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Pacemaker timing & advanced dual chamber concepts
- 1. Pacemaker Timing &Advanced Dual Chamber Concepts Dr D Sunil Reddy Consultant Cardiologist KIMS Hospital
- 2. Topics • Single ChamberTiming • The NBG Code • Dual Chamber Timing • Dual Chamber Pacing Modes • Upper Rate Behaviour • Timings in Rate-responsive Pacemakers
- 3. Single Chamber TimingTerminology • Lower rate & Lower Rate Interval • Refractory period • Blanking period • Upper Sensor Rate & Upper Sensor Rate Interval
- 4. VP VP VSVP 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 LRI LRI Lower Rate = 60, LRI = 1000 ms
- 5. Voltage Deflections oftheVoltage 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
- 6. Refractory PeriodRefractory Period RefractoryPeriod Refractory Period Refractory Period NO SENSING NO SENSING NO SENSING
- 7. Refractory Period Lower RateInterval 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
- 8. Refractory Period Lower RateInterval • 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
- 9.
- 10. Blanking Period Lower RateInterval 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 Period Refractory Period
- 11. Sensor-Indicated Rate • Thebasic 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
- 12. Activity Sensor • Fixedto the back of the can • Responds to – Pressure – Vibrations
- 13. Accelerometer Based ActivitySensor • 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
- 14. Upper Sensor RateInterval 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 Period Refractory Period Upper Sensor Rate Interval Sensor Indicated Rate
- 15. VOO Mode Blanking Period VPVP Lower Rate Interval VOO / 60 • Asynchronous pacing delivers output regardless of intrinsic activity
- 16. VPVPVP VP VOO TIMINGVOOTIMING
- 17. VPVPVP VP VOO TIMINGVOOTIMING V
- 18. VPVPVP VPVP VOO TIMINGVOOTIMING V
- 19. VP VPVPVP VP VOOTIMINGVOO TIMING V
- 20. VP VPVPVP VP VOOTIMINGVOO TIMING V
- 21. VP VPVPVPVP VOO TIMINGVOOTIMING V
- 22. VP VP VPVPVP VOOTIMINGVOO TIMING V
- 23. VP VP VPVPVP VOOTIMINGVOO TIMING V
- 24. V VP VPVP VOO TIMINGVOOTIMING VP VP
- 25. VVI Mode Lower RateInterval VP VS Blanking/Refractory VP { VVI / 60 • Pacing inhibited with intrinsic activity
- 26.
- 27.
- 28.
- 29.
- 30. VP VP VS VPVP VVI TIMINGVVITIMING V
- 31. VP VP VP VS VP VVITIMINGVVI TIMING V
- 32. VP VP VP VS VVITIMINGVVI TIMING VP V
- 33. VP VPVP VP VVITIMINGVVI TIMING V
- 34. VP VPVP VP VVITIMINGVVI TIMING V VS
- 35. VP VPVP VP VVITIMINGVVI TIMING V VS
- 36. V VP VPVP VP VS VVITIMINGVVI TIMING
- 37. VVI – RefractorySensing
- 38. VPVP VPVP VVI TIMINGVVITIMING
- 39.
- 40.
- 41.
- 42.
- 43.
- 44. VP VP VS VP VP V VVITIMINGVVI TIMING
- 45. VP VP VS VP VP V VR VVITIMINGVVI TIMING
- 46. VP VP VS VP VP VR V VVITIMINGVVI TIMING
- 47. V VVI TIMINGVVI TIMING VPVP VS VP VP VR
- 48. VVI Timing –T wave Oversensing
- 49.
- 50.
- 51.
- 52. VP VP VS VPVP VVI TIMINGVVITIMING V
- 53. VP VP VS VPVP VS VVI TIMINGVVITIMING V
- 54.
- 55.
- 56.
- 57. VP VP VS VP VS VP VVI TIMINGVVITIMING V
- 58. VP VP VS VP VS VP VVI TIMINGVVITIMING VS V
- 59. VP VP VS VS VP VS VP VVITIMINGVVI TIMING V
- 60. VP VP VS VS VP VS VVITIMINGVVI TIMING V VP
- 61.
- 62. V VVI TIMINGVVI TIMING VPVP VS VP VS VP VS T wave re-cycling
- 63. VP VR VR VRVRVR VPVP VVI TIMINGVVI TIMING
- 64. VP VR VR VRVRVR VPVP VVI TIMINGVVI TIMING V
- 65. VP VR VR VRVRVR VPVP VVI TIMINGVVI TIMING V VP
- 66. VP VP VR VRVRVR VR VPVP VVI TIMINGVVI TIMING V
- 67. VP VP VR VRVRVR VR VPVP VVI TIMINGVVI TIMING V VR
- 68. VP VP VRVR VRVRVR VR VPVP VVI TIMINGVVI TIMING V
- 69. VP VP VRVR VRVRVR VR VPVP VVI TIMINGVVI TIMING V VR
- 70. VP VP VRVR VRVRVR VR VPVP VVI TIMINGVVI TIMING V VR
- 71. VP VP VRVR VRVRVR VR VPVP VVI TIMINGVVI TIMING V VP VR
- 72. VP VP VP VRVRVR VRVR VR VPVP VVI TIMINGVVI TIMING V VR
- 73. VP VP VP VRVRVR VRVR VR VPVP VVI TIMINGVVI TIMING V VR
- 74. VP VP VP VRVRVR VRVR VR VP VVI TIMINGVVI TIMING V VR
- 75. VP VP VP VRVRVR VRVR VR VP VVI TIMINGVVI TIMING VP V VR
- 76. V VP VPVP VVI TIMINGVVITIMING VP VP VRVR VR VRVR VR Interference Operation VR
- 77. Noise Reversion VPVP SRSR SRSR Noise Sensed Lower Rate Interval VVI/60 • Continuous refractory sensing will cause pacing at the lower or sensor driven rate
- 78. VVIR VP VP Refractory/Blanking Lower Rate UpperRate Interval (Maximum Sensor Rate) VVIR / 60/120 Rate Responsive Pacing at the Upper Sensor Rate • Pacing at the sensor-indicated rate (= Upper Rate Interval)
- 79. AAIR Lower Rate Interval APAP Refractory/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
- 80. VP VP VSVP Lower Rate Interval-60 ppm Hysteresis • Allows the rate to fall below the programmed lower rate following an intrinsic beat Hysteresis Rate-50 ppm
- 81. Dual Chamber Timing(DDD or Universal Mode)
