JPH0779992A - Radio frequency ablation device with phase sensitive power detection function - Google Patents

Abstract

(57) [Abstract] [Purpose] A function to detect the actual radio frequency power (phase sensitive power) is provided, and the radio frequency power is controlled based on this to perform the tissue resection procedure accurately and safely Provided is a radio frequency ablation device. A device for ablating tissue using radio frequency energy, comprising a source 30 of radio frequency energy.
An electrode means 16 which is electrically connected to the supply source and emits radio frequency energy at the ablation site; and a radio frequency current delivered to the electrode means 16 is measured and a measured radio frequency current signal Current monitor means 40 for generating
Voltage monitor means 42 for measuring the radio frequency voltage at the electrode means 16 and generating the measured radio frequency voltage signal;
An analog multiplier integrated circuit 58 which multiplies the measured current signal by the measured voltage signal to obtain a phase sensitive power signal representative of the actual phase sensitive power delivered to the electrode means.
And a control means 7 that performs a function based on the actual power signal.
It has 0 and.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to catheters and associated power sources. More specifically, the present invention relates to an ablation catheter that transmits energy to create a lesion for therapeutic purposes after being steered and manipulated in an internal region of the body.

[0002]

In today's medical procedures, physicians use catheters to access internal regions of the body to ablate areas of tissue of interest. It is important for the physician to carefully and accurately control the energy emission within the body used to ablate tissue.

The need for careful and precise control over the catheter is particularly critical during the procedure of ablating tissue within the heart. These procedures, called electrophysiological therapy,
It has been more widely used to treat rhythm disorders of the heart.

During these procedures, the physician advances the catheter through the vena cava or aorta (typically the femoral artery) to the interior region of the heart to be treated. The physician then further manipulates the steering mechanism so that the electrodes attached to the distal end of the catheter are in direct contact with the tissue to be excised. The doctor will remove the tissue to form the injury,
Radio frequency energy is radiated from the tip of the electrode through the tissue to the indifferent electrode.

Ablation of the heart is particularly characterized by its ability to accurately monitor and control the emission of energy from the ablation electrodes.
I need.

[0006]

Prior art devices control the radio frequency power to the ablation electrode based on the root mean squared result of the rapidly varying radio frequency voltage and current. These root-mean-squared results represent actual power only when the radio frequency voltage is in phase with the radio frequency current. When a phase shift occurs, the root mean squared voltage and current product differs from the actual power by the factor of the cosine of the phase angle. The root mean square result is then not directly used in the control decision to maintain the desired power level at the ablation electrode. In fact, when a large phase shift occurs, the root-mean-squared result can lead to incorrect control decisions.

The present invention has been made in view of the above circumstances, and has a function of detecting actual radio wave power (phase sensitive power), and by controlling the radio wave power based on this function, It is an object of the present invention to provide a radiofrequency ablation device that can accurately and safely perform a tissue ablation procedure.

[0008]

SUMMARY OF THE INVENTION A radiofrequency ablation device of the present invention is a device for ablating tissue using radiofrequency energy, the source of radiofrequency energy being electrically coupled to the source. Electrode means connected to emit radio frequency energy at the ablation site, current monitoring means for measuring the radio frequency current delivered to the electrode means and generating a measured radio frequency current signal, and the electrode means A voltage monitor means for measuring the radio frequency voltage at, and generating a measured radio frequency voltage signal, and an actual signal transmitted to the electrode means by multiplying the measured current signal by the measured voltage signal. It comprises a power monitor means for obtaining a phase sensitive power signal representing the phase sensitive power and a control means for performing a function based on the actual power signal, whereby the above object is achieved.

Further, the control means may include display means for indicating the value of the phase sensitive power signal in a user-readable format.

Further, the control means may include feedback means for controlling the voltage output of the supply source based on the phase sensitive power signal.

Further, the feedback means includes register means for storing a desired amount of phase sensitive power, the desired amount of phase sensitive power in the register means, and the phase sensitive power generated by the power monitor means. It may have a comparator means for comparing the electric power signal and generating a shift signal, and a command means for changing the output voltage of the supply means in response to the shift signal.

Further, the command means may change the output voltage of the supply source in order to maintain a predetermined minimum deviation signal.

Further, the device obtains root mean squared current signal based on the measured radio frequency current signal, and root mean squared voltage signal based on the measured radio frequency voltage signal. Means for multiplying the root mean squared current signal by the root mean squared voltage signal to obtain a root mean squared power signal representative of the apparent power transmitted to the electrode means; Comparing the power signal and the phase sensitive power signal generated by the power monitoring means, the phase between the measured radio frequency voltage signal and the measured radio frequency current signal at the electrode means. It is possible to further include a phase shift detection means having a means for generating a shift signal indicating a shift and a phase shift control means for performing a function based on the phase shift shift signal. There.

Furthermore, the phase shift control means can interrupt the conduction of radio frequency energy when the phase shift deviation signal exceeds a predetermined value.

Further, the phase shift control means can generate a warning signal when the phase shift deviation signal exceeds a predetermined value.

Further, the control means has a feedback means for controlling the voltage output of the supply source based on the phase sensitive power signal when the phase shift deviation signal remains within a predetermined range. Good.

