Electrical and mechanical interventricular dyssynchrony coupling in patients with bradycardia: A UHF-ECG validation trial

Background: Ultra-high-frequency electrocardiography (UHF-ECG) is a noninvasive tool visualizing the ventricular activation sequence. It was never compared with other methods of dyssynchrony assessment in patients with bradycardia. Objective: We aimed to compare UHF-ECG interventricular electrical dyssynchrony (e-DYS) with interventricular mechanical delay (IVMD) measured by echocardiography in patients receiving right ventricular pacing (RVP) or conduction system pacing (CSP). Methods: Fifty-three patients with advanced atrioventricular conduction disease and preserved ventricular systolic function were prospectively assigned to RVP (n=32 [60 %]) or CSP (n=21 [40 %]). IVMD was measured as the time difference between left ventricular and right ventricular preejection periods. Interventricular e-DYS was calculated by software as the time difference between activation in V ₁ and V ₇ chest electrodes using UHF-ECG. Results: The median age of patients was 75 (interquartile range 72–80) years, and both groups had similar clinical characteristics. Baseline IVMD and interventricular e-DYS were similar in the entire population (−2 [−8 to 5] ms vs−1 [−6 to 5] ms, respectively; P=.52). Both methods showed the same dyssynchrony trends after pacemaker implantation; that is, while both IVMD and interventricular e-DYS increased in the RVP group (IVMD 28 [23–33] ms vs interventricular e-DYS 26 [19–33] ms; P=.99), they remained low in the CSP group (IVMD −7 [−16 to 2] ms vs interventricular e-DYS −5 [−12 to 2] ms; P=.91). There was a moderate overall correlation between IVMD and interventricular e-DYS for all studied ventricular rhythms (R=0.74). Conclusion: UHF-ECG noninvasively expresses interventricular dyssynchrony from V ₇–V ₁ chest leads with similar results to echocardiography. RVP increases interventricular dyssynchrony, while CSP preserves synchronous ventricular activation.