Note: Descriptions are shown in the official language in which they were submitted.
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There are individuals walking the streets today who
experience recurring episodes of atrial fibrillation, atrial
flutter, or tachycardia. While not life-threatening, these supra-
ventricular arrhythmias can become debilitating and lead to comp-
lications, and hence require trea-~nent when present. Such indi-
viduals require frequent electrical or pharmacological conversion
under the care of the physicians to return their hearts to normal
sinus rhythm.
Drug therapy is frequently successful in correcting
atrial fibrillation, flutter or tachycardia, but there are many
patients who are resistant to the appropriate drugs or who suffer
serious side-effects from the drugs. For these patients, cardio-
version is accomplished by way of a technique in which a pulse
generator and external paddles combine to send high energy elec-
trical pulses through the ailing patientls thorax to the heart.
For those who suffer from recurring bouts of atrial
tachyarrythmias, regular and often times frequent visits to hos-
pitals are in order. Those whose hearts can be successfully re-
turned to normal sinus rhythm by way of drug therapy frequently
undergo hospitalization so that the effects of the administered
drugs can be carefully monitored. Similarly, those requiring
electrical cardioversion are generally cardioverted in the hos- ., .
pital due to the fact that the procedure frequently required the
application of a general anesthetic and carries with it a sig-
nificant risk to the patient.
It is toward the facilitation of treatment for and the
, reduction of the risks to those patients suffering from recurring
episodes of atrial fibrillation, flutter and tachycardla, that
the present invention is directed.
The present invention relates to an atrial cardioverter
designed to be implanted under the skin of patients who frequentl~
suffer from bouts of atrial fibrillation, flutter or tachycardia.
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During those times when the patient is suffering such an arrhyth-
mia, and cardioversion is in order, a command given by the patient
or his physician brings the inventive cardioverter out of its
standby condition to administer a low-level pulse of energy
directly to the heart, for example, through a catheter implanted
in or about the atrium. Cardioversion by means of an electrical
discharge delivered through an intra-atrial catheter has been
shown to require energies of five watt-seconds or less, and is
thus a painless procedure not requiring anesthesia.
In one embodiment of the present invention, the patient
will likely visit the office of his physician for treatment. By
way of an external console, the physician programs the desired
level of cardioverting energy to be administered. Then, both the
power to charge an implanted discharge capacitor and a set of
control signals corresponding to the programmed level of cardio~
verting energy is transmitted through the skin of the patient
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and into the implanted unit. In addition, the invention contem-
plates that an ECG synchronization signal be derived either inter-
nally or from an external ECG unit and fed back -through the skin
of the patient as a command signal to ensure that cardioversion
occurs in proper synchronization with the QRS complex. With the
present invention, provision can be made to discharge the stored
energy through a test load for verifying the readiness of the
implanted unit, and information can be extracted through the skin
of the patient so that the physician is able to monitor the dis-
charge of the implanted capacitor, which is either through the
test load or the implanted atrial catheter.
In another embodiment of the present invention, the
patient is able to cardiovert himself at home, without the inter~
~ention of his physician. The patient who frequently undergoes
attacks of atrial fibrillation, flutter or tachycardia can be
taught to recognize the symptoms of such arrhythmias. Once able
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to recognize that he or she is experiencing such an attack of a
convertible arrhythmia, the patient can effect cardioversion when
appropriate.
In the second patient-operated embodiment o~ thepresent
invention, an ener~y source is incorporat~d into the implanted
cardloverting device. The energy source is normally maintained
out of the cardioverting circuit, and is connected into the cir-
cuit only upon the issuance of an appropriate command. As here
disclosed, the patient issues this command by holding a magnet
at an appropriate location against his skin, and a reed switch
closes. Upon ~he closing of the reed switch, the energy source
is brought into the circuit, and the discharge cycle is initiated.
In the embodiment of the present invention designed for
operation by a physician, the level of cardioverting energy to
be delivered to the patient can be manually programmed. In the
embodiment of the invention designed for operation without the
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intervention of a physician, it is also possible to deliver the
cardioverting shocks in varied energy levels. In this regard,
the patient-operated embodiment of the invention contemplates
sequentiall~ increasing the cardioverting energy level over prior
attempts at cardioversion. The patient controls repeated dis-
charges by way o the duration of magnet placement against his
skin.
