Date post: | 24-Jan-2017 |
Category: |
Health & Medicine |
Upload: | sunil-reddy-d |
View: | 172 times |
Download: | 5 times |
Pacemaker Timing & Advanced Dual Chamber Concepts
Dr D Sunil ReddyConsultant Cardiologist
KIMS Hospital
Topics
• Single Chamber Timing• The NBG Code• Dual Chamber Timing• Dual Chamber Pacing Modes• Upper Rate Behaviour• Timings in Rate-responsive Pacemakers
Single Chamber Timing Terminology
• Lower rate & Lower Rate Interval• Refractory period• Blanking period• Upper Sensor Rate & Upper Sensor Rate
Interval
VP VP VS VP
Lower Rate Interval• Interval corresponding to the programmed Lower Rate• Defines the lowest rate the pacemaker will pace• Starts after every paced or sensed event• Ends at the next paced or sensed event• Vp-Vp or Vs-Vp in a VVI pacemaker• Ap-Ap or As-Ap in an AAI pacemaker
LRILRI
Lower Rate = 60, LRI = 1000 ms
Voltage Deflections of the Voltage Deflections of the Sensed EGM in a PacemakerSensed EGM in a Pacemaker
Pacemaker
Stimulus
Paced R wave
Post-pace T wave
Intrinsic R wave
T wave corresponding to intrinsic R wave
2.5 mV
Refractory PeriodRefractory Period
Refractory Period Refractory Period Refractory Period
NO SENSING NO SENSING NO SENSING
Refractory Period
Lower Rate Interval
VP VP VVI / 60
• Interval initiated by a paced or sensed event• Designed to prevent inhibition by cardiac or non-cardiac events e.g.
stimulus evoked R wave, repeated sensing of the same intrinsic R wave, T waves, noise
• Events sensed in the refractory period do not affect the Lower Rate Interval but start their own Refractory Periods
Refractory Period
Lower Rate Interval
• Interval initiated by a paced or sensed event• Designed to prevent inhibition by cardiac or non-cardiac events e.g.
stimulus evoked R wave, repeated sensing of the same intrinsic R wave, T waves, noise
• Events sensed in the refractory period do not affect the Lower Rate Interval but start their own Refractory Periods
VP VP VR VP
LRI LRI
Afterpotential due to Polarization
Afterpotential
Blanking Period
Lower Rate Interval
VP VP VVI / 60
• The first portion of every refractory period• Pacemaker is “blind” to any activity and no events can be sensed• Designed to prevent oversensing of pacing stimulus & after-
potential
Blanking PeriodRefractory Period
Sensor-Indicated Rate
• The basic pacing rate in all rate responsive modes
• Determined by the pacemaker based on the sensor-detected level of patient activity
• Lower Rate <= Sensor Indicated Rate<= Upper Activity Rate
Activity Sensor
• Fixed to the back of the can• Responds to
– Pressure– Vibrations
Accelerometer Based Activity Sensor
• Located on the IC of the pacemaker
• Does not respond to pressure or vibrations
• Responds to motion – Primarily in the anterior-posterior axis
Body Movement
Upper Sensor Rate Interval
Lower Rate Interval
VP VP VVIR / 60 / 120
• Defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR, VVIR modes)
• A paced event can never occur before the UARI expires
Blanking PeriodRefractory Period
Upper Sensor Rate Interval
Sensor Indicated Rate
VOO Mode
Blanking Period
VP VP
Lower Rate Interval
VOO / 60
• Asynchronous pacing delivers output regardless of intrinsic activity
VPVPVP VP
VOO TIMINGVOO TIMING
VPVPVP VP
VOO TIMINGVOO TIMING
V
VPVPVP VPVP
VOO TIMINGVOO TIMING
V
VP VPVPVP VP
VOO TIMINGVOO TIMING
V
VP VPVPVP VP
VOO TIMINGVOO TIMING
V
VP VPVPVPVP
VOO TIMINGVOO TIMING
V
VP VP VPVPVP
VOO TIMINGVOO TIMING
V
VP VP VPVPVP
VOO TIMINGVOO TIMING
V
V
VP VPVP
VOO TIMINGVOO TIMING
VP VP
VVI Mode
Lower Rate Interval
VP VSBlanking/Refractory
VP
{
VVI / 60
• Pacing inhibited with intrinsic activity
VPVS
VPVPVP
VVI TIMINGVVI TIMING
V
VPVS
VPVP
VVI TIMINGVVI TIMING
VP
V
VP VPVS
