Predictability of lesion durability for AF ablation using phased radiofrequency: Power, temperature, and duration impact creation of transmural lesions

The importance of electrode-tissue proximity in creating pulsed field ablation lesions: insights from a sub-acute preclinical model

BACKGROUND

We sought to evaluate the anatomic and functional lesion development over time at different atrial sites immediately following delivery of pulsed field ablation (PFA).

METHODS

Using a porcine model, PFA ablations were performed in the superior vena cava (SVC), right atrial lateral wall (RA), left atrial appendage (LAA), and right superior pulmonary vein (RSPV) using four different PFA profiles. Mapping was done sequentially in 5-20-min increments up to 280-min post lesion delivery for low voltage area (LVA) assessment and conduction velocity. Lesion characteristics were noted with voltage mapping immediately post ablation and at the serial time points.

RESULTS

In 9 animals, 33 sites were ablated. None of the four different profiles across all sites showed any statistical difference on acute lesion formation or persistence. Higher tissue contact was observed in the SVC and RSPV and lower tissue contact was observed in the LAA and RA locations. Higher contact areas were noted to have higher density electroanatomic low voltage area (LVA) (12/14 vs 5/18, p = 0.01) and larger lesions on gross pathology (2 /14 vs 6/16, p = 0.01) compared to lower contact areas. Lesion regression occurred in 16/33 sites. Sustained lesions were significantly more prevalent in higher versus lower contact sites (65% vs 38%, p = 0.037).

CONCLUSION

The development of significant and durable lesions for PFA in a porcine model appears to be dependent on tissue proximity and contact.

A novel polarity configuration for enhancing ablation depth of pulsed field ablation: Design, modeling, and in vivo validation

BACKGROUND

Pulsed field ablation (PFA) has been increasingly used to cut off the delivery of abnormal electrical signals in the treatment of cardiac arrhythmias. A successful cut off requires forming a layer of transmural damage on the heart wall, and this layer depends on the depth of ablation by PFA.

PURPOSE

This study aims to propose a novel polarity configuration of PFA to increase the ablation depth in the treatment of cardiac arrhythmias.

METHOD

A novel polarity configuration was designed for a multi-electrode system, where the number of electrodes is greater than two. The polarity configuration in such multi-electrode system is called the paired-electrode interlaced configuration (PIC). The existing configuration called the single-electrode interlaced configuration (SIC) was used to compare with the PIC. To both the SIC and PIC, a full-SIC or a full-PIC is called when all electrodes (anode, cathode) in a catheter is used otherwise partial-SIC or partial-PIC is called. By the comparison between the full-SIC and full-PIC, the benefit of the PIC was exhibited as opposed to the SIC, but an extra ablation step was added in the PIC in order to form a continuous ablation zone. The other comparative study was taken between a partial-PIC and a partial-SIC with the same number of ablation step. In this study, a rabbit model was built by infusing 0.4% saline solution (at 37°C) into the rabbit's abdominal cavity which surrounds the liver. This model was considered as a biometric environment of the heart, namely cardiac-mimetic model (CMM).

RESULT

The experimental results have shown that the full-PIC is superior to the full-SIC in the ablation depth, specifically in both the maximum (4.14 ± 0.55 mm vs. 3.35 ± 0.26 mm, p < 0.01) and the minimum (3.18 ± 0.29 mm vs. 2.76 ± 0.28 mm, p < 0.05), and in the ablation width, specifically only in the maximum (8.27 ± 0.76 mm vs. 7.09 ± 0.51 mm, p = 0.019) under an identical ablation time (i.e., 5 s). It is noted that the minimum ablation width did not show a significant difference between the full-PIC and full-SIC (specifically, 5.61 ± 0.86 mm vs. 4.67 ± 0.73 mm, p = 0.069). Considering the lethal electric field threshold (LEFT) to be 600 V/cm for liver tissues, the maximum and minimum ablation depth generated by the full-PIC was found larger than that by the full-SIC (3.90 vs. 3.52 mm, and 3.03 vs. 2.48 mm, respectively) in the simulation. Meanwhile, similar experiment results by comparing the partial-PIC and partial-SIC have been obtained, which shows a significant increase in both the maximum ablation depth (4.81 ± 0.87 mm vs. 3.30 ± 0.73 mm, p < 0.001) and the maximum ablation width (8.19 ± 0.85 mm vs. 6.47 ± 1.13 mm, p = 0.001).

