Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
  • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
  • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
  • A61B18/1206—Generators therefor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
  • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
  • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
  • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
  • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
  • A61B18/14—Probes or electrodes therefor
  • A61B18/1492—Probes or electrodes therefor having a flexible, catheter-like structure, e.g. for heart ablation
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B2017/00017—Electrical control of surgical instruments
  • A61B2017/00022—Sensing or detecting at the treatment site
  • A61B2017/00039—Electric or electromagnetic phenomena other than conductivity, e.g. capacity, inductivity, Hall effect
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B2017/00017—Electrical control of surgical instruments
  • A61B2017/00022—Sensing or detecting at the treatment site
  • A61B2017/00084—Temperature
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
  • A61B2018/00636—Sensing and controlling the application of energy
  • A61B2018/0066—Sensing and controlling the application of energy without feedback, i.e. open loop control

Definitions

• the invention relates to a method and a device for detecting the contact of a catheter arranged in a patient's vessel, in particular in the bloodstream of a patient, with the tissue and also to a method and a device for detecting the interaction of high-frequency energy with the patient's tissue.
• the desired treatment effect can generally only be achieved if contact between the ablation catheter and the patient's tissue to be treated can be ensured during the entire duration of action of the delivered ablation performance.
• resistance measurements have been made between at least two to detect the catheter-tissue contact Catheter electrodes or the catheter electrodes and an indifferent electrode arranged on the patient's body.
• this procedure is disadvantageous, in particular in the case of high-frequency catheter ablation, because the resistance measurement is in principle connected to a current flow through the area to be measured.
• this introduces additional currents during ablation, which can be extremely disruptive, for example when recording the ECG signals.
• DC resistance measuring methods are used in order to avoid high-frequency signals which influence the ECG detection, undesirable electrolytic effects are generated which lead to further chemical stress on the patient.
• resistance measurements are difficult to carry out and prone to failure wherever corrosive influences and surface contamination impede the flow of current or falsify the measurement result.
• the invention is therefore based on the object of avoiding the disadvantages mentioned above and of contributing to an improved detection of the contact between the catheter and the patient's tissue.
• the inventor has surprisingly found that in many cases when electrodes are applied to the tissue of patients, especially with blood-washed tissue, voltages between the electrodes and in particular during HF ablation occur.
• the preferably metallic electrode of an ablation catheter generates, for example, the voltage signal shown in FIG. 1, which was obtained according to the invention in the measurement setup shown in FIG. 2.
• a catheter arranged in the bloodstream generates a voltage signal, which is initially referred to here as U 0 , and is only very weak, whereas an abrupt increase in voltage occurs when the catheter electrode comes into contact with the tissue.
• the voltage signal obtained in this way represents a measure of the quality of the catheter-tissue contact and can be detected without using additional external currents. Consequently, no electrolytic processes will occur in the manner according to the invention, and it can be assumed that further measurements, such as, for example, the recording of EKG signals, are not adversely affected.
• the voltage measurement according to the invention is also clearly superior to the conventional resistance measurement in relation to the measurement data obtained.
• the voltage is an extremely precise measure of the contact of the catheter electrode with the tissue, while an impedance measurement during ablation only indicates the tissue contact of the catheter to a limited extent, and on the other hand, this signal occurs with almost no time delay, which this causes for real-time measurement makes suitable.
• the level of the measured signal corresponds very precisely to the temperature of the tissue, in particular the correlates during an ablation of warming tissue.
• temperature values of the tissue lying on the catheter could be measured with an accuracy of +/- 1 ° C.
• Voltage measuring devices accuracies of +/- 2 ° C measurable.
• the temperature was regularly linearly related to the measured voltage, which made it possible to assign standardized voltage measurements to the same ablation catheter or to a group of identical catheters.
• the voltage signals that occur and are detected always ensure that the energy is essentially released into the tissue, and consequently, in the invention, the power delivered by the catheter can be directly and more precisely assigned to a treatment effect. Furthermore, after the abrupt voltage rise has detected the catheter / tissue contact, the absolute level of the voltage signal can be used for very precise temperature measurement.
• the voltage signal that occurs is used to control or monitor the ablation process itself. If, for example, in the case of high-frequency ablation, the voltage signals are detected during the delivery of the high-frequency power, and if the switch-off or at least a reduction in the delivery of the high-frequency power is effected if the value falls below or is exceeded, it is always ensured that the high-frequency power has essentially been released into the patient tissue. and there is treatment with cooler catheter electrodes overall and increased effectiveness.
• the switch-off or at least the reduction in the delivery of the high-frequency power is effected with a rapid increase or decrease in the potential values, the vaporization of the tissue to be treated can thereby be prevented or at least greatly restricted, since a very fast regulation is now possible and it is no longer necessary unwanted overheating of the tissue occurs.
