JPH0336546B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to an implantable defibrillator that defibrillates a patient's heart, and more particularly, the present invention relates to an implantable defibrillator that defibrillates a patient's heart, and in particular, to an implantable defibrillator that defibrillates a patient's heart. The present invention relates to a defibrillator using telemetry means for transmitting information representing the status and operation of the defibrillator. BACKGROUND ART In recent years, considerable progress has been made in the development of defibrillation techniques that effectively defibrillate various malfunctions and arrhythmias of the heart. Efforts have led to the development of implantable standby electronic defibrillators, which are connected to the heart and only respond when an abnormal heart rhythm is detected. Sufficient energy is applied to the heart through the electrodes in the body, providing a negative effect on the heart and allowing it to return to its normal heart rhythm. Additionally, much research effort has been directed toward developing techniques to reliably monitor cardiac activity to determine whether defibrillation is necessary. Such techniques include determining the presence of fibrillation or monitoring ventricular activity rate based on a probability density function (PDF). A system using this PDF technology statistically compares the location of each point on a cardiac waveform with the expected location of each point on a normal waveform. When the waveform becomes irregular, as measured by the probability density function, abnormality in cardiac function is suggested. This technique is disclosed in co-owned US Pat. Nos. 4,184,493 and 4,202,340 to Langer et al. As disclosed in co-owned Patent Application No. 175670 filed by Langer et al. on August 5, 1980, recent systems use PDF technology to determine the presence or absence of heart rhythm abnormalities, as well as to determine heart rate. Sensing circuitry is used to detect ventricular fibrillation and fast tachycardia (the latter indicated by a heart rate above a predetermined minimum threshold) and normal heart rhythm or slow tachycardia (the latter indicated by a heart rate above a predetermined minimum threshold). (indicated by falling below a predetermined minimum threshold). Further, research in this field has led to the development of heart rate detection systems that accurately measure heart rate for a wide variety of different shapes of electrocardiogram (ECG) signals. One such system was introduced in May 1981.
Joint patent application filed by Imran et al. on the 15th
Disclosed in No. 263910. Despite these efforts and the level of technology achieved in known devices, there are potential problems and drawbacks to such devices. Such issues include: (1) Since it is important to be able to detect R-waves with maximum accuracy for the proper and efficient operation of implantable defibrillators, there is a continuing need to improve R-wave detection. is necessary. (2) Sensing electrodes that monitor cardiac activity can sometimes become misaligned, thus impairing or completely attenuating the sensed ventricular beat signal, thereby triggering defibrillator activation. The cycle becomes irregular or unreliable. (3) Once implanted, there is currently no means to determine the status (operating or not) or other operational status or functionality of an implanted defibrillator. (4) Since the defibrillator is configured to operate automatically when necessary, it maintains a running count of the number of defibrillation pulses generated by the defibrillator and is It would be advantageous to provide a means for transmitting stored count information and other status information without the need for invasive surgery. (5) Defibrillators have serious problems when their external high-voltage electrodes are shunted, so these implantable defibrillators have short circuits to protect sensitive internal circuits and electrodes. It is considered convenient to provide a prevention circuit (shunt prevention circuit) function. (6) Since there is a danger in using a general defibrillation device that applies a shock asynchronously to the R wave in response to an increasingly rapid arrhythmia, it is preferable to perform defibrillation in synchronization with the R wave. In view of the foregoing, it is an object of the present invention to provide an implantable defibrillator having improved sensing means for detecting the occurrence of abnormal heart rhythms and automatically generating defibrillation pulses in response thereto. That is, to provide cardioverter. Another object of the present invention is to provide an improved defibrillator or cardioversion system that can determine whether heart rate sensing electrodes are properly placed without invasive surgery. It is. Yet another object of the present invention is to provide various status information, when interrogated by extracorporeal means, indicating whether the electrodes are properly positioned relative to the heart and what the operating status of the electrodes is. An object of the present invention is to provide an implantable defibrillator or cardioverter capable of transmitting the following information. Yet another object of the present invention is to provide an implantable cardioverter defibrillation device or cardioversion system in which telemetry information transmitted outside the patient's body is encoded and transmitted by circuitry within the implanted device. It is. Yet another object of the present invention is to provide an implantable cardioversion device or cardioversion system that prevents external defibrillation pulses from being shorted between the defibrillation electrodes. . Yet another object of the present invention is to provide an implantable defibrillator or cardioversion system with means for reducing the risk of accelerated arrhythmia in a patient during cardioversion. DISCLOSURE OF THE INVENTION In accordance with embodiments of the present invention that achieve the above and other objects, a defibrillation device includes an implantable defibrillator and an implantable defibrillator that changes the state of the implanted defibrillator and/or or an extracorporeal non-invasive controller/monitor for retrieving status information. The implantable defibrillator consists of a high-voltage inverter circuit with shunt prevention means, a PDF circuit and a heart rate analysis circuit that each detect abnormal heart rhythms and actuate the high-voltage inverter circuit together. a combination body, a series of electrodes connected to the heart, a bipolar sensing electrode connected to the heart rate analysis circuit to sense ventricular beat signals, and a high-energy defibrillation pulse and a PDF. a series of electrodes including a high voltage pulsing electrode connected to the high voltage inverter circuit and the PDF circuit to respectively provide an information signal; and counting the number of defibrillation pulses emitted by the inverter circuit. a piezoelectric speaker connected to the wall of the case surrounding the defibrillator circuit that generates an audible sound indicating the status of the defibrillator, and a piezoelectric speaker that responds to an external magnet. telemetry means for changing the state of the defibrillator (activated or inactive) and transmitting encoded status information of the defibrillator (such as pulse count and capacitor charge time information); Enables internal test functions to be performed and enables the piezoelectric speaker to generate an audible tone that non-invasively indicates proper placement of bipolar sensing electrodes and defibrillator status. It is equipped with means to enable The external controller/monitor is connected to a hand-held magnet that initiates the above functions when properly positioned relative to a reed switch inside the implanted defibrillator. The device includes an RF receiving circuit including a demodulator that decodes certain status information transmitted as electromagnetic waves and displays it on a display device. The invention is particularly pointed out in the claims. The above and further objects and advantages of the present invention will be understood from the following description of illustrative embodiments of the invention with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 depicts in functional block diagram form the intracorporeal and extracorporeal components of the defibrillation system of the present invention. The implanted parts are in a metal case (not shown)
It constitutes a standby defibrillator that detects abnormalities in heart rhythm. In response to the detection of such heart rhythm abnormalities, the defibrillator delivers a series of defibrillation pulses (25 to 25) to the patient's heart 10.
