Evaluation of left ventricular dyssynchrony by ultra-high-frequency ECG in patients with non-LBBB conduction disorder treated with cardiac resynchronization therapy

Funding Acknowledgements

Type of funding sources: None.

Introduction

LBBB is a reliable left ventricular (LV) electrical dyssynchrony indicator. Patients with RBBB/IVCD are a heterogeneous group, where even with "larger" QRS complex expansion, LV dyssynchrony may not be present. Ultra-high-frequency (UHF) 14-lead ECG is a non-invasive method based on signal averaging that allows better assessment of local electrical activation of the ventricles than standard ECG. Our study aims to test the hypothesis of the usefulness of UHF ECG to select non-LBBB patients for cardiac resynchronization therapy (CRT) based on evidence of electrical dyssynchrony.

Methods

Using UHF ECG we analysed patients who underwent CRT implantation. The groups of patients with RBBB, IVCD, and LBBB were compared and the presence of electrical dyssynchrony (e-DYS) as a parameter of global ventricular activation, and delayed activation of the left ventricular lateral wall (LVLWd) as a marker of LV intravenricular dyssynchrony was assessed.

Results

UHF ECG was recorded in 49 patients treated with CRT. IVCD patients had lower e-DYS compared to LBBB patients (26±17 ms vs. 86±20 ms; p<0.0001) and lower LVLWd (26±16 ms vs. 83±22 ms; p<0.0001). In RBBB patients, e-DYS was -52±22 ms, corresponding to right ventricular delay. Delayed left ventricular free wall activation ("RBBB masking LBBB" activation pattern) was not found in any RBBB patient.

Conclusion

UHF ECG appears to be a promising tool to detect LV electrical dyssynchrony in non-LBBB candidates for cardiac resynchronization therapy. Delayed left ventricular free wall activation was not found in any RBBB patient. Our findings are consistent with the lack of effect of CRT in this group of patients.