Pulmonary Vein Conduction Research Articles

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Sinoatrial node electrical activity modulates pulmonary vein arrhythmogenesis

BackgroundSinoatrial node (SAN) dysfunction increases the occurrences of atrial fibrillation (AF). The pulmonary veins (PVs) play a critical role in the pathophysiology of AF. The purpose of this study was to evaluate whether SAN electrical activity can modulate PV arrhythmogenesis. MethodsConventional microelectrodes and multi-electrode array system were used to simultaneously record the electrical activity and conduction properties of rabbit SAN and PV tissue preparations with and without SAN–PV interruptions before and after perfusion with Anemonia sulcata toxin (ATX)-II (100nM) or isoproterenol (1μM). ResultsATX-II significantly increased PV beating rates, which overdrove SAN electrical activity with the occurrences of PV burst firings in 5 (56%) of 9 tissue preparations, and induced SAN–PV conduction block in 6 (67%) of 9 preparations. After SAN–PV disconnection, ATX-II induced burst firing and early afterdepolarizations in 8 (89%) of 9 PVs. Moreover, the multi-electrode array found that ATX-II reversed the electrical conduction between the SAN and PV with an increase in electrical activity from 1.8±0.6 to 2.9±0.6Hz (P<0.05) in SAN–PV preparations (n=7). In contrast, isoproterenol did not reverse electrical conduction between the SAN and PV with an increase in electrical activity from 1.8±0.2 to 3.0±0.3Hz (P<0.005) in SAN–PV preparations (n=7). ConclusionsSAN electrical activity modulates PV arrhythmogenesis. SAN–PV conduction blocks can increase PV arrhythmogenesis.

Incidence of pulmonary vein conduction recovery in patients without clinical recurrence after ablation of paroxysmal atrial fibrillation: Mechanistic implications

Pulmonary vein (PV) isolation has become the mainstay acute procedural end point for paroxysmal atrial fibrillation (AF) ablation. To examine the incidence of conduction recovery in the PVs in patients without clinical recurrence of AF after paroxysmal AF ablation. From August 2008 to March 2011, 392 patients with drug-refractory PAF underwent catheter ablation in our center, a wide area circumferential ablation approach guided with a circular mapping catheter was performed with the intended endpoint of entrance block in all PVs. 276 (70.4%) of them were free from recurrence at one year follow-up, and 32 of them were enrolled to assess the incidence of PV reconnection. Forty-three patients with clinical recurrence after ablation were analyzed for comparison. The regions of gap were mapped and characterized in all of the reconnected PVs. Among patients without recurrence, recovery of PV conduction was observed in 29 of 32 (90.6%) patients: 10/32 (31.2%) reconnection in 4 veins, 7/32 (21.9%) in 3 veins, 10/32 (31.2%) in 2 veins, and 2/32 (6.2%) in 1 vein. No anatomic propensity was seen because reconnection was evenly distributed throughout all veins (left superior pulmonary vein 21, left inferior pulmonary vein 20, right superior pulmonary vein 19, and right inferior pulmonary vein 23). When compared to patients with recurrence, no significant differences were seen in the proportion of patients with reconnection (P = 1.0) or in left atrium-PV intervals (73.4 ± 43.3 ms vs 61.9 ± 31.8 ms; P > .05). A high incidence of PV reconnection was similarly observed in patients with and without recurrence of AF, suggesting that sustained PV isolation may not be required for freedom from clinical recurrence of AF.

Radiofrequency ablation annotation algorithm reduces the incidence of linear gaps and reconnection after pulmonary vein isolation

