Durable Pulmonary Vein Isolation Research Articles

P811Right versus left durable pulmonary vein isolation using the first and second generation cryoballoons: comparative results from a French multicenter study

P811Right versus left durable pulmonary vein isolation using the first and second generation cryoballoons: comparative results from a French multicenter study

Temperature-Controlled Radiofrequency Ablation for Pulmonary Vein Isolation in Patients With Atrial Fibrillation

BackgroundSaline irrigation improved the safety of radiofrequency (RF) ablation, but the thermal feedback for energy titration is absent. ObjectivesTo allow temperature-controlled irrigated ablation, a novel irrigated RF catheter was designed with a diamond-embedded tip (for rapid cooling) and 6 surface thermocouples to reflect tissue temperature. High-resolution electrograms (EGMs) from the split-tip electrode allowed rapid lesion assessment. The authors evaluated the preclinical and clinical performance of this catheter for pulmonary vein (PV) isolation. MethodsUsing the DiamondTemp (DT) catheter, pigs (n = 6) underwent discrete atrial ablation in a temperature control mode (60°C/50 W) until there was ∼80% EGM amplitude reduction. In a single-center clinical feasibility study, 35 patients underwent PV isolation with the DT catheter (study group); patients were planned for PV remapping after 3 months, regardless of symptomatology. A control group included 35 patients who underwent PV isolation with a standard force-sensing catheter. ResultsPorcine lesion histology revealed transmurality in 51 of 55 lesions (92.7%). In patients, all PVs were successfully isolated; no char or thrombus formation was observed. Compared with the control group, the study cohort had shorter mean RF application duration (26.3 ± 5.2 min vs. 89.2 ± 27.2 min; p < 0.001), shorter mean fluoroscopic time (11.2 ± 8.5 min vs. 19.5 ± 6.8 min; p < 0.001), and lower acute dormant PV reconduction (0 of 35 vs. 5 of 35; p = 0.024). At 3 months, 23 patients underwent remapping: 39 of 46 PV pairs (84.8%) remained durably isolated in 17 of these patients (73.9%). ConclusionsThis first-in-human series demonstrated that temperature-controlled irrigated ablation produced rapid, efficient, and durable PV isolation. (ACT DiamondTemp Temperature-Controlled and Contact Sensing RF Ablation Clinical Trial for Atrial Fibrillation [TRAC-AF]; NCT02821351)

Therapeutic Approaches to AtrialFibrillation Ablation TargetingAtrialFibrosis.

Atrial fibrosis is the fundamental histopathologic finding in atrial fibrillation (AF) patients and an important predictor of ablation failure beyond pulmonary vein isolation. There is wide variation in the extent and localization of left atrial fibrosis in patients with paroxysmal and nonparoxysmal AF. Box isolation of fibrotic areas is an effective rhythm control concept in patients with paroxysmal AF despite durable pulmonary vein isolation, and this strategy has recently been implemented successfully in initial AF ablation procedures in addition to pulmonary vein isolation for patients with nonparoxysmal AF. Incontrast, the time for "empirical" lines or other nonindividualized substrate modifications seems over.

Acute efficacy, safety, and long-term clinical outcomes using the second-generation cryoballoon for pulmonary vein isolation in patients with a left common pulmonary vein: A multicenter study

Second-generation cryoballoon (CB2)-based pulmonary vein isolation (PVI) has demonstrated encouraging clinical results in the treatment of paroxysmal (PAF) and persistent atrial fibrillation (PersAF). However, the CB2 features a maximal diameter of 28 mm, and its adaptability to anatomic variations of the pulmonary veins (PVs) might be challenging. The purpose of this study was to assess the acute efficacy, safety, and long-term clinical results of CB2-based PVI in patients with a left common pulmonary vein (LCPV). Six hundred seventy consecutive patients underwent CB2-based PVI in 3 electrophysiology centers. In 74 patients (11%), an LCPV was identified (LCPV group). The data were compared to those from matched patients (n = 74) with normal PV anatomy and comparable baseline characteristics (control group). An antral occlusion of the complete LCPV ostium was feasible in 50% of patients in the LCPV group. If an antral occlusion could not be obtained, a sequential isolation of the first superior and inferior branches was applied. All 74 LCPVs were successfully isolated. A total of 64% patients (LCPV group) and 66% patients (control group) remained in sinus rhythm after mean follow-up of 1.9 ± 0.9 years (P=.820). In 18 of 26 patients (69%) with atrial tachyarrhythmia recurrence, a repeat procedure using radiofrequency energy was performed, and a total of 56% LCPVs were found to be persistently isolated (control group: 61% of left-sided PVs, P = .801). Patients with an LCPV undergoing CB2-based PVI demonstrate a high acute success rate. Comparable results with regard to clinical success and durability of PVI were shown when comparing patients of the LCPV group and the control group.

