Atrial fibrillation catheter ablation

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2] Anahita Deylamsalehi, M.D.[3] Vendhan Ramanujam M.B.B.S [4] Laith Adnan Allaham, M.D.[5]

Overview

In patients with atrial fibrillation where rate control drugs are ineffective and it is not possible to restore sinus rhythm using cardioversion, non-pharmacological alternatives are available. One of the techniques used is called catheter ablation, where the bundle of cells that pace the heart in the atrioventricular node, are destroyed using radiofrequency energy source, the dominant energy source for catheter ablation. Cryoablation has more recently been developed as a tool for atrial fibrillation (AF) ablation procedures. Other energy sources and tools are in various stages of development and/or clinical investigation. There are three classes of indications for using catheter ablation for atrial fibrillation (AF). The cornerstone for most atrial fibrillation ablation procedures are ablation strategies that target the pulmonary veins and/or pulmonary vein antrum while electrical isolation is the goal. Due to high risk of thromboembolism in patients with atrial fibrillation, careful attention and starting anticoagulation in atrial fibrillation patients before, during, and after ablation is important. Moreover, possible complications and adverse effects associated with catheter ablation in atrial fibrillation patients should be considerd.

Indications for Catheter and Surgical Ablation

• The indications of ablation among patients with atrial fibrillation are stratified as class I, class IIa, class IIb, and class III.
• One of the primary indications (class I) of ablation among patients with atrial fibrillation is the presence of symptomatic atrial fibrillation, which is refractory or intolerant to at least one class I or III antiarrhythmic medication.
• Balloon-based ultrasound ablation and laser based ablation systems have also been developed for ablation of atrial fibrillation (AF).

Class I Indications

In symptomatic paroxysmal atrial fibrillation patients who are either refractory or intolerant to at least one class I or III antiarrhythmic medication, catheter ablation is recommended.

Class IIa Indications

• In symptomatic persistent atrial fibrillation patients who are either refractory or intolerant to at least one class I or III antiarrhythmic medication, catheter ablation is reasonable.
• In symptomatic paroxysmal atrial fibrillation patients, prior to initiation of antiarrhythmic drug therapy with either class I or III antiarrhythmic agent, catheter ablation is reasonable.
• In patients who are undergoing surgery for other indications with symptomatic paroxysmal atrial fibrillation, refractory or intolerant to at least one class I or III antiarrhythmic medication, surgical ablation is reasonable.
• In patients who are undergoing surgery for other indications with symptomatic persistent AF, refractory or intolerant to at least one class I or III antiarrhythmic medication, surgical ablation is reasonable.
• In patients who are undergoing surgery for other indications with symptomatic longstanding persistent atrial fibrillation, refractory or intolerant to at least one class I or III antiarrhythmic medication, surgical ablation is reasonable.
• In patients who are undergoing surgery for other indications with symptomatic paroxysmal atrial fibrillation prior to initiation of antiarrhythmic drug therapy with either class I or III antiarrhythmic agent, surgical ablation is reasonable.
• In patients who are undergoing surgery for other indications with symptomatic persistent AF prior to initiation of antiarrhythmic drug therapy with either class I or III antiarrhythmic agent, surgical ablation is reasonable.

Class IIb Indications

• In symptomatic longstanding persistent atrial fibrillation patients who are either refractory or intolerant to at least one class I or III antiarrhythmic medication, catheter ablation may be considered.
• In patients with symptomatic persistent atrial fibrillation prior to initiation of antiarrhythmic drug therapy with a class I or III antiarrhythmic medication, catheter ablation may be considered.
• In patients with symptomatic longstanding persistent atrial fibrillation prior to initiation of antiarrhythmic drug therapy with a class I or III antiarrhythmic medication, catheter ablation may be considered.
• In patients who are undergoing surgery for other indications with symptomatic longstanding persistent atrial fibrillation prior to initiation of antiarrhythmic drug therapy with a class I or III antiarrhythmic agent, surgical ablation may be considered.
• In symptomatic paroxysmal atrial fibrillation patients who are either refractory or intolerant to at least one class I or III antiarrhythmic medication, stand alone surgical ablation may be considered if they have not failed catheter ablation but prefer a surgical approach.
• In symptomatic paroxysmal atrial fibrillation patients who are either refractory or intolerant to at least one class I or III antiarrhythmic medication, stand alone surgical ablation may be considered if they have failed one or more attempts at catheter ablation.
• In symptomatic persistent atrial fibrillation patients who are either refractory or intolerant to at least one tion|class I or III antiarrhythmic medication]], stand alone surgical ablation may be considered if they have not failed catheter ablation but prefer a surgical approach.
• In symptomatic persistent atrial fibrillation patients who are either refractory or intolerant to at least one tion|class I or III antiarrhythmic medication]], stand alone surgical ablation may be considered if they have failed one or more attempts at catheter ablation.
• In symptomatic longstanding persistent atrial fibrillation patients who are either refractory or intolerant to at least one class I or III antiarrhythmic medication, stand alone surgical ablation may be considered if they have not failed catheter ablation but prefer a surgical approach.
• In symptomatic longstanding persistent atrial fibrillation patients who are either refractory or intolerant to at least one class I or III antiarrhythmic medication, stand alone surgical ablation may be considered if they have failed one or more attempts at catheter ablation.

