Author + information
- Received May 30, 2012
- Revision received September 11, 2012
- Accepted September 11, 2012
- Published online April 23, 2013.
- Jürgen Vogt, MD⁎ (, )
- Johannes Heintze, MD,
- Klaus J. Gutleben, MD,
- Bogdan Muntean, MD,
- Dieter Horstkotte, MD, PhD and
- Georg Nölker, MD
- ↵⁎Reprint requests and correspondence:
Dr. Jürgen Vogt, Department of Cardiology, Heart Centre North Rhine-Westphalia, Ruhr University Bochum, Georgstrasse 11, Bad Oeynhausen 32545, Germany
Objectives The purpose of this study was to investigate long-term outcomes of freedom from atrial fibrillation (AF) after pulmonary vein (PV) isolation using cryoballoon ablation with balloon-size selection based on individual PV diameters.
Background Data are lacking on long-term outcomes from cryoablation and on the most effective balloon size.
Methods This was a prospective observational study involving 605 consecutively enrolled patients with symptomatic paroxysmal AF (n = 579) or persistent AF. Cryoballoon size was based on magnetic resonance imaging and/or conventional angiograms. Patients were followed up every 3 months during the first year after discharge and every 6 months in the second year. After 24 months, follow-up was on an outpatient basis with documented AF episodes recorded.
Results The PV isolation was achieved without touch-up in 91.1% of patients, using the smaller balloon in 26.7%, the larger balloon in 25.6%, and both balloons in 47.7% of patients. Follow-up data for >12 months (median 30 months; interquartile range 18 to 48 months) were available for 451 patients, 278 (61.6%) of whom were free of AF recurrence with no need for repeat procedures after the 3-month blanking period. Rates of freedom from AF after 1, 2, and 3 repeat procedures (using cryoballoon or radiofrequency ablation with similar success rates) were 74.9%, 76.2%, and 76.9%, respectively. Use of the smaller balloons or both balloons produced the highest rates of long-term freedom from AF. Phrenic nerve palsy occurred in 12 patients (2%), resolving within 3 to 9 months.
Conclusions Rates of long-term freedom from AF after cryoballoon ablation are similar to those reported for radiofrequency ablation. A choice between balloons may improve outcomes.
Ablation procedures for circumferential pulmonary vein isolation (PVI) by encircling the pulmonary vein (PV) antrum have become the therapy of choice for drug-refractory symptomatic focal atrial fibrillation (AF) (1), with a continual increase in the number of procedures performed annually (2). The majority of these procedures are carried out with radiofrequency energy, but the use of cryoballoon ablation is growing rapidly.
Most published cryoballoon studies have focused on 12-month outcomes (4–6), and current consensus guidelines note the need for follow-up data beyond 12 months from large patient populations (7,8). We conducted a prospective, large-scale, long-term investigation into the outcomes of cryoablation in consecutively enrolled patients with AF. The choice between the 23-mm and 28-mm balloons was made for individual veins on the basis of the anatomies of the PV ostia. We also included the option of using 2 balloon sizes in the same patient.
This was a prospective observational study involving 605 patients enrolled consecutively at our institute. All patients provided informed consent, and the study was approved by the local institutional ethics committee.
Enrolled patients had symptomatic paroxysmal AF, defined as per Heart Rhythm Society (HRS)/European Heart Rhythm Association (EHRA) consensus guidelines (8), with a history of failed treatment with antiarrhythmic drugs class Ic and/or III. Exclusion criteria were as published previously (4). Transesophageal echocardiography was performed on all candidates to exclude the presence of thrombi.
Ablation procedures and choice of balloon size followed what has been described previously (4). Any phenprocoumon anticoagulation therapy was continued, with a target international normalized ratio of 2.0 to <3.0. A double transseptal puncture was performed to access the left atrium (LA) in the first 253 patients. In the succeeding patients, the LA was accessed by a single transseptal puncture from the right femoral vein, and a steerable 12-F inner diameter sheath (FlexCath, Medtronic, Minneapolis, Minnesota) was employed. Balloon occlusion was assessed with the help of 50% diluted contrast medium injected into the PV and confirmed within the first minute of cryoenergy application (Fig. 1).
In the 518 patients treated between 2005 and 2010, a 20-polar Lasso catheter (Biosense Webster, Diamond Bar, California) was placed in the LA to map signals before and after ablation at the ostial sides of PVs. Starting in 2010, the Achieve mapping catheter (Medtronic) was employed instead to enable mapping during and after each freezing procedure (n = 87). Freezing times were 2 × 360 s for each vein, 3 × 300 s for left superior (LS) PVs.