Further, the feedback means can reduce the output voltage of the supply source when the phase shift deviation signal increases beyond a predetermined range.

Further, the feedback means may interrupt the power to the electrode means when the phase shift deviation signal exceeds a predetermined maximum value.

Further, the apparatus has means for obtaining a root mean squared current signal based on the measured radio frequency current signal, and a root mean squared voltage signal based on the measured radio frequency voltage signal. Means for determining the measured tissue impedance signal by dividing the root mean squared voltage signal by the root mean squared current signal, and impedance control for performing a function based on the measured tissue impedance signal. And a tissue impedance monitoring means having a means.

Further, the impedance control means comprises:
It is also possible to calculate the change in the measured tissue impedance signal during a selected interval and generate a control signal based on predetermined criteria.

Further, the impedance control means comprises:
A command signal may be generated that interrupts energy to the electrode means when the measured tissue impedance signal is outside a predetermined range.

Further, the predetermined range is approximately 50 to 30.
It may be 0 ohm.

Further, the impedance control means is
A control signal may also be generated when the measured tissue impedance signal begins to fall into a range and increases over time, indicating coagulation of blood on the electrode means.

Further, the impedance control means comprises:
A control signal may also be generated in response to an increase in the measured tissue impedance signal by more than a certain amount, which is indicative of the initiation of coagulation or a sudden shift in the position of the electrode means.

Further, the impedance control means is
A control signal can also be generated if the measured tissue impedance signal exceeds a predetermined maximum amount, indicating poor skin contact to the electrode means or electrical problems in the device.

Further, the impedance control signal is
A display device may be provided to show the value of the measured tissue impedance signal in a user-readable format.

[0027]

The present invention provides an improved device for ablating tissue using radio frequency energy. This device controls the delivery of radio frequency energy to the ablation electrode based on the measurement of the actual phase sensitive power being delivered.
The device also detects when a phase shift occurs between the radio frequency voltage and the radio frequency current and initiates the appropriate action.

In one embodiment, the device comprises a source of radio frequency energy. The electrode portion emits radio frequency energy delivered by the source at the ablation site. The device measures the radiofrequency current delivered to the electrode portion and produces a measured radiofrequency current signal. The device also measures the radio frequency voltage at the electrode portion and produces a measured radio frequency voltage signal.

According to one embodiment of the invention, the device comprises a power monitor which multiplies the measured current signal by the measured voltage signal. This causes the monitor to determine a phase sensitive power signal representative of the actual phase sensitive power transmitted to the electrode means. The device comprises a controller that performs a function based on the actual power signal.

In one configuration, the controller displays the value of the phase sensitive power signal in a user readable format.

In another configuration, the controller has a feedback loop that controls the voltage output of the source based on the phase sensitive power signal.

According to another embodiment of the invention, the device comprises a radio frequency phase shift detector. The detector determines a root-mean-squared current and voltage signal based on the measured radio frequency current signal and the measured radio frequency voltage signal. The detector multiplies the root mean squared current signal by the root mean squared voltage signal. This gives a mean squared power signal. This signal represents the apparent power transmitted through the electrode means. The detector compares the root mean squared power signal with the phase sensitive power signal generated by the power monitor. The detector produces a shift signal representative of the magnitude of the phase shift between the measured radio frequency voltage signal and the measured radio frequency current signal. The detector performs a function based on the phase shift signal.

In one configuration, the phase detector interrupts the conduction of radio frequency energy when the phase shift signal exceeds a predetermined value.

In the preferred arrangement, the source power feedback loop controls the voltage output of the source based on the phase sensitive power signal when the phase shift signal remains within a predetermined range. If the phase shift signal exceeds this range, the feedback loop will reduce the output voltage of the source. When the phase shift signal exceeds a predetermined maximum amount, the feedback loop interrupts the power to the electrode portion.

According to the present invention, the device controls the radio frequency power to the ablation electrode in response to the actual phase sensitive power measurement. The device also detects the phase difference between the radio frequency voltage and the radio frequency current and incorporates this factor in making its control decision.

[0036]

EXAMPLES The present invention will be described below with reference to examples.

FIG. 1 shows an apparatus 10 for performing an ablation on human tissue, which embodies features of the present invention.
The device 10 comprises a radio frequency generator 12 that delivers radio frequency energy. The device 10 also includes a steerable catheter 14 having a tip electrode 16 for radio frequency radiation.

In the illustrated embodiment, the device 10 operates in a monopolar mode. In this configuration, the device 10
Equipped with skin patch electrodes. This electrode functions as the indifferent second electrode 18. In use, indifferent electrode 18
Adheres to the patient's back or other external skin area.

Alternatively, the device 10 can also operate in bipolar mode. In this mode, the catheter 14 is provided with both electrodes.

In the illustrated embodiment, the ablation electrode 16
The indifferent electrode 18 is made of platinum.

The device 10 can be used in many different environments. Described herein is a device 10 when used to perform ablative treatments of the heart.

When used for this purpose, the physician advances the catheter 14 through the vena cava or aorta (typically the femoral artery) to the interior region of the heart to be treated. Next, the physician further manipulates the catheter 14 to position the tip electrode 16 against tissue within the heart to be ablated. The user sends radio frequency energy from the generator 12 into the tip electrode 16 to create lesions on the contacted tissue.

