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Timestamp: 2014-07-25 17:28:12
Document Index: 244632332

Matched Legal Cases: ['art 12', 'art 12', 'art 12', 'art 12', 'art 12', 'art 12']

Heart Stimulator FreshPatents Stats115 views for this patent on FreshPatents.com2014: 4 views2013: 32 views2012: 43 views2011: 28 views2010: 6 views2008: 2 viewsUpdated: March 31 2014 TOP 200 Companies filing patents this week
05/15/08 | Class 607 Monitor | RSS | Industry | Agents | Inventors
Heart stimulator Title: Heart stimulator.Abstract: Heart stimulator that stimulates at least a heart's right atrium and ventricle in an atrium asynchronous stimulation mode with an overdrive stimulation rate. Interposes one resynchronization cycle after a sensed atrial event to regain AV synchrony during otherwise asynchronous stimulation mode. Allows for pacing mode that can pace the atrium with an overdrive stimulation rate in dual-chamber asynchronous mode while maintaining the AV synchrony and is called DDI(R)+. In DDI(R)+, pacemaker performs an atrial asynchronous (V synchronous) pacing mode such as DDI or DDI(R). The overdrive stimulation rate (OSR) is either a fixed rate (programmed by the external device) that is thought to be above the underlying intrinsic atrial rate, or is dynamically adjusted according to the measured atrial cycle length to be slightly above intrinsic atrial rate. The overdrive stimulation rate may be based on an intrinsic atrial rate or on hemodynamic need. DDI(R)+ timing may be ventricle-based. ...
- La Jolla, CA, USInventors: Jie Lian, Christopher S. de Voir, Garth Garner, Hannes Kraetschmer, Dirk MussigUSPTO Applicaton #: #20080114409 - Class: 607 17 (USPTO) - 05/15/08 - Class 607 The Patent Description & Claims data below is from USPTO Patent Application 20080114409, Heart stimulator.Atrium Hemodynamic Pacemaker Right Atrium Synchronous Mode BACKGROUND OF THE INVENTION
[0002]The invention refers to a heart stimulator for stimulating at least
one atrium and one ventricle of a heart by means of electrical
stimulation pulses in an overdrive mode of pacing wherein the atrium and
the ventricle are stimulated with an overdrive stimulation rate that is
thought to be higher than an intrinsic heart rate. More particular, the
invention is directed to dual-chamber (RA-RV), three-chamber (BiA-RV, or
RA-BiV), or four-chamber (BiA-BiV) implantable cardiac devices including
pacemakers, defibrillators and cardioverters, which stimulate cardiac
tissue electrically to control the patient's heart rhythm.
[0004]Implantable heart stimulators can be used for treating a variety of
heart disorders like bradycardia, tachycardia or fibrillation.
[0005]Depending on the disorder to be treated, such heart stimulator
generates electrical stimulation pulses that are delivered to the heart
tissue (myocardium) of a respective heart chamber according to an
adequate timing regime. Delivery of stimulation pulses to the myocardium
is usually achieved by means of an electrode lead that is electrically
connected to a stimulation pulse generator inside a heart stimulator's
housing and that carries a stimulation electrode in the region of it's
distal end. A stimulation pulse having strong enough strength causes an
excitation of the myocardium that in turn is followed by a contraction of
the respective heart chamber. A stimulation pulse also is called a pace.
Similarly, pacing a heart chamber means stimulating a heart chamber by
delivery of a stimulation pulse (pace).
[0006]In order to be able to sense a contraction a heart chamber that
naturally occurs without artificial stimulation and that is called
intrinsic, the heart stimulator usually comprises at least one sensing
stage that is connected to a sensing electrode on said electrode placed
in the heart chamber. An intrinsic excitation of a heart chamber results
in characteristic electrical potentials that can be picked up via the
sensing electrode and that can be evaluated by the sensing stage in order
to determine whether an intrinsic excitation--called: intrinsic
event--has occurred.
[0007]Usually, a heart stimulator features separate stimulation generators
for each heart chamber to be stimulated. Therefore, in a dual chamber
pacemaker, usually an atrial and a ventricular stimulation pulse
generator for generating atrial and ventricular stimulation pulses are
provided. Delivery of an atrial or a ventricular stimulation pulse
causing an artificial excitation of the atrium or the ventricle,
respectively, is called an atrial stimulation event AP (atrial paced
event) or a ventricular stimulation event VP (ventricular paced event),
[0008]Similarly, common heart stimulators feature separate sensing stages
for each heart chamber to be of interest. In a dual chamber pacemaker
usually two separate sensing stages, an atrial sensing stage and a
ventricular sensing stage, are provided that are capable to detect
intrinsic atrial events AS (atrial sensed event) or intrinsic ventricular
events VS (ventricular sensed event), respectively.
[0009]By means of a sensing stage for a heart chamber to be stimulated,
the pacemaker is able to only trigger stimulation pulses when needed that
is when no intrinsic excitation of the heart chamber occurs in time. Such
mode of pacing a heart chamber is called demand mode. In the demand mode
the pacemaker schedules an atrial or a ventricular escape interval that
causes triggering of an atrial or ventricular stimulation pulse when the
escape interval times out. Otherwise, if an intrinsic atrial or
ventricular event is detected prior to time out of the respective atrial
or ventricular escape interval, triggering of the atrial or ventricular
stimulation pulse is inhibited.
[0010]Depending upon which chambers of heart are stimulated and which
sense events are used different modes of stimulation become available.
These modes of stimulation are commonly identified by a three letter code
wherein the first letter identifies the chamber or chambers to be
stimulated such as V for a ventricle to be stimulated, A for an atrium to
be stimulated and D (dual) for both, ventricle and atrium to be
stimulated. Similarly, the second letter characterizes the chamber or
chambers sensed events may origin from (V: ventricle, A: atrium, D:
ventricle and atrium). The third letter characterizes the mode of
delivery of stimulation pulses: T=triggered, I=inhibited and D=dual
(T+I). A fourth letter "R" may characterize a rate adaptive heart
stimulator that comprises an activity sensor or some other means for
determining the hemodynamic need of a patient in order to adapt the
stimulation rate accordingly.
