U.S. patent application number 09/732320 was filed with the patent office on 2001-05-10 for implantable electric heart defibrillator with attenuation of the pain resulting from the electric shock.
This patent application is currently assigned to Leonardo Cammilli. Invention is credited to Cammilli, Leonardo, Grassi, Gino.
Application Number | 20010001126 09/732320 |
Document ID | / |
Family ID | 11352028 |
Filed Date | 2001-05-10 |
United States Patent
Application |
20010001126 |
Kind Code |
A1 |
Cammilli, Leonardo ; et
al. |
May 10, 2001 |
Implantable electric heart defibrillator with attenuation of the
pain resulting from the electric shock
Abstract
An implantable electrical heart defibrillation system for both
ventricle and atrium is proposed and is characterized in that it
acts in a manner such as: to diagnose the type of arrhythmia within
a maximum time of 2 seconds from the onset of the arrhythmia; to
deliver the therapeutic shock by electrodes implanted in the region
to be defibrillated no more than 4-5 seconds after the recognition
of the arrhythmia, if it is ventricular fibrillation, so that the
patient does not loose consciousness; immediately after the onset
of the arrhythmia and before the defibrillation shock is delivered,
to prevent the conduction of neural pain signals coming from the
region in which the electric shock acts, by means of nerve
stimulation by a catheter inserted in the spinal column, utilizing
the gate effect, or by the perfusion of a drug with immediate
analgesic effect by means of an infusion pump and a catheter
positioned in the region affected by the pain signals. This system
enables defibrillation or conversion to be carried out with the
patient conscious and within a sufficiently short time to be able
to use low shock energy, and with prevention of the consequent
painful shock. This considerably improves the quality of life of
the patient who is no longer subject to loss of consciousness
during ventricular fibrillation and does not feel the pain during
the electric shock.
Inventors: |
Cammilli, Leonardo;
(Firenze, IT) ; Grassi, Gino; (Sesto Fiorentino,
IT) |
Correspondence
Address: |
Terry. L. Wiles, Esq.
Popovich & Wiles, PA
IDS Center, Suite 1902
80 South 8th Street
Minneapolis
MN
55402
US
|
Assignee: |
Leonardo Cammilli
|
Family ID: |
11352028 |
Appl. No.: |
09/732320 |
Filed: |
December 7, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
09732320 |
Dec 7, 2000 |
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|
09057206 |
Apr 8, 1998 |
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|
6167305 |
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Current U.S.
Class: |
607/5 |
Current CPC
Class: |
A61N 1/39624 20170801;
A61N 1/36071 20130101 |
Class at
Publication: |
607/5 |
International
Class: |
A61N 001/39 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 1997 |
IT |
FI97A000071 |
Claims
What is claimed is:
1. A method of electrically defibrillating a heart, comprising: (a)
sensing a heart arrhythmia; (b) stimulating the spinal column to
produce an analgesic effect; and (c ) delivering an electrical
shock to defibrillate the heart.
2. A method of electrically defibrillating a heart as in claim 1,
wherein the step of stimulating the spinal column comprises
saturating the pathways of the pain caused by the shock by the gate
control method.
3. A method of electrically defibrillating a heart as in claim 1,
wherein the step of delivering the electrical shock is synchronized
with the patient's QRS.
4. A method of electrically defibrillating a heart as in claim 1,
wherein a blanking circuit is provided, the blanking circuit
generating a signal which can protect the other circuits from the
electrical shock, the blanking circuit being activated prior to the
delivery of the shock and termninating after delivery of the
shock.
5. A method of electrically defibrillating a heart as in claim 1,
wherein the arrhythma is a ventricular fibrillation.
6. A method of electrically defibrillating a heart as in claim 5,
wherein the step of sensing the ventricular fibrillation comprises
sensing within 2 seconds from the start of the ventricular
fibrillation an electrical signal from the heart having an average
frequency of greater than 280-300 beats per minute with
irregularities in period and amplitude and sensing a stoppage of
pumping of the heart.
