Substrate‐Based Ablation Guided by Combined Fractionation and Frequency Analysis for Multiple and Unmappable Ventricular Tachycardias

Figures

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  FIGURE 1. ECGs during sinus rhythm and VT. The cycle length (CL) of clinical VT was 330 ms. Lead I showed a Qr pattern, leads II and III an RR pattern, lead V1 an rS pattern, and lead V6 an RR pattern. Four types of VT were induced during the procedure, and all differed from the clinical VT. VT1 and VT2 had a superior axis, while VT3, VT4, and the clinical VT had an inferior axis. From the precordial leads, VT1 and VT2 were suspected to originate from the apex. VT3, VT4, and the clinical VT showed an R wave in V1. VT2 and VT3 could be mapped. VT3 terminated during mapping and was incomplete. VT1 and VT4 were hemodynamically unstable, so activation mapping was not performed. CL, cycle length; SR, sinus rhythm.

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  FIGURE 2. Substrate map. A substrate map of the left ventricle was created during right ventricular pacing. The left panel shows a voltage map obtained using near‐field detection. The right panel shows Isochronal late activation mapping (ILAM). White circles (1 cm in diameter) indicate deceleration zones. Low‐voltage areas were seen in the apex and on the anterior‐lateral wall. Voltage was relatively preserved in the septum. Delayed potentials were seen in the apical low‐voltage area (light blue tags). Two good pace maps for VT1 were identified nearby (white tags). A good pace map for VT2 was also found (yellow tag).

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  FIGURE 3. VT2 activation map. VT2 rotated within the low‐voltage area of the apex. The white dashed lines show the conduction direction estimated from the activation map during VT2. Mid‐diastolic potentials were recorded around the circuit (green tags). The VT2 circuit likely enters near the yellow tag and exits near the VT1 good pace map point (white tag). The local electrogram at the yellow tag showed a fragmented diastolic potential. Radiofrequency energy delivered at this site terminated VT after 52 s.

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  FIGURE 4. (A) Local electrograms on and around the VT2 isthmus. A voltage map during right ventricular pacing is shown. The white dashed lines show the conduction direction estimated from the activation map during VT2. Local electrograms, fractionation number, and peak frequency (PF) are shown at the entrance, isthmus, exit, and outer loop. Electrograms within the VT circuit had relatively higher fractionation number and higher PF than surrounding areas. Ablation near the entrance terminated the VT. PF, peak frequency. (B) Emphasis map (voltage map+fractionation map). This is an emphasis map that combines the voltage and fractionation maps. The white dashed lines show the conduction direction estimated from the activation map during VT2. Yellow tags mark the VT entrance, and white tags mark the exit. We changed the fractionation threshold stepwise from 1 to 9. Mapping points that meet the fractionation threshold are shown as small fluorescent yellow dots. The figures show fractionation thresholds of 4, 5, and 6. The VT‐related region was most clearly delineated at a fractionation threshold of 5. (C) Emphasis map (voltage map + fraction map + peak frequency map). This emphasis map combines…