In the embodiment shown in FIG. 1, the catheter 14 comprises a handle 20, a guide tube 22 and a tip 24, which is provided with a tip electrode 16 (hereinafter also referred to as ablation electrode). There is. The handle 20 incorporates a steering mechanism 26 for a catheter tip 24. The cable 28 extending from the rear of the handle 20 has a plug (not shown). The plug is
Catheter 14 is connected to generator 12 for delivering radio frequency energy to ablation electrode 16. The radio frequency heats the tissue to form the lesion.

Left and right steering wires (not shown) extend through the guide tube 22 so as to interconnect the steering mechanism 26 to the left and right sides of the tip 24. When the steering mechanism 26 is rotated counterclockwise, the left steering wire is pulled and the tip 2
4 is bent to the left. Similarly, rotating the steering mechanism 26 to the right pulls the right steering wire and bends the tip 24 to the right. Thus, the physician steers the ablation electrode 16 to contact the tissue to be ablated.

The generator 12 comprises a radio frequency power supply 30 which is connected to the first and second conductors 34 and 36 through a main isolation transformer 32.

In the illustrated environment, the power source 30
Delivers up to 50 watts of power at a frequency of 500 kHz. The first conductive line 34 extends to the ablation electrode 16. The second conductive line 36 continues to the indifferent patch electrode 18.

The actual and apparent radio frequency power monitor
As shown in FIGS. 2 and 3, the device 10 comprises first monitoring means 38 for measuring the radiofrequency current and the radiofrequency voltage delivered by the generator 12 to the patient.
The first monitor means 38 also includes RMS (root mean square) voltage (in volts), RMS current (in amps).
And a control signal indicative of the actual phase sensitive power (in watts) is derived to support other control functions of the generator 12.

The first monitor means 38 can have various structures and configurations. In the illustrated embodiment, the first monitoring means 38 passes radio waves from the first line 34 through the tissue to the second line 36 (ie, from the ablation electrode 16 to the indifferent patch electrode 18). A current monitor 40 for measuring the current is provided.

The first monitor means 38 also comprises voltage monitor means 42. The voltage monitoring means 42 is arranged between the first and second conducting wires 34 and 36 (ie the ablation electrode 1
6 and the indifferent patch electrode 18).

The first monitor means 38 has three control outputs 44, 46 and 48. First control output 44
Carries a signal representative of the RMS current conducted by the ablation electrode 16.

The second control output 46 carries a signal representative of the RMS voltage between the ablation electrode 16 and the indifferent patch electrode 18.

The third control output 48 carries a signal representative of the actual phase sensitive power transmitted by the ablation electrode 16.

In the illustrated embodiment (FIGS. 2 and 3)
(As shown in FIG. 2), the current monitoring means 40 includes an isolated current sensing transformer 50 connected at the second conducting wire 36.
have. In this configuration, the current sensing transformer 50
Directly measures the radio frequency current passing through the ablation electrode 16 to the indifferent patch electrode 18.

The measured value is a radio frequency signal varying at a selected rate, 50 in the illustrated embodiment.
It is 0 kHz.

The current sensing transformer 50 has a first control output 4
4 and determines the RMS current. The first control output 44 comprises an integrated circuit RMS converter 52 to perform this function. The RMS current converter first squares the radio frequency current input signal from the current sensing transformer 50 and then averages the squared signal over a user-defined period (in the illustrated embodiment, about 0.
Once every 01 seconds). The RMS current converter 52 then takes the square root of the mean square value. The output obtained is RMS
Represents current.

The RMS current signal takes the form of a relatively slowly changing signal as compared to a rapidly changing radio frequency current input signal.

As shown in FIGS. 2 and 3, the voltage monitoring means 42 comprises a separate voltage sensing transformer 54 connected between the first and second conducting wires. In this configuration, the voltage sensing transformer 54 directly measures the radio frequency voltage on the body tissue between the ablation electrode 16 and the indifferent patch electrode 18.

Similar to the value measured by the current sensing transformer 50, the measured voltage value is the selected 500 kH.
It is a radio frequency signal that changes at the speed of z.

The voltage sensing transformer 54 has a second control output 4
6 and determines the RMS voltage. The second control output 46 comprises an integrated circuit RMS converter 56 for performing this function. RMS voltage converter 56
Squares the radio frequency voltage input signal and then averages it over the same user-defined period used by the current converter 52. The RMS voltage converter 56 then takes the square root of the mean square voltage value.

The resulting RMS voltage signal (like the RMS current signal) takes the form of a relatively slowly varying signal.

The voltage sensing transformer 54 has a third control output 4
8 is also connected to obtain the actual phase sensitive power.
The third control output 48 has an analog multiplier integrated circuit 58 to perform this function. The multiplier circuit directly receives as one input the radio frequency input current signal from the current sensing transformer 50. The multiplier circuit 58 directly receives the radio frequency input voltage signal from the voltage sensing transformer 54 as a second input.

The output of the multiplier circuit 58 is the product of these two inputs and represents the actual radio frequency power transmitted by the ablation electrode 16.

