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European Heart Journal Advance Access published online on March 6, 2007
European Heart Journal, doi:10.1093/eurheartj/ehl548
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© The European Society of Cardiology 2007. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Complete isolation of the pulmonary veins and posterior left atrium in chronic atrial fibrillation. Long-term clinical outcome{dagger}

Prashanthan Sanders*, Mélèze Hocini, Pierre Jaïs, Fréderic Sacher, Li-Fern Hsu, Yoshihide Takahashi, Martin Rotter, Thomas Rostock, Chrishan J. Nalliah, Jacques Clémenty and Michel Haïssaguerre

Hôpital Cardiologique du Haut-Lévêque and Université Victor Segalen Bordeaux-II, Bordeaux, France

Received 25 August 2006; revised 29 December 2006; accepted 25 January 2007.

* Corresponding author: Prashanthan Sanders, Cardiovascular Research Centre, Department of Cardiology, Royal Adelaide Hospital, Level 5, Mc Ewin Building, Adelaide, SA 5000, Australia. Tel: +61 8 8222 2723; fax: +61 8 8222 2722. E-mail address: prash.sanders{at}adelaide.edu.au


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conclusion
 Acknowledgements
 References
 
Aims: To evaluate the contribution of the posterior left atrium (LA) to chronic atrial fibrillation (AF).

Methods and results: Twenty-seven patients with chronic-AF were studied. After pulmonary vein (PV) isolation, the posterior-LA was isolated by ablation joining the right- and left-PVs using an irrigated-tip catheter. Isolation was demonstrated by absent/dissociated posterior-LA activity and the inability to pace the region. Ablation impact was determined by the effect on cycle length (CL) and AF termination. Posterior-LA isolation was achieved using 35 ± 12 min of radiofrequency with total fluoroscopic and procedural durations of 64 ± 16 and 199 ± 46 min, resulting in abolition of electrograms (n = 21) or autonomous activity (n = 6; CL 820 ± 343 ms). AFCL increased from 156 ± 28 ms to 162 ± 27 ms with PV-isolation and to 175 ± 32 ms by posterior-LA exclusion (P < 0.0001). AF persisted in all after PV-isolation and terminated in 5 (19%) during posterior-LA-isolation. After 10 ± 6 months, 12 patients developed atrial tachycardia (four) or AF (eight); four underwent repeat posterior-LA-isolation, while the others required additional ablation/antiarrhythmics. After 21 ± 5 months, 17 (63%) were in sinus rhythm following posterior-LA-isolation.

Conclusion: This study demonstrates the feasibility of complete posterior-LA exclusion by catheter ablation. This strategy results in maintenance of sinus rhythm in 63% at ~2 years follow-up.

Key Words: Atrial fibrillation • Arrhythmia • Ablation • Electrophysiology


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conclusion
 Acknowledgements
 References
 
The posterior left atrium (LA) and pulmonary veins (PV) are a dominant source of recurrent rapid activity emanating continuously, intermittently, or alternately during atrial fibrillation (AF).1 This activity demonstrates a frequency gradient away from the posterior-LA.2,3 In addition, regions of short cycle length (CL) fibrillatory activity localized to the posterior-LA in animals have been observed, with their ablation producing the termination of AF; thereby implicating this region in the maintenance of AF.4 In humans, isolation of the PVs, involving a variable component of the posterior-LA, has been highly effective in terminating paroxysmal AF and results in a significant long-term suppression of arrhythmia.5–9 However, the role of the posterior-LA in the maintenance of chronic AF has not been characterized.

This prospective clinical study was designed to evaluate the feasibility of using radiofrequency catheter ablation to completely isolate the entire posterior-LA and to determine the resulting electrophysiological and clinical outcome.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Conclusion
 Acknowledgements
 References
 
Study population
The study comprised 27 patients with symptomatic drug refractory chronic AF undergoing radiofrequency catheter ablation. These patients were selected on the basis of having chronic AF defined as sustained AF of ≥ 6 months duration. Baseline characteristics of patients studied are presented in Table 1. All patients provided written informed consent to the study protocol that was approved by the institutional Clinical Research and Ethics Committee.