Class III Indications

In symptomatic paroxysmal or persistent or longstanding persistent atrial fibrillation patients, prior to initiation of antiarrhythmic drug therapy with a class I or III antiarrhythmic agent, stand alone surgical ablation is not recommended.

Recommendations Regarding Catheter Ablation Technique

• The cornerstone for most atrial fibrillation ablation procedures are ablation strategies that target the pulmonary veins and/or pulmonary vein antrum.
• While targeting the pulmonary veins, electrical isolation should be the goal.
• Electrical isolation requires, at a minimum, assessment and demonstration of entrance block into the pulmonary vein.
• Monitoring for pulmonary vein reconduction for 20 minutes following initial pulmonary vein isolation should be considered.
• Careful identification of the pulmonary vein ostia is mandatory to avoid ablation within the pulmonary veins.
• If a focal trigger is identified outside a pulmonary vein at the time of an atrial fibrillation ablation procedure, ablation of that focal trigger should be considered.
• If additional linear lesions are applied, operators should consider using mapping and pacing maneuvers to assess for line completeness.
• Ablation of the cavotricuspid isthmus (fibrous tissue in the lower right atrium between the inferior vena cava and the |tricuspid valve) is recommended in patients with a history of typical atrial flutter or inducible cavotricuspid isthmus dependent atrial flutter.
• If patients with long standing persistent atrial fbrillation are approached, operators should consider more extensive ablation based on linear lesions or complex fractionated electrograms.
• It is recommended that radiofrequency power be reduced when creating lesions along the posterior wall near the esophagus.

Radiofrequency Ablation

• In patients with symptomatic paroxysmal atrial fibrillation who did not tolerate medications or when medications are not successful, radiofrequency ablation is recommended.
• To control rate it is possible to destroy the bundle of cells connecting the upper and lower chambers of the heart - the atrioventricular node - which regulates heart rate, and to implant a pacemaker instead.
• A more complex technique, which avoids the need for a pacemaker, involves ablating groups of cells near the pulmonary veins where atrial fibrillation is thought to originate, or creating more extensive lesions in an attempt to prevent atrial fibrillation from establishing itself.
• Ablation is a newer technique and has shown some promise for cases of recurrent atrial fibrillation that are unresponsive to conventional treatments. Radiofrequency ablation (RFA) uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue.
• Radiofrequency energy is delivered by way of a transvenous electrode catheter. The energy emitting probe (electrode) is placed into the heart through a catheter inserted into veins in the groin or neck.
• Electrodes that can detect electrical activity from inside the heart are also inserted, and the electrophysiologist uses these to map an area of the heart in order to locate the abnormal electrical activity before eliminating the responsible tissue.
• Most atrial fibrillation ablations consist of isolating the electrical pathways from the pulmonary veins (PV), which are located on the posterior wall of the left atrium. All other veins from the body (including neck and groin) lead to the right atrium, so in order to get to the left atrium the catheters must get across the atrial septum. This is done by piercing a small hole in the septal wall (transseptal approach). Once the catheter is in the left atrium, the physician may perform Wide Area Circumferential Ablation (WACA) to electrically isolate the pulmonary veins from the left atrium.
• Some more recent approaches to ablating atrial fibrillation is to target sites that are particularly disorganized in both atria as well as in the coronary sinus (CS). The aforementioned sites are termed Complex Fractionated Atrial Electrogram (CFAE) sites.
• It is believed by some that the CFAE sites are the cause of atrial fibrillation, or a combination of the pulmonary veins and CFAE sites are to blame.
• Most tissues exposed to temperatures of 50 C or higher for more than several seconds will show irreversible coagulation necrosis, and evolve into non-conducting myocardial scar.
• The following factors promote the formation of larger lesions and improve procedure efficacy:
  • High power delivery
  • Good electrode–tissue contact
  • Adequate ablation duration
• Significant complications can occur during atrial fibrillation ablation if high radiofrequency power is administered in an uncontrolled fashion.
• The increased risk of atrial fibrillation ablation compared to ablation of other arrhythmias may be attributed to the great surface area of tissue ablated, the large cumulative energy delivery, the risk of systemic thromboembolism, and the close location of structures susceptible to collateral injury, such as phrenic nerve, pulmonary veins, and esophagus.
• Thrombus, char formation and intramural steam pops can also occur.
• Conventional radiofrequency electrodes were employed earlier. But comparative trials against conventional radiofrequency electrodes have demonstrated that irrigated tip and large tip radiofrequency technologies have increased efficacy and decreased procedure duration.

