WO2007010073A2

WO2007010073A2 - Apparatus and method for the thermal protection of the oesophagus

Info

Publication number: WO2007010073A2
Application number: PCT/ES2006/000430
Authority: WO
Inventors: Enrique BERJANO ZANÓN; Fernando Hornero Sos
Original assignee: Universidad Politecnica De Valencia; Fundación Comunidad Valenciana Hospital General Universitatio
Priority date: 2005-07-22
Filing date: 2006-07-21
Publication date: 2007-01-25
Also published as: ES2267396A1; WO2007010073A3; ES2267396B1

Abstract

The invention relates to an apparatus which is used to cool part of the oesophagus in order to prevent injury thereto owing to overheating during a hyperthermal ablation procedure close to the oesophagus. The inventive apparatus comprises a flexible element (1, 11) which is configured to be inserted into the patient's mouth or nose and which has one part that is intended to be placed in contact with the oesophagus. The aforementioned flexible element comprises a coolant circulation circuit which is configured such that the coolant circulates through the part that is intended to be placed in contact with the oesophagus. The flexible element can be connected to a coolant-pumping device (7, 17) and is equipped with temperature-detection means. The invention also relates to an associated method.

Description

APPARATUS AND METHOD FOR THERMAL PROTECTION OF THE ESOPHAGUS

TECHNICAL FIELD OF THE INVENTION

The invention is encompassed in the field of organ protection systems in relation to surgical or therapeutic interventions.

BACKGROUND OF THE INVENTION

The esophagus is an organ of vital importance in the maintenance of life. At the retrocardial level, its walls are very close to the heart, and in particular to the free wall of the left atrium (K. Lemola, M. Sneider, B. Desjardíns, I. Case, J. Han, E. Good, K Tamirisa, A. Tsemo, A. Chugh, Bogun F _r F Jr Pelosi, E. Kazerooni, F Morady, H. Oral: "Computed tomographic analysis of the • anatomy of the left atrium and the esophagus: implications for left atrial catheter ahlatϊon " _f Circulation, vol. 110, pp. 3655-3660, 2004). Recently, different radiofrequency or microwave ablation techniques are allowing to solve clinical problems in a minimally invasive way, thus avoiding the aggression of major surgery. Thus, for example, the creation of linear lesions in the atrium can allow the elimination of atrial fibrillation, which is the most frequent arrhythmia in daily clinical practice (F. Hornero, JA Montero, 0. Gil, R. García, F Atienza, R. Paya, JL Pérez, A. Quesada, S. Cánovas, MJ Dalmau, M. Bueno: "Surgery ablation of bypass fibrillation with eplcardial and endocardial biauricular radiofrequency: initial experience", Revista Española de Cardiología, vol. 55 , pp. 235-244, 2002). These thermal injuries are being done through different energy sources such as radiofrequency, microwave, laser or ultrasound; . and it is possible to perform them intraoperatively, that is, during a cardiac intervention, or by non-surgical procedures using percutaneous catheters designed for this purpose. Both systems, especially the surgical one, are offering very high success rates when radiofrequency currents are used as a source of energy. However, in recent times, very important problems, often lethal to the patient, associated with this technique and due to esophageal perforations have been recorded (B. Sonmez, E. Demirsoy, N. Yagan, M. Unal, H Arbatli, D. Sener, T. Baran, F. Ilkova: "A fatal complication due to radiofrequency ablation for atrial fibrillation: atrio-esophageal fistula", The Annals of Thoracic Surgery, vol. 76, pp. 281-283, 2003). At the beginning it was believed that these perforations were caused by the • simultaneous use of a transesophageal echocardiography probe, however, more recently such problems have appeared without the simultaneous use of said probe, and are mainly due to thermal conduction from the area of lesion (atrial wall) to the wall of the esophagus.

To minimize the risk of esophageal hyperthermal injury during intraoperative ablation,. different more or less feasible techniques have been proposed, such as the use of bipolar probes (AM Glllϊnov, PM McCarthy: "Bipolar atrial radiofrequency clamp for intraoperative ablation of atrial fibrillation", The Annals of Thoracic Surgery, vol. 74, pp. 2165 -2168, 2002) which prevent ^currents' RF pass through the esophagus and circumscribe the lesion tissue disposed between the two electrodes, or using specific surgical procedures (K. Khargi, A. Laczkovics, K. Müller, T. Deneke: "A possible surgical technique to avoid. esophageal and circumflex artery injuries using radiofrequency ablation to treat atrial fibrillation", Interactive Cardiovascular and Thoracic Surgery, vol. 3, pp. 352-355, 2004).

On the other hand, percutaneous ablation of the atrium has not only shown problems of damage to the esophagus (C. Pappone, H. Oral, V. Santinelli, Vicedomini G, CC Lang, F. Manguso, L. Torracca, S. Benussi, 0. Alfieri, R. Hong, W. Lau, K. Hirata, N. Shikuma, B. Hall, F. Morady: "Atrio-esophageal fistula as a complication of percutaneous transcatheter ablation of atrial fibrillation", Circulation, vol. 109 , pp. 2724-2726, 2004), but it is still a tedious and not so effective procedure. In addition, it presents a greater potential risk to the esophagus in that:

1) bipolar ablation is not possible, -

2) blood flow over the endocardium produces a greater degree of cooling on the surface of the lesion, which can lead to the displacement of the maximum temperature point towards the deeper tissue, and therefore, towards the esophagus.