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  		Table 1 Baseline patient characteristics based on the long-term success of posterior-LA isolation alone in maintaining sinus rhythm without the use of anti-arrhythmic drugs

 
Electrophysiologic study
All antiarrhythmics, with the exception of amiodarone, were ceased ≥ 5 half-lives prior to ablation. Oral anticoagulation was administered (INR 2–3) for at least 1 month before the procedure and transesophageal echocardiography was performed within 5 days to exclude atrial thrombus.

Surface electrocardiogram and bipolar endocardial electrograms were continuously monitored and stored on a computer-based digital amplifier/recorder system (Bard Electrophysiology). Intracardiac electrograms were filtered from 30 to 500 Hz and measured at a sweep speed of 100 mm/s.

Radiofrequency ablation
All patients had PV electrical isolation, cavo-tricuspid isthmus ablation, and isolation of the posterior-LA. For the purposes of the study, the posterior-LA was defined as the region bounded by the PV ostia; superiorly by a line joining the top of the superior PVs and inferiorly by a line joining the bottom of the inferior PVs. The lateral boundaries of the posterior-LA were completed by the contiguous lesions of PV isolation.

Ablation at sites outside the above-defined posterior-LA was only performed in patients with arrhythmia refractory to electrical cardioversion (after more than three attempts at external cardioversion). Such substrate modification involved targeting fractionated electrograms and/or linear ablation. If patients underwent additional ablation outside the posterior-LA, they were considered to have failed the strategy of posterior-LA isolation alone. All patients were reverted to sinus rhythm either by ablation or electrical cardioversion in the electrophysiology laboratory.

PV electrical isolation
The techniques used for PV isolation have been described previously. In brief, the following catheters were introduced via the right femoral vein for electrophysiological study: (i) a steerable quadripolar catheter (Xtrem; Ela Medical) was positioned in the coronary sinus (CS) at 4–5 o'clock on the mitral annulus in the left anterior-oblique projection, at a site with minimal or absent ventricular electrogram or in the LA appendage; (ii) a circumferential mapping catheter (Lasso, Biosense-Webster) was introduced following transeptal access and stabilized with the aid of a long sheath (Preface multipurpose, Biosense-Webster) that was continuously perfused with heparinized glucose; and (iii) a 3.5 mm irrigated-tip ablation catheter (Celsius Thermocool or Navistar, Biosense-Webster). Following transeptal access, a single bolus of 50 IU/kg body weight of heparin was administered and repeated only for procedures lasting ≥ 4 h.

Ablation was performed proximally to minimize the risk of PV stenosis, ~1 cm from the ostia of both right-PVs, as identified on fluoroscopy and 3D mapping, for the posterior and superior aspects of the left-PVs. Ablation was commenced by confluent lesions along the posterior border of the PV ostia and extended circumferentially around the venous perimeter. However, when ablation was required at the anterior portions of the left-PVs, energy was delivered within the first part of the PV targeting the earliest site of PV activation. Ablation was guided by the use of circumferential mapping and anatomical guidance using CARTO (Biosense-Webster) or NavX (St Jude Medical). The endpoint of PV ablation was electrical isolation signified by the abolition or dissociation of PV potentials. RF energy was delivered for 30–60 s at each point and this application was prolonged for 1–2 min when a change occurred in activation of the PV potentials as determined by circumferential mapping recorded down stream. RF energy was delivered with power limited to 25–35 W using irrigation rates of 17–60 mL/min (0.9% saline via Cool Flow; Biosense-Webster) to achieve the desired power. Temperature was limited to 50°C.

Cavotricuspid isthmus ablation
Ablation of the cavotricuspid isthmus was performed with an endpoint of bi-directional conduction block, confirmed during pacing after restoration of sinus rhythm. Ablation of the cavotricupid isthmus was performed after the completion of LA ablation. Radiofrequency energy was delivered with power limited to 30–35 W using irrigation rates of 17–60 mL/min to achieve the desired power. Temperature was limited to 50°C.

Posterior left atrial isolation
Isolation of the posterior-LA was achieved by the following configuration of linear ablation (Figure 1): (i) joining the two superior PVs (roofline) and, (ii) joining the two inferior PVs (inferior line). The lateral boundaries of the posterior-LA were formed by the contiguous lesions previously created by PV isolation. This was performed with the use of either CARTO (Biosense-Webster) or NavX (St Jude Medical) guidance.