VPVP
V
VVI TIMINGVVI TIMING
VP VPVS
VPVP
V
VVI TIMINGVVI TIMING
VP VPVS
VPVP
VVI TIMINGVVI TIMING
V
VP VP VPVS
VP
VVI TIMINGVVI TIMING
V
VP VP VPVS
VVI TIMINGVVI TIMING
VP
V
VP VPVP VP
VVI TIMINGVVI TIMING
V
VP VPVP VP
VVI TIMINGVVI TIMING
V
VS
VP VPVP VP
VVI TIMINGVVI TIMING
V
VS
V
VP VPVP VPVS
VVI TIMINGVVI TIMING
VVI – Refractory Sensing
VPVP VPVP
VVI TIMINGVVI TIMING
VPVP VPVP
V
VVI TIMINGVVI TIMING
VPVP VP
V
VP
VVI TIMINGVVI TIMING
VP VPVS
VPVP
V
VVI TIMINGVVI TIMING
VP VPVS
VP
V
VVI TIMINGVVI TIMING
VP VPVS
VPVP
V
VVI TIMINGVVI TIMING
VP VPVS
VP VP
V
VVI TIMINGVVI TIMING
VP VPVS
VP VP
V
VR
VVI TIMINGVVI TIMING
VP VPVS
VP VP
VR
V
VVI TIMINGVVI TIMING
V
VVI TIMINGVVI TIMING
VP VPVS
VP VP
VR
VVI Timing – T wave Oversensing
VPVS
VPVPVP
VVI TIMINGVVI TIMING
VPVS
VPVPVP
VVI TIMINGVVI TIMING
V
VPVS
VPVP
VVI TIMINGVVI TIMING
V
VP
VP VPVS
VPVP
VVI TIMINGVVI TIMING
V
VP VPVS
VPVPVS
VVI TIMINGVVI TIMING
V
VPVS VP
VSVPVP
VVI TIMINGVVI TIMING
V
VPVS VP
VSVPVP
VVI TIMINGVVI TIMING
V
VPVS VP
VSVP
VVI TIMINGVVI TIMING
V
VP
VP VPVS VP
VSVP
VVI TIMINGVVI TIMING
V
VP VPVS VP
VSVP
VVI TIMINGVVI TIMING
VS
V
VP VPVS VS VP
VSVP
VVI TIMINGVVI TIMING
V
VP VPVS VS VP
VS
VVI TIMINGVVI TIMING
V
VP
VP VPVS
VPVS VP
VS
VVI TIMINGVVI TIMING
V
V
VVI TIMINGVVI TIMING
VP VPVS
VPVS VP
VS
T wave re-cycling
VP
VR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
VP
VR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VP
VR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VP
VP VP
VR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VP VP
VR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VR
VP VP
VRVR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VP VP
VRVR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VR
VP VP
VRVR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VR
VP VP
VRVR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VP
VR
VP VP VP
VRVR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VR
VP VP VP
VRVR VR VRVR VR
VPVP
VVI TIMINGVVI TIMING
V
VR
VP VP VP
VRVR VR VRVR VR
VP
VVI TIMINGVVI TIMING
V
VR
VP VP VP
VRVR VR VRVR VR
VP
VVI TIMINGVVI TIMING
VP
V
VR
V
VP VPVP
VVI TIMINGVVI TIMING
VP VP
VRVR VR VRVR VR
Interference Operation
VR
Noise Reversion
VPVPSRSR SR SR
Noise Sensed
Lower Rate Interval
VVI/60
• Continuous refractory sensing will cause pacing at the lower or sensor driven rate
VVIR
VP VP
Refractory/Blanking
Lower Rate
Upper Rate Interval(Maximum Sensor Rate)
VVIR / 60/120Rate Responsive Pacing at the Upper Sensor Rate
• Pacing at the sensor-indicated rate (= Upper Rate Interval)
AAIR
Lower Rate Interval
AP APRefractory/Blanking
Upper Rate Interval(maximum sensor rate)
AAIR / 60 / 120(No Activity)
• Atrial-based pacing allows the normal A-V activation sequence to occur
Sensor Indicated Interval
VP VP VS VP
Lower Rate Interval-60 ppm
Hysteresis
• Allows the rate to fall below the programmed lower rate following an intrinsic beat
Hysteresis Rate-50 ppm
Dual Chamber Timing (DDD or Universal Mode)
NBG Code ReviewI
ChamberPaced
IIChamber
Sensed
IIIResponseto Sensing
IVProgrammableFunctions/Rate
Modulation
VAntitachy
Function(s)
V: Ventricle V: Ventricle T: Triggered P: Simpleprogrammable
P: Pace
A: Atrium A: Atrium I: Inhibited M: Multi-programmable
S: Shock
D: Dual (A+V) D: Dual (A+V) D: Dual (T+I) C: Communicating D: Dual (P+S)
O: None O: None O: None R: Rate modulating O: None
S: Single (A or V)
S: Single (A or V)
O: None
NBG Code Revised - 2002I
ChamberPaced
IIChamber
Sensed
IIIResponseto Sensing
IVProgrammableFunctions/Rate
Modulation
VMulti Site
Pacing
V: Ventricle V: Ventricle T: Triggered V: Ventricle
A: Atrium A: Atrium I: Inhibited
D: Dual (A+V) D: Dual (A+V) D: Dual (T+I) D: Dual (A+V)