Despite these increased risks, radiofrequency catheter ablation of atrial fibrillation is a major advantage over ^', ablation. It is a non-surgical procedure, and therefore it is expected that in the future ^' not too far away, new designs of electrodes and ablation catheters will improve this procedure by decreasing its duration and increasing its effectiveness. However, in Parallel to this research, new systems should be able to significantly minimize the risk of damage to the esophagus. The present invention proposes a system that allows thermal protection of the esophagus during intraoperative ablation, and especially during percutaneous ablation.

To date, some catheter-based systems and probes have been proposed for heat transfer in different body cavities, such as blood vessels (US-A-5624392), or in the esophagus (WO-A-99). / 05996, WO-A-03/105736). Specifically, the publication WO-A- 99/05996 deals with an oral insertion probe that is housed in the esophagus at the height of the aorta, and which allows maintaining body temperature during a cardiac surgery operation. It is based on circulating a fluid through the probe to achieve temperatures between 37 and 41 ⁰ C in the area of the esophagus. Therefore nothing contributes to the ^• respect of preserving the esophagus against possible overheating due to hyperthermal ablation of nearby tissues, but rather tries to achieve a degree of hypothermia that preserves the cardiac tissue during the ischemia phase of 'cardiac surgery . Publication WO-A-03/105736 deals with a catheter that allows topical cooling of body areas. However, since it is not designed for endocavitary structures, it cannot be inserted into the esophagus. Furthermore, while WO-A-03/105736 deals with a general topical cooling system for therapies, it makes no reference to the prevention of thermal damage caused by the proximity of ablated areas. US-B-6261312 is about an inflatable catheter for heating or cooling selected organs. _. However, the system. It is based on providing a change in the temperature in the blood that feeds that organ. It is therefore difficult ^'application to the case of the portion of the esophagus near the heart wall.

On the other hand, different devices based on inflatable balloon for the heating or cooling of certain organs have been proposed. Some ^'devices are raised _with. in order to create severe cooling injuries (cryosurgery) and are therefore not related to the present invention (see, for example, US-A-2004/147914 and US-A-2004/143249).

. On the other hand, US-B-6726708 is a system based on inflatable and cooled balloon to control the temperature of the colon or stomach. The same system can be used to monitor the temperature in the area of the esophagus, but there is no reference to the swelling of the cooling balloon in the area of the esophagus. US-A-2004/210281 presents an apparatus based on probes and inflatable balloons internally cooled and located in the esophagus, allow to cool the cardiac tissue. Said apparatus is oriented to create a mild hypothermia (32-35 ⁰ C) in said tissue and thus minimize metabolic expenditure after, for example, a myocardial infarction, or any case of hypoxia or ischemia in any other tissue. It is therefore not oriented at any time to thermally protect the esophagus against thermal elevations by adjacent ablations. The device is oriented to achieve hypothermia slowly (from decrements of 0.5 ° C / hour, until no more than 1 ° C / minute). Therefore, it would not be possible with this device to achieve a rapid evacuation of the heat generated in the wall of the esophagus during the no more than 120 seconds that an ablation lasts. . • Furthermore, said apparatus allows not only the cooling of the organ, adjacent to the cooled probe or balloon, but of other organs adjacent to it. Therefore, it would not be valid to thermally protect the esophagus during cardiac ablation, since during this procedure it is desired to thermally injure the cardiac wall.

That is, the apparatus described in US-A-2004/210281 is more oriented to slowly lower the temperature not only of an organ, but of other adjacent tissues, while the problem of protecting the esophagus during ablation should be based on evacuating rapidly. the heat created in the vicinity of the chilled ball or probe.

Finally, at http://www.uvminnovations.com/graphics/catheter.pdf, a patent application from the University of

Vermont (A. Abdul-Karim, D. Lustgaten, A. Maheshari, and P.

Spector: "Esophageal balloon cooling catheter") and it is briefly indicated that it is an inflatable balloon-based system that is positioned in the esophagus and internally cooled, allows thermal protection of the esophagus during atrial ablation, as well as monitoring e cardiac and esophageal image. The document that has been accessed does not include any detailed description of the system that allows to evaluate the efficacy and safety of said invention - in order to protect thermally the esophagus during an ablation of a nearby organ.

DESCRIPTION OF THE INVENTION A first aspect of the invention relates to an apparatus for thermal protection of the esophagus (or at least a part of the esophagus) of a patient, to avoid damage to the esophagus due to overheating in correspondence with an intervention of hyperthermal ablation in the vicinity of the esophagus. The apparatus comprises a flexible element configured to be inserted by the patient's mouth or nose, said flexible element comprising at least a part intended to be in contact with the esophagus, the flexible element comprising at least one circulation circuit of a configured cooling fluid for the circulation of a cooling fluid through the part intended to be in contact with the esophagus, in order to cool the corresponding part of the esophagus to avoid hyperthermia injuries. The flexible element has a portion configured to input and output device connected to a fluid pumping refrigerator, ^"so that said pumping device to pump fluid cooler cooler fluid through the circulation circuit.

