Ablation of atrial fibrillation: Facts for the referring physician
ABSTRACT
Radiofrequency ablation has become a safe and effective treatment for atrial fibrillation. We believe that referral to an electrophysiologist for consideration of ablation may allow for better rhythm control and outcomes by altering the natural history of atrial fibrillation progression.
KEY POINTS
- Atrial fibrillation is increasing in prevalence with the aging of the US population and is associated with worsening quality of life and increased risk of stroke, heart failure, and death.
- Atrial fibrillation results in adverse atrial remodeling and fibrosis, eventually leading to persistence of the arrhythmia and making rhythm control difficult.
- Catheter ablation has evolved to be a safe procedure with technologic advancements, especially in experienced tertiary care centers.
- The primary aim of atrial fibrillation ablation is to reduce symptoms and improve quality of life. In theory, it could also decrease the risk of stroke, heart failure, and death, but these outcomes have not been systematically evaluated in a large randomized controlled trial.
PERIPROCEDURAL CONSIDERATIONS
Periprocedural anticoagulation
The risk of thromboembolism is increased during, immediately following, and for several weeks to months after atrial fibrillation ablation.36,37
During the procedure, the risk is related to transseptal sheath placement, electrode catheters in the left atrium, and char formation on ablation catheters. These risks are mitigated with proper and careful sheath and catheter manipulation, maintenance of bubble-free irrigation through lines and sheaths, use of irrigated catheters, and initiation of heparin before transseptal access. Heparin is also infused during the procedure, with close monitoring of activated clotting time.
Postprocedurally, the transiently increased clotting risk could be due to damaged endothelium from the ablation itself and stunning of atrial tissue, which results in impaired contraction. Damaged endothelium improves as the tissue heals, and the stunning resolves by electrical reverse remodeling with sinus rhythm maintenance.
In view of these risks, the referring physician and electrophysiologist must pay careful attention to anticoagulation before and after ablation.
Before the procedure. It is safe to continue anticoagulation uninterrupted through the procedure.38,39 If the patient is on warfarin, we want the international normalized ratio to be in the therapeutic range when we perform atrial fibrillation ablation, and the patient takes his or her usual dose on the day of the procedure. If taking a direct oral anticoagulant, patients typically skip a dose the day before ablation and again on the morning of the procedure, and resume taking it immediately afterward while in the anesthesia recovery room.
During the procedure, we start heparin before transseptal puncture, adjust it to achieve an activated clotting time of 300 to 400 seconds, and keep it in this range as long as there are sheaths or catheters in the left atrium.
After the procedure. The current guidelines24 recommend that oral anticoagulation be continued without interruption for at least 2 months after the procedure, and in most cases indefinitely, depending on age and comorbidities. The decision to stop anticoagulation after 2 months is typically based on the stroke risk as assessed by the CHA2DS2-VASc score (www.chadsvasc.org) and not on the success of the ablation procedure.
ANTIARRHYTHMIC DRUGS AFTER THE PROCEDURE
Some patients actually experience more atrial fibrillation in the first weeks to months after the procedure. The mechanism in this setting may be different from that causing the arrhythmia in the first place. The causes of early recurrence of atrial arrhythmias include postablation inflammation, temporary autonomic imbalance, and delay of atrial radiofrequency lesion formation.40,41 These arrhythmias may completely resolve as the ablation lesions heal and scars mature.
It has been hypothesized that short-term use of antiarrhythmic drugs after atrial fibrillation ablation is effective in preventing arrhythmias because it alters atrial electrophysiologic characteristics induced by the above transient factors. A recent systematic review of 6 clinical trials showed that short-term use of antiarrhythmic drugs reduces the risk of early arrhythmia recurrence but does not reduce recurrence in the long term.42
In terms of outcomes, any arrhythmias that occur in the first 3 months do not necessarily affect long-term success. This is referred to as the “blanking period.” However, generally speaking, it is preferable to maintain sinus rhythm during that time to avoid further anatomic or electrical left atrial adverse remodeling. In many situations, patients continue taking the same antiarrhythmic agent or start on antiarrhythmic therapy in the first few months after ablation.43,44
The mechanisms of late recurrence of atrial arrhythmias after ablation are thought to be different from those in early recurrence. Late recurrence has been ascribed to incomplete pulmonary vein isolation, recovery of pulmonary vein-left atrium connections, or recovery of any other lines of ablation created in the procedure.45,46 For late recurrence of atrial arrhythmia, studies and guidelines suggest that repeat ablation may be an option.24,47
PRACTICAL CONSIDERATIONS FOR PROCEDURAL PLANNING
Before the procedure, some electrophysiologists use cardiac computed tomography or magnetic resonance imaging to evaluate the pulmonary vein anatomy. This helps in planning and in selecting the appropriate tools for the procedure.
The patient is asked to fast on the day of the procedure. The procedure can take 3 to 6 hours, depending on the patient’s anatomy and the operator’s technique and experience. It can be performed with the patient under general anesthesia or conscious sedation. Currently, we use general anesthesia most of the time to maximize patient comfort.
After the procedure, our patients must stay in bed for 4 hours and stay overnight for observation. If no complications arise, they are discharged the next day.
