Summary
Background
Catheter ablation is widely used to treat symptomatic atrial fibrillation (AF) refractory to drug therapy; and can be facilitated by a number of different techniques.
Aims
To evaluate our performance as a new centre for AF ablation and to evaluate the efficacy of different AF ablation techniques.
Methods
We employed three techniques in AF ablations; the three-dimensional (3D) mapping approaches (CARTO ® or Ensite NavX ® ) or multielectrode catheter duty-cycled radiofrequency ablation (pulmonary vein ablation catheter [PVAC ® ]). The immediate restoration of sinus rhythm was considered as acute success; while success at 6 months was determined by the maintenance of sinus rhythm on Holter monitoring.
Results
Between March 2008 and March 2010, 109 patients underwent AF ablations (mean age: 58 years; 72% male). Six-month success rates did not differ significantly between CARTO and NavX (40% vs 38%; P = 0.81), but the PVAC group achieved greater success than the two 3D-mapping groups combined (68% vs 39%; P = 0.004). Paroxysmal AF patients demonstrated greater 6-month success than persistent AF patients ( P = 0.005); and although the ratio of paroxysmal to persistent AF patients was slightly higher among the PVAC group, logistic regression confirmed PVAC and paroxysmal AF as predictors of success. Single-procedure success at 6 months was 48%. Including redo-ablations, some performed beyond the study period, our overall success rate at 6 months was 65%. Four patients experienced complications, but there were no deaths.
Conclusion
Despite being a new centre with relative inexperience, we achieved success rates comparable to those of established tertiary centres. PVAC performed significantly better than the two 3D-mapping approaches.
Résumé
Afin d’évaluer notre performance comme un nouveau centre pour la fibrillation auriculaire (FA) dans trois techniques d’ablation, les approches cartographie en trois dimensions (3D) utilisant CARTO ® ou NavX ® et l’ablation par radiofréquence multiélectrodes décapolaire circulaire à l’aide du cathéter d’ablation des veines pulmonaires (PVAC ® ).
Méthodes
Au cours des 24 premiers mois de mars 2008, nous avons réalisé 109 cas d’ablation de la FA. La restauration immédiate du rythme sinusal par ablation a été considéré comme un succès instantané. La réussite à six mois a été déterminée par le maintien du rythme sinusal au monitoring du Holter.
Résultats
L’âge moyen de notre cohorte était de 58 ans. Le taux de réussite à six mois ne différaient pas significativement entre les CARTO ® et NavX ® (40 % vs 38 %, p = 0,81) mais le groupe PVAC a connu plus de succès que les deux combinés groupes en 3D cartographie (68 % vs 39 %, p = 0,004). Les patients FA paroxystique (FAP) ont démontré une réussite plus grande de patients atteints de FA tenace à six mois ( p = 0,005). La proportion des patients paroxystique et de FA tenace n’était pas significativement différente entre les groupes de cartographie 3D et PVAC. La régression logistique a confirmé FAP et PVAC comme prédicteurs de succès. Le succès de une seule procédure à six mois était de 48 %. Y compris les ablations refait au-delà de la période d’étude, notre taux de réussite global à six mois était de 65 %. Nous avons eu quatre complications, mais aucun décès liés à l’arythmie.
Conclusions
En dépit d’un nouveau centre et de l’inexpérience relative, nous avons atteint les taux de succès comparables à ceux des centres de soins tertiaires établis. PVAC fait significativement meilleurs que les deux approches de cartographie en 3D. Nous recommandons donc l’ouverture de plusieurs installations d’ablation de la FA et l’adoption de PVAC dans ces centres.