[0011]A dual chamber pacemaker featuring an atrial and a ventricular
sensing stage and an atrial and a ventricular stimulation pulse generator
can be operated in a number of stimulation modes like VVI, wherein atrial
sense events are ignored and no atrial stimulation pulses are generated,
but only ventricular stimulation pulses are delivered in a demand mode,
AAI, wherein ventricular sense events are ignored and no ventricular
stimulation pulses are generated, but only atrial stimulation pulses are
delivered in a demand mode, or DDD, wherein both, atrial and ventricular
stimulation pulses are delivered in a demand mode. In such DDD mode of
pacing, ventricular stimulation pulses can be generated in synchrony with
sensed intrinsic atrial events and thus in synchrony with an intrinsic
atrial rate, wherein a ventricular stimulation pulse is scheduled to
follow an intrinsic atrial contraction after an appropriate
atrioventricular delay (AV-delay; AVD), thereby maintaining the
hemodynamic benefit of atrioventricular synchrony.
[0012]In some cases, a DDI mode of stimulation may be adequate. In such
DDI mode, a ventricular stimulation pulse is not synchronized with a
preceding atrial sense event (not "triggered" by an atrial sense event).
However, both, atrium and ventricle, are stimulated in a demand mode
wherein stimulation pulses are inhibited if an intrinsic event is sensed
prior to time out of a respective escape interval.
[0013]In particular if an overdrive stimulation is needed, DDI mode pacing
may be adequate. When stimulating a heart with an overdrive stimulation
rate it is attempted to deliver a (premature) stimulation pulse prior to
a possible intrinsic excitation and thus render a respective heart
chamber refractory so that it is not susceptible to any further (natural)
excitation during a (natural) refractory period needed by the cells of
the myocardium to repolarize and thus become susceptible to further
excitation again.
[0014]Atrial overdrive pacing is useful in a number of applications.
[0015]One typical application is to prevent atrial fibrillation (AF).
Possible mechanisms by which atrial pacing may be effective include
suppression of premature supraventricular beats, elimination of delayed
atrial conduction, and atrial pauses that may trigger or facilitate
reentry circuits favoring the initiation of AF. Various algorithms have
been developed, including dynamic (permanent) atrial overdrive pacing,
post-AES (temporary) atrial rate stabilization, post-mode-switch
(temporary) overdrive pacing, etc.
[0016]Another application is for atrial capture verification during atrial
pacing threshold measurement. For patients with intact AV node, the
presence of a conducted ventricular sense (Vs) after a premature atrial
stimulation pulse (Ap) indicates that the atrial stimulation pulse was
strong enough to be effective and thus to cause "capture" of the atrium
whereas the absence of a ventricular sense event Vs after the atrial
stimulation pulse Ap indicates atrial non-capture. For patient without
intact AV node, the atrial non-capture can be suspected on the detection
of intrinsic atrial sense (As) after the atrial stimulation pulse Ap
since the atrial stimulation pulse was unable to render the atrial
myocardium refractory and thus to suppress intrinsic atrial excitation.
For both scenarios, atrial overdrive pacing above the intrinsic atrial
[0017]In a dual-chamber device, atrial overdrive pacing can be achieved in
both DDD(R) mode and DDI(R) mode. The DDD(R) mode is useful to maintain
the AV synchrony during atrial overdrive pacing, but has intrinsic risk
of pacemaker-mediated tachycardia (PMT). On the other hand, the DDI(R)
mode is free of PMT but may also lose the hemodynamic benefit of AV
[0018]Therefore, there is a need to implement the atrial overdrive pacing
in DDI(R) mode (thus eliminate the risk of PMT) while still maintaining
the AV synchrony (thus enjoy the associated hemodynamic benefits).
[0019]For the purpose of this disclosure, the following abbreviations are
AES Atrial extrasystole
Ap Atrial pace event
Ars Atrial refractory sense
A Any atrial event
AsVI The interval measured from the As to the following Vp or
AUI Atrial upper interval
AVD AV delay as applied by the pacemaker (in contrast to
FFPW Far field protection window after Vs or Vp
MS Mode switch
ODI Overdrive pacing interval (s): ODI = 60/OSR
OSR Overdrive stimulation rate (ppm): OSR = 60/ODI
PMT Pacemaker mediated tachycardia
PVAB Post-ventricular atrial blanking period
PVARP Post-ventricular atrial refractory period
Re-Sync Re-synchronization pacing cycle in DDI(R)+ mode
SW Safety window
VAI VA interval (duration of the VA timer)
VES Ventricular extra-systole
V Any ventricular event
[0020]According to the present invention the object of the invention is
achieved by a heart stimulator featuring:
[0021]at least one sensing stage connected or being connectable to an
electrode lead comprising an electrode for picking up electric potentials
inside at least one atrium and one ventricle of a heart, said sensing
stage being adapted to sense an excitation or a contraction of a heart
[0022]at least one stimulation pulse generator adapted to generate
electric stimulation pulses and being connected or being connectable to
an electrode lead comprising a stimulation electrode for delivering
electric stimulation pulses to at least said atrium and said ventricle of
[0023]a control unit that is connected to said sensing stage and to said
stimulation pulse generator.
[0024]The control unit is adapted:
[0025]to trigger stimulation pulses that are generated by the stimulation
pulse generator and that are to be delivered via said electrode lead,
[0026]to perform at least a DDI mode of pacing,
[0027]wherein atrial and ventricular stimulation pulses are triggered in
an atrium asynchronous manner when a respective atrial or ventricular
escape interval times out because no intrinsic atrial or ventricular
contraction is sensed during said atrial or ventricular escape interval,
[0028]wherein triggering of an atrial or a ventricular stimulation pulse
is inhibited, when an intrinsic atrial or ventricular contraction,
respectively, is sensed prior to time out of the respective atrial or
ventricular escape interval,
[0029]and wherein the atrial and the ventricular escape interval
correspond to an overdrive stimulation rate, that is thought to be higher
than an intrinsic heart rate,
[0030]and to resynchronize said ventricular escape interval and said
atrial escape interval during said DDI mode of pacing with an intrinsic
heart rhythm when an intrinsic atrial event AS is sensed prior to time
out of an atrial escape interval.