In this way, the temperature of the esophagus (or the relevant part of the esophagus) can be maintained at a level that avoids hyperthermia damage during a hyperthermia ablation intervention in the area near the esophagus. In addition, the part intended to be in contact with the esophagus is provided with means for measuring parameters related to temperature in an area of contact with the esophagus. Thus, the temperature can be monitored during the operation and changing the temperature of the cooling fluid and / or the pumping rate based on the development of ^this' temperature.

For this, the device can be equipped with an electronic system (which can be external to the patient) configured to interpret data provided by the measurement means, of parameters related to temperature, and to modify the operation of the device based on said data .

The electronic system may be configured to modify the temperature of the cooling fluid and / or a pumping rate of the cooling fluid, depending on said data provided by the means of measuring parameters related to the temperature.

The temperature-related parameter measuring means may comprise a plurality of electrodes for measuring the electrical impedance of the tissue adjacent to the electrodes (that is, in the wall of the esophagus), and / or a plurality of temperature sensors for the measurement of the temperature reached in a plurality of points of the esophagus. The same electrodes may be configured to serve for recording electrograms associated with the attached cardiac tissue.

At least some of the electrodes and / or the temperature sensors may be distributed around the part intended to be in contact with the esophagus (ie, angularly distributed around the axis length of this part), to ensure that there is always at least one temperature sensor and / or electrode located close to the area corresponding to the atrial wall where the ablation occurs, regardless of the possible rotation of the flexible element that is introduced into the esophagus.

The flexible element may comprise a tubular probe, for example, of plastic. The tubular probe can fundamentally protect that portion of the perimeter of the esophagus that is in intimate contact with the probe.

The circulation circuit may comprise two concentric or coaxial ducts that are in communication at a distal end of the probe, so that through one of said ducts the cooling fluid can flow to said distal end and then return through the other of said ducts, so that the cooling fluid, when flowing through an external duct of said two concentric or coaxial ducts, can cool a part of the esophagus with which the tubular probe is in contact.

The probe may have a diameter greater than or equal to 4 mm and less than or equal to 15 mm in the part intended to be in contact with the esophagus.

The apparatus may also include the ^' pumping device, which may be a device configured to pump a precooled liquid fluid.

According to another embodiment of the invention, the flexible element can be a catheter and the part intended to be in contact with the esophagus can be an inflatable balloon that is part of said catheter, the circulation circuit being configured to make circulating the cooling fluid through said inflatable ball. The balloon, when swollen, can open the light of the esophagus, allowing the surface of the ball to come into intimate contact with the entire perimeter of the esophagus at the height of its position.

The inflatable balloon may have a circular cross section, for example.

The inflatable balloon may have a maximum diameter in a swollen state of greater than 10 mm and less than 20 mm, for example.

The ball may have a length greater than or equal to 5 cm and less than or equal to 15 cm, for example. In fact, the ball must be long enough to protect an extensive area of the esophagus. It should be borne in mind that thermal lesions created in the atrium during ablation for the suppression of atrial fibrillation follow in most cases a linear and extensive pattern. In this sense, it is interesting to have a thermal protection system that without repositioning the cooled balloon, allows almost all the necessary lesions in the atrium to be completed safely for the esophagus.

The apparatus may further comprise the pumping device, said pumping device being a pumping device for a precooled fluid. It can be a device configured to pump a precooled gas.

The apparatus according to any of the modalities described above may be configured for the circulation of a cooling fluid with a temperature greater than or equal to 10 ⁰ C and less than or equal to 30 ⁰ C. In the ^'same way as in the case of the probe configuration inflatable balloon you can have two channels for the transfer of fluid or gas cooled.

The apparatus may be configured for the circulation of the cooling fluid at a speed sufficient to maintain the part of the esophagus with which the flexible element is in contact, at a temperature sufficiently low to prevent damage to the esophagus in relation to an ablation intervention. for hyperthermia- in the area. It involves evacuating excess temperature from the wall of the esophagus. Both the temperature of the fluid or gas, and the speed of the same can be programmed by the user from the same pumping system. The optimum values can be programmed from the results suggested by the mathematical modeling or by the clinical experience based on the ^' records of thermal evolution obtained by means of temperature sensors located in the refrigerant system itself or in the ablation electrodes.

The flexible member may be provided with at least one mark the radiopaque to facilitate proper positioning of Ia the flexible element, in correspondence with the part of the esophagus to cool. In this way, the device can be placed in a guided manner with fluoroscopy image or similar. In addition, the flexible element (for example, the probe or catheter) may be provided with distance marks (for example, a ruler in centimeters or inches) to aid in its placement or repositioning; These marks may be present at least in an area that will be placed in correspondence with the insertion point (nose or - mouth) when the flexible element is placed in the • patient, in a position suitable for use.

The electronic system may be configured to modify the operation of an ablation generator in response to data indicative of a temperature rise above ^• a predetermined threshold (which may correspond to an absolute temperature or a temperature rise rate), supplied by means of measuring parameters related to temperature. This allows these means to be used to influence and even stop the ablation process, if necessary.

Another aspect of the invention relates to a method for preventing unwanted lesions in the esophagus of a patient during a hyperthermal ablation process of an organ close to the esophagus of a patient (for example, the atrial wall), which comprises the passage of , for at least a substantial part of the ablation process, cooling a selected part of the esophagus with a device according to what has been described above.

