JPH0238230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an extracorporeal device for recording and later reproducing information regarding disturbances in the electrical activity of the heart. It is intended that this device be used to monitor implantable defibrillators. This device takes the form of an extracorporeal recorder with extracorporeal electrodes for contact with the patient, and information such as the ECG is transmitted to this recording means by means of a telemeter. A delayed, constantly updated memory is always activated. When any one of a number of types of arrhythmia is sensed, or when a defibrillation pulse is applied, the data in memory is "permanently" recorded on magnetic tape.

During the past few decades, coronary artery disease has become the leading cause of death in developing regions of the world. Although the exact cause of sudden death in cases of coronary artery disease is still not completely clear, death in the majority of these cases is due to severe disturbances in the electrical activity of the heart, such as causing ventricular fibrillation. Based on past examples in this field, it is believed that this is the case.

Although it is not possible to predict with certainty which patients with coronary artery disease will fall victim to sudden death, a large group of such at-risk patients can be identified. For example, patients who have experienced a myocardial infarction are at several times the risk of sudden death than the general population, even if they are alive and healthy. Furthermore, if a patient with a myocardial infarction has a history of severe ventricular arrhythmia and/or cardiac arrest, or has signs of persistent myocardial irritability, the risk of sudden death may be substantially increased. logically deduced. Patients similar to those described above would benefit considerably from automatic, standby, or on-demand defibrillators.

Another qualified class of patients who specifically require an automatic defibrillator are those who have no previous myocardial infarction but who have severe symptoms of coronary artery disease, such as ventricular arrhythmias or angina that are side effects of medical treatment. This class is made up of patients with similar symptoms.

Additionally, many people walking the streets today have experienced atrial fibrillation, atrial flutter, or tachycardia. Although not life-threatening, these supraventricular arrhythmias can be debilitating, lead to complications, and require treatment when they occur. Such people often require electrical or pharmacological diversion to return the heart to normal sinus rhythm under medical care.

Great strides are now being made to develop fully implantable automated ventricular defibrillators. For example, see Japanese Patent No. 932290, which discloses the first concept of an implantable automatic ventricular defibrillator. Progress is also currently being made in increasing the reliability of fibrillation detectors. In this regard, see US Pat. No. 4,202,340.
Furthermore, the patent application filed on May 26, 1978
As disclosed in US Pat. Measures are being taken to improve instrument reliability.

Although substantial steps have been taken to develop fully implantable automatic defibrillators and to ensure the operation of sensing and defibrillation circuits, implantable defibrillators are in a period of flux; Don't forget. Therefore, there is a current need for data that would confirm the accuracy of sensing and defibrillation circuits or reveal failures in the circuits. In particular, providing data by recording and later reproducing desired portions of the electrocardiogram (ECG) signal emitted by the heart before and during various disturbances in the electrical activity of the heart. A practical device that can do this is needed. Such a device could not only confirm that an implanted defibrillator is working, but also provide valuable information about a patient's heart activity before and during a cardiac arrhythmia. . Additionally, there is a need for a practical device that can be worn by a patient to monitor cardiac activity in the absence of an implantable defibrillator.

It is an object of the present invention to meet the above-mentioned needs.

The present invention generally relates to an apparatus for recording and later reproducing desired portions of the ECG signal generated by the heart before and during various disturbances to the heart's electrical activity. By using a suitable transducer, the electrical activity of the patient's heart is detected and converted into a typical ECG signal.

In particular, in a preferred embodiment of the invention, the means used to sense the electrical activity of the heart as an ECG signal takes the form of a chest electrode placed on the anterior chest wall of the patient. ECG signals are transmitted from the patient using conventional telemetry technology. This signal is received for recording and later playback by the circuit of the present invention, which is housed in a convenient container such as a purse. In this embodiment, the received ECG signal is converted to a convenient digital form. Digital signals representing ECG signals are stored on a FIFO (first in, first out) basis in a storage device having a predetermined capacity. A conventional arrhythmia detector that constantly monitors the received ECG signal generates an arrhythmia detection logic signal when there is a disturbance in the electrical activity of the heart. For example, such disorders are caused by ventricular tachycardia, bradycardia, asystole, ventricular flutter, ventricular fibrillation, and ectopic beats. The arrhythmia detection logic signal turns on the tape recorder and the tape recorder stores the output of the storage device. After the disturbance ceases and the heart returns to normal electrical activity, the arrhythmia detection logic signal terminates. The tape recorder continues to record the output of the storage device for a predetermined period of time, for example equal to the time interval required for the storage device to read its entire contents once again. Once this is done, the recorder will stop. The recorder thus now has on magnetic tape in digital form the desired portions of the ECG signals generated and received by the heart before and during disturbances in the electrical activity of the heart.

