Dual-Chamber Timing Göran Mathson, 2005

NASPE/BPEG Generic Pacemaker Code What is stimulated? I 0=None A=Atrium V=Ventricle D=Dual (A+V) S=Single (A or V) What is sensed? II 0=None A=Atrium V=Ventricle D=Dual (A+V) S=Single (A or V) Reaction to sensing III 0=None T=Triggered I=Inhibited D=Dual (T+I) Rate Modulation IV 0=None R=Rate Modulation Multisite Pacing V 0=None A=Atrium V=Ventricle D=Dual (A+V) The Revised NASPE/BPEG Generic Code for Antibradycardia, Adaptive-Rate, and Multisite Pacing, PACE , Volume 25, No. 2, February 2002

Pacing systems AAI(R) VVI(R) DDD(R) VDD(R) = Sensing point = Stimulation point = Sensing and Stimulation point

A-A This presentation is on atrial-based DDD timing. This is the timing system we have had since Affinity. Main timer is the A-A timer, generally corresponding to the basic rate. The timer starts with an atrial event whether paced or sensed. And if it times out, you will see an atrial stimulus on the ECG.

A-A AV Delay In parallell to the A-A timer, AV delay runs. Starting with an paced atrial event. And if it times out, you will see an ventricular stimulus on the ECG.

A-A PV Delay PV delay is like the AV delay but the starting point is the sensing of a P-wave.

AV and PV Delay... To make haemodynamics equivalent whether the atrium is paced or sensed, the AV and PV delays are separately programmable. Per definition an AV delay starts the atrial depolarisation and the PV delay detects an already ongoing depolarisation. Hence, to get the same haemodynamics, PV delay is usually programmed slightly shorter than the AV delay. 170 ms 150 ms

AV and PV interval... Late atrial activation In some cases, the atrial lead sits in a slow conducting part of the atrium, resulting in late atrial activation. To some extent, you can limit the haemodynamic consequences by programming AV and PV delays differently. 250 ms 150 ms The AV Delay can be programmed max. 100 ms longer than the PV Delay

Late Atrial Activation In this case: AV Delay should be 80 ms longer than PV Delay

A-A AV Delay Both the AV and PV delay can be terminated by sensing of a ventricular event.

A-A terminated by intrinsic P-wave AV Delay The A-A timer can be terminated by sensing of an atrial event, restarting a new A-A timer and a PV delay. A-A terminated by intrinsic P-wave

A-A – AV delay timer starts on detection of a PVC A-A terminated by a PVC A-A – AV delay timer starts on detection of a PVC The A-A timer can also be terminated by a ventricular event. Per definition this would now be a PVC. This ventricular event restarts a modified A to A timer. It is reduced by the AV delay to avoid an extra long pause until the next ventricular paced event.

Post Ventricular Atrial Refractory Period A-A AV Delay PVARP Post Ventricular Atrial Refractory Period Programmable refractory period on the atrial channel is called PVARP. It starts with a ventricular event paced or sensed.

AV/PV Delay + PVARP = Total Atrial Refractory Period, TARP A-A AV Delay PVARP In fact, the atrial channel is refractory also during the AV/PV delay. TARP is not directly programmable, but will play a significant role in upper rate behaviour. AV/PV Delay + PVARP = Total Atrial Refractory Period, TARP

Example of programmability... 25, 30, 40, 50…170…350 150 200 250 300 350 400 450 500 175 225 275 325 375 425 475

Noise Mode, Atrial Channel PVARP The main refractory periods, in this case PVARP, consists of two parts, one absolute refractory and one relative refractory part. Noise mode appears when signals of a very high rate are picked up in the relative refractory period. The refractory period will be prolonged as long as these high rate signals keep coming in. The effect of this is basic rate pacing. A-A Interval Absolute Relative Programmable PVARP

Noise sampling window (NSW) Sensed Event NSW 150 ms Example Identity ADx: 100 ms 175 ms Relative Absolute Sensed Event NSW 150 ms Sensed Event NSW 150 ms Sensed Event Sensed Event

Noise Mode, Atrial Channel A-A Interval

Ventricular Refractory Period A-A AV Delay PVARP VRP The ventricular refractory period starts with a ventricular event, paced or sensed. Ventricular Refractory Period

Ventricular Blanking Period A-A AV Delay PVARP VRP Ventricular blanking period appears on the ventricular channel after atrial stimulation only. Reason for this is to avoid cross talk, see next slide. Ventricular Blanking Period

Far-field sensing Crosstalk Intrinsic activity is sensed in the = Sensing point = Stimulation point = Sensing and Stimulation point Far-field sensing Intrinsic activity is sensed in the “wrong” chamber Crosstalk Pacemaker activity is sensed in the “wrong” chamber Note that cross talk can only appear on the ventricular channel. The atrial channel would be in PVARP when the ventricular stimulation appears.