O: None O: None O: None R: Rate modulating O: None
S: Single (A or V)
S: Single (A or V)
O: None
A: Atrium
Rate = 60 bpm / 1000 msA-A = 1000 ms
APVP
APVP
V-AAV V-AAV
• Atrial Pace, Ventricular Pace (AP/VP)
Four “Faces” of DDD Pacing
Rate = 60 ppm / 1000 msA-A = 1000 ms
AP VS
AP VS
V-AAV V-AAV
• Atrial Pace, Ventricular Sense (AP/VS)
Four “Faces” of DDD Pacing
ASVP
ASVP
Rate (sinus driven) = 70 bpm / 857 msA-A = 857 ms
• Atrial Sense, Ventricular Pace (AS/ VP)
V-AAV AV V-A
Four “Faces” of DDD Pacing
Rate (sinus driven) = 70 bpm / 857 msSpontaneous conduction at 150 msA-A = 857 ms
ASVS
ASVS
V-AAV AV V-A
• Atrial Sense, Ventricular Sense (AS/VS)
Four “Faces” of DDD Pacing
DDD Timing Parameters
• Lower rate & Lower Rate Interval• AV and VA intervals• Upper Tracking Rate & Interval• Refractory periods• Blanking periods
Lower Rate Interval
APVP
APVP
Lower Rate • The lowest rate the pacemaker will pace the ATRIUM in
the absence of intrinsic atrial events• Ap-Ap or As-Ap• Starts with every atrial event and ends with the next
atrial event
DDD 60 / 120
APVP
ASVP
AVI AVI
Lower Rate Interval
AV Intervals• Electric analog of the PR Interval – allows for AV Synchrony or
atrial kick
• Initiated by a paced or non-refractory sensed atrial event
• The Atrial Channel is refractory during the AV interval
DDD 60 / 120
PAV
Typical Programming for CHBSAV = 120 ms, PAV = 150 ms
Lower Rate Interval
APVP
APVP
AV Interval VA Interval
Atrial Escape Interval (V-A Interval)• The interval between a paced or sensed ventricular event to the
next atrial event• Starts with a Vs or Vp• Ends with Ap or (prematurely) with As
DDD 60 / 120PAV 200 ms; V-A 800 ms
200 ms 800 ms
1000 ms
Atrial Escape Interval (VA Interval)
• Not programmable
• A (non-refractory) ventricular event not preceded by an atrial event (e.g. PVC, lack of atrial sensing, no sinus activity) starts a new VA interval
Lower rate interval – AV interval = VA interval
Lower Rate Interval
APVP
APVP
VA Interval
Atrial Escape Interval (V-A Interval)
DDD 60 / 120PAV 200 ms; V-A 800 ms
200 ms 800 ms
1000 ms
PV C
ASVP
AS
VPDDDR 60 / 100 (upper tracking rate)
Sinus rate: 100 bpm
Lower Rate Interval {
Upper Tracking Rate Limit
Upper Tracking Rate
SAV
SAV
VA VA
• Prevents rapid ventricular pacing rates in response to rapid atrial rates
• The maximum rate the ventricle can be paced in response to sensed (intrinsic)atrial events
• Starts with every ventricular sensed or paced event• No Vp can occur before the UTRI expires
SAV
600 ms
Programing Upper Tracking Rate
• Typically programmed to 120 bpm
• Young, active patients – 150 to 180 bpm
• Patients with angina – 100 to 110 bpm
Refractory Periods
• Ventricular Refractory Period (VRP)• Post-ventricular Atrial Refractory Period
(PVARP)• Total Atrial Refractory Period (TARP)
Separate Amplifiers• Atrial Channel• Ventricular Channel
Ventricular Refractory Period• Same as for VVI mode• Starts with every ventricular event, including refractory
sensed events• Events in the VRP do not affect the VA interval
AP
VPVentricular Refractory Period (VRP)
Retrograde P waves
• If the AV node is not refractory during a ventricular event, the ventricular excitation can be conducted back into the atrium – Retrograde P wave
• Possible in both CHB & SSS patients
• Retrograde P waves may be sensed by the pacemaker and result in initiation of an AV interval followed by a Vp
• The Vp can in turn result in another retrograde sensed P wave causing another Vp
• Pacemaker Mediated Endless Loop Tachycardia
Post Ventricular Atrial Refractory Period (PVARP)
Post-Ventricular Atrial Refractory Period
• PVARP starts with every sensed or paced ventricular event, including refractory sensed events
