US 3135264 A
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June 2, 1964 M. TISCHLER ETAL 3,135,264
HEART MONITOR-AUTOMATIC CONTROL DEVICE Filed June 14, 1961 5 Sheets-Sheet. 1
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ATTORNEY June 2, 1964 M. TISCHLER ETAL HEART MONITOR-AUTOMATIC CONTROL DEVICE 5 Sheets-Sheet 2 Filed June 14, 1961 INVENTORS Mtk AVRUM TAMRES MORRIS TISCHLER n QE 2.
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HEART MONITOR-AUTOMATIC CONTROL DEVICE Filed June 14. 1961 5 Sheets-Sheet 4 game v I") Q l' R 'G\ I Q 0 HI '4) N b a S a N N H) WH MH I'I a m m FIG. 4-.
AVRUM TAMRES ATTORNEY MORRIS TISCHLER INVENTORS 3,135,264 HEART MONITOR-AUTOMATIC CONTROL DEVICE Morris Tischler and Avrum Tamres, Baltimore, Md., as-
signors to Electronics Aids, Incorporated, Baltimore, Md., a corporation of Maryland Filed June 14, 1961, Ser. No. 117,048 3 Claims. (Cl. 128-423) This invention relates generally to heart therapy apparatus, and more particularly it pertains to an automatic heart monitor-stimulator control device.
The technique of detecting and analysing minute electrical currents generated by the heart muscles is generally well understood. The stimulation of muscular tissue by electrical current is also well known. Recently, the application of shaped and timed electrical pulses to the heart in the treatment of abnormal heart conditions has given a new tool to the heart specialist.
I11 this connection, attention is directed to U.S. Letters Patent No. 3,109,430, issued on November 5, 1963, for Transistorized Heart Stimulator, to one of the present applicants. The use of such a device requires the close attention of the doctor as even a small delay in its application may be fatal.
It is an object of the present invention, therefore, to provide a heart monitor which automatically turns on a heart stimulator to counteract a faltering heart.
Another object of this invention is to provide an automatic heart monitor-stimulator control device which requires a minimum of electircal connections to the patient.
A further object of this invention is to provide a heart monitor-stimulator control device which indicates heart impulses on a rate meter and produces an audible tone or a warning signal for each impulse in the absence of a predetermined number of same.
And another object of this invention is to provide a heart monitor-stimulator control device for heart treatment which will not falsely give stimulation if an electrode to of its associated heart electrodes.
Another object of this invention is to provide a heart monitor-stimulator device which indicates its operating I functions remotely by wire or radio.
United States Patent M These and other objects and attendant advantages of this invention will become more readily apparent and understood from the following detailed specification and accompanying drawings in which:
FIG. 1 is the upper left quarter of a schematic diagram of a heart monitor-stimulator control device incorporating features of this invention;
FIG. 2 is the lower right quarter of the overall schematic diagram of FIG. 1;
FIG. 3 is the upper right quarter of the over-all schematic diagram of FIG. 1; and
' stimulator control device of this invention.
Referring now to the details of the schematic diagram depicted in FIGS. 1, 2, 3, and 4, there is shown a group of three electrodeterminals J1, J2 and J3 at the top of FIG. 1. These terminals J1, J2 and J3 are provided for the connection by means of flexible wires and electrodes, well a known in the art, either externally or internally to the heart of the patient under consideration.
, is in an on condition. An incoming rectangular pulse .voltage to a limiting minus value.
3,135,264 Patented June 2, 1964 The electric signals repersentative of the heart beat are received at these terminals J1, J2, and J3 and are routed through common grounds and switching means to be described subsequently to terminals J4 and J5 of a differential amplifier shown in FIG. 2.
This differential amplifier 100 consists of transistors Q101, Q102, Q103, and Q104. Input coupling capacitors C101 and C102, as well as a control resistor R115 and a fixed resistor R are provided for the amplifier 100. Resistors R103 and R104 are provided in the amplifier 100 for degeneration and stabilizing thereof, while resistors R101, R106 and R102, R107 set the DC. bias and feedback of the amplifier 100. I Capacitors C103, C104 in the differential amplifier 100 determine the frequency response thereof, While resistors R108 and R109 provide collector current for transistors Q101 and Q102 as well as base bias for transistors Q1103 and Q104.
Resistors R110 and R111 are provided in the differential amplifier 100 which have the same function as R103 and R104, mentioned above for degeneraton and stabilization thereof. A resistor R112 is provided which sets the bias level for transistors Q103 and Q104 and it provides additional rejection to common mode inphase currents.
Resistors R113 and R114 are provided in the diiferential amplifier 100 for collector biasing of the transistors. A capacitor C105 is provided in the circuit which limits the upper frequency response of the differential amplifier 100 and corrects for phase shift thereof. A capacitor C106 is provided in the amplifier system and is made small so as to reduce the passage of low frequencies, while a capacitor C107 passes both high and low frequencies to an oscilloscope connection jack J7.