Pulmonary Vein Isolation Lesion Set Assessment During Radiofrequency Catheter Ablation for Atrial Fibrillation.

This article reviews methods for lesion set assessment during radiofrequency catheter ablation for atrial fibrillation (AF). Pulmonary vein isolation (PVI) is the foundation for AF ablation, but PV reconnection can lead to treatment failure. Testing for entrance block can help confirm PVI, although complex electrograms that consist of both near- and far-field potentials may make assessment of entrance block challenging. Differential pacing maneuvers can help appropriately identify PV potentials. After entrance block has been achieved, pacing within the PVs to demonstrate capture of PV musculature with exit block may also help to confirm completeness of lesion sets for PVI. Employing a waiting period of at least 30 min or administering adenosine or isoproterenol can reveal dormant conduction, warranting adjunctive ablation. Additional techniques to confirm durable PVI include testing the ablation lines for excitability with high amplitude pacing, and automated waveform analysis of local electrogram morphology. Newer techniques like real-time magnetic resonance imaging and acoustic radiation force impulse elastography may have a role in testing the completeness of lesion sets in the future.

The relationship between oesophageal heating during left atrial posterior wall ablation and the durability of pulmonary vein isolation.

During ablation of the posterior wall (PW), luminal oesophageal temperature elevation (OTE) prompts attenuation of radiofrequency (RF) energy delivery to minimize oesophageal injury. This strategy on lesion efficacy is unknown. The goal of this study was to analyse the relationship between OTE and pulmonary vein reconnection (PVR). During the index antral pulmonary vein (PV) isolation procedure with an irrigated RF ablation catheter, OTE was detected with a multisensor oesophageal temperature probe. Posterior wall ablation did not exceed 25 W and was terminated when the temperature was ≥38.5°C. Patients undergoing redo procedures (n = 142) were studied for PW sites of PVR along 4 segments: left and right superior, and left and right inferior. Pulmonary vein reconnections had occurred in 51 of the 142 patients (36%), in 58 of 284 PV pairs (20%). Among these 58 reconnected pairs, 83% (n = 48) were along the PW. Oesophageal temperature elevation had occurred in 30 patients (59%). No difference in characteristics was seen between the patients with OTE (n = 30) and those without (n = 21). For superior segments, there was no interaction between the presence or absence of OTE and PVR. For inferior segments, there were more PVRs in the group with OTE: for the right-inferior segment, the PVR rate was 72% for OTE cases vs. 42% without (P = 0.04), and for the left-inferior segment, the PVR rate was 44% for OTE cases vs. 22.9% without (P = 0.12). Pulmonary vein reconnections are predominantly posteriorly located. Along the right- and left-inferior PW segments, there was an association with elevated oesophageal temperature during the index procedure.

What Is the Acute Antral Lesion Size After Pulmonary Vein Isolation Using Different Balloon Ablation Technologies?

Clinical outcome after pulmonary vein isolation (PVI) may be linked to both durability of PVI and the antral lesion size. Data on balloon-guided technologies are scarce. We investigated the size of the isolated surface area (ISA) acutely after PVI achieved by cryoballoon (CB) or laser balloon (LB), both using voltage mapping.Methods and Results:In 40 patients (73% male, mean age 66±9 years), a bipolar voltage map before and after PVI in sinus rhythm was acquired to delineate the isolated antral surface area (IASA, contiguous area of low voltage <0.5 mV) and the ISA (relative size of the low-voltage area in relation to the whole antral surface area including the posterior wall). IASA (CB: 57±14 cm2vs. LB: 42±15 cm2; P=0.002) as well as ISA (65±8% vs. 54±10%; P=0.001) were significantly larger in the CB than in the LB group. No periprocedural complications occurred. During a mean follow-up of 326±142 days, 4/20 and 5/20 patients experienced an AF/AT recurrence in the CB and LB groups, respectively. No differences in clinical outcome were observed between patients with a large (≥55%) or small (<55%) ISA. Balloon-guided PVI is associated with antral lesion formation. CB-guided PVI is associated with the largest ISA as compared with LB procedures. ISA size did not correlate with clinical outcome after a single procedure in the present study population.