• It renders the ATRIAL CHANNEL refractory and has no effect on ventricular sensing
• The PVARP is intended primarily to prevent sensing of retrograde P waves by the atrial channel
• Atrial events sensed in the PVARP do not start an SAV and are marked Ar
AP
VPVentricular Refractory Period (VRP)
Retrograde P wave
Lower Rate Interval
AR
PVARP
Upper Tracking Rate
Lower Rate Interval
{No SAV started for events sensed in the TARP
AS AS
VPVP
SAV = 200 msPVARP = 300 ms
Thus TARP = 500 ms (120 ppm)
DDDLR = 60 ppm (1000 ms)
UTR = 100 bpm (600 ms)Sinus rate = 66 bpm (900 ms)
SAVTARP
PVARP
Total Atrial Refractory Period (TARP)
• Sum of the AV Interval and PVARP
SAV
What is happening
DDD / 70 / 120
Issue: Crosstalk
• Crosstalk is the sensing of a pacing stimulus delivered in the opposite chamber, which results in undesirable pacemaker response, e.g., false inhibition
DDD / 70 / 120
Blanking Periods• First portion of the refractory period-sensing when sensing is
completely disabled• To prevent sensing of the pacemaker stimulus, after potential,
repeated sensing of the same intrinsic wave and cross-talk
AP
VPAP
Post Ventricular Atrial Blanking (PVAB) (Programmable)
Post Atrial Ventricular Blanking (Programmable)
Ventricular Blanking (Nonprogrammable)
Atrial Blanking (Nonprogrammable)
Dual Chamber Modes & their Timing
DDD Mode- Universal Mode
• Atrial Tracking – provides AV Synchrony and preserves Heart Rate reserves
• Atrial intrinsic events start an SAV• Sensed Intrinsic events in a given chamber
inhibit pacing in that chamber
DDD Mode
• ApVp – AV Sequential Pacing• Sinus Rate below programmed Lower Rate• AV conduction absent or PAV interval
programmed shorter than intrinsic AV conduction time
VP VP
AP AP
V
A
VRP
DDD TIMINGDDD TIMING
VP VP
AP AP
V
A
VRP
VP
DDD TIMINGDDD TIMING
VP VP VP
AP AP
V
A
V-A Interval
V-A Interval
DDD TIMINGDDD TIMING
VRPVRP
VP
A
V
PVARPPVARP
AP
VP
DDD TIMINGDDD TIMING
V-A Interval
V-A Interval
VRPVRP
VP
A
V
PVARPPVARP
AP
VP
DDD TIMINGDDD TIMING
VRPVRP
PVARPPVARP
VP
A
V
PVARPPVARP
VP VP
AP
DDD TIMINGDDD TIMING
VRPVRP
PVARPPVARP
VP
AP
A
V
PVARPPVARP
VP
DDD TIMINGDDD TIMING
VRPVRP
PVARPPVARP AV RP
A-V Interval
A-V Interval
VP
AP
A
V
PVARPPVARP
VP
DDD TIMINGDDD TIMING
VP
VRPVRP
PVARPPVARP AV RP
VP VP
AP
A
V
DDD TIMINGDDD TIMING
PVARPPVARP
VRPVRP
VP
AV RPAV RPPVARPPVARP
VRPVRP
VP VP
AP
A
V
DDD TIMINGDDD TIMING
PVARPPVARP
VRPVRP
VP
AV RPAV RPPVARPPVARP PVARPPVARP
VRPVRP
VP VP
AP
A
V
DDD TIMINGDDD TIMING
PVARPPVARPAV RPAV RP PVARPPVARP
VRPVRP
VP
AP
VP VP
AP AP
A
V
DDD TIMINGDDD TIMING
PVARPPVARPAV RPAV RP PVARPPVARP
VRPVRP
AV RP
VP
VP VP
AP AP
A
V
DDD TIMINGDDD TIMING
AV RPAV RP PVARPPVARP
VRPVRP
VP
VP VP
AP AP
A
V
DDD TIMINGDDD TIMING
VP
DDD Mode
• AsVs – Pacemaker Inhibited• Sinus Rate greater than programmed Lower
Rate• Normal intrinsic AV conduction
AS AS AS
VS VS VS
AS
VS
AS
DDD TIMINGDDD TIMING
AS AS AS
VS VS VS
AS
VS
AS
A
V
DDD TIMINGDDD TIMING
AS AS AS
VS VS VSVS
ASAS
A
V
DDD TIMINGDDD TIMING
AS AS ASAS
VS VS VSVS
AS
A
V
DDD TIMINGDDD TIMING
AS AS ASAS
VS VS VSVS
AS
A
V
DDD TIMINGDDD TIMING
VS
AS AS ASAS
VS VS VS VSVS
AS
A
V
DDD TIMINGDDD TIMING
AS AS ASAS
VS VS VS VSVS
AS
A
V
DDD TIMINGDDD TIMING
ASAS AS ASAS
DDD TIMINGDDD TIMING
VS VS VS VS VS
A
V
Pacemaker Inhibited
DDD Mode
• ApVs – Atrial Pacing Ventricular Inhibition• Sinus Rate lower than programmed Lower
Rate• Intrinsic AV Conduction
VS VS
AP AP
VSVS
AP
DDD TIMINGDDD TIMING
VS VS
AP AP
VSVS
AP
A
V
DDD TIMINGDDD TIMING
VS VS
AP AP
VSVS
AP
A
V
DDD TIMINGDDD TIMING
AP
VS VS
AP AP
VSVS
AP
A
V
DDD TIMINGDDD TIMING
AP
VS VS
AP AP AP
VS
AP
A
V
DDD TIMINGDDD TIMING
VS VS
AP AP AP
VS
AP
A
V
DDD TIMINGDDD TIMING
VS
VS VS VS
AP AP AP
VS
AP
A
V
DDD TIMINGDDD TIMING
VS VS VS VS
