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. 2023 Feb 16;25(2):536-545.
doi: 10.1093/europace/euac224.

Electrocardiographic imaging demonstrates electrical synchrony improvement by dynamic atrioventricular delays in patients with left bundle branch block and preserved atrioventricular conduction

Peter H Waddingham  1   2 , Jan O Mangual  3 , Michele Orini  4 , Nima Badie  3 , Amal Muthumala  1 , Simon Sporton  1 , Luke C McSpadden  3 , Pier D Lambiase  1   4 , Anthony W C Chow  1   2
Affiliations

Electrocardiographic imaging demonstrates electrical synchrony improvement by dynamic atrioventricular delays in patients with left bundle branch block and preserved atrioventricular conduction

Peter H Waddingham et al. Europace. .

Abstract

Aims: Cardiac resynchronization therapy programmed to dynamically fuse pacing with intrinsic conduction using atrioventricular (AV) timing algorithms (e.g. SyncAV) has shown promise; however, mechanistic data are lacking. This study assessed the impact of SyncAV on electrical dyssynchrony across various pacing modalities using non-invasive epicardial electrocardiographic imaging (ECGi).

Methods and results: Twenty-five patients with left bundle-branch block (median QRS duration (QRSd) 162.7 ms) and intact AV conduction (PR interval 174.0 ms) were prospectively enrolled. ECGi was performed acutely during biventricular pacing with fixed nominal AV delays (BiV) and using SyncAV (optimized for the narrowest QRSd) during: BiV + SyncAV, LV-only single-site (LVSS + SyncAV), MultiPoint pacing (MPP + SyncAV), and LV-only MPP (LVMPP + SyncAV). Dyssynchrony was quantified via ECGi (LV activation time, LVAT; RV activation time, RVAT; LV electrical dispersion index, LVEDi; ventricular electrical uncoupling index, VEU; and biventricular total activation time, VVtat). Intrinsic conduction LVAT (124 ms) was significantly reduced by BiV pacing (109 ms) (P = 0.001) and further reduced by LVSS + SyncAV (103 ms), BiV + SyncAV (103 ms), LVMPP + SyncAV (95 ms), and MPP + SyncAV (90 ms). Intrinsic RVAT (93 ms), VVtat (130 ms), LVEDi (36 ms), VEU (50 ms), and QRSd (163 ms) were reduced by SyncAV across all pacing modes. More patients exhibited minimal LVAT, VVtat, LVEDi, and QRSd with MPP + SyncAV than any other modality.

Conclusion: Dynamic AV delay programming targeting fusion with intrinsic conduction significantly reduced dyssynchrony, as quantified by ECGi and QRSd for all evaluated pacing modes. MPP + SyncAV achieved the greatest synchrony overall but not for all patients, highlighting the value of pacing mode individualization during fusion optimization.

Keywords: Atrioventricular delay; CRT optimization; Electrocardiographic imaging; Fusion pacing; MultiPoint pacing; SyncAV.

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Conflict of interest statement

Conflict of interest: N.B., L.C.M., and J.O.M. are employees of Abbott.

Figures

Graphical Abstract
Graphical Abstract
Dynamic atrioventricular delays targeting fusion with intrinsic conduction reduce electrical dyssynchrony.
Figure 1
Figure 1
Distribution of latest segment of left ventricular (LV) activation during intrinsic conduction. Values represent % of patients with latest activation in each segment.
Figure 2
Figure 2
Electrocardiographic imaging (ECGi) epicardial maps of activation time in a representative case for each modality of interest. From left to right, images correspond to right anterior oblique (RAO), left anterior oblique (LAO), and left lateral (LL) views. Grey geometries correspond to left anterior descending artery (LAD), right ventricular lead tip (RV tip), and left ventricular lead (LV lead); LVAT, left ventricular activation time.
Figure 3
Figure 3
Electrocardiographic (ECG) QRS duration and ECG imaging (ECGi) activation times for intrinsic conduction and each pacing mode. (A) QRS duration, (B) LVAT, (C) RVAT, and (D) VVtat panels show box plots of absolute values and bar graphs of proportion of patients in which each mode delivered the minimum value. Standard box plots show median (horizontal line), interquartile range (box), non-outlier range (dashed whiskers), and individual outlier values beyond 1.5 × (interquartile range) from each of the two quartiles (‘+’ symbol). BiV, biventricular pacing with nominal fixed atrioventricular delays; LVSS, left ventricular single site pacing, LVMPP, left ventricular MultiPoint Pacing (dual site), MPP, biventricular MultiPoint Pacing; QRSd, QRS duration; LVAT, left ventricular activation time; RVAT, right ventricular activation time; VVtat, total ventricular activation time. Statistical significance (P < 0.05/15 using Bonferroni correction) indicated relative to intrinsic conduction (*), BiV (†), LVSS + SyncAV (◊), BiV + SyncAV (#), and LVMPP + SyncAV (x).
Figure 4
Figure 4
Electrocardiographic imaging (ECGi) metrics of dyssynchrony for intrinsic conduction and each pacing mode. (A) LVEDi and (B) VEU panels show box plots of absolute values and bar graphs of proportion of patients in which each mode delivered the minimum value. LVEDi, left ventricular dispersion index; VEU, ventricular electrical uncoupling index; all other plot characteristics, abbreviations, and symbols follow Figure 3.
Figure 5
Figure 5
Correlation between QRS duration (QRSd) and each electrocardiographic imaging (ECGi) dyssynchrony metric across all pacing modes: (A) LVAT, (B) RVAT, (C) VVtat, (D) LVEDi and (E) VEU. Acronyms follow those of Figures 3 and 4.
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