ES2267396A1 - Apparatus and method for the thermal protection of the oesophagus - Google Patents

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 for thermal protection of the esophagus, and use of the device for thermal protection of the esophagus.

Technical Field of the Invention

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

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. Desjardins, I. Case, J. Han, E. Good, K Tamirisa, A. Tsemo, A. Chugh, Bogun F, 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 ablation ", 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, O. Gil, R. García, F. Atienza, R. Paya, JL Pérez, A. Quesada, S. Canovas, MJ Dalmau, M. Bueno : " Surgery ablation of bypass fibrillation with epicardial and endocardial biauricular radiofrequency: initial experience ", Revista Española de Cardiología, vol. 55, pp. 235-244, 2002 ). These thermal injuries are being done by 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 injury (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 Gillinov, PM McCarthy : " Bipolar atrial radiofrequency clamp for intraoperative ablation of atrial fibrillation ", The Annals of Thoracic Surgery, vol. 74, pp. 2165-2168, 2002 ) that prevent radiofrequency currents from crossing the esophagus and circumscribe the lesion to the tissue between the two electrodes, or the use of specific surgical procedures ( K. Khargi, A. Laczkovics, K. Muller, 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, O. Alfieri, R. Hong, W. Lau, K. Hirata, N. Shikuma, B. Hall, F. Morady : " Atrium-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 today. 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 injury, which may result in the displacement of the point of maximum temperature towards the deepest tissue, and therefore, To the esophagus.

Despite these greater risks, ablation percutaneous radiofrequency atrial fibrillation It represents a great advantage over intraoperative ablation: It is a non-surgical procedure, and therefore it is expect that in the not too distant future, new designs of electrodes and ablation catheters allow to improve said procedure decreasing its duration and increasing its effectiveness. However, in parallel to this research, new systems they 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 ablation intraoperatively, and especially during ablation percutaneous

To date, some systems based on catheters and probes have been proposed for the transfer of heat in different body cavities, such as in 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 tube that lodges in the esophagus at height of the aorta, and that allows to maintain body temperature during a cardiac surgery operation. It is based on circulating a fluid through the probe to achieve temperatures between 37 and 41 ° C in the area of the esophagus. Therefore nothing brings about it of preserving the esophagus against possible overheating due to hyperthermal ablation of nearby tissues, but more well try to achieve a degree of hypothermia that preserves the tissue Cardiac during the ischemia phase of cardiac surgery. The publication WO-A-03/105736 deals on a catheter that allows topical cooling of areas bodily However, not being designed for structures endocavitary, can not be inserted into the esophagus. Further, while WO-A-03/105736 is about a general topical cooling system for therapies, does not no reference to the prevention of thermal damage caused by the proximity of ablated areas.

US-B-6261312 treats on an inflatable catheter to heat or cool organs selected. However, the system is based on providing a change in the temperature in the blood that feeds that organ. It is therefore difficult to apply to the case of the portion of the esophagus near the heart wall.

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

On the other hand, US-B-6726708 deals with a system based on inflatable balloon and refrigerated 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 inflation of the cooling balloon in the area of the esophagus

US-A-2004/210281 presents an apparatus based on probes and inflatable balls internally cooled and located in the esophagus, allow Refrigerate heart tissue. Said apparatus is oriented to create a mild hypothermia (32-35ºC) in said tissue and thus minimizing metabolic expenditure after, for example, a heart attack myocardium, or any case of hypoxia or ischemia in any other tissue. It is therefore not oriented at any time to protect thermally the esophagus against thermal elevations by adjacent ablations. The device is oriented to achieve slowly hypothermia (from 0.5ºC / hour decrements, to no more than 1ºC / minute). Therefore, it would not be possible with this device achieve rapid evacuation of heat generated in the wall of the esophagus for no more than 120 seconds that lasts a ablation.