7. A method of electrically defibrillating a heart as in claim 5,
wherein the step of delivering the electrical shock comprises
delivering the electrical shock no longer than three seconds after
sensing the ventricular fibrillation.
8. A method of electrically defibrillating a heart as in claim 5,
wherein the step of stimulating the spinal column to produce an
analgesic effect comprises infusing an analgesic drug immediately
upon sensing the ventricular fibrillation.
9. A method of electrically defibrillating a heart as in claim 5,
wherein the step of stimulating the spinal column to produce an
analgesic effect comprises electrically stimulating a nerve
immediately upon sensing the ventricular fibrillation.
10. A method of electrically defibrillating a heart as in claim 5,
wherein the step of stimulating the spinal column comprises
saturating the pathways of the pain caused by the shock by the gate
control method.
11. A method of electrically defibrillating a heart as in claim 5,
wherein a blanking circuit is provided, the blanking circuit
generating a signal which can protect the other circuits from the
electrical shock, the blanking circuit being activated prior to the
delivery of the shock and terminating after delivery of the
shock.
12. A method of electrically defibrillating a heart as in claim 1,
wherein the arrhythmia is an atrial arrhythmia.
13. A method of electrically defibrillating a heart as in claim 12,
wherein the step of sensing the arrhythmia allows sufficient time
to verify the stability of the arrhythmia.
14. A method of electrically defibrillating a heart as in claim 12,
wherein the step of delivering the electrical shock may take up to
one minute from sensing the arrhythmia, and the electrical shock is
between 1 and 10 Joules.
15. A method of electrically defibrillating a heart as in claim 12,
wherein the step of stimulating the spinal column occurs at least
two seconds before the electrical shock.
16. A method of electrically defibrillating a heart as in claim 12,
wherein the step of delivering the electrical shock is synchronized
with the patient's QRS.
17. A method of electrically defibrillating a heart as in claim 12,
wherein the step of stimulating the spinal column comprises
saturating the pathways of the pain caused by the shock by the gate
control method.
18. A method of electrically defibrillating a heart as in claim 12,
wherein a blanking circuit is provided, the blanking circuit
generating a signal which can protect the other circuits from the
electrical shock, the blanking circuit being activated prior to the
delivery of the shock and terminating after delivery of the
shock.
19. A method of electrically defibrillating a heart as in claim 1,
wherein the arrhythmia is ventricular tachycardia.
20. A method of electrically defibrillating a heart as in claim 19,
wherein the step of sensing the ventricular tachycardia comprises
sensing an electrical signal from the heart beating up to 300 beats
per minutes, wherein the beats have substantially constant
frequency and amplitude, and further sensing an attenuated and/or
irregular blood flow without stoppage of the heart.
21. A method of electrically defibrillating a heart as in claim 19,
further comprising the step of applying a pacing electrical
stimulus as a first treatment and, if this is unsuccessful after a
programmed number of attempts, delivering a low energy
cardioversion shock.
22. A method of electrically defibrillating a heart as in claim 19,
wherein the step of stimulating the spinal column comprises
saturating the pathways of the pain caused by the shock by the gate
control method.
23. A method of electrically defibrillating a heart as in claim 19,
wherein a blanking circuit is provided, the blanking circuit
generating a signal which can protect the other circuits from the
electrical shock, the blanking circuit being activated prior to the
delivery of the delivery of the shock and terminating after
delivery of the shock.
24. A method of electrically defibrillating a heart as in claim 1,
wherein the step of stimulating the spinal column comprises
infusing an analgesic drug with immediate effect.
25. A method of electrically defibrillating a heart as in claim 1,
wherein the step of sensing the arrhythmia comprises sensing the
arrhythmia through electrical, mechanical, or electromechanical
impulses.
Description
FIELD OF THE INVENTION
1. The present invention concerns a heart defibrillator and a
method for its operation.
2. The invention has been developed with particular attention to
its possible application to so-called heart defibrillators. The
invention is, however applicable to defibrillators in generally and
should not therefore be understood as limited to the specific field
of use referred to below in the present description.
