Reactive ATP Feature
Reactive ATP™ allows for multiple deliveries of programmed atrial antitachycardia pacing (ATP) therapies during an atrial tachyarrhythmia episode in response to either of the following events:
- change in the atrial rhythm’s cycle length or regularity (Rhythm Change)
- the expiration of a programmed time interval (Time Interval)
This feature can be found in some Medtronic Pacemaker, ICD, CRT-P, and CRT-D devices. Please go to manuals.medtronic.com or consult with your local Medtronic representative regarding device models available in your geography.
AT/AF detection is nominally set to Monitor.
- To program this feature ON, go to Params › Detection AT/AF
- Select the field for AT/AF, All RX Off, to open the AT/AF Detection and Therapies window
- Set AT/AF Detection to ON
- Set Atrial Interval detection Zone(s) and Rate(s)
- Set desired atrial ATP therapies
- Choose desired values for Episode Duration Before Rx Delivery (ATP)
- Choose desired values for Reactive ATP (Rhythm Change & Time Interval)
- Choose whether atrial therapies should be disabled if rate acceleration occurs or if lead position is suspect
- Choose a desired value for Duration to Stop
- Return to the Parameters screen and select PROGRAM
Note: High Power devices may have additional programming options and fields.
If Rhythm Change is enabled, the device detects changes in the atrial arrhythmia using both regularity and cycle length. The AT/AF zone is subdivided into a series of narrower regions. Each region is supplied with a separate set of the atrial ATP therapies enabled for AT/AF episodes. One series of subdivided regions is identified for regular atrial rhythms. Another series of regions is identified for irregular atrial rhythms. If the rhythm shifts into a different region because of a change in cycle length or regularity, the device delivers therapies from those available in the new region.
Single zone programming is shown in the diagram below. The AT/AF detection zone is divided into smaller zones or bins, each having a full set of ATP therapies. With Rhythm Change ON, if the rhythm shifts into a different region (bin) because of a change in cycle length or regularity, the device delivers therapies available in the new region. The number of bins depends on the size of the AT/AF zone.
Two zone programming is shown in the diagram below. When there are 2 atrial detection zones, the number of regions in the AT/AF zone depends on the programmed values for the AT/AF detection interval and the Fast AT/AF detection interval. The Fast AT/AF zone is not subdivided, and Fast AT/AF ATP therapies are not affected by this type of Reactive ATP.
The Time Interval feature of Reactive ATP allows for treatment of atrial arrhythmias that may have changed throughout the course of an atrial episode. If a Reactive ATP Time Interval is programmed, the number of ATP sequences is reset for both the AT/AF zone and the Fast AT/AF zone. The reset occurs when the Sustained Duration value (time from initial detection) reaches a multiple of the programmed Time Interval. This reset function is available only within the first 48 hours of an atrial episode.
Disabling Atrial Therapies
Stop Atrial Rx After Rx/Lead Suspect - there are 2 programming options:
- Disable Atrial ATP if it accelerates V. rate – If enabled, the device responds when a single ATP therapy causes the ventricular rate to accelerate. The device disables all atrial therapies until they are re-enabled using the programmer. The criteria for rate acceleration are that ventricular intervals are shorter than 320 ms, that they decrease by 70 ms, and that the ventricular rate acceleration occurs during the atrial ATP.
- Disable all atrial therapies if atrial lead position is suspect – The device checks the atrial lead position every 24 hours. The Atrial Lead Position Check occurs only if the pacing mode includes atrial pacing. The check is disabled during mode switching, telemetry sessions, atrial episodes, and ventricular episodes. It determines the number of AP-VS intervals in the series that are shorter than 80 ms. A large number of short intervals indicate that the lead may no longer be positioned in the atrium. If this lead check fails, all atrial therapies are disabled until they are re-enabled using the programmer.
Duration to Stop:
To limit therapy delivery for a prolonged atrial episode, you can program the Duration to Stop parameter. If an atrial episode exceeds the programmed value, this feature suspends all atrial therapies for the duration of the atrial episode. Atrial therapies are re-enabled upon atrial episode termination.
Review of Atrial ATP Therapy
Ramp therapy sequences consist of a programmable number of AOO pulses delivered at decreasing intervals. VVI ventricular backup pacing is available during Ramp pacing. The first pulse of each Ramp sequence is delivered at a programmable percentage of the current atrial cycle length (the median of the last 12 P-P intervals). The rest of each sequence is delivered at progressively shorter intervals, based on the programmed Interval Decrement. If the tachycardia is redetected after an ineffective sequence, the device delivers another Ramp sequence. For this sequence, the device calculates the intervals based on the atrial cycle length at redetection. Each sequence contains one more pacing pulse than the previous sequence contained.
Burst+ therapy sequences consist of a programmed number of AOO pulses followed by 2 premature stimuli that are delivered at shorter intervals. VVI ventricular backup pacing is available during Burst+ pacing. The AOO sequence is delivered at the programmed A-S1 Interval timed from the first sensed A-event following the V-event that fulfills detection. The first premature stimulus is delivered at the S1-S2 percentage. The second premature stimulus is delivered at the S1-S2 interval minus the programmed S2-S3 Decrement. If the tachycardia is redetected after an ineffective sequence, the device delivers another Burst+ sequence with shorter pacing intervals. For this sequence, the device calculates these intervals by subtracting the programmed Interval Decrement from the Burst+ parameters.