30 joules) and then record the cumulative number of defibrillation pulses given in memory (eg, a counter). In the preferred embodiment, the defibrillator generates three 25 joule defibrillation pulses, followed by a 30 joule pulse if needed. After the first pulse, detect again and if there is still an arrhythmia, start charging,
A second pulse is applied at the end of the charging cycle. This pattern continues, if necessary, until a fourth high energy shot is applied. Thereafter, no further pulses can be given until at least 35 seconds of normal sinus rhythm is detected. The device is then ready to deliver yet another series of four shots. In the present invention, multiple electrodes are connected to the patient's heart and the defibrillation circuit. These electrodes transmit sensing information from the heart to the defibrillator and provide high energy defibrillation pulses from the defibrillator to the heart. These electrodes include a bipolar sensing electrode 18 placed in the right ventricle to sense electrical activity from ventricular contractions and a bipolar sensing electrode 18 adapted to sense electrical activity and provide a defibrillation pulse. It includes intercardiac sensing and high voltage application electrodes 20 and 22 for.
Electrode 20 is placed in the superior vena cava and patch electrode 22 is connected to the myocardium at the distal end of the heart. Electrode construction and circuit connections will be described in detail below, with particular reference to bipolar sensing electrodes 18 as they form part of the subject matter of the present invention. On the other hand, the external parts of this system include a demodulator/decoder circuit 12, which receives RF signals (high frequency signals).
and, in the preferred embodiment, decode the telemetry decoder transmitted as electromagnetic waves by the current-carrying conductors of the implanted defibrillation circuit. In addition, the display device 14 displays the charging time required to charge the high voltage energy storage capacitor in the defibrillator and cumulative pulse count information stored in the implanted defibrillator. do. As discussed below, the charging time is derived by detecting the RF signal emitted from the high voltage inverter coil within the inverter when the inverter is operating, while the pulse count information is It is derived by decoding the modulated transmission signal of the same RF signal, which is sometimes generated by a high voltage inverter. When the defibrillator is implanted subcutaneously, the reed switch 24 (housed in the defibrillator case) is approached and the ring-shaped magnet 21 is attached to the patient's skin.
By placing , one of the following three things will occur. First, the audio oscillator 50 is enabled to generate sound synchronously with the heartbeat when the defibrillator is activated, and continuously when the defibrillator is inactive. Make it. Second, the state flip-flop 26 changes state if the magnet is held in that position for more than a predetermined period of time (eg, 30 seconds).
