Conduction system pacing preserves both electrical and mechanical interventricular synchrony, a UHF ECG validation study
Authors: Mizner J , Jurak P , Linkova H , Stros P , Sussenbek O , Vesela J , Beela A , Lumens J , Curila K 
Published: May 2024

Abstract

Background
Interventricular mechanical delay (IVMD) is an established echocardiographic risk factor for pacing-induced cardiomyopathy development. Ultra-high-frequency ECG (UHF-ECG) is a non-invasive tool visualizing the ventricular activation sequence.

Purpose
To compare UHF-ECG interventricular dyssynchrony with echocardiography and to establish interventricular dyssynchrony related to conductive system pacing (CSP) and right ventricular myocardial pacing (RVP).

Methods
53 patients with advanced AV conduction disease, without organic heart disease, and preserved LV systolic function were prospectively included. Thirty-two had RVP, and twenty-one had CSP. CSP included both His bundle pacing (n=5) and left bundle branch area pacing (n=16). UHF-ECG and echocardiography were obtained at the baseline (during spontaneous rhythm) and after 1 year (during pacing). IVMD was manually calculated as a difference between the time from a distinct point of the QRS until the onset of the flow through LV and RV outflow tract using pulsed wave doppler imaging. Analysis was performed by two experienced and blinded cardiologists. Interventricular e-DYS was calculated automatically by a software as a time difference between activation in V8 (LV free wall) and V1 electrode (RV free wall).

Results
The average age of all included patients was 76 ± 6 years old and patients in both RVP and CSP group had similar clinical characteristics. The values of IVMD and interventricular e-DYS were similar in the whole study population both before the pacemaker implantation (-2 ± 21 ms for IVMD vs. 0 ± 20 ms for interventricular e-DYS; p=0.31) and after one year (14 ± 23 ms for IVMD vs. 14 ± 24 ms for UHF; p = 0.7). There were no significant differences in the baseline IVMD and interventricular e-DYS between those receiving CSP vs. RVP (IVMD -6 ± 22 ms for CSP vs 2 ± 20 ms for RVP, p=0.22) and interventricular e-DYS (e-DYS -5 ± 20 ms for CSP vs. 3 ± 20 ms for RVP, p=0.34). After one year of pacing, the patients with CSP preserved similar levels of both IVMD (mean change -2 ± 5 ms, p=0.74) and interventricular e-DYS V8-V1 (mean change 0 ± 4 ms, p = 0.95) – Figure 1. There was no difference between IVMD and interventricular e-DYS in CSP patients after one year (p=0.92). On the contrary, in the RVP group IVMD increased for 27 ± 5 ms (p &lt;0.0001) and interventricular e-DYS for 24 ± 5 ms (p &lt;0.0001) compared to the baseline - Figure 1. There was no difference between IVMD and interventricular e-DYS in RVP patients after one year (p=0.75). There was a moderate overall correlation between IVMD and e-DYS V8-V1 in all studied ventricular rhythms (R=0.73, p&lt;0.0001) – Figure 2.

Conclusions
UHF-ECG expresses the interventricular dyssynchrony noninvasively by measuring the activation difference between V8-V1 chest leads. RV myocardial pacing increases interventricular dyssynchrony, while CSP preserves synchronous ventricular activation.CSP vs RVPcorrelation of dyssynchrony