The power value (as well as its component current and voltage inputs) is a radio frequency signal that changes at a relatively radio frequency.

The third control output 48 also has a low pass filter 60. In the illustrated embodiment operating at a radio frequency of 500 kHz, the selected cutoff frequency of filter 60 is approximately 100 Hz. The rapidly changing measured input power value is low pass filtered by filter 60 into a relatively slowly changing signal.

This signal represents the actual phase sensitive power signal of the radio frequency energy delivered by the ablation electrode 16 to the tissue of interest.

First, second and third control outputs 44, 46
And 48 each include a suitable in-line scaling circuit 62. The scaling circuit 62 uses the RM
The S current signal, the RMS voltage signal, and the actual phase sensitive power signal are scaled (proportional converted) to a specific voltage range as enabled by the rest of the generator 12 circuitry. In the illustrated embodiment, the scaled range is 0.0 to 5.0 volts.

The first monitor means 38 also comprises an analog-to-digital converter 64. Converter 6
4 digitizes one or more selected analog RMS current output signals, RMS voltage output signals, and actual phase sensitive power signals.

The digital output or outputs of converter 64 can be used to display the measurement results. In the illustrated embodiment, the device 10 includes a first digital display 66 on the generator 12 to show the actual phase sensitive power signal to the user.

The digital output (s) of converter 64 can also be used to control the operation of generator 12. In the illustrated embodiment, the device 10
Uses the digitized output in a feedback loop that maintains the radio frequency output voltage in a desired range or constant to control the radio frequency power at the ablation electrode 16. By controlling the power delivered by the generator 12, the physician can reproducibly create the desired depth of injury during the ablation procedure.

In this configuration, the device 10 comprises the generator 1
An input device 68 is provided for the user to enter the desired operating value for the actual phase sensitive power for the two. The device 10 includes power control means 70. The power control means 70 has a comparator 71 for comparing the desired power with the actual phase sensitive power. The output of the comparator varies the output voltage of the radio frequency power source 30 so as to minimize the error between the measured actual power and the setpoint power.

In the illustrated embodiment, the power control means 70 also monitors the phase difference between the radio frequency voltage and the current. The power control means 70 performs this function by calculating the apparent power and comparing the calculated apparent power with the actual phase sensitive power. If the radio frequency voltage and the current signal have exactly the same phase, the apparent power and the actual phase sensitive power are the same. However, when there is a phase difference, the actual phase sensitive power differs from the apparent power by the coefficient representing the cosine of the phase angle.

In the illustrated embodiment, the power control means 70 comprises a multiplier circuit 72 which determines the product of RMS current and RMS voltage. The resulting output of multiplier circuit 72 forms the apparent (ie, phase insensitive) power of device 10. The power control means 70 comprises a comparator 74 for comparing the resulting apparent power with the actual phase sensitive power. The magnitude of the output of the comparator 74 is
Represents the amount of phase shift.

When the output of the phase shift comparator 74 exceeds a predetermined amount, the power control means 70 generates a warning signal indicating that a phase shift has occurred between the radio frequency voltage and the current. The device 10 may also include a flashing light and an alarm sound (not shown) to alert the user.

The power control means 70 includes the phase shift comparator 7
If the output of 4 remains within the acceptable range above the threshold amount, it operates to maintain a constant value of power. The power control means 70 operates to reduce the output voltage of the source 30 if the output of the phase shift comparator 74 increases beyond this range. If the output of the phase shift comparator 74 indicates a phase shift above the maximum threshold, the power control means 70 will generate a signal to shut off all power to the ablation electrode 16.

Monitoring Tissue Impedance As shown in FIG. 4, device 10 further comprises second monitoring means 76 for determining the impedance of the tissue undergoing ablation. The second monitor means 76 functions not only to obtain the tissue impedance in absolute terms, but also to record changes in the tissue impedance over time.

The second monitoring means 76 generates an appropriate control signal based on the observed absolute value of the tissue impedance and the sensed change according to preprogrammed criteria.

The second monitor means 76 can have various structures and configurations. In the illustrated embodiment, the second monitor means 76 comprises a microprocessor 78. Microprocessor 78 samples the digitized output of analog-to-digital converter 64 at predetermined intervals (eg, representing a sampling rate of 50 Hz every 20 milliseconds).

Microprocessor 78 also divides the sampled and digitized RMS voltage signal by the sampled and digitized RMS current signal. The numerical result is
Tissue impedance (in ohms) for the sample. Preferably, the device 10 has a second display 80 on the generator 12 that shows the sampled tissue impedance to the user.

The microprocessor 78 also maintains a record of the sampled tissue impedance over time. From this record, microprocessor 78 calculates the change in tissue impedance during the selected interval and generates an appropriate control signal based on a predetermined criterion.

The predetermined criteria by which the microprocessor 78 generates the control signal based on the tissue impedance can vary. Preferably, the tissue impedance control signal is the power control means 70 just described.
It is used to improve the monitor and control functions of the.

