Methods

One hundred three of 249 consecutive patients who underwent PVI at Beth Israel Deaconess Medical Center (Boston, Massachusetts) from January 2002 to December 2006 and were prospectively followed for ≥4 years after the index procedure were included in the present study. Patients with insufficient data and those lost to follow-up (most whom lived at a distance, believed that they were doing well clinically, and chose not to continue follow-up after 2 years) as well as patients who underwent previous PVI procedures at other institutions or who were not followed at our center were excluded. AF was defined as paroxysmal, persistent, or longstanding persistent according to international guidelines. Before ablation, all patients underwent transesophageal echocardiography or intracardiac echocardiography and cardiac magnetic resonance imaging or cardiac computed tomography to rule out the presence of intracardiac thrombi and to assess PV size, anatomy, and flow velocities. Anticoagulation treatment with warfarin, if any, was stopped 3 to 4 days before ablation and replaced with subcutaneous low–molecular weight heparin until the day before the procedure. Demographic and clinical details were obtained from the electronic medical record. This study was approved by the Beth Israel Deaconess Medical Center committee on clinical investigations. All patients provided informed consent before the procedure.

Catheter ablation of AF was performed by a single operator (M.E.J.). The ablation protocol has been previously described in detail. In summary, all procedures were performed under general anesthesia or conscious sedation. Left atrial access was obtained by 2 transseptal punctures. Transesophageal echocardiography or intracardiac echocardiography (throughout the procedure) was used to exclude the presence of intra-atrial thrombi and to identify PV anatomy and velocities before and after ablation, to identify catheter position with reference to the vein ostia, to determine the presence or absence of pericardial effusion before and after the procedure, and in some cases to guide transseptal puncture. After transseptal puncture, patients received intravenous heparin to maintain an activated clotting time of 250 to 350 seconds. Three-dimensional electroanatomic mapping of the left atrium and PVs was performed using an 8-mm tip, a 4-mm tip ablation nonirrigated NaviStar catheter or a 3.5-mm tip ablation irrigated ThermoCool NaviStar (Biosense Webster, Inc., Diamond Bar, CA) and CARTO (Biosense Webster, Inc.) recording systems. Radiofrequency ablation was performed outside the PV ostium near sites with the earliest PV electrograms during pacing or AF. Radiofrequency energy was delivered in the temperature control mode, with a temperature limit of 55°C and a power limit of 50 W for the 4-mm tip catheter and 52°C and 50 to 70 W for the 8-mm tip catheter. Irrigated radiofrequency energy was delivered with a temperature limit of 42°C, a maximal power of 30 W, and an infusion rate of 17 ml/min. The process was repeated until complete bidirectional electrical PVI was achieved. All PVs were routinely isolated for all patients. After PVI, induction of AF was attempted by burst pacing at 200 ms for 5 seconds from the right atrium and twice from the coronary sinus. AF that did not terminate spontaneously was electrically cardioverted. Isolation of PVs was reassessed in all patients, and if reconnection was observed, the vein was reisolated. Isoproterenol (up to 10 μg/min) was then administered to assess triggers and reconnection, after which the attempt at induction of AF by burst atrial pacing was repeated. If reconnection was observed with isoproterenol, the vein was reisolated. If AF was inducible, the effectiveness of PVI was again reevaluated with the circumferential catheter, and any observed electrical reconnection was ablated. Reinduction of AF was attempted in patients who underwent further ablation to reisolate reconnected PVs. Inducibility was defined as induction of AF or atrial tachycardia (AT) (after the final ablation to achieve PVI) lasting >10 seconds. No additional left atrial lines were performed in patients without inducible AF or AT after PVI. Left atrial ablation lines (roof line, mitral isthmus line, and/or posterior left atrial line) or ablation of extra-PV atrial triggers (such as the superior vena cava, coronary sinus os musculature, and vein of Marshall) ablation were performed in patients with inducible sustained AF or AT at the operator’s discretion, on the basis of electroanatomic mapping information obtained during the induced arrhythmia. Mitral isthmus and roof lines were attempted in patients with inducible sustained AF or AT only if sequential activation in the coronary sinus catheter suggested roof or isthmus participation. No attempt was made to assess the completeness of the lines, as judged by the absence of a continuous line of split potentials. A right atrial isthmus line (tricuspid valve to inferior vena cava) was performed only in patients with histories of or inducible right atrial isthmus–dependent flutter.