Background
Catheter ablation of atrial fibrillation (AF) has been widely used in the treatment of symptomatic AF, as well as AF refractory to drug therapy or cardioversion . AF ablation (AFA) involves the isolation of triggers within pulmonary veins (PVs) using radiofrequency (RF) energy . To facilitate this, CARTO (Biosense Webster, Diamond Bar, CA, USA) uses magnetic fields to construct a three-dimensional (3D) geometry of the left atrium (LA), while Ensite NavX (St Jude Medical, St Paul, MN, USA) uses electrical fields to generate 3D maps. Pulmonary vein ablation catheter (PVAC) (Medtronic, Ablation Frontiers, Carlsbad, CA, USA) simplifies PV isolation procedures by using a multielectrode catheter capable of circular mapping and duty-cycled RF energy delivery without 3D guidance.
The aim of this retrospective study was to compare the efficacy of CARTO and NavX with that of PVAC, and to evaluate the performance of our new institution in a 6-month follow-up.
Methods
Patients
Our institution started performing AFAs in March 2008, undertaken by two operators. Patients included those with paroxysmal AF (self-terminating AF lasting < 7 days) or persistent AF (lasting for > 7 days but < 1 year) .
Transoesophageal echocardiogram was routinely performed prior to ablation procedures to rule out atrial thrombi. Warfarin was discontinued 5 days prior to the procedures and was replaced with low-molecular-weight heparin. This study formed part of a service evaluation of our new institution.
Ablation procedures
Patients underwent ablation using CARTO, NavX, or PVAC. Techniques were selected on a random basis in our cohort. The ablation procedures were performed under conscious sedation using diazepam and pethidine or general anaesthesia. Surface and intracardiac electrocardiograms (ECGs) were continuously monitored and recorded. In all three techniques, a steerable multipolar electrode catheter was positioned in the coronary sinus for pacing and recording.
LA access was gained through a transseptal puncture with Brockenbrough (St. Jude Medical) or Endrys (Cook Medical, Bloomington, IN, USA) needle, or through a patent foramen ovale when present. An SL1 (St. Jude Medical), Mullins (Cook Medical), or Channel (Bard, Covington, GA, USA) sheath was then introduced into the LA and infused with 0.9% saline. In the 3D-mapping approaches, a multipolar mapping catheter (Orbiter [Bard], Optima [St. Jude], or Lasso [Biosense Webster]) was passed through this sheath. An initial bolus of 10,000 units of heparin was given, followed by 2500–5000 units of additional boluses to maintain an activated clotting time of 300–400 seconds. Activated clotting times were determined every 30 minutes.
CARTO- and NavX-guided ablations were done with 30 W of RF energy delivered through an ablation catheter (Celsius or Navistar Thermocool [Biosense Webster] or Cool Path Duo [St. Jude Medical]) advanced into the LA through the initial puncture whenever possible. Otherwise, a second transseptal puncture was performed. The catheter tip was maintained < 48 °C with irrigated saline. Pulmonary vein isolation (PVI) was the primary goal in all cases. Wide area circumferential ablation (WACA) was performed around the PV antrum, proximal to PV ostia, in all patients. No ablations were done within or distal to PV ostia. Successful PVI was confirmed by circular mapping catheters positioned at the PV ostia. Linear ablations in the forms of roof, floor, and coronary sinus lines were done in addition to PVI in cases of persistent AF . Burns were performed in the coronary sinus and LA surface of the coronary sinus until definite change in coronary sinus activation suggested electrical isolation. Other linear burns were assessed by juxtaposed atrial pacing and presence of homogenous line of split potentials.
In PVAC ablations, after access into LA was gained, the PVAC was positioned at the antrum of each PV to record local electrical activity. RF energy was applied with a target temperature of 60 °C and 4/1 ratio between bipolar and unipolar energy. Multiple applications of RF were delivered to achieve antral isolation. Then, the PVAC was used to map all PV ostia. If PVs appeared to be incompletely isolated, additional RF applications were delivered using the PVAC until PVs were completely disconnected, based on PVAC signals and differential pacing manoeuvres. DC cardioversion was performed if sinus rhythm was not restored following the ablations.