Latest technologies and techniques to improve pulmonary vein isolation

Pulmonary vein isolation (PVI) is the established cornerstone in catheter ablation for atrial fibrillation (AF). The traditional point-to-point ablation by focal radiofrequency (RF) catheter to achieve PVI was technically challenging, and the outcome remained suboptimal despite advancement in three-dimensional electroanatomical mapping systems and steerable sheaths. Different catheter designs including contact force, balloon-based catheters with other energy sources (cryothermal and laser energies), and circular RF catheters have been developed to make the ablation procedure more user-friendly and PVI more durable. Adjunctive techniques including detection of dormant conduction by adenosine triphosphate injection and pace-capture-guided ablation have also been studied to improve the durability of PVI and thus reduce the AF recurrence rate.

Paroxysmal atrial fibrillation ablation: Achieving permanent pulmonary vein isolation by point-by-point radiofrequency lesions.

Pulmonary vein isolation by point-by-point radiofrequency catheter ablation constitutes the cornerstone of catheter ablation strategies for the treatment of atrial fibrillation. However, despite advances in pulmonary vein isolation ablation strategies, long-term success rates after ablation remain suboptimal, which highlights the need to develop techniques to achieve more durable lesions. Strategies proposed to improve the durability of pulmonary vein isolation can be divided into two groups: Those addressed to improving the quality of the lesion and those that optimize the detection of acute PV reconnection during the ablation procedure. This manuscript reviews the role and potential benefits of these techniques according to current clinical evidence.

Peri-procedural Corticosteroid Use in Improving Outcomes Following Atrial Fibrillation Ablation: Back to Square One?

Bilateral pulmonary vein (PV) isolation by catheter ablation has become an established therapy for highly symptomatic, drug refractory, paroxysmal atrial fibrillation (AF) (1, 2). The efficacy of pulmonary vein isolation has improved over the years through refinement of procedural technique as well as improved ablation technology involving irrigated ablation, contact force sensing, and “single shot” ablation techniques such as cryo, laser, and multielectrode ablation catheters(1, 3-5). However, durable pulmonary vein isolation has remained a significant challenge with increasing rates of pulmonary vein reconnection noted during long-term follow-up (6, 7). Similarly, acute reconnections as well as early recurrences during the blanking period have been associated with reduced freedom from AF during follow-up(8). With radiofrequency (RF) ablation, acute inflammation from the ablation lesions itself have been thought to have a major role in AF recurrences during the immediate peri-procedural period (9).

Automated Ablation Annotation Algorithm Reduces Re-conduction of Isolated Pulmonary Vein and Improves Outcome After Catheter Ablation for Atrial Fibrillation.

Durable pulmonary vein isolation (PVI) is critical in reducing recurrence after radiofrequency catheter ablation for atrial fibrillation (AF). The VISITAG Module, an automatic annotation system that takes account of catheter stability and contact force (CF), might be useful in accomplishing this.Methods and Results:In 49 patients undergoing VISITAG-guided AF ablation (group A), we set the following automatic annotation criteria: catheter stability range of motion ≤1.5 mm, duration ≥5 s, CF ≥5 g, time ≥25% and tag diameter at 6 mm. We used ablation >20 s and force-time integral >150 gs at each site, then moved to the next site where a new tag appeared that overlapped with the former tag. Results and outcome were retrospectively compared for 42 consecutive patients undergoing CF-guided AF ablation without this algorithm (group B). Successful PVI at completion of the initial anatomical line was more frequent in group A than B (66.3% vs. 36.9%, P=0.0006) while spontaneous PV reconnection was less frequent (14.2% vs. 30.9%, P=0.0014) and procedure time was shorter (138±35 min vs. 180±44 min, P<0.001). One-year success rate off anti-arrhythmic drugs was higher in group A (91.8% vs. 69.1%, log rank P=0.0058). An automated annotation algorithm with an optimal setting reduced acute resumption of left atrium-PV conduction, shortened procedure time, and improved AF ablation outcome.