[0031]Generally, the objective of the invention is solved by a heart
stimulator that is adapted to stimulate at least a right atrium and a
right ventricle of a heart in an atrium asynchronous stimulation mode
with an overdrive stimulation rate, wherein the heart stimulator is
further adapted to interpose one resynchronization cycle after a sensed
atrial event in order to regain AV synchrony during the otherwise
asynchronous stimulation mode.
[0032]The pacemaker according to the invention allows for a pacing mode
that can pace the atrium with an overdrive stimulation rate in
dual-chamber asynchronous mode while maintaining the AV synchrony. This
mode is called DDI(R)+ mode for the purpose of present disclosure.
[0033]In DDI(R)+, the pacemaker performs an atrial asynchronous (V
synchronous) pacing mode such as DDI or DDI(R). The overdrive stimulation
rate (OSR) is either a fixed rate (programmed by the external device)
that is thought to be above the underlying intrinsic atrial rate, or is
dynamically adjusted according to the measured atrial cycle length so
that it is slightly above the intrinsic atrial rate. Corresponding to the
overdrive stimulation rate. ODI is an overdrive stimulation interval that
determines the duration of one stimulated heart cycle and is reciprocal
to the overdrive stimulation rate: ODI=60/OSR.
[0034]Preferably, the control unit is adapted to adjust the overdrive
stimulation rate based on an intrinsic atrial rate sensed via the sensing
stage such that the overdrive stimulation rate is higher than said sensed
intrinsic atrial rate prior to performing the DDI mode of pacing with
that overdrive rate.
[0035]Alternatively, the control unit may be adapted to adjust the
overdrive stimulation rate based on an activity signal determined by
means of an activity sensor such that the overdrive stimulation rate is
higher than an adapted heart rate corresponding to a hemodynamic need
that corresponds to the activity as determined by the activity sensor.
[0036]In a preferred embodiment, the timing cycle of DDI(R)+ is
ventricle-based.
[0037]Accordingly it is preferred that the ventricular escape interval is
a VV-interval started by a ventricular event, said VV-interval being
reciprocal to the overdrive stimulation rate.
[0038]Similarly, it is preferred that the atrial escape interval is a
VA-interval started by a ventricular event. The atrial escape interval
preferably is a VA-interval that corresponds to: VAI=VV-AVD wherein AVD
is a predetermined atrioventricular delay interval. The atrioventricular
delay interval AVD preferably is adjustable.
[0039]In such pacemaker, like in a conventional DDI(R) mode, after each
used ventricular event (Vs or Vp), a VV timer setting the ventricular
escape interval is started with duration of ODI. The ventricular
stimulation pulse Vp will be inhibited if there is a used (not ignored)
ventricular sense event Vs prior to the timeout of the VV timer,
otherwise a ventricular stimulation pulse Vp will be delivered at the
timeout of the VV timer. The ventricular escape interval is the VV
interval that equals the overdrive interval ODI. Meanwhile, after each
used ventricular event (Vs or Vp), a VA timer defining the atrial escape
interval is started with duration of VAI=ODI-AVD, where AVD is a
programmed AV delay (or may be dynamically adjusted by other features).
The atrial stimulation pulse Ap will be inhibited if there is a used
atrial sense event As prior to the timeout of the VA timer, otherwise the
atrial stimulation pulse Ap will be delivered at the timeout of the VA
timer (with VA interval=ODI-AVD). Ideally, the ODI should be shorter than
the intrinsic atrial cycle length to achieve overdrive pacing of the
atrium. The ODI can be a programmed value, or can be dynamically adjusted
according to the measured atrial rate or the sensor indicated rate, see
[0040]As long as atrium is continuously overdriven, the operation of
DDI(R)+ is identical to conventional DDI(R).
[0041]The key difference is when an atrial stimulation pulse Ap is
inhibited by a used As, that is, when the atrial overdrive is lost. After
a used As, the device triggers a Re-Sync cycle and starts monitoring the
following ventricular event (Vs or Vp). Upon detection of the following
ventricular event, the Re-Sync cycle is implemented so that the following
VV interval and VA interval are recalculated based on the just measured
AV interval. By this means, the device tries to regain control of the
atrial overdrive pacing. Alternatively, the Re-Sync cycle can also be
triggered by an Ars detected during the late PVARP. The Re-Sync cycle
will be implemented if the Ars is followed by a conducted ventricular
sense event Vs within a predefined AV control time. Otherwise, the
Re-Sync cycle will be discarded.
[0042]Accordingly, it is preferred, that the control unit is adapted to
resynchronize said ventricular escape interval and said atrial escape
interval by recalculating said ventricular escape interval and said
atrial escape interval based on an ASV-Interval, which begins with said
intrinsic atrial event AS that triggered resynchronization and which end
with the following ventricular event V.
[0043]The Re-Sync cycle is re-triggerable. That is, after an Ars or As
triggers a Re-Sync cycle, if there is another Ars or As before the
detection of the ventricular event, the second Ars or As will re-trigger
the Re-Sync cycle. By this means, upon detection of the following
ventricular event, the latest Ars or As will be based upon to measure the
AV interval, which is used for the re-calculation of the VV interval and
the VA interval to implement the Re-Sync cycle.
[0044]Several additional features are added to handle special conditions,
such as safety window (SW) Vs and Vp, atrial upper interval (AUI), upper
rate limit (URL), ventricular extra-systole (VES), high
atrial/ventricular rate detection, etc.
[0045]The details of the DDI(R)+ feature can be understood from the
following drawings and the corresponding text descriptions.
[0046]The above and other aspects, features and advantages of the present
description thereof, presented in conjunction with the following drawings
[0047]FIG. 1 shows a dual chamber pacemaker connected to leads placed in a
[0048]FIG. 2 is a block diagram of a heart stimulator according to the
[0049]FIG. 3 is a diagram illustrating a typical cycle of DDI(R)+ where
both atrium and ventricle are overdriven.