Thirdly, when the defibrillator is in operation, the magnet 2
1, the defibrillator begins to receive telemetry data of pulse count information and capacitor charge time information. These operations will also be discussed in detail below. As mentioned above, another feature of implantable defibrillators is that they are reliable in detecting cardiac arrhythmias and are reliable in preventing inappropriate delivery of defibrillation pulses. To accomplish this, the implantable defibrillator uses a probability density function (PDF) analysis circuit 28 such as that disclosed in the aforementioned U.S. Patent Application No. 175,670, U.S. Patent No. 4,184,493, and U.S. Patent No. 4,202,340. It is equipped with Additionally, the implantable defibrillator includes a heart rate analysis and averaging circuit 30 that senses, analyzes and averages heart rate signals representative of ventricular contractions of the heart 10. When circuits 28 and 30 detect a heart rhythm abnormality, each of these circuits generates an enable signal that activates AND gate 32 to generate signal INVST, which is then output to the high voltage inverter. The control circuit 34 is activated and ready to deliver defibrillation pulses to the patient's heart. Each such pulse is delivered to the heart across electrodes 20 and 22. The application of defibrillation pulses will not occur unless circuit 34 is activated. To put circuit 34 into operation, ring magnet 21 is used to toggle state flip-flop 26, which generates an EN signal at its Q output and sends this signal to circuit 34. Then, the inverter/control circuit 34 is enabled. Additionally, a signal sent from heart rate circuit 30 via conductor 35 in synchronization with the generation of the ventricular contraction signal of heart 10 serves as a timing signal for circuit 34 such that the generation of defibrillation pulses is synchronized with the contraction of the ventricles. . When synchronized in this manner, the defibrillation pulses most efficiently defibrillate the heart 10, reducing the risk of accelerated arrhythmias. To track the number of defibrillation pulses applied, circuit 34 generates a CT pulse signal each time it generates a defibrillation pulse. This CT pulse signal is used by a pulse count circuit described later. Still referring to FIG. 1, a comparator 36 associated with heart rate circuit 30 sets a heart rate threshold at, for example, 160 beats/minute, at which heart rate circuit 30 passes through AND gate 32. In conjunction with the transmitted PDF output, an enable signal is generated that initiates operation of the high voltage inverter circuit 34. Heart rate analysis and averaging circuit 30 generates an analog signal RATE on conductor 31 having a magnitude representative of the ventricular heart rate and supplies this signal to one terminal of comparator 36. A signal RATE THRESHOLD is sent to the other terminal of comparator 36. During defibrillator manufacturing, the voltage level of signal RATE THRESHOLD is determined by comparator 36 and gate 32 when the ventricular heart rate, as indicated by the RATE signal, reaches a predetermined trigger level, such as 160 beats/minute. is set to energize. A digital pulse counter comprising a register 38 is responsive to the CT pulse signal generated by the inverter circuit 34, assuming that the heart is actually fibrillating and the inverter generates a defibrillation pulse. This counter therefore maintains a running count of the number of defibrillation pulses delivered. This count information can be transmitted as electromagnetic waves during a "magnetic test" to be described later, when requested. When the device is in operation, a magnetic test is initiated by momentarily placing ring-shaped magnet 21 against reed switch 24 and removing the magnet. In response, the inverter begins operation and a telemetry control signal from magnetic test logic 40 enables converter 39 to serialize the digital count information and transfer this series of data bits to the pulse width modulation circuit. 90, which frequency modulates the frequency of the high voltage inverter via a frequency modulator 92. When the inverter is in operation, an RF signal is generated by the inverter coil, which is detected external to the body by demodulator 12.
By demodulating the RF signal and detecting the RF frequency, the charging time of the storage capacitor (corresponding to the maximum time that the RF signal is present) is detected, and
A total number of defibrillation pulses delivered to the patient is detected. Demodulation circuit 12 is a general FM demodulator and detector. It is preferably placed within a few inches of the patient. After demodulation, circuit 12
displays the capacitor charge time, which indicates the status of the implanted battery, and displays the cumulative number of pulses delivered by the defibrillator. State indication and change Audio oscillator 50 and piezoelectric transducer 52
Several sounds generated by the device indicate the status of the implantable defibrillator. In the activated state, the state flip-flop 26 of FIG. and is periodically enabled. Thus, when magnet 21 is placed near reed switch 24, the generation of each ventricular beat pulse from heart rate circuit 30 momentarily energizes AND gate 48 and audio oscillator 50. (When reed switch 24 is closed by magnet 21, a low or "0" state signal is provided to inverter 46 and a "1" input is provided to AND gate 48.) At this time, oscillator 50
An audio speaker (piezoelectric transducer) 52 directly connected to the case of the implantable defibrillator is driven. Thus, while remaining activated, for example when the state flip-flop 26 provides its Q output, a sound synchronized with the heartbeat will be generated periodically. In the preferred embodiment, piezoelectric transducer 52 resonates at approximately 3000 Hz, which is audibly detected by a person within range of the sound produced by the transducer. Thus, the pulsed sound produced by the piezoelectric crystal 52 in synchronization with the heartbeat indicates that the bipolar electrode 18 is properly positioned within the patient's heart. On the other hand, if the state flip-flop 26 is inactive and, for example, no EN signal is generated, then
AND gate 44 is disabled and the flip-flop
Flop 26, via its output, provides a continuous activation enable signal to one input of AND gate 48. In the inactive state, reed switch 2
When the magnet 21 is placed near 4, the inverter 46
A continuous enable signal is provided to the other input of AND gate 48 via. As a result, oscillator 50 is driven continuously to generate a steady audible sound from piezoelectric transducer 52 at approximately 3000 Hz. Thus, a pulsed tone indicates that the defibrillator is activated and a continuous tone indicates that the defibrillator is not activated. If the bipolar sensing probe 18 is not properly positioned within the right ventricle when the device is in operation, no ventricular signal will be sensed and no sound will be generated. Therefore, the presence or absence of an audible tone indicates whether probe 18 is properly positioned relative to the right ventricle. The operating frequencies of the oscillator 50 and the piezoelectric transducer 52 are determined by the characteristics of the rigid case surrounding the defibrillation circuit so that the transducer 52 dissipates the least amount of energy for a given level of generated sound. selected substantially equal to the resonant frequency. The attachment of the piezoelectric crystal to the inner wall 51 of the implanted case is shown in FIG. In order to make the wall 51 of the case resonate effectively, a solid layer 53 of epoxy cement, such as an adhesive called Eccobond 24, is inserted between the surface of the wall 51 and the surface of the crystal 52 via an insulating tape 55. Works as an adhesive. Preferably, there are no cavities between the crystal and the wall in order to generate audible sound. Rather, wall 5
1 itself vibrates to produce sound. Switching the state of the defibrillator (via the state flip-flop 26) is accomplished by holding the magnet in position over the reed switch for a predetermined period of time - 30 seconds in the preferred embodiment. To switch states, the 30 second timer circuit 54 generates a CK signal;
This signal is activated when the magnet 21 is held in position for more than 30 seconds (reed switch 24 closed).
