JP2001521774A - Ring-shaped electrode structure for diagnostic and ablation catheters - Google Patents

Abstract

(57) Abstract: A ring-shaped electrode structure with increased radial dimensions. The electrode projects from the outer diameter of the catheter when mounted on the catheter. The upright ring-shaped electrode is provided with a tissue contacting surface that generally contacts tissue within the patient's body before the catheter itself contacts tissue. The electrodes ensure good and uniform contact between the tissue and the respective electrodes attached to the distal end of the catheter. This electrode also allows greater pressure to be applied to the tissue with less power than conventional electrode catheter configurations because the contact area created by the upright ring-shaped electrode is reduced. In a preferred configuration, the upright electrodes have smooth, curved edges to prevent tissue damage as the catheter is advanced and retracted within the patient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a diagnostic and ablation catheter, and more particularly, to a ring-shaped electrode structure for a diagnostic and ablation catheter.

[0002]

[Prior art]

Arrhythmias are commonly known as irregular heart beats or arrhythmias. Two of these cardiac rhythm irregularities are Wolf-Parkinson-White syndrome and AV nodular reentrant tachycardia. These conditions are usually caused by extrinsic strands in the myofibers of the heart, resulting in an abnormal short circuit path for electrical impulses in the heart. For example, in certain Wolf-Parkinson-White syndromes, an alternative pathway causes an electrical impulse, which typically travels from the upper chamber to the lower chamber of the heart and back to the upper chamber.
Another common type of arrhythmia is ventricular tachycardia (VT), which may be a complication of a heart attack or a decrease in blood supply to the myocardial region. The latter type of arrhythmia is a life threatening arrhythmia.

[0003] Atrial fibrillation (AF) is the most common type of arrhythmia. This atrial fibrillation has been associated with increased morbidity and mortality due to more thromboembolic events and impaired hemodynamics. In patients with drug-resistant AF, ventricular response can be modulated by catheter ablation or transient mutation of the atrioventricular nodal (AV) region, but such treatments are associated with AF and its associated risk factors. Is a temporary stoppage as it persists afterwards. Pacemakers can be used to prevent sinus bradycardia that induces AF or reduce interatrial transmission delays to prevent recurrence of paroxysmal AF.

[0004] Non-surgical procedures, such as those using drugs, are advantageous for treating arrhythmias. However, some arrhythmias, such as drug-free AF, cannot be treated with drugs and conventionally required surgery. According to these procedures, various incisions are made in the heart to block conduction pathways and divide the atrial area available for multiple undulating reentry, and to completely eliminate arrhythmias. Alternatively, as described in US Pat. No. 4,817,608 to Shapland, et al., A self-implantable cardioverter / defibrillator (AICD) is surgically administered to a patient. Can be implanted in. While these surgical procedures are therapeutic, they can also increase morbidity and mortality, and are also very expensive. The use of any AICD requires significant surgical intervention. However,
For example, older or more ill patients cannot tolerate invasive surgery to remove the tachycardia that causes arrhythmias.

[0005] Several non-surgical, minimally invasive methods have been developed, which are used to locate the heart in response to tachycardia and also eliminate the short-circuiting of these parts. Also used for: According to these methods, the endocardial myocardium is subjected to an electrical energy shock to remove heart tissue in the arrhythmia-producing region and create a scar that blocks the re-entry conduction pathway. The area to be resected is usually first determined by endocardial mapping. This mapping generally involves the percutaneous introduction of a diagnostic catheter having one or more electrodes to the patient and the insertion of the diagnostic catheter through a blood vessel (eg, femoral vein or aorta) into an endocardial site (eg, atrial). Or ventricle) and inducing tachycardia to allow continuous simultaneous recording with a multi-channel recorder at each of several different endocardial locations. Once the tachycardia is located, as shown in this ECG recording,
The tachycardia is so that it can remove the arrhythmia at the located site,
The X-ray image is marked. A conventional electrode catheter with an electrode having a larger surface area than the electrode of the diagnostic catheter then provides electrical energy to the tissue adjacent to the electrode and creates a lesion in the tissue. One or more well-located lesions will create an area of necrotic tissue and eliminate the dysfunction caused by the tachycardia.

