Breathing control during cardiac ablation

Abstract

The invention is entitled "Breath control during cardiac ablation." The invention discloses a method for invasive cardiac treatment, the method comprising inserting a catheter into a beating heart of a patient who is anesthetically paralyzed and intubated for ventilation via a transvascular path, and temporarily stopping ventilation of the patient after the catheter is inserted. The method comprises moving the catheter between a plurality of locations of myocardial tissue of the heart with the ventilation stopped, and ablating the myocardial tissue of the heart at the plurality of locations with the ventilation stopped.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to invasive medical procedures, and in particular to cardiac ablation. BACKGROUND

[0002] The fact that the heart is not a stationary object complicates the ablation of cardiac tissue, for example, to treat arrhythmias, and any device used for ablation has to contend with the motion of the heart.

[0003] For example, U.S. Patent Application 2003 / 0018251 to Solomon provides a system for superimposing the position and orientation of a device on previously acquired three-dimensional anatomic images, such as CT or MRI images, to enable navigation of the device to a desired location. Multiple previously acquired three-dimensional images can be used to create a "movie" of the beating heart, and these images can be synchronized with the EKG of the patient in the operating room, and the position of the device can be superimposed on the synchronized "movie" of the beating heart. SUMMARY

[0004] Exemplary embodiments of the present invention provide a method for invasive cardiac treatment, the method comprising:

[0005] inserting a catheter into a beating heart of a patient who is anesthetically paralyzed and intubated for ventilation via a transvascular path;

[0006] temporarily stopping ventilation of the patient after inserting the catheter;

[0007] moving the catheter between a plurality of locations of myocardial tissue of the heart with the ventilation stopped; and ablating the myocardial tissue of the heart at the plurality of locations with the ventilation stopped.

[0008] In exemplary embodiments disclosed herein, the method includes measuring the oxygen and carbon dioxide levels of the patient, and ensuring that the oxygen and carbon dioxide levels are within acceptable limits while ablating the tissue with the ventilation stopped. The method can also include stopping the ablation and resuming ventilation of the patient when the oxygen and carbon dioxide levels are not within acceptable limits.

[0009] In another exemplary embodiment disclosed herein, the catheter is selected from one of a balloon, a basket, a snare, a lesion, and a multi-strand catheter.

[0010] In yet another exemplary embodiment disclosed herein, the catheter includes an electrode, and ablating the myocardial tissue includes ablating the tissue with radiofrequency energy injected into the tissue via the electrode and configured to cause cell necrosis.

[0011] In yet another example embodiment disclosed herein, the catheter includes an electrode, and ablating myocardial tissue of the heart includes ablating the tissue with radiofrequency energy injected into the tissue via the electrode and configured to cause irreversible electroporation so as to cause apoptosis.

[0012] In an alternative example embodiment, the catheter includes a magnetic position sensor, and inserting the catheter includes tracking a position of the catheter within the beating heart using the magnetic position sensor.

[0013] In another alternative example embodiment, the catheter includes an electrode, and inserting the catheter includes tracking a position of the catheter within the beating heart in response to at least one of a current passing through the electrode and an impedance measured between the electrode and a conductive patch positioned on the patient.

[0014] In yet another alternative example embodiment, the method includes measuring an oxygen level of the patient, and using the ventilation to increase the oxygen level prior to stopping the ventilation.

[0015] In yet another alternative example embodiment, ablating myocardial tissue of the heart at a given location of the plurality of locations includes ablating the tissue at the given location for up to 4 seconds.

[0016] Ablating myocardial tissue of the heart at the plurality of locations can include ablating the tissue at the plurality of locations for up to 4 minutes.

[0017] According to an example embodiment of the present application, there is also provided apparatus for invasive cardiac treatment, the apparatus comprising:

[0018] a ventilator configured to provide ventilation to a patient that is anesthetically paralyzed and intubated;

[0019] a catheter configured to be inserted into a beating heart of the patient via a transvascular path, and to move between a plurality of locations of myocardial tissue of the heart with the ventilation stopped; and

[0020] a power source configured to ablate myocardial tissue of the heart at the plurality of locations with the ventilation stopped.

[0021] According to an embodiment of the present application, there is also provided a method of invasive cardiac treatment, the method comprising:

[0022] inserting a catheter into a beating heart of a patient that is anesthetically paralyzed and intubated ventilation via a transvascular path;

[0023] temporarily inducing the patient to hyperventilate after inserting the catheter;

[0024] moving the catheter between a plurality of locations of myocardial tissue of the heart with the ventilation stopped.