[0050]FIG. 4 is a diagram illustrating 3 cycles of DDI(R)+ where both
atrium and ventricle are overdriven and there is an incidental SW Vs and
SW Vp.
[0051]FIG. 5 is a diagram illustrating DDI(R)+ where both atrium and
ventricle are overdriven and there is a used As that triggers the Re-Sync
[0052]FIG. 6 is a diagram illustrating DDI(R)+ where both atrium and
ventricle are overdriven and a used As triggers the Re-Sync cycle whose
cycle length is limited by the URL.
[0053]FIG. 7 is a diagram illustrating DDI(R)+ where both atrium and
ventricle are overdriven and there is a VES and two Ars events without
causing AUI violation.
[0054]FIG. 8 is a diagram illustrating DDI(R)+ where both atrium and
ventricle are overdriven and an Ars triggers the Re-Sync cycle and the
conducted ventricular sense event Vs implements the Re-Sync cycle.
[0055]FIG. 9 is a diagram illustrating one cycle of DDI(R)+ where both
atrium and ventricle are overdriven and one Ars causes rescheduling of
the following Ap and Vp to avoid AUI violation.
[0056]FIG. 10 is a diagram illustrating DDI(R)+ where both atrium and
ventricle are overdriven and one Ars causes rescheduling of the following
Ap and Vp to avoid AUI violation while another used As triggers a Re-Sync
[0057]FIG. 11 is a diagram illustrating a typical cycle of DDI(R)+ where
atrium is overdriven followed by conducted Vs.
[0058]FIG. 12 is a diagram illustrating 3 cycles of DDI(R)+ where atrium
is overdriven followed by conducted Vs and there is an incidental SW Vs
and SW Vp.
[0059]FIG. 13 is a diagram illustrating DDI(R)+ where conducted Vs
accompany the atrial overdrive pacing and there is a used As that
triggers the Re-Sync cycle.
[0060]FIG. 14 is a diagram illustrating DDI(R)+ where conducted Vs
triggers the Re-Sync cycle whose cycle length is limited by the URL.
[0061]FIG. 15 is a diagram illustrating DDI(R)+ where conducted Vs
accompany the atrial overdrive pacing and an Ars after VES triggers the
Re-Sync cycle and the conducted Vs implements the Re-Sync cycle.
[0062]FIG. 16 is a diagram illustrating DDI(R)+ where conducted Vs
accompany the atrial overdrive pacing and an Ars after VES that causes
rescheduling of the following Ap and Vp to avoid AUI violation.
[0063]FIG. 17 is a diagram illustrating DDI(R)+ where both conducted Vs
and Vp may accompany the atrial overdrive pacing.
[0064]FIG. 18 is a diagram illustrating DDI(R)+ where atrial overdrive
pacing is lost due to a transient increase of the atrial rate.
[0065]The following description is of the best mode presently contemplated
for carrying out the invention. This description is not to be taken in a
limiting sense, but is made merely for the purpose of describing the
determined with reference to the claims.
[0066]In FIG. 1 a dual chamber pacemaker 10 as heart stimulator connected
to pacing/sensing leads placed in a heart 12 is illustrated. The
pacemaker 10 is electrically coupled to heart 12 by way of leads 14 and
16. Lead 14 has a pair of right atrial electrodes 18 and 20 that are in
contact with the right atria 26 of the heart 12. Lead 16 has a pair of
electrodes 22 and 24 that are in contact with the right ventricle 28 of
heart 12. Electrodes 18 and 22 are tip-electrodes at the very distal end
of leads 14 and 16, respectively. Electrode 18 is a right atrial tip
electrode RA-Tip and electrode 22 is a right ventricular tip electrode
22. Electrodes 20 and 24 are ring electrodes in close proximity but
electrically isolated from the respective tip electrodes 18 and 22.
Electrode 20 forms a right atrial ring electrode RA-Ring and electrode 24
forms a right ventricular ring electrode RV-Ring.
[0067]Referring to FIG. 2 a simplified block diagram of a dual chamber
pacemaker 10 is illustrated. During operation of the pacemaker leads 14
and 16 are connected to respective output/input terminals of pacemaker 10
as indicated in FIG. 1 and carry stimulating pulses to the tip electrodes
18 and 22 from an atrial stimulation pulse generator A-STIM and a
ventricular pulse generator V-STIM, respectively. Further, electrical
signals from the atrium are carried from the electrode pair 18 and 20,
through the lead 14, to the input terminal of an atrial channel sense
amplifier A-SENSE; and electrical signals from the ventricles are carried
from the electrode pair 22 and 24, through the lead 16, to the input
terminal of a ventricular sense channel amplifier V-SENSE.
[0068]Controlling the dual chamber pacer 10 is a control unit CTRL that is
connected to sense amplifiers A-SENSE and V-SENSE that form respective
sensing stages and to stimulation pulse generators A-STIM and V-STIM.
Control unit CTRL receives the output signals from the atrial sense
amplifier A-SENSE and from the ventricular sense amplifier V-SENSE. The
output signals of sense amplifiers A-SENSE and V-SENSE are generated each
time that a P-wave representing an intrinsic atrial event or an R-wave
representing an intrinsic ventricular event, respectively, is sensed
within the heart 12. An As-signal is generated, when the atrial sense
amplifier A-SENSE detects a P-wave and a Vs-signal is generated, when the
ventricular sense amplifier V-SENSE detects an R-wave.
[0069]Control unit CTRL also generates trigger signals that are sent to
the atrial stimulation pulse generator A-STIM and the ventricular
stimulation pulse generator V-STIM, respectively. These trigger signals
are generated each time that a stimulation pulse is to be generated by
the respective pulse generator A-STIM or V-STIM. The atrial trigger
signal is referred to simply as the "A-pulse", and the ventricular
trigger signal is referred to as the "V-pulse". During the time that
either an A-pulse or V-pulse is being delivered to the heart, the
corresponding sense amplifier, A-SENSE and/or R-SENSE, is typically
disabled by way of a blanking signal presented to these amplifiers from
the control unit CTRL, respectively. This blanking action prevents the
sense amplifiers A-SENSE and V-SENSE from becoming saturated from the
relatively large stimulation pulses that are present at their input
terminals during this time. This blanking action also helps prevent
residual electrical signals present in the muscle tissue as a result of
the pacer stimulation from being interpreted as P-waves or R-waves.