- Detection is suspended during an atrial ATP therapy sequence.
- S2-S3 pulses are not delivered if S1-S2 pulses are programmed Off.
Atrial 50 Hz Burst
50 Hz Burst therapy is available and programmable in certain ICD and CRT-D devices. The device delivers a 50 Hz Burst therapy sequence with a burst of pulses at 20 ms pacing intervals for the programmed 50 Hz Burst Duration. Each time the atrial tachyarrhythmia is redetected, the device delivers another identical 50 Hz Burst sequence until delivering the last programmed sequence. Atrial therapy scheduling is delayed for 16 ventricular events after each 50 Hz Burst therapy sequence. Please refer to the appropriate product manuals for more information.
Atrial ATP Pacing Therapy Programming
Using the programming shown above, Rx1 Ramp therapy would be delivered as follows:
- Initial #S1 Pulses – Number of pulses in the first Ramp sequence.
- A-S1 Interval (%AA) – Pacing interval of the first Ramp pulse as a percentage of the pretherapy atrial cycle length.
- Interval Decrement – Pacing interval decrement per pulse for the remaining Ramp pulses in each sequence.
- # Sequences – Number of sequences in the Ramp therapy.
Using the programming shown above, Rx2 Burst+ therapy would be delivered as follows:
- Initial #S1 Pulses – Number of S1 pulses in each burst sequence.
- A-S1 Interval (%AA) – Pacing interval of the S1 burst pulses, as a percentage of the pretherapy atrial cycle length.
- S1-S2 (%AA) – Pacing interval of the S2 stimulus following the burst as a percentage of the pretherapy atrial cycle length.
- S2-S3 Decrement – The S2-S3 interval equals the S1-S2 interval minus this decrement value.
- Interval Decrement – Pacing interval decrement per sequence.
- #Sequence – Number of sequences in the Burst+ therapy.
- Lead fixation – Do not program an atrial ATP therapy On until the atrial lead has matured (approximately 1 month post-implant).
- Certain ATP episodes may have higher success rates for restoring sinus rhythm.1
- Atrial ATP amplitude and pulse width can be adjusted.
- VVI backup pacing is available during atrial ATP.
- Note: If all atrial therapies are programmed Off and the AT/AF Detection parameter is changed from Monitor to On, the programmer automatically sets the first 2 AT/AF therapies to nominal or previously programmed settings.
In the episode below, the device was programmed as follows:
- Single AT/AF zone detection = 350 ms
- Rx1=8 sequence Ramp, and Rx2=6 sequence Burst+, for a total of 14 sequences.
- Reactive ATP was programmed with Rhythm Change ON and Time Interval OFF.
The Episode Text displays the number of atrial ATP sequences delivered in each bin. The asterisk is displayed in the bin where the Last Rx was delivered. The rhythm changed in cycle length and regularity over the 11 hour episode duration. Therapy was exhausted for the 150-199 ms bin, as well as for rhythms classified as irregular, as illustrated in the episode text by the number 14. This indicates that all 14 therapies were applied in the respective bins. Therapy 1; sequence 4 was successful when the rhythm slowed to 250 ms and became regular.
Evaluation of Reactive ATP
The device reports accumulated data on detected and treated AT/AF episodes, bradycardia interventions, and the efficacy of therapy in the Cardiac Compass™ trends report. This information may help you optimize Reactive ATP programming for your patient.
The MINERVA (MINimizE Right Ventricular pacing to prevent Atrial fibrillation and heart failure) study2 demonstrated that patients programmed DDDRP+MVP™ had a significant 61% relative risk reduction in the progression of AF over a two year follow-up compared to standard dual chamber pacing. DDDRP+MVP™ includes atrial ATP with Reactive ATP, along with pacing overdrive features; Atrial Preference Pacing, Atrial Rate Stabilization and Post Mode Switch Overdrive Pacing, all programmed “ON” as well as MVP.
These graphs represent how many patients in each arm had at least one episode of AT/AF lasting longer than 1 day and 7 days, respectively. Note that there is a statistically significant reduction in the DDDRP+MVP™ arm compared to the Control DDDR arm.
- Gillis et al. Heart Rhythm 2005;2:791–796 ATP Efficacy predictors.
- Boriani G, et al. Atrial Antitachycardia Pacing and Managed Ventricular Pacing Reduce the End Point Composed by Death, Cardiovascular Hospitalizations, and Permanent Atrial Fibrillation compared to Conventional Dual Chamber Pacing in Bradycardia Patients: Results of the MINERVA Randomized study. AHA Late Breaking Clinical Trial, November 18, 2013.
Sources: Medtronic Consulta™ CRT-P Clinician Manual; Medtronic Protecta™ XT DR Clinician Manual; Medtronic Protecta™ XT CRT-D Clinician Manual;Medtronic Enrhythm™ Reference Manual; Advisa DR MRI™ SureScan™Clinician Manual