Atrial fibrillation (AF) is the most frequent sustained cardiac arrhythmia, and in the last decade, catheter ablation has evolved from a nearly experimental and uncertain procedure, to a routine and well established one in many major hospitals around the world.
Despite this fact, symptomatic AF refractory or intolerant to antiarrhythmic medication is the only accepted indication for AF ablation (Class IIb with a level of evidence C) , in daily clinical practice the indications have rapidly expanded. Thereby in those cases in which we expect a great benefit (as in highly symptomatic patients with congestive heart failure and/or depressed ejection fraction [2,3] or a high rate of success (as those with short episodes of paroxysmal AF, without structural heart disease, and normal left atrium size  AF ablation is recommended as first line therapy (table 1).
Main follow-up considerations
When we review published literature regarding outcomes of AF catheter ablation, we must be conscious of the potential factors that may impact outcome, including:
- The type of AF (paroxysmal, persistent or longstanding persistent AF) .
- Epidemiological variables such as age, concomitant cardiac disease, LA size, and comorbidity, such hypertension  or severe obstructive sleep apnoea disease .
- Differences in techniques, follow-up, or definitions of success.
- Differences in the employment of antiarrhythmic drugs.
- Differences in technical proficiency, and so forth.
The Worldwide survey on methods, efficacy and safety of catheter ablation of AF , published in 2005, reported a success rate (defined as freedom from symptomatic AF in the absence of antiarrhythmic therapy) of 52%, with 6% major complications.
Arrhythmic recurrences following AF catheter ablation
Analysis of the results reported in many prospective single centre studies [5,9,10-18], shows that the single procedure efficacy on paroxysmal AF ablation ranges from 38 to 78%, and it usually exceeds 70% when considering multiple procedures. However, reviewing the outcome on persistent AF ablation, success rate of the initial procedure does not reach 50%.
- Definition: in a strict sense, any episode of AF/flutter/tachycardia lasting 30 seconds at least should be considered as a recurrence. In about 45% of the cases this recurrence occurs during the initial 3 months after the procedure despite antiarrhythmic drug treatment, and more than 60% of patients will not present further recurrences during long-term follow-up. There is a general consensus that a blanking period of 3 months should be considered when reporting outcomes and before considering a repeated ablation procedure.
- Clinical success: although for research purposes the definition of recurrence, as well as the time to recurrence of AF are eligible endpoints, it may under-represent the true benefit of ablation, because in many cases there is a significant arrhythmic burden reduction and an evident improvement of symptoms and quality of life.
- Main limitation: the main limitation is that many recurrences are asymptomatic. Various types of monitoring systems can be used to detect recurrences. Obviously, the longer the period monitored, the greater the likelihood of detecting recurrences.
- Post-procedural arrhythmias:
o Early recurrences: 45% of patients present AF recurrence during the first three months of follow-up, however, more than a half will not have any further arrhythmias during long-term follow-up . These early recurrences are probably due to the inflammatory reaction created by multiple RF applications. Atrial tachycardias can be observed in 5-25% of patients after catheter AF ablation , representing at least 10% of the recurrences. In many cases they are self-limited during the initial three to six months of follow-up. Regular atrial tachycardias are usually due to re-entrant arrhythmias using conduction gaps that cross ablation lines. When these tachycardias have a fast ventricular rate, patients can suffer a symptomatic worsening. In these cases our efforts should be focused on restoring sinus rhythm, using electrical cardioversion or controlling ventricular rate.
o Very late recurrences: recurrences occurring after 12 months of follow-up occur in 5% to 10% of patients , and they are commonly due to PVs reconnection. A new ablation procedure is indicated depending on clinical worsening despite antiarrhythmic drugs therapy.
- Practical monitoring recommendations: follow-up of patients should be done monthly for at least three months, and then ideally every six months for at least two years. Each visit should include an ECG, and a 1 to 7 days Holter monitoring is recommended at three to six months intervals for one to two years of follow-up (Figure 1). Patients should be encouraged to document any symptoms on ECGs.
- Arrhythmic recurrences treatment: in order to prevent early arrhythmia recurrences, the consensus is that all patients must continue prior antiarrythmic drugs during the first three months, even if they had been unsuccessful. After three months follow-up, the decision to interrupt drugs depends on the presence or absence of symptoms, cardiomyopathy and the presence of risk factors for recurrence. When recurrences are detected after 3 months follow-up, a repeated ablation procedure should be considered. This is specially true in recurrent regular atrial tachycardias, which are usually refractory to drugs. The procedure should attempt PVs reisolation in most of the patients, being additional linear lesions required only when a macroreentrant mechanism is present . If during the procedure, the PVs are isolated and no atrial tachycardia is present or induced, some groups try to induce AF to determine the presence of sites with atrial fractionated electrograms to ablate them . There is no theoretical maximal number of procedures that can be attempted, but common sense must be applied in order to avoid ineffective repeated ablation procedures and to increase complications rates. Minimally invasive surgical ablation procedures, actually in development, could offer an alternative option for refractory patients, but it still needs to be well established and validated.
