Is the mid-diastolic isthmus always the best ablation target for re-entrant atrial tachycardias?

Visualization of residual gaps after linear ablation using the LUMIPOINTTM module: A case report

BACKGROUND

Macroreentrant atrial tachycardia (ATs) through epicardial conduction is depicted as a focal AT on 3-D mapping, i.e., pseudo-focal AT. A new feature of the Rhythmia mapping system (Boston Scientific), the "LUMIPOINT module", can highlight all electrocardiograms (EGMs) above a threshold determined by an adjustable confidence slider (CS). Lowering the CS (L-CS) may highlight undetected electrograms (EGMs) at the nominal CS setting, potentially enabling visualization of the critical isthmus of pseudo-focal ATs.

METHODS AND RESULTS

This study included 3 ATs after linear ablation of two left atrial roof-dependent ATs (cases 1 and 2) and one peri-mitral flutter (case 3). All ATs were diagnosed as pseudo-focal AT according to an electrophysiological study and the Rhythmia mapping system with the LUMIPOINT module. The L-CS method consisted of the following steps: 1. Set the LUMIPOINT activation window to the time difference before and after the linear ablation line. 2. Highlight the two regions before and after the linear ablation line. 3. Gradually lower the CS value from the nominal setting of 85 % by 5-10 %. By the L-CS method in cases 1-3, the 2-sided highlighted areas before and after the prior linear ablation lesion gradually expanded and eventually fused. EGMs at the fusion sites of the highlighted areas exhibited fragmented EGMs with a low voltage, where a single-shot ablation terminated the targeted ATs.

CONCLUSION

The L-CS method was useful for the visualization of residual gaps and identification of targeted ablation sites in cases of pseudo-focal AT after linear ablation of macroreentrant ATs.

Does Unidirectional Block Exist after a Radiofrequency Line Creation? Insights from Ultra-High-Density Mapping (The UNIBLOCK Study)

BACKGROUND

Whether unidirectional conduction block (UB) can be observed after creation of a radiofrequency (RF) line is still debated. Previous studies reported a prevalence of 9 to 33% of UB, but the assessment was performed using a point-by-point recording across the line. Ultra-high-density (UHD) system may bring some new insights on the exact prevalence of UB.

PURPOSE

A prospective study was conducted to assess the prevalence of UB and bidirectional block (BB) using UHD system after RF line creation.

METHODS

Patients referred for atrial RF ablation procedure were included in this multicenter prospective study. UHD maps were performed by pacing both sides of the created line.

RESULTS

A total of 80 maps were created in 40 patients (67 ± 12 years, 70% male) by pacing (mean cycle length 600 ± 57 ms) from both sides of the cavotricuspid isthmus line. After a 47 ± 17 min waiting time after the last RF application, UHD maps (mean number of 4842 ± 5010 electrograms, acquired during 6 ± 5 min) showed that BB was unambiguously confirmed on all of them. UB was not observed in any map. After a mean follow-up of 12 ± 4 months, 6 (14%) patients experienced an arrhythmia recurrence.

CONCLUSION

After creation of an RF line, no case of UB was observed using UHD mapping, suggesting that the presence of a conduction block along a RF line is always associated with a block in the opposite direction.

Basket catheter-guided ultra-high-density mapping of cardiac arrhythmias: a systematic review and meta-analysis

Aim: Ultra-high-density mapping (HDM) is increasingly used for guidance of catheter ablation in cardiac arrhythmias. While initial results are promising, a systematic evaluation of long-term outcome has not been performed so far. Methods: A systematic review and meta-analysis was conducted on studies investigating long-term outcome after Rhythmia HDM-guided atrial fibrillation (AF) or atrial tachycardia catheter ablation. Results: Beyond multiple studies providing novel insights into arrhythmia mechanisms, follow-up data from 17 studies analyzing Rhythmia HDM-guided ablation (1768 patients, 49% with previous ablation) were investigated. Cumulative acute success was 100/90.2%, while 12 months long-term pooled success displayed at 71.6/71.2% (AF/atrial tachycardia). Prospective data are limited, showing similar outcome between HDM-guided and conventional AF ablation. Conclusion: Acute results of HDM-guided catheter ablation are promising, while long-term success is challenged by complex arrhythmogenic substrates. Prospective randomized trials investigating different HDM-guided ablation strategies are warranted and underway.