Like the first, the second embodimen-t of thepresent
invention can be equipped with circuitry for synchronizing the
cardioverting shocks with the QRS complex. This can be accomp-
lished by way of a sensing probe positioned in or about the
heart.
A major object of the present invention is to provide
an implanted e~ternally operated device which will efficiently
cardiovert a heart under~oing atrial fibrillation, flutter or
tachycardia, comfortably, without the necessity for administration
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of an anesthetic, and without the necessity of physician inter-
vention.
Another major object of the present invention is to
provide an implanted cardioverter whose operation can be verified
before the discharge of electrical energy into the heart.
These and other important objects of the present inven-
tion will become more apparent when reference is made to the
following description taken in conjunction with the accompanying
drawlngs .
~igure 1 is a block diagram of an embodiment of the
inventive implantable command cardioverter particularly suited
for use in the office of a physician;
Figure 2 pictorially depicts the physician's console
which is represented in Figure l as associating with the inventive
implantable cardioverter; and
Fiyure 3 is a block diagram of another embodiment of
the inventive implantable command cardioverter, suitable for
operation without the intervention of a physician.
~ ith reference initially to Figures 1 and 2, the first
embodiment of the present invention will be described. The inven-
tive implantable command cardioverter is indicated generally at
10 and is adapted to associate with an external console generally
designated at 12. Console 12 includes circuitry for transmitting
power and control lnformation to the implanted cardioverter for
receiving information about the nature of the cardioverting pulses
from the implanted cardioverter as well as signals from other
cardiac equipment, and for visually displaying selected cardiac
in~ormation. The numeral 14 schematically represents the skin of
; the patient, and hence shows the separation ~etween the implanted
cardioverter lO and the external console 12.
The console 12 comprises a power and information trans-
mitter 16 which communicates with an implanted receiver unit l~.
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Information such as the desired cardioverting energy, whether the
unit should be in its "test" or its operating mode, etc., all of
which will be explained below, is programmed into an operating
control unit 20. Unit 20 may, for example, include a plurality
o~ on-of switches which generate digital signals. The digital
signals from operating control unit 20 are i-ed in parallel to an
information modulator circuit 22 where they are converted into a
serial chain of operating commands.
Schematically illustrated in Figure 1 at 24 is an ECG
input which may be in the form of a conventional ECG unit or an
amplifier which is made an integral part of the console 12. A
sequence of electrocardiograph s-ignals taken from the skin 14 of
the patient is further illustrated at ~ in Figure 2. From the
electrocardiograph input 24 can be derived impulses which are
representative of the occurrence of the QRS complex. The QRS
impulses are fed to the information modulator 22 as is schemati-
cally represented, from the ECG synchronization unit 26.
Also part of the external console 12 is a receiver and
decoder 28 which is adapted to receive and decode information
transmitted by the implanted transmitter 30. After being decoded,
the information delivered across the skin 1~ by transmitter 30 is `
displayed at an external display unit 32. As can be seen, the
implantea transmitter 30 sends signals across the skin 14 of the
patient to *he--receive~ and decoder 28 much the same as-external
transmitter 16 sends signals to 1mplanted receiver 18. Of course,
the particular form of modulation couid be different.
As represented in Figure 1, power and information sig-
nals are transmitted through the skin of the patient by way of
coupled transformer primary and secondary windings. In the
specific physician-controlled embodiment herein illustrated and
described, power to the implanted unit and the control information
is, for simplicity, transmitted along the same channel. The
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control information can be modulated into the power channel by
~requency shift keying, pulse width modulation, or any other
appropriate well-known modulation technique.
With specific reference to Figure 2, the external con~
sole 12 can he seen to include a display portion 32 and an operat~
ing control panel generally designated at 20. Control panel 20
is.equipped with an on/off switch 34, an input for the ECGsignal 24, ~:
a rotary energy dischàrge dial 36 to enable the physician to
control the amount of energy discharged into the heart, a toggle
switch 3~ for controlling whether the stored energy is discharged
into a test load or into the heart, a push button 40 to initiate
the discharge of the implanted storage capacitor, and a load-
data push button 41. Also illustrated as part of the display
portion of external console 12 is a cathode ray tube 42 shown as
simultaneously displaying the periodic QRS complex 4~ and, in
broken lines, the discharge of the implanted storage capacitor.