The tape is played on a playback device by the physician or a trained assistant in the physician's office or hospital for later determination of the information recorded thereon.

Generally, the term electrocardiogram (ECG) refers to the use of electrodes on the surface of the body to obtain electrical signals representative of heart activity. On the other hand, the term electrogram generally refers to measurements taken on the surface of the heart. As used herein, the term "ECG" means
Defined broadly, it refers to any measurement of the electrical activity of the heart, regardless of the source or measurement technique of the measurement.

It is therefore an object of the present invention to provide a device for recording and later reproducing desired parts of the ECG signal generated by the heart before and during disturbances in the electrical activity of the heart. .

Another object of the invention is to provide a device that retains valuable information regarding the activity of a patient's heart as represented by the ECG signals occurring before and during fibrillation.

Yet another object of the present invention is to use wireless telemetry technology to record and later reproduce desired portions of the ECG signal generated by the heart before and during disturbances in the electrical activity of the heart. The object of the present invention is to provide a lightweight extracorporeal device using the present invention.

Yet another object of the present invention is to provide a lightweight extracorporeal device for recording and later replaying portions of the ECG signal related to multiple disturbances in the electrical activity of the heart experienced by a patient.

Yet another object of the present invention is to provide an apparatus for recording and later replaying information related to defibrillation attempts by an implantable defibrillator.

Yet another object of the present invention is to assist in identifying the need for a fully implantable ventricular defibrillator in patients suffering from coronary artery disease and to provide treatment for patients suffering from cardiac arrhythmias. The aim is to provide equipment that will help in the process.

Yet another object of the invention is to provide a device for verifying the operation of an implanted defibrillator.

Other objects and advantages of the present invention will become more apparent from the following description and accompanying drawings.

In describing the preferred embodiments of the invention that are illustrated in the accompanying drawings, specific terminology will be used for the sake of clarity. It is to be understood, however, that the invention is not limited to the specific terms so chosen, and that each specific term includes any technical equivalent that operates in a similar manner to serve a similar purpose. sea bream.

One embodiment of the present invention will be described with reference to FIG.

The apparatus of the present invention consists of two units indicated generally at 160 and 170. First unit 160
is an ECG signal transmitting unit worn by the patient. The second unit 170 is an ECG signal receiving and processing unit, which is designed to be placed at a fixed distance from the patient and is housed in a convenient container such as a handbag. .

A chest electrode 162 placed on the anterior chest wall of the patient senses the electrical activity of the heart as an ECG signal.
This signal is sent to amplifier 163. The pulse frequency modulation (PFM) encoder 164 has been amplified.
Converts ECG signal to PFM waveform. In this regard, the PFM waveform includes a plurality of uniform width pulses whose spacing (ie, frequency) is representative of the data being transmitted. PFM waveform is transmitter 16
6 and its output is sent to antenna 168. If the patient has a defibrillator implanted, a defibrillation pulse sensor 172 is shown in phantom.
is included in unit 160. This defibrillation pulse sensor receives the ECG signal from the chest electrode. A normal ECG signal has a magnitude of about 1 millivolt,
Defibrillation shocks, on the other hand, have a magnitude of about 10 volts measured at the skin. Therefore, when the implanted defibrillator delivers a defibrillation shot, the sensor 172 detects the defibrillation shot and generates a signal that is sent to the PMF encoder to be PMF encoded and then Transmitted by transmitter 166 and antenna 168. At the same time,
The signal sent from sensor 172 via line 165 is a special signal that indicates the application of a defibrillation pulse.
The PMF encoder 164 is caused to provide the transmitter.

Receiver 174 receives the transmitted PFM waveform via antenna 176. The output of this receiver is a pulse frequency modulation (PFM) decoder 178
and is sent to signal detector 180. receiver 174
If the output of R/P) device 184, such as a cassette type recorder. Timer 182 generates a signal of the desired width to activate audible alarm 186. In this way, the patient may experience interruptions in the transmission of ECG signals by unit 160, interruption in reception of ECG signals by unit 170, or if the patient enters an area of electromagnetic interference (pulse width different from that transmitted). It makes you realize that something is wrong. Also, the patient is in Unit 1.
60 is out of range of unit 170.