A common mechanism of atrial fibrillation recurrence after catheter ablation is resumption of pulmonary vein (PV) conduction due to gaps in the ablation line. These gaps may go unrecognized owing to inadequate ablation lesion annotation. To examine the utility of an automated radiofrequency (RF) ablation annotation algorithm for the detection and treatment of ablation gaps during pulmonary vein isolation (PVI). Eighty-four patients with paroxysmal atrial fibrillation underwent PVI. In 42 patients (group A), RF ablation was guided by an automated algorithm with predefined criteria of catheter stability range of motion ≤2 mm and impedance decrease ≥5% for individual ablation applications. In 42 control patients (group B), ablation was guided by the operator. Successful PVI, conduction recovery, and dormant conduction with adenosine were compared between the groups. Ipsilateral PVI at the completion of the initial anatomical line was obtained in 90.5% of group A patients (76 of 84 ipsilateral pairs of PVs) but only in 66.7% of group B patients (56 of 84 ipsilateral pairs of PVs) (P = .0001). Ineffective energy delivery was detected in 23% (1005 of 4362) of group A applications but only in 9% (368 of 4071) of group B applications (P = .0001). The frequency of conduction recovery was lower in group A than in group B (5.9% vs 25%; P = .001). Arrhythmia-free survival at 6 months trended higher in group A (38 of 42 [90%]) than in group B (32 of 42 [76%]; P = .07). Automated ablation lesion annotation provides real-time feedback of RF ablation that may improve effective energy delivery.

Acute pulmonary vein reconnection is a predictor of atrial fibrillation recurrence following pulmonary vein isolation

Arrhythmia recurrence following pulmonary vein isolation (PVI) occurs predominantly due to the reconnection of previously isolated pulmonary veins (PVs). The prognostic implications of detection and treatment of acute PV reconnection are not well understood. We aim to examine the prognostic significance of acute PV reconnection on arrhythmia recurrence at 1 year following PVI. This prospective study included 44 patients (22 men, 60 ± 7 years) who underwent index PVI procedure for treatment of atrial fibrillation (AF). Acute PV reconnection and/or dormant PV conduction were assessed sequentially in response to a 30-min waiting period, intravenous isoproterenol infusion and/or adenosine. All cases of acute PV reconnection and/or dormant conduction were successfully targeted with additional ablation. Freedom from AF at 1 year was 75 % (83.3 % in paroxysmal and 65 % in persistent AF, p = ns). Acute PV reconnection and/or dormant conduction were evident in 16 of 44 patients (36.3 %). AF recurrence was documented in eight of 16 patients with, but only in three of 28 patients without acute reconnection (p = 0.009). Three patients underwent a redo procedure, all from the group of patients with acute PV reconnection. In a multivariate model, acute PV reconnection was a strong independent predictor of arrhythmia recurrence (hazards ratio [HR], 6.36; 95 % confidence interval [CI], 1.12-31.6). Identification of acute PV reconnection, even when successfully targeted, is a strong predictor of arrhythmia recurrence following PVI.

Origin and Ablation of the Adenosine Triphosphate Induced Atrial Fibrillation After Circumferential Pulmonary Vein Isolation: Effects on Procedural Success Rate

Adenosine triphosphate (ATP) has been used to provoke dormant pulmonary vein (PV) conduction after circumferential PV isolation (CPVI). However, there have been no systematic studies examining the incidence and the mechanism of ATP-induced atrial fibrillation (AF) following CPVI in paroxysmal AF. In this study, we explore the mechanism of ATP-induced AF and assess the feasibility of eliminating this response by additional radiofrequency (RF) ablation. A total of 300 consecutive patients with paroxysmal AF underwent CPVI. After all PVs were isolated, intravenous ATP (40 mg) was administered during an intravenous isoproterenol (ISP) infusion (5 μg/min). AF was reproducibly induced by ATP in 39 patients. Non-PV foci were confirmed and located in 29 of these patients at the onset of AF, including 27 foci in the superior vena cava (SVC), 1 focus in the crista terminalis, and 1 focus near the antrum of the PV. In all these cases, ATP-induced AF was eliminated after the non-PV foci were successfully ablated. For the other 10 patients, the foci triggering AF could not be confirmed or located due to the transient effect of ATP, thus no further ablation was performed. After a mean follow-up period of 18.7 ± 6.4 (8-24) months, the success rate in the ATP-induced AF group was not significantly different compared with the conventional treatment group who did not exhibit ATP-induced AF (76.9% vs 67.3%; P = 0.25). But in the subgroup of which the ATP-induced AF could be eliminated by additional RF ablation, the success rate was significantly higher than the non-ATP inducible group (86.2% vs 67.3%; P = 0.04). A large proportion of the ATP-induced AF post CPVI were initiated by rapid firing in the SVC. Eliminating this response by additional ablation may have an influence on clinical results of paroxysmal AF ablation.