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 an ablation cardiac, since during this procedure, you want to injure thermally 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 an ablation should be based on rapid evacuation the heat created in the vicinity of the ball or probe refrigerated

Finally, at http://www.uvminnovations.com/graphics/catheter.pdf, a patent application from the University of Vermont is mentioned ( A. Abdul-Karim, D. Lustgaten, A. Maheshari, and P. Spector : " Esophageal balloon cooling catheter ") and briefly indicates 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 and imaging Cardiac and esophageal. 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 thermally protect 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 a hyperthermal ablation intervention in the vicinity of the esophagus. The apparatus comprises a flexible element configured to be inserted through the patient's mouth or nose, said said flexible element at least one part intended to be placed in contact with the esophagus, the flexible element comprising the minus a circulation circuit of a cooling fluid configured for the circulation of a cooling fluid through of the part intended to be in contact with the esophagus, with the in order to cool the corresponding part of the esophagus to avoid hyperthermia lesions The flexible element has a part of input and output configured to connect to a device pumping of cooling fluid, so that said device pumping of cooling fluid can pump the cooling fluid through the circulation circuit.

In this way, the temperature can be maintained of the esophagus (or the relevant part of the esophagus) at a level that allow to avoid damage due to hyperthermia during an intervention of hyperthermia ablation in the area near the esophagus.

In addition, the part intended to be placed in contact with the esophagus is equipped with measuring means of temperature related parameters in a contact zone With the esophagus. In this way, the temperature can be monitored during the intervention and modify the fluid temperature refrigerator and / or pumping speed depending on the development of said temperature

For this, the apparatus may be provided with a 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 can be configured to modify the temperature of the cooling fluid and / or a pumping rate of the cooling fluid, depending on these data provided by the parameter measuring means temperature related.

The means of measuring parameters related to temperature may comprise a plurality of  electrodes for measuring the electrical impedance of the tissue next to the electrodes (that is, in the wall of the esophagus), and / or a plurality of temperature sensors for measuring the temperature reached at a plurality of points of the esophagus. The same electrodes may be configured to serve the electrogram recording 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 (i.e. distributed angularly around the longitudinal axis of this part), to ensure that there is always at least one sensor temperature and / or electrode located near the corresponding zone to the atrial wall where ablation occurs, regardless of the eventual rotation of the flexible element It enters the esophagus.

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

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

The probe may have a larger diameter or equal to 4 mm and less than or equal to 15 mm in the part intended for get in touch with the esophagus.

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

According to another embodiment of the invention, the flexible element may be a catheter and the part intended for getting in touch with the esophagus can be an inflatable balloon which is part of said catheter, the circuit being circulation configured to circulate the cooling fluid for said inflatable ball. The balloon, when swollen, can open the light of the esophagus, allowing the surface of the balloon to enter intimate contact with the entire perimeter of the esophagus at the height of your position.

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

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

The ball may have a longer length 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 Keep in mind that thermal injuries created in the atrium during ablation for suppression of the atrial fibrillation most often follow a pattern linear and extensive. In this sense, it is interesting to have a system thermal protection without repositioning the ball refrigerated, allow almost all injuries to be completed Necessary in the atrium safely for the esophagus.

The apparatus may also comprise the pumping device, said pumping device being a precooled fluid pumping device. You can try a device configured to pump a precooled gas.

The device 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 ° C and less than or equal to 30 ° C.

In the same way as in the case of the probe, the inflatable balloon configuration can have two ducts for the cooled fluid or gas transfer.

The device may be configured for circulation of the cooling fluid at a speed sufficient to  keep the part of the esophagus with which the flexible element, at a temperature low enough to avoid damage to the esophagus in relation to an intervention of hyperthermia ablation in the area. It's about evacuating the excess of temperature of the wall of the esophagus. Both the temperature of fluid or gas, as the speed of it can be programmed by the user from the same pumping system. The values optimal can be programmed from the results suggested by mathematical modeling or clinical experience based on thermal evolution records obtained by means of sensors temperature located in the cooling system itself or in the ablation electrodes

The flexible element can be provided with minus a radio-opaque mark, to facilitate the correct placement of the flexible element in correspondence with the part of the esophagus to cool. In this way, it can be done the placement of the device in a guided way with the image of fluoroscopy or similar.

