Impact of Interelectrode Spacing on Ventricular Tachycardia Substrate Mapping

BACKGROUND: Re-entrant ventricular tachycardia (VT) circuits often involve 3-dimensional activation across the endocardium, epicardium, and mid-myocardium, highlighting the importance of comprehensive substrate assessment. Wider interelectrode spacing may incorporate broader-field electrical components that are less apparent on conventional closely spaced recordings. OBJECTIVES: This study sought to investigate the electrophysiological impact of interelectrode spacing on substrate mapping and its potential implications for 3-dimensional features of VT substrate. METHODS: Sixty-eight high-density substrate maps from 35 patients undergoing catheter ablation for scar-related VT were retrospectively analyzed. Closely spaced (2-mm) and widely spaced (8-mm) bipolar electrograms were simultaneously acquired using a decapolar catheter and used to generate closely and widely spaced bipolar electrode maps (CEM and WEM). RESULTS: Compared with CEM, WEM, which incorporates a greater contribution of far-field components, demonstrated higher bipolar amplitudes, a greater prevalence of multicomponent electrograms, and a lower prevalence of split potentials (all P < 0.01). Lines of block delineated by split potentials on CEM were frequently attenuated or no longer apparent on WEM because the corresponding electrograms appeared fragmented and lacked a distinct split configuration. In an exploratory analysis of 6 VTs with evaluable activation maps, activation gaps were larger with closely than widely spaced bipolar mapping (32.5% vs 20.0%; P = 0.03). In 4 VTs, widely spaced recordings identified diastolic or presystolic far-field potentials not evident with closely spaced recordings. CONCLUSIONS: Widely spaced bipolar electrograms may provide complementary functional information beyond that obtained with conventional near-field recordings by incorporating broader-field electrical components, thereby offering additional insight into the potential 3-dimensional characteristics of the arrhythmogenic substrate.