Summary
Background
Pulmonary vein (PV) isolation, using cryoballoon or radiofrequency ablation, is the cornerstone therapy for symptomatic paroxysmal atrial fibrillation (AF) refractory to antiarrhythmic drugs. One-third of the patients have recurrences, mainly due to PV reconnections.
Aims
To describe the different locations of reconnection sites in patients who had previously undergone radiofrequency or cryoballoon ablation, and to compare the characteristics of the redo procedures in both instances.
Methods
Demographic data and characteristics of the initial ablation (cryoballoon or radiofrequency) were collected. Number and localization of reconduction gaps, and redo characteristics were reviewed.
Results
Seventy-four patients scheduled for a redo ablation of paroxysmal AF were included; 38 had been treated by radiofrequency ablation and 36 by cryoballoon ablation during the first procedure. For the initial ablation, procedural and fluoroscopy times were significantly shorter for cryoballoon ablation (147.8 ± 52.6 min vs. 226.6 ± 64.3 min [ P < 0.001] and 37.0 ± 17.7 min vs. 50.8 ± 22.7 min [ P = 0.005], respectively). Overall, an identical number of gaps was found during redo procedures of cryoballoon and radiofrequency ablations. However, a significantly higher number of gaps were located in the right superior PV for patients first ablated with radiofrequency (0.9 ± 1.0 vs. 0.5 ± 0.9; P = 0.009). Gap localization displayed different patterns. Although not significant, redo procedures of cryoballoon ablation were slightly shorter and needed shorter durations of radiofrequency to achieve PV isolation.
Conclusions
During redo procedures, gap localization pattern is different for patients first ablated with cryoballoon or radiofrequency ablation, and right superior PV reconnections occur more frequently after radiofrequency ablation. Redo ablation of a previous cryoballoon ablation appears to be easier.
Résumé
Introduction
L’isolation des veines pulmonaires par radiofréquence ou cryothérapie est le traitement de référence de la fibrillation atriale (FA) symptomatique et résistante au traitement médical. Un tiers de patient vont cependant présenter des récidives de FA en lien principalement avec des reconnections veineuses pulmonaires (Gaps). Peu de données sont disponibles sur les caractéristiques des deuxièmes ablations en fonction du choix de l’énergie utilisée lors de la première procédure.
Méthodes
Les patients adressés pour une deuxième ablation de FA symptomatique et paroxystique entre 2011 et 2014 ont été rétrospectivement inclus. Les caractéristiques de la première et de la deuxième procédure ont été collectées. Le nombre et la localisation des reconnections veineuses pulmonaires ont été comparés.
Résultats
Soixante-quatorze patients ayant bénéficiés d’une deuxième procédure d’ablation ont été inclus. Trente-huit et 36 patients ont été respectivement traités par cryothérapie ou radiofréquence lors de la première ablation. Lors de la première procédure, la durée de procédure et le temps de fluoroscopie étaient significativement plus court dans le groupe cryothérapie (147,8 ± 52,6 vs. 226,6 ± 64,3 min, p < 0,001, et 37,0 ± 17,7 vs. 50,8 ± 22,7 min, p = 0,005, respectivement). Lors de la deuxième procédure, un même nombre de reconnections veineuses pulmonaires a été retrouvé dans les 2 groupes. Cependant, le nombre de gaps localisés au niveau de la veine supérieure droite était significativement plus élevé dans le groupe radiofréquence (0,5 ± 0,9 vs. 0,9 ± 1,0, p = 0,009). Les gaps suivent des localisations différentes, dépendantes du choix de l’énergie utilisée lors de la première ablation. Les caractéristiques de la deuxième procédure sont similaires dans les deux groupes.
Conclusion
Lors d’une deuxième procédure d’ablation de FA, les gaps ont des localisations différentes en fonction de l’énergie utilisée lors de la première procédure. Les reconnections situées au niveau de la veine pulmonaire supérieure droite sont plus fréquentes après une première ablation par radiofréquence. Les caractéristiques de la deuxième procédure (durée de procédure et temps de scopie) sont similaires que le patient soit premièrement isolé par cryothérapie ou radiofréquence.
Background
Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. Pulmonary veins (PVs) play a critical role in AF initiation, and their isolation is currently the cornerstone treatment for patients with symptomatic paroxysmal AF resistant to antiarrhythmic drug therapy. The most common strategies to achieve PV isolation are cryoballoon ablation and radiofrequency ablation, achieving up to 60–70% arrhythmia-free survival.