In addition, the flexible element (for example, the probe or catheter) may be provided with distance marks (for example of a ruler in centimeters or inches) to help in your placement or relocation; these brands may be present at less in an area that will be in correspondence with the point of insertion (nose or mouth) when the flexible element is placed in the patient, in a position suitable for use.

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

Another aspect of the invention relates to the use of the device to prevent unwanted injuries in the esophagus of a patient during a hyperthermal ablation process of an organ near the esophagus of a patient (for example, the atrial wall), comprising the passage of, for at least one substantial part of the ablation process, cool a part selected from the esophagus with an apparatus according to what has been described above.

Another aspect of the invention (not claimed, but described to give more information about the applicability of the invention) refers to a method for preventing injuries unwanted in a patient's esophagus during a process of hyperthermal ablation of an organ near the patient's esophagus, which includes the steps of:

1) place a cooling device that comprises a balloon or a probe in the esophageal light, before initiate 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 ablate, by

-

guided radiological based on radiopaque marks (by For example, the ball or probe may have two marks radiopaque at its ends; in this case it could a ball of length between 5 and 10 cm is used, to ensure with certain margin the exact location); I

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guided electrocardiographic (the balloon or probe can be placed through a electrocardiographic guidance based on the unipolar record 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 ball or probe, and the signal recorded with electrodes in the center, the atrium can be located in its portion closer to the esophagus; in this case a balloon could be used 15 cm, to ensure with certain margin the exact location of the atrium); I

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guided Intraoperative anatomical (during cardiac surgery it is easy palpate the retrocardial wall of the left atrium, as well as the esophagus; by surgical palpation you can know the exact position of the balloon or probe);

3) purge and fill the cooling device (i.e. the ball or probe; this can be done without internal circulation, with normothermic physiological soil - that is, with a temperature of approximately 36ºC-, in order to assess patient tolerance to inflation - 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);

5) start a fluid circulation refrigerator by the cooling device, said fluid having refrigerator a temperature greater than or equal to 10 ° C and below or equal to 30 ° C;

6) check the temperature of the relevant area  by means of temperature sensors and / or electrodes configured to detect an impedance in said area, before and during the process ablation (by impedance detection and / or by thermometers; you can, for example, detect a initial increase in impedance and arrival in an area of constant impedance, which indicates that the programmed cooling temperature; in turn, it can be convenient to assess the clinical tolerance of hypothermia esophageal by the patient);

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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 make sure you have the empty balloon or probe before the extraction, in order to avoid injuries by tearing the esophagus).

Before step 3) and in the case of using a ball, you must select the size of the inflatable ball, by example using one of the following criteria:

a) the anatomical size of the organ to be ablated (by some diagnostic imaging system, for example, the echocardiography, CT scan or cardiac magnetic resonance imaging); or

b) the guidance method for implementation esophageal described above.

After step 2) you can optionally take reading note offered by an external rule (located on the probe or catheter body) exactly at the point of insertion (in mouth or nose). This way you get that, in any of the steps between 3) and 7), and in case of displacement unwanted cooling device inside the esophagus, it will be possible to reposition it correctly and  fast thanks to the reading of the rule taken after the step 2).

After step 4) it may be convenient to return to check the location of the ball or probe using the control radiological, unipolar electrocardiographic, or intraoperative surgical, and confirm that the balloon or probe has not been displaced.

Between steps 5 and 6 it may be advisable check the correct rheological functioning of the  balloon or probe, and record electrical impedances before cooling by electrodes inserted in the balloon or probe.

It is advisable to record the variations of temperature and impedance throughout the ablation. An excessive temperature increase recorded by balloon sensors or probe, or an excessive decrease in the recorded impedance by means of the electrodes it would indicate a bad protection esophageal

The method may comprise the step of, as response to a detection of a temperature rise in the area relevant, increase a fluid flow rate through the cooling device, and / or lower the temperature of said fluid, and / or interrupt the ablation process.

