A novel approach for LV delay evaluation: non-invasive QLV measurement using UHF-ECG

Introduction: Ultra-high-frequency ECG (UHF-ECG) which displays ventricular dyssynchrony may be a valuable tool for improving the selection and treatment of patients with indication to cardiac resynchronization therapy (CRT). Objective: To compare noninvasive assessment of LV delay using UHF-ECG with invasive QLV in CRT, and to evaluate the effect of biventricular CRT on LV resynchronization and remodeling. Methods: Consecutive patients undergoing CRT at two centers were included. LV lead positions were classified as basal, midventricular, or apical lateral wall. QLV was measured from QRS onset to the steepest EGM deflection. UHF-ECG LV delay was measured from QRS onset to local activation in leads V5-V8. LV dyssynchrony was calculated as the time from the earliest activation to the latest activation in leads V4-V8. Results: 48 patients were included (75 % male, age 67 ± 12 years, LVEF 31 ± 6 %, QRSd 167 ± 20 ms). UHF-ECG activation delay in V8 did not differ from QLV in the basal segment (3 ± 14 ms, p = 0.52). QLV from the midventricular segment did not differ from UHF-ECG activation in V7 (3±17 ms, p=0.18). QLV from the apical segment was not different from UHF-ECG activation in V6 (0±17 ms, p=0.92). Patients with QLV and lv-DYS above 95 and 60 ms showed a more significant reduction in LV dyssynchrony and were more often responders to CRT than patients with shorter values (lv-DYS -70 ms vs. -8 ms, and responders 95 % vs. 24 %). Conclusion: UHF-ECG enables noninvasive estimation of QLV and assessment of CRT response, which may have important clinical implications for the evaluation and management of CRT candidates.