Ventricular Antitachycardia Pacing Feature
Ventricular antitachycardia pacing (ATP) therapy delivers pacing pulses to interrupt a tachyarrhythmia episode and restore normal sinus rhythm. ATP therapy is considered painless and requires less battery energy than cardioversion and defibrillation. ATP may be programmed On in the device prior to the delivery of high-voltage therapies.
This feature can be found in some Medtronic ICD and CRT-D devices. Please go to manuals.medtronic.com or consult with your local Medtronic representative regarding device models available in your geography.
To program this feature, go to Params → VT Therapies → VT Therapy Type
Note: VT and FVT detection zone programming is nominally "OFF". Please see the device manuals for nominal programming.
Ventricular ATP - 2090 CareLink™ Programmer
iATP - CareLink SmartSync™ Device Manager
Smart Mode is programmable for each ATP therapy and is nominally OFF. Smart Mode is only available for Rx1 – Rx4 therapies and will turn an ATP therapy OFF, if all sequences of an ATP therapy fail in 4 consecutive episodes.
Shared Settings for Ventricular ATP Therapy
The programmable parameter V-V Minimum ATP Interval (under Shared Settings; nominal = 200ms) limits the pacing interval at which the ATP pulses are delivered within a sequence. The likelihood of accelerating the arrhythmia is reduced by limiting the ATP pacing interval.
- If the ATP pacing interval is < the programmed V-V Minimum Interval, the pulses are delivered at the programmed V-V Minimum ATP Interval.
- If all intervals of an ATP sequence have been delivered at the V-V Minimum Interval, the device skips the rest of the ATP therapy and delivers the next programmed therapy. If the device detects a FVT episode, it delivers the next programmed CV therapy.
- All ATP therapies are delivered at the same Amplitude and Pulse Width (nominally 8 V @ 1.5 ms) which is programmable.
Shared Settings for Ventricular ATP - 2090 CareLink Programmer
Shared Settings For iATP - CareLink SmartSync Device Manager
Note: iATP is delivered only in RV pacing regardless of Shared Setting programming.
Progressive Episodes Therapies can be programmed On or Off for this feature.
There are three types of Ventricular ATP
Burst: All pacing pulses delivered are of equal cycle length, between sequences, pulses decrement (Interval Dec).
Ramp: Each pacing pulse is decremented by the programmable Interval Dec (ms); an additional pulse is added between sequences.
Ramp +: The first 3 pacing pulses are delivered at a programmable percentage of the detected VT. Subsequent pulses are delivered at the percentage of the 3rd pulse. An additional pulse is added between sequences.
iATP: iATP is a feature which gives customized ATP in real time. An iATP algorithm delivers the equivalent of a train of Burst pulses (S1) followed by 1 (S2) or 2 (S2-S3) extra- stimuli Ramp+ pulses. The protocol for the first iATP sequence is S1-S2. If the first sequence does not terminate the tachyarrhythmia, the protocol for the subsequent sequences is S1-S2 or S1-S2-S3.
Note that the number of S1 paces, and the S2 and/or S3 intervals vary based on iATP’s analysis of how the VT responds to ATP therapy.
When a VT or FVT episode is detected and the first therapy (Rx1) is ATP, the device delivers the first sequence of the ATP therapy. If the device redetects the VT/FVT episode, it delivers the next sequence and repeats this cycle until the episode is terminated or all sequences (max 10) in the therapy are exhausted. If all sequences in an ATP therapy are unsuccessful, the device starts delivering the next ATP or cardioversion therapy (Rx2). If it detects that the current VT episode has accelerated (by at least 60 ms) or redetects the VT as FVT, the device skips the remaining sequences of an ATP therapy and starts the next programmed therapy for the episode.
The ATP pacing interval (R-S1 Interval = % RR, S1S2, etc.) is based on the detected ventricular tachycardia cycle length, which is calculated as the average of the last 4 ventricular intervals prior to VT or FVT detection (or redetection). The smaller the RR%, the more aggressive the ATP therapy is considered.
- VT and FVT therapies – ATP therapies should not be used exclusively to treat VT or FVT episodes. At least one VT therapy and one FVT therapy should be programmed to a maximum energy cardioversion.
- Therapy aggressiveness – VT and FVT therapies must be programmed to be increasingly aggressive. For example, one VT therapy cannot be programmed as a cardioversion and a subsequent VT therapy as a ventricular ATP therapy. Likewise, a VT cardioversion therapy cannot be followed by another VT cardioversion therapy with a lower energy setting.