Another aspect of the invention relates to a method for preventing unwanted injury ^• in the esophagus of a patient during an ablation process hyperthermic organ near the esophagus of the patient, comprising the steps of:

1) placing a cooling device comprising a balloon or a probe in the esophageal light, before starting the ablation procedure, introducing said cooling device through the nostril or through the patient's mouth; 2) confirm a correct position of the cooling device in a neighboring area to the location of the organ to be ablated, by

- radiological guidance based on radio-opaque markings (for example, the balloon or probe may have two radio-opaque markings at its ends; in this case, a balloon with a length between 5 and 10 cm could be used to ensure with some margin the exact location) ; I

- electrocardiographic guidance (the balloon or probe can be placed by electrocardiographic guidance based on the unipolar recording of the signals associated with atrial depolarization; thanks to the difference in amplitude between the signal recorded by two electrodes at the ends of the balloon or probe, and the signal registered with electrodes in the center, the atrium can be located in its portion closest to the esophagus; in this case a 15 cm balloon could be used, to ensure with certain margin the exact location of the atrium); and / or intraoperative anatomical guidance (during cardiac surgery it is easy to palpate the retrocardial wall of the left atrium, as well as the esophagus; by surgical palpation the exact position of the balloon or probe can be known);

3) purge and fill the cooling device (i.e. the balloon or probe, - this can be done without internal circulation, with normothermic physiological soil - that is, with a temperature of approximately 36 ⁰ C-, in order to assess the tolerance when inflated by the patient - degree of discomfort, retrosternal pain, etc.); 4) initiate a circulation of a fluid through the cooling device, said fluid having a temperature greater than 30 ° C (for example, between 35 ° C and 37

° C);

May 5) initiating a flow of a fluid cooler device ^{'refrigerator,} said cooling fluid at a temperature greater than or equal to 10 ⁰ C and not exceeding 30 ⁰ C;

6) check the temperature of the relevant area

10 by means of temperature sensors and / or electrodes - configured to detect an impedance in said area, before and during the ablation process (by means of impedance detection and / or by temperature sensors; for example, an increase can be detected

15. Initial impedance and arrival at a constant impedance zone, which indicates that the programmed cooling temperature has been reached; in turn, it may be convenient to assess the clinical tolerance of esophageal hypothermia by the patient); 0 7) Once the ablation process is finished, perform a purge and complete extraction of the cooling fluid from the 'cooling device, and remove the cooling device (it is important to ensure that the balloon or probe is empty before extraction, in order to avoid injury due to tear of the esophagus).

Before step 3) and in the case of using a balloon, the size of the inflatable balloon must be selected, for example by one of the following criteria: a) the anatomical size of the organ to be ablated 0 (by some diagnostic imaging system, by example,. echocardiography, CT or cardiac magnetic resonance imaging); or b) the guidance method for esophageal implantation described above. After step 2) can optionally take note reading featuring an external rule (located on the body of the probe or catheter) exactly at the height of the insertion point (in mouth or nose) ^' ". • This This means that, in any of the steps between 3) and 7), and in case of unwanted displacement of the cooling device inside the esophagus, it will be possible to reposition it correctly and quickly thanks to the reading of the rule taken after step 2); After step 4) it may be convenient to recheck the location of the balloon or probe by means of radiological, unipolar electrocardiographic, or surgical intraoperative control, and confirm that the balloon or probe has not moved. steps 5 and 6 it may be advisable to check the rheological operation of the balloon or probe, and record the electrical impedances before cooling by means of ins electrodes ertados in

- the ball or probe. It is advisable to record the variations in temperature and impedance throughout the ablation. An excessive increase in temperature recorded by the sensors of the balloon or probe, or an excessive decrease in the impedance recorded by the electrodes would indicate poor esophageal protection. The method may comprise the step of, in response to a detection of a temperature rise in the relevant area, increasing a flow rate of the fluid through the cooling device, and / or lowering the temperature • of said fluid, and / or interrupt the ablation process.

During periods between radiofrequency energy (ablation) applications, the esophagus can be returned to its basal temperature, for example, according to one of two ways: a) by stopping cooling fluid circulating, thus achieving a progressive and spontaneous recovery of temperature; or, b) recirculating fluid at normothermic temperature (approximately 36 ⁰ C).

DESCRIPTION OF THE FIGURES

To complete the description and in order to aid a better understanding of the characteristics of the invention according to some examples of practical embodiments thereof, it ^'as an integral part of said description, a set of drawings where with Illustrative and non-limiting, the following has been represented:

Figure 1.- Schematic view of the catheter system and inflatable balloon positioned in the esophagus at the height of the left atrial wall.

Figure 2. - General schematic view of the catheter and inflatable balloon system.

Figure 3. - General schematic view of the system based on internally cooled plastic probe from circulating and precooled fluid. Figure 4.- Schematic view of the inflatable balloon with a possible electrode arrangement for recording electrograms and impedance measurements, and temperature sensors. Figure 5. - Schematic view of the inflatable balloon system positioned in the esophagus and its relationship with the other elements (coolant pumping system, ablation generator, electronic system for signal processing acquired by sensors and electrodes).

Figure 6.- Scheme of the possible evolution of the electrical impedance recorded by the electrodes of the balloon before and during an ablation of an adjacent organ. ^' Figure 7. Schematic view of the external ruler located on the body of the catheter or catheter at the level of the insertion point (oral or nasal).

