RU2420245C2 - Catheter with thermoballoon for isolation of pulmonary vein orificis - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medical equipment, namely to devices for treatment of auricle fibrillation. Device contains catheter in form of external tube and internal tube, located inside external tube, filled with electroconductive liquid thermoballoon, two successively connected electrodes, located inside thermoballoon on catheter and having electroconductive connection with outlets of high-frequency current generator, temperature sensor, located inside thermoballoon and having electroconductive connection with temperature metre, whose outlet is connected with controloutlet of high-frequency generator, guiding part of catheter, protruding beyond thermoballoon coat, wire conductor, freely moved in internal tube of catheter, device for mixing fluid inside balloon. In the space between internal and external tubes of catheter located are additional tubes, intended for conductors, connecting electrodes inside balloon with outlets of high-frequency current generator, and for conductors of temperature sensor, and two additional tubes, connecting internal space of thermoballoon from one side and device of liquid supply from the other side. Thermoballoon coat from two sides is fixed on external tube of catheter before guiding part of catheter, one of the tubes, connecting internal space of thermoballoon with device for liquid supply has connection with device of liquid mixing.

EFFECT: application of the invention will make it possible to increase device reliability due to constructive catheter implementation.

6 cl, 1 dwg

Description

 The invention relates to medical equipment, and more specifically to devices for treating atrial fibrillation by creating thermal damage to the myocardium, blocking the propagation of excitation waves from the mouth of the pulmonary veins.

Known ablation electrode-catheter containing in the distal part a miniature 4 mm metal electrode, and a method of catheter ablation for the treatment of atrial fibrillation by isolating the mouth of the pulmonary veins, which are currently widely used [1, 2]. Isolation of the pulmonary vein region in the left atrium is performed by a miniature electrode, for which a high-frequency electric current is supplied between the above electrode and an electrode with a large contact surface, which is placed on the patient’s body. An electric current causes resistive heating of the myocardial tissue adjacent to the electrode. The main heat generation occurs within 1-2 mm from the electrode surface; tissue heating in depth occurs through the process of heat diffusion. As a rule, the depth of damage does not exceed 4 mm. The result is generally achieved by creating a vast area of damage, consisting of many ablation points around the pulmonary vein collectors in the form of linear ablation sections connecting the pulmonary veins, “exposure lines” in the area of the roof of the left atrium and along the posterior wall between the pulmonary vein collectors. The operation is performed non-invasively, the operating space is visualized using x-rays or navigation systems. The structurally small size of the electrode is a disadvantage of catheter ablation technology. Damage at the point of impact caused by such an electrode is small in size, has significant temperature gradients, and the complete isolation procedure requires many precision actions. If cooling of the electrode is used, then in the subsurface layer of the affected area, zones of elevated temperature are created, and there is a possibility of damage to the integrity of the atrial wall or the formation of fistulas in the esophagus. In addition, with insufficiently accurate positioning of the ablation electrode, there is a possibility of postoperative pulmonary vein stenosis. There are frequent cases of electrode sticking. The duration of the operation is several hours and requires highly qualified personnel and the accuracy of all elements of the procedure.

Another technical solution is also known: a catheter with a cooled cryoballon (Arctic Front, Cryocath ™) [3]. This technical solution is a new technology for the isolation of pulmonary veins, good results were obtained [4]. The cryoballon has 2 sizes for the diameter of the shell: 23 and 28 mm. For security, the shell is made in two layers. The cryoballon is cooled with liquefied nitrous oxide N ₂ O to minus 80 ° C. The ablation zone is created in the form of a ring around the mouth of the pulmonary veins in one cooling cycle. The disadvantage of this device is that the use of cryoballon for isolation of the pulmonary veins in some cases causes paralysis of the phrenic nerve, and there is no long-term effect. In addition, due to the significant temperature gradient, damage uneven in depth is obtained, which apparently leads to the restoration of myocardial conductivity over time. Penetration of toxic refrigerant into the patient is not permitted.

The main disadvantage of the known technical solutions is the low level of safety and reliability.