Figure 1
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  		Figure 1 Schematic and NavX maps demonstrating the ablation for posterior-LA isolation. The grey area on the schematic indicates PV isolation. The un-edited ablation lesions are demonstrated on the NavX map as brown tags.

 
Ablation of the roofline was performed as previously described.10 The ablation catheter was introduced through the long sheath for stability and ablation commenced at the left superior PV. Using a dragging technique with clockwise torque of the assembly, ablation was continued to the right superior PV using parallel and/or perpendicular catheter-tissue configurations. This line was performed as cranially as possible on the left atrial roof. RF energy was delivered for 60–120 s at each point while monitoring the on-line potentials to achieve elimination or formation of local double potentials. The stability of the catheter was monitored during RF applications using the proximal electrograms, intermittent fluoroscopy and 3D navigation. Radiofrequency energy was delivered with power limited to 30 watts using irrigation rates of 17–60 mL/min to achieve the desired power. Temperature was limited to 50°C.

Following the roofline, ablation of the inferior line was performed by curving the catheter with clockwise torque maintained on the sheath-catheter assembly to perform linear ablation between the two inferior PVs. The ablation technique is as described above for the roofline ablation and used a maximal power of 20–30 W. Other than restricting the power delivery, no other specific precautions were taken to minimize the risk of atrio-esophageal fistula. During ablation, the proximal bipole was used to monitor the slowing of posterior-LA activity with progressive completion of the posterior-LA rectangle. Care was taken to prevent delivery of RF within the PVs. In the event of persistent conduction, the lines were meticulously mapped to determine the presence of potentials signifying a gap, which were ablated as previously described.11 Complete isolation of the posterior-LA was confirmed by the absence or dissociation of potentials within the ablated zone (Figures 2 and 3). The persistence of complete isolation of the posterior-LA was then confirmed in sinus rhythm and by pacing at maximum output (20 mA) from within the isolated posterior-LA, demonstrating failure to capture the remaining atria (Figure 2).


Figure 2
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  		Figure 2 Validation of posterior-LA isolation. Pacing with the ablation catheter at maximal output in the posterior-LA. In this example, the local tissue activation in the posterior-LA is seen on the proximal bipole of the ablation catheter (arrows) while uninterrupted atrial activation is seen in the CS with the atria in sinus rhythm.

 

Figure 3
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  		Figure 3 (A) Dissociated activity within the posterior-LA with the atria in sinus rhythm. (B) Brief burst of activity in the isolated posterior-LA with the remaining atria in sinus rhythm. In both examples, the catheter is positioned in the mid posterior-LA.

 
Monitoring the effect of ablation
The effect of ablation on the AF process was determined utilizing the change in AF cycle length (AFCL) within the CS or LA appendage and the termination of AF, as previously described.5

The AFCL was determined by averaging the interval of 30 consecutive cycles before and after the completion of PV isolation and posterior-LA isolation, using automated CL monitoring software (Bard Electrophysiology). Inter-electrogram intervals of < 100 ms and continuous electrical activity were counted as a single interval.5 At each time point, the automated annotation was manually verified and corrected using online callipers at a paper speed of 100 mm/s by a single investigator.

If AF terminated during ablation to flutter or sinus rhythm, the AFCL was determined prior to termination. To avoid transitional changes in CL, the AFCL determined 10 cycles before termination. Termination of AF was defined as direct transition to sinus rhythm or conversion to flutter.5 AF was defined by the beat-to-beat variability in CL and morphology, while atrial flutter was defined as a rapid regular atrial rhythm with stable CL, morphology, and activation sequence.

Follow-up
Patients received subcutaneous heparin while oral anticoagulation was re-initiated. Amiodarone was ceased in all patients after ablation. However, all patients received antiarrhythmic drugs for 2–3 months after ablation.

Patients were hospitalized for 1 day at 1, 3, 6, and 12 months after the last procedure for assessment involving ambulatory monitoring and exercise stress testing. At 12 months post-procedure, all patients underwent CT angiography to exclude PV stenosis. After this time, in the absence of symptomatic or asymptomatic AF, the referring physician provided follow-up data.