During periods between applications of radiofrequency energy (ablation), the esophagus may return at its basal temperature, for example, according to one of these two ways:

a) stop circulating refrigerator fluid, thus achieving a progressive and spontaneous recovery of the temperature; or

b) recirculating fluid at temperature normothermal (approximately 36 ° C).

Description of the figures

To complement the description and in order to  help a better understanding of the characteristics of the invention, according to some examples of practical embodiments of it, is accompanied as an integral part of said description, a set of figures in which with illustrative character and not limiting, the following has been represented:

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

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

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 ball  with a possible electrode arrangement for recording electrograms and impedance measurement, and sensors temperature.

Figure 5.- Schematic view of the system inflatable balloon positioned in the esophagus and its relationship with the other elements (refrigerant pumping system, generator ablation, electronic signal processing system acquired by sensors and electrodes).

Figure 6.- Scheme of the possible evolution of the  electrical impedance recorded by ball electrodes previously and during an ablation of an adjacent organ.

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Figure 7. Schematic view of the external rule located on the body of the catheter or catheter at the height 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 that inflates in the inside the esophagus 3 at the height of the ablation electrode 4 which creates a thermal lesion 5 in the atrial wall 6. Also, such as schematically shown in figure 2, said balloon 2 is swollen and a gas or refrigerated fluid circulates inside it to from a pumping device 7 through two conductors 13 (illustrated schematically in Figure 5).

The balloon 2 can be of high pressure type, of elongated spherical shape, with a fixed diameter that prevents a uncontrolled swelling and therefore damage to the wall of the esophagus. As a material it is possible to use PET or nylon. On the ball, the walls are thin enough to transfer the heat from the walls of the esophagus into the ball. Also, when the ball is inflated, the ball remains 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, the ball must be constructed of a external material that allows flexibility at the same time, conformability, and a high degree of heat transfer. By Finally, the ball can have insulating characteristics electric, especially its outermost coating. The internal cooling of the balloon can be done by gas (nitrogen, for example) or by circulating liquid (serum saline, for example) similar to that of the balls preheated by circulating fluid for ablation endometrial of the uterus (WO-A-00/00100), or the ball proposed in US-A-2004/210281 for create a slight hypothermia in the esophagus.

In another configuration, as shown in the Figure 3, instead of catheter with balloon it is possible to use a plastic probe 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 probe design with circulating liquid can be based on two coaxial ducts attached at the distal end 12 similarly to that described in the Publication WO-A-99/05996. Probe It could be made of polyurethane or silicone, have a diameter external variable (4-15 mm) and a total length between 20 and 25 cm. In addition, it should have an internal diameter large enough to house two ducts inside united coaxials (i.e. with fluid communication between the two ducts) exclusively at the distal end of the probe. By said ducts would circulate the coolant, so that when flowing through the external duct would serve to cool the wall Internal esophagus. With this configuration, only the area of the esophagus in contact with or very close to the probe would be fine protected. A difference to consider when choosing between this configuration and that of an inflatable balloon catheter is that the Inflating the ball can reduce, in some cases, the distance between the wall of the esophagus and the earpiece wall, being able to increase the possibility of thermal damage.

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

In addition, and in order to achieve a good positioning of the probe or balloon in the vicinity of the wall cardiac ablation object, both configurations (plastic probe and inflatable balloon) have radiopaque marks 8.18 (Figures 1 and 3) which together with radioscopy equipment makes possible 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 fast and correct repositioning of the probe or balloon in case of unwanted displacement of the same, both configurations (probe and inflatable balloon) have a ruler divided in centimeters, millimeters or inches (figure 7), and engraved on the outside of 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, 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. Such 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.