Toggle flop 26. Timer 54 is CK
Preferably, the trigger circuit includes an R-C charging network to generate the signal. Any suitable timer, such as a digital timer responsive to a reed switch, can be used as the delay timer. Also, when inactive, the status flip-flop 26
de-energizes all non-critical components of the defibrillator, reducing the amount of current drawn from the battery (not shown). Only the state switching circuit and the voice prompt circuit require power during the inactive state. Similarly, when activated, the EN signal enables an electronic switch (not shown) to power heart rate circuit 30 and PDF circuit 28. Heart rate analysis/averaging circuit 30 Figure 2 shows the heart rate analysis/averaging circuit 3 in Figure 1.
0 is a circuit diagram. As mentioned above, this circuit 3
0 senses right ventricular depolarization and in response generates an analog signal with a voltage level proportional to the average ventricular heart rate. In the circuit 30,
A pair of conductors 56 and 57 receive ventricular signals from bipolar sensing probe 18 . The ventricular beat signal is passed to a high pass filter 58, which attenuates signal components below a frequency of 30 Hz. Preamplifier 59 then amplifies the signal from the high pass filter. A high voltage protection circuit 55 is inserted between the electrode 18 and the high pass filter 58, which protects the circuit from the high voltages produced by the defibrillation pulse. Preamplifier 59 is connected to amplifier 66 which has an automatic gain controller (AGC) in its feedback circuit. This AGC attempts to maintain a constant output amplitude even if the input signal level changes.
It is known that the amplitude of the ECG input signal changes rapidly. A pulse shaping circuit comprising comparator 76 receives the gain controlled ventricular beat signal and generates a series of square wave pulses in response. Conveniently, the trigger pulse is generated by both positive and negative swings in the ventricular beat signal, so that the circuit 30 can be used for various patient-related events in which the ventricular signal is strong in either the positive or negative direction. or to characteristic signals derived from various locations in the ventricle where the bipolar sensing probe 18 is placed. For this and other reasons, circuit 30 is very reliable. The square wave pulse from comparator 76 triggers a one shot multivibrator 78 which generates another square wave pulse of fixed duration, preferably about 150 milliseconds. This time span represents the refractory time of the device. This 150
During the millisecond refractory time, the multivibrator 78
cannot be retriggered by other signals, such as T-waves, etc., until this time has elapsed. A signal REFRAC consisting of uniform width refractory pulses from multivibrator 78 is sent to averaging circuit 80 and AND gate 44 (FIG. 1). Additionally, the R-wave output signal is sent via line 35 to high voltage inverter control circuit 34 to synchronize the defibrillation pulses with the R-wave output (see FIGS. 1 and 3). resistance 82
and a capacitor 84.
0 is the signal from multivibrator 78
Integrate REFRAC. Circuit 80 is similar in its operation to a frequency-to-voltage converter. for example,
At 60 beats/min, the duty cycle of signal REFRAC is 15%. When integrated or averaged, circuit 80 calculates the
Generate RATE signal. When the heart rate increases, pulses of constant width occur frequently, so
The duty cycle of the REFRAC signal also increases,
When the circuit 80 integrates this, it generates a RATE signal of a corresponding magnitude. This RATE signal is output by comparator 36 (also shown in Figure 1).
Compared to the RATE THRESHOLD signal, this comparator generates an enable signal that activates AND gate 32. RATE of comparator 36
The THRESHOLD signal is selected such that the comparator generates an enable signal at a predetermined rate. Although not shown in FIG. 1, delay circuit 86 introduces a two second delay such that the input to delay circuit 86 is
The signal is passed to the AND gate 32 only when it is maintained for more than a second. This delay reduces the risk of detecting self-limiting short-lived arrhythmias. High-voltage inverter/control circuit The high-voltage inverter/control circuit 34 is shown in FIGS. 3, 4, and 6 together with the magnetic test logic circuit 40.
This is shown in detail in the figure. Referring first to FIG. 4, a high voltage inverter 200, also known as a DC-DC converter, is a common component well known in the field of implantable defibrillators. See, for example, US Pat. No. 4,164,946, which describes a DC-DC converter (device 30 of that patent). The high voltage inverter 200 charges an energy storage capacitor 202 within the body, which is charged to a predetermined level, and the SVC electrode 202 is charged to a predetermined level.