BACKGROUND OF THE INVENTION
3. Most unexpected heart deaths are due to ventricular fibrillation
in patients both with and without coronary disease. Ventricular
fibrillation consists of chaotic, asynchronous and fractional
activity of the ventricles. In a heart which has started the
ventricular fibrillation process, all of the cells contract
independently and not synchronously, with the final result that the
pumping function of the heart is lost and circulatory arrest
occurs; without intervention, the patient dies.
4. The only way of intervening is by electric heart defibrillation.
This method, which was implemented successfully as early as 1908,
came back into clinical practice around the 1940s and has been used
increasingly since then. External defibrillation is achieved by
applying to the patient's chest two plates by means of which an
electric shock is transmitted. In recent years, implantable
electric defibrillators have been designed and produced and these
apply the electric shock directly to the heart wall, the shock
being delivered automatically as soon as ventricular fibrillation
is recognized by the circuits.
5. It should also be noted that malignant ventricular tachycardia
(MVT), which is usually a precursor of ventricular fibrillation,
can also be treated by electric cardioversion. A stimulation system
with anti-tachycardia programs (with burst and premature
extra-stimulation capabilities and the like) which are used as a
first approach for the cardioversion of MVT is fitted, together
with the defibrillation system, in the same device. In serious
cases which are insensitive to anti-arrhythmic stimulation, when a
certain number of attempts with this program have been found
ineffective, the system can deliver an electric shock which has a
greater probability of interrupting the MVT but which usually has
less energy than for ventricular fibrillation.
6. The implantation of these devices (ICDs--implantable
cardioverter defibrillators) started in 1980 and, since the 1990s,
has increased notably because of the considerable technological
progress and the increased ease of implantation due, in particular,
to the use of catheter-electrodes which are introduced by a
peripheral venous route in the same manner as for the implantation
of pacemakers.
7. The implantation of ICDs is currently the only safe means of
ensuring the survival of patients affected by these arrhythmias
which are otherwise fatal.
8. There are, however, considerable problems, including:
9. a) the harmful nature of the electric shock which, with the
energy of about 30 Joules currently used, damages the mitochondrial
structures of the cells, and
10. b) the fact that the life of the patient wearing the ICD is
rendered traumatic by the loss of consciousness which occurs in the
presence of ventricular fibrillation and hence of defibrillation,
even though this saves the patient's life.
11. In fact, the shock is delivered about 10 seconds after
ventricular fibrillation is recognized; this leads to circulatory
arrest with loss of flow of oxygenated blood to the brain so that,
after 5-6 seconds, the patient loses consciousness, falling to the
ground if he is standing up.
12. The delay in the delivery of the shock is necessary in order to
confirm the diagnosis of ventricular fibrillation and to charge the
capacitor which serves to store the energy for the delivery of the
shock.
13. The delay is also necessary in order to deliver the shock when
the patient is unconscious so that he does not feel the pain of the
discharge. In some cases of younger patients who are still
conscious when the discharge is delivered, the sensation of pain is
in fact so strong and distressing that some patients have asked for
the ICD to be removed.
14. The situation in which it is necessary to interrupt MVT by
means of the shock should also be considered; in fact the delivery
of the shock takes place when the patient is fully conscious since,
although MVT is disabling, it does not cause loss of consciousness.
In these cases, the pain complained of by the patient which,
amongst other things, is sudden, is very great, although it is not
of long duration.
15. In any case, even in patients who do not feel the shock, their
existence becomes so traumatic with the continual fear and
expectation of crises accompanied by loss of consciousness that
they sometimes prefer the risk of death.
16. A condition which is similar to ventricular fibrillation as a
physiological phenomenon, although it does not involve an immediate
danger of death of the patient will now also be considered.
17. Atrial fibrillation (AF) is an arrhythmia which causes
disappearance of the atrial contractions which are replaced by
fibrillation, that is, by uncoordinated activity which nullifies
the pumping effect of normal contraction. It is compatible with
life since blood circulation is maintained, although with a
reduction in the cardiac range.