- 82. NBG Code Review I Chamber Paced II Chamber Sensed III Response toSensing IV Programmable Functions/Rate Modulation V Antitachy Function(s) V: Ventricle V: Ventricle T: Triggered P: Simple programmable 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
- 83. NBG Code Revised- 2002 I Chamber Paced II Chamber Sensed III Response to Sensing IV Programmable Functions/Rate Modulation V Multi 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
- 84. Rate = 60bpm / 1000 ms A-A = 1000 ms AP VP AP VP V-AAV V-AAV • Atrial Pace, Ventricular Pace (AP/VP) Four “Faces” of DDD Pacing
- 85. Rate = 60ppm / 1000 ms A-A = 1000 ms AP VS AP VS V-AAV V-AAV • Atrial Pace, Ventricular Sense (AP/VS) Four “Faces” of DDD Pacing
- 86. AS VP AS VP Rate (sinus driven)= 70 bpm / 857 ms A-A = 857 ms • Atrial Sense, Ventricular Pace (AS/ VP) V-AAV AV V-A Four “Faces” of DDD Pacing
- 87. Rate (sinus driven)= 70 bpm / 857 ms Spontaneous conduction at 150 ms A-A = 857 ms AS VS AS VS V-AAV AV V-A • Atrial Sense, Ventricular Sense (AS/VS) Four “Faces” of DDD Pacing
- 88. DDD Timing Parameters •Lower rate & Lower Rate Interval • AV and VA intervals • Upper Tracking Rate & Interval • Refractory periods • Blanking periods
- 89. Lower Rate Interval AP VP AP VP LowerRate • 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
- 90. AP VP AS VP AVI AVI Lower RateInterval 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
- 91. PAV Typical Programming forCHB SAV = 120 ms, PAV = 150 ms
- 92. Lower Rate Interval AP VP AP VP AVInterval 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 / 120 PAV 200 ms; V-A 800 ms 200 ms 800 ms 1000 ms
- 93. 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
- 94. Lower Rate Interval AP VP AP VP VAInterval Atrial Escape Interval (V-A Interval) DDD 60 / 120 PAV 200 ms; V-A 800 ms 200 ms 800 ms 1000 ms PV C
- 95. AS VP AS VP DDDR 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
- 96. Programing Upper Tracking Rate •Typically programmed to 120 bpm • Young, active patients – 150 to 180 bpm • Patients with angina – 100 to 110 bpm
- 97. Refractory Periods • VentricularRefractory Period (VRP) • Post-ventricular Atrial Refractory Period (PVARP) • Total Atrial Refractory Period (TARP) Separate Amplifiers • Atrial Channel • Ventricular Channel
- 98. 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)
- 99. 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
- 100. Post Ventricular Atrial RefractoryPeriod (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
- 101. PVARP Upper Tracking Rate LowerRate Interval { No SAV started for events sensed in the TARP AS AS VPVP SAV = 200 ms PVARP = 300 ms Thus TARP = 500 ms (120 ppm) DDD LR = 60 ppm (1000 ms) UTR = 100 bpm (600 ms) Sinus rate = 66 bpm (900 ms) SAV TARP PVARP Total Atrial Refractory Period (TARP) • Sum of the AV Interval and PVARP SAV
- 102. What is happening DDD/ 70 / 120
- 103. Issue: Crosstalk • Crosstalkis the sensing of a pacing stimulus delivered in the opposite chamber, which results in undesirable pacemaker response, e.g., false inhibition DDD / 70 / 120
- 104. Blanking Periods • Firstportion 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 VP AP Post Ventricular Atrial Blanking (PVAB) (Programmable) Post Atrial Ventricular Blanking (Programmable) Ventricular Blanking (Nonprogrammable) Atrial Blanking (Nonprogrammable)
- 105. Dual Chamber Modes& their Timing
- 106. DDD Mode- UniversalMode • 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
- 107. 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
- 108. VP VP AP AP V A VRP DDDTIMINGDDD TIMING
- 109. VP VP AP AP V A VRP VP DDDTIMINGDDD TIMING
- 110. VP VP VP APAP V A V-A Interval V-A Interval DDD TIMINGDDD TIMING VRPVRP
- 111.
- 112.
- 113. VP A V PVARPPVARP VP VP AP DDD TIMINGDDDTIMING VRPVRP PVARPPVARP
- 114. VP AP A V PVARPPVARP VP DDD TIMINGDDD TIMING VRPVRP PVARPPVARPAV RP A-V Interval A-V Interval
- 115.
- 116. VP VP AP A V DDD TIMINGDDDTIMING PVARPPVARP VRPVRP VP AV RPAV RPPVARPPVARP VRPVRP
- 117. VP VP AP A V DDD TIMINGDDDTIMING PVARPPVARP VRPVRP VP AV RPAV RPPVARPPVARP PVARPPVARP VRPVRP
- 118. VP VP AP A V DDD TIMINGDDDTIMING PVARPPVARPAV RPAV RP PVARPPVARP VRPVRP VP AP
- 119. VP VP AP AP A V DDDTIMINGDDD TIMING PVARPPVARPAV RPAV RP PVARPPVARP VRPVRP AV RP VP
- 120. VP VP AP AP A V DDDTIMINGDDD TIMING AV RPAV RP PVARPPVARP VRPVRP VP
- 121. VP VP AP AP A V DDDTIMINGDDD TIMING VP
- 122. DDD Mode • AsVs– Pacemaker Inhibited • Sinus Rate greater than programmed Lower Rate • Normal intrinsic AV conduction
- 123. AS AS AS VSVS VS AS VS AS DDD TIMINGDDD TIMING
- 124. AS AS AS VSVS VS AS VS AS A V DDD TIMINGDDD TIMING
- 125. AS AS AS VSVS VSVS ASAS A V DDD TIMINGDDD TIMING
- 126. AS AS ASAS VSVS VSVS AS A V DDD TIMINGDDD TIMING
- 127. AS AS ASAS VSVS VSVS AS A V DDD TIMINGDDD TIMING VS
- 128. AS AS ASAS VSVS VS VSVS AS A V DDD TIMINGDDD TIMING
- 129. AS AS ASAS VSVS VS VSVS AS A V DDD TIMINGDDD TIMING
- 130. ASAS AS ASAS DDDTIMINGDDD TIMING VS VS VS VS VS A V Pacemaker Inhibited