How to Achieve Complete and Permanent Pulmonary Vein Isolation without Complications.

The efficacy and safety of catheter ablation for the management of atrial fibrillation (AF) has been improved in recent years. Radiofrequency (RF) catheter ablation for maintaining sinus rhythm is superior to the current antiarrhythmic drug therapy in selected patients. Pulmonary vein isolation (PVI) is the cornerstone of various catheter ablation strategies. It is well recognized that pulmonary vein (PV) antrum contributes to the AF initiation and/or perpetuation. Since PV stenosis is a complication of ablation within a PV, the ablation site for PVI has shifted to the junction between the left atrium and the PV rather than the ostium of the PV. However, PV reconnection after ablation is the major cause of recurrence of AF. The recovery of PV conduction could be caused by anatomical variations such as the failure to produce complete transmural lesion or gaps at the ablation line due to the transient electrophysiologic effects from the RF ablation. In this review, we discussed several factors to be considered for the achievement of the best PVI, including clinical aspects and technical aspects.

Unipolar Electrogram Morphology to Assess Lesion Formation During Catheter Ablation of Atrial Fibrillation

The past decade has seen a significant increase in catheter ablation procedures for atrial fibrillation (AF)1; however, data on the efficacy of pulmonary vein (PV) isolation (PVI) are soberingly modest, with single and multiple procedure success rates of 54% and 79% for paroxysmal AF, respectively, during long-term follow-up (≥3 years).2 The main mechanism of AF recurrence after catheter ablation is resumption of PV-left atrial (LA) conduction.3 The time-dependent inevitability of recovery of PV conduction has been consistently demonstrated in acute studies showing PV conduction in ≤93% of patients during an intraprocedural waiting period of 60 minutes after PVI.4 Furthermore, late recurrence of AF is associated with conduction recovery in ≥1 PV in >97% of patients who are having a redo procedure.2 Thus, durable PVI is critical if we are to make inroads toward enhancing procedural efficacy. Article see p 1095 Gaps in the ablation line5 and failure to produce transmural lesions6 are implicated in recovery of PV conduction. PVI can be achieved after partial completion of a circumferential ring of lesions around the PVs, irrespective of intervening gaps. This is thought to result from a combination of irreversible and reversible atrial injury.7 Reversible atrial injury may stem from incomplete lesion formation that causes temporary electric uncoupling but not cell death ≤3.5 mm away from the lesion boundary, dependent on tissue temperature and tissue geometry.8 With time, tissue at the boundary of the transmural lesion recovers normal conduction during the course of 1 to 4 weeks.8 Thus, lesion gaps that exhibit conduction block frequently go undetected during the index procedure, and block persists for up to several weeks or months thereafter until tissue injury heals. Conduction block may occur in tissue with normal conductivity despite a gap of ≤1.4 mm …

Abstract 9570: Adenosine Triphosphate Facilitates Dormant Conduction across Left Atrial Lines in Patients With Atrial Fibrillation Who Underwent Catheter Ablation