The closest analogue (prototype) of the device proposed in this invention is a catheter with a thermal balloon heated by RF current: US patent No. 7,112,198 (Radio-frequency heating ball catheter) [5]. The specified device contains a catheter with a channel for supplying saline solution, conductors for connection with a temperature sensor, a temperature meter, a conductor to the electrode located inside the thermowell, a shell of the thermowell, an electrically conductive contact (electrode) inside the balloon, a temperature sensor, contact (electrode) on the patient’s skin, a generator RF current, a device for mixing liquid in a cylinder. A thermal balloon catheter consists of an external and an internal tube. The elastic shell of the thermowell is fixed on the edge of the outer tube on one side and at a certain distance from the end of the inner tube on the other side.

The shell of the thermal bulb is pumped up and brought into contact with the area of the alleged damage. The thermal bulb is pumped to a size of 20-40 mm in diameter. A high-frequency current with a frequency of 1.8–13.56 MHz is transmitted between the electrode located inside the container and the electrode on the surface of the patient’s body, causing heat generation according to the Joule-Lenz law and heating of the liquid inside the container. The dielectric shell of the thermowell does not impede the passage of electric current, due to the fact that the capacitive reactance of the shell to the current of high frequency is negligible. The temperature inside the cylinder is controlled by a temperature sensor. The part of the inner tube protruding from the balloon, which is inserted into one of the pulmonary veins, serves to hold the balloon opposite the mouth of the pulmonary veins in the ablation region. For the manufacture of thermoball components, materials with low electrical and thermal conductivity are used. For the directional advancement of the catheter to the mouth of the pulmonary veins, a wire conductor is used that moves freely in the inner tube of the catheter. In order to reduce the stray currents of high frequency through a metal conductor, it is coated with an insulating composition, and the return end is grounded. The effect of gravity on a heated liquid causes its convective redistribution and warmer layers move upward, which leads to a decrease in the efficiency of ablation. To equalize the temperature inside the cylinder, the liquid is mixed using a mechanically rotating structure, or by vibration.

A catheter with a thermal balloon heated by a high-frequency current was successfully tested under clinical conditions [6], and a long-term effect was achieved in 92% of patients. The balloon was visualized by fluoroscopy. A radiopaque liquid was injected into the balloon. The thermal balloon was placed with emphasis in the mouth of the pulmonary veins to a state of occlusion, which was controlled by the administration of a radiopaque substance through the inner tube of the catheter. The solution was mixed inside the balloon using a vibrator connected to the external lumen of the catheter, connected with the internal volume of the balloon.

The disadvantage of the prototype is the low level of security caused by the need to use excessively high frequencies that cause increased energy dissipation to stray heat the patient’s body tissue outside the ablation zone and a high level of electromagnetic interference for recording equipment. Another disadvantage is the low structural rigidity inside the container. Among the disadvantages is the low level of reliability associated with the presence of moving parts of the elements of the mechanical solution mixing system inside the container.

The technical result of the proposed device is to increase the degree of security and to increase the reliability of the device. The technical result in increasing the degree of safety is obtained by reducing the impact of high-frequency current and thermal energy on the patient’s tissue outside the ablation zone and increasing the rigidity of the structure, and increasing reliability by eliminating the moving structural elements in the container.

For this, additional tubes are introduced into the inner space of the external tube of the catheter or special channels are created in the catheter body. Both ends of the shell of the bulb are fixed on the outer tube of the catheter. The part of the catheter protruding beyond the shell of the thermal balloon is a continuation of the main body of the catheter, and due to the integrity of this design, its necessary strength is achieved.

Another annular electrode is introduced into the thermowell, which is arranged in series with an existing electrode. Both electrodes are connected to the outputs of the high-frequency current generator by conductors, which are located either in additional tubes or in free space inside the outer tube of the catheter. The conductive connections of the temperature sensor to the temperature meter are also located either in additional tubes or in free space inside the external tube of the catheter. The output of the temperature meter is connected to the input of a high-frequency current generator and the temperature measurement results are used to control the power level.

The inner space of the thermoballon shell is connected to the electrically conductive fluid supply device with two additional tubes, so that the sides of the fluid supply device are connected together, and their entrances to the inner space of the thermoballion shell are separated. One of the tubes is connected to a peristaltic pump. When you turn on the peristaltic pump, the liquid circulates through the tubes through the inner space of the shell of the bulb, causing it to mix. Moreover, the peristaltic pump can periodically change the direction of rotation.