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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 tissue temperature contiguous will decrease gradually, and due to the positive coefficient of the electrical conductivity of biological tissues (approximately + 2% / ºC), 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 by conduction I arrived from the ablated area. 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 the electrodes intended for recording electrograms and for measuring impedance, the cooling elements (both the ball and the probe) may have temperature sensors 20 in their surface in order to have a direct measure of the cooling quality of the wall of the esophagus. The position of these sensors could be for example, right next to each electrode or, anyway, preferably with a certain radial distribution that allows a sensor to always be temperature in the area near the atrial wall to be monitored, regardless of the rotation of the flexible element on its axis longitudinal. Both the signals obtained from electrodes 19, and The signals obtained from the temperature sensors 20 are physically supported by conductive cables 14 that are housed in the inside of catheter 1 or plastic probe 11. The information obtained from both the impedance measurement signals, and from the own temperature sensors, can be processed by a system  electronic 15 of simple implementation that estimates the evolution thermal wall of the esophagus, and therefore, can modify automatically the operation of the ablation generator 10 (for for example, the power managed by said generator), or even directly cause its disconnection in order to avoid damage to the esophagus Also, it could also by an algorithm of control, automatically adjust the two programmable parameters of  pumping system 7, 17, namely the fluid temperature refrigerator and its circulation speed.

Electrodes 19 for recording electrograms or for impedance measurement can be small size (for example, 2 mm x 2 mm) and made of metallic material (for example, of an alloy of platinum and iridium or steel stainless). The impedance measurement can be performed by Injection of sinusoidal alternating current (20 kHz frequency, per example) and of low amplitude (1 mA, for example). For the measurement of impedance a pair of electrodes can be used by which the electric current is injected and received, and among which You can measure the voltage at the same time. These two electrodes can be, for example, one of the electrodes 19 positioned in the balloon inflatable, and a reference electrode away from the area. In In general, the electrodes can be attached 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 ).

Regarding the method to prevent injuries unwanted in a patient's esophagus during a process of hyperthermal ablation of an organ near the esophagus, which can understand the step of, for at least a substantial part of the Ablation process, cool a selected part of the esophagus with a device according to the invention, this method can be brought to perform, for example, according to the following steps:

* The ball will be placed in the esophageal light before of starting the atrial ablation procedure. This 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 one topical anesthetic can be applied with local spray (2% xylocaine) to eliminate discomfort (emesis,  nausea) during its introduction.

* Before esophageal local cooling can be important to confirm the correct position of the ball in the area next to the location of the atrium, as it could occur situation of introducing the ball in the bronchial tree, or in areas esophageal boundary not attached to the left atrium, in whose In case the objective would not be achieved.

* A selection of the size of the ball can be perform using any of the following criteria:

to)

He Anatomical size of the left atrium: This will require have a previous measurement, using some system diagnostic imaging, for example, echocardiography, CT scan or cardiac magnetic resonance Echocardiography is the most available and simple, being measured in its apical projection four chambers the superior inferior diameter of the atrium (distance between the mitral valve plane and the atrial roof). This diameter offers the operator, with much approximation, the length of the atrium in contact with the esophagus. This distance will be the one Guides when selecting the size of the ball, slightly higher to correct implantation inaccuracy esophageal

b)

Using the guidance method for esophageal implantation (see options below).

* Guidance method for implantation esophageal For the correct location of the ball can be used Three different ways:

to.

Radiological guidance If available radiology room, as is the case during the studies percutaneous electrophysiological, it is easy to locate the area of the esophagus to cool keeping in mind the anatomical structures of The left atrium. Once located with the electro-catheter the pulmonary veins of the atrium left, it is easy to define the position of the esophageal wall in continuity with the left atrium. The ball has two radio-opaque marks at their ends (see 8 in Figure 4), which allow you to position the ball exactly. In this In this case, a balloon with a length between 5 and 10 cm could be used to ensure with certain margin the exact location of the atrium.

b.