- 131. DDD Mode • ApVs– Atrial Pacing Ventricular Inhibition • Sinus Rate lower than programmed Lower Rate • Intrinsic AV Conduction
- 132. VS VS AP AP VSVS AP DDDTIMINGDDD TIMING
- 133. VS VS AP AP VSVS AP A V DDDTIMINGDDD TIMING
- 134. VS VS AP AP VSVS AP A V DDDTIMINGDDD TIMING AP
- 135. VS VS AP AP VSVS AP A V DDDTIMINGDDD TIMING AP
- 136. VS VS AP APAP VS AP A V DDD TIMINGDDD TIMING
- 137. VS VS AP APAP VS AP A V DDD TIMINGDDD TIMING VS
- 138. VS VS VS APAP AP VS AP A V DDD TIMINGDDD TIMING
- 139. VS VS VSVS AP AP AP AP A V DDD TIMINGDDD TIMING Atrial Pacing - Ventricular inhibition
- 140. 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
- 141. AS VP VP VP ASAS VP ASAS DDD TIMINGDDD TIMING
- 142. AS VP VP VP ASAS VP ASAS A V DDD TIMINGDDD TIMING
- 143. AS VP VP VP ASAS VP AS A V AS DDD TIMINGDDD TIMING
- 144. AS VP VP VP ASASAS VP AS A V DDD TIMINGDDD TIMING
- 145. AS VP VP VP ASASAS VP AS A V DDD TIMINGDDD TIMING
- 146. AS VP VP VP ASASAS VP AS VP A V DDD TIMINGDDD TIMING
- 147. VP AS VP VP VP ASASAS VP AS A V DDD TIMINGDDD TIMING
- 148. A V VP AS VP VP VPVP AS AS ASAS DDD TIMINGDDD TIMING Atrial Tracking
- 149. DDI Mode • A-Vsequential 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
- 150. A V VS PVARPPVARP VRPVRP ARP PVARPPVARP ARPPVARPPVARP ARP AS VP PVARPPVARP AS VP ARPARPPVARPPVARP AP AV RPAV RP DDI TIMINGDDI TIMING
- 151. A V VS PVARPPVARP VRPVRP ARP PVARPPVARP ARPPVARPPVARP ARP AS VP PVARPPVARP AS VP ARPARPPVARPPVARPAV RPAV RP AP DDI TIMINGDDI TIMING
- 152. AP A V VS PVARPPVARP VRPVRP ARP PVARPPVARP ARPPVARPPVARP ARP AS VP PVARPPVARP AS VP ARPARPPVARPPVARP DDI TIMINGDDI TIMING AV RPAV RP
- 153. AP A V VS PVARPPVARP VRPVRP ARP PVARPPVARP ARPPVARPPVARP ARP AS VP PVARPPVARP AS ARPARPPVARPPVARP VP DDI TIMINGDDI TIMING A-VInterval AV RPAV RP
- 154. A-VInterval AP A V VP VS VRPVRP ARP PVARPPVARPARP PVARPPVARP ARP AS VP PVARPPVARP AS ARPARP DDI TIMINGDDI TIMING AV RPAV RP PVARPPVARP
- 155. AP A V VP VS VRPVRP ARP PVARPPVARPARP PVARPPVARP ARP AS VP PVARPPVARPARPARP AS DDI TIMINGDDI TIMING AV RPAV RP PVARPPVARP A-VInterval V-A Interval V-A Interval
- 156. AP A V VP VS VRPVRP ARP PVARPPVARPARP PVARPPVARP ARP AS VP PVARPPVARPARPARP AS DDI TIMINGDDI TIMING AV RPAV RP PVARPPVARP A-VInterval V-A Interval V-A Interval
- 157. AP A V AS VP VS PVARPPVARP ARPPVARPPVARP ARP AS VP PVARPPVARP DDI TIMINGDDI TIMING ARPARPAV RPAV RP A-VInterval
- 158. AP A V AS VP VS PVARPPVARP ARPPVARPPVARP ARP AS PVARPPVARP DDI TIMINGDDI TIMING VP ARPARPAV RPAV RP A-VInterval
- 159. DDI TIMINGDDI TIMING AP A V ASAS VP VP ARPARP A-VInterval AV RPAV RP ARP V-A Interval V-A Interval PVARPPVARP VRPVRP
- 160. DDI TIMINGDDI TIMING AP A V ASAS VP VP ARPARP A-VInterval AV RPAV RP V-A Interval V-A Interval PVARPPVARP ARP
- 161. DDI TIMINGDDI TIMING AP A V ASAS VP VP ARPARPARP A-VInterval AV RPAV RP V-A Interval V-A Interval PVARPPVARP
- 162. DDI TIMINGDDI TIMING AP A V ASAS VP VP VS ARPARPARP A-VInterval AV RPAV RP
- 163. DDI TIMINGDDI TIMING AP A V ASAS VP VP VS VRPVRP ARPARPARP A-VInterval PVARPPVARPAV RPAV RP
- 164. DDI TIMINGDDI TIMING AP A V ASAS VP VP VS ARPARPARPARPAV RPAV RP A-VInterval PVARPPVARPPVARPPVARP V-A Interval PVARPPVARP V-A Interval VRPVRP
- 165. DDI TIMINGDDI TIMING AP A V ASAS VP VP VS
- 166. DDI/R Lower Rate Interval DDI60 PAV = 200 ms PVARP = 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
- 167. VDD Mode • AtrialSynchronous 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
- 168.
- 169. MVP Basic Operation AAI(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.
- 170. MVP Basic Operation VentricularBackup Ventricular pacing only as needed in the presence of transient loss of conduction
- 171. MVP Basic Operation DDD(R)Switch Ventricular support if loss of A-V conduction is persistent
- 172.
- 173. Issue: Crosstalk • Crosstalkis the sensing of a pacing stimulus delivered in the opposite chamber, which results in undesirable pacemaker response, e.g., false inhibition DDD / 70 / 120
- 174. Solution: Ventricular SafetyPacing • 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
- 175. PVARP Ventricular Safety Pace AVPVARP PVARP AV 110 ms VS VPVP VP AP APAP
- 176. VS VS VS APAPAP DDDTIMINGDDD TIMING
- 177. VS VS VS APAPAP A V DDDTIMINGDDD TIMING
- 178. VS VS VS APAPAPAP A V DDDTIMINGDDD TIMING
- 179. VS VS VS APAPAPAP A V DDD TIMINGDDD TIMING
- 180. VS VS VS APAPAP A V DDD TIMINGDDD TIMING AP
- 181. VS VS VS APAP APAP A V DDD TIMINGDDD TIMING
- 182. VS VS VS APAP APAP A V VSP DDD TIMINGDDD TIMING
- 183. VS VS VS APAP AP VSP AP DDD TIMINGDDD TIMING A V
- 184. DDD TIMINGDDD TIMING VSVS VS AP AP AP VSP A V AP
- 185. A V DDD TIMINGDDD TIMING VSVS VS AP AP AP AP VSP Ventricular Safety Pacing
- 186. Ventricular Safety Pace DDD60 / 120
- 187. 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
- 188. Other Methods forManaging 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
- 189.
