Minimizing Right Ventricular Pacing with a New Pacing Algorithm for Implantable Pacemakers and Defibrillators: ADI Mode

  • Thu, 5/1/08 - 3:22pm
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All four test criteria for AV block were met. Intracardiac EGMs and marker channels were automatically stored. The switch to DDD on January 4 was for 2nd degree AVB. Two of the three dropped beats and the characteristic Wenckebach rhythm are both shown in
This strip shows SORIN’s stored intracardiac EGM and marker channel annotation for a failed attempt to verify intact conduction. The test criterion for complete heart block was met after two non-conducted P waves.
Medtronic Test for AV Block. This strip shows a real time surface ECG and marker channel. The first dropped P wave is followed by a V pace synchronized to the next P wave. The following P wave is also dropped, meeting the Medtronic test criterion for 3:2
Medtronic Test for Resumed Conduction. This strip shows a real time surface ECG and marker channel. When the Medtronic device switched to AAI to test for intact conduction, the first P wave was blocked. The test criterion for intact conduction failed afte
Author(s): 

Kenneth A. Ellenbogen, MD, Kontos Professor of Medicine

In the DDD pacing mode, the ventricular sensing channel waits for a conducted beat until the programmed AV interval (AV delay) times out. This typically results in a high percentage of ventricular pacing. Programming longer AV delays can increase the frequency of intrinsic conduction. However, long AV delays may introduce complications such as non-physiologic PR intervals, pacemaker-mediated tachycardia, and artificially limited maximum tracking rates. Attempts to manage AV delays to promote conduction are even more complex for ICDs.

ADI Mode: Product Development

In 2003, ELA Medical, now SORIN GROUP CRM, introduced in Europe a dual chamber pacemaker where the ventricular lead tests for AV block instead of AV conduction. When the patient's intrinsic AV conduction is normal, the pacemaker paces in the AAI mode. If the test criteria for AV block are met, the pacemaker switches to DDD pacing to preserve cardiac output. Switching to DDD mode at the onset of AV block allows physicians to select appropriate AV delay settings optimized for maximum cardiac output. SORIN named its version of ADI mode pacing AAIsafeR. In 2004, Medtronic introduced in Europe its version of an ADI algorithm for both implantable defibrillators and pacemakers. Medtronic's ADI mode is called Managed Ventricular Pacing (MVP). In 2005, SORIN GROUP CRM released a second generation ADI algorithm, AAIsafeR2, incorporating new therapeutic and diagnostic features to better manage pacemaker patients. This feature is offered in the Symphony DR pacemaker and was unlocked and made available retroactively upon FDA approval in May 2005. A third generation of SORIN's ADI algorithm is included in the Ovatio DR implantable defibrillator, which is currently awaiting FDA approval in the U.S.

ADI Mode: Operation of SORIN and Medtronic Algorithms

SORIN GROUP CRM's algorithm uses five different criteria to test for either blocked P waves (consecutive P waves without an intervening ventricular contraction) or long PR intervals:
1. 3rd degree AV Block: Two consecutive blocked P waves.
2. 2nd degree AV Block: Three blocked P waves within 12 atrial cycles.
3. 1st degree AV Block: Seven consecutive atrial cycles, where the PR interval exceeds a programmed value.
4. Ventricular Pause: In order to prevent inappropriate cycling to DDD mode during atrial arrhythmias, the pacemaker switches to DDD mode only if a ventricular pause occurs, (programmable up to 4 seconds).
5. Ventricular safety pacing: SORIN's new Ovatio DR defibrillator will employ a fifth test based on ventricular safety pacing criteria.

References: 

1. DAVID Trial Investigators. Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial. JAMA 2002;288:3115–3123.2. Sweeney MO, Hellkamp AS, Ellenbogen KA, et al., for the MOde Selection Trial (MOST) Investigators. Adverse effect of ventricular pacing on heart failure and atrial fibrillation among patients with normal baseline QRS duration in a clinical trial of pacemaker therapy for sinus node dysfunction. Circulation 2003;107:2932–2937.3. Freudenberger RS, Wilson AC, Lawrence-Nelson J, et al., for the Myocardial Infarction Data Acquisition System Study Group (MIDAS 9). Permanent pacing is a risk factor for the development of heart failure. Am J Cardiol 2005;95:671–674.4. Goldberger JJ. Right ventricular pacing: Has DAVID slain this Goliath? Heart Rhythm 2005;2:835–836.5. Medtronic EnRhythm Reference Manual, Part No. UCX220739001.6. Gillis AM, et al. Reduction of unnecessary right ventricular pacing due to the Managed Ventricular Pacing (MVP) Mode in patients with symptomatic bradycardia: Benefit for both sinus node disease and AV block. Heart Rhythm 2005;2, May Supplement:AB21-1.7. Anselme F, et al. First clinical results of AAIsafeR2, a new mode to prevent ventricular pacing. Heart Rhythm 2005;2, May Supplement:P4-99.8. Defaye P, Anselme F, Gras D, et al. AAIsafeR2: Suppression of deleterious unnecessary ventricular pacing. Europace 2005, P202. 9. Op cit, DAVID Trial.

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