Severe atrioventricular decoupling, uncoupling, and ventriculoatrial coupling during enhanced atrial pacing: incidence, mechanisms, and implications for minimizing right ventricular pacing in ICD patients.
AV Decoupling During Enhanced AAIR Pacing.


BACKGROUND
Enhanced AAI/R pacing minimizes right ventricular pacing but may permit or induce AV decoupling (AV-DC) due to unrestricted AV intervals (AVIs). The purpose of this study was to characterize and quantify AVI behavior in a randomized trial of enhanced AAI/R pacing in ICD patients.


METHODS
One hundred twenty-one patients in the Marquis ICD MVPtrade mark Study, a randomized 1-month crossover comparison of cumulative% ventricular pacing (Cum%VP) in enhanced AAIR (MVP) vs DDD/R, were analyzed. AV-DC was defined as >or=40% AVIs >300 ms; VA coupling (VA-C) was defined as%V-atrial pace (AP) intervals <300 ms. Dynamic AVI behavior and increases in Cum%VP due to AV block (AV uncoupling, AV-UC) were characterized using Holters with real-time ICD telemetry.


RESULTS
AV-DC occurred in 17 (14%) of patients. Baseline PR, amiodarone, nighttime, lower rate >60 beats/min, rate response, and Cum%AP were associated with longer AVIs. Logistic regression identified baseline PR (odds ratio [OR]= 1.024, 95% confidence interval [CI] 1.007-1.042; P = 0.005), and Cum%AP (OR = 1.089, 95% CI 1.027-1.154; P = 0.004) as predictors of AV-DC. AV-DC was associated with approximately 10-fold increases in both Cum%VP (13.6 +/- 28.3% vs 1.2 +/- 3.9%; P = 0.023) due to transient AV-UC) and VA-C (6.0 +/- 17.5% vs 0.5 +/- 1.2%, P = 0.028). AV coupling (<40% AVIs >300 ms) was preserved in 104 (86%) patients.


CONCLUSIONS
AV-DC, VA-C, and AV-UC may be worsened or induced by enhanced AAI/R pacing. Conservative programming of lower rate and rate response should reduce the risk of AV-DC by reducing Cum%AP.
Sweeney
Michael O
MO
Brigham and Women's Hospital, Boston, Massachusetts 02115, USA. mosweeney@partners.org
Ellenbogen
Kenneth A
KA
Tang
Anthony S L
AS
Johnson
James
J
Belk
Paul
P
Sheldon
Todd
T
D000368:Aged; D000465:Algorithms; D001145:Arrhythmias, Cardiac / Q000453:epidemiology* / Q000517:prevention & control*; D002304:Cardiac Pacing, Artificial / Q000379:methods / Q000706:statistics & numerical data*; D018592:Cross-Over Studies; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D016037:Single-Blind Method; D013813:Therapy, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000453:epidemiology* / Q000517:prevention & control*