- 190. 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
- 191. The Upper TrackingRate • 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
- 192. PVARP Upper Tracking Rate LowerRate Interval { P Waves Blocked AS AS VPVP SAV = 200 ms PVARP = 300 ms Thus TARP = 500 ms (120 ppm) DDD LR = 60 ppm (1000 ms) UTR = 100 bpm (600 ms) Sinus rate = 66 bpm (900 ms) SAV TARP PVARP Total Atrial Refractory Period (TARP) • Sum of the AV Interval and PVARP SAV
- 193. TARP • The atrialchannel 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
- 194. TARP Rate • TARP= SAV + PVARP (during atrial sensed rhythms) • If SAV = 150 ms and PVARP = 350 ms, TARP = 500 ms TARP 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
- 195. Fixed Block or2:1 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
- 196. • Every otherP wave falls into refractory and does not restart the timing interval Upper Tracking Limit Lower Rate Interval { { P Wave Blocked AS AS VPVP ARAR Sinus rate = 133 bpm (450 ms) PVARP = 300 ms SAV = 200 ms Tracked rate = 66 bpm (900 ms) AV PVARP AV PVARP TARP TARP 2:1 Block
- 197.
- 198. AS AS VP VP ASAS ARARAR VPVP AR AS VP A V DDD TIMINGDDD TIMING
- 199. AS AS VP VP ASAS ARARAR VPVP AR VP A V DDD TIMINGDDD TIMING AS
- 200. AS AS AS VPVP AS AS ARARAR VPVP AR A V DDD TIMINGDDD TIMING VP
- 201. AS VP AS VP VP AS AS ARARAR VPVP AR AS A V DDDTIMINGDDD TIMING
- 202. AS VP AS VP VP AS AS ARARAR VPVP AR A V DDDTIMINGDDD TIMING
- 203. AS VP AS VP VP AS AS ARARAR VPVP AR AS A V DDDTIMINGDDD TIMING
- 204. AS VP AS AS VP VP ASAS ARARAR VP AR VP A V DDD TIMINGDDD TIMING
- 205. AS VP VP AS AS VPVP AS AS ARARAR VP AR A V DDD TIMINGDDD TIMING
- 206. AS VP VP AS AS VPVP AS AS ARARAR VP A V AR DDD TIMINGDDD TIMING
- 207. AS VP VP AS AS VPVP AS AS AR ARARAR VP A V DDD TIMINGDDD TIMING
- 208. AS VP VP AS AS VPVP AS AS AR ARARAR VP A V DDD TIMINGDDD TIMING
- 209. AS VP VP AS VP VP ASAS AR ARARAR VP A V DDD TIMINGDDD TIMING AS
- 210. AS VP VP AS AS VPVP AS AS AR ARARAR VP A V DDD TIMINGDDD TIMING
- 211. AS VP VP AS AS VPVP VP AS AS AR ARARAR A V DDD TIMINGDDD TIMING
- 212. DDD TIMINGDDD TIMING AS VPVP AS AS VP VP VP AS AS AR ARARAR A V
- 213. DDD TIMINGDDD TIMING AS VPVP AS AS VP VP VP AS AS AR ARARAR A V 2:1 Block
- 214. Wenckebach Operation • Occurswhen 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
- 215. PVARP Wenckebach Operation Upper TrackingRate Lower Rate Interval { AS AS AR AP VPVP VP TARP SAV PAV PVARPSAV 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
- 216.
- 217.
- 218. ASAS AS AR VPVP AS VP VPVP AS DDDTIMINGDDD TIMING A V AS
- 219. ASAS AS AS AR VPVP AS VPVP AS DDD TIMINGDDD TIMING VP A V
- 220. VP ASAS AS AS AR VPVP AS VPVP AS DDD TIMINGDDD TIMING A V
- 221. VP ASAS AS AS AR VPVPVPVP ASAS A V DDD TIMINGDDD TIMING
- 222. VP AS ASAS ASAS AR VPVPVP VP AS A V DDD TIMINGDDD TIMING
- 223. VP AS ASAS ASAS AR VPVP AS VP A V DDD TIMINGDDD TIMING VP
- 224. VP VP AS ASASAS AS AR VPVP VP A V AS DDD TIMINGDDD TIMING
- 225. VP AS VP AS ASAS ASAS AR VP VPVP DDD TIMINGDDD TIMING A V
- 226. VP AS VP AS ASAS ASAS AR VPVP A V DDD TIMINGDDD TIMING VP
- 227. VP AS VP VP AS ASASAS AS AR VPVP A V DDD TIMINGDDD TIMING
- 228. VP AS VP VP AS ASASAS AS AR VPVP DDD TIMINGDDD TIMING A V
- 229. VP AS VP VP AS ASAS DDDTIMINGDDD TIMING AS AS AR VP A V VP
- 230. VP AS VP VP VP ASASAS DDD TIMINGDDD TIMING AS AS AR A V VP
- 231. A V VP AS VP VP VP ASASAS DDD TIMINGDDD TIMING AS AS AR VP Wenckebach Behaviour
- 232. Wenckebach or 2:1block 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
- 233. Wenckebach vs. 2:1Block – What Will Happen First? What will the upper rate behavior of this pacemaker be? Lower rate = 60 ppm Upper tracking rate = 120 ppm PAV = 230 ms SAV = 250 ms PVARP = 350 ms
- 234. Wenckebach vs. 2:1Block – Solution Upper tracking rate = 120 ppm PVARP = 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
- 235. Wenckebach vs. 2:1Block – What Will Happen First? What will the upper rate behavior of this pacemaker be? Lower rate = 60 ppm Upper tracking rate = 100 ppm PAV = 150 ms SAV = 150 ms PVARP = 350 ms
- 236. Wenckebach vs. 2:1Block – Solution Upper tracking rate = 100 ppm PVARP = 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 bpm Wenckebach behaviour will persist until atrial rate exceeds 120 (TARP rate), after which 2:1 block will commence
- 237. What Can WeDo to Make Wenckebach Occur First? • Shorten or reduce the TARP by: – Shortening the PVARP – Shortening the SAV – Automatic PVARP
- 238. DDDR 60 /120 A-A = 500 ms AP VP AP VP 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
- 239. UAR versus UTR UTR Theventricle 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 UAR e.g. 140 bpm Both atrium and subsequently the ventricle may be paced up to 140 bpm
- 240.