PFM decoder 178 decodes the PFM waveform received from receiver 174 and reconstructs the ECG signal. This reconstructed ECG signal is on line 188
to an analog-to-digital (A/D) converter 190, where the ECG signal is converted to a digital display. This digital representation consists of a series of words, each word consisting of 8 bits.
The reconstructed ECG signal is also sent via line 188 to an arrhythmia detector 192 of known design. The particular type of arrhythmia detector is selected based on the type of cardiac abnormality to be detected. One such arrhythmia detector is described in detail below. The output of the A/D converter 190 is received in a delay store 194 having a predetermined capacity and stored therein on a FIFO (first in, first out) basis. This storage device 194 may include random access memory (RAM) or may include a shift register.

In one embodiment of the invention, storage device 194
contains 8K of random access memory, which is
It can store 1024 words of digital data. These 1024 words represent the most recent 10 seconds of cardiac electrical activity sensed by chest electrode 162. Therefore, at any time, the latest 10 seconds
The ECG signal is stored in storage device 194 in digital form. It should also be noted that the storage capacity can be increased or decreased to store data generated during more or less time.

Clock 196 provides a conversion start signal and gate pulse on line 198 to the A/D converter. A storage address (SA) counter 200 sends the address code to storage 194 via line 202.
give to Clock 196 provides clock pulses on line 204 to increment the SA counter. The SA counter provides an address code to sequentially address all storage locations in the storage device.
As long as a clock pulse is received on line 204, the SA counter constantly repeats the address sequence.

During operation, the output of A/D converter 190 is SA
It is stored in the storage location determined by the address code from counter 200. Conversions are initiated and performed at the A/D converter in response to pulses from clock pulse 196. Once the conversion is complete, the A/D converter outputs a signal on line 191.
Generates a WRITE strobe signal.
Therefore, data from the A/D converter is written to the storage device via data bus 193.
Once the entire RAM has been addressed, the SA counter starts the address sequence again and the A/D
New digital data from the converter is written to storage locations in storage device 194 on a first in, first out (EIFO) basis. Storage device 194 includes read circuitry for constantly reading replaced digital data on line 206.

In a variant of the embodiment of the device of FIG.
The storage device 194 is constructed using eight 1024-bit shift registers. In this variant, storage address counter 200 is not required.
As previously mentioned, the digital display from A/D converter 190 consists of a series of words, each word consisting of 8 bits. The eight bits of each word are written to the first stage of the shift register by the WRITE strobe signal on line 191, one bit to each register. The data in each shift register is shifted sequentially under the control of clock 196. Eventually, the data is shifted to the last stage of each shift register. The data in the last stage of each shift register is shifted out on line 206 as a series of 8-bit words. In this way, new digital data replaces already stored digital data on a first in, first out (FIFO) basis.

When arrhythmia detector 192 detects a disturbance in the heart's electrical activity, it generates two signals, one on line 208 and one on line 210.
sent to. The signal on line 208 enables recording/playback device 184. The signal on line 210 is sent to an internal timer 212, which is, for example, a digital watch chip. This internal timer constantly maintains a track of predetermined information such as date and time in the form of a digital signal called a time tag. line 21
A zero signal causes internal timer 212 to generate a time tag on line 214.

Recording/playback device 184 records the digital data and time tag on line 206 to magnetic tape in response to the enable signal. After the heart damage has stopped and the heart has regained normal electrical activity,
The enable signal on line 208 ends. The recording/playback device continues to record the output of storage device 194 for a predetermined period of time. This predetermined time is, for example, equal to the time interval required for the storage device to read its entire contents once again. When this recording operation is finished, the recorder stops. The recorder thus now has on magnetic tape in digital form the desired portions of the ECG signal generated by the heart before and during disturbances in the electrical activity of the heart.

Thereafter, if a disturbance occurs in the electrical activity of the heart, it is recorded in the same manner as described above. In each case,
Recording/playback device 184 records the digital data and time tag on line 206 to magnetic tape in response to the enable signal. The capacity of a recording/reproducing device is determined by the length of the magnetic tape and the recording speed.

In embodiments of the present invention, the defibrillation pulse sensor 17 is used when a defibrillator is implanted in the patient.
2 is used. As mentioned above, normal
ECG signals have a magnitude of approximately 1 millivolt, while defibrillation shocks have a magnitude of approximately 10 volts. Defibrillation pulse sensor 172 connects chest electrode 16
2 and senses the severe fluctuations in pulse amplitude caused by the application of the defibrillation shock. When this variation occurs, the defibrillation pulse sensor sends the defibrillation sense (DS) signal to line 1.
Occurs in 65. This DS signal causes the pulse frequency modulation (PFM) encoder to transmit codes that would not normally be seen during the transmission of ECG signal data, such as codes with a high pulse repetition rate. Furthermore, this DS signal is an ECG signal from the chest electrode 162.
After being encoded, transmitted, received and decoded as described above for the signal, it is received by defibrillation pulse decoder 161.
This defibrillation pulse decoder 161 receives the DS signal,
Determining an event to be recorded, and responsively generating a signal on line 223 to enable recording/playback device 184 and generating a signal on line 210 to cause internal timer 212 to generate a time tag. urge