AP AP AP AP
A
V
DDD TIMINGDDD TIMINGAtrial Pacing - Ventricular inhibition
DDD Mode
• AsVp – Atrial Tracking• Sinus Rate greater than programmed Lower
Rate• No intrinsic conduction or programmed SAV
is shorter than intrinsic AV conduction time
AS
VP VP VP
AS AS
VP
ASAS
DDD TIMINGDDD TIMING
AS
VP VP VP
AS AS
VP
ASAS
A
V
DDD TIMINGDDD TIMING
AS
VP VP VP
AS AS
VP
AS
A
V
AS
DDD TIMINGDDD TIMING
AS
VP VP VP
AS ASAS
VP
AS
A
V
DDD TIMINGDDD TIMING
AS
VP VP VP
AS ASAS
VP
AS
A
V
DDD TIMINGDDD TIMING
AS
VP VP VP
AS ASAS
VP
AS
VP
A
V
DDD TIMINGDDD TIMING
VP
AS
VP VP VP
AS ASAS
VP
AS
A
V
DDD TIMINGDDD TIMING
A
V
VP
AS
VP VP VP VP
AS AS ASAS
DDD TIMINGDDD TIMINGAtrial Tracking
DDI Mode
• A-V sequential pacing WITHOUT atrial tracking
• Atrial sensed events do not begin an SAV• Atrial Sensed events inhibit atrial pacing• Ventricular pacing rate cannot increase
beyond the programmed lower rate
DDI mode is used during Mode Switch due to atrial tachycardias
A
V
VS
PVARPPVARP
VRPVRP
ARP PVARPPVARP ARP PVARPPVARPARP
AS
VP
PVARPPVARP
AS
VP
ARPARPPVARPPVARP
AP
AV RPAV RP
DDI TIMINGDDI TIMING
A
V
VS
PVARPPVARP
VRPVRP
ARP PVARPPVARP ARP PVARPPVARPARP
AS
VP
PVARPPVARP
AS
VP
ARPARPPVARPPVARPAV RPAV RP
AP
DDI TIMINGDDI TIMING
AP
A
V
VS
PVARPPVARP
VRPVRP
ARP PVARPPVARP ARP PVARPPVARPARP
AS
VP
PVARPPVARP
AS
VP
ARPARPPVARPPVARP
DDI TIMINGDDI TIMING
AV RPAV RP
AP
A
V
VS
PVARPPVARP
VRPVRP
ARP PVARPPVARP ARP PVARPPVARPARP
AS
VP
PVARPPVARP
AS
ARPARPPVARPPVARP
VP
DDI TIMINGDDI TIMING
A-VInterval
AV RPAV RP
A-VInterval
AP
A
V
VP VS
VRPVRP
ARP PVARPPVARP ARP PVARPPVARPARP
AS
VP
PVARPPVARP
AS
ARPARP
DDI TIMINGDDI TIMING
AV RPAV RP PVARPPVARP
AP
A
V
VP VS
VRPVRP
ARP PVARPPVARP ARP PVARPPVARPARP
AS
VP
PVARPPVARPARPARP
AS
DDI TIMINGDDI TIMING
AV RPAV RP PVARPPVARP
A-VInterval
V-A Interval
V-A Interval
AP
A
V
VP VS
VRPVRP
ARP PVARPPVARP ARP PVARPPVARPARP
AS
VP
PVARPPVARPARPARP
AS
DDI TIMINGDDI TIMING
AV RPAV RP PVARPPVARP
A-VInterval
V-A Interval
V-A Interval
AP
A
V
AS
VP VS
PVARPPVARP ARP PVARPPVARPARP
AS
VP
PVARPPVARP
DDI TIMINGDDI TIMING
ARPARPAV RPAV RP
A-VInterval
AP
A
V
AS
VP VS
PVARPPVARP ARP PVARPPVARPARP
AS
PVARPPVARP
DDI TIMINGDDI TIMING
VP
ARPARPAV RPAV RP
A-VInterval
DDI TIMINGDDI TIMING
AP
A
V
AS AS
VP VP
ARPARP
A-VInterval
AV RPAV RP ARP
V-A Interval
V-A Interval
PVARPPVARP
VRPVRP
DDI TIMINGDDI TIMING
AP
A
V
AS AS
VP VP
ARPARP
A-VInterval
AV RPAV RP
V-A Interval
V-A Interval
PVARPPVARP ARP
DDI TIMINGDDI TIMING
AP
A
V
AS AS
VP VP
ARPARPARP
A-VInterval
AV RPAV RP
V-A Interval
V-A Interval
PVARPPVARP
DDI TIMINGDDI TIMING
AP
A
V
AS AS
VP VP VS
ARPARPARP
A-VInterval
AV RPAV RP
DDI TIMINGDDI TIMING
AP
A
V
AS AS
VP VP VS
VRPVRP
ARPARPARP
A-VInterval
PVARPPVARPAV RPAV RP
DDI TIMINGDDI TIMING
AP
A
V
AS AS
VP VP VS
ARPARPARPARPAV RPAV RP
A-VInterval
PVARPPVARPPVARPPVARP
V-A Interval
PVARPPVARP
V-A Interval
VRPVRP
DDI TIMINGDDI TIMING
AP
A
V
AS AS
VP VP VS
DDI/R
Lower Rate Interval
DDI 60PAV = 200 msPVARP = 300 ms
VPVP VP
AS AS APAS
PVARP PVARP
• A non-tracking mode– Provides AV sequential pacing at lower or sensor indicated rate
VA Interval VA Interval
LR LR
VA Interval
VDD Mode• Atrial Synchronous pacing or Atrial Tracking Mode
• A sensed intrinsic atrial event starts an SAV
• The Lower Rate Interval is measured between Vs to Vp or Vp to Vp
• If no atrial event occurs at the end of the Lower Rate Interval a Ventricular pace occurs
• Paces in the VVI mode in the absence of atrial sensing or if programmed lower rate > atrial intrinsic rate
VDD Mode
MVP Basic OperationAAI(R) Mode Atrial based pacing allowing intrinsic AV conduction
PR Intervals are only restricted by the underlying atrial rate or sensor rate; VS events simply need to occur prior to the next AS or AP.