Increasing the Single-Procedure Success Rate of Pulmonary Vein Isolation.

To improve the single-procedural success and long-term outcomes of catheter ablation techniques for AF, there is a need for durable, contiguous and transmural lesions encircling the pulmonary veins (PV). Measurement of contact force (CF) between the catheter tip and the target tissue can optimise ablation procedures. A new approach to obtain single-procedure durable PV isolation (PVI) using the latest CF technology combined with the CARTO VISITAG™ Module with Ablation Index (Biosense Webster) has been shown in small studies to almost eliminate recurrence of paroxysmal AF at 1-year follow up and to make PVI procedures more reproducible. The use of a standardised workflow is expected to increase the reproducibility of results and to increase the efficiency of PVI procedures.

Mechanistic Insights Into Durable Pulmonary Vein Isolation Achieved by Second-Generation Cryoballoon Ablation.

The mechanism explaining the efficacy of cryoballoon ablation (CBA) for atrial fibrillation has not been clarified. We compared lesion characteristics between patients in whom pulmonary vein isolation (PVI) was performed by CBA (n=56) and those by contact force (CF)-based RF ablation (n=56). We evaluated the 3-dimensional PV morphology before and after cryoballoon inflation. After PVI, a 3D left atrial voltage map was created. Pacing (10 mA and 2 ms) was performed within the low voltage area from the ablation line, and electrically unexcitable ablated tissue was identified. ATP-provoked dormant conduction after PVI occurred in 9 of the 224 (4%) PVs in the CBA group and in 13 of the 224 (6%) PVs in the CF group (P=0.3935). The inflated balloon stretched the PV from the original PV ostial surface by 7.1±3.5 mm, but at sites with (vs, sites without) residual PV potential/dormant conduction, the extent of the PV distension was reduced (4.0±4.0 mm vs. 7.2±3.4 mm, P<0.0001). The unexcitable ablated tissue around the PVs was significantly wider in CB patients than in CF patients (16.7±5.1 mm vs. 5.3±2.3 mm, P<0.0001). Use of the cryoballoon significantly distends the PV. Without this extensive distention, PVI may not be successful. CBA seems to yield wide unexcitable ablation zones. These factors seem to explain the durability of CBA lesions.

Second-generation cryoballoon ablation without the use of real-time recordings: A novel strategy based on a temperature-guided approach to ablation

The achievement of -40°C within the first 60 seconds during cryoenergy applications has proven to independently predict durable pulmonary vein (PV) isolation in the setting of second-generation cryoballoon (CB-A; Medtronic, Minneapolis, MN) ablation. We sought to evaluate a strategy based on the attainment of the specific parameter of -40°C within the first 60 seconds during cryoenergy applications in the setting of CB-A ablation without the use of an inner lumen mapping catheter (Achieve, Medtronic) for the visualization of real-time recordings. A total of 52 patients having undergone CB ablation for paroxysmal atrial fibrillation (AF) between 1 February 2015 and 30 June 2015 who underwent a temperature-guided approach based on achieving -40°C within 60 seconds without real-time recordings (wire group) were compared with a cohort of 52 propensity score-matched patients having undergone CB ablation performed with an inner lumen mapping catheter (Achieve group). All PVs were checked for electrical isolation at the end of the procedure with a circular mapping catheter in the wire group. Electrical isolation could be obtained in all patients in the Achieve group and in 99% of PVs in the wire group. Freedom from AF without antiarrhythmic drugs at a mean follow-up of 12.4 ± 3.0 months did not significantly differ between both groups (85% vs 88%, respectively; P = .56). A temperature-guided approach based on achieving -40°C within 60 seconds is effective in producing PV isolation and affords freedom from AF at 12-month follow-up in 85% of patients affected by paroxysmal AF after a 3-month blanking period.

Sites With Small Impedance Decrease During Catheter Ablation for Atrial Fibrillation Are Associated With Recovery of Pulmonary Vein Conduction.