The function of the differential amplifier 100 is to provide high gain to a signal derived from the heart potentials of a patient under consideration (across terminals 1 4 and J5) and to reject unwanted signals which have a similar phase thereacross.
The amplified heart signals are fed from a terminal J 6 to a terminal J8 of a saturation amplifier 200, shown in FIG. 2. This saturation amplifier 200 operates in such a manner that a small positive-going incoming signal causes it to become cut-off. Resistors R201 and R203 in the saturation amplifier 200 set the value of the saturation point. A resistor R202 is also provided in the amplifier 200 which is the collector load for a transistor Q201 and a capacitor C201 is the emitter bypass.
The collector voltage of the transistor Q2111 is normally near zero. A small incoming current shifts its collector Consequently, the wave shape of the output signal is essentially rectangular. When so biased, the transistor Q201 eliminates all but the R wave of the normal ECG heart signal. The rectangular wave resulting from the R wave is fed from a terminal J9 to a keyer 300 depictedschematically in FIG. 3.
The keyer 300 is a two transistor switching circuit of the one-shot multivibrator type. Normally, its transistor Q301 is in an off condition while the transistor Q302 from the saturation amplifier 200 reverses the condition of the transistors Q301 and Q302 and in doing so energizes a relay K301.
Transistor Q301 is held in the normally oif condition by a positive biasing from the resistors R302 and R303. The negative-going pulse is coupled through a capacitor C301 and it develops a voltage across a resistor R301. Any overshoots are clipped by a diode CR301 in the circuit.
Each pulse causes the current in the transistor Q301 to flow, thus closing the relay K301 once for each heart 3 beat. A diode CR302 prevents spurious operation due to inductive transients. The relay K301 is held closed by the switching of the transistor Q302 whose normal collector voltage is zero.
During the switching time, this voltage goes negative which is required at the base of the transistor Q301 for a time duration set by the values of a capacitor C302 and a resistor R304. Normally, this time is set at 0.07 second.
This permits the keyer 300 to switch up to speeds of fourteen cycles per second. Switching speed held no greater than this frequency enables the heart monitor to differentiate between normal heart rhythms and fibrillation.
A capacitor C303 prevents any random switching due to changes in supply voltage or from transients therein. A resistor R305 is provided in the circuit as the collector resistor for the transistor Q302 while a resistor R303 acts as a DC. feed back coupling.
A rate meter circuit 400 is provided in the system which makes use of an integrating network. Each time the relay K301 of the keyer 300 closes, a negative potential is applied to a terminal J of a capacitor C401. This charging pulse is used to charge a pair of capacitors C402, C403 in parallel. The charge on capacitors C402 and C403 is used as a source of current for a microammeter M801, shown in FIG. 1, which is eifectively connected across terminal I11 and ground.
Between pulses, the charge on capacitor C401 is reduced to zero by the relay K301 shortcircuiting the terminal J11 and another terminal J12. Therefore, each new impulse starts a new charge on the capacitor C401 and an additional charge step recurrent in the capacitors C402 and C403.
A resistor R401 in the rate meter circuit provides a constant rate of discharge on the capacitors C402 and C403, while resistors R402 and R403 form a voltage divider for calibrating the microammeter M801 to read heart beats per unit of time.
A capacitor C304 is connected through the contacts of the relay K301 to a charging resistor R306 which leads from a source of voltage. When the relay K301 shifts, it transfers the capacitor C304 to a terminal J13 which, in turn, leads to a terminal J14 of a tone generator 500 shown in FIG. 1.
This tone generator 500 consists of a transformer coupled oscillator transistor Q501 which produces a 1500 cycle tone burst each time it receives an impulse of current from the previously mentioned charged capacitor C304.
A resistor R501 is provided in the tone generator 500 which is the collector limiting resistor, while a resistor R502 and a capacitor C501 set the frequency of oscillation thereof. A capacitor C502 in the generator 500 reduces harmonic production and makes the tone output more pleasing to the ear. The'secondary of an oscillation transformer T501 is connected to a loudness control resistor R4 and a loudspeaker SP601.
Whereas the loudspeaker SP601 may be adjusted to minimum volume by the action of loudness control resistor R4, this control resistor R4 is overridden and full volume is produced in case of alarm. This occurs when a relay K601 functions and removes the ground return from a terminal J15 of the loudness control resistor R4.
Under conditions of an abnormal heart beat, skips or complete stoppage of the heart, an automatic recycle circuit 600 will energize this relay K601 and turn on a stimulator 900, both shown in FIG. 1. The amplifier circuitry from heart electrode terminals J1 and J3 is also interrupted by relay K601 and the electrodes are transferred to a pair of terminals J 16 and J17 to receive stimulation pulses produced by the stimulator 900 connected thereto. For further details regarding this stimulator 900 see the previously referenced co-pending patent application Serial Number 789,989, filed January 25,
' connecied to an AC. mains source.
4 1959, by one of applicants, for Transistorized Heart Stimulator, now Patent No. 3,109,430.