18. However, atrial fibrillation causes stagnation of the blood in
the atrium which favors the formation of a thromboembolism which,
in time, puts the patient's life at risk. Moreover, the
irregularity of the ventricular response may set off dangerous
ventricular tachycardia. This arrhythmia can be treated
pharmacologically but insensitivity to the drugs is often
encountered.
19. Another possibility is electric cardioversion which consists of
the application of an electric shock similar to ventricular
defibrillation but with lower discharge energy. A couple of years
ago, the implanted atrial defibrillator technique was proposed and
implemented in order to deliver a shock directly to the appropriate
locations of the heart cavity at the onset of the arrhythmia. For
this treatment, the need to attenuate or cancel out the pain caused
by the discharge which, in this case, is applied to conscious
patients who have difficulty in tolerating it, becomes
fundamental.
20. It can be seen from the foregoing description that an ability
to prevent the pain signals from being perceived by the patient is
very important.
SUMMARY OF THE INVENTION
21. The object of the invention is to produce an implantable atrial
or ventricular defibrillator which allows patients to have a less
traumatic life, by means of the characteristics which will be
described below.
22. In one aspect, this invention is a method of electrically
defibrillating a heart, comprising sensing a heart arrhythmia;
stimulating the spinal column to produce an analgesic effect; and
delivering an electrical shock to defibrillate the heart. The
method may also include stimulating the spinal column by saturating
the pathways of the pain caused by the shock by the "gate control"
method. Preferably, the step of delivering the electrical shock is
synchronized with the patient's QRS. A blanking circuit also may be
provided. The blanking circuit generates a signal which can protect
the other circuits from the electrical shock, and is activated
prior to the delivery of the shock and terminated after delivery of
the shock. The arrhythmia may be a ventricular fibrillation or
atrial arrhythmia.
23. The step of sensing the arrhythmia may include sensing within 2
seconds from the start of the arrhythmia an electrical signal from
the heart having an average frequency greater than 280-300 beats
per minute with irregularities in period and amplitude and sensing
a stoppage of pumping of the heart.
24. The step of delivering the electrical shock may include
delivering the electrical shock no longer than three seconds after
sensing the arrhythmia. The step of stimulating the spinal column
to produce an analgesic effect may include infusing an analgesic
drug or electrically stimulating a nerve immediately upon sensing
the arrhythmia.
25. The step of sensing the arrhythmia preferably allows sufficient
time to verify the stability of the arrhythmia. The step of
delivering the electrical shock may take up to one minute from
sensing the arrhythmia, and the electrical shock may be between 1
and 10 Joules. The step of stimulating the spinal column preferably
occurs at least two seconds before the electrical shock.
26. Alternatively, the arrhythmia may be ventricular tachycardia.
The step of sensing the arrhythmia may include sensing an
electrical signal from the heart beating up to 300 beats per
minutes, wherein the beats have substantially constant frequency
and amplitude, and further sensing an attenuated and/or irregular
blood flow without stoppage of the heart. A pacing electrical
stimulus may be applied as a first treatment and, if this is
unsuccessful after a programmed number of attempts, a low energy
cardioversion shock may be delivered.
27. The step of stimulating the spinal column may include infusing
an analgesic drug with immediate effect. The step of sensing the
arrhythmia may include sensing the arrhythmia through electrical,
mechanical, and electromechanical impulses.
BRIEF DESCRIPTION OF THE DRAWINGS
28. FIG. 1 is a block diagram showing the elements of the
defibrillating system
29. FIG. 2 is a block diagram describing an embodiment of the
system in greater detail.
30. FIG. 3 illustrates the time sequences of the interventions for
ventricular fibrillation of the various components which are
characteristic of the proposed system.