Introduction: The addition of left atrial lines including a roof line, bottom line, and mitral isthmus line after pulmonary vein (PV) isolation may lead to a favorable outcome of atrial fibrillation (AF) ablation. Transient reconduction of the isolated pulmonary vein (PV) is induced by administration of adenosine triphosphate (ATP) and elimination of dormant conduction improves outcome of AF ablation. The potential role of ATP in other arrhythmic substrates, such as left atrial lines, remains unclear. The aim of this study was to investigate the characteristics and frequency of dormant left atrial line conduction. Methods: Sixty-four patients (50 men; mean age 65±10; 3 paroxysmal, 26 persistent, 35 Longstanding persistent) who underwent first ablation of left atrial lines were enrolled in this study. A roof line, bottom line and mitral isthmus line were performed in 63 patients, 44 patients and 64 patients, respectively. Irrigated ablation catheters were used through steerable sheaths with a max power of 35W at the endocardial surface and 30W in the coronary sinus. ATP (20mg) was given greater than 10 minutes after completion of left atrial lines to reveal dormant conduction. Results: Completion of a roof line, bottom line and mitral isthmus line was achieved in 97% (61/63), 98% (43/44), and 95% (61/64), respectively. Following administration of ATP, dormant conduction was observed in 3.2% at a roof line, 2.3% at a bottom line, and 3.2% at a mitral isthmus line. Persistent reconduction was observed in 1.6% at a roof line and 2.3% at a bottom line. Transient reconduction was observed in 1.6% at a roof line and 3.2% at a mitral isthmus line. Following additional ablation, dormant left atrial line conduction was eliminated in all patients. The frequency of dormant left atrial line conduction was similar to that of dormant PV conduction (6.3% vs 7.8%., P=0.7) Conclusion: Administration of ATP could reveal dormant left atrial line conduction. Dormant conduction was evenly induced among PVs and left atrial lines.

Prolonged ablation on critical segments of pulmonary vein ostia in paroxysmal atrial fibrillation: a prospective randomized controlled study.

Electrical reconnection of the pulmonary veins (PVs) plays a key role in the recurrence of atrial fibrillation (AF) after ablative treatment. This randomized controlled study tested the hypothesis that prolonged ablations, on areas that may be critical for left atrial (LA)-PV conduction, can significantly reduce the rate of acute PV reconnection and AF recurrence. Patients with paroxysmal AF were randomly assigned to either a control or an add-on group.Ostial PV isolation (PVI) was performed by point-to-point RF ablation (irrigated tip, 30 Watts, 30 seconds).An ostial segment was assumed to be critical for LA-PV connection if any of the following reactions occurred during RF application: (1) sudden delay of LA-PV conduction, (2) change of activation sequence,and (3) PVI. In this case, RF application was prolonged from 30 seconds to 90 seconds in the add-on group only. A total of 131 patients (58 ± 11 years, 47 female) were assigned to a control (n = 64) and an add-on (n = 67) group. Ablation time was longer in the add-on (48 ± 16 minutes vs 37 ± 15 minutes, P = 0.03). Acute PV reconnection was observed in 20 of 64 controls and in eight of 66 add-on patients (31% vs 12%, P < 0.001). During a follow-up of 26 months, AF recurred in 33 of 64 controls and in 16 of 66 add-on patients (52% vs 24%, P = 0.001) after a single ablation procedure. Prolonged radiofrequency application on critical segments of LA-PV connection is a safe and effective ablative strategy that significantly reduces acute PV reconnection and AF recurrence rates after a single ablation procedure for paroxysmal AF.

Adenosine-Induced Pulmonary Vein Ectopy as a Predictor of Recurrent Atrial Fibrillation After Pulmonary Vein Isolation

Adenosine can unmask dormant pulmonary vein (PV) conduction after PV isolation. Adenosine can also induce ectopy in electrically silent PVs after isolation, possibly via activation of autonomic triggers. We sought to identify the implications of adenosine-induced PV ectopy for atrial fibrillation (AF) recurrence after PV isolation. A total of 152 patients (age, 60±11 years; 63% paroxysmal AF) undergoing PV isolation for AF were studied. After each PV was isolated, adenosine was administered and the presence of adenosine-induced PV reconnection and PV ectopy were recorded. Dormant conduction was targeted with additional ablation. Adenosine-induced PV ectopy was seen in 45 (30%) patients, and dormant conduction was seen in 44 (29%) patients. After a median follow-up of 374 days, 48 (32%) patients had recurrent AF after a single ablation procedure. Rates of freedom from AF among patients with adenosine-induced PV ectopy were significantly lower than patients without adenosine-induced PV ectopy (63% versus 76% at 1 year; log rank, 0.014). Rates of freedom from AF among patients with dormant conduction were also lower than patients without dormant conduction (64% versus 76% at 1 year; log rank, 0.062). With multivariate analysis, adenosine-induced PV ectopy was found to be the only independent predictor of AF after PV isolation (hazard ratio, 1.90; 95% confidence interval, 1.06-3.40; P=0.032). Adenosine-induced PV ectopy is a predictor of recurrent AF after PV isolation and may be a marker of increased susceptibility to autonomic triggers of AF.