Recording/playback device 184 at some point by a physician or a trained assistant in a physician's office or hospital.
The tape is rewound and played. Doctors and hospitals shall be equipped with playback equipment so that a patient can mail the cassette to have his symptoms evaluated. However, for convenience, the playback functionality is integrated with the reception and recording functionality. Information on the tape is passed through a playback decoder 218 to a display device 216 for displaying and interpreting the information in an understandable format. Playback decoder 218
includes circuitry that converts the digital data on the tape into a series of drive signals for the display device 216. This circuit of the playback decoder is connected to the recording/playback device 184.
are selected to take into account the order in which the outputs of storage device 194 were recorded.

Now, an embodiment of the arrhythmia detector 192 will be described in detail with reference to FIG. Appears on line 188
The ECG signal is sent to phase locked loop 220 via A/D converter 219. One of these phase-locked loops was manufactured by RCA Corporation, Solid State, Samoa Abule, New Jersey, USA.
It is RCA4046 manufactured by Division. The phase-locked loop includes an amplifier 222;
Its output is connected to one input of exclusive-OR network 224 and one input of phase comparator 226. The output of voltage controlled oscillator (VCO) 228 is connected to the other input of exclusive-OR network 224 and to the other input of phase comparator 226. VCO22
8 is an external capacitor C1 and two external resistors
Requires R1 and R2. Resistor R1 and capacitor C1 determine the frequency range of VCO 228, and resistor R2 allows the VCO to have frequency offset. The output of the exclusive-OR network is sent to one input of NOR gate 230. The phase pulse from phase comparator 226 is output to NOR gate 230.
is sent to the other input of The output of NOR gate 230 is sent to the input of inverter 232 through a series connection of diode D1 and resistor R3. Capacitor C2 is connected between the input and output of inverter 232. One end of resistor R4 is connected to the input of inverter 232, while the other end is grounded. The output of inverter 232 is a resistor
After passing through R5, it is sent to the input of inverter 234. The output of the inverter 234 is the output of the inverter 23
6 inputs and one input of a 3-input OR gate 244. A resistor R7 is connected between the input of inverter 234 and the output of inverter 236. Voltage Vcc, which is 6V DC, is applied to the input of inverter 234 via resistor R6.

A resistor R8 is connected between the output of the phase comparator 226 and the input of the VCO 228. The input of the VCO is grounded through a series connection of capacitor C3 and resistor R9. Capacitor C3 and two resistors R8 and R9 form a two-pole low pass filter, which improves the frequency capture range and fixing speed. Two series resistors R10 and R11 are connected between the input of VCO 228 and the + input of operational amplifier 238. The +input of the operational amplifier 238 is grounded via the capacitor C5. Capacitor C4
One end is connected to the series connection point of resistors R10 and R11, and the other end is connected to the output of operational amplifier 238. A resistor R12 is connected between the output and the -input of the operational amplifier 238. Arithmetic amplifier 23
The output of 8 passes through resistor R15 to + of operational amplifier 240.
input and also to the -input of operational amplifier 242. A voltage V _DD of 15 V DC is applied to the − input of operational amplifier 240 . Arithmetic amplifier 240
- input is grounded via resistor R14. A resistor 16 is connected between the output and the +input of the operational amplifier 240. The output of operational amplifier 240 is sent to the second input of OR gate 244. The voltage VDD, which is 15V _DC , passes through the resistor R17 to the + of the operational amplifier 242.
applied to the input. Further, the +input of the operational amplifier 242 is grounded via a resistor R18. Arithmetic amplifier 24
A resistor R20 is connected between the output of No. 2 and the +input. The output of the operational amplifier 242 is the OR gate 244
is sent to the third input of Finally, or gate 24
The output of 4 is connected to lines 208 and 21 as a detection signal.
Appears at 0.