In the event of recurrent arrhythmia, patients were offered further ablation or trial of antiarrhythmic drug therapy. At the second procedure, the completeness of posterior-LA isolation was evaluated (as described above). In the presence of conduction recovery, re-isolation was performed as the first step; patients with persistent AF underwent cardioversion. If patients could be cardioverted, no further ablation was performed and they were followed again for the efficacy of this strategy in the prevention of arrhythmia. If atrial tachycardia (AT) was the presentation, these were localized using activation and entrainment mapping and ablated. If patients failed attempts at cardioversion (≥ 3 attempts) after repeat isolation of the posterior-LA then additional substrate modification was undertaken. Any patient requiring ablation at sites other than the posterior-LA due to AT or inability to cardiovert were considered as a failure of the strategy of posterior-LA isolation. If patients had no additional ablation other than specified by the research protocol they continued in the study. The effectiveness of posterior-LA isolation was evaluated in terms of the maintenance of sinus rhythm. If patients maintained sinus rhythm for 3–6 months, cessation of anticoagulation was considered.

Statistical analysis
All variables are reported as mean ± SD or median and range. Data that were normally distributed (Shapiro-Wilk test) were compared using the paired or unpaired Student's t-test (two-sided). Data that were not normally distributed were compared using the Wilcoxon Signed-Rank or Rank-Sum tests, for paired and unpaired data, respectively. Sequential measurements of AFCL were analysed by a single factor repeated measures ANOVA (to minimize the type 1 error due to multiple testing) followed by Scheffé's comparison. Categorical variables are reported as number and percentage, and compared using the Fisher's exact test. A Kaplan–Meyer curve was used to demonstrate time-to-arrhythmia events during follow-up after the last procedure. Statistical significance was established at P < 0.05.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conclusion
 Acknowledgements
 References
 
Patient characteristics
Patients had continuous AF for a median of 24 months (range 6–72 months) and had failed 3.3 ± 1.0 antiarrhythmics (including amiodarone in 17). All patients had undergone prior attempts at cardioversion with eight unable to restore sinus rhythm. Eight patients had evidence of structural heart disease; four with coronary artery disease, four with dilated cardiomyopathy, and one had hypertension. Table 1 presents the baseline characteristics of these patients.

Posterior left atrial isolation and automatic activity
All PVs were isolated using 35 ± 13 min of RF ablation. Isolation of the entire posterior-LA was achieved in all patients with an additional 35 ± 12 min of radiofrequency energy. This was performed with total fluoroscopic and procedural durations of 64 ± 16 min and 199 ± 46 min, respectively.

During ablation of the posterior-LA, a gradual slowing of posterior-LA activity with variable conduction block preceded complete isolation (Figure 4). The latter was demonstrated by the absence of local electrograms in 21 patients and dissociated activity in six patients (Figure 3). Spontaneous dissociated activity demonstrated a CL of 820 ± 343 ms (Figure 3) and occurred despite the absence of activity within the isolated PVs; in four patients, activity persisted at a constant CL, while in two it demonstrated significant beat-to-beat variation ranging from 480 to 1280 ms in one and 580 to 3000 ms in the other. In addition, one of these patients demonstrated intermittent rapid repetitive activity (up to four beats at a CL of 250 ms; Figure 3). In the remaining patients, no electrical activity was observed within the isolated posterior-LA in sinus rhythm, during pacing, or in AF (Figure 2).


Figure 4
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  		Figure 4 Slowing and dissociation of posterior-LA activity during completion of the inferior line. Note the patient remains in AF. The top panel demonstrates the slowing of activity on the proximal bipole of the ablation catheter while the bottom panel shows the dissociated electrical activity. Note the distal bipole of the ablation catheter was removed in both examples as the traces were taken during ablation with significant noise on the distal bipole.

 
Impact of posterior left atrial ablation on AF
During PV isolation, the AFCL increased by 6 ± 5 ms (range – 7 to 16 ms): from 156 ± 28 ms to 161 ± 27 ms (P = ns) with an increase ≥10 ms observed in five patients. Posterior-LA isolation resulted in a further increment in the AFCL by 13 ± 15 ms (range – 21 to 48 ms) to 175 ± 32 ms (P < 0.01) with an increase ≥ 10 ms observed in 13 patients (48%; P < 0.0001; Figure 5).


Figure 5
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  		Figure 5 Effect of ablation on the AFCL determined within the CS. Presented are the results for each individual patient together with the mean ± SD for each time point for the group.