CONCLUSIONS

(1) The electric field in the PIC is concentrated around the pair of electrodes, and the pattern of the field is a significant factor in the energy delivery along the direction of the depth. (2) The increase of the ablation depth can significantly expand the range of the tissue on the heart, where the PFA can apply, and can therefore readily form a layer of transmural damage on the heart wall at positions at which the wall is thicker.

Quantitative late gadolinium enhancement cardiac magnetic resonance analysis of the relationship between ablation parameter and left atrial tissue lesion following pulmonary vein isolation

Background

The impact of ablation parameters on acute tissue lesion formation after pulmonary vein isolation (PVI) has not been sufficiently evaluated in patients with atrial fibrillation. Radiofrequency ablation lesion can be visualized by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). We sought to quantitatively analyze the relationship between ablation parameter and tissue lesion following PVI at different segments of pulmonary vein (PV) using LGE-CMR.

Methods

Twenty-one patients with atrial fibrillation who underwent PVI procedure were retrospectively enrolled. All patients underwent LGE-CMR examination within 3 days after radiofrequency ablation. Ablation parameters during PVI were documented, including lesion size index (LSI), force-time integral (FTI), power, contact force, temperature, and time of duration. The ablation point was projected onto 3-dimensional (3D) left atrial shell constructed base on LGE-CMR and corresponding image intensity ratio (IIR) was calculated on the same shell. A tissue lesion point was defined when the LGE-CMR IIR was > 1.2.

Results

In total, 1,759 ablation points were analyzed. The ablation parameters and IIRs for each PV segment were significantly different (P < 0.0001). IIRs corresponding to ablation points at posterior of PV tended to be higher than those at non-posterior of PV when similar ablation parameters were applied during ablation. LSI was a better predictor of tissue lesion existence following PVI than FTI, contact force, power, temperature, and duration time at non-posterior wall of PV. The IIR showed positive correlation with LSI at non-posterior wall of PV (non-posterior of right PV, r = 0.13, P = 0.001, non-posterior of left PV, r = 0.26, P < 0.0001).

Conclusion

When similar ablation parameters were applied during PVI, the posterior wall of PV had more severe tissue lesion than non-posterior wall of PV. Therefore, it was reasonable to decrease ablation energy at posterior wall of PV. Moreover, LSI was a better index to reflect tissue lesion quality following PVI at non-posterior of PV.

The Incidence, Electrophysiological Characteristics and Ablation Outcome of Left Atrial Tachycardias after Pulmonary Vein Isolation Using Three Different Ablation Technologies

Background: Left atrial tachycardias (LAT) are a well-known outcome of pulmonary vein isolation (PVI). Few data are available on whether the catheter used to perform PVI influences the incidence, as well as the characteristics of post PVI LAT. We present data on LAT following PVI by the following three ablation technologies: (1) phased multi-electrode radiofrequency catheter (PVAC), (2) irrigated single-tip catheter (iRF), and (3) cryoballoon ablation. Methods: Using a prospectively designed single-center database, we analyzed 650 patients (300 iRF, 150 PVAC, and 200 cryoballoon) with paroxysmal (n = 401) and persistent atrial fibrillation (AF), who underwent their first PVI at our center. Results: The three populations were comparable in their baseline characteristics; however, the cryoballoon group comprised a higher percentage of patients with persistent AF (p = 0.05). The LAT rates were 3.7% in the iRF group (mean follow-up 22 ± 14 months), 0.7% in the PVAC group (mean follow-up 21 ± 14 months), and 4% in the cryoballoon group (mean follow-up 15 ± 8 months). The predominant mechanism of LAT was macro-reentrant tachycardia. Reconnection of at least one pulmonary vein was observed in 87% of the patients who underwent 3D mapping. No predictors for LAT occurrence were identified. Conclusion: The occurrence of LAT post PVI is rare; the predominant mechanism was macro-reentrant tachycardia. Reconnection of at least one pulmonary vein was observed in nearly all the LAT patients. In our retrospective analysis, the lowest rate of LAT was observed with the PVAC. No predictors for LAT occurrence were identified.

