Patients appearing free of atrial fibrillation (AF) based on limited electrocardiographic monitoring/clinical history late after ablation may still have a large silent AF burden and thus have failed ablations and may be at risk of thromboembolism. We evaluated long-term monitoring (LTM; 7 days or 1 year) in 203 patients off antiarrhythmic drugs who were clinically free of AF >1 year after ablation. A 7-day monitor was done in 186 and 17 had pacemakers in whom the most recent year was analyzed. Arrhythmia recurrence was >30 seconds of AF, flutter, or tachycardia. LTM was done 3.1 ± 1.3 years (range 1.1 to 7.3) after the last ablation. AF recurred in only 8 of 186 (4.3%) on 7-day monitoring. One had persistent AF. For the other 7, AF burden was 0.0075% to 3.34% with 3 of 7 having an AF burden ≤0.037%. AF recurred in 4 of 17 patients (23.5%) with pacemakers. The 4 patients with pacemakers and AF had a 1-year AF burden of 0.0037% to 0.16%. Given the longer duration of monitoring, pacemakers detected more AF than 7-day monitors (p <0.011). AF duration before ablation was the only predictor of AF recurrence on LTM (p = 0.01). In patients with symptomatic AF who appeared free of AF on clinical grounds an average of 3 years after ablation, AF burden on LTM was low. In conclusion, monitoring by implanted devices detects more AF than 7-day monitors, most patients exceeding the failure definition of >30 seconds have a small AF burden, and when using LTM for follow-up the definition of “ablation failure” may be better described by an AF burden >0.5% rather than a single 30-second arrhythmia recurrence.
Catheter ablation is a widely accepted treatment for patients with symptomatic atrial fibrillation (AF). Many studies have focused on procedural factors such as techniques of ablation and/or complications. The ultimate goal of ablation is to provide long-term elimination of AF. One previous study of AF ablation suggested a high incidence of silent atrial tachyarrhythmias after ablation, however, many patients were being treated with antiarrhythmic drugs (AADs) and beta blockers. A 2007 Heart Rhythm Society expert consensus statement on catheter and surgical ablation of AF defined AF ablation failure as >30 seconds of AF, atrial flutter, or atrial tachycardia documented on electrocardiographic (ECG) recordings. Documenting long-term elimination of AF in clinical follow-up can be more challenging than documenting freedom from symptoms. Virtually all studies providing long-term AF ablation outcomes have shortcomings. Most have provided outcomes data based on patient telephone interview and/or clinic visits and almost none have provided late long-term monitoring (LTM) ECG data. Many patients are reluctant to undergo LTM late after AF ablation for different reasons including patients’ perception that they are free of arrhythmia and that LTM is superfluous or the lack insurance coverage for LTM. In the present study, we report LTM data from patients who appeared to be free of AF based on clinical follow-up an average of 3 years after AF ablation.
Methods
Subjects were consecutive patients undergoing routine follow-up after ablation for symptomatic AF at Sequoia Hospital, Redwood City, California. All signed written informed consent for their ablations. Data collection was prospective and approved by the hospital’s institutional review board. AF type was categorized as paroxysmal (lasting <1 week), persistent (lasting >1 week to <1 year or requiring pharmacologic or electrical cardioversion in <1 week), and longstanding persistent (lasting >1 year).
Our ablation protocol and anticoagulation strategy have been previously published and some patients in this study were included in previous publications. AADs were stopped ≥5 1/2-lives and amiodarone ≥3 months before ablation. General anesthesia and right femoral venous access were used in most ablations. A 7F duo-decapolar catheter (Live Wire, St. Jude, St. Paul, Minnesota) was placed around the tricuspid valve annulus with the distal poles in the coronary sinus. A 9F Ultra Ice (Boston Scientific, Natick, Massachusetts) catheter guided the transseptal puncture, performed using a 71-cm BRK (St. Jude) or NRG (Baylis, Montreal, Quebec, Canada) needle. Patients had a femoral or radial arterial line. The NavX system (St. Jude) was used in all cases. Before January 2006, we used a closed-tip catheter (Blazer II, Boston Scientific; or 8-mm Celsius, Webster, Diamond Bar, California) and thereafter an open-tip irrigated catheter (3.5-mm Thermocool, Webster; or 4.0-mm Cool Path or Sapphire-Blu, St. Jude). Most irrigated tip catheter ablations were done using 50 W and the technique of “perpetual motion” where the catheter is moved back and forth across a small area and not left at single sites for extended times. All patients underwent circumferential atrial ablation isolating all pulmonary veins and a left atrial (LA) roof-line ablation. Only patients with right atrial or LA isthmus flutter underwent caval–tricuspid or mitral isthmus linear ablation. Many patients had low posterior LA lines and LA complex fractionated atrial electrogram ablations. Some patients underwent ablation in the coronary sinus and/or superior vena cava isolation. After wide-area ablation around all veins, a circumferential mapping catheter (7F Lasso, Webster; or Reflexion Spiral, St. Jude) was used to isolate all pulmonary veins, defined as complete local electrical silence. After May 2010, all patients underwent pacing from pulmonary veins to document exit block. NavX activation and entrainment mapping were used to ablate flutters and tachycardias. Isoproterenol was given and nonpulmonary vein triggers were mapped and ablated.
