Atrial substrate characterization based on bipolar voltage electrograms acquired with multipolar, focal and mini-electrode catheters

Prospective evaluation of antral lesion size of the 31-mm size of a novel size-adjustable cryoballoon: Results of the BETTER-FIT study

Background

A novel size-adjustable cryoballoon can deliver cryotherapy with a 28- or 31-mm balloon size. However, data on antral lesion size with the 31-mm balloon size are scarce.

Objective

The purpose of this study was to evaluate the antral lesion size of cryoablation with the 31-mm balloon size.

Methods

This prospective single-center study included patients with paroxysmal atrial fibrillation undergoing first-time pulmonary vein isolation (PVI). All pulmonary veins (PVs) were first ablated with the 31-mm balloon size. The 28-mm balloon size was only used as bailout. Pre- and postablation left atrial ultrahigh-definition mapping was performed to assess the antral lesion area. Secondary outcome measures were procedural efficacy including balloon occlusion grade.

Results

Complete PVI was achieved in all 80 PVs in 20 patients (mean age 59.7 ± 10.7 years, 75% male). More than one-third of the posterior wall was ablated (35.4% ± 13.8%), and the isolated surface area was 68.7% ± 8.5%. Lateral and septal circumferential antral lesion areas were 12.1 ± 2.0 cm2 and 19.1 ± 4.7 cm2, respectively. One patient demonstrated inadvertent overlap of the antral lesions on the roof. There was a trend toward lower complete balloon occlusion in the right superior PV with the 31-mm balloon size in comparison to the 28-mm size (75% and 90%, P = .08).

Conclusion

Cryoablation with the 31-mm size of a novel size-adjustable cryoballoon results in a large antral lesion. In small atria there is the potential for leaving a small nonablated corridor on the roof when using the 31-mm balloon in both superior PVs, which may be proarrhythmogenic.

Effect of electrode size and distance to tissue on unipolar and bipolar voltage electrograms and their implications for a near-field cutoff

Characteristics of electrograms depend on the electrode design and distance to the electric source. Our aim was to assess the impact of electrode design and distance from the myocardial electric source on the unipolar and bipolar electrograms to deduce a far-field cut-off. We retrospectively analyzed left atrial electroanatomical maps of 25 patients acquired using an ablation catheter with a 4.5 mm tip-, mini- and 2 mm ring electrodes. The unipolar and bipolar electrograms were characterized based on peak-to-peak amplitude, signal duration, maximal slope, and relative power of the high frequency spectrum above 50 Hz (HF_rel). The unipolar electrograms of ring electrodes showed an increased amplitude (140%), slope (150%) and HF_rel (16% vs. 11%) compared to the tip- and mini-electrodes. The median amplitude, slope, and HF_rel for the ring electrodes followed a power-law decay with distance with a steep decline up to 4 mm. This near-field cut-off can be identified based on a HF_rel above 10% in unipolar electrograms. In conclusion, we observed a higher unipolar amplitude for small ring-electrodes compared to larger tip-electrodes. The rapid decay of the amplitude, slope, and HF_rel up to a distance of 4 mm is suggestive for near-field cut-off identified based on HF_rel above 50 Hz.Clinical Trial Registration: NCT04095559.

Pacing cycle length-dependent electrophysiologic changes in left atrium: Poor validity of using low-voltage area and slow conduction area under specific pacing cycle length as absolute substrates of atrial fibrillation

BACKGROUND

Pacing cycle length (PCL)-dependent changes in left atrial (LA) electrophysiologic properties have not been fully elucidated.

OBJECTIVE

We aimed to elucidate these changes using a high-resolution mapping system.

METHODS

Forty-eight patients underwent atrial fibrillation ablation with RHYTHMIA HDx. Paired LA maps under a baseline PCL (600 ms) and rapid PCL (300 ms) were acquired after pulmonary vein isolation under right atrial appendage pacing. The PCL-dependent change in the low-voltage area (LVA; area with <0.5 mV bipolar voltage), LA activation time (interval from first LA activation to wavefront collision at lateral wall), regional mean voltage, regional mean wave propagation velocity, and slow conduction area (area with <0.3 m/s wave propagation velocity) were quantitatively analyzed.

