least the base portion is made of flexible resin, so that it can be ligated to prevent bodily fluids from entering the cap.
[0012] In the present invention, the implantable cardiac electrical device, which is composed of a main body and leads, is composed of a main body (transmitter) with a built-in electric circuit and battery for generating electrical stimuli to be applied to the heart, and leads for transmitting the electrical stimuli generated in the main body to the heart. There are no particular limitations on the type of lead, as long as the lead is made of an insulated electric wire (metal wire) that has, at one end, an electrode made of metal for attaching to the heart to apply electrical stimuli, and at the other end, a connector for connecting to the main body. Specific examples of the type of lead include well-known devices such as pacemakers, implantable cardioverter defibrillators (ICDs), cardiac resynchronization therapy devices (CRTs), cardiac resynchronization therapy devices with pacing function (CRT-Ps), and cardiac resynchronization therapy devices with defibrillation function (CRT-Ds).
[0013] In the cap of the present invention, making at least a part of the outer surface electrically conductive with the metal part (such as a connector pin) of the internal connector can be easily achieved by various methods.
[0014] One example of such a method is to construct the cap body, including the base, from flexible insulating resin (which may be the same as existing insulating caps, with dimensions such as a length of 30 to 50 mm, an outer diameter of 3.5 to 6.5 mm, an inner diameter of 2.5 to 5.5 mm, and a resin thickness of 0.5 to 2.5 mm), wrap a metal wire around the outer surface of the body, and guide one end of the metal wire wound around the outer surface of the body through the body to the inside and make it contact with the metal part of the connector inserted into the cap. The metal wire is, for example, made of nickel, gold, titanium, copper, platinum, or an alloy containing these with a wire diameter of 1 to 100 μm (the metal constituting the core wire may be coated with another metal), and has a conductivity (10 6 The insulating resin having flexibility that forms the main body of the cap may be, for example, a silicone resin.
[0015] 1 is a schematic diagram (with the interior seen through) showing a specific example of a cap of the present invention, in which at least a portion of the outer surface is electrically connected to the metal portion of the internal connector, with the connector inserted and the metal wire wound around the outer surface of the cap body being electrically connected to the metal portion of the internal connector. The cap of the present invention has a body made of silicone resin, including the base, and metal wire (titanium, approximately 50 μm in diameter) wound in a coil shape around two locations on the outer surface of the body. One end of each of the two metal wires wound around the outer surface of the body penetrates the body and is guided inside, where it abuts against and contacts two metal portions of the connector inserted into the cap, such as a tip electrode (on the left side of the figure) that forms the tip of the lead and a ring electrode (on the right side of the figure) that forms a bipolar electrode on the connector pin, thereby establishing electrical continuity between the metal wire wound around the outer surface of the body and the metal portion of the connector. Therefore, the induced current and conduction current generated during an MRI examination are dispersed to both ends of the lead, thereby suppressing heating of the cardiac tissue to which the electrodes are attached. The metal wire wound around the outer surface of the cap body can be fixed to the outer surface of the body by the winding tension, but may be reinforced with a silicone resin adhesive or the like, if necessary. Furthermore, the penetration points of the metal wire in the cap body may be sealed with a silicone resin adhesive or the like to prevent bodily fluids from seeping into the inside of the cap through the penetration points of the metal wire.
[0016] The ends of the metal wires that penetrate the cap body and are guided inside may be connected to a metal housing (e.g., a housing whose inner diameter is the same as the outer diameter of the connector's metal portion, allowing the connector to be inserted and the metal portion of the connector to fit) located inside the body, and the connector may be inserted into the metal housing and the metal portion of the connector may be fitted, thereby establishing electrical continuity between the two metal wires wound around the outer surface of the body and the two metal portions of the connector via the metal housing. In this case, the metal wires may be connected to the metal housing by soldering the metal wires to the metal housing or by winding the metal wires around the metal housing. Instead of a metal housing, a tubular metal member may be used that has an inner shape and dimensions that allow the connector to be inserted and the metal portion of the connector to fit.