MVP Basic OperationVentricular Backup Ventricular pacing only as needed in the presence of
transient loss of conduction
MVP Basic OperationDDD(R) Switch Ventricular support if lossof A-V conduction is persistent
Ventricular Safety Pacing
Issue: Crosstalk
• Crosstalk is the sensing of a pacing stimulus delivered in the opposite chamber, which results in undesirable pacemaker response, e.g., false inhibition
DDD / 70 / 120
Solution: Ventricular Safety Pacing• Following an atrial paced event, a ventricular safety pace
interval is initiated– If a ventricular sense occurs during the safety pace window, a pacing
pulse is delivered at an abbreviated interval (110 ms)
Post Atrial Ventricular Blanking
PAV Interval
Ventricular Safety Pace Window
PVARP
Ventricular Safety Pace
AV PVARP PVARP AV110 ms
VS VPVP VP
AP APAP
VS VS VS
APAPAP
DDD TIMINGDDD TIMING
VS VS VS
APAPAP
A
V
DDD TIMINGDDD TIMING
VS VS VS
APAPAPAP
A
V
DDD TIMINGDDD TIMING
VS VS VS
AP APAPAP
A
V
DDD TIMINGDDD TIMING
VS VS VS
AP APAP
A
V
DDD TIMINGDDD TIMING
AP
VS VS VS
AP AP APAP
A
V
DDD TIMINGDDD TIMING
VS VS VS
AP AP APAP
A
V
VSP
DDD TIMINGDDD TIMING
VS VS VS
AP AP AP
VSP
AP
DDD TIMINGDDD TIMING
A
V
DDD TIMINGDDD TIMING
VS VS VS
AP AP AP
VSP
A
V
AP
A
V
DDD TIMINGDDD TIMING
VS VS VS
AP AP AP AP
VSP
Ventricular Safety Pacing
Ventricular Safety Pace
DDD 60 / 120
Ventricular Safety Pacing
• Often seen during atrial undersensing in patients with intact AV conduction
• Atrial undersensing results in Ap despite intrinsic event and starts an AV interval with a VSP window
• If the intrinsic event is conducted through the AV Node and and the Ventricular intrinsic event occurs during the VSP window, a ventricular pace is delivered at the end of the VSP window
Other Methods for Managing Crosstalk
• Reduce atrial output (amplitude and/or pulse width)• Decrease (increase value) ventricular sensitivity• Program bipolar (if possible)• Increase the post -atrial ventricular blanking period
Upper Rate Behaviour
Upper Rate Behaviour
• Pacemaker operation and timings when the atrial intrinsic rate is at or above the Upper Tracking Rate
• Governed by two rates`– UTR– TARP rate
The Upper Tracking Rate
• Prevents the ventricles from being paced at high rates in response to atrial tachycardias
• The ventricle can never be paced faster than the Upper Tracking Rate in response to sensed atrial activity
• The Upper Rate Interval is given priority over other timing intervals
PVARP
Upper Tracking Rate
Lower Rate Interval
{P Waves Blocked
AS AS
VPVPSAV = 200 ms
PVARP = 300 msThus TARP = 500 ms (120 ppm)
DDDLR = 60 ppm (1000 ms)
UTR = 100 bpm (600 ms)Sinus rate = 66 bpm (900 ms)
SAVTARP
PVARP
Total Atrial Refractory Period (TARP)
• Sum of the AV Interval and PVARP
SAV
TARP
• The atrial channel is refractory to sensed events that occur during the TARP
• Any atrial intrinsic event occurring in the TARP does not start an AV interval
• Any atrial intrinsic event occurring in the TARP is not tracked by the pacemaker and does not result in ventricular pacing
TARP Rate
• TARP = SAV + PVARP (during atrial sensed rhythms)• If SAV = 150 ms and PVARP = 350 ms,
TARP = 500 msTARP Rate = 120 bpm
• Atrial rates with cycle length’s less than 500 ms (or rates greater than 120 bpm) will result in at least every other intrinsic atrial wave falling in the TARP