The frequency of the high-frequency current generator is reduced and set in the range from 400 to 500 kHz, lowering the frequency reduces the level of spurious radiation. A lower frequency is impractical because of the electrolysis processes at the electrodes that begin at the same time. The location of both electrodes inside the bulb shell leads to a reduction in the required energy level to 30-100 watts. The operating current is almost completely concentrated inside the container and is used only for heating the electrically conductive liquid. There is no possibility of heating the wire conductor. Control of the output power eliminates the possibility of overheating of the myocardial tissue, which allows you to get uniform damage with high residual strength of the tissues of the atria. To create these exposure modes by power, operating frequency and power control using temperature sensors, standard ablators designed for 4 mm catheter electrodes can be used.

The invention is illustrated in the drawing, which shows a diagram of the device and its connection: 1 - device for supplying electrically conductive liquid; 2 - high frequency current generator; 3 - wall of the left atrium; 4 - valve; 5 - peristaltic pump, reversible; 6 - catheter; 7 - 1st electrode; 8 - 2nd electrode; 9 - area of myocardial damage; 10 - the output of the tube 13 into the inner space of the shell of the bulb 18; 11 - tube fixation of the catheter with a balloon in the pulmonary vein 20; 12 - wire conductor; 13 - inner tube for supplying electrically conductive liquid to the thermowell; 14 - inner tube for supplying electrically conductive liquid to the thermowell; 15 - valve; 16 - the exit of the tube 14 into the inner space of the shell of the bulb 18; 17 - inner tube for the conductor; 18 - shell thermoball; 19 - temperature sensor; 20 - superior pulmonary vein; 21 - temperature meter; 22 - left atrium in the area of the mouth of the pulmonary veins; 23 - lower pulmonary vein.

Description of the device.

A catheter with a thermal balloon to isolate the mouth of the pulmonary veins contains a catheter in the form of an external tube and internal tubes that are located inside the external tube. The thermal bulb is made in the form of an elastic shell filled with an electrically conductive liquid. The shell of the thermal balloon is fixed on both sides to the outer tube of the catheter so that the protruding portion of the catheter remains. The protruding portion of the catheter, extending beyond the envelope of the balloon, is a continuation of the catheter. The device comprises a wire guide mounted and freely movable in one of the inner tubes of the catheter. The device contains first and second ring electrodes located on the catheter sequentially inside the thermowell and having an electrically conductive connection with the outputs of the high-frequency current generator, a temperature sensor located inside the thermoballion and having an electrically conductive connection with a temperature meter, the output of which is connected to the control input of the high-frequency current generator.

A space is provided in the space between the inner and outer tubes of the catheter for the location of the conductors connecting the first and second electrodes inside the balloon to the outputs of the high-frequency current generator, and a place for the conductors of the temperature sensor. Two inner tubes connect the interior of the bulb on one side to the fluid supply on the other. One of the tubes connecting the interior of the bulb to the fluid supply device is connected to a fluid mixing device. The fluid mixing device is designed as a peristaltic pump.

The proposed device operates as follows. A catheter 6 with a balloon 18 to isolate the mouths of the pulmonary veins is inserted into the left atrium 22 so that the protruding part of the catheter 11 fits into one of the pulmonary veins 20 or 23. Fill the membrane shell 18 with electrically conductive fluid to a size sufficient to overlap the mouth of the pulmonary veins 3. This is done using the device for supplying electrically conductive fluid 1, through the open valve 4 and the inner tubes of the catheter 13 and 14, designed to supply electrically conductive fluid to the thermo-cylinder 18. The ends of the tubes 13 and 14 have outputs 10 and 16, respectively but, into the interior of the bulb in the form of holes. The valve 15 connected to the tube 13, open if there is a need to bleed air. After filling the shell of the bulb 18 valves 3 and 4 are closed. The tube 13 is introduced into connection with a peristaltic pump 5.