[0070]Furthermore, atrial sense events As recorded shortly after delivery
of a V-pulses during a preset time interval called post ventricular
atrial refractory period (PVARP) are generally recorded but ignored. Such
atrial sense event during PVARP is marked Ars herein after.
[0071]Control unit CTRL comprises circuitry for timing ventricular and/or
atrial stimulation pulses according to an adequate stimulation rate that
can be adapted to a patient's hemodynamic need as pointed out below.
[0072]Still referring to FIG. 2, the pacer 10 may also include a memory
circuit MEM that is coupled to the control unit CTRL over a suitable
data/address bus ADR. This memory circuit MEM allows certain control
parameters, used by the control unit CTRL in controlling the operation of
the pacemaker 10, to be programmably stored and modified, as required, in
order to customize the pacemaker's operation to suit the needs of a
particular patient. Such data includes the basic timing intervals used
during operation of the pacemaker. Further, data sensed during the
operation of the pacer may be stored in the memory MEM for later
[0073]A telemetry circuit TEL is further included in the pacemaker 10.
This telemetry circuit TEL is connected to the control unit CTRL by way
of a suitable command/data bus. Telemetry circuit TEL allows for wireless
data exchange between the pacemaker 10 and some remote programming or
analyzing device which can be part of a centralized service center
serving multiple pacemakers.
[0074]The pacemaker 10 in FIG. 1 is referred to as a dual chamber
pacemaker because it interfaces with both the right atrium 26 and the
right ventricle 28 of the heart 12. Those portions of the pacemaker 10
that interface with the right atrium, e.g., the lead 14, the P-wave sense
amplifier A-SENSE, the atrial stimulation pulse generator A-STIM and
corresponding portions of the control unit CTRL, are commonly referred to
as the atrial channel. Similarly, those portions of the pacemaker 10 that
interface with the right ventricle 28, e.g., the lead 16, the R-wave
sense amplifier V-SENSE, the ventricular stimulation pulse generator
V-STIM, and corresponding portions of the control unit CTRL, are commonly
referred to as the ventricular channel.
[0075]In order to allow rate adaptive pacing in a DDDR or a DDIR mode, the
pacemaker 10 further includes a physiological sensor ACT that is
connected to the control unit CTRL of the pacemaker 10. While this sensor
ACT is illustrated in FIG. 2 as being included within the pacemaker 10,
it is to be understood that the sensor may also be external to the
pacemaker 10, yet still be implanted within or carried by the patient. A
common type of sensor is an activity sensor, such as a piezoelectric
crystal, mounted to the case of the pacemaker. Other types of physiologic
sensors are also known, such as sensors that sense the oxygen content of
blood, respiration rate, pH of blood, body motion, and the like. The type
of sensor used is not critical to the present invention. Any sensor
capable of sensing some physiological parameter relatable to the rate at
which the heart should be beating can be used. Such sensors are commonly
used with "rate-responsive" pacemakers in order to adjust the rate of the
pacemaker in a manner that tracks the physiological needs of the patient.
[0076]Now the operation of pacemaker 10 during the DDI(R)+ mode shall be
[0077]The DDI(R)+ mode allows effective atrial overdrive pacing. The
ventricle can be overdriven as well with short AVD (e.g., 70 ms or
adaptively adjust to shorter than the measured intrinsic AV conduction
time, or in the case of AV block). This allows simultaneous overdrive
pacing in both atrium and ventricle. This is particularly useful for
situations that prefer ventricular pacing such as for patients with
hypertrophic obstructive cardiomyopathy, or in cardiac resynchronization
therapy (CRT). On the other hand, conducted ventricular events (Vs) can
be preserved by programming a long AVD (e.g., 250 ms or adaptively adjust
to longer than the measured intrinsic AV conduction time that is the
natural atrialventricular time delay). This is particularly useful to
minimize right ventricular pacing, which has been demonstrated to be
associated with hemodynamic deterioration and potential proarrhythmic
effect. When programming a moderate AVD that is comparable to the
intrinsic AV conduction time, both Vs and Vp may follow the atrial
stimulation pulse Ap. The DDI(R)+ mode supports all above conditions.
[0078]In the following, we first consider the conditions that both atrium
and ventricle are overdriven with a short AVD. Then we consider the
conditions that atrium is overdriven while conducted Vs is encouraged by
programming a long AVD. Condition that Vs and Vp are mixed with moderate
AVD is also discussed.
[0079]Refer to FIG. 3. Both atrium and ventricle are overdriven at a cycle
length ODI with a short AVD. After each ventricular stimulation pulse Vp,
a VV timer and a separate VA timer start. The VV timer times out after
duration of the overdrive interval ODI after which another ventricular
stimulation pulse Vp will be delivered. The VA timer times out after
duration of VAI=ODI-AVD, after which another atrial stimulation pulse Ap
will be delivered. As known in the art, the timing control is typical of
the conventional DDI(R) mode. As known in the art, the PVARP after a
ventricular stimulation pulse Vp can be a programmed value, or can be
dynamically adjusted based on the measured heart rate. In a typical
embodiment, the PVARP after ventricular stimulation pulse Vp contains an
early portion of the post ventricular atrial blanking period PVAB where
atrial sensing is blanked, an intermediate far field protection window
FFPW where sensed atrial event is recorded but ignored, and a late PVARP
window where any sensed atrial event is declared as atrial refractory
sense event (Ars).
[0080]Refer to FIG. 4. Similarly, both atrium and ventricle are overdriven
at a cycle length ODI with a short AVD. After the third atrial
stimulation pulse Ap, there is a ventricular sense event Vs sensed during
a safety window SW followed by a committed SW Vp. As a result, the
interval from the second ventricular stimulation pulse Vp to the
ventricular sense event Vs during the safety window SW is slightly less
than ODI. After the SW Vp, the VV timer (with duration ODI) and VA timer
(with duration ODI-AVD) start, and the atrium and ventricle are again
overdriven with specified ODI.