• Only intrinsic events falling outside the TARP will generate an SAV and a resultant ventricular pace
Fixed Block or 2:1 Block
• Occurs whenever the intrinsic atrial rate exceeds the TARP rate
• At least every other atrial event falls in the TARP when the atrial rate exceeds the TARP rate
• Results in block of atrial intrinsic events in fixed ratios
• Every other P wave falls into refractory and does not restart the timing interval
Upper Tracking Limit
Lower Rate Interval {
{P Wave Blocked
AS AS
VPVPARAR
Sinus rate = 133 bpm (450 ms)PVARP = 300 ms SAV = 200 msTracked rate = 66 bpm (900 ms)
AV PVARP AV PVARPTARP TARP
2:1 Block
DDD TIMINGDDD TIMING
AS AS
VP VP
AS ASARARAR
VPVP
ARAS
VP
A
V
DDD TIMINGDDD TIMING
AS AS
VP VP
AS ASARARAR
VPVP
AR
VP
A
V
DDD TIMINGDDD TIMING
AS
AS AS AS
VP VP
AS ASARARAR
VPVP
AR
A
V
DDD TIMINGDDD TIMING
VP
AS
VP
AS
VP VP
AS ASARARAR
VPVP
ARAS
A
V
DDD TIMINGDDD TIMING
AS
VP
AS
VP VP
AS ASARARAR
VPVP
AR
A
V
DDD TIMINGDDD TIMING
AS
VP
AS
VP VP
AS ASARARAR
VPVP
ARAS
A
V
DDD TIMINGDDD TIMING
AS
VP
AS AS
VP VP
AS ASARARAR
VP
AR
VP
A
V
DDD TIMINGDDD TIMING
AS
VP VP
AS AS
VP VP
AS ASARARAR
VP
AR
A
V
DDD TIMINGDDD TIMING
AS
VP VP
AS AS
VP VP
AS ASARARAR
VP
A
V
AR
DDD TIMINGDDD TIMING
AS
VP VP
AS AS
VP VP
AS ASAR ARARAR
VP
A
V
DDD TIMINGDDD TIMING
AS
VP VP
AS AS
VP VP
AS ASAR ARARAR
VP
A
V
DDD TIMINGDDD TIMING
AS
VP VP
AS
VP VP
AS ASAR ARARAR
VP
A
V
DDD TIMINGDDD TIMING
AS
AS
VP VP
AS AS
VP VP
AS ASAR ARARAR
VP
A
V
DDD TIMINGDDD TIMING
AS
VP VP
AS AS
VP VP VP
AS ASAR ARARAR
A
V
DDD TIMINGDDD TIMING
DDD TIMINGDDD TIMING
AS
VP VP
AS AS
VP VP VP
AS ASAR ARARAR
A
V
DDD TIMINGDDD TIMING
AS
VP VP
AS AS
VP VP VP
AS ASAR ARARAR
A
V
2:1 Block
Wenckebach Operation
• Occurs when the intrinsic atrial rate lies between the UTR and the TARP rate
• Results in gradual prolonging of the AV interval until one atrial intrinsic event occurs during the TARP and is not tracked
• Cycle repeats
PVARP
Wenckebach Operation
Upper Tracking Rate
Lower Rate Interval {
AS AS AR APVPVP VP
TARPSAV PAV PVARP SAV PVARP
P Wave Blocked (unsensed or unused)
DDD Sinus rate = 109 bpm (550 ms) LR = 60 bpm (1000 ms) UTR = 100 ppm (600 ms)
SAV = 200 ms PAV = 230 ms PVARP = 300 ms
• Prolongs the SAV until upper rate limit expires– Produces gradual change in tracking rate ratio
TARP TARP
DDD TIMINGDDD TIMING
A
V
DDD TIMINGDDD TIMING
ASAS ASAR
VPVP
AS
VP VPVP
AS
DDD TIMINGDDD TIMING
A
V
AS
ASAS AS ASAR
VPVP
AS
VP VP
AS
DDD TIMINGDDD TIMING
VP
A
V
VP
ASAS AS ASAR
VPVP
AS
VP VP
AS
DDD TIMINGDDD TIMING
A
V
VP
ASAS AS ASAR
VPVPVP VP
ASAS
A
V
DDD TIMINGDDD TIMING
VP
AS ASAS AS ASAR
VPVPVP VP
AS
A
V
DDD TIMINGDDD TIMING
VP
AS ASAS AS ASAR
VPVP
AS
VP
A
V
DDD TIMINGDDD TIMING
VP
VP VP
AS ASAS AS ASAR
VPVP VP
A
V
AS
DDD TIMINGDDD TIMING
VP
AS
VP
AS ASAS AS ASAR
VP VPVP
DDD TIMINGDDD TIMING
A
V
VP
AS
VP
AS ASAS AS ASAR
VPVP
A
V
DDD TIMINGDDD TIMING
VP
VP
AS
VP VP
AS ASAS AS ASAR
VPVP
A
V
DDD TIMINGDDD TIMING
VP
AS
VP VP
AS ASAS AS ASAR
VPVP
DDD TIMINGDDD TIMING
A
V
VP
AS
VP VP
AS ASAS
DDD TIMINGDDD TIMING
AS ASAR
VP
A
V
VP
VP
AS
VP VP VP
AS ASAS
DDD TIMINGDDD TIMING
AS ASAR
A
V
VP
A
V
VP
AS
VP VP VP
AS ASAS
DDD TIMINGDDD TIMING
AS ASAR
VP
Wenckebach Behaviour
Wenckebach or 2:1 block rate during exercise/activity?