Sustained PVI was confirmed 30 min after the initial isolation. For difficult verifications, namely, because of large far-field potentials of the LA, exit block was confirmed by pacing within the PV ostium monitored with the Lasso or Achieve catheter. In 53 patients in the early cohort, touch-up of remaining gaps was performed with the 8-mm tip Freezor MAX focal cryoablation catheter (Medtronic Cryocath). In all later patients, residual potentials were eliminated with additional balloon freezes.
Post-ablation treatment was as described previously (4). During a blanking period of 3 months, antiarrhythmic treatment with the former ineffective drug was allowed to facilitate maintenance of sinus rhythm. Patients who failed 3 repeat ablation attempts were put on antiarrhythmic drug regimens.
Patients were scheduled for follow-up visits every 3 months during the first year after discharge and every 6 months in the second year. After 24 months, follow-up was on an outpatient basis with documented AF episodes recorded.
In the first 109 patients, 1 or more magnetic resonance imaging/computed tomography scans were performed during the first 12 months to assess PV diameters and to exclude PV stenosis. The procedure was found unnecessary and discontinued for subsequent patients. Seven-day Holter electrocardiography (ECG) recordings were obtained at each visit for the first 12 months of follow-up, including the first 12 months after repeat procedures (8).
The primary endpoint was successful isolation of all 4 PVs, defined as confirmed unidirectional entrance block complete with absence of PV spikes. Secondary endpoints were the recurrence of AF during follow-up, procedural data, complications, and the time to successful PVI. Recurrence was defined as an episode of AF >30 s documented on 7-day Holter ECG, or any ECG-documented AF during follow-up. No Holter monitoring was included in the protocol after the first 12 months. Safety endpoints were the occurrence of PV stenosis or atrioesophageal fistula and peri-interventional safety.
Kaplan-Meier univariate analysis was used to estimate AF-free survival. Continuous data are represented as mean ± SD or median and interquartile range, as appropriate. The chi-square test was employed post-hoc for comparisons of success and recurrence rates between different balloon sizes and an unpaired t test for post-hoc comparisons of procedure and fluoroscopy times between balloon sizes. The criterion for statistical significance was set to p < 0.05.
A total of 605 patients were enrolled consecutively between July 2005 and August 2011. The flow of patients is shown in Figure 2. Demographic criteria are shown in Table 1. In 26 patients, persistent AF developed between the scheduling and carrying out of the ablation procedure, and they remained in the study population.
The PVI was achieved without the need for focal touch-up with Freezor MAX in 551 patients (91.1%). An average of 2.4 ± 1.0 applications were needed to achieve PVI. Total procedure and fluoroscopy times with the 28-mm balloon, 23-mm balloon, and 2 balloons, respectively, are shown in Table 2. There was a steep learning curve (Fig. 3).
Of the 551 patients treated with cryoballoon ablation only, 147 patients (26.7%) were treated with the 23-mm balloon, and 141 patients (25.6%) with the 28-mm balloon. Two balloons were employed in 263 patients (47.7%), primarily in cases of rapid reconduction despite good occlusion in younger patients with greater cardiac output, when hockey-stick or pull-down maneuvers were unsuccessful, in conically shaped venous openings, insufficient occlusion with the 28-mm balloon, or for final isolation of incompletely isolated right inferior PVs.
Recurrences of AF within the blanking period were documented for 46 patients, 23 of whom had no further recurrences and did not undergo repeat procedures.
Freedom from AF during long-term follow-up
Twenty patients were lost to follow-up. One patient died before the first follow-up visit, and 2 patients died during follow-up. No death was associated with any of the procedures. Follow-up data after the 3-month blanking period (median 24 months; interquartile range: 12 to 42 months; mean 28.2 ± 19.0 months) were available for 554 patients (91.6%). Rates of freedom from AF were significantly higher using the 23-mm balloon or 2 balloons than using only the 28-mm balloon (Fig. 4A). This difference remained significant when the 53 patients who received focal touch up with Freezor MAX were excluded from the analysis.
Long-term follow-up data >12 months (median 30 months; interquartile range: 18 to 48 months; mean 33.4 ± 17.3 months) were available for 451 patients. Actively solicited data on vital status at the end of follow-up were obtained for 191 patients. Of the 451 patients, 278 (61.6%) remained free of AF with no need for repeat procedures after the blanking period (Fig. 4B). The percentages of patients free of AF after 1, 2, and 3 repeat procedures, respectively, after the blanking period were 74.9%, 76.2%, and 76.9%. The first repeat procedure utilized cryoballoon in 79 cases and radiofrequency in 28 cases. Further repeat procedures were predominantly radiofrequency ablations (13 of 18 procedures). Success rates were similar with both technologies.
The rate of decline in freedom from documented AF recurrences was steepest during the first 12 months of follow-up (Fig. 4B). A total of 124 recurrences (22.4% of patients) were documented between months 4 and 12, and 59 recurrences (10.6%) were documented after month 12.