To correlate impedance decrease during atrial fibrillation (AF) ablation with lesion durability and PV conduction recovery demonstrated during redo procedures. Markers of successful ablation beyond acute conduction block are needed to improve durability of pulmonary vein (PV) isolation (PVI). Local impedance decrease resulting from ablation is a real-time marker of tissue heating and is correlated with lesion creation. Impedance changes associated with point-by-point radiofrequency ablation in the PV antra were recorded during 167 consecutive first-time AF ablations. During clinically indicated redo procedures, sites of recovered PV conduction were identified, and were correlated with the impedance change achieved during ablation at these locations during the initial procedure. Redo procedures were performed in 28 patients, in whom 19 sites of recovered PV conduction were documented. Most sites of PV reconnection (58%) occurred along the posterior PV antra. Ablation resulting in impedance decrease <10 ohms during the initial procedure was present in 89% (17/19) of sites with conduction recovery. Regions with adjacent ablation resulting in impedance decrease <10 ohms were associated with a higher rate of conduction recovery (37% vs. 1.5%, P < 0.001). Likewise, patients with PV conduction recovery demonstrated during redo procedure (Group 1) had larger regions where ablation resulted in <10 ohm impedance decrease than patients without PV conduction recovery (Group 2) (21.9 ± 15.5 mm vs. 11.5 ± 2.1 mm, P < 0.01). Recovered PV conduction occurs predominantly in regions where adjacent ablation applications result in impedance decreases <10 ohms. Impedance-guided ablation strategies may improve durability of PVI.

Update on Atrial Fibrillation

Atrial fibrillation (AF), the most prevalent cardiac arrhythmia, is categorized into 4 different groups on the basis of the duration of the arrhythmia episodes. If AF terminates spontaneously or with intervention within 7 days from onset, it is paroxysmal AF; AF of more than 7 days in duration is persistent AF; continuous AF of more than one year's duration is longstanding persistent AF; and permanent AF is the condition that ensues when the patient and his or her physician mutually decide not to pursue the restoration or maintenance of sinus rhythm by any means.1

Recurrent atrial arrhythmias in the setting of chronic pulmonary vein isolation

Atrial arrhythmias may still occur in patients after durable pulmonary vein isolation (PVI). The purpose of this study was to examine the incidence of patients undergoing ablation for recurrent arrhythmia despite chronic PVI and their clinical outcomes. Patients undergoing repeat left atrial ablation procedures were selected from a prospective registry. From this population, we identified patients with chronic PVI. Clinical characteristics, ablation strategies, and outcomes were analyzed. Between January 2003 and December 2013, 1045 patients underwent 1298 repeat left atrial procedures. Of these, 900 patients had atrial fibrillation (AF) and 145 had atrial flutter (AFL)/atrial tachycardia (AT). Fifty-two patients (5.0%; 27 with AF and 25 with AFL/AT) had chronic PVI and were included in the study. Patients were followed for 19.7 ± 5.6 months. In patients with AF, 11 (41%) had a non-PV trigger identified. Ablation strategies included non-PV trigger ablation (n = 11), empiric trigger-site ablation (n = 3), provoked arrhythmia ablation (n = 9), complex fractionated atrial electrogram ablation (n = 2), and linear ablation (n = 2). During follow-up, 9 (33%) had no recurrence, 7 (26%) had rare AF (≤2 episodes during follow-up ≥1 year), and 11 (41%) had AF recurrence. In patients with AFL/AT, 12 (48%) had no recurrence, 4 (16%) had rare recurrence (≤2 episodes during follow-up ≥1 year), and 9 (36%) had recurrence. In patients with PVI undergoing a repeat procedure during the time period studied, only a small portion had chronic PVI. A strategy of targeting non-PV triggers for AF and linear/focal ablation for AFL/AT may achieve long-term arrhythmia control in the majority of patients.

Durability of cryothermal pulmonary vein isolation — Creating contiguous lesions is necessary for persistent isolation