Example of programmability... 12…51ms 125 175 225 275 325 375 425 475 150 200 250 300 350 400 450

Maximum Tracking Rate Interval A-A AV Delay PVARP VRP Maximum tracking rate interval corresponds to the programmed maximum tracking rate. It starts with a ventricular event, paced or sensed. MTRI Maximum Tracking Rate Interval

A-A AV Delay PVARP VRP MTRI Maximum Tracking Rate Interval

Pseudo Wenckebach Upper Rate Behaviour MTR Interval MTR Interval MTR Interval MTR Interval

A-A AV Delay PVARP VRP MTRI MSRI Maximum sensor rate interval corresponds to the programmed maximum sensor rate. (Since this is an atrial based timing, it starts with the atrial event paced or sensed.) MTRI MSRI

V = Ventricular paced event R = Ventricular sensed event Markers… A = Atrial paced event P = Atrial sensed event V = Ventricular paced event R = Ventricular sensed event

DDD(R) Pacing States AV-Pacing AR-Pacing PV-Pacing PR-Pacing

DDD(R) Pacing States AV-Pacing AV pacing appears at basic rate or in a rate modulated system at sensor driven rate. In today’s devices, there are many more possibilities as well, for instance, AF suppression or rest rate.

DDD(R) Pacing States PV-Pacing P-wave tracking. This would be the typical pacing state of an AV block patient.

DDD(R) Pacing States PR-Pacing

DDD(R) Pacing States AR-Pacing Atrial stimulation with intrinsic conduction. This would be the typical pacing state of an Sinus Node Disease patient.

Pacing States A V A R P V P R It might facilitate interpretation to make the annotations on a Xerox copy…

Markers P R A V P R Atrial Refractory period 142 546 694 170 617 759 Atrial Refractory period P R Ventricular Refractory period

DDI Timing DDI(R) is active during mode switch… 2

NASPE/BPEG Generic Pacemaker Code What is stimulated? I 0=None A=Atrium V=Ventricle D=Dual (A+V) S=Single (A or V) What is sensed? II 0=None A=Atrium V=Ventricle D=Dual (A+V) S=Single (A or V) Reaction to sensing III 0=None T=Triggered I=Inhibited D=Dual (T+I) Rate Modulation IV 0=None R=Rate Modulation Multisite Pacing V 0=None A=Atrium V=Ventricle D=Dual (A+V) The Revised NASPE/BPEG Generic Code for Antibradycardia, Adaptive-Rate, and Multisite Pacing, PACE , Volume 25, No. 2, February 2002

AVI AEI VEI PVARP VRP MSRI DDI could be programmed or appear as the mode during mode switch. DDI has ventricular based timing. At the ventricular event, both an atrial escape interval and a ventricular escape interval starts. VRP MSRI

AVI AEI VEI PVARP VRP MSRI If a high atrial rate is detected, the ventricular rate will not be affected. VRP MSRI

P V AVI AEI VEI PVARP VRP MSRI

AVI AEI VEI PVARP VRP MSRI

Lower Rate 2

Rest Rate, and it’s Sensor Driven! Basic Rate Rest Rate is sensor driven – patients can rest when they feel like it. It is technically based on statistics long term (Activity Variance Histogram) compared to short time. Rest Rate

Rate Hysteresis Classic single-chamber version Basic Rate Hysteresis Rate Classical single-chamber rate hysteresis. Today almost exclusively used in VVI(R) in conjunction with Autocapture. This is to avoid a series of (pseudo)fusion beats.

Advanced Hysteresis Response Intervention Duration Sensor Recovery Rate Search Interval Intervention- rate Basic rate Hysteresis rate Advanced hysteresis response is mainly used together with DDI mode in patients with vasovagal syncope. Cycle Count Cycle Count

Crosstalk… A V P V A R Crosstalk events marked by the arrows.

Decrease atrial output? Decrease ventricular sensitivity? Crosstalk Decrease atrial output? Decrease ventricular sensitivity? Prolong ventricular blanking? Enable Ventricular Safety Standby! The classical recommendations to avoid crosstalk. They are not easy to follow, except for the use of Ventricular Safety Standby.

Ventricular Safety Standby Blanking Period Crosstalk Detection Window

Ventricular Safety Standby Crosstalk V. Safety Pacing after 120 ms

Is Ventricular Safety Pacing Present In This Panel? Yes, in the last event! But it is due to a late cycle PVC (no crosstalk).

Vetricular Safety Pacing Other tracing – same story.

Ventricular Safety Standby Sensing in Crosstalk Detection Window V. Safety Pacing after 120 ms

Ventricular Safety Standby Blanking Period Undersensing V. Pacing after programmed AV Interval We can enjoy the shortest Ventr. Blanking in the industry. This is important – look at the next slide!