Choice of Steerable Sheath Impacts Contact Force Stability During Pulmonary Vein Isolation

A stable contact force (CF) is correlated with more effective radiofrequency (RF) ablation (RFA) lesions and long-term procedural outcomes. Efforts to improve catheter stability include jet ventilation, pacing, steerable sheaths, and CF-sensing ablation catheters. This study compares CF stability and effective RF lesions between two commercially available steerable sheaths. Thirty patients underwent first-time RFA at a single center using the Agilis™ NxT (Abbott, Chicago, IL, USA) or SureFlex™ (Baylis Medical, Montreal, Canada) steerable sheath. High-power short-duration RFA was utilized, targeting a 10-Ω drop. Sheath performance was assessed for the entire procedure and around each pulmonary vein (PV) in terms of mean CF, CF variability, RF time per lesion, and inefficient contact lesions (defined as lesions with a CF of less than 5 g for at least 10% of the RF delivery time). The operator-targeted mean CF was achieved using both sheaths; however, the overall CF variability was 12.8% lower when using the SureFlex™ sheath (p = 0.08). The CF variability was generally 16% greater in the right PVs than the left PVs (p = 0.001) but trended lower with the SureFlex™ sheath. There were 8% more inefficient contact lesions created when using the Agilis™ sheath as compared to the SureFlex™ sheath (p = 0.035), especially in the right inferior PV (p = 0.009). The RF time per lesion was, on average, 12% (1.4 seconds) shorter when using the SureFlex™ sheath than the Agilis™ sheath (p < 0.05). The choice of steerable sheath may affect both catheter stability and lesion quality, especially in the right PVs.

Paroxysmal and persistent atrial fibrillation ablation outcomes with the pulmonary vein ablation catheter GOLD duty-cycled phased radiofrequency ablation catheter: quality of life and 12-month efficacy results from the GOLD Atrial Fibrillation Registry

Aims

The GOLD AF Registry has been designed to prospectively assess the population, indications, and outcomes using second-generation phased radiofrequency (RF) ablation (pulmonary vein ablation catheter GOLD) in a global examination of standard-of-care use for the treatment of paroxysmal and persistent atrial fibrillation (AF).

Methods and results

GOLD AF (NCT02433613) is a prospective, observational, multi-centre registry designed to characterize efficacy and safety of phased RF ablation in patients with AF. The primary endpoint was freedom from AF recurrence at 12-month follow-up after a 90-day blanking period. Ancillary objectives include safety, procedural efficiency, and quality of life (QoL). The QoL assessment using the Atrial Fibrillation Effect on QualiTy-of-Life (AFEQT) and the European Heart Rhythm Association (EHRA) Score of AF-related symptoms was collected at baseline and 12 months. In total, 1054 patients were included in this analysis (age 60.6, 67.6% male, 26.5% PersAF). Kaplan–Meier estimate of freedom from AF recurrence was 77.7% at 12 months. Peri-procedural device or procedure-related complications were observed in 26 (2.5%) patients, with a low stroke rate of 0.3%. One-year post-ablation, the EHRA AF Symptom score decreased in 68% of patients. The AFEQT score improvement was observed in 88.4% and 90.4% of patients who completed the questionnaire in-person or interviewed by phone at 12 month follow-up, respectively.

Conclusion

Phased RF ablation for the treatment of paroxysmal and persistent AF demonstrated a 77.7% freedom from AF recurrence at 12 months in addition to a significant reduction in arrhythmia symptoms and clinically meaningful improved QoL. Low peri-procedural complication rate of <3% was reported.

Evaluation of a simple technique aiming at optimizing point-by-point isolation of the left pulmonary veins: a randomized study

Aims

We sought to evaluate the efficacy and the safety of a simple technique for stabilizing the ablation catheter during anterior pulmonary vein (PV) encirclement in patients ablated for paroxysmal atrial fibrillation. This consisted of bending the ablation catheter in the left atrium, creating a loop that was cautiously advanced together with the long sheath at the ostium and then within the left superior PV. The curve was then progressively released to reach a stable contact with the anterior part of the left PVs.