Patients were treated with warfarin to achieve an international normalized ratio of 2.0 to 3.0 for ≥6 months, as well as acetylsalicylic acid (81 to 325 mg/day) for ≥1 month (in 60% of patients). Antiarrhythmic drugs were continued after the procedure in patients with histories of persistent or longstanding persistent AF and were reinitiated in patients with early (<30 days) recurrence of AF. Repeat magnetic resonance imaging or computed tomography was performed 4 to 6 weeks after the procedure to assess for PV stenosis and repeated at 3 and/or 6 months, if significant narrowing was observed. Patients without AF recurrence for ≥3 to 6 months were progressively weaned off antiarrhythmic drugs and, according to the risk profile of the patient, off oral anticoagulation.

Evaluation of symptomatic or asymptomatic AF or AT was performed using a 1- to 3-week continuous loop event recorder at 1, 3, 6, and 12 months. During the first month after the procedure, all patients underwent loop recording with transmissions 3 times daily without symptoms and if any symptoms occurred. Beyond the first year of follow-up, patients returned for clinical evaluation in the outpatient clinic at least once a year (usually every 6 months for 2 years), and every effort was attempted to retrieve clinical and electrocardiographic information from the patients enrolled in the study approximately every 6 to 12 months. Long-term monitoring by their primary care practitioners was requested and often was done at least once a year without symptoms and any time it was appropriate.

Recurrent AF was deemed present if an asymptomatic or symptomatic atrial tachyarrhythmia consistent with AF or AT was documented to last >10 seconds. Freedom from AF was defined as no detected episode of symptomatic or asymptomatic AF or AT beyond 30 days after the procedure (blanking period).

Patients with symptomatic AF recurrence beyond the blanking period of 1 month were offered to repeat a catheter ablation of AF, only if class I or III antiarrhythmic drugs or rate-control agents were still inefficacious to prevent or treat the symptoms or if the patients were reluctant to take any of these medications. Repeat procedures consisted in the same stimulation and ablation protocol as in the index procedure.

Continuous variables are reported as mean ± SD or as medians and interquartile ranges (25th and 75th percentiles), and categorical variables are expressed as numbers and relative percentages. Predictive analysis of recurrence over the follow-up time was assessed through the Cox regression method. The multivariate stepwise regression model was used adjusting for clinical variables with p values <0.05 in the univariate analysis. The hazard ratio and its 95% confidence interval were retrieved from the model. Kaplan-Meier event-free survival analysis was conducted to assess the cumulative freedom from AF or AT recurrence. Probability of AF recurrence according to AF type was determined using Kaplan-Meier analysis with the Mantel-Cox (log-rank) test. A p value <0.05 was considered statistically significant. SPSS version 11.0 (SPSS, Inc., Chicago, Illinois) was used for statistical analysis.

Results

A total of 249 patients underwent catheter ablation of AF from January 2002 to December 2006 at our center. One hundred three patients who were first-time ablation patients and strictly followed in our AF clinic for >4 years constituted the study group. The median follow-up period was 6 years (interquartile range 4.88 to 7.27). Clinical and demographic details are listed in Table 1 . The remaining 146 patients were excluded from analysis because of insufficient data or follow-up. For the most part, this was due to patient and/or primary care physician preference, primarily because of a “perceived” good clinical outcome or, less frequently, because the primary care physician assumed responsibility of adjusting therapy. In the absence of significant monitoring or other data, we believed that these patients should not be included.

Seventy-six percent of the patients were men, the mean age was 53 ± 13 years (median 55), most patients had persistent or chronic AF (61%), and 20% had already undergone cavotricuspid isthmus ablation. Every patient received ≥1 antiarrhythmic drug before undergoing catheter ablation of AF. All patients had event recorders for the first month after PVI, and all patients had ≥2 episodes of 1- to 3-week continuous monitoring (mean 2.8). Beyond the first year, all patients returned in person to the Beth Israel Deaconess Medical Center at least once a year, obtaining an average of electrocardiographic or Holter recordings of 8.64 per patient (1.44 per patient per year).