• the potentials or voltage signals according to the invention can always be detected very reliably during the implementation of high-frequency ablation, regardless of whether the high-frequency signals for ablation are applied either continuously or in pulsed fashion. If the high-frequency power delivered by the catheter is integrated over time, as long as the voltage signals are above a predefinable limit value, which ensures that a catheter / tissue contact is present, and the integrated power is calculated as the ablation energy delivered into the tissue up to this point in time, the treating person can Not only the progress of the treatment success is indicated to the doctor, but the treatment can be terminated automatically by switching off or reducing the high-frequency power with a suitably programmed control device when a predetermined energy value is reached. As a result, a much higher level of treatment security can be provided than this was possible with the previous methods. For the first time, it is now possible to record the ablation effect during the course of the treatment by integrating the output and to display it to the treating doctor in real time.
• the treating doctor can specify tissue depths which are assigned to the temporal integral of the measured potentials.
• the device according to the invention can then either terminate the entire ablation process after the predetermined value has been reached, or, in the case of catheters with a plurality of electrodes, sections of the catheter within which the predetermined values have been reached can be switched off or less power can be supplied to them.
• the signal data can be assigned, recorded, calculated and displayed to the respective special electrode, and the treatment sequence can be programmably ended locally assigned to the treatment site.
• data that is optimized for the treatment can also be assigned locally before the start of the treatment, and a treatment that is optimized with respect to the respective patient can be carried out.
• Fig. 1 shows the waveform of the voltage according to the invention, as in a time-limited catheter electrode tissue contact in a system with an indifferent platinum electrode and Platinum catheter electrode occurs
• FIG. 2 shows a schematic illustration for carrying out the invention with a catheter and a device which corresponds, for example, to that described in PCT / DE96 / 00638, but was further developed in the manner according to the invention,
• FIG. 3 shows a laboratory measurement setup for standardization or calibration and acquisition of measurement data by means of a pig heart
• FIG. 6 shows a comparison of the values of the time integral of the potential values obtained according to the invention with lesion depths achieved during catheter ablation at different temperatures of the ablation catheter.
• the voltage taps of the low-pass filter a and b were connected to platinum electrodes of a bipolar catheter, as described for example in PCT / DE96 / 00638.
• the catheter 3 generally does not need to have any additional means for detecting the catheter temperature, such as thermal sensors, for carrying out the present invention, although this is not excluded by the invention.
• Catheter electrodes a and b the voltage between the indifferent electrode (s) 4 and one of the electrodes a, b of the catheter 3 can also be detected, or the location of the respective catheter electrode a, b can be detected.
• the low-pass filter 2 of the first embodiment according to the invention is connected to a storage oscilloscope of the Hameg HM 1007 type, which in the usual way represents a two-dimensional display device for the temporal display of voltage profiles.
• the initially low, flat section 5 of the basic signal Uo represents the voltage when the catheter 3 is in the blood stream and shows a clearly pronounced signal edge 6 as soon as the catheter 3 comes into contact with tissue 7.
• the signal shoulder 8 which extends substantially flat after the abrupt rise in the signal flank 6, shows a temporal modulation which can be attributed to the mechanical catheter-tissue contact between the cathecer electrode b and the tissue 7 in relation to the indifferent electrode 4 or the electrode a can be or with the generation and transport of chemical substances which cause electrical potentials at the location of the catheter, related.
• the abrupt rise 6 and fall 9 of the signal edge indicates the formation and termination of a catheter / tissue contact with a high degree of certainty.
• FIG. 3 The structure used to obtain the signal form shown in FIG. 1 is shown schematically in FIG. 3 in the form of a stationary measurement structure that can be used for standardization and calibration.
• An HF generator 11 is connected to the device for the controlled delivery of HF power to the catheter 3, which has a plurality of ablation electrodes, described in the PCT application cited above and supplies pulsed high-frequency power to the electrodes of the catheter 3.
• the high-frequency power can also be supplied to the catheter 3 continuously over time.
• the indifferent electrode 4 and tissue 7 are arranged within a trough 13, on which 3 ablation processes are carried out by means of the catheter.
• the trough 13 can either be filled with blood or with a suitable other liquid in order to simulate the conditions prevailing in the patient's body.
• the indifferent electrode 4 and the electrodes a and b of the catheter 3 are coated with platinum or consist of platinum and are cleaned with formalin or formaldehyde gas immediately before its use in such a way that there are essentially no surface residues on the catheter or the indifferent electrode 4 remain.
• FIG. 5 represents the comparison of the potential values according to the invention with temperatures which were recorded simultaneously at the location of the potential measurement.
• the correspondence of the temperature value shown in dashed lines with the potential value 23 shown in solid lines is correct As expected, it agrees well with the model given above, since chemical potentials are also largely temperature-dependent. However, if the temperature drops again after the treatment, as shown on the right-hand side of FIG. 5, the potential only drops to the increased value U 2 , which can be easily explained by the presence of the chemical substances discussed above.
• This threshold value indicates the minimum voltage value to be expected and, if undershot, can result in the ablation energy being switched off.
