Ablation of Cavotricuspid Isthmus-Dependent Flutter Using a Mini-Electrode-Equipped 8-mm Ablation Catheter: Case Series

Ablation of CTI-dependent flutter using different ablation technologies: acute and long-term outcome from the LEONARDO study

BACKGROUND

A novel ablation catheter has been released to map and ablate the cavo-tricuspid isthmus (CTI) in patients with atrial flutter (AFL), improving ablation efficiency.

METHODS

We evaluated the acute and long-term outcome of CTI ablation aiming at bidirectional conduction block (BDB) in a prospective, multicenter cohort study enrolling 500 patients indicated for typical AFL ablation. Patients were grouped on the basis of the AFL ablation method (linear anatomical approach, Conv group n = 425, or maximum voltage guided, MVG group, n = 75) and ablation catheter (mini-electrodes technology, MiFi group, n = 254, or a standard 8-mm ablation catheter, BLZ group, n = 246).

RESULTS

Complete BDB according to both validation criteria (sequential detailed activation mapping or mapping only the ablation site) was achieved in 443 patients (88.6%). The number of RF applications needed to achieve BDB was lower in the MiFi MVG group vs both the MiFi Conv group and the BLZ Conv group (3.2 ± 2 vs 5.2 ± 4 vs 9.3 ± 5, p < 0.0001 for all comparisons). Fluoroscopy time was similar among groups, whereas we observed a reduction in the procedure duration from the BLZ Conv group (61.9 ± 26min) to the MiFi MVG group (50.6 ± 17min, p = 0.048). During a mean follow-up of 548 ± 304 days, 32 (6.2%) patients suffered an AFL recurrence. No differences were found according to BDB achieved by both validation criteria.

CONCLUSIONS

Ablation was highly effective in achieving acute CTI BDB and long-term arrhythmia freedom irrespective of the ablation strategy or the validation criteria for CTI chosen by the operator. The use of an ablation catheter equipped with mini-electrodes technology seems to improve ablation efficiency.

CLINICAL TRIAL REGISTRATION

Atrial Flutter Ablation in a Real World Population. (LEONARDO).

CLINICALTRIALS

gov Identifier: NCT02591875.

Minielectrode catheter technology for near zero-fluoroscopy substrate-guided ablation of typical atrial flutter

Background

MicroFidelity catheter technology may facilitate voltage-guided ablation by high-resolution electroanatomic mapping (HR-EAM) and precisely targeted energy application.

Objective

To evaluate the performance of minielectrode (ME) technology for zero-fluoroscopy substrate-guided cavotricuspid isthmus (CTI) ablation.

Methods

Eighty-two patients underwent near zero-fluoroscopy substrate-guided CTI ablation using a nonirrigated large-tip catheter with 3 MEs. The CTI was subdivided into 15 electroanatomic segments. Bipolar voltage maps were compared with ME signals. The outcome was compared with a historic cohort of 92 patients who underwent linear ablation.

Results

Compared with linear ablation, the substrate-guided approach was associated with an almost halved ablation duration (336 ± 228 vs 649 ± 409 seconds, P < .001), halved radiofrequency energy applied (14.2 ± 10.6 vs 28.6 ± 19.6 kJ, P < .001), and shorter procedure duration (60.8 ± 33.8 vs 76.3 ± 40.9 minutes, P = .008) limiting the extent of energy delivery to 22.7% of the CTI area. HR-EAM visualized 2.03 ± 0.88 conductive pathways with a diameter of 5.35 ± 1.98 mm. A higher number of ME-detected bundles and a larger channel diameter correlated with increased ablation requirements. In 97.6% of the voltage-guided and 88.0% of the linear procedures, fluoroscopy was not used.

Conclusion

HR-EAM-based substrate-guided CTI ablation may improve procedural outcome compared with the linear approach. Enhanced identification of discrete conductive pathways correlates with ablation efficacy. The electroanatomic subdivision of the CTI into 15 segments was feasible and may improve the understanding and comparability of anatomic variants and ablation results. Independent of the ablation strategy, modern EAM technology enables safe zero-fluoroscopy procedures in the majority of cases.