[0006] Conventional catheter ablation techniques have used catheters each equipped with a single electrode attached to the tip as a single electrode bar. Other electrode rods have traditionally been provided by a backplate that forms a capacitive coupling of an ablation energy source (DC, laser, radio frequency, etc.) on the outer body part of the patient. Another ablation catheter is Mackey, filed December 8, 1995 and granted a patent.
US Patent Application No. 08 / 569,771), provided with multiple electrodes, such as a catheter, which is incorporated herein by reference in its entirety as described herein. Are known. Still other ablation electrodes with multiple electrodes are described, for example, in Haissaguerre, et al.
et al. And U.S. Patent No. 5,779,669, the disclosure of which is incorporated herein by reference as if described herein.

When the electrodes of the catheter come into contact with heart tissue, ablation is performed by applying energy to the electrodes. This energy may be, for example, high frequency, direct current, ultrasonic, microwave or laser radiation. When RF energy is supplied between the distal end of the standard electrode catheter and the backplate, a local RF heating effect occurs. This creates discrete, well-defined lesions slightly larger than the tip electrode and increases the temperature of the tissue in contact with the electrode. Such elevated tissue temperatures and impedance changes at the electrode / tissue interface are monitored from time to time as disclosed in the above-mentioned McKay patent to dehydrate tissue, blood coagulate, char at electrodes, thrombus formation or catheterization into tissue. Undesirable complications, such as the adhesion of slime, are better prevented. To prevent the temperature rise, the tip electrode / tissue interface is cooled using a saline-perfused catheter, thereby providing more power without causing the aforementioned undesirable complications. .

[0008] The lesions created by radiofrequency ablation are small in size and shallow in depth, which has been found to be one limitation of this method. The conventional idea was to use radiofrequency waves to create either large enough or deep enough lesions to prevent ventricular tachycardia. Following this line of thinking, improvements in electrode design have been related to changes in electrode length, as seen in the direction of catheter extension. The proposed long electrodes will be 6, 8, 10 or even 12 millimeters in length so as to promote the formation of longer lesions and allow more power to be delivered to the tissue through the increased contact area. Was something. However, as the electrode length increases, the flexibility of catheters with such longer electrodes decreases, and both the risk and morbidity of myocardial perforation increase.

[0009] In addition, an open question remains how to ensure good and uniform contact with tissue at each of the long electrodes at the distal end of the catheter. Complicating this problem is the fact that the endocardial myocardium and especially the atrial comb muscles have irregular surfaces. Therefore, in order for each electrode to make good contact with the tissue, a contact pressure must be applied to each electrode over the length of the catheter holding the electrodes.

[0010]

[Problems to be solved by the invention]

What has been required and not used in the prior art is mapping tachycardia nests to form deep lesions in the tissue without significant heating of the tissue at the electrode / tissue interface. Ring-shaped electrode structure. Further needed in the prior art is an electrode structure with axially spaced electrodes for increased diagnostic and ablation applications without sacrificing catheter flexibility. Is a multi-electrode catheter.

[0011]

[Means for Solving the Problems]

In accordance with one aspect of the present invention, a ring-shaped electrode structure with an increased radius dimension is disclosed such that when the electrode is mounted on a catheter, the electrode protrudes from the outer diameter of the catheter. Have been. In other words, the outer diameter of the electrode is
It is larger than the outer diameter of the catheter to which it is attached. The enlarged or upright ring-shaped electrode has a tissue contacting surface, which generally contacts the tissue within the patient before the catheter itself contacts the tissue. Such a configuration ensures good and uniform contact between the tissue and the respective electrodes attached to the distal end of the catheter. Such an arrangement also allows greater pressure to be applied to the tissue with less power than conventional electrode catheter arrangements due to the reduced contact area created by the upright ring electrode. The ring-shaped electrode preferably projects from about 0.25 French to about 2 French from the catheter to which it is attached.