31. FIG. 4 illustrates the time sequences of the interventions for
atrial fibrillation of the various components which are
characteristic of the proposed system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
32. First of all, the case of ventricular fibrillation will be
considered; the following solutions are proposed:
33. a) to make a sure diagnosis within the first 1-2 seconds of the
start of the arrhythmia,
34. b) to deliver the electric shock no more than 3-4 seconds after
the recognition of the ventricular fibrillation so as to start the
shock when the patient is conscious and with less energy than is
currently used because of the earliness of the intervention,
and
35. c) in order to be able to operate as in b), to prevent the
patient's nervous system from receiving the pain stimulus due to
the electric shock and to the abrupt contraction of the adjacent
muscles. This can be achieved, for example, by the insertion of
electrodes in the spinal column, the electrodes being connected to
a nerve stimulator which will saturate the pain-conduction pathways
(gate effect), preventing the pain from being perceived by the
patient or, in any case, causing it to arrive greatly attenuated.
The same result can also be achieved, for example, by means of an
infusion pump which can send a drug which has an immediate effect
(e.g. a recently investigated drug, conopeptide, with effectiveness
100 times greater than morphine) to the appropriate sites of the
nerve endings affected by the shock in order to cancel out the
perception of the pain.
36. The instrument for implementing the system proposed is made up
essentially as shown by the simplified block diagram which shows
its main components.
37. In FIG. 1, the various blocks represent:
38. A sensors for detecting fibrillation,
39. B fibrillation or tachycardia recognition circuit,
40. C programmable nerve stimulator or analgesic drug infusion
pump,
41. D neural electrode system for the spinal column, or catheter
for the infusion of the analgesic drug,
42. E quickly prepared electric-shock generator, and
43. F defibrillation electrode system.
44. The sequence of operation is as follows. The circuit B
recognizes the presence of fibrillation by means of the sensors A
within a time no longer than 2 sec. When recognition has taken
place, a signal starts the nerve stimulator (or the infusion pump)
C which produces the gate effect in the nervous system involved in
receiving the expected pain signals, by means of the spinal
electrodes (or the infusion catheter) D. At the same time, the
quick shock-energy generator E charges the capacitor which stores
the energy within a time less than or equal to 3 sec. If the
circuit B confirms fibrillation, the discharge is delivered at a
time no longer than 4-5 sec. after recognition.
45. The solutions set out in points a), b) and c) described above
are thus achieved:
46. quick recognition of ventricular fibrillation;
47. immediate saturation of the pain-conduction pathways; and
48. defibrillation at times close to the onset of the arrhythmia,
within the first 5 seconds.
49. The various components of the proposed system can be formed by
solutions already existing in various implantable defibrillator
models and spinal-chord nerve stimulators (or drug infusers) which
have already been produced.
50. The detection of ventricular fibrillation with regard to its
electrical component has now been established and it is proposed
herein to supplement it by means of a second sensor, for example, a
mechanical sensor so as to be able to recognize the type of
arrhythmia with certainty within a very short time. The stimulation
parameters of nerve stimuli, which are generally used to treat
long-term pains, have to be adapted to the need to prevent the
propagation of a pain which is expected, sudden and of short
duration, at least with regard to its cause. Any infuser must be
designed to deliver an analgesic drug with immediate effect. The
generator and supplier of the electric shock must be put into
operation in a very short time as is, however, already provided for
in the latest generations of defibrillators. Naturally, the entire
device which forms the proposed system can preferably be fitted in
a single implantable container although this is not functionally
necessary as long as the various functions are interconnected
electrically or electromagnetically.
51. The block diagram of FIG. 2 will be considered in order to
describe a possible embodiment of the system in greater detail. The
sensors 1 and 2 constitute the arrhythmia detection and recognition
system. The electric sensor 1 analyses the electrical signal of the
heart which enables the presence of ventricular tachycardia to be
distinguished from ventricular fibrillation, by considering, for
example, the aroma frequency of the complexes and the regularity of
the period and amplitude of the heart signals. The electrical
diagnoses which, in some cases, could be uncertain, can be
confirmed with the use of a mechanical (or electromechanical)
signal, for measuring, for example, systolic pressure, which is
practically zero in ventricular fibrillation, or contractility,
which is easily detectable by means of recently-proposed
implantable transducers, or by rheography, or heart noise.