0 and patch electrode 22 to the patient's heart, or through test load resistor 212 under conditions described below. High voltage inverter 200
has an implanted coil (not shown) that emits an RF signal during operation of the inverter, ie, during charging time of the capacitor 202.
As explained below, this can be detected outside the patient's body.
It is RF radiation. EN from the above state flip-flop 26
When the high voltage inverter is enabled by the signal, the inverter 200 is ready to operate. The high voltage inverter 200 is an INVERTER
It starts operating when it receives a START signal, which can be either the INVST signal from the AND gate 32 as shown in FIG. 3 or the magnetic test logic circuit 40 (as shown in FIGS. 1 and 3). from)
It is initiated by receiving either the MGTST signal. The high voltage inverter begins operation and provides an INV RUNNING signal to the magnetic test logic circuit 40, as described below. The high voltage inverter continues to operate until the energy storage capacitor 202 is charged to its predetermined level. The time the high voltage inverter operates, that is, the time required for the high voltage inverter to charge the capacitor 202 is:
It is clear that this is an indication of the defibrillator's battery strength. (See discussion in US Pat. No. 4,164,946). Furthermore, during the charging time of the high voltage inverter, the RF radiation of the inverter coil is
It is frequency modulated to represent the number of inverter discharges between 0 and 22, and this information can be detected outside the patient's body by demodulator/decoder 12. Capacitor 202 is discharged through test load 212 based on whether a trigger pulse is received on test load SCR 204 via line 206 or a trigger signal is received between leads 208 to enable patient SCR 210. ,
Alternatively, a discharge occurs between patient electrodes 20 and 22. Line 206 and lead 208 are operated by a control circuit described below with respect to FIG. When SCR 204 is triggered by a pulse on line 206, capacitor 202 discharges across test load resistor 212, and when patient SCR 210 is activated by a signal on lead 208, capacitor 202 discharges across test load resistor 212. Discharge occurs across electrodes 20 and 22. When the capacitor discharges across the patient electrode, a count signal is provided to the CT which increments a counter 38 representing the number of discharges to the patient's heart, as shown in FIG. Similarly, as shown in FIG. 4, a pulse feedback signal is provided which is sent to the control circuitry shown in FIG. 3 to trigger the disconnect SCR 214 as described below. Patient SCR 210 is triggered by a signal sent through lead 208 and the shunt prevention circuit.
The shunt prevention circuit includes a miniature pulse transformer 216 connected to a patient SCR 210 to trigger the patient SCR 210 in response to a trigger input across lead 208. The trigger input signal is routed to the primary winding of this transformer 216, which actuates the patient SCR 210 so that high voltage defibrillation pulses can be delivered to the SVC and patch electrodes 20, 22. do. Such circuits ensure that when an external defibrillation voltage is applied to the patient's heart to which the implanted device is connected, the external defibrillation voltage is not sent to the implanted device. , especially avoiding the disadvantage of not being fed to a high voltage inverter. Coupling through the transformer eliminates a low impedance path to ground. Cut SCR 214 is activated by a signal on line 216, as shown in FIGS. 3 and 4. The purpose of cutting SCR is as follows. When the capacitor 202 discharges across the implanted electrode, the discharge has an exponentially decaying waveform. When the waveform decays to a certain voltage, the disconnection occurs.
SCR 214 fires and cuts this decaying pulse. Preferably, this predetermined decay point is approximately 2/3 of the point that a fully damped pulse would take. The trigger signal to the circuit of FIG. 4 is provided by an inverter control circuit associated with magnetic test logic 40, as shown in FIG.
As shown in FIG. 3, the INVST signal received from the AND gate 32 or the MGTST signal received from the magnetic test logic circuit 40 is applied to the OR gate 32.
18, this OR gate generates an INVERTER START signal that initiates operation of the high voltage inverter that causes charging capacitor 202 to charge. Assuming that the need for defibrillation arises and the INVST signal is generated from the AND gate 32,
Such a signal initiates operation of the inverter via OR gate 218, which initiates operation of the patient flip-flop 2.
Set 20. The output of the patient flip-flop is sent to AND gate 222. A second input to AND gate 222 receives the R-wave detection output signal from heart rate analysis circuit 30 shown in FIG. 1 (via line 35). and gate 222
The third input of
Connected to the high voltage inverter to receive the INV RUNNING signal. During times when the inverter is operating, the third input of AND gate 222 is low and the output of AND gate 222 is low. When the inverter stops operating, ie, when the defibrillator capacitor is fully charged, the output of the inverter logic element 224 goes high. Therefore, when the next R-wave input is sent to AND gate 222, it passes through appropriate RC pulse shaping network 226 and buffer 228 to transistor 2.
A pulse is generated to 30. transistor 230
is activated and a patient trigger pulse is sent to lead 208. As previously discussed, upon receipt of a patient trigger pulse via lead 208, patient SCR 210 is fired, as shown in FIG. 4, and capacitor 202 is discharged across the electrodes connected to the patient's heart. This discharge provides a count CT pulse, which via OR gate 232 resets patient flip-flop 220. When patient SCR 210 is triggered, capacitor 202 discharges to provide an exponentially decaying high voltage pulse between electrodes connected to the patient's heart. This exponentially decaying pulse is fed back to threshold comparator 234 via a pulse feedback terminal. When this exponentially decaying pulse feedback signal falls to a predetermined reference level applied to the negative input terminal of comparator 234, the comparator produces an output, which is inverted by inverter 236. The lead 21 is shaped by the pulse shaping circuitry 238.