Electrophysiological Evaluation of Pulmonary Vein Isolation.

Since the pulmonary veins (PVs) were identified as a major source of AF triggers, ablation strategies targeting the PVs have evolved from focal ablation inside the PVs to wide area circumferential PV isolation (PVI) which at this juncture is the standard approach. Despite the widespread popularity of PVI, a universal definition is lacking. While "entrance block" is a generally accepted endpoint for PVI, the role of "exit block" has yet to be determined. Inexcitability of the circular ablation line has been introduced as a promising additional endpoint for PVI and was associated with an improved clinical outcome in a randomized trial. Correct interpretation of PV electrograms during an ablation procedure is critical in terms of efficacy and safety. A variety of electrophysiological techniques help to correctly differentiate components of complex PV electrograms. Resumption of PV conduction after initially successful PVI leading to AF recurrence remains a major problem and confirmation of bi-directional conduction block does not exclude reversible tissue damage along the ablation line. Prolongation of post-PVI monitoring and application of provocative procedures such as the administration of adenosine after initial PVI to unmask dormant PV conduction may improve clinical outcome although there is lack of valid data supporting these strategies. This article aims on clarifying the electrophysiological criteria for complete pulmonary vein isolation and the explain the importance of this cornerstone in almost all atrial fibrillation ablation procedures.

The COR trial: A randomized study with continuous rhythm monitoring to compare the efficacy of cryoenergy and radiofrequency for pulmonary vein isolation

Results from randomized trials designed to compare cryoenergy with radiofrequency for pulmonary vein (PV) isolation are lacking. To compare the efficacy of a simplified strategy for PV cryoablation (group C) vs PV isolation with open-irrigated radiofrequency catheters (group R). Fifty patients with paroxysmal atrial fibrillation (AF) and 4 independent PVs received a Reveal XT implantable cardiac monitor and were randomized to group C or group R. In group C, PV ablation was done with a single Arctic Front balloon (23 or 28 mm) per patient and two 300-second applications per PV. No further applications were delivered to close residual conduction gaps. In group R, bidirectional PV conduction block was pursued with Lasso and Navistar ThermoCool catheters and the CARTO system. The primary end point was the proportion of patients remaining free from AF recurrences ≥2 minutes without taking antiarrhythmic drugs 12 months after ablation. The primary end point was met by 12 (48%) patients in group C and 25 (68%) patients in group R (odds ratio 0.43; P = .05). This difference disappeared after adjustment for acute procedural outcome. In patients for whom all 4 PVs were blocked at the end of the procedure, there was no difference between group C and group R in the primary end point (67% vs 68%; P = .94). The efficacy of the simplified strategy for PV cryoablation tested in this study is inferior to PV isolation using open-irrigated radiofrequency catheters with electrophysiological and electroanatomical guidance. Complete PV conduction block is critical to the success of AF ablation.

Clinical significance of elimination of dormant pulmonary vein conduction revealed by adenosine after pulmonary vein isolation: 3-year follow-up

Purpose: This study evaluated the impact of elimination of Adenosine-Triphospatis (ATP)-induced dormant Pulmonary Vein (PV) conduction on the clinical outcome after PV isolation in patients with Atrial Fibrillation (AF). Methods: Study included 134 patients with paroxysmal (25%) and persistent (75%)AF. After antral PV isolation, 30 minutes observation period was applied. All acute PV reconnections were eliminated and then ATP-test was performed to reveal dormant conduction. In case of dormant conduction patients were randomized to 2 groups. Dormant conduction was eliminated by additional ablations in all patients of ATP-Abl group and remained intact in ATP-Control group. During follow-up period each patient was given antiarrhythmic drugs for 3 months. Results: After initial PV isolation and observation period ATP-test revealed dormant conduction in 33 out of 268 ipsilateral PV pairs (12%) in 31 patients (23%). ATP-Abl group included 14 patients, in whom all dormant conduction were eliminated by additional ablations in 15 ipsilateral PV pairs. ATP-Control group included 17 patients, in whom dormant conduction was revealed in 18 ipsilateral PV pairs, but left intacted. After 40 months follow-up 6 patients in ATP-Abl group (43%) and 6 patients in ATP-Control group (35%) were free from any arrhythmia (Log Rank test, p=0,39). ![Figure][1] Kaplan-Meier curves of freedom from AF Conclusion: After the application of 30 minutes observation period and reablation of all acute reconnections, dormant PV conduction was revealed in one fourth of the patients. Elimination of dormant PV conduction does not increase long-term freedom from AF. [1]: pending:yes