Reference may be made, for example, to the documents EP-A-0 515
319, EP-A-0 582 162, EP-A-0 655 260, EP-A-0 770 406 and EP-A-0 778
049.
52. The algorithm which can be implemented with systems of this
type enables ventricular tachycardia to be distinguished from
ventricular fibrillation; in fact in ventricular tachycardia,
neither the pressure nor the contractility become zero, although
their values are much lower than the normal sine function and
amplitude and frequency may be irregular; with ventricular
fibrillation, on the other hand, the pressure and contractility
fall practically and abruptly to zero and the heart noise is almost
non-existent.
53. The circuit represented by block 3 is provided for processing
the data obtained by 1 and 2 by an algorithm which, as stated
above, recognizes the type of arrhythmia, providing a signal
indicating the presence of ventricular fibrillation or ventricular
tachycardia to downstream circuits. If the arrhythmia recognized is
ventricular fibrillation the proposed system starts block 4 and
block 8 together.
54. In this embodiment, block 4 represents, by way of non-limiting
example, the nerve stimulator assembly the stimulating electrodes 6
of which are inserted in the spinal chord in positions in which the
closure of the gate will cancel out the transmission of the pain
signals coming from the heart region and from the surrounding
muscles. The drug infuser may be used in similar manner. The
functional characteristics of block 4 are known to experts in the
art and are programmed in a manner such that the nerve stimulation
effect is immediate (usually from 0.5 to 1 sec. delay) and
effective for the region affected.
55. Block 8 represents the system for the storage of the shock
energy, which consists in charging a capacitor such as that
normally used in ICDs, contained in block 9. The main
characteristic of block 8 is that it can charge the capacitor,
which usually has a capacitance of between 80 and 180 .mu.F, to the
maximum energy of 25-30 J within a time less than or equal to 3
seconds. The short charging time is important for the purposes of
the invention; it has already been achieved in the design of
implantable defibrillators currently in production.
56. The circuit 5 confirms the presence of ventricular fibrillation
about 4-5 seconds after the recognition effected by 3. In this
case, the circuit of block 9 provides for the emission of a shock
with the electrical characteristics (wave-form, duration, etc.)
required and programmed by the operator. The shock is delivered by
means of the electrode system (endocavitary or epicardial) 11 which
comprises the defibrillation electrodes and those for the
pre-selected programmed stimulation for any ventricular
tachycardia.
57. In fact, if the arrhythmia is recognized as ventricular
tachycardia, a signal is sent to block 10 which comprises a
programmable anti-tachycardia stimulator which can deliver the
pre-selected stimulation program for tachyarrhythmia and implement
the algorithms normally used for this treatment such as, for
example, burst, premature extra-stimuli, overdrive. Block 10 is
also capable of delivering a normal stimulation in the event of
stoppage or asystole after defibrillation or cardioversion so as to
promote the re-establishment of a possible sinusoidal rhythm. The
programmed stimulation is delivered by means of the electrode
system 11.
58. Block 7 consists of a circuit provided for creating blanking
which electrically excludes both the anti-arrhythmic pacemaker 10
and the nerve stimulator 4 from normal operation in order, as far
as possible, to protect the electronic circuits from the shock of
the defibrillation signal which could damage them because of its
high energy. The blanking signal is applied for a time slightly
greater than the total duration of the shock pulse; a duration of
about 20-30 mseconds, starting from the leading edge of the shock
itself or a few mseconds earlier, will normally suffice. For the
same reason and as is normally the case, the electrode systems 1, 2
and 6 must be protected from discharges greater than about 20
Volts, for example, by means of semiconductor devices well known in
electronics.