After the initial ablation, up to 30% of patients present AF recurrences, mainly due to PV reconnections , extra-PV triggers or adverse remodelling of atrial substrate. For patients with symptomatic recurrences, a redo ablation can be performed to assess PV isolation and ablate reconduction gaps, and sometimes to achieve a more thorough ablation of the left atrial (LA) substrate. Finding gaps in the initial lesion sets is sometimes challenging, and requires precise mapping of PV activation and pacing manoeuvers. Little is known about the characteristics of the redo procedure, depending on the choice of radiofrequency or cryoballoon ablation energy during the initial procedure, and on the pattern of localization of reconduction gaps for both strategies.
The aims of this study were to describe the different locations of reconnection sites in patients who had previously undergone radiofrequency or cryoballoon ablation, and to compare the characteristics of the redo procedures in both instances.
Methods
Patients and design
Patients referred to our tertiary centre from 2011 to 2014 for redo ablation of symptomatic paroxysmal AF (episodes < 7 days) were included retrospectively. A medical history, including age, sex, Cardiac failure, Hypertension, Age ≥ 75 years (Doubled), Diabetes, Stroke (Doubled) – Vascular disease, Age 65–74 years and Sex category (Female) (CHA 2 DS 2 -VASc) score, number of antiarrhythmic drugs attempted and existence of associated underlying cardiac disease, was obtained during the clinic visit. For the first procedure, patients were assigned to have radiofrequency or cryoballoon ablation depending on physician preference. All patients had the redo procedure performed using radiofrequency energy. All the ablations (radiofrequency and cryoballoon) were performed by a single experienced operator.
Exclusion criteria were a redo ablation for non-paroxysmal AF, LA tachycardia or flutter, and patients in whom LA roof or mitral isthmus ablation lines had been performed previously. Only patients with complete PV isolation at the first procedure were included; those in whom isolation of at least one PV had failed were excluded.
First AF ablation procedure
Before the ablation procedure, a transoesophageal echocardiogram was performed to exclude the presence of LA thrombus, and to measure LA dimensions and left ventricular ejection fraction. LA computed tomography was performed to examine the PV anatomy. Vitamin K antagonists or other oral anticoagulants were discontinued, and replaced by intravenous heparin. All procedures were performed under conscious sedation using midazolam and fentanyl, as necessary. Venous access was obtained via the femoral vein. In the absence of a patent foramen ovale, transseptal puncture was performed under fluoroscopic guidance, without the use of periprocedural transoesophageal or intracardiac echocardiography.
For patients referred for a radiofrequency ablation, a circumferential mapping catheter was advanced into the left atrium (LA) through the first transseptal sheath. A second transseptal puncture was performed to advance a 3.5 mm irrigated ablation catheter to the LA. Transseptal sheaths were continuously flushed with heparinized saline solution. Atrial geometry was constructed using either CARTO ® (Biosense Webster, Diamond Bar, CA, USA) or NavX™ (St. Jude Medical, Inc., St. Paul, MN, USA) mapping systems. Radiofrequency energy was delivered with a power of 25–30 W, depending on the targeted area, with a maximum temperature of 48 °C. The maximum power at the posterior wall was 25 W. Circumferential antral ablation at the atrial level of the PV antrum was performed around the ipsilateral PV. No carinal lesions were ablated. The procedural endpoint was PV isolation confirmed by a LASSO ® catheter (Biosense Webster). A 20-minute waiting period was observed after the last PV was ablated, to ensure persistent PV isolation.
For patients referred for cryoballoon ablation, a 6 F Xtrem ® quadripolar catheter (Sorin SPA, Milan, Italy) was placed in the coronary sinus via the right femoral vein. A single transseptal puncture was performed under fluoroscopic and pressure guidance. A “single big cryoballoon ablation” approach, using a 28 mm balloon, was performed as previously described . The cryoballoon catheter was introduced into the LA through a steerable 12 F inner diameter FlexCath ® sheath (Medtronic, Minneapolis, MN, USA), constantly flushed with heparinized saline. Finally, an Achieve™ mapping catheter (Medtronic) was advanced over the cryoballoon to the PV orifice, and positioned as proximally as possible inside the vessel to record the PV potentials at baseline and to monitor the isolation procedure in real time. Next, the cryoballoon was inflated and advanced to the ostium of each PV. The quality of vascular occlusion was ascertained by the injection of diluted contrast material into the PV, and ablation was performed for 240–300 seconds, depending on the minimal temperature achieved. An additional application of energy was systematically delivered after PV isolation, unless phrenic nerve paralysis was observed. Before ablation of the right-sided PV, the quadripolar catheter was relocated to the superior vena cava to constantly pace the right phrenic nerve at a 2000 ms cycle length and 20 mA output during freezing. In case of cessation or weakening of the right hemidiaphragmatic contraction, freezing was immediately discontinued and the cryoballoon was deflated. The endpoint of ablation was elimination of all PV potentials, confirmed by the Achieve™ catheter. A 20-minute waiting period was observed after the last PV was ablated, to ensure persistent PV isolation.