A pulse is applied to 6 to fire the disconnect SCR 214 as shown in FIG. When the cut SCR 214 is fired, the exponentially decaying pulse across the electrodes 20, 22 is cut. This is done because it is undesirable to require the pulse to decay exponentially to a zero level. The operation of the test logic circuit 40 by the magnet and the triggering of the test load SCR 204 will be described below. The magnetic test logic circuit is activated when AND gate 240 is energized.
AND gate 240 is energized when the defibrillator is enabled, ie, when it receives the EN signal from status flip-flop 26, and when magnet 21 is removed from reed switch 24, a positive high level signal is applied to the AND gate. 240. That is, the magnet 21
When the reed switch 24 is brought near the reed switch 24, this closes the reed switch contact.
AND gate 240 is provided with a negative zero input. When the magnet is removed, thereby opening reed switch 24, the input from the reed switch to AND gate 240 goes high, energizing AND gate 240. Note that magnet 21 must be removed from the vicinity of reed switch 24 within 30 seconds in order to begin the magnetic test. If the magnet 21 is placed near the reed switch 24 for more than 30 seconds, the state flip-flop 26 will be disabled and the AND gate 240 will be removed from the state flip-flop 26.
The input sent to is low, thus preventing AND gate 240 from energizing. When AND gate 240 is activated, delay flip-flop 242 is set, which is passed through OR gate 218 to inverter and control circuit 34.
The MGTST signal is applied, which starts the operation of the inverter. Furthermore, flip-flop 2
The output of 42 sets a magnetic test flip-flop 244. Once magnetic test flip-flop 244 is set, AND gate 2 is turned on after a short delay by delay element 246.
An input signal is issued to 48. and gate 24
The second input to 8 is connected to the INV RUNNING line via an inverter logic element 224. Once the inverter has finished operating, indicating that internal capacitor 202 is fully charged, the second input to AND gate 248 goes high, energizing AND gate 248. and gate 248
The output pulse from the test load SCR 204 is applied to the test load SCR trigger line 206 through a pulse shaping/buffer circuit, and the test load SCR 204 is fired. The capacitor then discharges across the test load resistor 212. When magnetic test flip-flop 244 is set and its Q output goes high, the Q output is sent to OR gate 232 to hold patient flip-flop 220 in reset. Therefore, during the magnetic test condition, the patient flip-flop is inhibited from operating and no defibrillation pulses can be delivered to the patient's heart. During magnetic testing, when magnetic test flip-flop 244 is set, telemetry control AND gate 250 is enabled during times when the inverter is operating. This sends a telemetry control signal from magnetic test logic 40, which is sent to an 8-bit parallel-to-serial converter 39 as shown in FIG. As mentioned above, the number of defibrillation shots administered to the patient is represented by CT signals, and these signals are sent to counter 38 as shown in FIG. When the telemetry control signal is applied from the magnetic test logic circuit 40, the counter 38
The contents of are sent to an 8-bit parallel-to-serial converter 39. The serial data bits from converter 39 are sent to pulse width modulation circuit 90 which provides a pulse width modulated signal to inverter frequency modulator 92. This inverter frequency modulator 92
frequency modulates the RF signal emitted by the inverter coil during the time the inverter is operating. This frequency modulated information can be detected outside the patient's body by an external demodulator/decoder 12, which demodulates the frequency modulated signal to determine the number of defibrillation pulses counted. Display. Furthermore, by detecting the time during which the inverter coil generates the high frequency, the charging time of the capacitor of the defibrillator is measured. reading and converting telemetry information from the counter 38;
The time required to pulse width modulate and modulate at the inverter frequency is approximately 2 seconds, while the time required to charge the high voltage capacitor contained within the high voltage inverter and control circuit is 5 to 6 seconds. Demodulator/decoder 12 and display device 14 are external devices suitable for demodulating, decoding and displaying the transmitted information. Now, referring to FIG. 6, the 4 count holding circuit will be described. As mentioned above, the 4 count hold circuit inhibits the inverter until 35 seconds of normal sinus rhythm is detected after 4 defibrillation pulses have been delivered to the patient. The 4-count holding circuit includes a 4-stage shift register, after which an inverter inhibit line is connected to the fourth stage Q3. When defibrillation pulses are detected via the CT input, each CT pulse representing a defibrillation shot is counted. When 4 counts are received, an inverter inhibit output is given, inhibiting the high voltage inverter. Each CT pulse passes through an OR gate 302 and a 35 second delay timer 30.
It is also sent to 4. Upon receiving each CT input, 35
A second delay timer is started. After 4 CT pulses, still INVST to OR gate 302
If an input is sent indicating that the patient still requires defibrillation, the 35 second delay timer continues to run. Only when normal sinus rhythm is detected by the absence of the INVST signal does the 35 second delay timer reset the shift register 300 and allow the high voltage inverter to operate. Bipolar Sensing Electrode 18 FIG. 5 shows the bipolar sensing electrode 1 shown in FIG.