Blanking period undersensing can be dangerous at long AV intervals Blanking period under-sensing can be dangerous if AV delay is programmed long. Note that this will happen with AutoCapture as well when the backup pulse will come approximately 100 milliseconds after the initial stimulus. AICS can also produce a dangerous situation. This can be the case in competitors devices as well, of course. Again, we have the shortest ventr. Blanking! Conclusion, it is preferable to have a very short blanking period if possible. Blanking period undersensing can be dangerous at long AV intervals

AutoIntrinsic Conduction Search Neg. AV/PV Hysteresis AF Suppression Special Features AutoIntrinsic Conduction Search Neg. AV/PV Hysteresis AF Suppression

AutoIntrinsic Conduction Search Programming Suggestions

AutoIntrinsic Conduction Search in Intermittent High Degree AV-Block P V 150 788 938 Programme the optimal AV/PV Delay for time in high degree AV-block 1 Add an AutoIntrinsic Conduction Search of e.g. 100 - 120 ms to allow for intrinsic conduction within a hemodynamically acceptable conduction time 2 Philosophy: High degree AV block will need relatively high percentage ventricular stimulation. Hemodynamically optimized AV delay is important. 150 Progr. PV Interval 100 AICS

AutoIntrinsic Conduction Search in Intermittent High Degree AV-Block P 232 R The pacemaker will now allow for intrinsic conduction within the prolonged AV/PV Delay, in this case 250 ms. 634 812 150 Progr. PV Interval 100 AICS

AutoIntrinsic Conduction Search in Intermittent High Degree AV-Block 150+100 ms 150+100 ms 150+100 ms 150 ms 150 ms Programmed AV/PV Delay AutoIntrinsic Conduction Search

AutoIntrinsic Conduction Search in Intermittent High Degree AV-Block 150 ms Search 150+100 ms 150+100 ms 150+100 ms 150 ms Programmed AV/PV Delay AutoIntrinsic Conduction Search

AutoIntrinsic Conduction Search in Sinus Node Disease P R 171 767 938 Let the pacemaker measure the PR- and AR-Interval at rest 1 Program PV- and AV Delay slightly longer than intrinsic conduction 2 Add an AutoIntrinsic Conduction Search of 120 ms 3 Philosophy: SND will need low percentage, if any, ventricular stimulation. Avoiding un-necessary ventricular stimulation is in focus. 200 Programmed PV Interval 120 AICS

AutoIntrinsic Conduction Search in Sinus Node Disease P 268 R The pacemaker will now allow for intrinsic conduction within the prolonged AV/PV Delay, in this case 320 ms. 670 841 200 Programmed PV Interval 120 AICS

AutoIntrinsic Conduction Search in Sinus Node Disease Preference of intrinsic conduction... 200 + 120 ms 200 + 120 ms 200 + 120 ms 200 + 120 ms 225 + 120 ms Programmed AV/PV Delay AutoIntrinsic Conduction Search

AutoIntrinsic Conduction Search in Sinus Node Disease Back-up pacing if, against all odds, intrinsic conduction is lost... 200 + 120 ms 200 ms 200 ms 200 ms 200 ms Programmed AV/PV Delay AutoIntrinsic Conduction Search

Neg. AV/PV Hysteresis Programming in HOCM

HOCM Hypertrophic Obstructive CardioMyopathy

Negative AV/PV-hysteresis Measure, with the puls generator, the PR interval Program, with the aid of Echo, the optimal PV- Delay. (Longest PV Delay with full capture) To make this dynamic, program how much faster pacing should be, compared to a sensed R-wave (PRMeas – PVOpt). This is called Neg. AV/PV Delta.

Negative AV/PV-Hysteresis (search) 81 ms 74 ms 74 ms 124 ms 124 - 124 - 50 ms 50 ms Measured PR-interval Neg. AV/PV-Delta (Programmable, -10 to -110 ms) Resulting PV-interval

AF Suppression

AF Suppression, AFx > 90% Atrial Pacing AFx ensures a high percentage of atrial stimulation at a rate following the patients natural circadian variations, thereby maintaining control of the atrium, reducing ectopy, and suppressing atrial tachyarrhythmias

AF Suppression, AFx MSR AFx Intrinsic Rate Basic Rate Searches will happen approximately 2-3 times a minute. Basic Rate

AF Suppression, AFx AFx Overdrive: 10 min-1 at rate 60 min-1 and 5 min-1 at rate 150 min-1.

AF Suppression, AFx Search for intrinsic activity 67 66 65 Activity found (two P-waves) 64 65 Increase stimulation rate 74 To apply overdrive, two P-waves has to be sensed, the second within 16 cycles from the first.

AF Suppression, AFx ! … and to programme: ON / OFF