Non-invasive assessment of left atrial activation using lead V8 during Bachmann bundle pacing

Bachmann bundle pacing (BBP) improves atrial synchrony by advancing LA activation, but quantifying inter-atrial synchronization remains challenging. This study evaluated whether lead V8 reflects posterolateral LA activation time and whether lead V8 can be used to assess the effect of BBP on LA activation.

Consecutive patients undergoing an electrophysiology study and ablation (Cohort 1) or BBP lead implantation (Cohort 2) were prospectively enrolled. Surface ECGs were recorded with the V5 electrode repositioned to the V8 location (2 cm below the inferior left scapula). LA activation was determined using the steepest negative downslope of the P-wave (NDAT-P-V8). Iso-V8 was defined as the time from P-wave onset to first positive deflection in lead V8. In Cohort 1, a coronary sinus (CS) catheter invasively determined activation timing at the posterolateral LA (mitral isthmus region). In Cohort 2, NDAT-P-V8 and iso-V8 were used to assess the effect of BBP on LA activation.

In Cohort 1 (n=50), NDAT-P-V8 strongly correlated with the latest CS activation (r = 0.94, p<0.001). In Cohort 2 (n=50), lead V8 facilitated intra-procedural assessment of LA activation. IAB was corrected in 20/23 (87%), accompanied by shortening of NDAT-P-V8 (from 120±25ms to 82±17ms, p<0.001) and iso-V8 (from 51±22ms to 18±17ms, p<0.001), consistent with earlier LA activation.

NDAT-P-V8 closely reflects the invasively determined timing of the posterolateral LA activation and provides a simple non-invasive marker to assess the effect of BBP on LA activation. Lead V8 may therefore help to assess and optimize atrial activation with BBP.