ATP Before/During Charging Feature
The ATP Before Charging™ and ATP During Charging™ features provide adaptive antitachycardia pacing (ATP) therapy based on the prior success of ATP. If the ATP parameter is set to During Charging, the device delivers a single sequence of ATP therapy when it starts charging for the first defibrillation shock in the VF zone. If the ATP parameter is set to Before Charging, the device delivers a sequence of ATP therapy as soon as an arrhythmia is detected in the VF zone. If the arrhythmia is not terminated by this ATP and the arrhythmia is redetected, the device delivers a second ATP sequence during charging for the defibrillation shock.
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.
This feature is set nominally to ATP During Charging but will adapt to ATP Before Charging with ATP success. The nominal ATP settings are shown in the image below. Other programming options are Before Charging and Off.
To program this feature, go to Params -> VF Therapies -> ATP.
Review the ChargeSaver™/SwitchBack™ features to learn about programming these features.
The graphics below depict the operation of ATP During Charging and ATP Before Charging. For ATP During Charging, once VF detection is reached the device begins to charge to the first programmed shock therapy while at the same time delivering one round of ATP at the programmed settings. If the ATP is not successful, the shock is delivered once the charge ends and the arrhythmia is confirmed.
While ATP During Charging provides a chance for ATP to break the arrhythmia without delaying the shock, ATP Before Charging provides an extra attempt at ATP and also allows more time for the arrhythmia to terminate spontaneously. ATP Before Charging may also conserve the battery for patients in whom ATP is successful.
Once ATP has been delivered during charging, the device will attempt to confirm the continued presence of VF before delivering the shock. The device will review the rhythm and abort the shock therapy if the ventricular intervals are deemed nonarrhythmic according to the confirmation interval.
Review the ChargeSaver™/SwitchBack™ features to learn how the device can automatically adapt between ATP During Charging and Before Charging based on the prior success of ATP for a given patient.
- If the first VF defibrillation shock is not at full energy, there is a potential for the charge time to be too short to allow ATP During Charging to complete the ATP sequence.
- ATP will only be delivered for arrhythmias that fall within the rate range specified by the programmed parameter “Deliver ATP if last 8 R- R Intervals >= (greater than or equal to).” If ATP was not delivered for a FVT because the rate was too fast, consider programming this number down to allow delivery of ATP for faster rates.
- If a FVT via VF zone is programmed in the same rate ranges as ATP During Charging, FVT zone detection takes precedence and FVT therapies will apply. The message below will be displayed in the Observation window on the Quick Look™ II screen.
The example below displays a FVT terminated successfully with ATP During Charging. The EGM shows VF detection and ATP delivered during charging. The ATP successfully terminates the tachyarrhythmia and prevents the delivery of a high voltage shock.
ATP programmed in the VF zone can provide PainFree therapy for fast VTs which has been found to successfully eliminate approximately 75% of shocks.1 In the PainFREE Rx II Trial, the FVT zone was programmed via VF at 240 ms (250 bpm) with one sequence of Burst ATP with eight pulses at 88% of the RR interval average.2 ATP for fast ventricular tachycardia (188-250 bpm) successfully eliminated three out of four shocks, thus improving patient quality of life without adding additional risk from syncope or acceleration as compared with the shock-only group.2
- 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.