PREFERRED EMBODIMENT OF THE INVENTION Figure 1 reflects a possible embodiment of the invention in which the apparatus for thermal protection of the esophagus includes a catheter _. 1 with a balloon 2 ^inflates' inside the esophagus 3 and the height of the ablation electrode 4 creating thermal injury 5 in the atrial wall 6. Also, as shown schematically in Figure 2, the balloon 2 is swollen and a gas or refrigerated fluid circulates inside it from a pumping device 7 through two conductors 13 (illustrated schematically in Figure 5). The balloon 2 can be of a high pressure type, of elongated spherical shape, with a fixed diameter ^• which prevents uncontrolled swelling and therefore damage to the wall of the esophagus. As a material it is possible to use PET or nylon. In the ball, the walls are thin enough to transfer heat well. from the walls of the esophagus to the inside of the ball. In addition, when the ball is inflated, the ball remains in intimate contact with the walls of the esophagus, partially forming the curves and irregularities of said walls and thus achieving a good degree of protection.

That is to say, the ball must be constructed of an external material that allows at the same time flexibility, formability, and a high degree of heat transfer. By last, . The ball can have electrical insulating characteristics, especially its outermost coating. The internal cooling of the balloon can be done by gas (nitrogen, for example) or by circulating liquid (saline, for example) similar to that of preheated balloons by circulating fluid for endometrial ablation of the uterus (WO-A -00/00100), or the ball proposed in US-A-2004/210281 to create a slight hypothermia in the esophagus. In another embodiment, as shown in Figure 3, instead of the balloon catheter is possible ^' to use a plastic tube 11 which in turn is internally cooled by a circulating fluid. Said fluid is driven by a pumping device 17 which in turn can maintain the temperature of the liquid at a preset value. The design of the probe with liquid Circulating can be based on two coaxial ducts joined at the distal end 12 similarly to that described in. Publication WO-A-99/05996. The probe could be made of polyurethane or silicone, have a variable external diameter (4-15 mm) and a total length between 20 and 25 cm. In addition, it should have a large enough internal diameter to house two coaxial ducts inside (ie, with fluid communication between both ducts) exclusively at the distal end of the probe. The coolant will circulate through said ducts, so that when flowing through the outer duct, it will serve to cool the inner wall of the esophagus. With this configuration, only the area of the esophagus in contact with or very close to the probe will be well protected. A difference to take into account when choosing between this configuration and the inflatable balloon catheter is that the action of inflating the balloon can reduce, in some cases, the distance between the wall of the esophagus and the wall of the earpiece, and can increase the possibility of thermal damage.

In this configuration, the proximal end of the probe could be connected to a pump that would allow liquid circulation. Said pump 17 could be of the conventional peristaltic type attached to a liquid reservoir (thermostatic bath) or a more elaborate system as proposed in US-A-2003/060864.

In addition, and in order to achieve good positioning of the probe or ball near the ablated cardiac wall, - both ^{configurations'} (plastic tube and inflatable balloon) have radiopaque markings 8.18 (figures 1 and 3 ) which together with radioscopy equipment makes it possible to determine the position of the device and its spatial relationship with other recording or ablation electrodes (also radiopaque).

Similarly, and in order to achieve a rapid and correct relocation of the probe or balloon in case of unwanted displacement of the same, both configurations

(probe and inflatable ball) have a ruler divided into centimeters, millimeters or inches (figure 7), and engraved on its exterior at the height of the insertion point (9 in figure 5). Likewise, the cooling elements (both the balloon 2 and the probe 11) can have metal electrodes 19 for recording the atrial or ventricular electrograms of the heart. The technique has been previously described (F. Prochaczek _r G. Jerzy, MJ Stopczyk: "A method of esophageal electrogram recording for diagnostic atrial and ventricular pacing" Pacing and Clinical Electrphysiology, vol. 13, pp. 1136-1141, 1990). Typically a total of 6 electrodes could be arranged (see Figure 4 illustrating the electrodes in correspondence with the inflatable balloon 2; a similar configuration could be used for the case of the probe 11). The four electrodes of center 19 will be arranged at the same height, but on all four sides of the ball (front, back, right and left). This is intended to always have a ventral electrode, in contact with the part of the atrial wall, and thus avoid that during the introduction of the balloon it could rotate in its longitudinal axis and be arranged in the dorsal part of the esophagus, away from the signal electrocardiographic atrium. This can be checked by observing the amplitude of the unipolar electrograms associated with each of these four electrodes. These unipolar electrograms are captured as the difference in electrical voltage between each of the four electrodes and a reference electrode located at a remote point (for example the one used for recording surface electrocardiogram). Bipolar electrograms could also be recorded (between two of these four electrodes). The two electrodes of the ends of the balloon (proximal and distal) can also serve as reference electrodes for said unipolar registers. These same electrodes 19 could also serve to monitor the unipolar or bipolar impedance of the adjacent tissue, that is, of the wall of the esophagus. The evolution of this impedance, which is closely related to the temperature of said tissue (WM Hartung, ME Burton, AG Deam, PF Walter, K. McTeague, JJ Lagnberg: "Estimation of temperature during radiofrequency catheter ablation using impedance measurements", Pacing and Clinical Electrophysiology, vol 18, pp. 2017-21, 1995) would allow to easily estimate the temperature of the wall of the esophagus and therefore assess in real time the effectiveness of thermal protection. Figure 6 shows a possible evolution of the impedance (Nomenclature: T _E (temperature in the wall of the esophagus), T _PA (temperature in the atrial wall, or in any organ subject to ablation), Z (electrical impedance measured between two electrodes of the balloon, or between one of the electrodes and a distant reference electrode.) During a phase A corresponding to the cooling of the balloon and prior to the application of radiofrequency energy in the ablation zone, the temperature of the adjacent tissue will gradually decrease, and due to the positive coefficient of the electrical conductivity of biological tissues (approximately +2 % / ° C), the impedance recorded from the electrodes of the balloon will increase asymptotically towards a constant value, corresponding to the moment of thermal equilibrium. Once the ablation begins (phase B in figure 6), the temperature of the esophagus will experience a rise due to the thermal energy that arrives from the ablated zone by conduction. This thermal increase will be reflected in a change in the trend of the said impedance, which will begin to decrease. An excessive decrease in the value of this impedance will correspond to an excessive increase in the temperature of the tissue adjacent to the electrodes, that is, of the wall of the esophagus, and consequently reflect poor protection. On the contrary, a decrease in impedance that is not significant, or even absent, will suggest good thermal protection of the tissue adjacent to the electrode, that is, of the esophagus.