- 241. Pacemaker Mediated Tachycardias • Anytachycardia 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
- 242. 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
- 243.
- 244. PMT • Loss ofAV 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
- 245. PMT Prevention • PreventRetrograde 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
- 246. 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
- 247. UTR = 120bpm, PMT Rate = 120 bpm
Editor's Notes
- #2 Good afternoon ladies and gentlemen. It was with great pleasure that I accepted this invitation to discuss heart rate management in the pacing population. I have enjoyed participating in the evolution of rate-adaptive pacing for the past twleve years, and I am truly excited about Kappa’s contribution to clinical practice. To fully appreciate Kappa’s rate response features, it is important to first understand normal daily submaximal heart rate behavior.
- #5 Single chamber timing has three components: Lower rate interval Refractory period Blanking period Single chamber devices that are programmed to a rate responsive mode add a fourth component, the upper rate interval.
- #9 During refractory periods, the pacemaker “sees” but is unresponsive to any signals. This is designed to avoid restarting the lower rate interval in the event of oversensing. T-wave oversensing in VVI and AAI modes will occur if refractory periods are too short. In the AAI mode, the pacemaker may even sense the QRS complex (“far-field R wave”) if the refractory period is not long enough. Events that fall into the refractory period are sensed by the pacemaker (the marker channel will display a “SR” denoting ventricular refractory or atrial refractory in single chamber systems) but the timing interval will remain unaffected by the sensed event. A refractory period is started by a paced, non-refractory, or refractory sensed event.
- #10 During refractory periods, the pacemaker “sees” but is unresponsive to any signals. This is designed to avoid restarting the lower rate interval in the event of oversensing. T-wave oversensing in VVI and AAI modes will occur if refractory periods are too short. In the AAI mode, the pacemaker may even sense the QRS complex (“far-field R wave”) if the refractory period is not long enough. Events that fall into the refractory period are sensed by the pacemaker (the marker channel will display a “SR” denoting ventricular refractory or atrial refractory in single chamber systems) but the timing interval will remain unaffected by the sensed event. A refractory period is started by a paced, non-refractory, or refractory sensed event.
- #12 A paced or sensed event will initiate a blanking period. Blanking is a method to prevent multiple detection of a single paced or sensed event by the sense amplifier (e.g., the pacemaker detecting its own pacing stimuli or depolarization, either intrinsic or as a result of capture). During this period, the pacemaker is &quot;blind&quot; to any electrical activity. A typical blanking period duration in a single-chamber mode is 100 msec*. Note: In Thera and Kappa devices, nonprogrammable blanking parameters are dynamic (ranging from 50-100 ms) depending on the strength/duration of the paced or sensed signal.
- #15 Accelerometers are used with the Sigma and Kappa 700 family of pacemakers. It does not respond to pressure waves like the piezoelectric crystal, however, it interprets the data the same way.
- #16 The upper sensor rate interval in single chamber pacing is available only in rate-responsive modes. The upper rate defines the limit at which sensor-driven pacing can occur.
- #17 VOO mode paces in the ventricle but will not sense and, therefore, has no response to cardiac events. Pacemakers programmed to the VVI, VVIR, and VDD modes will revert to VOO mode upon magnet application. In this example, an intrinsic beat occurs, but it has no effect on the timing interval and another ventricular pace is delivered at the programmed rate. No sensing occurs, thus, the entire lower rate interval is unresponsive to intrinsic activity.
- #27 In inhibited modes (VVI/AAI), intrinsic events that occur before the lower rate interval expires will reset the lower rate interval, as shown in the example above. As with paced events, sensed events will also initiate blanking and refractory periods.
- #79 The portion of the refractory period after the blanking period ends is commonly called the &quot;noise sampling period.&quot; This is because a sensed event in the noise sampling period will initiate a new refractory period and blanking period. If events continue to be sensed within the noise sampling period causing a new refractory period each time, the pacemaker will asynchronously pace at the lower rate since the lower rate timer is not reset by events sensed during the refractory period. This behavior is known as &quot;noise reversion.&quot; Note: In rate-responsive modes, noise reversion will cause pacing to occur at the sensor-driven rate.
- #80 Single chamber rate-responsive pacing is identical to non-rate responsive pacing operation, with the exception that the pacing rate is driven by a sensor. The sensor determines whether or not a rate increase is indicated, and adjusts the rate accordingly. The highest rate that the pacemaker is allowed to pace is the upper rate limit or interval. In this example, the pacemaker is pacing at the maximum sensor indicated rate of 120 ppm.
- #81 Although this mode is seldom used (particularly in the USA) , AAI/R pacing is a mode which, unlike VVI/R, allows for normal AV conduction to occur. AAI/R is not often used because of the risk of development of AV block which can occur over time. In this example, the patient received a single chamber device programmed to the AAIR pacemaker mode due to sick sinus syndrome and chronotropic incompetence. Presently the patient is at rest, so the sensor is at the programmed lower rate. An atrial event (paced or sensed) will initiate a refractory period including a blanking period. As previously stated, in AAI/R, the refractory period must be long enough so that the far-field R and T waves are ignored. Therefore, the refractory period must be longer in the AAI/R mode than in the VVI/R mode—typically 400 msec. Atrial events sensed during the refractory period in AAI/R are marked with an &quot;SR&quot; on the marker channel.
- #82 Hysteresis allows the sensed intrinsic rate to decrease to a value below the programmed lower rate before pacing resumes. Hysteresis provides the capability to maintain the patient&apos;s own heart rhythm as long as possible, while pacing at a faster rate if the intrinsic rhythm falls below the hysteresis rate. The hysteresis rate is always &lt; the lower rate limit. The lower rate limit is initiated by a paced event, while the hysteresis rate is initiated by a non-refractory sensed event. In the example above, the lower rate limit is 60 ppm (1000 ms), while the hysteresis rate is 50 ppm (1200 ms). The patient is paced at 60 ppm until an intrinsic event occurs, and an interval of 1200 ms is started. This patient did not have another sensed event, so a ventricular pace was delivered. However, if another sensed event had occurred, the pacemaker would again have extended the interval to 1200 ms.