[0081]Refer to FIG. 5. Again, both atrium and ventricle are overdriven at
a cycle length ODI with a short AVD. After the second atrial stimulation
pulse Ap, there is a used atrial sense event As (outside PVARP) that
inhibits the scheduled atrial stimulation pulse Ap, and the Ap-As
interval is shorter than ODI. This used As could be an atrial
extrasystole AES, or an incidental atrial noise sense, or an intrinsic
atrial depolarization due to subthreshold pacing of the second atrial
stimulation pulse Ap, or an indication of transiently accelerated atrial
rate such as due to enhanced heart rate variability or onset of proximal
atrial tachycardia. Upon detection of the used atrial sense event As, a
Re-Sync cycle is triggered, and the device starts to monitor the
following ventricular event. Upon the detection of the following
ventricular event, either Vs or Vp (a ventricular stimulation pulse Vp is
shown in this example), the Re-Sync cycle is implemented. The
implementation of the Re-Sync cycle is achieved by first measuring the
interval between used atrial sense event As and the ventricular event V,
AsVI. Then the VV timer and the VA timer are started with re-calculated
intervals for this Re-Sync cycle. For the VV timer, the duration is
calculated as: VVresync=max(ODI-AsVI+AVD, URL) with URL being an upper
rate limit that is the shortest ventricular pacing interval at an upper
stimulation rate limit. URL is not a rate but an interval although the
name of this interval would indicate the opposite. For the VA timer, the
duration is calculated as: VAresync=VVresync-AVD=max(ODI-AsVI, URL-AVD).
As noted, the shortest ventricular pacing interval for the Re-Sync cycle
is limited to URL. If there is no URL violation, then the closing atrial
stimulation pulse Ap for the Re-Sync cycle will ensure the As-Ap interval
equals ODI. By applying ODI coupled to the used As, the device can
immediately regain control of the atrial overdrive. While the ventricular
interval for the Re-Sync cycle is shorter than ODI, the closing
ventricular stimulation pulse Vp for the Re-Sync cycle is coupled to the
closing atrial stimulation pulse Ap, thus AV synchrony is maintained.
After the Re-Sync cycle, the durations for the VV timer and VA timer are
restored to their original values, so that both atrium and ventricle are
continuously overdriven at the cycle length ODI. Also note that for fixed
PVARP, because the used As is outside PVARP (i.e., AsVI<ODI-PVARP),
the closing atrial stimulation pulse Ap also falls outside the PVARP
(VAresync=ODI-AsVI>PVARP).
[0082]Refer to FIG. 6. Similar to the example shown in FIG. 5, one used
atrial sense event As triggers a Re-Sync cycle, and the following
ventricular event V (Vp in this example) implements the Re-Sync cycle.
However, in this example, it is found that (ODI-AsVI+AVD) is less than
URL. Therefore, the duration of the VV timer is limited to URL, and the
VA timer duration is set to (URL-AVD). As a result, the interval between
the used As and the closing atrial stimulation pulse Ap for this Re-Sync
cycle is longer than ODI.
[0083]Refers to FIG. 7. A ventricular extrasystole VES occurs while
applying overdrive pacing to both atrium and ventricle. In a typical
embodiment, the sensed ventricular event is declared as VES if it is not
preceded by a used atrial event A (e.g., As outside PVARP or Ap). The VES
starts a PVARP window that may have the same or different duration than
the PVARP after a ventricular stimulation pulse Vp. The VES also resets
the VV timer and VA timer, while the duration of each timer is unchanged.
Also shown in this example are two refractory atrial sense events (Ars)
that occur during the PVARP. The Ars could be a far-field sensing of the
ventricular event, or a retrograde As due to ventricular stimulation
pulse Vp or VES, or an atrial noise sense, or an intrinsic atrial
depolarization due to sub-threshold pacing of the previous atrial
stimulation pulse Ap. Upon detection of the Ars, the device calculates
the interval from the Ars to the next scheduled atrial stimulation pulse
Ap. As long as the calculated interval is longer than the programmed
atrial upper interval (AUI, preferably 250 or 300 ms), there is no change
on the VA timer duration or the VV timer duration.
[0084]Refer to FIG. 8. In another embodiment, the sensed ventricular event
can be declared as conducted ventricular sense event Vs if it is preceded
by an Ars and the interval between Ars and Vs is within a predefined
range, termed AV control time, preferably 150 ms-300 ms. This could
happen if an AES occurs in the late PVARP and conducts to the ventricle
as the example shown in FIG. 8. Accordingly, the Ars also triggers a
Re-Sync Cycle, and the conducted ventricular sense event Vs implements
the Re-Sync cycle. If there is no URL violation, then the closing atrial
stimulation pulse Ap for the Re-Sync cycle will ensure the Ars-Ap
interval equals ODI. By applying ODI coupled to the Ars, which is most
likely an AES because of the following conducted ventricular sense event
Vs, the device can immediately regain control of the atrial overdrive. On
the other hand, if there is no detected ventricular sense event Vs within
the AV control time, then the Re-Sync cycle is discarded.
[0085]Refer to FIG. 9. An Ars occurs while applying overdrive pacing to
both atrium and ventricle. In this example, however, the interval from
the Ars to the scheduled atrial stimulation pulse Ap is shorter than AUI.
Upon detection of the AUI violation, the following atrial stimulation
pulse Ap is delayed so that the Ars-Ap interval is equal to AUI.