59. The system proposed up to now can also be used with a few
modifications in the case of atrial fibrillations. In this case,
there is no need for early intervention, since this arrhythmia is
disabling but not fatal. It is, however, important to try to
prevent the painful sensation caused by the electric shock since
this will take place when the patient is conscious. In the case of
atrial cardioversion, the difference factors also render the
production of the cardioverter easier and less critical. The energy
required for atrial cardioversion is much lower than that required
for ventricular defibrillation; normally from 1 to 10 Joules
suffices. The charging of the capacitor for the shock can take
place over longer periods, thus requiring a lower charge-generator
power. To prevent pro-arrhythmic effects which could lead to
ventricular fibrillation owing to the delivery of the shock in the
period of ventricular vulnerability, the shock is synchronized with
the patient's QRS.
60. In view of the similarities between the two defibrillation
methods, it is thus possible to design a single device which can be
programmed with the two different algorithms, the sole change in
the hardware being in the electrode system 11 of FIG. 2. The time
sequences of the interventions of the various components which are
characteristic of the proposed system are shown schematically in
FIG. 3 for ventricular fibrillation and in FIG. 4 for atrial
fibrillation.
61. FIG. 3A describes operation during persistent ventricular
fibrillation. Recognition system 3 notices the ventricular
fibrillation at time 20 and immediately starts nerve stimulator 4
and the charging of capacitor 8. At the same time, checking system
5 checks that arrhythmia is present. Capacitor 8 will already be
charged at time 21. At time 32 programmed for the emission of the
shock, blanking circuit 7 protects the circuits with a signal of
duration 24 which is greater than discharge time 22, stimulator 4
also being prevented for the period 23. Immediately afterwards,
circuit 9 delivers shock 22 which should interrupt the ventricular
fibrillation. Nerve stimulator 4 will continue to protect the
patient from the pain for a programmable period which may be as
long as a few minutes.
62. FIG. 3B shows a case of ventricular fibrillation which
disappears naturally at a time earlier than that programmed for the
discharge. After the start at time 25 which triggers stimulator 4
and charging circuit 8, the ventricular fibrillation disappears at
time 26, and all of the circuits are reset.
63. FIG. 3C gives an example in which ventricular tachycardia
occurs. At time 27, circuit 3 recognizes the type of arrhythmia as
ventricular tachycardia and activates anti-arrhythmic stimulator
circuit 10 which starts to deliver stimuli in accordance with the
programmed algorithms.
64. If these stimuli are effective, the ventricular tachycardia
will be stopped and circuits 3 and 10 will be reset. If, however,
the treatment with anti-arrhythmic stimulator circuit 10 is not
effective, after the delivery of a certain number of programs (3-5
times in succession) circuit 3 will start both spinal cord
stimulator (SCS) generator 4 and the capacitor-charging circuit 8
at time 28 up to the time at which the programmed energy 25 is
reached. At the time 33, as in the case described in FIG. 3A,
blanking signal 31 will start and will protect the circuits of the
system during the shock for period 34. The delivery of shock 30
will cancel out the arrhythmia and the system will be reset.
65. FIG. 4 shows the sequence of operation of the various blocks in
the case of atrial fibrillation. Also this refers to FIG. 2.
66. Recognition system 3 detects atrial fibrillation at time 40. At
the same time, the charging of the capacitor by block 8 is started,
the programmed energy being reached after time 46 which may even be
one minute. At the same time, or at time 41 after the recognition
of the atrial fibrillation, nerve stimulator 4 starts the
stimulation. Checking system 5 checks the existence of atrial
fibrillation.
67. At time 42, a fraction of a second before the shock, the
blocking of the blanking unit is switched on for time 45 which
lasts until a few hundred milliseconds after the shock. During time
45, the circuits of blocks 3, 4 and 5 are prevented and/or
protected against the shock energy which is propagated through the
patient's body. During time 45, the cardioversion electric shock is
delivered and is synchronized with the patient's QRS by blocks 3
and 5. Circuits 3 and 5 then become active again in order to
monitor the patient and nerve stimulator 4 continues in accordance
with the program setting.
* * * * *