 
In five patients (19%), AF terminated during ablation of the posterior-LA either directly to sinus rhythm (n = 3) or to AT (n = 2). While these patients demonstrated no differences in baseline characteristics, they had a significantly greater increase in AFCL when compared with those in whom AF did not terminate, 34 ± 13 ms vs. 8 ± 10 ms (P = 0.002). In the two patients with conversion to AT, a macro-re-entrant mechanism was identified by activation and entrainment mapping utilizing the cavotricuspid isthmus in 1 and mitral isthmus in 1. Cavotricuspid isthmus ablation terminated flutter in the former, and the latter was pace-terminated with no further ablation in keeping with the predefined study protocol.

In two patients, after isolation of the posterior-LA, repeated cardioversions (≥ 3) could not restore sinus rhythm and required additional substrate modification. In a further patient, repeated cardioversion was followed each time by the development of incessant perimitral macro re-entry. These three patients (11%) were considered failures of the protocol.

Recurrent arrhythmias after posterior left atrial isolation
Twelve patients (50%) developed recurrent arrhythmias at an average of 10 ± 6 months after initially successful posterior-LA isolation, AT in four and AF in eight. Half of these recurrences occurred more than 12 months after the initial procedure. There were no baseline factors predictive of recurrence.

Mapping was performed in all patients with AT and identified perimitral macro re-entry in two and re-entry localized to a small area in two. Perimitral macro re-entry occurred in one patient with persistent isolation of the posterior-LA (Figure 6A) and in one with partially recovered conduction of the posterior-LA. Both patients required mitral isthmus ablation which interrupted the tachycardia. Localized re-entry was mapped to the anterior LA in one and to the posterior-LA in the other. The former patient underwent anterior LA ablation to terminate tachycardia. Posterior-LA localized re-entry was observed to involve the left PVs and a small area of recovered conduction along the posterior wall and LA roof (Figure 6B). Re-entry was confirmed by entrainment and ablation performed to re-isolate the posterior-LA. All but the patient undergoing repeat isolation of the posterior-LA were considered to have failed the study protocol.


Figure 6
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  		Figure 6 (A) Electroanatomic activation mapping (left) and voltage map (right) of AT occurring after posterior-LA isolation. This patient presents with clockwise perimitral re-entry in the presence of persistently isolated posterior-LA. (B) Localized re-entry utilizing the recovered conduction through the roof and posterior-LA. Entrainment performed in this region demonstrated a post-pacing interval 10 ms longer than the tachycardia CL. The left superior and inferior PVs remained isolated. Ablation was performed to complete the roofline and resulted in termination of tachycardia. Additional application was required between the two PVs to achieve posterior-LA isolation.

 
Of the 8 patients presenting with AF, four were in persistent AF while four had paroxysmal episodes. Five patients agreed to a further procedure and underwent mapping and ablation. Four of these demonstrated recovery of posterior-LA conduction; in three patients (all with paroxysmal AF) the posterior-LA was re-isolated (two requiring re-isolation of the PVs). In the remaining one, sinus rhythm could not be restored despite repeated attempts at cardioversion after re-isolation of the posterior-LA and further ablation was required. In the one patient with no recovered conduction of the posterior-LA, additional substrate modification was performed. Three patients declined a further procedure and have been managed with antiarrhythmic agents; one of these has had no further arrhythmia for over 10 months while the other two have persistent AF.

Clinical outcome of posterior left atrial isolation
These patients have been followed for 21 ± 5 months after their initial procedure. Sinus rhythm was maintained without antiarrhythmic drugs in 12 patients (44%) at 23 ± 3 months after a single procedure and in a further 4 patients (15%) at 12 ± 6 months after a second procedure to re-isolate the posterior-LA (Figures 7 and 8). A single patient has been arrhythmia-free with the use of an antiarrhythmic drug (10 months). Thus, a total of 17 patients (63%) were in sinus rhythm after ablation of the posterior-LA and PVs (arrhythmia-free follow-up 20 ± 6 months). The cumulative proportion of patients remaining in sinus rhythm over the follow-up period after the last procedure is depicted in Figure 8.


Figure 7
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  		Figure 7 Schematic representation of the results of posterior-LA exclusion.

 

Figure 8
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  		Figure 8 Cumulative arrhythmia-free survival of patients after the final posterior-LA isolation procedure.