- #86 Knowing the basic A-V and V-A intervals will help in understanding the four modes or “faces” of dual chamber pacing. In the first example, the pacemaker is pacing in both the atrium and the ventricle–most likely a patient with sinus node dysfunction and AV block.
- #87 In this example, the atrium is being paced, but AV conduction is intact, so the ventricular output is inhibited by a sensed ventricular event.
- #88 In this example, the atrial rate is driving the ventricular rate–also called atrial tracking. This patient has adequate sinus node function with AV block.
- #89 In this example, the patient has adequate sinus node function and intact AV conduction, but may experience little to no increase in sinus rate with activity and/or AV block that occurs at increased rates. At appropriate rates, it is best to try and utilize the patient’s intrinsic rhythm when possible.
- #90 Dual-chamber pacing requires attention to these parameters: Lower rate AV and V-A intervals Upper rates Refractory periods Blanking periods
- #91 In order to provide optimal hemodynamic benefit to the patient, dual-chamber pacemakers strive to mimic the normal heart rhythm. In dual-chamber pacemakers, the lower rate is the rate at which the pacemaker will pace the atrium in the absence of intrinsic atrial activity. Similar to single-chamber timing, the lower rate can be converted to a lower rate interval (A-A interval), or the longest period of time allowed between atrial events.
- #92 The SAV is usually programmed to a shorter duration than the PAV to allow for the difference in interatrial conduction time between intrinsic and paced atrial events. Think of the difference in the activation sequence between a cycle initiated with an intrinsic atrial event versus a paced atrial event. The cycle starting with the intrinsic atrial event will use the normal conduction pathways between the right atrium and the left atrium. The cycle starting with the paced atrial beat will not use the normal interatrial conduction pathways but will instead use muscle tissue, which takes a little longer to reach the left atrium and causing it to contract. If the AV interval is timed to allow the appropriate amount of time for left ventricular filling when the cycle is initiated with a sensed atrial event, the same duration for the PAV may not be the appropriate amount of time to allow for left ventricular filling when the cycle is initiated by a paced atrial event. Proper LA-LV timing promotes left ventricular filling (&quot;atrial kick&quot;) and prevents regurgitant flow through an open mitral valve. Therefore, it is beneficial to have separately programmable PAV and SAV intervals. In this example, the lower rate interval is terminated by a sensed atrial event, which initiates a SAV interval (and restarts the the lower rate interval).
- #96 Knowing the lower rate interval and the PAV interval (A-V interval after a paced atrial event), the V-A interval can be found: V-A interval = lower rate interval minus the AV interval. The V-A interval is the longest period that may elapse after a ventricular event before the atrium must be paced in the absence of atrial activity. The V-A interval is also commonly referred to as the atrial escape interval.
- #97 The A-V interval is employed to allow the appropriate amount of time to optimize ventricular filling and mimic the activation sequence of the normal heart. Knowing the lower rate interval and the PAV interval (A-V interval after a paced atrial event), the V-A interval can be found: V-A interval = lower rate interval minus PAV interval. The V-A interval is the longest period that may elapse after a ventricular event before the atrium must be paced in the absence of atrial activity. The V-A interval is also commonly referred to as the atrial escape interval.
- #98 Knowing the lower rate interval and the PAV interval (A-V interval after a paced atrial event), the V-A interval can be found: V-A interval = lower rate interval minus the AV interval. The V-A interval is the longest period that may elapse after a ventricular event before the atrium must be paced in the absence of atrial activity. The V-A interval is also commonly referred to as the atrial escape interval.
- #99 The sequence of an atrial intrinsic event being sensed, starting an SAV interval, timing out the SAV interval, and pacing in the ventricle can be referred to as &quot;tracking.&quot; If the atrial rate begins to increase and continues to increase, is it desirable to let the ventricle &quot;track&quot; to extremely high rates? No. It is desirable to limit the rate at which the ventricle can pace in the presence of high atrial rates. This limit is called the upper tracking rate.
- #102 The Post-Ventricular Atrial Refractory Period (PVARP) is the period of time after a ventricular pace or sense when the atrial channel is in refractory. In other words, atrial senses outside of blanking that occur during this period are &quot;seen&quot; (and marked “AR) on the marker channel), but do not initiate an AV interval. The purpose of PVARP is to avoid allowing retrograde P waves, far-field R waves, or premature atrial contractions to start an AV interval which would cause the pacemaker to pace in the ventricle at a high rate. The refractory period after a ventricular event (paced or sensed) is designed to avoid restarting of the V-A interval due to a T wave. Ventricular sensed events occurring in the noise sampling portion of the ventricular refractory period are &quot;seen&quot; (and marked “VR” on the marker channel) but will not restart the V-A interval. The atrial channel is refractory following a paced or sensed event during the AV interval. This allows atrial senses occurring in the AV interval to be &quot;seen&quot; but not restart another AV interval .
- #104 The Post-Ventricular Atrial Refractory Period (PVARP) is the period of time after a ventricular pace or sense when the atrial channel is in refractory. In other words, atrial senses outside of blanking that occur during this period are &quot;seen&quot; (and marked “AR) on the marker channel), but do not initiate an AV interval. The purpose of PVARP is to avoid allowing retrograde P waves, far-field R waves, or premature atrial contractions to start an AV interval which would cause the pacemaker to pace in the ventricle at a high rate. The refractory period after a ventricular event (paced or sensed) is designed to avoid restarting of the V-A interval due to a T wave. Ventricular sensed events occurring in the noise sampling portion of the ventricular refractory period are &quot;seen&quot; (and marked “VR” on the marker channel) but will not restart the V-A interval. The atrial channel is refractory following a paced or sensed event during the AV interval. This allows atrial senses occurring in the AV interval to be &quot;seen&quot; but not restart another AV interval .
- #105 The total time that the atrial chamber of the pacemaker is in refractory is during the AV interval and during the PVARP. The Total Atrial Refractory Period (TARP) is equal to the SAV interval plus the PVARP. The TARP is important to understand as it defines the highest rate that the pacemaker will track atrial events before 2:1 block occurs.
- #106 Crosstalk is a phenomenon that occurs when one chamber senses the output pulse of the other chamber. Crosstalk can become a problem when one chamber senses the output of the other chamber and is inhibited. If the ventricular chamber is inhibited by the atrial pacing pulse, as seen in the third complex above, the ventricular output is withheld. In this particular example, crosstalk inhibition is intermittent but the outcome could be disastrous if it occurred with every paced atrial beat. If the ventricular lead is &quot;blanked&quot; for an adequate period of time after the atrial pacing pulse to avoid seeing the atrial pacing pulse, crosstalk inhibition will not occur. Programmable ventricular blanking after an atrial pace is one method used to address the problem of crosstalk. Another solution is ventricular safety pacing.