In the illustrated embodiment, when the measured tissue impedance is outside the predetermined set range, the microprocessor 78 causes the power to the ablation electrode 16 to be irrespective of how the actual phase sensitive power level is sensed. A command signal is generated to shut off the signal. The setting range for tissue impedance for cardiac ablation procedures is approximately 50-30.
Considered to be 0 ohms.

If the tissue impedance begins to fall into the set range and increases beyond that over time, the most likely cause is blood coagulation on the ablation electrode 16. A sudden rise in tissue impedance beyond the set range suggests a sudden onset of coagulation or a sudden shift in the position of the ablation electrode 16. Rapid changes in tissue impedance may also indicate poor contact between the ablation electrode 16 and the target tissue. Everything requires prompt attention. For example, withdrawal and cleaning of the ablation electrode 16 or the ablation electrode 16
It is a rearrangement.

The device 10 preferably includes a flashing light and an alarm sound (not shown) to alert the user when these conditions occur.

The very high tissue impedance may indicate poor contact of the indifferent electrode 18 to the skin or electrical problems in the device 10. Also in this case, a quick correction operation is required.

If the tissue impedance is within the set range but rises above a predetermined amount within the range, the second monitor means 76 will generate a control signal to reduce rather than interrupt the power output. In this configuration, a relatively narrow range of tissue impedance (eg, 80-150
Ohms) can be established to maintain a relatively constant power within this range.

Tissue Temperature Monitoring As shown in FIG. 5, the device 10 includes a third monitoring means 8 for sensing the temperature of the tissue in contact with the ablation electrode 16.
Equipped with 2. The third monitor means 82 is the ablation electrode 1
6 has a temperature sensing means 84. The device 10 responds to the sensed tissue temperature to perform a generator control function by a control means 86 for the generator 12.
Is equipped with.

The thermal insulation means 88 thermally isolates the temperature sensing means 84 from the ablation electrode 16. Therefore, the temperature sensing means 84 does not apply heat to the ablation electrode 16 or become part of the amount of heat. It acts to indicate the true temperature of the tissue in contact, does not apply heat to the ablation electrode 16, and
It is also unaffected by the temperature around the ablation electrode 16.

In the embodiment shown in FIGS. 6A-6C, the ablation electrode 16 has an inner well 90 at its tip 92.
have. The temperature sensing means 84 occupy this well.

In this configuration, the thermal insulation means 88 thermally insulates the temperature sensing means 84 from the inner surface of the well 90 and the rest of the ablation electrode 16.

In FIGS. 6A-C, the temperature sensing means 84 comprises a small bead thermistor 94 having two associated leads 96 and 98. The temperature sensitive end of the thermistor 94 is exposed at the tip 92 of the ablation electrode 16 for contact with tissue.

In the illustrated embodiment (FIG. 6 (a)-
(See (c)), the third monitor means 82 comprises means 132 for calibrating the thermistor 94 to account for deviations in nominal resistance among the different thermistors 94.
During the manufacture of the catheter 14, the resistance of the thermistor 94 is measured at a known temperature, for example 75 degrees Celsius. A calibration resistor 134 equal to the measured value is incorporated into the catheter handle 20. The lead wire of the calibration resistor 134 is connected to the third monitor means 82.

A thermistor 94 of the type shown is marketed by Fenwal, Mass. Under the tradename 111-202CAK-BD1. Leads 96 and 98
Consists of # 36 AWG signal wiring Cu + clad steel (heavy insulation).

The casting resin 100 seals the thermistor 94 and the lead wires 96 and 98 in the electrode well. Insulation coating 102 provides sealed leads 96 and 9
8 is also shielded. At the same time, resin 100 and coating 1
02 electrically insulates the thermistor 94 from the surrounding ablation electrode 16.

The casting resin 100 and the insulating coating 102 can be formed using various materials. In the illustrated embodiment, the loctite adhesive is a casting resin 1
Function as 00, but cyanoacrylate adhesive or RTV adhesive or the like may also be used. The coating 102 comprises a polyimide material, but other conventional electrically insulating materials may also be used.

In the illustrated embodiment, the thermal insulation means 8
8 has a tube 104 that encloses the sealed thermistor 94 and leads 96 and 98. The heat insulating tube 104 itself is adhered to the inner wall of the well 90.

The heat insulating material of the tube 104 can vary. In the illustrated embodiment, it is a polyimide material having walls about 0.003 inches thick. Other heat insulating materials such as mylar or kapton may also be used.

Leads 96 and 98 for thermistor 94 extend from electrode well 90 through guide tube 22 and into catheter handle 20. There, the leads 96 and 98 are electrically coupled to the cable 28 extending from the handle 20. A cable plug (not shown) connects to the generator 12 and transmits the signal from the thermistor 94 to the third monitor means 82.

FIGS. 7A to 7C show the temperature sensing means 84.
7 illustrates another embodiment of an ablation electrode 16 having an array of. At least one, and preferably all of the temperature sensing means 84, are thermally isolated from the ablation electrode 16 as shown in Figures 6 (a)-(c).