 
Eight patients (30%) have required additional ablation (outside the posterior-LA) due to the occurrence of clinical AT (n = 3), arrhythmia resistant to cardioversion (n = 4), or recurrent AF with persistent isolation of the posterior-LA (n = 1). Two patients (7%) have had recurrent AF and have elected not to undergo further intervention; no mapping has been performed to evaluate the persistence of posterior-LA isolation in these patients. The only variable associated with an unsuccessful long-term clinical outcome after posterior-LA isolation was the presence of concurrent structural heart disease (P = 0.03; Table 1).

All patients undergoing posterior-LA isolation demonstrated evidence of left atrial function; mitral A-wave velocity 50 ± 22 cm/s, 6 months following the procedure.

Procedural complications
Two patients had complications related to the procedure. One patient developed pericardial tamponade during catheter manipulation that required percutaneous drainage. One patient was observed to develop right phrenic nerve injury following ablation of the right superior PV. The patient has remained asymptomatic with complete recovery of diaphragmatic movement. No patient was observed to have PV stenosis.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conclusion
 Acknowledgements
 References
 
This study demonstrates the feasibility of isolating the posterior-LA by catheter ablation and the contribution of this region to the chronic fibrillatory process. Posterior-LA isolation could be achieved consistently with the use of irrigated ablation with the isolated region capable of automatic activity independent of the PVs. Exclusion of the posterior-LA during chronic AF resulted in a significant prolongation of the AFCL, incremental to the effect of PV isolation, and termination of AF in ~20%. At a long follow up, 63% of these patients with chronic AF have remained in sinus rhythm.

Posterior LA in paroxysmal AF
Experimental and clinical studies have identified that during AF the posterior-LA is activated more rapidly with a gradient of activation to the surrounding atria, implicating this region in the maintenance of AF.3,12–14 Further support for this notion has been demonstrated in a canine rapid atrial-pacing model of AF in which cryoablation, targeting areas of the shortest CL in the posterior-LA resulted in termination of AF.4

In humans, Todd et al.7 performed successful en bloc surgical isolation of the PV–posterior-LA with the addition of mitral isthmus ablation and excision of the LA appendage in 13 of 14 patients with predominantly paroxysmal AF (11 paroxysmal and three persistent AF). These investigators observed automatic activity within the PV–posterior-LA region that was dissociated from the remaining atria. Two of the 13 patients had arrhythmia recurrence, one with perimitral macro re-entry and the second with AF managed by re-isolation of the posterior-LA. However, similar observations of the role of the PVs have been made with isolation of the PVs with a variable component of the posterior-LA in patients with paroxysmal AF.5,6 Ouyang et al. isolated ipsilateral PVs by wide encircling and identified spontaneous activity in > 80% of PVs with 95% of these patients (some requiring a second procedure) remaining in sinus rhythm during follow up; this suggests that the substrate for paroxysmal AF in these patients is harboured within the PV–LA junction.6

Posterior-LA in chronic AF
Much less is known of the contribution of the PVs and posterior-LA in chronic AF. Wu et al.1 have observed repetitive activity originating from the corners of a posterior-LA mapping plaque during epicardial mapping and have suggested that this may represent PV activity. However, a strategy of PV isolation alone has been ineffective in the majority of patients with chronic AF.8,15,16

Nitta et al.17 have performed mapping in patients with predominantly continuous AF (37/46) and found that the majority of sites demonstrating focal activity occurred within the posterior-LA, from the tissue adjacent to the PVs but also from the region between the left and right PVs. Sueda et al.18 have performed surgical encircling of the entire posterior-LA and PVs in 49 patients with chronic AF, the majority having concurrent mitral valve disease. They have observed that some of these patients demonstrated repetitive activity from the posterior-LA and that this region frequently harboured the shortest CL activity during AF.

The current study adds to these observations by demonstrating that in chronic AF, ablation to isolate the posterior-LA after PV isolation results in further prolongation of the fibrillatory CL (independent of the PVs) with termination of AF achieved in ~ 20%. After isolation of this region, the posterior-LA demonstrates automatic activity, independent of the PVs, in up to 30% of patients. Although it may be argued that this represents a general ‘debulking’ of the atria, this seems less likely based on the significant effects observed during AF.