How to avoid unnecessary RF applications in cavo-tricuspid isthmus: common atrial flutter ablation using 8-mm-tip mini-electrode-equipped catheter

PURPOSE

Eight-millimeter-tip ablation catheters are characterized by poor mapping resolution as they depend on electrode size and spacing. IntellaTip MiFi XP 8-mm (Boston Scientific) catheters offer high mapping resolution due to 3 mini-electrodes (ME) located at the distal tip of the catheter and are dedicated for cavo-tricuspid isthmus (CTI) radiofrequency ablation (RFA). The aim of the study was to evaluate the usefulness, effectiveness and safety of novel IntellaTip MiFi XP catheter for CTI RFA and its ability to localize anatomical structures of the heart.

METHODS

The study included 10 patients referred for atrial flutter ablation. The 3D mapping system EnSite Velocity was utilized for catheter visualization. The ME signals were used for tricuspid annulus visualization, RF delivery effectiveness assessment defined as ME signal attenuation, and localization of the gaps in the ablation line. The use of ME signals for TV annulus localization resulted in a 13.9 mm (35.5 ± 4.8 mm vs 49.4 ± 7.8 mm; p < 0.01) shorter ablation line in comparison with the potential ablation line designed using standard bipol. The ablation endpoint, bidirectional block, was achieved in all 10 cases (100%) and lasted for at least 15 min after the last RF delivery. The ablation endpoint was reached after 5.1 ± 1.67 RF applications. The total RF time was 220 ± 61 s. Total procedure time was 66 ± 13.5 min, fluoroscopy time 3.92 ± 4.21 min, and total fluoroscopy dose 40.3 ± 56.5 mGy.

RESULTS

In 3 out of 10 cases, there was a need of filling the gap with 1-2 additional applications after the first linear lesion set. No additional RF applications were required at the annular end of the ablation line. The indirect comparison with previously conducted studies using a standard 8-mm ablation catheter shows that the studied catheter has at least the same or even better performance.

CONCLUSIONS

The use of the novel IntellaTip MiFi XP may help to avoid unnecessary RF application especially at the annular part of cavo-tricuspid isthmus and enables a purely electrophysiological approach to atrial flutter ablation, as high-resolution ME signals help to understand local electrophysiological phenomena.

Additional Diagnostic value of Mini Electrodes in an 8-mm Tip in Cavotricuspid Isthmus Ablation

Background

Eight-mm ablation catheters are widely used in cavotricuspid isthmus ablation (CTI) for treatment of right sided atrial flutter. However a high success rate, these large ablation tips comes with adisadvantage of lower resolution of fractionated signals.

Purpose

The aim of this study was to evaluate the additional diagnostic value of the electrograms recordedfrom mini electrodes (MEs) in an 8-mm ablation catheter tip during CTI.

Methods

CTI-ablation procedures were compared retrospectively in two groups, namely, group A: the Abbott Safire 8-mm tip with a 3D mapping system (n =37) and group B: the Boston Scientific MiFi IntellaTip XP 8-mm tip without a 3D mapping system (n=13). We analyzedacute procedural success, ablation characteristics and recurrence rate at one-year follow-up. Electrograms from MEs were analyzedright before the onset of the critical ablation application that resulted in acute CTI-block. We determined whether these ME electrograms had additional diagnostic value in addition to of the 8-mm tip derivedelectrogram.

Results

At the onset of the critical ablation application, the MEs had an important additional value in 3 out of 13 cases as local signals were sensed on the MEs that were not recorded by the 8-mm tip electrode. In 2cases the ME did not show local electrogramsalthough the ablationwas still effective. Acute procedural and long-term success wereobserved in all patients. No differences were found in time to bidirectional block, procedure time or fluoroscopic exposure.

Conclusion

Our data show that signals recorded from the MEs had additional diagnostic value, but only in asmall percentage of the patients. We did not observe, although omitting 3D-mapping in the ME group, any differencebetween groups with regard to procedural or ablation characteristicsduring CTI-ablation.