BackgroundElectrical reconnections after pulmonary vein isolation (PVI) are common in catheter ablation. This study aimed to evaluate the impact of the ablation method on the durability of cryothermal PVI. MethodsOne hundred thirty-two consecutive paroxysmal atrial fibrillation patients undergoing cryothermal PVI were enrolled. PVI was performed with one 28-mm second-generation balloon using 3-minute freeze techniques, and touch-up lesions were created by focal cryothermal applications. ResultsOut of 520 PVs, 503 (96.7%) were isolated using exclusively cryoballoons, and 17 required additional focal ablation. Adenosine testing was performed in 111 patients for 439 PVs including 427 isolated with cryoballoons and 12 isolated by focal ablation. The incidence of dormant conduction was significantly higher in PVs isolated by focal ablation than by cryoballoons (4/12 vs. 3/427 PVs, p<0.0001). All latent conduction was successfully eliminated by additional cryoapplications. In 36 patients, 142 PVs were re-evaluated during repeat procedures a median of 6 [4.3–9.0] months after the initial procedure. Late reconnections were detected in 32 (22.5%) PVs. The incidence of late reconnections was significantly higher in PVs isolated by focal ablation than by cryoballoons (5/6 vs. 27/136 PVs, p=0.0003). Among the PVs requiring touch-up ablation, both the acute dormant conduction and late reconnection sites were identical to sites requiring touch-up ablation. ConclusionsThe incidence of both acute latent and late PV reconnections was significantly higher when PVI was achieved by focal cryoablation than by cryoballoon ablation despite using the same energy source. These data suggest that creating contiguous lesions is essential for achieving a durable PVI.

176-17: First-in-Man Experience and Procedural Efficacy of Pulmonary Vein Isolation using the Third-Generation Cryoballoon

Background: The second-generation cryoballoon (CB2) provides effective and durable pulmonary vein isolation (PVI) associated with encouraging clinical outcome data. The novel third-generation cryoballoon (CB3) incorporates a 40% shorter distal tip. This design change may translate into an increased rate of PVI real-time signal recording, facilitating an individualized ablation strategy using the time to effect (TTE). Methods and results: Thirty consecutive patients with paroxysmal or short-standing persistent atrial fibrillation (AF) underwent CB3-based PVI and were compared to 30 patients treated with the CB2. Individual freeze-cycle duration was set to TTE + 120 seconds for both groups. A total of 118 (CB3) and 119 (CB2) pulmonary veins (PV) were identified and all PVs successfully isolated utilizing the CB3 and CB2, respectively. The real-time PVI visualization rate was 74% (CB3) and 40% (CB2; p = 0.001) and the mean freeze-cycle duration 204 ± 88sec. (CB3) and 215 ± 90sec. (CB2; p = 0.15), respectively. Per individual PV, a shorter mean freeze-duration was found for the CB3 and the right superior PVs (188 ± 92sec vs. 211 ± 124sec., p = 0.04) and right inferior PVs (192 ± 75sec vs. 200 ± 37sec., p = 0.02). No differences were found for the left-sided PVs. Conclusions: A higher rate of real-time electrical PV recordings are seen using the novel CB3 as compared to CB2, which may facilitate an individualized ablation strategy using the TTE.

Pulmonary vein isolation in the treatment of atrial fibrillation

Pulmonary vein isolation in the treatment of atrial fibrillation Saurabh Kumar, Gregory F Michaud Cardiac Arrhythmia Service, Cardiovascular Division, Brigham and Women&#39;s Hospital, Boston, MA, USA Abstract: Atrial fibrillation (AF) is the commonest arrhythmia in humans and is associated with marked reduction in quality of life and an elevated thromboembolic risk. Paroxysmal, persistent, and permanent forms of AF have been recognized. Whilst antiarrhythmic drugs are considered as first-line therapy, the role of catheter ablation is increasing due to its superior efficacy in terms of quality of life and reduction in AF burden. The central paradigm for catheter ablation of AF is that triggers for AF are located near and within the pulmonary veins (PVs), and electrical isolation of the PVs from the left atrium forms the cornerstone of most catheter ablation strategies. Whilst paroxysmal form is generally trigger dependent, persistent and permanent forms are associated with variable interaction between triggers and &quot;substrate&quot; comprised of atrial and PV electrical and structural remodeling. Nevertheless, isolation of the PVs still forms a critical component of catheter ablation strategies, regardless of AF type. Procedural efficacy, however, is limited by PV conduction recovery. This is likely due to deficiencies in ablation tools or limitations of intraprocedural assessment of lesion efficacy. Careful attention to surrogates of tissue heating, such as impedance decrease and electrogram morphology changes, along with advances in catheter technology like contact force catheters may improve rates of durable PV isolation and single-procedural success. This review discusses the mechanism of paroxysmal AF with particular focus on the role of the PVs in AF initiation and PV isolation in the management of AF. Keywords: contact force, lesion transmurality, radiofrequency catheter ablation, paroxysmal atrial fibrillation, electrophysiology, AF