8 is shown in detail. This electrode 18 is implanted in the right ventricle and senses the relatively weak electrical signals generated by ventricular contraction, as described above. R
This signal, known as a wave, then
It is supplied to the heart rate analysis/averaging circuit 30 shown in the figure. The electrode 18 includes a first wire lead 301 and a second wire lead 302 spaced apart from the lead 301. Lead 301 is in electrical communication with a conductive distal tip 303 compressed around it, while lead 302 is in electrical communication with a conductive ring electrode 304 in contact therewith. 304 surrounds a flexible insulating elastomer 306. In a preferred embodiment, the spacing between conductive elements 303 and 304 is about 1 cm. Lead coils 307 and 308 are wound around wire leads 301 and 302 to surround them.
Lead coils 307, 308 are individually enclosed within a two-lumen tube 305 and extend to a plug element 310 that is inserted into an implantable device. Lead coil 3
08 further includes a medical grade silicone surrounding tube near its distal end. Strictly speaking, the structure of the bipolar electrode 18 is different from that described above, the important feature of which is the spacing between the far end tip electrode 303 and the ring electrode 304. Furthermore, these two electrodes are connected to one part of the integral structure.
It may also be a separate electrode, such as a corkscrew or needle type electrode that does not form a part. Chip electrode 303
Polymorphic ventricular frequency It has been found that a signal with a fast rise time is obtained which is useful for counting heart rate during particularly disruptive cardiac arrhythmias such as pulse and ventricular fibrillation. “Fibrillation”, “cardioversion” used here,
“Defibrillation”, “defibrillator” and “cardioverta”
The term refers to any fatal arrhythmia that can be restored to its normal rhythm by applying a high voltage shock, as well as to restoring such an arrhythmia to its normal rhythm, e.g. Fatal tachycardia with high heart rate should be considered equivalent to "fibrillation" as used herein. Illustrative embodiments of the invention have been described above that accomplish the foregoing objects. It will be understood that many changes and modifications may be made without departing from the scope of the claims.

[Brief explanation of drawings]

FIG. 1 is a simple block diagram showing the internal and external components of the defibrillation system according to the present invention, FIG. 2 is a detailed circuit diagram of the heart rate analysis/averaging circuit of FIG. 1, and FIG. Figure 1 is a detailed circuit diagram of the magnetic test logic and inverter control circuit, Figure 4 is a partial circuit diagram of the inverter control circuit of Figure 1, and Figure 5 is a detailed circuit diagram of the inverter control circuit of Figure 1 that senses electrical signals from the patient's heart. 6 shows the four-count holding circuit of FIG. 1; and FIG. 7 shows the attachment arrangement of the piezoelectric crystal to the wall of the case surrounding the implant of FIG. 1. FIG. 12... Demodulator/decoder, 14... Display device, 18... Bipolar sensing electrode, 20, 22...
Electrode, 21... Magnet, 24... Reed switch,
26...state flip-flop, 28...
PDF analysis circuit, 30... Heart rate analysis/averaging circuit, 34... High voltage inverter/control circuit, 36...
...Comparator, 38...Register, 39...Converter, 40...Test logic circuit using magnet, 50...
...Audio oscillator, 90...Pulse width modulation circuit, 92
...Frequency modulator.

Claims (1)

[Scope of Claims] 1. An implantable defibrillation device for automatically removing cardiac fibrillation in a patient, comprising: detection means for detecting cardiac fibrillation; and at least one device responsive to the detection means. defibrillation means for generating and applying high-energy defibrillation pulses to the heart; counting means for maintaining pulse count information in response to the defibrillation means; and a telemetry device connected to the counting means. Telemetry means for transmitting an information signal representing the pulse count information outside the patient's body in response to a control signal, and control means for generating the telemetry control signal in response to an actuation signal generated outside the patient's body. The defibrillation means comprises a storage capacitor and high voltage inverter means for charging the storage capacitor, the high voltage inverter means configured to generate a radio frequency (RF) signal detectable outside the patient's body while charging the storage capacitor. ) the telemetry means comprises frequency modulation means for frequency modulating the high frequency signal emitted by the high voltage inverter means according to pulse count information held in the counting means. A device characterized by: 2. The counting means comprises register means for counting the number of defibrillation pulses applied to the patient's heart, and the telemetry means is for converting the number of pulses held in the register means into a series of pulses. serial conversion means connected to said register means, said telemetry means further comprising pulse width modulation means for pulse width modulating a series of pulses from said serial conversion means, said pulse width modulation means being connected to said frequency 2. The apparatus of claim 1, wherein the frequency modulation means is connected to modulation means, and wherein the frequency modulation means frequency modulates the high frequency signal based on a pulse width modulation signal from the pulse width modulation means. 3. The apparatus according to claim 2, wherein the serial conversion means is activated upon receiving a telemetry control signal from the control means. 4. The control means further provides a test signal to the high voltage inverter means to initiate operation of the high voltage inverter means in response to the activation signal;
The control means further includes a test load resistor;
2. The apparatus of claim 1, further comprising means for discharging said storage capacitor across said test load resistor upon termination of operation of said high voltage inverter means. 5. The control means comprises a reed switch responsive to an actuation signal generated by a magnetic field.