For each patient we recorded age, gender, AF duration and type, number of AADs failed, and congestive heart failure, hypertension, age, diabetes, stroke (2 points) score, body mass index, strokes/transient ischemic attacks, LA size, and co-morbidities including hypertension, diabetes, coronary artery disease, and cardiomyopathy.
Many patients were treated with AADs during the 3-month blanking period after ablation. Patients transmitted daily ECG strips for 1 month to 3 months after ablation and were seen at 3 months when echocardiography and ambulatory ECG monitoring for ≥24 hours were performed. Initial ablation failures were encouraged to undergo repeat ablation. Patients were seen or contacted frequently from 3 to 12 months and came for a 1-year follow-up with echocardiography and 24-hour electrocardiograph. Thereafter, every 6 to 12 months patients were seen directly or contacted by telephone by research nurses or the attending physician, and arrhythmia records were obtained from hospitals and referring physicians. Patients were advised to call for arrhythmia symptoms and ECG recorders were reissued to them. Late pacemaker AF data were used when available.
During 2011, as we did routine in-office or telephone follow-up surveillance, consecutive patients considered free of AF >1 year after final ablation were encouraged to undergo 1-week of continuous mobile cardiac outpatient telemetry monitoring (CardioNet, Conshohocken, Pennsylvania). This provided continuous documentation of all ECG tracings for a 7-day period. For each patient, we determined the number of hours the monitor was worn and the number of hours the ECG signal was adequate for analysis. Tracings were reviewed by a trained research nurse and uncertainties were adjudicated by 1 of the authors for all episodes of AF, flutter, or tachycardia of any length, heart rates <40 beats/min, pauses >3 seconds, and occurrence of any ventricular tachycardia >3 beats. Duration and ventricular rate of each episode of atrial tachyarrhythmia were recorded. All episode of recurrent AF, tachycardia, or flutter lasting >30 seconds were tabulated and AF burden was the total minutes of these arrhythmias divided by total minutes of monitoring. Patients with implanted permanent pacemakers that quantified atrial high-rate episodes were also evaluated. Atrial high rate was defined as ≥180 beats/min. Devices were interrogated on a regular basis over a 1-year period. Atrial high-rate episodes were reviewed and atrial arrhythmia burden was calculated.
Statistical analysis was done using XLSTAT 2011 (XLSTAT, Paris, France). Continuous data were described as mean ± SD and categorical data as counts and percentage. Cochran–Armitage trend analysis was used to determine a trend to AF recurrence by AF type. Chi-square analysis was done to evaluate number of AF recurrences detected by 7-day versus 1-year monitoring. A single iteration of analysis of variance was used to examine clinical variables of age, gender, LA size, AF type, body mass index, AF duration, number of AADs failed, and presence of diabetes, hypertension, and coronary artery disease to determine independent predictors of AF recurrence on LTM. All tests were 2-sided and a p value <0.05 was considered statistically significant.