~ ith continuing reference to Figures l and 2, the opera- :
tion of the external unit will be described. The patient suffer-
ing ~rom a convertable atrial arrythmia, such as atrial ~ibrilla-
tion, ~lutter or tachycardia, is e~amined by the physician, pre-
ferably with the aid of ECG e~uipment. Based upon this input,
. the physician makes his best estimate o~ the energy level which
will be required to cardiovert the malfunctioning heart, and sets
rotary dial 36 accordingly. The ECG synchronization input is then
connected to ~he console 12, the toggle switch 3~ is set to either
. the test load or catheter discharge position, and toggle 34 is
moved to the `'oni' position. ~t this time, the unit is functional,
with energy being transmitted to the implanted circuitry, and with
EC~ signals being displayed on the display device 32 as shown at
4~. The physician then presses the load-data button 4:L to trans-
mit the instructions regarding the level of the dischaxge pulse
to the implanted unit at which time the energy storage capacitor
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is charged to the desired level. When ready, the "discharge"
button 40 is depressed, and either the test load or the heart is
shocked at the proper time during the QRS complex. The test load
is, of course, intended to verify attaining the proper level of
discharge before a shock is actually appliecl to the heart. ~hen
the discharge level is verified, the physician simply moves
switch 38 to the catheter position, presses the load-data button
and then the "discharge" button 40 to deliver a pulse to the heart.
Once a shock is actually applied to the heart, the physician ob-
serves the screen of CRT 42, and either concludes his activity ifcardioversion is successful, or repeats the cardioverting attempt
at perhaps a higher energy level if unsuccessful.
When the rotary energy dial 38 and the other controls
are set by the physician, the operating con-trol unit 20 provides,
~or example, a binary signal representative of the energy level
to which the dial 36 is set and other operating parameters. This
signal takes the form of a parallel binary contro~ woxd. As noted
above, the rotary dial 36 could be replaced by a set of toggle
switches, each one of which would provide a discrete binary con-
trol signal. The parallel binary control word from the operatingcontrol unit 20, as illustrated in Figure 1, is delivered to the
information modulator 22 where it is converted into a serial binary
control word. From modulator 22, the serial control word is del-
ivered to the transmitter 16 and sent tothe implanted device along
the information channel. Simultaneously, the ECG synchronization
signal is delivered to the modulator 22.
~ hen the on/off switch 3~ on the external console 12 is
in the "on" position, the transmitter 16 is activated, and energy
; in the for~ of power signals is transformer coupled across the
~ `0 skin of the patient. This energy is received through the secondary
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winding of the ~oupling transformer at receiver 18. Then, when
the load-data button 41 is depressed, the serial binar~ control
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word i5 transmitted along the information channel. The serial
control word recovered by the receiver 18 ta]ces the form of a timed
set of pulses. The receiver 18 directs these serial pulses to a
control register 48 which reconstructs them into their original
parallel format. The parallel control word, along with other
control information, provides a signal proportional to the desired
energy level which is then transmitted via discrete lines 50 to
circuitry associated with a power inverter 52.
Before the activity of the power inverter 52 is initi-
ated, the control register 48 issues a "go" signal which confirms
receipt of the control word from the receiver 18. This may be
accomplished in any of several well-known ways, for example, by
ending each control word with a unique character to designate its
end. This "go" command is indicated at 54. As represented in
Figure 1, with three energy control lines 50, a maximum of eight
power levels can be set, as a binary format is used. The specific
operation of the power inverter 52 and the associated circuitry
which serves the purpose of charging the storage capacitor at a
predetermined energy level, will be explained below.
The receiver 18 also feeds to the control register 48,
information related to the QRS synchronization and whether the
energy storage device is to be discharged into the implanted
catheter or into a test load. As seen in Figure 1, the synchroni-
~ zation signal is carried along lead 56 while the test-mode signal
; is directed along lead 58. The signal on line 58 is fed to arelay driver 60 ~hich associates with coil 62 and in turn, a
switch 64. In one position of the switch 64, indicated a~ 66,
energy is directed into a test load 68. In the other positio~,
designated70 the discharge capaci-tor feeds directly to a cathetex
72 implanted i~ or about the atrium 74 o~ a heart 76.