In all, 153 procedures were performed, with a median of 1 (interquartile range 1 to 2) per patient as follows: 61 had 1, 35 had 2, 6 had 3, and 1 had 4 catheter ablations. Figure 1 shows the temporal distribution of all the procedures (index and repeat ones) and of AF or AT recurrence. Only 2 patients had very short recurrences, lasting <1 minute. The main indication for a repeat intervention was AF (72% of the patients); atrial flutter or AT was an indication for repeat catheter ablation in 28% of the patients who underwent >1 procedure. Of the 80 patients who had arrhythmic recurrences after the first procedure, 68 (85%) were symptomatic and 61 (76%) had AF recurrence, whereas among the remaining 19 (24%), AT (or atrial flutter) was the cause of recurrence. Forty-two patients underwent second procedures, 27 of whom had arrhythmic recurrences: 19 (70%) had AF, while in 8 (30%), AT or atrial flutter was the cause of recurrence. Seven patients underwent a third PVI procedure (2 because of AF and 5 because of AT, all symptomatic): 4 remained free of any atrial arrhythmia, while 3 patients had recurrences of AT (1 of whom underwent a fourth intervention). The average time to recurrence was 1.33 years after the first procedure and 0.68 years after the second procedure. Antiarrhythmic drugs were weaned off after 62 procedures (40% of all procedures), with recurrences off all antiarrhythmic drugs occurring in 54 of 62 (87%).

Study flow chart. FUP = follow-up; IQR = interquartile range; pts = patients.

Table 2 lists procedural characteristics. Bleedings accounted for most complications, with major bleeding occurring in 4% of procedures (there was 1 retroperitoneal bleed, 1 subcutaneous lower abdominal bleed, and 2 large groin hematomas during heparin bridging). There were no procedure-related deaths. One case of cardiac tamponade was successfully managed by pericardiocentesis and reversal of the periprocedural anticoagulation. Lasso catheter entrapment in the mitral valve requiring cardiac surgery occurred in 1 patient with a flail mitral leaflet. No deaths, cerebrovascular events, or symptomatic PV stenoses were reported during follow-up.

Freedom from asymptomatic or symptomatic AF or AT was present in 51% of patients at 1 year, 40% of patients at 2 years, 32% of patients at 4 years, and 23% of patients at 6 years ( Figure 2 ) . Most recurrences occurred in the first year, as shown in Figure 2 . After a single procedure, in Cox regression analysis, several variables that predicted long-term AF or AT recurrence (including AF duration, body mass index, and left atrial size as continuous variables and nonparoxysmal AF as a binary variable) in the univariate model lost their independence in the multivariate model ( Table 3 ).

Kaplan-Meier arrhythmia-free survival curve after single catheter ablation of AF.

Table 3

Results of univariate and multivariate Cox proportional-hazards analysis to recognize clinical variables associated with arrhythmia recurrences after a single catheter ablation

Variable	Univariate Analysis			Multivariate Analysis
	HR	95% CI	p Value	HR	95% CI	p Value
AF duration	1.00	1.0001–1.0063	0.04	1.00	0.99–1.00	0.52
Age	1.00	0.99–1.02	0.32
Body mass index	1.04	1.00–1.08	0.03	1.03	0.96–1.12	0.31
Male gender	0.86	0.52–1.42	0.55
Nonparoxysmal AF	1.80	1.11–2.89	0.01	1.24	0.63–2.46	0.52
Hypertension	1.33	0.86–2.08	0.19
Coronary artery disease	1.57	0.75–3.26	0.23
Diabetes mellitus	1.96	0.85–4.55	0.11
Obstructive sleep apnea	1.54	0.90–2.63	0.11
Left atrial size	1.04	1.00–1.08	0.02	1.02	0.98–1.07	0.23
AF inducibility	1.44	0.87–2.37	0.15

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