- Certain ATP therapies may have a higher success rate in restoring sinus rhythm.6
Ventricular ATP Therapy Example: Interval Plot
- Onset of VT; VT detection occurs at Time = 0
- Burst Rx1 Sequence 1 delivered
- VT redetection
- Burst Rx1 Sequence 2 delivered
- VT termination
iATP Therapy Example: Treated VT Episode
iATP performs a series of sequences to terminate the arrythmia using pulses. The number of S1 pulses and the pacing intervals for S2 and S3 are determined automatically. The device does this by analyzing how the ATP is affecting the VT, thus customizing ATP therapy in real-time during a VT episode.
Numerous trials have evaluated the efficacy of ATP for ventricular tachyarrhythmia as a "painless" option for termination. The ADVANCE III2 study, performed with current device nominals 30 of 40 intervals, demonstrated 52% efficacy. Analysis of the four major trials: PainFREE Rx3, PainFREE RxII4, EMPIRIC5 and PREPARE6 trials, showed an increased risk of mortality for patients who received shocks for VT/VF as compared to patients who received ATP therapy. Survival among patients with VT/VF who did not receive shocks was similar to patients with no VT/VF7. Strategies to minimize shocks with ATP therapy and reduce overall ventricular arrhythmia burden may further improve survival in ICD patients.7
In a virtual modeling study, Intrinsic ATP’s termination rate was 17% higher than traditional ATP (burst) with no difference in acceleration rate.8
Figure 1: Mortality Risk Based on Therapy Type6
- Gulizia MM, Piraino L, Scherillo M, et al. A Randomized Study to Compare Ramp Versus Burst Antitachycardia Pacing Therapies to Treat Fast Ventricular Tachyarrhythmias in Patients With Implantable Cardioverter Defibrillators: The PITAGORA ICD Trial. Circ Arrhythmia Electrophysio. 2009;2:146-153.
- Gasparini M, Proclemer A, Klersy C, et al. Effect of Long-Detection Interval vs Standard-Detection Interval for Implantable Cardioverter-Defibrillators on Antitachycardia Pacing and Shock Delivery: The ADVANCE III Randomized Clinical Trial. JAMA. 2013;309(18):1903–1911. doi:10.1001/jama.2013.4598.
- Wathen MS, Sweeney MO, DeGroot PJ, et al, for the PainFREE Investigators. Shock reduction using antitachycardia pacing for spontaneous rapid ventricular tachycardia in patients with coronary artery disease. Circulation. August 14, 2001:104(7): 796-801.
- Wathen MS, DeGroot PJ, Sweeney MO, et al., for the Pain FREE Rx II Investigators. Prospective randomized multicenter trial of empirical antitachycardia pacing versus shocks for spontaneous rapid ventricular tachycardia in patients with implantable cardioverter-defibrillators: Pacing Fast Ventricular Tachycardia Reduces Shock Therapies (PainFREE Rx II) trial results. Circulation. October 26, 2004;110(17):2591-2596.
- Wilkoff BL, Ousdigian KT, Sterns LD, Wang ZJ, Wilson RD, Morgan JM. A comparison of empiric to physician-tailored programming of implantable cardioverter-defibrillators: results from the prospective randomized multicenter EMPIRIC Trial. J Am Coll Cardiol. July 18, 2006;48(2):330-339.
- Wilkoff BL, Williamson BD, Stern RS, et al, for the PREPARE Study Investigators. Strategic programming of detection and therapy parameters in implantable cardioverter-defibrillators reduces shocks in primary prevention patients: results from the PREPARE (Primary Prevention Parameters Evaluation) study. J Am Coll Cardiol. August 12, 2008;52(7):541-550.
- Sweeney, MO, Wathen, MS, Sherfesee L, et al. Differences in Effects of Electrical Therapy for Ventricular Arrhythmias on Mortality in ICD Patients. AHA Abstract 2008. Circulation. 2008; 118S_672.
- Swenson DJ, Taepke RT, Blauer JJ, Kwan E, Ghafoori E, Plank G, Vigmond E, MacLeod RS, DeGroot P, Ranjan R, A Direct Comparison of a Novel Antitachycardia Pacing Algorithm Against Present Methods Using Virtual Patient Modeling, Heart Rhythm (2020), doi: https://doi.org/10.1016/j.hrthm.2020.05.009.
Sources: Medtronic Cobalt and Crome DR/VR MRI SureScan ICD and CRT-D Reference Guide, Medtronic Protecta,™ XT DR Clinician Manual, Medtronic Protecta™ XT CRT-D Clinician Manual.