Catheter isolation of the posterior LA
To date, only the studies by Sueda et al.18 and Todd et al.7 have achieved complete isolation of the posterior-LA. Notably, in both studies isolation of the posterior-LA were achieved surgically. Previous attempts at isolation of the entire posterior-LA by catheter ablation have been unsuccessful. Ernst et al.19 attempted an encircling lesion around all of the PVs in 13 patients using a 4 mm tip catheter and achieved isolation in none. Subsequently, the same authors have described a single case of successful compartmentalization of the LA.20,21 However, more recently this group have reported the successful double PV encircling procedure, involving a similar form of atrial ablation to posterior-LA isolation, with the use of the irrigated catheter.6

In the current series, we were able to achieve isolation of the posterior-LA in all patients with a long-term success of the procedure in patients with chronic AF of 63%. These results are lower than those previously described using surgery or catheter ablation with wide posterior-LA ablation, probably due to the longer follow-up. These findings implicate the posterior-LA and PV region as having a significant role in the chronic fibrillatory process in about 2/3 of patients, but it indicates the role of other structures in the remaining.

Clinical implications
The ablation strategy in patients with chronic AF has been associated with the use of extensive substrate modification.22,23 The current study suggests that over half of these patients, the critical substrate for chronic AF is harboured within the posterior-LA and PV region. Indeed, the posterior-LA itself was observed to contribute in addition to that of the PVs to the AF process. Whether these results can be achieved with wide encircling ablation, encompassing a part of the posterior-LA, is not known. However, despite the complete exclusion of the posterior-LA, a significant proportion of patients with chronic AF required additional intervention.

The long follow-up utilized in this study provides important information on the recurrence of arrhythmia, highlighting the need for prolonged observation. Indeed half of the recurrent arrhythmias observed in this series occurred after 12 months.

Limitations
This study was not a randomized design but the patients included had characteristics similar to other series described with chronic-AF. While intermittent monitoring was used to detect asymptomatic arrhythmias, prolonged ambulatory monitoring was not performed and may have decreased the success rate. In addition, since the commencement of the study protocol, there have been a few cases reported of atrio-esophageal fistulas occurring as a result of ablation along the posterior-LA.24 While no particular change was made to our ablation strategy, the roofline was performed along the more cranial portion of the posterior-LA and all ablation for the inferior LA used power limited to 30 W. Importantly, these results were achieved in a centre with significant experience in AF ablation procedures; thus, generalization of the technique should be performed using a cautious approach.


   Conclusion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
Acknowledgements
 References
 
Isolation of the posterior-LA in patients with chronic AF is associated with prolongation of the AFCL, incremental to the effect of PV isolation, and termination of AF in ~ 20%. The isolated posterior-LA demonstrates automatic activity independent of the PVs. This procedure was associated with the long-term maintenance of sinus rhythm in 63% of patients with chronic AF.


   Acknowledgements
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 Acknowledgements
References
 
Dr Sanders is supported by the Neil Hamilton Fairley Fellowship from the National Health and Medical Research Council of Australia and the Ralph Reader Fellowship from the National Heart Foundation of Australia. Dr Rotter is supported by the Swiss National Foundation for Scientific Research, Bern, Switzerland. Dr Rostock is supported by the German Cardiac Society. Mr Nalliah is supported by the National Heart Foundation of Australia.

Conflict of interest Disclosures: P.S., P.J. and M.H. report having served on the advisory board of and having received lecture fees from Biosense-Webster and Bard Electrophysiology. M.R. and L.-F.H. report having received lecture fees from Biosense-Webster. P.S. reports having received lecture fees from St Jude Medical.


   Footnotes
 
{dagger} Previous Presentation: Presented in part at the Heart Rhythm Society's 26th Annual Scientific Sessions, New Orleans, May 2005 and published in abstract form (Heart Rhythm 2005;2:S228–S229). Back


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 Acknowledgements
 References
 

  1. Wu TJ, Doshi RN, Huang HL, Blanche C, Kass RM, Trento A, Cheng W, Karagueuzian HS, Peter CT, Chen PS. (2002) Simultaneous biatrial computerized mapping during permanent atrial fibrillation in patients with organic heart disease. J Cardiovasc Electrophysiol 13:571–577.[CrossRef][Web of Science][Medline]
  2. Mansour M, Mandapati R, Berenfeld O, Chen J, Samie FH, Jalife J. (2001) Left-to-right gradient of atrial frequencies during acute atrial fibrillation in the isolated sheep heart. Circulation 103:2631–2636.
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