Electrocardiographic guidance In case of not having radio-scoop equipment, as usual be the case during cardiac surgery, the balloon can be placed by electrocardiographic guidance based on the record unipolar signals associated with atrial depolarization. This procedure would be similar to the esophageal ECG registry used clinically in the diagnosis of arrhythmias. For This, during the process of introducing the ball, must be continuously monitor-record the signal unipolar of the 6 electrodes of the balloon (see 19 in figure 4). Thanks to the difference in amplitude between the signal recorded by the two electrodes at the ends of the ball and the recorded signal with the four in 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 patient anesthetized and intubated it is easy to place the ball, in the same way that other probes such as transesophageal echocardiography are placed intraoperative By surgical palpation you can know the exact position of the ball before proceeding to its inflation. In this case a 10 cm ball could be used, to ensure with certain margin the exact location of the atrium.

* Once the ball is located in the esophagus it proceed to the implementation of the esophageal protection method according to the order established in the following protocol:

-

Purge and fill the ball, although without internal circulation, with soil physiological thermal normo (36ºC). In this way you can assess the  patient inflation tolerance (degree of discomfort, retrosternal pain, etc).

-

Check the location of the ball by radiological control, unipolar electrocardiographic, or intraoperative surgical. Confirm no displacement intraesophageal balloon.

-

Start the internal circulation of the serum  physiological thermal normo. Check the correct operation rheology of the ball, and record the electrical impedances before of cooling

-

Start the internal circulation of the serum  physiological hypothermic (programmable between 10 and 30ºC). to register the variations of the electrical impedances until reaching the phase of plateau, at the programmed temperature (see phase A in figure 6).

-

 To its instead, assess the clinical tolerance of esophageal hypothermia by part of the patient.

-

Confirm esophageal temperature desired by temperature sensors and / or impedance electric

-

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

-

During the ablation it might not be it is necessary to maintain the circulation of liquid, in order to avoid a hypothermic esophageal lesion. During periods between ablation applications, the esophagus can be returned to your basal temperature, in two ways:

to)

stop circulating liquid, achieving thus a progressive and spontaneous temperature recovery (This is probably the most natural and physiological way); or

b)

recirculating with liquid at temperature normothermic (36ºC). This is probably a more harmful way. because thermal gradients of evolution are created very fast

-

After the ablation, the ball will be removed by simple traction, after purging and extraction Complete of your liquid or gas. It is important to make sure you have the empty balloon before extraction in order to avoid injuries by tear of the esophagus.

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

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

Claims (24)

1. Apparatus for thermal protection of the esophagus of a patient, to avoid damage to the esophagus by overheating in correspondence with a hyperthermal ablation intervention in the vicinity of the esophagus, characterized in that the apparatus comprises: a flexible element (1, 11) configured to be inserted through the patient's mouth or nose, understanding said flexible element at least one part intended to be placed in contact with the esophagus, the flexible element comprising the minus a circulation circuit of a cooling fluid configured for the circulation of the cooling fluid through the part intended to be in contact with the esophagus; the flexible element having a part of input and output configured to connect to a device pumping (7, 17) of cooling fluid, so that said refrigerator fluid pumping device can pump the cooling fluid through the circulation circuit; said part being destined to be located in contact with the esophagus equipped with means (19, 20) for measuring parameters related to the wall temperature 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), such that through one of said ducts the cooling fluid can flow to said end distal to 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 circulation circuit being 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 balloon has a length greater than or equal to 5 cm 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, 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. 15. 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. 16. 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 means of measuring related parameters With the temperature. 17. 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. 18. Apparatus according to claim 17, 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 close to the area corresponding to the atrial wall 19. Apparatus according to claim 17 or 18, characterized in that the electrodes (19) are configured to also allow the registration of bipolar and unipolar electrograms generated in the cardiac tissue. 20. 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. 21. Apparatus according to claim 20, 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 close to the area corresponding to the atrial wall. 22. Apparatus according to any of claims 15 and 16, 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 predetermined threshold , supplied by means (19, 20) for measuring parameters related to temperature. 23. 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 corresponding to an insertion point in the patient when the flexible element is placed in a position of use of the apparatus. 24. Use of the apparatus according to any of the preceding claims 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 at least a substantial part of the Ablation process, cooling a selected part of the esophagus with said apparatus.