The filled thermoballon 18 is pressed against the mouth of the pulmonary veins for 20 and 23 seconds until occlusion (complete overlap) is achieved. The degree of occlusion is controlled by fluoroscopy, for which a radiopaque substance is injected into the pulmonary veins 20 and 23 through the inner tube 17 of the catheter 6. To facilitate the process of moving the catheter to the desired position, use a wire conductor 12 that moves freely in the inner tube 17 of the catheter. The protruding part of the catheter 11, inserted into one of the pulmonary veins, prevents the displacement of the catheter from the working position.

Turn on the high-frequency current generator 2 and through the ring electrodes 7 and 8 having an electrically conductive connection with the outputs of the above generator, pass the high-frequency current that flows through the electrically conductive fluid surrounding the electrodes. The high-frequency current causes resistive heating of the electrically conductive liquid inside the shell of the thermoballion 18. The temperature inside the thermoballion 18 is controlled by a temperature meter 21 having an electrically conductive connection through the internal space of the catheter 6 to the temperature sensor 19 located on the catheter inside the thermoballion 18. The power of the high-frequency current generator 2 is controlled by orienting to the temperature meter 21. The fluid inside the bulb 18 is mixed, achieving a uniform temperature distribution over the volume . The fluid mixing unit comprises a peristaltic pump 5 and two elastic tubes 13 and 14, which, on the one hand, have entrances to the interior of the balloon through openings 10 and 16, respectively, and are connected together on the other hand. The peristaltic pump 5 is turned on, and the liquid begins to cycle through the tubes 13 and 14 through the openings 10 and 16, through the inner space of the cylinder 18. Through one tube, the liquid enters the cylinder, the other from the cylinder. The outflow and inflow are the same in volume and do not cause a change in the geometric dimensions of the cylinder.

During heating, a temperature gradient is formed between the liquid of the thermoballion 18 and the adjacent tissues of the myocardium 3. The temperature gradient according to the Fourier law causes the heat of the heated fluid to diffuse through the shell of the thermoballon 18 into the adjacent tissues of the myocardium 3. The degree of heating of the fluid and the thermal resistance of the shell of the thermoballion 18 are selected so that to cause the necessary degree of coagulation of the protein in the annular region of contact of the shell of the thermoballon 18 with the myocardium 9. Parts of the surface of the shell of the thermoballon 18, pulsing with blood atrium 22, have a significant temperature drop and do not cause heat damage to the blood cells. A more significant temperature difference is due to the convection type of heat transfer at the boundary of the bulb with blood.

An increase in the degree of safety is achieved by reducing the level of exposure to thermal energy on the internal organs of the patient outside the ablation zone and increasing the rigidity of the structure, while increasing the reliability is ensured by the absence of mechanically moving structural elements inside the container.

According to the proposed technical solution, experimental samples of catheters with a thermal balloon for the isolation of pulmonary veins were made. The catheter consists of an external tube and seven internal tubes. The shell of the thermal bulb is made of heat-resistant elastic material. To control the temperature, a copper-constantan thermocouple with a temperature coefficient of 39 μV / K was placed inside the shell. Two 3 mm long stainless steel ring electrode contacts are located 5 mm apart. An infusion solution of 0.9% sodium chloride was used as an electrically conductive fluid. The shell was filled to a diameter of 20-40 mm. As a high-frequency current generator, we used the standard computerized 50-ED-01 Biotok conductive heart path electrode with a maximum output power of 100 W with a generation frequency of 440 kHz, with an integrated temperature meter and a peristaltic infusion pump, which is included in the generator set.

The results of experimental studies:

- the required power of the high-frequency current generator compared to the prototype is reduced to 30-100 W, depending on the size of the filled shell of the thermoball;

- the wire guide inside the catheter and protruding from it does not cause heating of the tissues in contact with;

- the active resistance between the electrodes of the thermal bulb ranged from 35 to 65 Ohms, there was a decrease in temperature during heating of the thermal bulb;

- the frequency is reduced to 440 kHz: energy dissipation is reduced by reducing the frequency and reducing the area of application of the electrodes;

- obtained effective mixing with achieving good uniformity of temperature distribution;

- good rigidity of the catheter structure is ensured: a catheter uniform in thickness;

- since the passage of current through the membrane of the catheter is not necessary, the thickness of the membrane is increased to 100 μm, which also reduces heat loss due to parasitic heating of the blood;

- the damage is uniform, the damaged tissue is not exposed to excessively high temperatures, and its strength after exposure remains high,

Since the thermal performance of the bulb is directly identical to the prototype, it is possible to predict the high clinical efficiency of the proposed device, with confirmation of the results obtained on the prototype and presented in [6]. The authors of this work cite 92% success in long-term follow-up, which is currently the best result in the treatment of atrial fibrillation.