[0017] The ratio of the area of the outer surface of the cap body that is electrically connected to the metal part of the internal connector (the area where the metal wire is wound) to the entire area of the outer surface is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more (in the cap of the present invention shown in Figure 1, the area where the metal wire is wound in two places is approximately 10% each, for a total of approximately 20%). If the ratio of the area of the area where the metal part of the internal connector is electrically connected to the entire area of the outer surface is too small, the insulation of the connector end will be increased, making it difficult to distribute the induced current and conduction current generated during an MRI examination to both ends of the lead, which may make it difficult to suppress heating of the cardiac tissue to which the electrode is attached. The upper limit of the ratio of the area of the area where the metal part of the internal connector is electrically connected to the entire area of the outer surface is preferably 75%, more preferably 60%, and even more preferably 45%. If the ratio of the area of the portion that is electrically connected to the metal portion of the internal connector to the area of the entire outer surface is too large, the end portion on the connector side may have the properties of a heat source, which may cause heat generation in the surrounding tissue. Note that, in the case of a tip electrode and a ring electrode that constitute a bipolar electrode provided on a connector pin, the portion of the outer surface of the cap body that is electrically connected to the metal portion of the internal connector is electrically connected to at least the tip electrode, which makes it easier for induced currents and conduction currents generated during an MRI examination to be dispersed to both ends of the lead.
[0018] For example, when a human body phantom is used, in which the leads of a dual-chamber pacemaker are positioned based on X-ray CT images of the patient in whom the pacemaker is implanted, and RF irradiation is performed using a 1.5 Tesla MRI device, the temperature change due to heat generation at the end of the lead is measured using a method in accordance with the test standard ASTM F2182-19e2.When the connector is covered with an insulating cap made of existing silicone resin and the base is ligated with a non-absorbable ligature (or suture), the degree of temperature rise in the electrode positioned at the location of the right ventricle and the electrode positioned at the location of the right atrium is significantly higher than the degree of temperature rise when the connector is not covered with a cap and its metal part is left exposed (the electrode positioned at the location of the right ventricle in particular becomes hotter). However, when the connector is covered with the conductive cap of the present invention in this example and the base is ligated and measurements are taken, the temperature rise of each electrode is slight, as there is a metal wire on the outer surface of the cap body that is conductive to the metal part of the internal connector, and is the same as or lower than the temperature rise when measurements are taken without covering the connector with the metal part exposed.This is confirmed by experiments using leads that make up two pacemakers from two manufacturers, and the temperature rise is suppressed by 60 to 90% compared to when measurements are taken when the connector is covered with an insulating cap made of existing silicone resin and the base is ligated.
[0019] Another example is a method in which a portion of the cap body is made of a ring-shaped metal member that can come into contact with the metal portion of a connector inserted into the cap (the rest of the body, including the base, can be made of flexible insulating resin). In this case, contact between the ring-shaped metal member and the metal portion of the connector can be achieved by providing a metal member on the inner wall surface of the ring-shaped metal member that can come into contact with the metal portion of the connector when the connector is inserted into the cap, and inserting the connector into the cap to bring the metal member provided on the inner wall surface of the ring-shaped metal member into contact with the metal portion of the connector, or by designing the shape and dimensions of the inside of the ring-shaped metal member to be such that the metal portion of the connector can fit into it, and inserting the connector into the cap to fit the metal portion of the connector.