[0025] ablate myocardial tissue of the heart at multiple locations in the event of induced hyperventilation.

[0026] According to exemplary embodiments of the present application, there is also provided apparatus for invasive cardiac treatment, the apparatus comprising:

[0027] a ventilator configured to provide ventilation to a patient who is anesthetized, paralyzed and intubated;

[0028] a catheter configured to be inserted via a transvascular path into the beating heart of the patient, and to move between multiple locations of myocardial tissue of the heart in the event of induced hyperventilation of the patient by the ventilator; and

[0029] a power source configured to ablate myocardial tissue of the heart at multiple locations in the event of induced hyperventilation. BRIEF DESCRIPTION OF DRAWINGS

[0030] The present application will be more fully understood from the following detailed description of exemplary embodiments thereof, taken together with the drawings in which:

[0031] Figure 1 is a schematic illustration of a system for cardiac ablation according to exemplary embodiments of the present application;

[0032] Figure 2 is a flowchart of steps of an algorithm performed in the operation of the system according to exemplary embodiments of the present application; and

[0033] Figure 3 is a flowchart of steps of an alternative algorithm performed in the operation of the system according to exemplary embodiments of the present application.

[0034] Detailed description of exemplary embodiments

[0035] SUMMARY

[0036] Radiofrequency (RF) ablation of tissue in the heart relies on good contact between the ablation electrode and the tissue being ablated. However, the fact that the tissue is not stationary complicates the contact. The tissue moves due to the beating of the heart and also due to the patient breathing. While catheter positioning can be configured to reduce the effect of both of these movements on the electrode-tissue contact, it can not be able to completely eliminate the effect of the movements.

[0037] Exemplary embodiments of the present application effectively eliminate the breathing movements during ablation, as follows. A catheter is inserted into the beating heart of a patient who is anesthetized, paralyzed and intubated for ventilation. Ventilation is temporarily stopped, and the catheter is moved to multiple locations within the heart. Ablation is then performed at the multiple locations.

[0038] Exemplary embodiments of the present application use the fact that each ablation, when injecting RF, can typically last about four seconds or even less. In some exemplary embodiments, prior to the ablation procedure, the patient can be ventilated to raise the patient's oxygen level, and then the ventilation is turned off. The ablation procedure is then performed, and while the ablation procedure is performed, the patient's O2 and CO2 levels are monitored. As long as the O2 and CO2 levels remain within permissible limits (which is typically the case, since the patient is under anesthesia), the ablation continues.

[0039] By temporarily stopping the patient's breathing during the ablation, the catheter is more stable. In some cases, a complete set of ablations can be performed without the need to re-engage ventilation.

[0040] In alternative exemplary embodiments of the present application, rather than turning off ventilation, the patient is induced to hyperventilate. Hyperventilation results in shallower and at a higher frequency of motion of the catheter due to breathing, so that any such motion can be easily filtered. DETAILED DESCRIPTION

[0041] Figure 1 is a schematic illustration of a catheter-based system 20 for cardiac ablation according to an exemplary embodiment of the present application. System 20 includes a lesion catheter 21 that includes an insertion tube 22 for transvascular insertion into a beating heart 26 of a patient 28, who is shown lying on an operating table 29. A distal tip 40 is deployed at a distal end of insertion tube 22 (as shown in the inset in Figure 1 In the exemplary embodiment shown, tip 40 is applied to a therapeutic procedure that includes ablation of tissue surrounding ostia 51 of pulmonary veins in the left atrium of heart 26. To perform the ablation, tip 40 has one or more electrodes 55 disposed on a tip surface.

[0042] A proximal end of catheter 21 is connected to a console 24 that includes a power source 45, which typically includes radio frequency (RF) signal generation circuitry. Power source 45 provides an RF electrical signal to electrodes 55 via electrical wires that pass through insertion tube 22, in order to ablate tissue that is in contact with the electrodes. Depending on the voltage, frequency, and power of the RF electrical signal, the ablation can be performed by RF energy injection into the heart tissue or by irreversible electrical perforation (IRE) of the heart tissue. RF energy injection causes cell necrosis in the tissue by heating; IRE causes cell apoptosis. In the disclosure and claims, the term "ablation" is assumed to include either form of application of the RF signal provided by power source 45. In addition or alternatively, electrodes 55 can be used for electrophysiological (EP) sensing and mapping of electrical signals in heart 26.