As an alternative or complement to electrodes intended for electrogram recording and impedance measurement, the cooling elements (both the balloon and the probe) can have temperature sensors 20 on their surface in order to have a direct measure of quality of the cooling of the wall of the esophagus. The position of these sensors could be, for example, right next to each electrode or, in any case, preferably with a certain radial distribution that allows a temperature sensor to always be in the area near the atrial wall to be monitored, regardless of rotation of the flexible element on its longitudinal axis. Both the signals obtained from the electrodes 19, and the signals obtained from the temperature sensors 20, are physically supported by conductive cables 14 that are housed inside the catheter 1 or plastic probe 11. The information obtained from both the impedance measurement signals, and from the temperature sensors themselves, can be processed by an electronic system 15 of simple implementation that estimates the thermal evolution of the wall of the esophagus, and therefore therefore, it can automatically modify the operation of the ablation generator 10 (for example, the power managed by said generator), or even directly cause its disconnection in order to avoid damage to the esophagus. Likewise, it could also, by means of a control algorithm, automatically adjust the two programmable parameters of the pumping system 7, 17, namely the temperature of the cooling fluid and its circulation speed. Electrodes 19 for recording electrograms or for measuring impedance can be small in size.

(for example, 2 mm x 2 mm) and made of metallic material

(for example, of an alloy of platinum and iridium or stainless steel). The impedance measurement can be performed by injection of sinusoidal alternating current (20 kHz frequency, for example) and of low amplitude (1 mA, for example). For the impedance measurement, a pair of electrodes can be used through which the electric current is injected and received, and between which the voltage can be measured at the same time. These two electrodes can be, for example, one of the electrodes 19 positioned in the inflatable balloon, and a reference electrode away from the area. In general, the electrodes can be adhered to the wall of the balloon as described in US-A-5255678. The temperature sensors 20 may be small enough to be positioned on the surface of the balloon or probe itself, and be quick response. For example, K-type thermocouples bonded with epoxy resin to the inner wall of the balloon could be used (A. Rosen, P. Walinsky: "Microwave balloon angioplasty", in A. Rosen and H. Rosen "New Frontiers in Medical Device and Technology ", John Wiley & Sons, p. 33, 1995). As for the method to prevent unwanted lesions in the esophagus of a patient during a hyperthermal ablation process of an organ close to the esophagus, which may comprise the passage of, during at least a substantial part of the ablation process, cooling a selected part of the Esophagus with a device according to the invention, this method can be carried out, for example, according to the following steps:

* The balloon will be placed in the esophageal lumen before starting the atrial ablation procedure. For this, it will be introduced through the nostril or through the patient's mouth, with the help of active swallowing of the patient and without the need for general anesthesia. Only a topical anesthetic with local spray can be applied

(2% xylocaine) to eliminate discomfort (emesis, nausea) during its introduction.

* Before the esophageal local cooling it may be important to confirm the correct position of the balloon in the neighboring area to the location of the atrium, since the situation could be introduced to introduce the balloon into the bronchial tree, or in esophageal bordering areas not attached to the left atrium, in which case the objective will not be achieved.

* A selection of the size of the ball can be made using one of the following criteria: a) The anatomical size of the left atrium:

For this, it will be necessary to have a previous measurement, using some diagnostic imaging system, for example, echocardiography, CT or cardiac magnetic resonance. Echocardiography is the most available and simple, with four chambers measuring the superior inferior diameter of the atrium (distance between the mitral valve plane and the atrial roof) in its apical projection. This diameter offers the operator, with much approximation, the length of the atrium in contact with the esophagus. This distance will be the guideline when selecting the size of the ball, slightly larger to correct the inaccuracy of esophageal implantation. b) Using the guidance method for esophageal implantation (see options below).