• 2:1 block – – Atrial Rates > TARP rate
• Wenckebach – Upper Tracking Rate < Atrial Rate < Tarp Rate
• Wenckebach is preferred – Fewer symptoms– Warning to patient
Wenckebach vs. 2:1 Block – What Will Happen First?
What will the upper rate behavior of this pacemaker be?
Lower rate = 60 ppmUpper tracking rate = 120 ppm
PAV = 230 msSAV = 250 ms
PVARP = 350 ms
Wenckebach vs. 2:1 Block – Solution
Upper tracking rate = 120 ppmPVARP = 350 ms
SAV = 250 ms
• 2:1 block interval = TARP = SAV + PVARP(250 ms + 350 ms = 600 ms)
• TARP Rate = 100 bpm• TARP rate is less than the upper tracking rate
interval Thus, 2:1 block will occur as soon as atrial rate
exceeds 100 bpm
Wenckebach vs. 2:1 Block – What Will Happen First?
What will the upper rate behavior of this pacemaker be?
Lower rate = 60 ppmUpper tracking rate = 100 ppm
PAV = 150 msSAV = 150 ms
PVARP = 350 ms
Wenckebach vs. 2:1 Block – Solution
Upper tracking rate = 100 ppmPVARP = 250 ms
SAV = 150 ms
• 2:1 block interval = TARP = SAV + PVARP(150 ms + 350 ms = 500 ms)
• TARP rate is 120 bpm Thus, Wenckebach will begin as soon as atrial rate
exceeds 100 bpmWenckebach behaviour will persist until atrial rate
exceeds 120 (TARP rate), after which 2:1 block will commence
What Can We Do to Make Wenckebach Occur First?
• Shorten or reduce the TARP by:– Shortening the PVARP– Shortening the SAV– Automatic PVARP
DDDR 60 / 120A-A = 500 ms
APVP
APVP
Upper Activity Rate Limit
Lower Rate Limit
V-APAV V-APAV
Upper Sensor Rate• In rate responsive modes, the Upper Sensor Rate provides the
limit for sensor-indicated pacing• It can be programmed independently of the UTR• Typically programmed to 120 bpm• For younger, active patients with chronotropic incompetence –
150 bpm
UAR versus UTR
UTR
The ventricle can never be paced at a rate higher than the UTR during sensed atrial activity
e.g. 120 bpm
All atrial rates above 120 bpm will not be tracked 1:1 by the ventricles
UAR
Maximum Sensor Indicated Rate
The atrium can never be paced at a rate higher than the UARe.g. 140 bpm
Both atrium and subsequently the ventricle may be paced up to 140 bpm
Pacemaker Mediated Tachycardias
Pacemaker Mediated Tachycardias
• Any tachycardia that occurs due to the presence of a dual chamber pacemaker
– Rapid ventricular pacing during tracking of rapid atrial rates
– Sensing of EMI or EMG on the atrial channel resulting in rapid ventricular pacing
– Tachycardia resulting from stimulation by pacemaker during myocardial vulnerable periods
– Sensing of Retrograde P waves – Endless Loop Tachycardia
Pacemaker Mediated Tachycardia (PMT)
• PMT is a paced rhythm, usually rapid, which is sustained by ventricular events conducted retrogradely (i.e., backwards) to the atria
PMT
PMT
• Loss of AV synchrony may be caused by:– PVC– Very early PAC– Atrial non-capture– Atrial undersensing– Atrial oversensing
• Long AV intervals can cause the AV node to recover from refractoriness and result in retrograde conduction
PMT Prevention
• Prevent Retrograde conduction– Maintain normal AV intervals at all rates– Good atrial sensing at implant– Good atrial thresholds at implant
• Prevent sensing of retrograde P wave if it occurs
Rate of PMT
• The rate of the PMT can never exceed the UTR
• Depends on the programmed parameters and the Vp to retrograde P wave interval
• Very often exactly equal to the UTR
UTR = 120 bpm, PMT Rate = 120 bpm