• FIG. 6 A further clear support of the explanatory model of the potential development can be found in FIG. 6, according to which the dependence of the depth of the lesions created in the tissue of a patient during HF ablation is shown on the time integral of the potentials that occur. These values are well correlated with one another over a temperature range of the ablation catheter of over 20 ° C., namely from less than 55 ° C. to more than 75 ° C. ablation temperature. Consequently, in known
• the catheter properties already have the temporal integral of the potential sufficient without additional temperature values having to be recorded in order to obtain a suitable statement about the course of the treatment.
• Such catheters could dispense with thermal sensors and consequently be manufactured more simply, more cost-effectively and with a smaller diameter.
• the evaluation unit 15 can also carry out a measurement of the potential values weighted or functionally linked with the output power, preferably in real time.
• FIG. 2 A further embodiment according to the invention is shown in FIG. 2, in which the pulsed generator 11 described in the PCT application cited above is connected to the catheter 3 and its catheter electrodes a and b.
• the catheter electrodes a and b are either the ablation electrodes themselves or measuring electrodes arranged in the vicinity thereof and assigned to the respective ablation electrodes, which are connected to the low-pass filter 2, which filters out both the high-frequency signal and hum signal interference.
• the downstream evaluation unit 15 comprises the voltage measuring device 1, which, as in the first embodiment according to the invention, has a high-impedance measuring input of at least more than 100 k ⁇ and preferably several M ⁇ input resistance in order to reduce any additional current flow for the variation process and of further measuring processes to a substantially no longer measurable value to suppress.
• a high-resistance voltage measurement is a voltage measurement that is no longer noticeable or is no longer detectable when performing the ablation or the measurement of, for example, ECG signals.
• a storage oscilloscope that can be connected to a personal computer as a control device
• the input resistance has about 1 M ⁇
• its input capacitance is not more than 30 pF.
• the measurement data obtained with the voltage measuring device 1 are recorded and stored in the evaluation unit 15.
• the data can be displayed either in real time or by reading them out of the memory of the evaluation unit 15 in a two-dimensional form on a display unit 21 and displayed, for example, for comparison purposes or for evaluating the success of the treatment.
• the display can take the form of a current voltage signal, a bar chart or any other ergonomically advantageous way for the treating doctor.
• a control device 16 assigned to the evaluation unit 15 can switch off or reduce the power output by the HF generator 11 if the measured voltage signal falls below a predetermined limit value U gl 17, in order to prevent the catheter or its surroundings from being heated up, without creating the desired ablation.
• the limit value U gl 17 can be changed as a function of the respectively delivered current ablation performance or integrated delivered ablation performance, ie delivered ablation energy, and can thus be specified very precisely. This considerably reduces or prevents contamination of the catheter by coagulated substances.
• the control device 16 can begin to integrate the power output by the HF generator 11 until the voltage signal either falls below the limit value U gl 17 or below any other predeterminable value falls off.
• the quantity associated with the energy release into the tissue is recorded, which allows the attending physician to make statements about the ablation effect.
• the depth of the lesion can also be represented as a function of the energy delivered and can be used to switch off the lesion process.
• the attending physician is assigned the respective catheter electrode the possibility of defining locally different depths or certain depths and lengths of the lesions generated, adjusting them on the control device 16 and subsequently implementing them automatically during the treatment.
• the attending physician can be given an optical or acoustic signal which supports him during the execution of the treatment and does not hinder the further execution of the ablation, for example on the basis of ECG data.
• a voltage peak is generally formed, which was measured as peak 20 in FIG. 1.
• processes can be used as a control variable by detecting the temporal differential and / or the absolute value of the potential curve or by a function depending on the two measured values, in order to interrupt the supply of high-frequency energy or at least locally reduce the process.
• control device 16 it is also within the scope of the invention to implement the control device 16 by means of an external computer or a personal computer 19.
• the invention is also not limited to high-frequency catheter ablation, but can be successfully used in most other catheter ablation methods to monitor the success of the treatment.

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• Veterinary Medicine (AREA)
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• Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
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• 1998
  • 1998-04-01 EP EP98928114A patent/EP0971636B1/de not_active Expired - Lifetime
  • 1998-04-01 AU AU80088/98A patent/AU740503B2/en not_active Ceased
  • 1998-04-01 US US09/402,222 patent/US6304776B1/en not_active Expired - Lifetime
  • 1998-04-01 JP JP54106898A patent/JP4105238B2/ja not_active Expired - Fee Related
  • 1998-04-01 DE DE59813142T patent/DE59813142D1/de not_active Expired - Lifetime
  • 1998-04-01 CA CA002285342A patent/CA2285342C/en not_active Expired - Fee Related
  • 1998-04-01 WO PCT/DE1998/000932 patent/WO1998043547A2/de not_active Ceased
  • 1998-04-01 AT AT98928114T patent/ATE307536T1/de not_active IP Right Cessation
  • 1998-04-01 ES ES98928114T patent/ES2249832T3/es not_active Expired - Lifetime
  • 1998-04-01 DK DK98928114T patent/DK0971636T3/da active

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