As shown in FIGS. 7A to 7C, the ablation electrode 16 in the example having a large number of arrays has an internal core well 106. 5 branch wells 1
08A-108E extend from the core well 106.
The branch wells 108A to 108E are open on the surface of the ablation electrode 16. One branch well 108A
A single temperature sensing means 84 shown in Figures 6 (a)-(c).
Similarly to, the ablation electrode 16 is open at the tip. The other four branch wells 108B-108E extend at an angle from the core well 106 at an arcuate spacing of 45 degrees. Four branch wells 108B-108
E opens on the side surface of the ablation electrode 16 and surrounds the tip well branch 108A.

One temperature sensing means 84 occupies each branch well 108A-108E. In the preferred embodiment shown, thermal isolation means 88 includes each temperature sensing means 84 with an associated branch well 108A-108.
It is thermally isolated from the inner surface of E and the rest of the ablation electrode 16.

Similar to the embodiment shown in FIGS. 6 (a)-(c), each temperature sensing means 84 comprises a small bead thermistor 94 having two associated leads 96 and 98. The temperature sensitive end of the thermistor 94 is exposed at the tip of the ablation electrode 16 for multiple contact with tissue. The associated leads 96 and 98 are bundled within the central core well 106 and extend through the guide tube 22 to the handle 20.

Similar to the embodiment shown in FIGS. 6A to 6C, the casting resin 100 seals each thermistor 94 and its lead wires 96 and 98 in the associated branch well. There is. The insulating coating 102 similarly shields the sealed leads 96 and 98. Along with that
The resin 100 and coating 102 electrically insulate each thermistor 94 from the surrounding ablation electrode 16.

Similar to the embodiment shown in FIGS. 6 (a)-(c), the heat insulating tube 104 encloses each electrically sealed thermistor 94 and its leads 96 and 98. Further, as in the embodiment shown in FIGS. 6A to 6C, an adhesive bond each heat insulating tube 104 to the inner wall of each branch well 108A to 108E.

FIGS. 8A to 8C show still another embodiment of the ablation electrode 16 having a large number of temperature sensing means 84.

In the structure shown in FIGS. 8A to 8C, the ablation electrode 16 has a front electrode portion 110 and a rear electrode portion 112. The front electrode part 110 and the rear electrode part 112 are generally spherical in shape.

The electrically and thermally insulating sleeve 114 separates the front electrode portion 110 and the rear electrode portion 112. The sleeve 114 is generally cylindrical in shape. The resulting "peanut" type is well suited for use within the valve portion of the heart.

In the illustrated embodiment, the front electrode part 1
10 and the rear electrode part 112 are made of platinum. The sleeve 114 is made of polysulfone material.

A number of temperature sensing means 84 occupy each surface of the front and rear electrode portions 110 and 112. At least one, and preferably all of the temperature sensing means 84 are thermally isolated from the body around the associated electrode portions 110 and 112.

Each electrode portion 110 and 112 has an internal core well 116 and a branch well 118 that are open at the surface of the associated electrode portion 110 and 112. A temperature sensing means 84 occupies each well branch. In the preferred embodiment shown, the thermal isolation means 88 similarly includes each temperature sensing means 84 associated with the inner surface of the associated branch well 116 and 118 and the electrode portions 110 and 1.
Thermally separate from the rest of 12.

Similar to the embodiment shown in FIGS. 6 (a)-(c), each temperature sensing means 84 has a small bead thermistor 94 having two associated leads 96 and 98. The temperature-sensing end of the thermistor 94 has associated electrode portions 110 and 11 for contacting tissue at multiple locations.
It is exposed on the surface of 2. Associated leads 96 and 9
8 are bundled in central core well 116 and extend through guide tube 22 to handle 20.

Similar to the above-mentioned embodiment, the casting resin 100 is used.
Seals each thermistor 94 and its leads 96 and 98 within the associated branch wells 116 and 118. In addition, as in the above-described embodiment, the heat insulating tube 10
4 encloses each electrically sealed thermistor 94 and its leads 96 and 98. An adhesive adheres the thermal isolation tube 104 to the inner wall of each branch well 116 and 118. Of course, the number and configuration of possible arrays of multiple temperature sensing means 84 can vary from the particular structure shown in FIGS. 6, 7 and 8. For example, one or more temperature sensing means 84 may occupy the side below the tip of the ablation electrode 16.
The branch wells carrying the temperature sensing means 84 can also extend from the central well at various angles, acute angles, obtuse angles or right angles. Not all temperature sensing means 84 need be separated from the electrodes 16, but preferably all are separated.

As shown in FIG. 5, the third monitor means 82.
Can perform different display and control functions depending on the sensed temperature conditions according to different predetermined criteria.

Preferably, the third monitor means 82 not only responds to the sensed absolute terms of tissue temperature, but also records changes in tissue temperature over time and functions to respond to these changes. To do.

In the illustrated embodiment, the third monitor means 82 has a control output 120 for each temperature sensing means 84 provided on the associated ablation electrode 16.

Leads 96 and 98 for each thermistor 94 provide an input for a control output 120. Alternatively, when the ablation electrode 16 is provided with a large number of thermistors 94, the number of lead wires 96 and 98 that cross the guide tube 22 depends on the integrated circuit for multiplexing the input signal of the thermistor 94. This can be reduced by providing 122 in the third monitor means 82.