- Anticoagulation therapy: a high risk for LA thrombus and thromboembolic events has been shown in patients after an AF ablation procedure. Anticoagulation therapy is recommended for at least two months after the procedure. Discontinuation of anticoagulation therapy appears to be safe in patients without prior history of stroke and with low risk for stroke (CHADS score <2), independently of the presence or type of AF.
Complications of AF ablation during follow-up
Catheter ablation is one of the most laborious electrophysiologic procedures, and although complications rate have decreased with the operators learning curve and technical improvements, major complications are still present in approximately 6% of patients. Even though most of the complications are detected during or immediately after the procedure, some of them will be detected during follow-up.
- Pulmonary vein stenosis: PV stenosis is mainly due to the fibrotic reaction generated by the radiofrequency energy applied. Its prevalence depends on the ablation strategy employed, as well as on its functional characterization [22, 23]. Severe PV stenosis (>70%) can be completely asymptomatic. The best method for diagnosis are CT or MR imaging of the PVs several months after catheter ablation. The most accepted therapy for severe symptomatic PV stenosis is PV angioplasty , opting for surgery in recurrent restenosis or in failed PV stenting.
- Esophageal injury: atrial esophageal fistula is very rare (less than 0,25%)[8,25], but can be devastating if an early diagnosis is not achieved. It usually happens two to four weeks after the procedure, sometimes presenting with a rapid clinical condition deterioration originated by several complications, like multiple gaseous and/or septic embolic events, causing cerebral and myocardial damage, or even death. Early diagnosis (CT or RM imaging) is essential because only a fast surgical intervention can avoid fatal consequences.
- Phrenic nerve injury: this rare (<0,5%) but sometimes dramatic complication can occur when ablating the right superior PV (close to right phrenic nerve) or within the LA appendage (close to left phrenic nerve) [26,27]. Symptoms vary broadly from asymptomatic to severe dyspnea leading to respiratory insufficiency that requires temporary mechanical ventilation support. Although it is usualy transient, in some patients can be permanent.
- Thrombo-embolism: the risk of thrombo-embolism after left atrial
radiofrequency ablation is about 1,1%, with most events occurring within 2 first weeks after the procedure . It can be almost avoided if correct anticoagulation therapy is used.
- Vascular complications: vascular complications are the most common complications, but they rarely generate long-term disability. Their prevalence (up to 13%) can be reduced with technical improvement in femoral access, avoiding long sheaths, using radial artery puncture instead of femoral puncture to monitoryze arterial pressure, and making sure to prescribe correct anticoagulation therapy. Echo-guided manual compression when arterial pseudoaneurism or femoral arteriovenous fistula is detected usually are effective. In patients requiring a continuous anticoagulant regimen, in those with large arteriovenous fistulas or in patients suffering from painful groin hematomas, compression repair is less successful. Percutaneous closure of false aneurysms and arteriovenous fistulas with unsuccessful ultrasonic compression repair can be a useful alternative to surgical treatment .
- Periesophageal vagal injury: catheter ablation on the left atrial posterior wall has been reported to potentially damage the esophagus or periesophageal vagal nerve . This is a rare complication (1%) that appears within the first two days after the procedure. Pyloric spasm and gastric hypomotility produce abdominal bloating and discomfort that can be spontaneously recovered. When persistent, mechanical pyloric dilatation or a local injection of botulinum toxin can be attempted.
- Effects of the radiation exposure during AF ablation: prolonged fluoroscopy is required because of double transeptal puncture and extensive RF applications. Complications due to prolonged radiation are very infrequent, although high accumulated radiation doses can have dramatic consequences. The principal effects are sub-acute skin injuy, genetic abnormalities, with an incidence less than 1 per million cases, and a risk of excess fatal malignancies 0,07% for female and 0,1% for male patients (normalized to 60 minutes of fluoroscopy). The most likely malignancy seems to be lung [31,32]. The efforts of the electrophysiologists should be focused on minimizing the radiation exposure, using very low frame rate pulsed fluoroscopy, and increasing the use of 3D mapping and remote navigation systems that should reduce fluoroscopy time and the need for biplane fluoroscopy, that is beneficial to the patient and to the electrophysiologists who perform AF ablation procedures.
There are other complications, like cardiac tamponade, mitral valve trauma by entrapment of the circular catheter in the mitral vale apparatus, air embolism or acute coronary artery occlusion. All of them occur during the procedure, and require immediate treatment when diagnosed.
To conclude, complications are rare but potentially serious, and careful evaluation should be done in case of symptoms that might be referred by patients. In some cases, due to the rarity of the complication, the treatment is not well defined, and treatment should be done in highly specialized centres.
Table 1 : Indications for Catheter AF Ablation
Established indication (Class IIb, level of evidence C)
- Symptomatic AF refractory or intolerant to at least one Class 1 or 3 antiarrhythmic medication
- In rare clinical situations, it may be appropriate to perform AF ablation as first line therapy. Exemples : 1) Prolonged pauses after termination of AF and the bradycardia-tachycardia syndrome 2) Patients with complications related to AF.
- Selected symptomatic patients with heart failure and/or reduced ejection fraction.
Figure 1 : General Schedule recommended for the follow-up of AF ablation procedure
from the procedure
|1-3 months*||6 months||12 months||18 months||24 months|
|CT or MR||+|
(*): Anticoagulation can be interrupted if CHADS score < 2.
The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.