- #107 Crosstalk is a phenomenon that occurs when one chamber senses the output pulse of the other chamber. Crosstalk can become a problem when one chamber senses the output of the other chamber and is inhibited. If the ventricular chamber is inhibited by the atrial pacing pulse, as seen in the third complex above, the ventricular output is withheld. In this particular example, crosstalk inhibition is intermittent but the outcome could be disastrous if it occurred with every paced atrial beat. If the ventricular lead is &quot;blanked&quot; for an adequate period of time after the atrial pacing pulse to avoid seeing the atrial pacing pulse, crosstalk inhibition will not occur. Programmable ventricular blanking after an atrial pace is one method used to address the problem of crosstalk. Another solution is ventricular safety pacing.
- #108 DDD/R modes have four types of blanking periods: A non-programmable atrial blanking period (varies from 50-100 msec) is initiated each time the atrium paces or senses. This is to avoid the atrial lead sensing its own pacing pulse or P wave (intrinsic or captured). In Thera and Kappa devices, this blanking period is dynamic, depending on the strength of the paced/sensed signal. The PVAB-(Post-Ventricular Atrial Blanking Period) is initiated by a ventricular pace or sensed event (nominally set at 220 msec) to avoid the atrial lead sensing the far-field ventricular output pulse or R wave. In dual-chamber timing, a non-programmable ventricular blanking period occurs after a ventricular paced or sensed event to avoid sensing the ventricular pacing pulse or the R wave (intrinsic or captured). This period is 50-100 msec in duration and is dynamic, based on signal strength. There also is a ventricular blanking period after an atrial pacing pulse in order to avoid sensing the far-field atrial stimulus (crosstalk). This period is programmable (nominally set at 28 msec). This blanking period is relatively short because it is important not to miss ventricular events (e.g., PVCs) that occur early in the AV interval. Ventricular blanking does not occur coincident with an atrial sensed event. This is because the intrinsic P wave is relatively small and will not be far-field sensed by the ventricular lead. The issue of ventricular safety pacing and cross-talk will be addressed later on in the presentation. A note of caution in programming long ventricular blanking periods after an atrial pace should be mentioned. If the ventricular blanking period after an atrial pace is excessively long, conducted ventricular events may go unsensed and cause the pacemaker to pace in the ventricle after the AV interval expires. This pace could occur before the ventricle has recovered from depolarization and may induce a ventricular arrhythmia (R on T phenomena).
- #181 This is an example of normal DDI/R operation. In the DDI/R mode, the pacemaker will pace in both chambers and sense in both chambers. In response to sensing, the pacemaker will inhibit, but a sensed P wave will not trigger an AV Interval (therefore, there is no SAV Interval in the DDI/R mode). DDI/R pacing can be thought of as AAI/R with VVI/R backup. In DDI mode the device is not tracking the atrial events, so pacing in V and A is always at lower rate. In the case of faster AS, the unit can not control the faster atrial rate, but it will not increase the pacing rate in Ventricle and hence continue to pace at lower rate in V. (As a result you see changing AV delays). DDIR works identical like DDI, but the sensor controls the Lower Rate and can make it pace faster and slower than programmed Lower Rate, following the sensor.
- #186 The following three slides graphically depict the three main phases of operation of the MVP pacing mode. Primarily, MVP looks like AAI(R) mode, EXCEPT that it allows for prolonged A-V. It is an atrial-based pacing mode that looks for any consecutive A-A intervals without associated ventricular events. AAI(R) Figure: If your patient has AV conduction, the device will operate in AAI(R) mode. The device will allow prolonged AV intervals and occasional, single, non-conducted normal atrial contractions. Programming Recommendation – For patients with long PR intervals, the device will remain in AAI(R) mode. Permanent DDDR or DDD modes may be more appropriate if the patient is symptomatic with first degree block. The next slide shows operation for transient loss of conduction (backup V-pacing).
- #187 Ventricular Backup Figure: For occasional, single, non-conducted normal atrial contractions, the device will provide backup ventricular pacing to ensure ventricular support. The backup VP occurs at 80 ms post the AP event (or inhibited AP if an AS occurs prior to it).
- #188 DDD(R) Switch Figure: If your patient develops persistent loss of conduction, the device will automatically switch to DDD(R) operation, but continue to periodically look for restored conduction. Persistent loss of conduction is detected whenever 2 out of the previous 4 A-A intervals have no conducted VS event. Note: Backup V-pacing will occur after each of the dropped beat intervals. Once the transition to DDD(R) occurs, the PAV and SAV values will operate at their permanently programmed settings. To avoid pacing the ventricle at long AV delays (upon loss of conduction), it is recommended that PAV and SAV remain at their nominal/shipped settings.
- #190 Crosstalk is a phenomenon that occurs when one chamber senses the output pulse of the other chamber. Crosstalk can become a problem when one chamber senses the output of the other chamber and is inhibited. If the ventricular chamber is inhibited by the atrial pacing pulse, as seen in the third complex above, the ventricular output is withheld. In this particular example, crosstalk inhibition is intermittent but the outcome could be disastrous if it occurred with every paced atrial beat. If the ventricular lead is &quot;blanked&quot; for an adequate period of time after the atrial pacing pulse to avoid seeing the atrial pacing pulse, crosstalk inhibition will not occur. Programmable ventricular blanking after an atrial pace is one method used to address the problem of crosstalk. Another solution is ventricular safety pacing.