Post-ablation and follow-up
After ablation, patients remained in hospital for ≥ 24 hours for telemetry monitoring. Patients were anti-coagulated with warfarin for ≥ 3 months. Low-molecular-weight heparin was administered until a therapeutic international normalized ratio > 2 was achieved. A transthoracic echocardiogram was performed the day after the procedure in all cases. A blanking period of 3 months was employed in this study as per international consensus . All patients were followed up in the outpatient clinic at 3, 6, and 12 months. A 12-lead ECG was recorded at each visit; and 24–48 hours of Holter monitoring was performed at each follow-up for all patients.
The successful restoration of sinus rhythm after ablations was considered as acute success. Success on follow-up was determined by the absence of symptoms and a lack of sustained AF of > 30 seconds on Holter monitoring. Data were collected from TOMCAT (Philips, Netherlands) and local electronic patient records.
Statistical analyses
Continuous data are presented as mean ± SD, and comparisons were performed with Student’s t test. Categorical variables are expressed as frequencies and percentages, and comparisons were performed with χ 2 analyses or Fisher’s exact test. Multivariable analyses were performed with logistic regression. All P values are two-sided and P < 0.05 indicates statistical significance. Statistical analyses were performed using SPSS (SPSS Inc, Chicago, IL, USA).
Results
Patient characteristics
In the 24 months from March 2008, we performed 117 AFAs. Two cases using cryoballoon (Arctic Front, Cryocath, Quebec, Canada) were excluded from this study. Six patients who had incomplete procedures due to vascular access difficulties such as femoral stenoses were also excluded. Therefore, only 109 patients (mean age 57.8 ± 10 years; 72% male) who received AFAs during the study period were analysed. All patients were symptomatic and refractory to drug treatment prior to ablation. Echocardiographic recordings demonstrated a mean LA size of 41.6 ± 7.3 mm (range 25–58 mm) and left ventricular ejection fraction (LVEF) of 57.1 ± 7.8% (range 26–70%).
We performed 47 ablations with CARTO (43%), 24 with NavX (22%), and 38 with PVAC (35%). There were no significant differences in baseline characteristics between the groups ( Table 1 ). Our cohort was composed of 73 patients with paroxysmal AF (67%) and 36 with persistent AF (33%). The ratio of paroxysmal to persistent AF patients was higher in the PVAC group than in the 3D-mapping groups, but this was not significant ( P = 0.052; Table 1 ).
| CARTO ( n = 47) | NavX ( n = 24) | 3D mapping (CARTO + NavX) ( n = 71) | PVAC ( n = 38) | P (PVAC vs 3D mapping) | |
|---|---|---|---|---|---|
| Age (years) | 56.2 ± 10.5 | 62.2 ± 7.7 | 58.2 ± 10.0 | 56.9 ± 10.2 | 0.51 |
| Male | 32 (68) | 17 (71) | 49 (69) | 29 (76) | 0.42 |
| LA size (mm) | 40.5 ± 7.5 | 43.9 ± 6.3 | 41.5 ± 7.3 | 42.0 ± 7.5 | 0.79 |
| LVEF (%) | 58.9 ± 6.4 | 55.4 ± 6.3 | 57.9 ± 6.5 | 55.6 ± 9.8 | 0.24 |
| AF type | 0.052 | ||||
| Paroxysmal | 28 (60) | 15 (63) | 43 (61) | 30 (79) | |
| Persistent | 19 (40) | 9 (38) | 28 (39) | 8 (21) | |
| Procedure time (min) | 246 ± 60 | 265 ± 60 | 252 ± 60 | 168 ± 41 | < 0.0001 |
| Fluoroscopy time (min) | 73 ± 27 | 79 ± 25 | 75 ± 26 | 39 ± 14 | < 0.0001 |
| Complications | 1 (2) | 1 (4) | 2 (3) | 2 (5) | 0.61 |
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