[0043] To perform the ablation procedure, patient 28 was first anesthetized, intubated with a tube 70, and then ventilated with a ventilator 72. Anesthesia and ventilation can be performed by qualified professionals such as an anesthesiologist. Figure 1 (Not shown in the image) is used to perform this. During patient 28's ventilation, the oxygen (O2) and carbon dioxide (CO2) levels in the patient's blood are checked using the corresponding meters 74 and 76 to ensure they are within acceptable ranges and that ventilation is satisfactory. In an exemplary embodiment, the oxygen level is in the range of 75 mm Hg to 100 mm Hg, and the carbon dioxide level is approximately 35 mm Hg to 40 mm Hg.

[0044] After performing the above-described intubation, the physician 30 inserts the sheath 23 into the heart 26 of the patient 28 via a transvascular route, and then passes the insertion tube 22 through the sheath. By manipulating the catheter 21 with a manipulator 32 near the proximal end of the catheter, the physician 30 advances the end 40 of the insertion tube 22 toward a target location in the heart 26 (e.g., adjacent to the orifice 51).

[0045] After the distal end 40 of the insertion cannula 22 has reached the left atrium in the heart 26, the physician 30 retracts the sheath 23 and further manipulates the catheter 21 to navigate the distal end to the target location within the orifice 51 of the pulmonary vein. Once the distal end 40 has reached the target location, the electrode 55 contacts the tissue surrounding the orifice. The console 24 verifies good contact between the electrodes and the tissue by measuring the impedance between each electrode and the tissue. After establishing good contact, the physician 30 actuates the power source 45 to apply RF power to the tissue.

[0046] During the procedure, system 20 uses magnetic position sensing to track the position and orientation of the insertion cannula 22 and distal end 40 within the heart 26, thus guiding physician 30 to manipulate the distal end to the target location (in this example, within the mouth 51) and verify that the end is properly positioned. For this purpose, as... Figure 1 As shown in the illustration, the end 40 of the insertion tube 22 includes a magnetic position sensor 39. One or more magnetic field generators 36 are fixed at a known location adjacent to the patient's body 28, such as under the bed 29. Figure 1 As shown. The drive circuit 34 in the console 24 applies a drive signal to the magnetic field generator to generate multiple magnetic field components pointing along different corresponding axes.

[0047] During the navigation of the end-effector 40 within the heart 26, the magnetic sensor 39 outputs a signal in response to the magnetic field component. Position sensing circuitry (such as the processor 41 in the console 24) receives these signals via interface circuitry 44 and processes them to determine the position and orientation coordinates of the end-effector 40.

[0048] The processor 41 presents the coordinates of the end 40 on the display 27, for example by overlaying a graphical representation of the end (using the position and orientation indicated by the position sensor 39) onto a three-dimensional mapping of the ventricle (in which the end is located).

[0049] The method and apparatus for magnetic position sensing implemented in system 20 are based on those manufactured by Biosense Webster, Inc. (Irvine, California). The methods and apparatus used in the system. The operating principles of such magnetic sensing are described in detail in, for example, U.S. Patent Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, PCT Patent Publication WO 96 / 05768, and U.S. Patent Application Publications 2002 / 0065455 A1, 2003 / 0120150 A1, and 2004 / 0068178 A1, the disclosures of which are incorporated herein by reference in their entirety as if listed in full. Alternatively or otherwise, System 20 may implement other magnetic position sensing techniques known in the art.

[0050] Additionally, or alternatively, system 20 may implement current and / or impedance position sensing techniques that use impedance / current measurement module 46 to measure the position of electrode 55 in response to current flowing through the electrode and / or impedance of the electrode. Module 46 is connected via cable 37 to a plurality of conductive patches 38 positioned on the skin of patient 28. When configured in current position measurement mode, module 46 injects current into electrode 55 and measures the current flowing through the electrode to patch 38. Based on the measured current, a processor such as processor 41 calculates the position and orientation of electrode 55. When configured in impedance position measurement mode, module 46 measures the impedance between electrode 55 and patch 38. Based on the measured impedance, the position and orientation of electrode 55 can be calculated.

[0051] The method and apparatus for current or impedance position sensing implemented in system 20 are also based on... The methods and apparatus used in the system. The operating principles of these systems are described in detail in, for example, U.S. Patent Nos. 7,756,576, 7,869,865, 7,848,787, and 8,456,182, the disclosures of which are incorporated herein by reference in their entirety as if listed in full.