~hen activated, the power inverter 52 directs energy to
an energy storage and discharge device 78 which in this case takes
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the form of a storage capacitor. ~hen the energy stored by the
capacitor 78 reaches the level set on the rotary dial 36, as will
be fully explained below, a "ready" signal is produced by a com-
parator 100 and fed via line 80 to an AND gate 82. ~he same
"ready" signal is also fed bac~ to the power inverter 52.
The "ready" signal which is produced by the comparator
100 is indicative of the discharge capacitor being in readiness
for firing through a discharge switch 84. Synchronization signals
are at this time, fed to the AND gate 82 along with the "ready"
signal on line 80, and upon the simultaneous occurrence of a
"ready" signal on line 80 and a QRS synchronization pulse on line
56, AND gate 82 responds by issuing a signal which controls the
state of switch 84, and firing the capacitor 78 through the dis-
charge switch. The position of switch 64 determines whether the
capacitor 78 fires thro~lgh the test load 68 or through the
catheter 72.
The capacitor 78 is charged as explained below. When
the control register 48 produces the "go" signal at line 54, this
signal reaches a gate input of the power inverter 52. Power in-
verter 52 can be of any conventional inverter design which pro-
duces an output some~here on the order of 600 volts and can be
gated "on" and "o~f" by the application of ex-ternal gating com-
mands. The "go" signal from the control register 48 gates -the
power inverter 52 on, and the relatively constant 600 volt output
,
is thereby initiated. The output of the power inverter 52 is fed
` dixectly to the capacitor 78.
As can be seen, a resistive divider in the form of a
pair of resistors 102 and 10~ is connected across capacitor 78,
and the signal appearing at the junction between the resistors
102 and lQ4 is tapped into one input terminal 106 of comparator
100. The "energy control" command which is produced a~ the con-
trol re~ister 4~ and fed alon~ lines 50 forms the input to a
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digital-to-analog converter 108. The converter 108 is o~ conven-
tional design, with its analog output being directed to the other
input terminalllO of compara-tor 100~
When the voltage across capacitor 78 reaches the preset
desired level, the signal reaching the input 106 of comparator
100 balances the control signal at input 110. At this time, the
comparator 100 produces a "ready~' signal which is simultaneously
transmitted to AND gate 8~ along line 80 and to power inverter
52 along ~eedback path 112. The "ready" signal on llne 112 gates
the power inverter 52 into its off state. At this point in time,
the capacitor 78 is fully charged and in readiness for discharging
into either the test load or the heart, and hence the charging
operation is completed.
As noted previously, the present invention contemplates
an implanted transmitter 30 associated with the receiver and de-
coder 28 forming a part of the external console 12. The discharge
of the capacitor 78 through either the test load 68 or the cathe-
ter 72 is monitored at line 86 which directs a pulse representa-
tive of the discharge to a pulse modulator 88. The pulse modula-
tor feeds a modulated signal to transmitter 30 which, in turn,transformer couples the signal across the skin 14 of the patient
and to the ex~ernal receiver and decoder 28. After decoding, the
signal representative of the delivery of an electrical shock is
displayed on the CRT as at 46 in Figure 2.
Now, with reference to Figure 3, the totally implantable
embodiment of the inventive elective atrial cardioverter will be -
described. For convenience of description, those elements which
have previously been described with reference to Figure 1 are
similarly numbered in Figure 3, and will not again be described
3~ in detail.
In the embodiment illustrated in Figure 3, each element
of the inventive cardioverter is implanted beneath the skin 1~ of
... . .. , ,. . . . : .
the patient with the exception of a command magnet 112. Here, the
patient controls the operation of the implanted cardioverter by
pOSitioning the command magnet 112 at a location on his body
immediately opposite an impla~ted reed switch 114. When so posi-
tioned, reed switch 114 closes, and the imp:lanted cardioverter is
activated.
The fully implanted cardioverter is generally shown in
Figure 3 at 10'. After the reed switch 114 closes, a timer 116 . .... .
is turned on and, after a preset delay set into the timer, a
switch 118 is closed to direct energy from an implanted battery
120 to the input of. the power inverter 52. Simultaneous with the
closing of the reed switch 114, a "clear" signal is issued along
line 122 and is ~ed to a binary counter 124 to reset the same to
its initial.state. .I~ should of course be appreciated that clo-
sure of the reed switch 114 also delivers operating power to the
timer 116 and to the binary counter 124, but such connections have
been eliminated to simplify the block diagram of Figure 3.