Apparatus described in section. 6. The detection means comprises an electrode that can be placed in the ventricle of the patient's heart to detect R waves,
The defibrillation means further includes an implantable sound emitting means for generating aurally perceptible sounds from outside the patient's body, and a high voltage inverter means for activating and disabling the high voltage inverter means. an enabling circuit means having an enable/disable status output connected to the R-wave detection means connected to the electrodes for detecting R-waves of the patient's heart; the high-voltage inverter means and the R-wave detection means, the audio signal is connected to the R-wave detection means to transmit a control signal representing proper placement of the electrodes on the patient's heart and a control signal representing the operable/disabled state of the high voltage inverter means. logic means for providing an oscillator means and connected to said enabling circuit means and said logic means for selectively enabling and disabling said high voltage inverter means in response to an actuation signal generated outside the patient's body; 2. The apparatus according to claim 1, further comprising switch means for controlling the sound generated by said sound oscillation means with a control signal from said logic means. 7. Said logic means (a) provides a continuous control signal to said audio oscillation means when said enabling circuit means is in an inoperative state; and (b) when said enabling circuit means is in an enabled state. and when the electrode is properly placed on the patient's heart, a periodic control signal is given to the sound oscillation means in synchronization with the R-wave output of the R-wave detection means, and (c) it is operable. When the control circuit means is operational and the electrodes are not properly placed on the patient's heart, it sends an uncontrolled signal to the sound oscillation means, which causes the sound oscillation means to respond to each of the control signals (a). 7. The apparatus according to claim 6, wherein the apparatus generates continuous tones, periodic tones and unvoiced tones in response to (a), (b) and (c). 8. The apparatus of claim 6, wherein said switch means changes the state of said enabling circuit means between an enabled state and a disabled state in response to an actuation signal maintained for a predetermined period of time or more. . 9. The device of claim 6, wherein the sound emitting means comprises a piezoelectric transducer fixed directly to the case of the implantable defibrillation means. 10 The defibrillation means further comprises an implantable defibrillation circuit means for applying corrective high-voltage pulses, a pair of electrodes attached to the patient's heart and applying high-voltage pulses across the heart, and the above-mentioned defibrillation circuit means. and a shunt prevention means connected between the pair of electrodes to prevent energy from being shunted to the upper defibrillation circuit means when a high voltage is externally applied to the pair of electrodes. An apparatus according to claim 1. 11 The shunt prevention means includes an electronic switch connected in series to the pair of electrodes, and activation means for activating the electronic switch when receiving a defibrillation signal from the implantable defibrillation circuit means. Claim 10, wherein said activation means comprises a transformer having a primary winding connected to said defibrillation circuit means and a secondary winding connected to said electronic switch. Apparatus described in section. 12 The detection means includes a bipolar electrode means consisting of a pair of electrodes arranged at a distance of 0.5 to 1.5 cm to detect the heart rate of the patient's heart, and a bipolar electrode means connected to the bipolar electrode means, heart rate detection means for generating an output signal in response to the heart rate detected by the bipolar electrode means, the defibrillation means being connected to the heart rate detection means and configured to detect the heart rate; 2. The apparatus of claim 1, wherein a corrective shock is applied to the patient's heart in response to said output signal detected by said detection means. 13. The device of claim 12, wherein the pair of electrodes are separated by 1 cm. 14 The pair of electrodes are attached to an elongated probe, one electrode attached to the distal tip of the probe and the other electrode attached to a ring circumferentially surrounding the probe spaced from the distal tip. 14. The device according to claim 13, comprising a shaped electrode. 15 The heart rate detection means is based on the incoming ECG
A signal-responsive heart rate detector comprising input means for receiving an ECG signal, processing means for converting the ECG signal into a series of uniform pulses corresponding to heartbeats, and a number of uniform pulses per unit time. averaging means for averaging and generating an analog output signal of a magnitude proportional to this value; and comparing the analog signal of the averaging means with a reference signal, the analog output signal being maintained above the level of the reference signal. 13. The apparatus of claim 12, further comprising threshold means for generating a heart rate detection output signal when the heart rate decreases. 16. The apparatus of claim 15, wherein said processing means comprises an automatic gain control amplifier. 17 The averaging means converts the frequency of the uniform pulse into a voltage output signal.
The device according to item 5. 18 The detection means includes an input means for receiving an ECG waveform; a PDF processing means connected to the input means for processing the ECG waveform based on a probability density function and generating a probability density function output signal; connected to the input means for averaging the frequency of heart beats and converting this frequency into an analog output signal;
The heart rate detection means compares the analog output signal with a reference signal and generates a heart rate detection signal when the analog output signal exceeds the reference signal,
The defibrillation means is connected to the PDF processing means and the heart rate detection means, and starts a defibrillation shock upon receiving the probability density function output signal and the heart rate detection output signal. The device according to paragraph 1.