The phase-locked loop powered by the voltage V _CC consists of a low power linear VCO 228 and two differential phase comparators 224, 226, which have a common signal input amplifier 222 and a common comparator. It has an input 221. The output of the VCO is directly connected to comparison input 221. Phase comparator 224 is an exclusive-OR network and has a typically triangular phase-output response. If there is no signal or noise at the signal input, the average output voltage of phase comparator 224 is
V _CC /2. Phase comparator 226 is a signal edge controlled memory circuitry that operates on the leading edge of the signal input and the compare input. This comparator constantly adjusts the input voltage of the VCO through a two-pole low-pass filter formed by capacitor C3 and resistors R8 and R9 to equalize the frequency and phase of the signal input and comparison input. If there is no signal input, comparator 2
The phase-locked loop 220 using VCO 26
8 to its lowest frequency. Phase comparator 2
The output of 26 is a 3-state output. When the output of the phase comparator conducts or supplies current to the low pass filter, the output of the phase pulse is a logic zero. When the tri-state output is in a high impedance state, the coarse pulse output is a logic one.

During operation, the output from the A/D converter 219 is
The ECG signal is sent to the signal input of phase-locked loop 220, which phase-locks the QRS of the ECG signal.
Respond to pulses. A phase-locked loop is a regular
Phase-locked to QRS pulse, but irregular
Phase locking is not possible with QRS pulses. The output of the NOR gate 230 is low when the phase-locked loop 220 is phase-locked, and high when the phase-locked loop 220 is not phase-locked. Inverter 232, capacitor C2, diode D1, resistors R3 and R4 form integrator 231. This integrator 231 integrates the output of the NOR gate 230. Capacitor C2 provides a time delay while resistors R3 and R4 adjust the rise and fall times of the output of inverter 232. Inverters 234 and 236 and resistors R5 to R7 form a limit trigger 233, which has two switching thresholds, one near ground and the other
It is near V _CC . The output of the Schmitt trigger appearing on line 235 is low when phase-locked loop 220 is phase-locked and high when it is not phase-locked.

Operational amplifier 238, capacitors C4, C5, and resistors R10-R12 form active filter 229. Arithmetic amplifier 240 and resistors R15 and R16
constitutes the comparator 237. Operational amplifier 242 and resistors R19 and R20 form comparator 239.
The VCO input, which is the input of the voltage controlled oscillator, is applied to a filter 229, which provides a DC voltage directly proportional to the heart's beating rate. Filter 2
The output of 29 is sent to the pulse input of comparator 237. A voltage divider formed by resistors R13 and R14 provides a reference voltage to the negative input of comparator 237. The output of comparator 237 will be low level if the heart rate is normal and high level if it is faster than normal. The output of filter 229 is also sent to the -input of comparator 239. A voltage divider formed by resistors R17 and R18 provides a reference voltage to the +input of comparator 239. The output of comparator 239 is low level if the heart rate is positive, and high level if it is slower than normal.

The output of OR gate 244 will be low when all outputs from Schmitt Trigger 233 and comparators 237, 239 are low, and will be high when any of the outputs is high. When the output of OR gate 244 is high, a signal is provided on line 208 to enable record/playback device 184 and a signal is also provided on line 210 to cause interval timer 212 to generate a time tag.

Many modifications of the present invention will become apparent in light of the above technique. It is therefore to be understood that, within the scope of the invention, the invention may be practiced otherwise than as described.

[Brief explanation of drawings]

FIG. 1 is a detailed block diagram of a preferred embodiment of the invention, and FIG. 2 is a diagram illustrating an embodiment of an arrhythmia detector associated with the embodiment of FIG. 160...First unit, 162...Chest electrode, 164...PFM encoder, 166...Transmitter, 168, 176...Antenna, 170...
Second unit, 172... defibrillation pulse sensor,
174... Receiver, 161... Defibrillation pulse decoder, 178... PFM decoder, 180... Signal detector, 182... Timer, 184... Recording/
Reproduction device, 190...A/D converter, 192
...Arrhythmia detector, 194...Storage device, 196
... clock, 200 ... memory address counter, 212 ... internal timer, 216 ... display device, 218 ... playback decoder.

Claims (1)

[Claims] 1 A device for recording information regarding cardiac activity of a patient, comprising an ECG signal transmitting unit worn by the patient and an ECG signal receiving/processing unit that can be placed at a distance from the patient. The signal transmitting unit generates an ECG signal representing the electrical activity of the patient's heart.
The ECG signal receiving and processing unit comprises an ECG signal generating means and a transmitting means for transmitting the ECG signal to a place remote from the patient.
receiving means for receiving the transmitted ECG signal; first-in, first-out storage means having a predetermined storage capacity for sequentially and temporarily storing the received ECG signals; a cardiac abnormality detection means for detecting abnormality in the patient's cardiac activity and generating a cardiac abnormality detection signal instructing the detection; and a cardiac abnormality detection signal stored in the storage means in response to the cardiac abnormality detection signal. ECG
An apparatus characterized in that it comprises a recording means for reading a signal and recording the read ECG signal until the end of the cardiac abnormality detection signal.