[0020] Figure 2 is a schematic diagram of a specific example of a cap of the present invention, in which at least a portion of the outer surface is electrically connected to the metal portion of the internal connector (including a cross-sectional view of a key portion showing the state in which the connector is inserted and the ring-shaped metal member constituting part of the cap body is electrically connected to the metal portion of the internal connector). The cap of the present invention has two portions of the cap body made of a ring-shaped metal member (made of titanium) with metal wings on the inner wall surface that can contact two metal portions of the connector (e.g., the tip electrode and ring electrode constituting the bipolar electrode of the connector pin) when the connector is inserted into the cap, and the remaining portions, including the base portion, are made of silicone resin. Therefore, when the connector is inserted into the cap, the metal wings on the inner wall surface of the ring-shaped metal member come into contact with the metal portion of the connector, establishing electrical conduction between the ring-shaped metal member and the metal portion of the connector. This allows induced and conducted currents generated during an MRI examination to be dispersed to both ends of the lead, thereby suppressing heating of cardiac tissue to which the electrodes are attached. The overall dimensions of the cap may be the same as those of existing insulating caps (for example, a length of 30 to 50 mm, an outer diameter of 3.5 to 6.5 mm, an inner diameter of 2.5 to 5.5 mm, and a resin thickness of 0.5 to 2.5 mm), and the ring-shaped metal member that constitutes the main body of the cap and the part made of silicone resin can be joined, for example, by inserting the end of the ring-shaped metal member inside the part made of silicone resin, or by bonding the two together using a silicone resin adhesive.
[0021] 1, instead of the metal wire wound around the outer surface of the cap body, a ring-shaped metal member is fitted to the cap body, and one end of the metal wire is joined to the ring-shaped metal member, and the other end of the metal wire is passed through the body to be introduced into the interior and contacted with the metal part of the connector inserted into the cap, or a method is used to vapor-deposit a metal thin film having a film thickness of, for example, 1 to 100 μm on the outer surface of the cap body, and the other end of the metal wire is joined to the metal thin film, and the other end of the metal wire is passed through the body to be introduced into the interior and contacted with the metal part of the connector inserted into the cap. There are no particular limitations on the formation mode or number of the portions on the outer surface of the cap body that are electrically connected to the metal part of the internal connector, but the desirable ratio of the area of the portions on the outer surface of the cap body that are electrically connected to the metal part of the internal connector to the area of the entire outer surface is as described above.
[0022] The outer surface of the cap of the present invention may be coated with a flexible resin. For example, if the metal wire wound around the outer surface of the main body of the cap of the present invention shown in FIG. 1 is coated with a flexible resin, the coated resin not only reinforces the fixation of the metal wire to the main body of the cap, but also prevents bodily fluids from seeping into the cap even if a gap through which bodily fluids can seep exists at the portion of the cap where the metal wire penetrates. However, if an insulating resin such as a silicone resin is used as the flexible resin for coating the outer surface of the cap of the present invention, if the resin thickness is too thick, the insulation of the connector end may increase, making it difficult to distribute induced and conducted currents generated during MRI examinations to both ends of the lead, which may make it difficult to suppress heating of cardiac tissue to which the electrodes are attached. Therefore, when coating the outer surface of the cap with an insulating resin, the resin thickness is preferably 500 μm or less, more preferably 350 μm or less, and even more preferably 200 μm or less (the lower limit may be, for example, 10 μm). The method for coating the outer surface of the cap with a flexible resin can be a method known per se, such as spray coating of the resin. When an insulating resin is used as the flexible resin for coating the outer surface of the cap of the present invention, the electrical conductivity of the cap (preferably 1 S / m or more) can be adjusted by adjusting the resin thickness, the coating area, or the coating shape (patterning). [Industrial Applicability]
[0023] The present invention has industrial applicability in that it can prevent bodily fluids from seeping into the lead from the connector or blood clots from forming around it, even when the lead of an implantable cardiac electrical device consisting of a main body and a lead is left inside the body, and it can provide a cap that suppresses heating of cardiac tissue to which electrodes are attached when a patient with a lead left inside the body undergoes an MRI examination.
Claims
1. A cap for leaving the lead of an implantable cardiac electrical device, which is composed of a main body and a lead, inside the body, and for covering the connector for connecting the lead to the main body, with at least a part of the outer surface being conductive to the metal part of the internal connector, and at least the base part being made of flexible resin.
2. 2. The cap according to claim 1, wherein the ratio of the area of the portion that is electrically connected to the metal portion of the internal connector to the area of the entire outer surface is 5 to 75%.
3. 2. The cap according to claim 1, wherein the outer surface is coated with a flexible resin.