Adenosine injection was not systematically performed after PV isolation to unmask dormant conduction, and cavotricuspid isthmus ablation using radiofrequency was performed in those patients with a documented typical flutter in association with paroxysmal AF.
Follow-up after the initial procedure
Vitamin K antagonist treatment to obtain a target international normalization ratio of 2.0–3.0 was required for the first 3 months after ablation. Anticoagulation treatment was then left to the referring cardiologist’s discretion, depending on the thromboembolic risk of the patient. Antiarrhythmic drugs were stopped at the third month after the procedure if patients remained symptom free. Patients were routinely reviewed at 3 months with echocardiography, and after 12 and 24 months with clinic visits and electrocardiograms.
Redo procedures and localization of gaps
When a symptomatic AF recurrence was confirmed, patients were offered a redo procedure to detect PV reconnection and ablate possible reconnection gaps.
Initial procedural steps were performed as described above. After inserting the circular mapping and ablation catheters in the LA, PV isolation was assessed. The previous ablation lesions were identified using perprocedural electrophysiological data (voltage of the electrograms and/or presence of double potentials). Whenever PV reconnection was demonstrated, gaps were searched for using dedicated techniques (“pace-and-ablate” technique and analysis of the earliest activation in the circular mapping catheter).
The exact position of conduction gaps was proven by the occurrence of PV isolation during ablation or by the occurrence of an abrupt change in the PV activation pattern. The ablation lesions were performed outside the PV antra, at the level of the previous ablation line, at a power of 25 W in the posterior wall and 30 W in the rest of the LA (maximum temperature of 48 °C). Ipsilateral PVs were then divided into eight distinct zones, where the position of gaps was schematized.
At the time of redo ablation, roof and/or mitral isthmus lines or complex fractionated atrial electrogram ablation was performed, depending on the physician’s decision. For all the patients, extra-PV triggers were searched for during isoproterenol infusion before retrieving the catheter, and were eventually ablated. As described for the initial procedure, adenosine injection was not systematically performed after PV isolation to unmask dormant conduction.
This study was performed according to local institutional regulations and all patients provided written informed consent.
Statistical analysis
Normally distributed variables are expressed as means ± standard deviations, and were compared using Student’s t -test. Non-normally distributed variables are expressed as medians ± interquartile ranges, and were compared using the Mann-Whitney U test. Categorical variables are expressed as counts and percentages, and were compared using the Chi 2 test or Fisher’s exact test, when needed. A P -value < 0.05 was considered statistically significant. The analyses were performed with the SPSS statistical package, version 11.0 (SPSS Inc., Chicago, IL, USA).
Results
Study population
From 2011 to 2014, 74 patients were referred to our centre for a redo ablation of paroxysmal AF, having previously undergone cryoballoon ablation ( n = 36) or radiofrequency ablation ( n = 38). The characteristics of the patients are described in Table 1 . Most patients had lone paroxysmal AF (92%), non-dilated atria and very few comorbidities, as reflected in the low CHA 2 DS 2 -VASc score (63.5% having a score of 0 or 1).
| Cryoballoon group ( n = 36) | Radiofrequency group ( n = 38) | P | |
|---|---|---|---|
| Men | 27 (75.0) | 22 (57.9) | 0.51 |
| Hypertension | 20 (55.6) | 31 (81.6) | 0.023 |
| Diabetes mellitus | 2 (5.6) | 1 (2.6) | 0.61 |
| Cardiomyopathy | 1 (2.8) | 4 (10.5) | 0.36 |
| History of stroke | 3 (8.3) | 4 (10.5) | 1 |
| CHA 2 DS 2 -VASc | 0.73 | ||
| 0 | 12 (33.3) | 15 (39.5) | |
| 1 | 12 (33.3) | 8 (21.1) | |
| 2 | 9 (25.0) | 6 (15.8) | |
| ≥ 3 | 5 (13.9) | 7 (18.4) | |
| Years with AF | 8.6 ± 7.8 | 7.1 ± 8.1 | 0.13 |
| Duration of AF episodes | 0.12 | ||
| < 12 hours | 20 (55.6) | 12 (31.6) | |
| 12–24 hours | 8 (22.2) | 12 (31.6) | |
| > 24 hours | 8 (22.2) | 14 (36.8) | |
| Number of antiarrhythmic drugs tested | 2.7 ± 1.0 | 2.4 ± 1.0 | 0.30 |
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