Visualization of atrial activation during tachycardia enabled by 2:1 His-ventricular block for slow pathway localization in slow-fast atrioventricular nodal reentrant tachycardia: A case using advanced mapping algorithms

Figures

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  Figure 1. Tachycardia and subsequent 2:1 HV block. A: The tachycardia cycle length and VA interval were 390 ms and 30 ms, respectively, consistent with typical slow–fast AVNRT. B: During sustained tachycardia, a regular 2:1 HV block was observed. The tachycardia cycle length was 380 ms. AVNRT = atrioventricular nodal reentrant tachycardia; HV = His-ventricular; VA = ventriculoatrial.

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  Figure 2. Sinus rhythm mapping and frequency analysis. A: Activation map showing a pivot point in the inferior septal region. B: Voltage map demonstrating a low-voltage bridge (0.1–1.0 mV) extending from the AV node region to the coronary sinus along the tricuspid annulus. C: Peak frequency map showing high-frequency activity (>300 Hz) at the 5 o’clock position with electrograms resembling Jackman potentials.

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  Figure 3. Activation map and spectral analysis during supraventricular tachycardia without HV block. A: Activation map showing a pivot-like conduction pattern in the same region identified during sinus rhythm. Interpretation was limited by the overlap of atrial and ventricular components. B: Fractionation mapping identifying a localized region with a threshold value ≥7. C: Peak frequency analysis (180–210 Hz) showing spatial correlation with the fractionation site. D: Separate high-frequency activity (>300 Hz) observed at a site matching the high-frequency area seen during sinus rhythm, indicating rhythm-independent substrate concordance.

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  Figure 4. Activation map and spectral analysis during supraventricular tachycardia with 2:1 HV block. A: Activation map constructed by excluding ventricular components from the annotation window, revealing a pivot-like conduction pattern in the inferior septal region. B: Fractionation mapping using a threshold of 4 showing a localized area consistent with the site identified during tachycardia without HV block. C: Peak frequency analysis (180–210 Hz) showing spatial concordance with the fractionation area. D: The area of high-frequency activity corresponded to the same region observed during both sinus rhythm and tachycardia without HV block. HV = His-ventricular.

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  Figure 5. Ablation site and its correlation with previously identified mapping features. The ablation site was in the lower septal region, corresponding to the area of high-peak frequency activity observed during both sinus rhythm and tachycardia. The fractionation, middle peak frequency area, and His bundle recording site are also shown. For procedural safety, the ablation site was selected to be slightly inferior to these regions while still targeting the functionally relevant substrate.