- #191 One method to manage crosstalk is to program Ventricular Safety Pacing (VSP) ON. If VSP is programmed ON, a ventricular safety pace window opens up for 110 msec after an atrial pace. The first portion of this window (about 28 msec) is blanked. After the blanking period ends, if a ventricular event is sensed within 110 msec after the atrial pace, the pacemaker will pace at the end of the 110 msec window. The logic here is that it is assumed that if a sensed event happens within 110 msec of an atrial pace, it may not have happened as a result of conduction to the ventricle (i.e., it is not physiologic), and it may be crosstalk or noise. Rather than inhibit the ventricular pace and risk having no ventricular support, the pacemaker will pace. By pacing at the end of 110 msec, if the event was truly physiologic, the pace will fall into the absolute refractory period of the ventricular muscle tissue. Ventricular Safety Pacing is characterized by short (110 msec) AV intervals. On the marker channel, the VSP will be marked by two downward spikes–one for the ventricular sense and one for the ventricular pace. Ventricular Safety Pacing is designed to minimize the effects of cross-talk, but it can also occur under other circumstances. If a ventricular sensed event (e.g., a PVC or a conducted ventricular event) falls within the first 110 msec after an atrial pace, the pacemaker may Ventricular Safety Pace. Also, if there is an atrial undersensing problem, ventricular safety pacing may be seen. This happens if a scheduled atrial pace is delivered shortly after this unsensed P wave. The scheduled atrial pace initiates a PAV. If the unsensed P wave conducts to the ventricle within the Ventricular Safety Pace window, a Ventricular Safety Pace will occur. Other names for Ventricular Safety Pacing are &quot;non-physiologic AV delay&quot; or &quot;110-msec phenomenon&quot;. When in effect, the AV interval will always be shortened.
- #203 Programmed parameters for this strip are: DDD; lower rate 60; upper rate 120; PAV 150ms; SAV 150 ms. Ventricular Safety Pace (VSP) ON. VSP occurred due to a PVC falling in the AV interval.
- #205 Other methods to manage crosstalk include reducing the atrial output (while maintaining an appropriate stimulation safety margin), decreasing ventricular sensitivity (while maintaining an appropriate sensing safety margin), and programming the polarity to bipolar (if a bipolar lead is implanted).
- #209 The total time that the atrial chamber of the pacemaker is in refractory is during the AV interval and during the PVARP. The Total Atrial Refractory Period (TARP) is equal to the SAV interval plus the PVARP. The TARP is important to understand as it defines the highest rate that the pacemaker will track atrial events before 2:1 block occurs.
- #214 Pacemaker 2:1 block is characterized by two sensed P waves per paced QRS complex. This pattern develops because every other P wave falls into PVARP. Starting on the left side of this ECG, the sequence begins with a sensed P wave. This P wave initiates a SAV, followed by a paced ventricular event. The next P wave falls into the PVARP, started by the ventricular pace, so no SAV is initiated. The following P wave is sensed outside of the PVARP, so a SAV is started. Again, no ventricular event occurs during the SAV, so the pacemaker paces in the ventricle. In this manner, a 2:1 block pattern is created. The rate at which the pacemaker will exhibit a 2:1 block pattern is determined by the SAV and the PVARP (or the TARP). Atrial rates with a P-P coupling interval shorter than the TARP will result in 2:1 block. To determine at what rate the pacemaker will go into 2:1 block, the TARP is simply converted from an interval to a rate. Therefore, the rate the pacemaker will go into 2:1 block is: 60,000/TARP.
- #234 Pacemaker Wenckebach has the characteristic Wenckebach pattern of the PR (AV) interval gradually extending beat-to-beat until an atrial event falls into the PVARP and cannot restart an AV interval. In effect, a ventricular beat is “dropped”. In this graphic, starting from the left side of the ECG, the pacemaker senses an atrial beat and starts an SAV. Because no ventricular event occurs by the end of the SAV, a ventricular pace is delivered. Now the pacemaker is looking for a sensed atrial beat. An atrial beat is sensed outside of the PVARP and starts an SAV. This time, when the SAV times out, the upper rate interval has not yet expired. Since the pacemaker can never violate the upper tracking rate, the ventricular pace has to be delayed until the end of the upper rate interval, at which time a ventricular pace is delivered. This pattern of sensing a P wave, starting an SAV, waiting for the upper rate interval to time out, and pacing in the ventricle repeats until a P wave falls into the PVARP and does not start an SAV. The amount of delay created by the time from the sensed P wave until the upper rate interval expires is a little longer each time, producing the gradually lengthening of the P wave to ventricular pace intervals. Once a P wave falls into the PVARP and does not initiate an SAV, the pacemaker looks for the next sensed P wave and the pattern starts all over again. This is how the classic Wenckebach pattern develops. The rate at which the pacemaker will exhibit Wenckebach behavior is at the upper tracking rate (or upper rate if the pacemaker does not have a separate upper tracking rate and upper activity rate).
- #251 This ECG depicts Wenckebach operation.
- #254 Compare the P-P interval at which the pacemaker will exhibit Wenckebach to the P-P interval at which the pacemaker will go into 2:1 block. Upper tracking interval = 60,000/120 = 500 msec 2:1 block interval = TARP = 200 msec + 350 msec = 550 msec As the P-P interval shortens from the lower rate interval, the 2:1 block interval (550 msec) will be met before the upper tracking interval (500 msec). Therefore, the pacemaker will go into 2:1 block as the atrial rate increases and will never exhibit Wenckebach behavior.
- #256 In this example, the TARP is shorter than the upper tracking rate interval. Therefore, the pacemaker will exhibit Wenckebach operation as the P-P interval exceeds the upper tracking rate interval.
- #259 Going to 2:1 block first without a Wenckebach period may not be the optimal situation because many patients do not tolerate a precipitous drop in ventricular rate well. What can we do to make Wenckebach occur first? Shorten PVARP (Note: Sensor varied PVARP will be addressed later on in the module with mode switching, but it can be discussed as a solution briefly) Shorten SAV Turn on RA-AV
- #260 This upper rate is defined as the upper activity rate, also known as the upper sensor rate or maximum sensor rate. Before mode switching was available, pacemakers utilized a separate activity/sensor rate and upper tracking rate to limit the rate to which the patient could track (e.g., in the presence of SVTs), but allow the patient to pace to higher rates if they were exercising.
- #265 Even patients who have complete antegrade block may have the ability to conduct retrograde. But having the ability to conduct retrograde is not enough. There must be a situation in which the conduction pathways have had a chance to recover when a ventricular contraction occurs. Basically, anything that causes a loss of AV synchrony may promote retrograde conduction and potentially a PMT. All of the above conditions (PVC, atrial non-capture, atrial undersensing, and atrial oversensing) cause a loss of AV synchrony and may promote a PMT.
- #266 This diagram shows the initiation of a PMT by a PVC. A retrograde P wave occurs as a result of the PVC. This retrograde P wave is sensed outside of the PVARP and starts an SAV Interval. When the SAV Interval times out, if the Upper Tracking Rate has not yet expired so the SAV Interval is extended. A ventricular pace is delivered at the end of the upper tracking rate. The AV conduction pathways have recovered and the ventricular pace causes another retrograde P wave. The sequence continues resulting in a sustained Pacemaker Mediated Tachycardia (PMT).