[0052] In some example embodiments, the processor 41 comprises a general purpose computer having suitable interface circuitry 44 for receiving signals from the catheter 21 (including low noise amplifiers and analog / digital converters) and for receiving signals from and controlling the operation of the other components of the system 20. The processor 41 typically performs these functions under the control of software stored in a memory 48 of the system 20. This software can be downloaded to the computer in electronic form, over a network, for example, or it can alternatively or additionally be supplied and / or stored on non-transitory tangible media, such as magnetic, optical or electronic storage media. In addition to, or alternatively, at least some of the functionality of the processor 41 can be performed by dedicated or programmable hardware logic.

[0053] Figure 2 A flowchart 90 of the steps of an algorithm performed in the operation of the system 20 in accordance with an example embodiment of the present application. In an initial step 100, the patient 28 is prepared for the ablation procedure by being anesthetized, intubated and ventilated as described above. In addition, the tip 40 is inserted into the patient 28 as described above so that the electrodes 55 contact the desired location of the ostium 51 of the heart 26. During the insertion, the ventilation of the patient is checked by monitoring the levels of O2 and CO2 in the patient's blood, and the ventilation is adjusted accordingly to maintain the levels at satisfactory values.

[0054] In an ablation preparation step 104, the ventilation of the patient 28 is temporarily stopped. Typically, prior to the stop, the ventilation is adjusted to increase the oxygen level in the patient's blood to near the upper limit of the permissible oxygen level. In one embodiment, the upper limit is about 100 mm Hg. Increasing the oxygen level provides the patient 28 with more ablation time, as described in the following steps of the flowchart. When the ventilation is stopped, both the O2 and CO2 levels are continued to be monitored to ensure that they remain satisfactory.

[0055] In a decision step 108, the O2 and CO2 levels of the patient 28 are checked when the ventilation is stopped to ensure that they are within acceptable limits. It will be appreciated that after the ventilation is stopped as specified in step 104, the decrease in the O2 level and the increase in the CO2 level occur at a relatively slow rate because the patient is unconscious. In one example embodiment, the acceptable limit for the oxygen level is greater than about 60 mm Hg, and the acceptable limit for the carbon dioxide level is less than about 45 mm Hg.

[0056] If the decision step 108 returns an affirmative value, i.e., the O2 and CO2 levels of the patient 28 are within acceptable limits, then in an ablation step 112, the physician 30 actuates the power source 45 so as to ablate the tissue at the site contacted by the electrodes 55 of the tip 40. After the ablation is satisfactorily performed, the physician deactivates the power source 45.

[0057] At the end of the ablation in step 112, in a movement step 114, the physician manipulates the tip 40 to move so that the electrodes 55 contact a new site. Control of the flowchart then returns (as indicated by arrow 116) to the ablation step 112 via the decision step 108 so that ablation is performed at the new site.

[0058] The exemplary embodiment of the present application continuously monitors the O2 and CO2 levels of the patient 28 so that when the decision step 108 returns a positive value, the ablation step 112 and the movement step 114 iterate.

[0059] If the decision step 108 returns a negative value, i.e., the O2 or CO2 levels of the patient 28 are not within acceptable limits, then control proceeds to a ventilation step 120 in which ventilation is resumed and ablation can be stopped.

[0060] Figure 3 A flowchart 190 of steps performed in an alternative algorithm in the operation of the system 20 according to an exemplary embodiment of the present application. The algorithm of the flowchart 190 is generally similar to that of the flowchart 90 except for the differences described below, so that the actions of the steps indicated by the same reference numerals in both flowcharts are generally the same.

[0061] In the flowchart 190, an over-ventilation step 204 replaces the ablation preparation step 104 of the flowchart 90. In the over-ventilation step 204, the patient 28 is not stopped from ventilation as in the flowchart 90, but is over-ventilated, i.e., induced to hyperventilate. The hyperventilation can be as high as four times the regular ventilation rate, and in one embodiment, the hyperventilation is 150 breaths / minute, or even higher. While the patient is over-ventilated, both the O2 and CO2 levels are continuously monitored to ensure that they remain satisfactory. The over-ventilation results in shallower respiratory movements of the patient, i.e., with a smaller amplitude than regular breathing or ventilation. The shallow breathing significantly improves the stability of the tip 40. In addition, the low amplitude and high frequency of this movement cause the processor 41 to filter out any such movement.