Acute adverse events are shown in Table 3. Phrenic nerve palsy (PNP) occurred in 12 patients (2%) and resolved within 3 to 9 months. There was no case of chronic PNP. Hemoptysis with hematoma or edema around PVs was observed in 10 cases, all of which healed within 10 days. Patients remained free of hemoptysis during the follow-up period.
This study provides data on the long-term effectiveness and safety of cryoballoon ablation in a large representative cohort of patients with paroxysmal AF. The mean documented follow-up time of 33.4 ± 17.3 months is the longest reported to date for PVI with cryoballoon ablation.
Long-term success rates of PVI procedures
Rates of freedom from AF without and with repeat ablations after the initial 3-month blanking period were 61.6% and 76.9%, respectively, highly similar to rates achieved with radiofrequency ablation (9,10). Rates of freedom from AF could be improved by optimizing the choice of balloon size to fit the PV anatomies in each individual case.
Most recurrences occurred within the first 12 months, as previously reported both for radiofrequency ablation and for cryoablation over shorter follow-up periods (5). That may be due in part to the changes in follow-up examinations. Both in our study and in the 5-year follow-up analysis of radiofrequency ablation (10), 7-day Holter ECG monitoring was not routinely performed after >12 months of follow up. A direct comparison between cryoballoon and radiofrequency ablation technologies is conducted in the on-going prospective, randomized FIRE AND ICE trial (NCT01490814).
The similarities in outcomes from cryoballoon and radiofrequency ablation may hint at limitations inherent in PVI. The first repeat procedures, whether cryoballoon or radiofrequency ablation, increased the percentage of recurrence-free patients by 13.3 percentage points. Subsequent repeat procedures increased rates by a fraction of this amount. Two conclusions might be drawn. First, cryoablation is an equally valid alternative to radiofrequency for repeat procedures. Second, lack of success is most likely due to underlying pathologies rather than to the method used. If so, the challenge would be to identify in advance this subgroup of patients who are particularly resistant to PVI and consider alternative treatments, rather than attempt incremental procedural improvements.
Choice of optimal cryoballoon size
Some groups have advocated the 28-mm “single big balloon” methodology (11,12), but there are concerns that improved safety with the larger balloon may come at the cost of lower success rates (13,14). By providing tissue contact closer to the equatorial region of the balloon, smaller balloons may produce lower temperatures than the 28-mm balloon. In our hands, recurrence rates were indeed highest with the larger balloon. However, the larger balloon should be the first choice to create an antral isolation in large veins and common ostia, as the smaller 23-mm balloon may cause ostial isolation and jeopardize lung tissue, esophagus, and PV diameter. In our center, the balloon size is guided by the anatomy, with the option to use 2 balloon sizes in the same patient.
We recorded very few PNPs, despite frequent use of the smaller 23-mm balloon. We found 10 cases of bronchial erosion and hemoptysis. Although this corresponds to an incidence rate of <2%, and all cases healed within 10 days, operators should be aware of the potential risk.
This was a single-center study with possibly smaller differences between individual operators than in multicenter studies. Operator familiarity and preferences for 1 balloon size over the other may have influenced the results. Follow-up became less rigorous after the first 12 months. Furthermore, the equipment changed during the study, notably the discontinuation of Freezor MAX after the first 53 patients and the introduction of the Achieve catheter for the last 83 patients.
In our clinical experience, long-term rates of freedom from AF over several years after cryoballoon ablation appear comparable to those with radiofrequency energy ablation, although randomized, controlled studies would be needed to demonstrate this conclusively. Selecting the appropriate balloon size for each individual vein anatomy to ensure the best fit increases long-term success rates, but there is a trade-off in increased procedural risk with the smaller balloon that should be taken into account.
Birgit Wellmann, Cordula Kreft, and Simone Rolfsmeier helped with data management and follow-up, Astrid Kleemeyer provided scientific coordination, and Pelle Stolt, PhD, helped prepare the first draft of this manuscript.
This work was supported by an unrestricted grant from Medtronic. The sponsor had no influence on the generation of the protocol, study conduct, data analysis, and interpretation, or on the content and production of the manuscript.
Dr. Vogt has received speaker's honoraria and honoraria for advisory board meetings from Medtronic. Drs. Nölker, Gutleben, and Heintze have received speaker's honoraria from Medtronic. All other authors have reported they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- atrial fibrillation
- left atrium
- left superior
- phrenic nerve palsy
- pulmonary vein
- pulmonary vein isolation
- Received May 30, 2012.
- Revision received September 11, 2012.
- Accepted September 11, 2012.
- American College of Cardiology Foundation
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