Correspondingly, the following ventricular stimulation pulse Vp is also
rescheduled so that its interval to the Ars equals (AUI+AVD). The purpose
of AUI is to prevent atrial stimulation pulse Ap being delivered during
the atrial vulnerable period if the Ars is caused by an intrinsic atrial
[0086]Refer to FIG. 10. Similar to the example shown in FIG. 9, an Ars
occurs while applying overdrive pacing to both atrium and ventricle and
the following atrial stimulation pulse Ap and ventricular stimulation
pulse Vp are postponed to avoid AUI violation. Because of the delayed
atrial stimulation pulse Ap, there is a possibility for the occurrence of
an intrinsic As that inhibits the rescheduled atrial stimulation pulse Ap
(due to prolonged Ap-Ap interval), particularly if the Ars is not an
intrinsic atrial event (e.g., due to noise sense or far-field sense). As
in FIG. 5 and FIG. 6, this used As triggers a Re-Sync cycle, and the
following ventricular event (Vp in this example) implements the Re-Sync
cycle by recalculating the VV timer and the VA timer. Similarly, when
atrial stimulation pulse Ap and ventricular stimulation pulse Vp are
postponed in order to avoid URL violation (as the example shown in FIG.
6), there is also a possibility for the occurrence of an intrinsic As
that inhibits the rescheduled atrial stimulation pulse Ap. As expected,
such a used As will also trigger a Re-Sync cycle and the following
ventricular event will implement the Re-Sync cycle in the same manner.
[0087]Now refer to FIG. 11. In this example, a long AVD is programmed and
the patient has intact AV conduction. As a result, the atrium is
overdriven while each atrial stimulation pulse Ap is followed by a
conducted ventricular sense event Vs. After each ventricular sense event
Vs, a VV timer starts with duration of ODI, and a VA timer starts with
duration of (ODI-AVD). However, because atrial stimulation pulse Ap is
followed by conducted ventricular sense event Vs which inhibits the
scheduled ventricular stimulation pulse Vp, the Ap-Vs interval is shorter
than AVD. Consequently, the effective Ap-Ap interval and the measured
Vs-Vs interval are slightly shorter than ODI (by a difference of AVD
minus the Ap-Vs interval). As known in the art, the PVARP after
ventricular sense event Vs is usually different than the PVARP after
ventricular stimulation pulse Vp. In a typical embodiment, the PVARP
after ventricular sense event Vs is also the FFPW where sensed atrial
events are ignored.
[0088]Refer to FIG. 12. Similarly, conducted ventricular sense event Vs
accompany atrial overdrive pacing. After the third atrial stimulation
pulse Ap, there is a SW Vs which is followed by a committed SW Vp. After
the SW Vp, the VV timer (with duration ODI) and the VA timer (with
duration ODI-AVD) start. The atrium is continually overdriven with an
effective pacing interval slightly shorter than ODI, and conducted
ventricular sense event Vs follows the atrial stimulation pulse Ap. Note
that in this example, the PVARP after ventricular sense event Vs is
shorter than the PVARP after the SW Vp.
[0089]Refer to FIG. 13. Again, conducted ventricular sense event Vs
accompany atrial overdrive pacing. After the second atrial stimulation
pulse Ap, there is a used As that inhibits the scheduled atrial
stimulation pulse Ap. Similar to the case shown in FIG. 5, upon detection
of the used As, a Re-Sync cycle is triggered, and the device starts to
monitor the following ventricular event. Upon the detection of the
following Vs or Vp (a ventricular sense event Vs is shown in this
example), the Re-Sync cycle is implemented. The implementation of the
Re-Sync cycle is the same as described above. That is, the interval
between used As and the ventricular event, AsVI, is measured. The
durations for the VV timer and the VA timer are re-calculated as:
VVresync=max(ODI-AsVI+AVD, URL) and VAresync=VVresync-AVD=max(ODI-AsVI,
URL-AVD). As noted, the shortest ventricular pacing interval for the
Re-Sync cycle is limited to URL. If there is no URL violation, then the
closing atrial stimulation pulse Ap for the Re-Sync cycle will ensure the
As-Ap interval equals to ODI. By applying ODI coupled to the used As, the
device can immediately regain control of the atrial overdrive. Similarly,
the closing ventricular stimulation pulse Vp for the Re-Sync cycle is
coupled to the closing atrial stimulation pulse Ap, thus the AV synchrony
is maintained. After the Re-Sync cycle, the durations for the VV timer
and VA timer are restored to their original values, so that atrium is
continuously overdriven while conducted ventricular sense event Vs is
allowed. Also note that for fixed PVARP, because the used As is outside
PVARP (i.e., AsVI<ODI-PVARP), the closing atrial stimulation pulse Ap
also falls outside the PVARP (VAresync=ODI-AsVI>PVARP).
[0090]Refer to FIG. 14. Similar to the example shown in FIG. 13, one used
As triggers a Re-Sync cycle, and the following ventricular event (Vp in
this example) implements the Re-Sync cycle. However, in this example, it
is found that (ODI-AsVI+AVD) is less than URL. Therefore, the duration of
the VV timer is limited to URL, and the VA timer duration is set to
(URL-AVD). As a result, the interval between the used As and the closing
atrial stimulation pulse Ap for this Re-Sync cycle is longer than ODI.
[0091]Refer to FIG. 15. In one embodiment, the sensed ventricular event is
declared as conducted ventricular sense event Vs if it is preceded by an
Ars and the interval between Ars and Vs is within a predefined range,
termed AV control time, preferably 150 ms-300 ms. As the example shown in
FIG. 15, this could happen if an intrinsic atrial event is detected
during the PVARP after a VES, and the Ars is followed by a conducted
ventricular sense event Vs (note in this example, the PVARP after VES is
longer than the PVARP after Vs). Accordingly, the Ars triggers a Re-Sync
Cycle, and the conducted ventricular sense event Vs implements the
Re-Sync cycle. If there is no URL violation, then the closing atrial
likely an intrinsic As because of the following conducted ventricular
sense event Vs, the device can immediately regain control of the atrial
overdrive. On the other hand, if there is no detected ventricular sense
event Vs within the AV control time, then the Re-Sync cycle is discarded.
Yet in another embodiment, the sensed ventricular event can also be
declared as VES if it is not preceded by a used atrial event (e.g., As
outside PVARP or Ap). Similar to the example shown in FIG. 7, if a VES
occurs, it simply resets the VV timer and VA timer, while the duration of
each timer is unchanged.