The effect of treating dormant pulmonary vein conduction on the outcome of cryoballoon ablation

The effect of treating dormant pulmonary vein conduction on the outcome of cryoballoon ablation

Corticosteroid use during pulmonary vein isolation is associated with a higher prevalence of dormant pulmonary vein conduction

Atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) is associated with PV to left atrium reconduction. The purpose of this study was to prospectively determine if the use of intraprocedural corticosteroids to limit the extent of tissue edema and/or inflammation alters the prevalence of spontaneous and adenosine-induced acute PV reconnection after PVI. Prior to wide circumferential PVI, 45 patients received a single intravenous (IV) bolus of hydrocortisone 250 mg immediately after transseptal access (steroid group). Another 45 consecutive patients underwent standard PVI without IV hydrocortisone (nonsteroid group). After PVI, all patients underwent adenosine testing to unmask dormant conduction. Patients were followed at 3, 6, and 12 months. Dormant conduction was unmasked in a significantly higher proportion of PVs in the steroid group compared with the nonsteroid group (32.8% of PVs [60/183] vs 21.1% of PVs [37/175], P = .03). On multivariate generalized estimating equation analysis, steroid use remained independently associated with dormant PV conduction (P = .03). There was no difference in the segmental distribution of reconnection between the 2 groups. The 1-year freedom from recurrent AF did not differ between groups (P = .37). Radiofrequency time was significantly longer in the steroid group (58 ± 21 minutes vs 48 ± 18 minutes, P <.01), whereas procedure duration and fluoroscopy time were comparable (P = .55 and P = .44, respectively). A single bolus of hydrocortisone 250 mg IV prior to PVI results in greater radiofrequency requirements for PVI and a higher prevalence of dormant PV conduction unmasked by adenosine. The utility of these approaches requires evaluation in a long-term prospective randomized study.

Repeat procedure using radiofrequency energy for recurrence of atrial fibrillation after initial cryoballoon ablation: a 2-year follow-up

The ideal energy source needed to perform 're-isolation' of the pulmonary veins (PVs) during a repeat procedure for recurrence of paroxysmal atrial fibrillation (AF) has not been established yet. In this study we analysed the outcome of repeat procedure using radiofrequency (RF) energy after initial cryoballoon (CB) ablation at 2-year follow-up. Consecutive patients having undergone PVs isolation as repeat procedure for recurrent AF after an initial CB ablation were eligible for this study. Twenty-nine patients (22 male 76%, mean age: 55 ± 17 years) were included. Mean time to repeat ablation was 12 ± 7 months. Recovered PV conduction could be documented in a mean 2.45 ± 0.7 veins in each patient. At mean 20.2 ± 10.7 months follow-up, a total of 16 patients (55%) were free of AF at without antiarrhythmic drugs (AADs). An adjunctive 31% was AF free with previously ineffective AADs. A major complication with no permanent clinical sequelae occurred only in one patient. Repeat RF ablation following CB in case of AF recurrence is effective and safe.