* Guidance method for esophageal implantation. For the correct location of the ball three different forms can be used: a. Radiological guidance If a radiology room is available, as is the case during percutaneous electrophysiological studies, it is easy to locate the area of the esophagus to cool with the anatomical structures of the left atrium in mind. One time located with the electro-catheter the pulmonary veins of the left atrium, it is easy to delineate the position of the esophageal wall in continuity with the atrium

5 left. The ball has two radio-opaque marks at its ends (see 8 in figure 4), which allow to position the ball accurately. In this case, a ball with a length between 5 and 10 cm could be used to

10 ensure with certain margin the exact location of the atrium. b. Electrocardiographic guidance In case you do not have radio-scoop equipment, as is usually the case during surgery

15 cardiac, the balloon can be placed by electrocardiographic guidance based on the unipolar recording of the signals associated with atrial depolarization. This procedure would be similar to the

20 registry of esophageal ECG used clinically in the diagnosis of arrhythmias. To do this, during the process of introducing the ball, you must monitor-record continuously the

25 unipolar signal of the 6 ball electrodes

(see 19 in figure 4). Thanks to the difference in amplitude between the signal registered by the two electrodes at the ends of the ball and the signal registered with

30 the four of the center, the atrium can be located in its portion closest to the esophagus. In this case, a 15 cm ball, to ensure with certain margin the exact location of the atrium, c. Intraoperative anatomical guidance. During cardiac surgery it is easy to palpate the retrocardial wall of the left atrium, as well as the esophagus. With the anesthetized and intubated patient, it is easy to place the balloon, just as other probes such as intraoperative transesophageal echocardiography are placed. By surgical palpation you can know the exact position of the balloon before proceeding to its inflation. In this case, a 10 cm balloon could be used to ensure with certain margin the exact location of the atrium.

* Once the ball is placed in the esophagus, the esophageal protection method will be started up in the order established in the following protocol:

Purge and fill the balloon, although without internal circulation, with normal thermal physiological soil (36 ⁰ C). In this way the tolerance to inflation can be assessed by the patient (degree of discomfort, retrosternal pain, etc).

- Check the location of the balloon by means of radiological, unipolar electrocardiographic, or surgical intraoperative control. Confirm intraesophageal non-displacement of the balloon.

Start the internal circulation of the normo thermal physiological serum. Check the correct rheological operation of the balloon, and record the electrical impedances before cooling Start the internal circulation of the hypothermic physiological serum (programmable between 10 and 30

⁰ C). Record the variations of the electrical impedances until reaching the plateau phase, at the programmed temperature (see phase A in figure 6).

. In turn, assess the clinical tolerance of esophageal hypothermia by the patient.

Confirm the desired esophageal temperature using the temperature sensors and / or the electrical impedance.

- Start ablation of the atrial wall (or any other organ or tissue adjacent to the esophagus). Optionally, variations in the temperature and / or impedance of the central electrodes can be recorded along the ablation (see phase B in figure 6).

- During the ablation it may not be necessary to maintain the circulation of liquid, in order to avoid a hypothermic lesion of the esophagus. During periods between ablation applications, the esophagus can be returned to its basal temperature, in two ways: a) ceasing to circulate liquid, thus achieving a progressive and spontaneous recovery of temperature (this is probably the most natural and physiological form) ; or b) recirculating with liquid at normothermic temperature (36 ⁰ C). This is probably a more damaging way because thermal gradients of very rapid evolution are created. - Once the ablation is finished, the ball will be removed by simple traction, after purging and complete extraction of its liquid or gas. It is important to ensure that the balloon is empty before removal in order to avoid injury due to tearing of the esophagus.

In this text, the word "comprises" and its variants (such as "understanding", etc.) should not be construed as excluding, that is, they do not exclude the possibility that what is described includes other elements, steps, etc.

On the other hand, the invention is not limited to the specific embodiments that have been described but also covers, for example, the variants that can be made by the average person skilled in the art (for example, in terms of the choice of materials, dimensions , components, configuration, etc.), within what follows from the claims.

Claims

1.- Apparatus for thermal protection of the esophagus of a patient, to avoid damage to the esophagus due to overheating in correspondence with an intervention of hyperthermal ablation in the vicinity of the esophagus, characterized in that the apparatus comprises: a flexible element (1, 11) configured to be inserted by the patient's mouth or nose, said flexible element comprising at least one part intended to be in contact with the esophagus, the flexible element comprising at least one circulation circuit of a cooling fluid configured for the circulation of the cooling fluid through the part destined to be in contact with the esophagus; the flexible element having an inlet and outlet part configured to be connected to a cooling fluid pumping device (7, 17), so that said cooling fluid pumping device can pump the cooling fluid through the circulation circuit; said part being intended to be in contact with the esophagus provided with means (19, 20) for measuring parameters related to the temperature of the wall of the esophagus.

2. Apparatus according to claim 1, characterized in that the flexible element comprises a tubular probe (11) -

3. Apparatus according to claim 2, characterized in that said tubular probe is made of plastic.

4. - Apparatus according to any of claims 2 and 3, characterized in that the circulation circuit comprises two concentric ducts that are in communication at a distal end (12), so that through one of said ducts the cooling fluid can flow to said distal end and then return through the other of said ducts, so that the cooling fluid, when flowing through an outer duct of said two concentric ducts, can cool a part of the esophagus with which the tubular probe is in contact.

5. Apparatus according to any of claims 2-4, characterized in that the tubular probe (11) has a diameter greater than or equal to 4 mm and less than or equal to 15 mm in the part intended to be in contact with the esophagus.

6. Apparatus according to any of claims 2-5, characterized in that it further comprises the pumping device (17), said device being a device configured to pump a precooled liquid fluid.

