A case of scar-related ventricular tachycardia demonstrating termination with nonglobal capture at the site of concealed entrainment with dual slow conduction pathways

Figures

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  Figure 1. A: Voltage map of the left ventricle acquired using the CartoSound system. A bipolar electrogram amplitude of <1.5 mV was defined as low voltage, and sites with low voltage of <0.5 mV were designated as scarred areas. The low-voltage zone was observed in the inferoposterior left ventricle. Delayed potential (DP) was recorded at the site indicated by the blue circle (arrow). B: Ablation catheter in situ demonstrating concealed entrainment and termination with nonglobal capture in fluoroscopic images. C: At the same point as shown in panel A, DP was recorded during sinus rhythm (SR). D: In the induced ventricular tachycardia (VT), the VT cycle length was 340 ms and the QRS morphology (left bundle branch block and superior axis type) of VT was similar to that of clinical VT. E: Pacing was performed during SR at 120, 160, and 180 beats/min, and the stimulus-QRS (S-QRS) interval ranged from 85 to 87 ms without decremental properties. ABL = ablation catheter; HBE = His bundle electrogram; LAO = left anterior oblique; PA = posteroanterior; RAO = right anterior oblique; RVA = right ventricular apex; RVOT = right ventricular outflow tract; TCL = tachycardia cycle length.

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  Figure 2. A: Pacing with a pacing cycle length (PCL) of 325 ms during the entrained ventricular tachycardia (VT) with concealed fusion (concealed entrainment). The postpacing interval (PPI) from stimulus to presystolic potential (PP) at the ablation catheter (ABL1,2) was 355 ms, which approximated the VT cycle length (CL) of 340 ms. The stimulus-QRS (S-QRS) interval was 90 ms, which was within 30% of the VT CL and was therefore consistent with the exit site in the reentry circuit. B: Pacing with a PCL of 320 ms demonstrated that the S-QRS interval was extremely prolonged to 268 ms with an identical QRS complex, followed by termination with nonglobal capture (NGC). After termination of VT, stimulus directly captured the global myocardium, probably including conduction to the entrance site, which was proved by demonstration of a QRS morphology different from that of VT. C: VT was also terminated with NGC by premature single stimulus at this site. The coupling interval from ventricular electrogram to stimulus was 50 ms, which was similar to that in overdrive pacing with a PCL of 320 ms. D: VT was terminated 1 second after the initiation of radiofrequency energy application at this same site…

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  Figure 3. A: Scheme of the ventricular tachycardia (VT) circuit and pacing site. B: Concealed entrainment was obtained by pacing with a pacing cycle length (PCL) of 325 ms. Propagation conducted through slow pathway 1 (SP1). C: The wavefront propagated through slow pathway 2 (SP2) by pacing with a PCL of 320 ms during VT. The SP1 refractory period might be shorter than that of SP2, although the conduction time in SP2 was longer than that in SP1. The exit site distal to both SP1 and SP2 was considered the same site. D: Termination with nonglobal capture with conduction block of SP2 repeatedly occurred by continuous pacing with a PCL of 320 ms. S-QRS = stimulus to the QRS complex.