In accordance with another aspect of the invention, the upright electrode has a smooth, curved edge so that tissue is not damaged when the catheter is advanced and retracted within the patient. I have.

[0013] Other objects and aspects of the present invention will become apparent from the following detailed description of preferred embodiments, provided in conjunction with the accompanying drawings.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

By way of overview and introduction, FIG. 1 shows a ring-shaped electrode structure 10 that is carried by a combined diagnostic (mapping) and ablation catheter 12 and extends along a distal portion 14 thereof. . Preferably, the tip electrode 16 is provided at the distal end of the catheter, but it may be of conventional design. An assembly particularly suitable for the distal tip electrode 16 is disclosed in U.S. Pat. No. 5,685, issued Nov. 11, 1997, which is hereby incorporated by reference as if fully set forth herein. No. 878. Conventionally, this tip electrode 1
6 is made of platinum and is attached directly to the distal end of catheter 12. Alternatively, a refractive material (not shown) is interposed between the tip electrode 16 (or another electrode) and the catheter 12 so that the energy for ablation is applied to the electrodes 10 and 16 or from the heat immediately thereafter. The holding catheter may be protected.

The ring-shaped electrode structure 10 has the same inner diameter as the conventional electrode, that is, the catheter 1.
Preferably, it has an inner diameter slightly smaller than the outer diameter of the second. Each ring-shaped electrode is, for example, a brazed or welded conductive wire 18.
Through the window 22 and into the lumen 20 of the catheter, the distal portion 1 of the catheter.
By temporarily pulling 4 to reduce its outer diameter, causing the ring-shaped electrode 10 to slide over the catheter 12 and then relaxing the tension in the catheter when the ring-shaped electrode is positioned above the window 22, It can be mounted on the catheter 12 (see FIG. 2). Each of the ring-shaped electrodes 10 is attached along the inner diameter of the catheter 12 when the ring-shaped electrode 10 is attached to the catheter, preferably in a space in the outer wall of the catheter, or a window. A temperature sensor 23 corresponding to the hole 22 is provided. This temperature sensor 23 may be a thermocouple, a thermistor or a resistive thermal device ("RTD"). Each temperature sensor 23 has an associated conductive wire (not shown) that extends proximally to the connector.

According to the present invention, the ring-shaped electrode 10 has a radial direction R (see FIG. 2).
Measured, the contact surface 24 is thick enough to protrude from the catheter 12. As a result, the contact surface 24 will generally be located where the tissue 26 has an irregular surface.
It will come into contact with the tissue 26 before the catheter 12. Force is applied in a conventional manner from the proximal end 28 of the catheter 12 to ensure good contact with tissue,
The electrodes 10, 16 are pressed against the tissue 26. The upright electrodes concentrate the points of tissue contact at the surface 24 rather than at the insulating portion 30 of the distal portion 14 of the catheter. In contrast, conventional electrode designs are such that they are flush with the outer diameter of the catheter, and thus make significant contact with the tissue 26. The applied pressure is inversely proportional to the size of the contact area (P = F
/ A), the upright ring-shaped electrode 10 of the present invention achieves a pressure comparable to that achieved with conventional designs with a fairly small additional force. by this,
Benefits are provided for both mapping and ablation procedures. For example, a catheter containing electrode 10 is less sensitive than an optimal tissue contact pressure situation.
Because the larger electrode surface area of this upright electrode is available for contacting tissue, more high frequency energy is radiated from the electrode 10, especially from the electrode edges, and the electrode is active on irregular tissue surfaces. That the contact pressure at the electrode 10 concentrates instead of spreading the reduced pressure over a larger contact area including both the electrode and the insulating region 30 (as in conventional designs). Is likely to occur with a very high probability.

