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Figure 2 Ablation Sites of a VT Originating From the NCC Near the HB and in the NCC
Radiofrequency applications delivered near the His bundle (HB) region where the local ventricular activation preceded the QRS onset by 25 ms (left panel) caused a slight change in the QRS morphology with the prolongation of the QRS duration and an attenuation and delay of the high-amplitude near-field ventricular electrogram in the HB region (double arrowheads, center panel). The low-amplitude far-field ventricular electrogram (single arrowheads, center panel) preceding the QRS onset was then separated from the near-field ventricular electrogram after the QRS onset in the HB region. Successful radiofrequency ablation was achieved in the noncoronary cusp (NCC) where the local ventricular activation was recorded simultaneously with the activation of the far-field ventricular electrogram in the HB region (center panel). Note that the atrial electrogram with an amplitude greater than that of the ventricular electrogram was recorded at the successful ablation site during sinus rhythm (right panel). HBd = distal electrode pair of the His catheter; HBp = proximal electrode pair of the His catheter; VT = ventricular tachycardia; other abbreviations as in Figure 1.
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