RESULTS

Under the rapid PCL, the total LVA was significantly increased (7.6 ± 9.5 cm2 vs 6.7 ± 7.6 cm2; P = .031), especially in patients with a 10 cm2 LVA on the baseline PCL map (21.5 ± 9.1 cm2 vs 18.1 ± 6.5 cm2; P = .013). The LA activation time was also prolonged (87.9 ± 16.2 ms vs 84.0 ± 14.0 ms; P < .0001). Although the rapid PCL did not decrease the regional mean voltage, it significantly decreased the regional mean wave propagation velocity and increased the slow conduction area in all measured regions.

CONCLUSION

LVA and slow conduction area can be emphasized by rapid PCL LA mapping. There may be poor validity in using these areas as absolute atrial fibrillation substrates without considering the PCL-dependent changes.

Interactions of contact force, impedance, and power during repeated atrial arrhythmia ablation after previous atrial fibrillation ablation

BACKGROUND

Acutely effective repeated radiofrequency catheter ablation (RFCA) after previous atrial fibrillation ablation depends on several parameters including local impedance (LI), contact force (CF), and power.

OBJECTIVE

We aimed to investigate the relationship of LI, CF, and power to the LI drop in a repeated atrial RFCA environment.

METHODS

Consecutive patients undergoing repeated atrial RFCA were studied. High-quality local electrograms were analyzed for morphology changes indicating effective RFCA and associated LI dynamics. The influence of baseline LI, mean CF, and power on the LI drop was analyzed. Investigated power levels included ≤25 W, 30 W, and ≥40 W.

RESULTS

A total of 1390 RFCA points from 48 patients (48% female; median age, 70 years) were analyzed. Of 309 analyzed electrograms, 40.5% showed effective RFCA morphology changes with an elevated median LI drop (effective, 19.7 Ω; partially effective, 14.1 Ω; P < .001). CF showed the highest correlation to the LI drop within high baseline LI and when applying ≥40 W (low baseline LI, R = 0.39; intermediate, R = 0.66; high, R = 0.72). Within low baseline LI regions, CF levels showed a lower correlation to the LI drop (≤25 W, R = 0.30; 30 W, R = 0.35; ≥40 W, R = 0.39). A mean CF ≥10 g resulted in elevated LI drops with higher power compared with lower power within all baseline LI tertiles (P < .001 each).

CONCLUSION

Within high baseline LI regions, CF plays a greater role for the maximum LI drop when higher power is chosen. A mean CF ≥10 g ensures elevated LI drops with increasing power levels.

Durability of thermal pulmonary vein isolation in persistent atrial fibrillation assessed by mandated repeat invasive study

BACKGROUND

No study has assessed the durability of pulmonary vein isolation (PVI) with radiofrequency (RF) and cryoballoon (CB) in patients with persistent atrial fibrillation. These data are especially lacking for those with significantly diseased left atria (LA).

OBJECTIVES

The goals of this study were to assess PVI durability in patients with significant LA disease and to compare reconnection rates between RF and CB.

METHODS

Forty-four patients (mean age 63 years; 34 (77%) male; median time since atrial fibrillation diagnosis 22.5 months; median indexed LA volume 36 mL/m2) were randomized 1:1 to RF or CB PVI. A redo procedure using ultra-high-density electroanatomic mapping was mandated at 2 months, where PV reconnections were identified and reisolated.

RESULTS

Thirty-eight patients underwent both procedures (CB n = 17; RF n = 21). Index RF procedures were longer (median 158 minutes vs 97 minutes; P < .001) but required less fluoroscopy (9.5 minutes vs 23 minutes; P < .001). At the index RF procedure, a median of 47% of LA myocardium had voltage < 0.5 mV, suggesting that half of the mapped LA comprised scar. PV reconnection was observed in 73 of 152 PVs (48.0%) and was more frequent with CB (58.8%) than with RF (39.3%) (P = .022). Reconnection of at least 1 PV was detected in >75% of patients. Significantly more ablation was required during the redo procedure to reisolate PVs in the CB arm (median 10.8 minutes vs 1.2 minutes; P < .001).

CONCLUSION

PVI durability may be poor in those with significant LA scarring and dilatation, even with modern thermal ablation technologies. RF resulted in significantly better PVI durability than did CB in this complex population.