In the illustrated embodiment, the third monitoring means 82 for each array group of thermistors 94 during the user-defined period (once in the illustrated embodiment, approximately once every 0.01 seconds). A converter 124 for determining the average temperature is provided. Since the embodiment shown in FIGS. 6A to 6C includes one thermistor 94, the input signal and the average are the same.

The embodiment shown in FIGS. 7A to 7C is
Five thermistors 94 collected at the tip of the ablation electrode 16
It has a single array group. For this array, the converter adds the individual input signals and divides by 5.

The embodiment shown in FIGS. 8 (a)-(c) is
Two array groups are provided, one having five thermistors 94 on the front electrode portion 110 and the other having four thermistors 94 on the rear electrode portion 112. The converter 124 adds the input signals of each array group in each array group to generate the thermistor 94.
Divide by the relevant number of. Accordingly, the front electrode unit 110
And the average of the rear electrode portion 112 are obtained.

The third monitor means 82 has an analog-to-digital converter 126. The converter 126 digitizes the sensed temperature average (s) for the device 10.

The converter 126 also digitizes the value of the calibration resistor 134. The thermistor resistance value is divided by the calibration resistance value to obtain a standardized resistance for the thermistor 94. This value is an input to a read-only memory (ROM) 136 (see FIG. 5 (b)) that has stored thermistor temperature data. Since the output of the ROM 136 is the actually measured tissue temperature (unit: Celsius), the deviation of the nominal resistance of the thermistor 94 is considered.

Although not shown, a large number of thermistors 9
The embodiment with 4 has the same number of calibration resistors 134, one for each thermistor 94.

The digital output or outputs of the converter can be used to display the measurement results. In the illustrated embodiment, the device 10 includes a third digital display 128 on the generator 12 to indicate to the user the average sensed temperature.

When the "peanut" type electrodes shown in FIGS. 8 (a)-(c) are used, the device 10 comprises separate display devices for the front and rear electrode portions 110 and 112.

The digital output or outputs of converter 126 are also used for control operations of generator 12. Preferably, the temperature control signal of the third monitor means 82 is also used to further improve the functions of the above-mentioned first and second monitor means 38 and 76.

In the illustrated embodiment, the device 10 comprises:
To control the radio frequency power at the ablation electrode 16, the digitized temperature output is used in a feedback loop that maintains the radio frequency output voltage within a desired range or constant. By controlling the power delivered by the generator 12 based on temperature, the physician can control the amount of damage produced.

For this purpose, the device 10 comprises an input device 130 for the user to enter the desired operating value for the tissue temperature.

When the tissue temperature is within the predetermined range but deviates by a predetermined amount within the range, the third monitor means 82
The control signal for increasing or decreasing the power output is generated without interruption. The control signal reduces the power output when the tissue temperature increases. The control signal increases the power output when the tissue temperature decreases. If the measured tissue temperature is outside the predetermined range, the third monitor means 82 generates a command signal to shut off the power to the ablation electrode 16. A typical setting range for tissue temperature for ablation of the heart is considered to be about 40 to 100 degrees Celsius.

If the temperature begins to fall within the set range and goes out of that range over time, the most probable cause is coagulation of blood on the ablation electrode 16 and the ablation electrode 1
6 withdrawal and cleaning is required. An abrupt change in tissue temperature outside the set range indicates a shift in the position of the ablation electrode 16, requiring repositioning of the ablation electrode 16.
The device 10 preferably includes a flashing light and an alarm sound (not shown) to alert the user when these temperature conditions occur.

As mentioned above, the device 10 according to the present invention can provide precise control over the ablation procedure.
The actual phase sensitive power monitoring and control is performed by the ablation electrode 16
Ensure effective transmission of radio waves to. Tissue impedance and tissue temperature monitoring and control, either individually or in combination, set physiological safety limits in terms of damage magnitude and coagulation detection. Monitoring and controlling tissue impedance and / or tissue temperature also provides information regarding the orientation of the ablation electrode 16.

[0130]

The radiofrequency ablation device according to the present invention enables the tissue ablation procedure to be performed accurately and safely.

The actual phase-sensitive power monitoring means and the control means (ablation electrode means) that functions based on the phase-sensitive power signal transmit the power transmitted to the electrode means for radiating radio frequency energy at the ablation site throughout the tissue ablation procedure. Allows precise control.

The means for monitoring the tissue impedance and the temperature of the tissue and the control means operating on the basis of the signals obtained by these means, in order to ensure the physiological safety of the size of the injury and the coagulation of blood Allows you to set limits. Tissue impedance and tissue temperature monitoring and control means also provide information regarding the orientation of the ablation electrode means.

[Brief description of drawings]

FIG. 1 is a perspective view of an apparatus for ablating tissue embodying features of the present invention.

2 is a schematic diagram showing a generator and associated monitor and control circuitry for the apparatus of FIG. 1. FIG.

3 is a schematic diagram showing a power monitor and control circuit for the apparatus of FIG.

4 is a schematic diagram of a tissue impedance monitor and control circuit for the device of FIG.

5 (a) and 5 (b) are schematic diagrams showing a tissue temperature monitor and control circuit for the device of FIG.

6 (a)-(c) show electrodes that may be used with a device to measure tissue temperature, the electrodes having thermally isolated temperature sensing elements.

