Severe atrioventricular decoupling, uncoupling, and ventriculoatrial coupling during enhanced atrial pacing:...

AV Decoupling During Enhanced AAIR Pacing.

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.

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.

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.

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.