[0062] In the flowchart 190, a ventilation step 220 replaces the ventilation step 120 in the flowchart 90. The ventilation step 220 is invoked when the decision step 108 returns a negative value, and this step includes stopping the over-ventilation and resuming normal ventilation.

[0063] Looking at both flowcharts, in some example embodiments, the time of each ablation step 112 (i.e., the duration of activation of the power source 45) can be as short as about four seconds. Assuming a movement time of about six seconds, the time for ablating one site and moving to another site (including one pass through steps 112 and 114) is about 10 seconds. Since the patient 28 is comatose, the duration of the iterations of steps 112 and 114 can be up to about four minutes in total. Thus, embodiments of the present application enable the physician to accurately perform ablation at multiple locations, such as around the ostium 51, and even to move the tip 40 to one or more alternative locations, such as another ostium, and to perform ablation at each of the alternative locations.

[0064] The above description assumes that ablation is performed using a lesion catheter. However, the principles of the present application can be similarly applied, mutatis mutandis, to other types of catheters, such as a snare, basket, balloon, and / or multi-stick catheter having one or more electrodes suitable for ablation. It should also be understood that embodiments of the present application are not only directed to use in specific regions of the heart, but can also be applied, mutatis mutandis, to any region of a beating heart or the periphery of a beating heart.

[0065] It should therefore be understood that the embodiments described above are cited by way of example, and that the present application is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present application includes both combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which would occur to persons of ordinary skill in the art upon reading the foregoing description and which are not disclosed in the prior art.

Claims

1. An apparatus for invasive cardiac treatment, comprising: one or more processors; and a non-transitory computer-readable medium storing a plurality of instructions that, when executed, cause the one or more processors to: (a) cause ventilation supply from a ventilator to a patient to be adjusted to increase the patient's oxygen level prior to ablation of myocardial tissue of the patient using a catheter that has been inserted into the patient's heart via a transvascular path, (b) continuously monitor the patient's oxygen and carbon dioxide levels, (c) cause the patient's ventilation to be temporarily stopped prior to ablation, (d) activate a power source to ablate myocardial tissue of the heart at one or more locations when the ventilation is temporarily stopped and the monitored oxygen and carbon dioxide levels are within acceptable limits, (e) deactivate the power source to stop ablation at the one or more locations when the monitored oxygen and carbon dioxide levels are not within acceptable limits, (f) cause ventilation to be restored until the monitored oxygen and carbon dioxide levels are within acceptable limits, and (g) repeat steps (c)-(f) until the invasive cardiac treatment is complete. a meter configured to measure the patient's oxygen level and carbon dioxide level.

2. The apparatus of claim 1, and comprising: the catheter is selected from one of a balloon, a basket, a snare, a lesion, and a multi-strand catheter.

3. The apparatus of claim 1, wherein, the catheter includes an electrode, and wherein ablating the myocardial tissue includes ablating the tissue with radiofrequency energy injected into the tissue via the electrode and configured to cause cell necrosis.

4. The apparatus of claim 1, wherein, the catheter includes an electrode, and wherein ablating the myocardial tissue includes ablating the tissue with radiofrequency energy injected into the tissue via the electrode and configured to cause irreversible electroporation so as to cause cell apoptosis.

5. The apparatus of claim 1, wherein, the catheter includes a magnetic position sensor, and wherein inserting the catheter includes using the magnetic position sensor to track a position of the catheter within the beating heart.

6. The apparatus of claim 1, wherein, the catheter includes an electrode, and wherein inserting the catheter includes tracking a position of the catheter within the beating heart in response to at least one of a current passing through the electrode and an impedance measured between the electrode and a conductive patch positioned on the patient.

7. The apparatus of claim 1, wherein, a meter configured to measure the patient's oxygen level, and wherein the plurality of instructions further cause the one or more processors to increase the oxygen level using the ventilation prior to stopping the ventilation.

8. The apparatus of claim 1, and comprising: ablation of the myocardial tissue of the heart at the one or more locations includes ablating the tissue at the one or more locations for up to 4 seconds.

9. The apparatus of claim 1, wherein, ablation of the myocardial tissue of the heart at the one or more locations includes ablating the tissue at the one or more locations for up to 4 minutes.

10. The apparatus of claim 1, wherein, ​

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