Surprisingly, with the upright ring-shaped electrode 10, at comparable surface tissue temperatures and ablation times, the lesions formed are much deeper than was possible with conventional electrode designs. And wide (shown along the X and Y axes, respectively, of FIG. 1). In vitro experiments showed that the volume of a lesion created using a conventional electrode (2.5 mils in thickness) mounted flush with the catheter could be measured using the upright ring-shaped electrodes ( (1 mil = 0.0254 mm) by comparing to the volume of the lesion formed using a 10 mil thickness.
Each ring-shaped electrode is the same length (shown along the X axis in FIG. 1,
4 mm) and attached to a separate catheter (outside diameter is 91 mil (7 French)). To sense surface tissue temperature, a thermocouple was attached to the inside diameter of each ring-shaped electrode at the centerline of the electrode. Once attached, the conventional electrode was flush with the catheter, and the upright ring-shaped electrode 10 protruded approximately 15 mils (ie, greater than 1 French). A 15 gram force was applied to each electrode and the force was maintained in contact with the tissue sample. Also, energy was delivered to the electrodes for 60 seconds while flowing 1400 milliliters of saline using controlled temperature feedback set at 65 ° C.

More specifically, in vitro experiments have shown that a tissue consists of a cross section of bovine striated muscle approximately 1 inch long, approximately 0.75 inches wide and approximately 0.50 inches deep. The foci of the specimen were examined. An immersion fitting was used to position the electrode so that one side of the thermocouple was in contact with the tissue specimen. In addition, 1
A 5 gram weight was applied to the catheter shaft on one side of the electrode to hold the electrode firmly on the specimen. The fixture allows additional thermocouples to be positioned and aligned in the analyte just below the center of the axis and radius of the electrode.

With the tissue specimen and the electrodes mounted and held as described above, the assembly was equilibrated to an initial impedance of 100 ohms and circulated at 1400 ml / min by a peristaltic pump at 37 ° C. Physiological saline / DI
Submerged in tank of water mixture. Ablation procedures and data collection were initiated after the assembly was equilibrated with a saline / DI water mixture. Ablation energy was applied to the specimen for a predetermined duration (eg, 60 seconds, 90 seconds, and 120 seconds) in a temperature controlled mode at a set temperature of 65 ° C.

Next, a radionics brand lesion generator (model 3) equipped with a personal computer for controlling the removal procedure and retrieving the lesion parameter data
Using E), a comparison test between the electrode 10 according to the present invention and a conventional electrode was performed.
The results are as follows.

[Table 1] Where D is the cross-sectional depth from the center of the surface burned to the deepest edge of the lesion, W is the width of the surface, L is the cross-sectional length at the longest edge,
The calculated lesion volume is equal to (π / 6) (DWL).

The upright electrode according to the invention has three different ablation duration periods (each
For each of the measured parameters, the conventional electrodes were outperformed, as shown in FIGS. 4 to 6, which show the results for the 60, 90 and 120 second periods. Here, the "thick" electrode is electrode 10 and the "thin" electrode is a conventional electrode.

In order to achieve the results obtained with the electrode 10, conventional electrodes have been used for longer periods of time.
It should be energized or endured with greater risks such as tissue dehydration, electrode charring, blood clotting and the like. Therefore, the ring-shaped electrode structure 10 can transmit more power without increasing the tissue surface temperature beyond a clinically acceptable level, and further promote lesion formation, as compared with the conventional electrode configuration. Is done. In addition, increased power supply was obtained without increasing the length of the electrodes and without compromising the flexibility of the catheter. as a result,
A ring-shaped electrode 10 with a thickness and axial length suitable for high power ablation can be provided. Since the contact area of the ring electrode 10 is smaller than that of the conventional flush type electrode, the ring electrode 10 can map a tachycardia without blurring the original position of the sensed signal. Are also suitable. The smaller contact area 24 of the ring electrode 10 allows for both better signal sensing (like a small antenna) and ablation.