As is evident from Figure 3, an ECG signal is derived by
; way of a catheter 126 implanted in or about the heart, as in the :
right ventricle 128. This ECG signal is further developed ~t ECG
circuitry 130, and synchronization pulses are in turn produced at
a QRS synchronization circuit 132. As before, the "ready" signal .
from the inverter-capacitor circuit and -the synchronization signal
from the QRS synchronization circuit 132 are both fed to an AND ~-.
gate 82. Upon coincidence of the "ready" and synchronization
signals, AND gate 82 switches the discharge switch 84 to its con-
ductive state,. thereby discharging the storage and discharge capa-
citor 78 through the heart 76 by way of a catheter 72 implanted in :
or about the heart, as in the right atrium 74.
- 30 The operation of the circuit illustrated in Figure 3 is .
as follows. When the knowledgeable patient expexiences either
.atrial fibrillation, flutter or tachycardia, and elects to undergo
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cardioversion, he places the command magnet 112 at the appropriate
location near the reed switch 114. The magnetic pull closes the
reed switch 114, clears the binary counter 124, and places the
timer 116 in its counting state. After a preset delay, timer 116
produces a command which places switch 118 in its conductive state
and hence energy is delivered from the source 120 to the power
inverter 52.
Once being clearedt binary counter 124 takes its first
state which commands power inverter 52 to charge the discharge
capacitor 78 to its lowest predetermined energy level. This is
accomplished by the binary counter 124 developing an energy con-
trol signal, and feeding the same to the power inverter 52 along
lines 50. In the same manner as explained above, when discharge
capacitor 7~ reaches the proper level of charging, a "ready" sig-
nal is issued and is passed to AND gate 82 via line 80. At the
same time, the ventricular catheter 126 or another appropriate
sensing lead senses the heart function, and a set of QRS synchroni-
zation pulses is produced by circuit 132 and fed to AND yate 82
via line 56.
Upon the simultaneous occurrence of a "ready" signal and
a QRS pulse, AND gate 82 switches discharge switch 84 to its con-
ductive state and the discharge capacitor 78 discharges through
the heart 76 of the patient via atrial catheter 72~ Firing of
capacitor 78 through the atrial catheter 72 issues a signal at
line 134 which sets binary counter 124 to its second state. At
the same time, the delay period of timer 116 is reinitiated to
enable the patient to assess the effect of the first pulse.
If the patient successfully undergoes cardioversion, the
command magnet 112 is removed, and the procedure is completed. If
however, after the elapse of the time delay set in timer 116, the
patient determines that his heart is still in fibrillation, or
undergoing flutter or tachycardia, another cardioversion will be
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attempted. With the inventive circuit, this second attempt is
at a higher energy level.
After deciding that a second attempt at cardioversion
is appropriate, the patient maintains command magnet 112 in its
position opposite reed switch 114. As such, there is no "clear"
signal lssued to binary counter 124, and counter 124 remains in
its second state after being advanced by the ~irst discharge of
the capacitor 7~ through the heart. ~he preset delay in timer
116 elaps~sr and switch 118 is placed in its conductive state.
Therefore, energy source 120 again energizes power inverter 52.
Binary counter 124 then being in its second state, commands power
inverter 52 to charge energy storage and discharge capacitor 78
to a higher level of energy. When capacitor 78 reaches this high-
er energy level, the capacitor is again discharged through the
heart in proper synchronization with the QRS complex. This
stepped discharge through the heart can be programmed, as desired
by presetting the number of stages of the binary counter 124.
It should be appreciated that as shown in the embodiment
illustrated in Fi~ure 3, the QRS synchronization signal can be
~20 taken internally, as, for example, from a catheter implanted in
the ventricle. Such an arrangement can also be used in the
device of Figure 1 in lieu of the external ECG console. Further-
more, while the specific embodiment of Figure 3 employs a multi-
stage discharge in increasing-energy levelsj such is not necessary -~-
in the basic design of the implantable cardioverter. Rather, the :
binary counter and associated circuitry can be elimina-ted, and
the power inverter 52 set so that the first discharge through the
heart is at a level sufficient to cardiovert the heart under most
condi~ions of fibrillation, flutter and tachycardia.
While specific embodiments of the present invention have
been described, it should be understood -that these embodiments are
described for purposes of illustration only.
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