Resynchronisation efficacy of pacing strategies depends on the assessment metric: a computational study.

Background: Current evaluation of ventricular resynchronisation relies largely on ECGbased metrics, which do not fully capture the complexity of electrical synchrony. Reliance on a single clinical metric provides limited insight into the restoration of the intrinsic physiological activation sequence. To address this, we employed high-fidelity computational simulations using a multiple-metrics framework to mechanistically compare established pacing strategies. Methods: A high-resolution, anatomically and biophysically detailed four-chamber human model was used to compare the resynchronisation efficacy of conduction system pacing and biventricular pacing under focal bundle branch block. Outcomes were evaluated using: (1) ECG markers (QRS duration, Hisio-ventricular interval, V6-V1 interpeak interval, V6 R-wave peak time); (2) high-density activation maps; and (3) ventricular activation velocity, a novel metric of depolarisation dynamics. Results: Simulation results showed that pacing efficacy depended on the chosen metric. biventricular pacing improved ECG markers (e.g., QRS 120 to 90 ms) and activation velocity, but activation maps deviated most from physiological patterns. conduction system pacing produced maps resembling normal sinus rhythm, though velocity profiles showed residual dyssynchrony, highlighting that improvement on one metric did not guarantee improvement on another. Conclusion: These findings show that pacing efficacy depends on the evaluation metric and that single-metric assessment cannot capture the complex dynamics of ventricular resynchronisation. Patient-specific computational modelling offers a promising approach for non-invasive, multi-modal in silico evaluation.