Results
Two hundred forty-four consecutive patients who appeared to be clinically free of AF based on symptoms and limited ECG monitoring off AADs were asked to undergo a 7-day LTM during routine follow-up after AF ablation. The offer was rejected by 38 patients and an additional 20 agreed to monitoring, but when the equipment arrived they refused or did not persevere for >24 hours. Thus, 186 (76.2% of patients offered) underwent a 7-day monitor. An additional 17 patients had pacemakers capable of quantifying atrial high-rate episodes. Table 1 presents patients’ clinical characteristics before ablation. There were 151 men (74.4%); average age was 63.1 ± 9.9 years. AF was paroxysmal in 100 patients, persistent in 82 patients, and long-standing persistent in 21 patients. Beta blockers for nonarrhythmic reasons were taken by 36 (18%). LTM was done an average of 3.1 ± 1.3 years (range, 1.1 to 7.3) after the last ablation.
| 1 ablation | 154 (75.9%) |
| 2 ablations | 47 (23.1%) |
| 3 ablations | 2 (1.0%) |
| Age (years) | 63.2 ± 9.8 |
| Women | 52 (25.6%) |
| Duration of atrial fibrillation (years) | 7.3 ± 8.5 |
| Number of antiarrhythmic drugs failed | 1.1 ± 0.9 |
| Average congestive heart failure, hypertension, age, diabetes, stroke (2 points) score | 0.63 ± 0.81 |
| Left atrial size (cm) | 4.2 ± 0.6 |
| Previous stroke/transient ischemic attack | 4 (2.0%) |
| Hypertension | 83 (40.9%) |
| Diabetes mellitus | 13 (6.4%) |
| Dilated cardiomyopathy | 6 (3.0%) |
| Coronary artery disease | 16 (7.9%) |
| Paroxysmal atrial fibrillation | 100 (49.3%) |
| Persistent atrial fibrillation | 82 (40.4%) |
| Longstanding persistent atrial fibrillation | 21 (10.3%) |
For the 7-day monitors, average duration of monitoring per patient was 134 ± 30 hours with 132 ± 30 analyzable hours. Of 186 patients undergoing 7-day monitoring, 178 (95.3%) did not have a single episode of an atrial tachyarrhythmia >30 seconds. Eight (4.3%) had atrial arrhythmia occurrences lasting >30 seconds. Table 2 presents atrial arrhythmia burden in these 8 patients. One patient was in persistent asymptomatic AF throughout the 7 days. The other 7 patients had a total AF burden during the 7 days ranging from 38 seconds (0.6 minute) to 289 minutes. One patient was aware of a 90-minute AF episode and indicated it was the first episode since the ablation. Three patients had a total AF time of ≤3.1 minutes. Total AF burden ranged from 0.007% to 3.35% with 3 of the 8 having an AF burden ≤0.037%. Because 1 patient was symptomatic, only 7 of 186 patients (3.8%) had “silent AF” lasting >30 seconds during 7-day monitoring. Seventeen patients had 1 year of pacemaker data available for analysis. There were no atrial tachyarrhythmias >30 seconds in 13 of 17 (76.5%). Four patients (23.5%) had asymptomatic atrial tachyarrhythmias >30 seconds with a total atrial high-rate time ranging from 19.6 to 863 minutes (total 1-year atrial high-rate burden of 0.0037% to 0.16%; Table 2 ). Compared to the 7-day monitor, 1-year monitoring detected more patients exceeding the 30-second atrial tachyarrhythmia burden (p <0.011).
| Patient | Duration of Monitoring | Number of Episodes | Total Minutes of AF | AF Burden |
|---|---|---|---|---|
| 1 | 142 hours | 1 | 90 | 1.06% |
| 2 | 160 hours | 1 | 2.1 | 0.022% |
| 3 | 137 hours | 1 | 0.6 | 0.0075% |
| 4 | 146 hours | 1 | 58 | 0.66% |
| 5 | 142 hours | 2 | 3.1 | 0.037% |
| 6 | 144 hours | 3 | 289 | 3.34% |
| 7 | 146 hours | 3 | 75 | 0.86% |
| 8 | 144 hours | persistent | 8,640 | 100% |
| Pacer 1 | 1 year | 2 | 19.6 | 0.0037% |
| Pacer 2 | 1 year | 1 | 25.5 | 0.0048% |
| Pacer 3 | 1 year | 1 | 164 | 0.031% |
| Pacer 4 | 1 year | 1 | 863 | 0.16% |
Figure 1 shows results of analysis of variance examining clinical variables to determine independent predictors of AF recurrence on LTM. Although there was a trend for older age to predict more AF recurrences (p = 0.09), only duration of AF before ablation predicted AF recurrence on LTM (p = 0.01).