The recycle circuit 600 consists of a pair of transistors Q601 and Q6112, the capacitors C602 and C603, and the resistors R605, R606, and R607, all arranged in a oneshot multivibrator configuration. The intercoupling capacitor C602 is made very large so as to provide a long time constant in the order of thirty seconds.
The base of the transistor 'Q601 is positively biased through a resistor R604. A constant negative voltage is applied through a Recycle Time adjustment resistor R5 and a series resistor R601 to charge a time-out capacitor C601.
When the capacitor C601 becomes sufiiciently negative, a diode CR601 conducts and applies a negative charge to the base of the transistor 'Q601. The transistor (2601 then conducts (fires) and energizes the relay K601 during the thirty second time constant provided by the charge time of the coupling capacitor C602 and then the circuit flips back to the starting condition.
. It will be noted that the negative charging voltage mentioned in the previous paragraph is obtained through contacts of relay K601 so that for thirty seconds the charging of capacitor C601 is interrupted.
The above cycle will never begin, or, if started, will not repeat if a normal heart beat operates keyer relay K301. This is because a pair of contacts thereon periodically short out the capacitor C601 and prevent it from charging sufficiently negative to overcome the diode 'CR601 and fire the transistor Q601. A resistor R602 across capacitor C601 prevents the latter capacitor from long time integration of pulses.
The relay K601, as previously mentioned, opens up loudspeaker SP601 to full volume. It also applies a constant negative operating voltage to a terminal J10 of tone generator 500, thus causing a continuous alarm signal instead of the normal short beats.
Push switches S1 and S2 are provided for cutting out automatic monitor-stimulator operation and for allowing the use of the stimulator only. Another push button switch S3 is provided which permits checking the condition of the heart electrodes. Switch S3 transfers the electrode terminal J3 to ground and the terminal J1 to a resistor R2.
The microammeter M801 is transferred from the rate meter circuit 400 to a junction between the resistor R2 and a resistor R3 which leads from the negative supply. Thus microammeter M801 is connected to an intermediate point of an effective potentiometer arrangement consisting of the resistor R3 in one leg-and the resistor R2 in series with the electrode to ground for the other leg. A good contacting electrode will *have low resistance causing a low Good indication on micrornmeter M801.
The power supply 700 for the monitor-stimulator device is shown schematically in FIG. 4. This power supply 700 consists of a power transformer T701 which is A pair of rectifier diodes CR701 and CR7 02 provide direct current to a filter network consisting of resistors R701 and R702, and capacitors C701 and C702.
A resistor R703 is provided as a dropping resistor for an avalanche diode Z701. 'A battery B701 is charged by the constant voltage across the diode Z701 through a charge limiter consisting of a diode CR703 and a resistor R704 arranged in series connection. Should the AC.
mains source fail, the battery B701 continues to operate:
' the equipment.
thereacross the diode Z704 provides a second source of constant negative voltage which is isolated from the previously mentioned negative output.
A winding L1 on transformer T701 provides the voltage to energize a beacon lamp 11 shown in FIG. 3 whenever relay K301 closes in response to a heart beat. A radio transmitter may be connected across or in place of the beacon lamp I1 to furnish heart beat indication to a physicians pocket radio receiver, thus permitting some freedom of movement from the vicinity of the patient without losing touch with his condition.
It will occur to those skilled in the art that additional connections can be made to the radio transmitter from relay K601 so as to recall the physician in care of alarm actuation thereof.
Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
What is claimed is:
1. A monitor for automatically controlling a heart stimulator and for detecting abnormal heart conditions of a patient, comprising means including a plurality of electrode terminals for connection to a patient, amplifying means connected to said electrode terminals for receiving and amplifying heart impulses of said patient, as stimulator including means for providing electrical pulses for said patient, switching means responsive to normal heart rhythms controlled by the output of said amplifying means for switching said electrode terminals from said amplifying means to said electrical pulse providing means in the absence of said normal heart rhythms, with said electrical pulses being utilized to stimulate the heart of said patient, and means for recycling said terminals between said electrical pulse providing means and said amplifying means periodically as long as said normal heart rhythms are absent.
2. A monitor as recited in claim 1, and additionally means for controlling the period of recycling the terminals between said electrical pulse providing means and said amplifying means.
3. A monitor as recited in claim 1, and additionally loudspeaker means for producing an audible sound representative of said normal heart rhythms, said loudspeaker means being responsive to said recycling means to increase the volume of said audible sound when said normal heart rhythms are absent.
References Cited in the file of this patent UNITED STATES PATENTS 2,368,207 Eaton Jan. 30, 1945 2,848,992 Pigeon Aug. 26, 1958 2,854,968 Wright Oct. 7, 1958 3,002,185 Bases Sept. 26, 1961 3,030,946 Richards Apr. 24, 1962 3,052,233 Veling Sept. 4, 1962 3,057,356 Greatbatch Oct. 9, 1962 OTHER REFERENCES Lillehei article, JAMA, April 30, 1960 (pages Gibson article, Electronics, July 1941 (pages 99401).