7 (a)-(c) are diagrams illustrating electrodes that may be used with a device to measure tissue temperature, the electrodes having a plurality of thermally-insulated temperature sensing elements. .

8 (a) -8 (c) are electrodes that may be used with a device to measure tissue temperature, having a spatial shape as used in a heart valve, and thermal FIG. 6 is a diagram showing an electrode having a plurality of temperature sensing elements insulated from each other.

[Explanation of symbols]

 10 Radiofrequency ablation device 12 Radiofrequency generator 14 Catheter 16 Radiofrequency emission tip electrode (ablation electrode) 18 Indifferent electrode (skin patch electrode) 30 Radiofrequency power supply source 40 Current monitoring means 42 Voltage monitoring means 50 Current sensing transformer 54 voltage sensing transformer 70 power control means 74 phase shift comparator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Roger A. Stern United States California 95014, Cupertino, Palo Vista Road 10418

Claims (19)

[Claims] 1. A device for ablating tissue using radiofrequency energy, the source of radiofrequency energy being electrically connected to the source and radiating radiofrequency energy at the ablation site. For measuring the radio frequency current delivered to the electrode means and generating a measured radio frequency current signal, and measuring the radio frequency voltage at the electrode means for measuring the measured radio frequency. Voltage monitor means for generating a wave voltage signal, and a power monitor for multiplying the measured current signal by the measured voltage signal to obtain a phase sensitive power signal representative of the actual phase sensitive power transmitted to the electrode means. An apparatus comprising means and control means for performing a function based on the actual power signal. 2. The apparatus of claim 1 wherein said control means comprises display means for indicating the value of said phase sensitive power signal in a user readable format. 3. The apparatus of claim 1, wherein the control means comprises feedback means for controlling the voltage output of the source based on the phase sensitive power signal. 4. The feedback means includes register means for storing a desired amount of phase sensitive power, the desired amount of phase sensitive power in the register means, and the phase sensitive generated by the power monitor means. 2. The apparatus of claim 1 including comparator means for comparing the power signal to generate a shift signal and command means for changing the output voltage of the supply means in response to the shift signal. 5. The commanding means changes the output voltage of the source to maintain a predetermined minimum deviation signal.
The device according to. 6. Means for obtaining a root mean squared current signal based on the measured radio frequency current signal, and means for finding a root mean squared voltage signal based on the measured radio wave voltage signal, Means for multiplying the root mean squared current signal by the root mean squared voltage signal to obtain a root mean squared power signal representing apparent power transmitted to the electrode means; and the root mean squared power signal, Comparing the phase sensitive power signal generated by the power monitor means and indicating a phase shift between the measured radio frequency voltage signal and the measured radio frequency current signal at the electrode means. The device according to claim 1, further comprising a phase shift detection unit having a unit for generating a signal and a phase shift control unit for performing a function based on the phase shift deviation signal. . 7. The apparatus according to claim 6, wherein said phase shift control means interrupts conduction of radio frequency energy when said phase shift deviation signal exceeds a predetermined value. 8. The apparatus according to claim 6, wherein the phase shift control means generates a warning signal when the phase shift deviation signal exceeds a predetermined value. 9. The control means has a feedback means for controlling the voltage output of the supply source based on the phase sensitive power signal when the phase shift deviation signal remains within a predetermined range. The device according to claim 6. 10. The apparatus of claim 9, wherein the feedback means reduces the output voltage of the source when the phase shift signal increases beyond a predetermined range. 11. The apparatus of claim 10 wherein said feedback means interrupts power to said electrode means when said phase shift signal exceeds a predetermined maximum value. 12. Means for obtaining a root mean squared current signal based on the measured radio frequency current signal, and means for finding a root mean squared voltage signal based on the measured radio frequency voltage signal. A means for dividing the root-mean-squared voltage signal by the root-mean-squared current signal to obtain a measured tissue impedance signal, and impedance control means for performing a function based on the measured tissue impedance signal. The device of claim 1 further comprising a tissue impedance monitoring means for performing. 13. The apparatus of claim 12, wherein the impedance control means calculates the change in the measured tissue impedance signal during a selected interval and generates a control signal based on a predetermined criterion. 14. The apparatus of claim 12, wherein the impedance control means generates a command signal that interrupts energy to the electrode means when the measured tissue impedance signal is outside a predetermined range. 15. The device of claim 12, wherein the predetermined range is about 50 to 300 ohms. 16. The impedance control means, wherein the measured tissue impedance signal begins to fall into a predetermined range and increases over time to indicate coagulation of blood on the electrode means. 13. The device according to claim 12, which generates a control signal. 17. The impedance control means generates a control signal in response to an increase in the measured tissue impedance signal by more than a predetermined amount indicative of the onset of coagulation or a sudden shift in the position of the electrode means. The device according to claim 12. 18. A control signal when the impedance control means exceeds a predetermined maximum amount of the measured tissue impedance signal, indicating poor skin contact to the electrode means or an electrical problem in the device. 13. The device of claim 12, which produces 19. The apparatus of claim 12, wherein the impedance control signal comprises a display device that indicates the value of the measured tissue impedance signal in a user-readable format.