7. Apparatus according to claim 1, characterized in that the flexible element is a catheter (1) and that the part intended to be in contact with the esophagus is an inflatable balloon (2) that is part of said catheter, the circuit being circulation configured to circulate the cooling fluid through said inflatable balloon.

8. Apparatus according to claim 7, characterized in that the inflatable balloon (2) has a circular cross-section.

9. - Apparatus according to any of claims 7 and 8, characterized in that the inflatable balloon has a maximum diameter in a swollen state of more than 10 mm and less than 20 mm.

10. Apparatus according to any of claims 7-9, characterized in that the ball has a length greater than or equal to 5 ctn and less than or equal to 15 cm.

11. Apparatus according to any of claims 7-

10, characterized in that it further comprises the pumping device (7), said pumping device being a pumping device for a precooled fluid.

12. - Apparatus according to claim 11, characterized in that said pumping device is a pumping device configured to pump a precooled gas.

13. - Apparatus according to any of the preceding claims, characterized in that it is configured for the circulation of a cooling fluid with a temperature greater than or equal to 10 ° C and less than or equal to 30 ° C.

14. - Apparatus according to any of the preceding claims, configured for the circulation of the cooling fluid at a speed sufficient to maintain the part of the esophagus with which the device is in contact at a temperature low enough to prevent damage to the esophagus during a hyperthermia ablation intervention in an area near the esophagus.

15. - Apparatus according to any of the preceding claims, characterized in that the flexible element is provided with at least one radiopaque mark (8, 18), to facilitate the correct placement of the flexible element in correspondence with the part of the esophagus to be cooled.

16. Apparatus according to any of the preceding claims, characterized in that it is provided with an electronic system (15) configured to interpret data provided by the means (19, 20) for measuring parameters related to temperature, and to modify the operation of the apparatus based on such data.

17. Apparatus according to claim 16, characterized in that said electronic system (15) is configured to modify the temperature of the refrigerant fluid and / or the pumping rate of the refrigerant fluid, based on said data provided by the parameter measuring means temperature related.

18. Apparatus according to any of the preceding claims, characterized in that the means for measuring parameters related to temperature comprise a plurality of electrodes (19), for measuring the electrical impedance of a tissue adjacent to the electrodes.

19. Apparatus according to claim 18, characterized in that at least some of the electrodes (19) are distributed around the part intended to be in contact with the esophagus, to ensure that there is always at least one electrode located near the corresponding zone to the atrial wall.

20. Apparatus according to claim 18 or 19, characterized in that the electrodes (19) are configured to also allow the registration of bipolar and unipolar electrograms generated in the cardiac tissue.

21. Apparatus according to any of the preceding claims, characterized in that the means for measuring parameters related to temperature comprise a plurality of temperature sensors (20) for measuring the temperature reached at a plurality of points of the esophagus.

22. Apparatus according to claim 21, characterized in that at least some of the temperature sensors (20) are distributed around the part intended to be in contact with the esophagus, to ensure that there is always at least one temperature sensor located nearby to the area corresponding to the atrial wall.

23. Apparatus according to any of claims 16 and 17, characterized in that the electronic system (15) is configured to modify the operation of an ablation generator (10) in response to data indicative of a temperature rise above a threshold predetermined, supplied by means (19, 20) for measuring parameters related to temperature.

24. - Apparatus according to any of the preceding claims, characterized in that the flexible element is provided with distance marks to assist in its placement or repositioning, said marks being present at least in an area that will correspond to an insertion point in the patient when The flexible element is placed in a position of use of the apparatus.

25.- Method to prevent unwanted lesions in the esophagus of a patient during a hyperthermal ablation process of an organ close to the patient's esophagus, characterized in that it comprises the passage of, during at least a substantial part of the ablation process, cooling a part selected from the esophagus with an apparatus according to any one of the preceding claims.

26.- Method to prevent unwanted lesions in the esophagus of a patient during a hyperthermal ablation process of an organ close to the esophagus of a patient, comprising the steps of: 1) placing a cooling device comprising a balloon or a probe in esophageal light, before starting the ablation procedure, introducing said cooling device through the nostril or through the patient's mouth;

2) confirm a correct position of the cooling device in the neighboring area to the location of the organ to be ablated, by

- radiological guidance based on radiopaque marks; I

- electrocardiographic guidance; and / or - intraoperative anatomical guidance;

3) purge and fill the cooling device;

4) initiating a flow of fluid through the device 'refrigerator, said fluid having a temperature above 30 ⁰ C; 5) initiate a circulation of a cooling fluid through the cooling device, said cooling fluid having a temperature greater than or equal to 10 ⁰ C and less than or equal to 30 ⁰ C);

6) check the temperature of the relevant zone by means of temperature sensors and / or electrodes configured to detect an electrical impedance in said zone, before and during the ablation process;

7) Once the ablation process is finished, purge and completely remove the cooling fluid from the cooling device, and remove the cooling device.

27.- Method according to claim 26, characterized in that after step 2), a reading is taken that offers a ruler located outside the element flexible, at the height of an insertion point (9) in the patient.

28.- Method according to any of claims 26 and 27, characterized in that it comprises the step of, in response to a detection of a temperature rise in the relevant area, increasing the flow rate of the fluid through the cooling device, and / or lower the temperature of said fluid, and / or interrupt the ablation process.