The power to the electrode 10 reduces the risk of the electrode 10 adhering to the tissue to be ablated and minimizes any tendency that the tissue may be wrapped around the tissue, for example as a result of tissue dehydration. To a duration of about 120 seconds or less,
Can be supplied. As the resection time increased more than, for example, 60 seconds, the lesion cross-section was observed to become progressively denser and more elastic to the touch, indicating increased tissue dehydration and It may be an indicator of an increase in incidental lesion density. This suggests that the last lesion volume measured is smaller than the actual volume of tissue affected by the procedure, especially if the duration of the ablation energy cycle is longer. is there.

FIG. 3 illustrates a modification of the ring-shaped electrode illustrated in FIG. In FIG. 3, the ring electrode 10 'has no sharp edges that may cause tissue damage when the catheter 12 is moved within the patient. In particular, the ring-shaped electrode 10 'has a smooth and curved edge. Of course, pods can be used in this embodiment or in the embodiment of FIG. 1 to ensure atraumatic delivery and retraction of catheter 12.

Although two ring electrodes 10 are shown in series and spaced along the catheter 12, the catheter 12 may include only one or any number of the ring electrodes 10. Can be held. These ring-shaped electrodes 10 are spaced apart from each other (and the tip electrode 16) by an insulating region 30,
Each may have an arbitrary axial length. In order to create a linear lesion upon ablation, these electrodes are placed, for example, 1 to 3 mm apart, depending on the electrode thickness (measured radially) and the range of applied power be able to. The placement of the electrodes can also be established with respect to diagnostic considerations, such that these electrodes are properly positioned to map electrical signals inside the heart.

Due to the increased lesion volume created by the ring electrode of the present invention, as compared to conventional electrodes, the increased inter-electrode distance along the distal end of the catheter shaft and / or the distance between the electrodes 10 The axial length of the electrode can be reduced without sacrificing the ability to create a continuous linear lesion below the region, ie, the insulating region 30. Regardless of whether the inter-electrode distance increases or the electrodes become shorter in the axial direction, the electrode structure of the present invention increases the flexibility of the distal end by exposing most of the insulating region 30 in the catheter 12.

When the thickness of the ring-shaped electrode 10 in the radial direction is multiplied by its axial length, that is, the length along the x-axis (corresponding to the extending direction of the catheter) in FIG. 1, the volume of the ring-shaped electrode is obtained. Can be The thickness of the ring electrode 10 is such that the volume of the ring electrode is the tip electrode 1.
6 can be chosen to ensure that it is approximately the same as the volume of 6 or some other predetermined volume. As explained earlier, it is generally preferred to have an axially short electrode 10 so that the focus of the tachycardia signal does not blur beyond the length of the electrode. However, the electrode 10 cannot be made to project so far from the catheter, or the catheter will not be able to easily navigate into the desired passage. Therefore, the designer must balance the axial length of the ring-shaped electrode 10 with its radial thickness to achieve a predetermined volume. The volume of the ring-shaped electrode is preferably made to substantially match the volume of the tip electrode 16, and more preferably is made to substantially match the volume of the tip electrode.

In operation, the site of arrhythmia occurrence is determined by positioning the distal portion 14 of the catheter 12 within the heart and sensing electrical signals using the ring electrode 10. Once the site of arrhythmia has been located, a power source (not shown) is turned on and energy is applied to the electrodes 10, 16 in either a constant voltage, power or temperature mode, as described in detail in the McKay patent. Is given. These electrodes may be energized simultaneously, sequentially, or according to some other pattern. Radio frequency energy, usually in the range of about 250 kHz to 500 kHz, is applied to the electrodes 10, 16 to ablate the tissue. Energy flows from the electrodes 10, 16 through the tissue 26 to the return plate, which is connected to the ground potential of the power supply, completing the circuit. The current flowing through this circuit to the tissue 26 causes heating that will destroy the tissue 26 near the electrodes 10, 16 and ideally at the tachycardia site. If successful, the tachycardia can be permanently cut off and the patient will heal.

The catheter according to the invention can be wrapped with a guiding sheath sized to accommodate the ring electrode 10. Therefore, a 7 French catheter would have 7.
If a 5-french ring-shaped electrode 10 is provided, its guiding sheath is 8
It may be French, or it may be a custom guide sheath that is dimensioned to be greater than 7.5 French.