[0092]Refer to FIG. 16. Again, assume conducted ventricular sense event Vs
accompany atrial overdrive pacing. In this example, an Ars occurs during
the PVARP which is started by a VES, and the interval from this Ars to
the next scheduled atrial stimulation pulse Ap is shorter than AUI. To
avoid the AUI violation, the following atrial stimulation pulse Ap is
delayed so that the Ars-Ap interval is equal to AUI. Correspondingly, the
following ventricular stimulation pulse Vp is also rescheduled so that
its interval to the Ars equals to (AUI+AVD). Note that in this example,
the conducted ventricular sense event Vs following the rescheduled atrial
stimulation pulse Ap inhibits the rescheduled ventricular stimulation
pulse Vp. On the other hand, if the Ars did not cause AUI violation
(i.e., the interval from the Ars to the following Ap is longer than AUI),
then it would have no effect on the VA timer or the VV timer. As
discussed before, whenever atrial stimulation pulse Ap and ventricular
stimulation pulse Vp are postponed in order to avoid AUI violation or URL
violation, there is a possibility for the occurrence of an intrinsic As
in such cases, the detected As will trigger a Re-Sync cycle, and the
following ventricular event will implement the Re-Sync cycle.
[0093]Now refer to FIG. 17. In this example, the atrium is still
overdriven. However, the AVD is comparable to the intrinsic AV conduction
time, thus both Vs and Vp may follow the atrial stimulation pulse Ap. As
shown in the figure, the first atrial stimulation pulse Ap and the third
atrial stimulation pulse Ap are each followed by conducted ventricular
sense event Vs while the second atrial stimulation pulse Ap is followed
by a ventricular stimulation pulse Vp. As a result, the atrium is
persistently overdriven at the effective cycle length of ODI (after
Ap-Vp) or slightly shorter than ODI (after Ap-Vs), while ventricular
event (Vp or Vs) is synchronized to each atrial stimulation pulse Ap. As
described above, all the special handlings for SW Vs (trigger SW Vp and
start VV and VA timers), VES (reset VV and VA timers), used As (trigger
Re-Sync cycle limited by URL), Ars (check AUI violation and trigger
Re-Sync cycle), etc., remain the same.
[0094]Another condition that should be considered is the loss of atrial
overdrive for multiple cardiac cycles (evidenced by frequent As or Ars
without Ap). This could happen in the case of unstable atrial rhythm or
accelerating atrial rate (e.g., at the onset of the atrial
tachyarrhythmia). As described above, Ars may postpone the following
atrial stimulation pulse Ap and ventricular stimulation pulse Vp to avoid
AUI violation, thus opening window for the occurrence of used As which
will inhibit the scheduled atrial stimulation pulse Ap and trigger a
Re-Sync cycle.
[0095]The Re-Sync cycle is re-triggerable. That is, before the delivery of
the closing atrial stimulation pulse Ap of the Re-Sync cycle, if there is
another Ars or As occurs, then the Re-Sync cycle is re-triggered. Upon
the detection of the ventricular event after the Re-Sync cycle is
triggered, the AsVI is always measured from the most recent As (latest
trigger). Because the Re-Sync cycle is re-triggerable, in certain
circumstances, it is possible that the Re-Sync cycle is repeatedly
triggered while not a single one is completed by the closing atrial
stimulation pulse Ap. In other words, the atrium loses the overdrive
control. One example is illustrated in FIG. 18. In this example, the
first cycle starts with an Ap-Vp pair. Before the delivery of the
scheduled atrial stimulation pulse Ap, a used As is detected which
triggers a Re-Sync cycle. Because no ventricular sense event Vs is
detected after the As, the second ventricular stimulation pulse Vp is
delivered at the end of the VV timer (duration ODI). Meanwhile, the
device tries to implement the Re-Sync cycle based on the AsVI measured
from the As to the second ventricular stimulation pulse Vp. However,
before the delivery of the closing atrial stimulation pulse Ap for the
Re-Sync cycle, an Ars and another used As are detected. Upon the
detection of the Ars, the device checks against AUI violation and
reschedules the atrial stimulation pulse Ap and ventricular stimulation
pulse Vp if necessary. The Ars also triggers a new Re-Sync cycle. If
there were no following As, then the device would either implement or
discard the new Re-Sync cycle dependent on the presence or absence of a
conducted ventricular sense event Vs within the predefined AV control
time. However, in this example, there is another used As after the Ars.
This used As re-triggers the Re-Sync cycle, and its interval to the
following ventricular sense event Vs (AsVI) is used to implement the
Re-Sync cycle. Again, before the delivery of the closing atrial
stimulation pulse Ap for the new Re-Sync cycle, another As is detected
which triggers a new Re-Sync cycle. As a result, none of the Re-Sync
cycles is completed by the closing atrial stimulation pulse Ap, thus the
control of atrial overdrive is lost.
[0096]When the loss of atrial overdrive is suspected, for example,
consecutive number of Re-Sync cycles or frequent triggering of Re-Sync
cycles (e.g., using X-out-of-Y criteria), then adjustment of the
overdrive stimulation rate OSR and the overdrive interval ODI can be made
in order to regain control of the atrial overdrive. Alternatively, the
device may opt to exit the overdrive stimulation mode. As known in the
art, the Mode Switch (MS) can be activated when the detected high atrial
rate and the associated patterns meet the MS criteria.
[0097]In another condition, if VV timer and VA timer are repeatedly reset
by the sensed ventricular events (e.g., frequent VES, non-sustained VT,
etc.), then unstable ventricular rhythm or accelerated ventricular rate
is suspected. The frequent reset of the VA timer may also cause the loss
of atrial overdrive. In such circumstances, the device may opt to exit
the overdrive mode. Alternatively, as known in the art, the device may
detect the high ventricular rate and appropriate therapy may be applied.
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Patent InfoApplication # US 20080114409 A1Publish Date 05/15/2008 Document # 11560099 File Date 11/15/2006 USPTO Class 607 17 Other USPTO Classes International Class 61N1/368 Drawings 11 AtriumHemodynamicPacemakerRight AtriumSynchronous Mode