Methods and results

Eighty consecutive patients (age 64 ± 11 years, left atrial diameter 43 ± 8 mm) undergoing ‘CLOSE’-guided PV isolation were prospectively randomized into two groups depending on whether the loop technique was used or not. When using the loop technique, the encirclement of the left PVs was shorter [20 min (interquartile range, IQR 17–24) vs. 26 min (IQR 18–33), P < 0.01] with a high rate of first pass isolation [(100%) vs. (97%), P = 0.9] and adenosine proof isolation [(93%) vs. (95%), P = 0.67]. Most specifically, at the anterior part of the left PVs, there were less dislocations [0 (IQR 0–0) vs. 1 (IQR 0–4), P < 0.001], radiofrequency duration was shorter (272 ± 85 s vs. 378 ± 122 s, P < 0.001), force-time integral was higher [524 gs (IQR 427–687) vs. 398 gs (IQR 354–451), P < 0.001], average contact force was higher [20 g (IQR 13–27) vs. 11g (IQR 9–16), P < 0.001], and impedance drop was higher [12 Ω (IQR 9–19) vs. 10 Ω (IQR 7–14), P < 0.001].

Conclusion

This study describes a simple technique to facilitate catheter stability at the anterior part of the left PVs, resulting in more efficient left PV encirclement without compromising safety.

Pulmonary vein isolation using multi-electrode radiofrequency vs conventional point-by-point radiofrequency ablation: A meta-analysis of randomized and non-randomized studies

Aims

Pulmonary vein isolation is effective in reducing atrial fibrillation (AF) episodes. Previous studies suggest single-shot techniques are effective and safe for this purpose. Procedural and clinical outcomes were compared between multi-electrode and point-by-point radiofrequency ablations by performing a meta-analysis of all randomized and non-randomized studies.

Methods and results

Systematic reviews of MEDLINE and Cochrane Library databases were performed. Studies comparing procedural (procedure and fluoroscopy times) and clinical (AF recurrence) outcomes were included in the meta-analysis. A total of 13 clinical studies (5 randomized and 8 non-randomized) including 2152 patients met the inclusion criteria. In patients underwent multi-electrode ablation, there were significant reductions in both total procedure and fluoroscopy times, compared with point-by-point ablation (mean difference = −34.3 min [95% CI (−50.1 to −18.5)], p < 0.001 and mean difference = −7.1 min [95% CI (−12.0 to −2.2)], p < 0.01, respectively). These significances also continued in patients with paroxysmal AF. No such difference was observed in regard to AF recurrence between the 2 ablation strategies (RR = 0.90 [95% CI (0.80–1.01)], p = 0.066). This insignificance was also observed in patients with paroxysmal AF.

Conclusions

In a heterogeneous AF population, multi-electrode ablation is as effective as point-by-point ablation, with better procedural and fluoroscopy durations.

A 5-year clinical follow-up after duty-cycled phased RF ablation of paroxysmal atrial fibrillation

PURPOSE

Catheter radiofrequency ablation (RFA) is an effective treatment for symptomatic paroxysmal atrial fibrillation (AF). It has been demonstrated that the multielectrode pulmonary vein ablation catheter (PVAC) has favourable outcomes at 6-12 months post-ablation, but there are only few studies with a long-term follow-up.

METHODS

We retrospectively reviewed 77 consecutive PVAC procedures in our centre, from November 2007 to December 2012. RFA was attempted in patients with symptomatic paroxysmal AF (mean age 58.7 ± 9.8 years, 50 men (64.9 %). The ablation strategy consisted of circumferential pulmonary vein isolation (CPVI) with the PVAC system. A questionnaire was used over the follow-up period to assess the efficacy of AF ablation. Success was defined as freedom from AF/atrial flutter or atrial arrhythmia for a period ranging from 3 to 12 months or more.

RESULTS

Seventy-seven patients were included with paroxysmal AF. The mean duration of the procedure was 99.6 ± 26 min and fluoroscopy time 19.4 ± 6.8 min. Time of RFA was 22.4 ± 5.8 min. Acute complication rate was 10.4 % (the most frequent was vascular injury for 6 patients 7.8 %, 1 patient presented sepsis (1.3 %), 1 patient presented transient ischemic stroke). After a single procedure at a mean FU of 55 ± 11 months, 54/77 (70.1 %) patients were free of symptomatic AF.

CONCLUSIONS

These long-term results suggest that PVAC is an efficient system for CPVI of symptomatic paroxysmal AF.