Spontaneous Dissociated Firing from the Pulmonary Veins during Ablation of Paroxysmal Atrial Fibrillation: Implications and Impact on Arrhythmia-Free Survival

Following pulmonary vein isolation (PVI) for the treatment of paroxysmal atrial fibrillation (AF), spontaneous dissociated firing (DiFi) from the isolated veins may be observed. Little is known about the significance and prognostic implications of this phenomenon. We sought to determine the relationship between DiFi and ablation outcomes. The study population consisted of 156 paroxysmal AF patients who underwent first time PVI and were found to have spontaneous DiFi from the pulmonary veins (PVs). Their outcomes were compared to a population of 156 propensity-matched controls from our prospectively maintained AF ablation data registry. DiFi was most frequently observed from the right superior PV and occurred in 89 patients (57.1%). After 24 months of follow-up, patients with DiFi had better success rates compared to those with silent veins after isolation (88.5% vs 75%, P = 0.002). The overall distribution of types of recurrent arrhythmia was similar between DiFi patients and their matched controls (P = NS). During repeat ablations, DiFi patients were less likely to have PV conduction recovery (60% vs 93.3%, P = 0.02). Importantly, none of the veins with DiFi during index procedures was found to have conduction recovery. In patients with paroxysmal AF undergoing ablation, DiFi from the PVs after their isolation was associated with improved ablation outcomes. It is possible that DiFi is an indicator of successful durable isolation of the PVs. The findings suggest that confirmation of exit block may be warranted to improve AF ablation outcomes.

Method for Differentiating Left Superior Pulmonary Vein Exit Conduction from Pseudo‐Exit Conduction

Electrical isolation of pulmonary vein (PV) conduction from the left atrium (LA) is the cornerstone of successful atrial fibrillation (AF) ablation. Exit block is confirmed by the absence of LA capture during pacing from a circular mapping catheter positioned in the PV; however, far-field capture of the left atrial appendage (LAA) (pseudo-pulmonary vein exit conduction) can occur. In this study, we evaluated a methodology for identifying pseudo-exit conduction. A total of 135 consecutive AF patients undergoing PV isolation were studied. After circumferential ablation established PV entrance block, circumferential pacing (10 mA at 2.0 msec) was performed to assess exit block. In 16 (11.9%) patients, pacing the anterior poles of the left superior PV (LSPV) captured the LA. To differentiate true PV exit conduction from pseudo-exit conduction, the ablation catheter was positioned within the LAA during PV pacing. LAA activation preceding PV capture was consistent with far-field capture and this was confirmed by demonstrating local capture and exit block with decreasing pacing output. Using this approach, 14 patients (10.4%) were identified with pseudo-exit conduction. Due to the close proximity between the LSPV and LAA, pseudo-exit conduction is not uncommon and may lead to the erroneous conclusion that the LSPV is not isolated. Using this method to differentiate pseudo-exit conduction from true exit conduction should prevent unnecessary ablation after achievement of complete PV isolation.

Catheter ablation of atrial fibrillation: Radiofrequency catheter ablation for redo procedures after cryoablation

To evaluate the effectiveness of two different strategies using radiofrequency catheter ablation for redo procedures after cryoablation of atrial fibrillation. Thirty patients (paroxysmal atrial fibrillation: 22 patients, persistent atrial fibrillation: 8 patients) had to undergo a redo procedure after initially successful circumferential pulmonary vein (PV) isolation with the cryoballoon technique (Arctic Front Balloon, CryoCath Technologies/Medtronic). The redo ablation procedures were performed using a segmental approach or a circumferential ablation strategy (CARTO; Biosense Webster) depending on the intra-procedural findings. After discharge, patients were scheduled for repeated visits at the arrhythmia clinic. A 7-day Holter monitoring was performed at 3, 12 and 24 mo after the ablation procedure. During the redo procedure, a mean number of 2.9 re-conducting pulmonary veins (SD ± 1.0 PVs) were detected (using a circular mapping catheter). In 20 patients, a segmental approach was sufficient to eliminate the residual pulmonary vein conduction because there were only a few recovered pulmonary vein fibres. In the remaining 10 patients, a circumferential ablation strategy was used because of a complete recovery of the PV-LA conduction. All recovered pulmonary veins could be isolated successfully again. At 2-year follow-up, 73.3% of all patients were free from an arrhythmia recurrence (22/30). There were no major complications. In patients with an initial circumferential pulmonary vein isolation using the cryoballoon technique, a repeat ablation procedure can be performed safely and effectively using radiofrequency catheter ablation.