Literature

1. CELSIUS Ablation Catheters for Large Hearts [Electronic resource]. - Access mode: http://www.legmed.ru/catalogue/details.html?item=5300&section=20. - free.

2. Revishvili A.Sh., Rzayev F.G., Dzhetybaeva, S.K. Electrophysiological diagnostics and interventional treatment of complex forms of cardiac arrhythmias using a three-dimensional electroanatomical mapping system // Bulletin of Arrhythmology. - 2004. - No. 34. - S. 32-37.

3. Marcus L. Koller and Burghard Schumacher. Cryoballoon ablation of paroxysmal atrial fibrillation: bigger is better and simpler is better // E.H.J. - 2009. - No. 30. - P. 636-637.

4. Kyoung-Ryul Julian Chun, Boris Schmidt, Andreas Metzner, at. al. The “single big cryoballoon” technique for acute pulmonary vein isolation in patients with paroxysmal atrial fibrillation: a prospective observational single center study // E.H.J. - 2009. - No. 30. - P.699-709.

5. Shutaro Satake. Radio-frequency heating ball catheter. United States Patent 7, 112, 198, September 26, 2006.

6. Hiroshi Sohara, Hiroshi Takeda, Hideki Ueno, Toshiyuki Oda, Shutaro Satake. Feasibility of the Radiofrequency Hot Balloon Catheter for Isolation of the Posterior Left Atrium and Pulmonary Veins for the Treatment of Atrial Fibrillation // Circ. Arrhythmia Electrophysiol. - 2009. - No. 2. - P.225-232.

Claims (5)

1. A catheter with a thermal balloon for isolation of the mouths of the pulmonary veins, containing a catheter in the form of an external tube and an internal tube that is located inside the external tube, a thermoballion filled with electrically conductive fluid designed to create thermal contact with the area of damage, the first electrode located inside the thermoball and having an electrically connection to one of the outputs of the high-frequency current generator, a temperature sensor located inside the bulb and having a conductive connection to measure a temperature element, the output of which is connected to the control input of the high-frequency generator, the guide part of the catheter protruding from the shell of the thermal balloon, designed to prevent displacement of the catheter with the thermal balloon from a predetermined position opposite the mouth of the pulmonary veins, a wire conductor freely moving in the inner tube of the catheter and designed to facilitate procedures for installing a catheter with a thermal balloon in a predetermined position, a device for mixing fluid inside the balloon to eliminate temperature grad ient, characterized in that the second electrode is installed in series with the first electrode inside the balloon, having an electrical conductive connection to the other output of the high-frequency current generator, which generates a high-frequency electric current between the first and second electrodes through the electrical conductive fluid inside the thermal balloon, causing it to heat up in space between the inner and outer tubes of the catheter there are additional tubes for conductors connecting the electrodes inside the balloon to the gene outputs a high-frequency current generator, additional tubes for the conductors of the temperature sensor and two additional tubes connecting the inner space of the thermowell on one side and with the fluid supply device on the other hand, the shell of the thermowell on both sides is fixed to the outer tube of the catheter directly in front of the catheter guide, one of the tubes connecting the inner space of the thermowell with a fluid supply device is connected to a fluid mixing device. 2. The device according to claim 1, characterized in that the shell of the bulb is made of flexible heat-resistant material. 3. The device according to claim 1, characterized in that the guide part of the catheter protruding beyond the membrane of the balloon, designed to fix the position of the catheter with a thermal balloon in a predetermined position opposite the mouth of the pulmonary veins is a continuation of the external tube of the catheter. 4. The device according to claim 1, characterized in that the fluid mixing device generates a peristaltic wave, creating a cyclic fluid movement through the tubes through the interior of the bulb. 5. The device according to claim 1, characterized in that the frequency of the high-frequency current generator is set in the range from 400 to 500 kHz.

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