While the preferred embodiment of the invention has been thus described, it should be understood that the foregoing arrangement and system are merely illustrative of the principles of the invention, and that other arrangements and systems may be used. It should be understood that the system can be devised by those skilled in the art without departing from the spirit and scope of the invention, as set forth in the following claims.

[Brief description of the drawings]

FIG. 1 is a plan view showing a ring-shaped electrode of the present invention held by an ablation catheter.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a sectional view of a modification of the ring-shaped electrode structure according to the present invention.

FIG. 4: Ablation energy is applied for 60 seconds and controlled to not exceed 65 ° C.
Figure 4 shows the results of an in vitro comparative excision experiment.

FIG. 5: Ablation energy is applied for 90 seconds and controlled not to exceed 65 ° C.
Figure 4 shows the results of an in vitro comparative excision experiment.

FIG. 6 shows the results of an in vitro comparative ablation experiment in which ablation energy was applied for 120 seconds and controlled not to exceed 65 ° C.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Isagur Michel Michelle France Thalens F-33400 Liu Angel Dumad 47 (72) Inventor Collins Dennis United States New Hampshire 03038 Delhi, Poundview 6 (72) Inventor Falwell Gary S United States of America New Hampshire 03103 Manchester, Trolley Street 28 (72) Inventor Gibson Charles, USA 02148 Malden, Hill Street 73 (72) Inventor Patterson Donald, United States of America Massachusetts 01863 North Chelmsford, Lan Prayer Lane 37 (72) Inventor Stevens-Wright De I over United States Massachusetts 01845 North & Bar Candle Stick load 175 (72) inventor Karakojian Serkis United States Massachusetts 02178 Belmont, glove stream door 25 F-term (reference) 4C060 KK03 KK09 KK13 MM25

Claims (12)

[Claims] An electrode catheter for ablating tissue within a patient, comprising: a long catheter having a distal portion having a predetermined outer diameter and a lumen therein; and a long catheter retained in the distal portion. At least one ring-shaped electrode, a conductive wire disposed in the lumen and having one end connected to the ring-shaped electrode, and a temperature sensor disposed below the ring-shaped electrode The ring-shaped electrode has a thickness such that the electrode protrudes in a direction substantially transverse to the direction of extension of the catheter by a distance sufficient to separate the distal portion of the catheter from the tissue to be ablated. An electrode catheter comprising: 2. The electrode catheter according to claim 1, wherein the ring-shaped electrode has an inner diameter smaller than the predetermined outer diameter of the catheter. 3. The electrode catheter according to claim 1, wherein the temperature sensor is selected from the group consisting of a thermocouple, a thermistor, and a resistive thermal device. 4. The electrode catheter according to claim 1, wherein the ring-shaped electrode projects at least 4 mils radially from the catheter. 5. The electrode catheter according to claim 1, wherein the ring-shaped electrode has a smooth curved edge. 6. The electrode catheter according to claim 1, wherein there are a plurality of ring-shaped electrodes held by the catheter. 7. The electrode catheter according to claim 1, wherein the catheter is dimensioned to accommodate the temperature sensor and has a slot that can hold the ring electrode coaxially with the catheter. . 8. The electrode catheter according to claim 7, wherein the ring-shaped electrodes are spaced by an insulating region in the extension direction of the catheter. 9. The electrode catheter according to claim 1, further comprising a tip electrode at a distal tip of the catheter. 10. The electrode catheter according to claim 9, further comprising a refractive element interposed between the distal tip of the catheter and the tip electrode. 11. A ring-shaped electrode having a length in a direction in which the catheter extends, and a thickness of the ring-shaped electrode is obtained by multiplying the length by the thickness to a predetermined volume. 2. The electrode catheter of claim 1, wherein the catheters are selected to be equal. 12. The electrode catheter of claim 11, further comprising a tip electrode having a volume at a distal tip of the catheter, the volume of the tip electrode being substantially equal to the predetermined volume.