Cryoablation

• Cryoablation is recommended when point by point radiofrequency ablation is not proper in atrial fibrillation patients.
• Cryoablation is a new technique which uses cryothermal energy as an alternative energy source. In cryoablation, tissue freezing coolant, liquid nitrous oxide is delivered under pressure through a catheter where it changes to gas, resulting in cooling of surrounding tissue. Tissue injury results from tissue freezing with a creation of ice crystals within the cell that disrupts cell membranes and interrupts both cellular metabolism and any electrical activity in that cell. Interruption of microvascular perfusion also produces cell death by interrupting blood flow.
• More recently, a number of point-by-point and balloon-based cryoablation systems have been developed.
• Point-by-point cryoablation approach is proved to be associated with low complication rate, but the procedure is lengthy, and the long-term efficacy is limited. This ultimately paved way for the development of a cryoablation balloon ablation catheter.
• Regional blood flow around the tip of the catheter or balloon influences the achievement of optimal cryoablation. Continuous blood flow reduces the chance of achieving a full-thickness cryoablation. Because of this, complete vein occlusion is required during the procedure.

Ultrasound Ablation

• Although radiofrequency ablation and cryoablation are the two standard ablation systems used for catheter ablation of atrial fibrillation today, balloon-based ultrasound ablation have also been developed for atrial fibrillation ablation.
• The first of the balloon ablation systems to be approved for clinical use is the focused ultrasound ablation system that uses high intensity focused ultrasound (HIFU).

Laser Ablation

• Laser balloon ablation could be considered when radiofrequency ablation is not effective or tolerated.
• Balloon based laser ablation system involving a compliant balloon ablation catheter are being developed through which arcs of laser energy are delivered under visual guidance.
• Small clinical trials have demonstrated the safety and effectiveness of this ablation system, which is now approved for use in Europe and is entering a pivotal randomized clinical trial in the United States.

Anticoagulation Strategies

Atrial fibrillation patients are at increased risk of thromboembolism during, immediately following, and for several weeks to months after their ablation. Thus careful attention and starting anticoagulation in atrial fibrillation patients before, during, and after ablation for atrial fibrillation is important to avoid the occurrence of a thromboembolic events.

Pre Ablation

• In patients who have atrial fibrillation for 48 hours or longer or for an unknown duration, three weeks of systemic anticoagulants at a therapeutic level prior to the procedure is required.
• Prior to the ablation procedure a transesophageal echocardiography (TEE) should be performed in them.
• Transesophageal echocardiography (TEE) in atrial fibrillation patients who have sinus rhythm at the time of ablation or patients with current atrial fibrillation who also had atrial fibrillaton for 48 hours or less prior to atrial fibrillation ablation may be considered, but it is not mandatory.
• A left atrial thrombus found during transesophageal echocardiography (TEE) is a contraindication for catheter ablation of atrial fibrillation.
• Catheter ablation of trial fibrillation on a patient who is therapeutically anticoagulated with warfarin should also be considered.

During Ablation

• Heparin should be administered prior to or immediately following transseptal puncture during atrial fibrillation ablation procedures.
• Atrial fibrillation ablation in a patient who is systemically anticoagulated with warfarin does not alter the need for intravenous heparin to maintain a therapeutic activated clotting time (300 to 400 seconds) during the procedure.
• Administration of protamine following ablation to reverse heparin should be considered.

Post Ablation

• In patients who are not therapeutically anticoagulated with warfarin at the time of atrial fibrillation ablation, low molecular weight heparin or intravenous heparin should be used to resume the systemic anticoagulation with warfarin following atrial fibrillation ablation.
• Initiation of a direct thrombin or factor Xa inhibitor after ablation may be considered as an alternative post procedure anticoagulation strategy.
• A reduction in the dose of low molecular weight heparin (0.5 mg/kg) should be considered because of the increased risk of post procedure bleeding following a full dose (1 mg/kg bid).
• Systemic anticoagulation with warfarin or a direct thrombin or factor Xa inhibitor is recommended for at least two months following an atrial fibrillation ablation procedure. But decisions regarding the continuation of systemic anticoagulation for more than two months following ablation should be based on the patients risk factors for stroke.
• Discontinuation of systemic anticoagulation therapy post ablation is not recommended in patients who are at high risk of stroke.
• Patients in whom discontinuation of systemic anticoagulation is being considered should consider undergoing continuous ECG monitoring to screen for asymptomatic atrial fibrillation.

Outcomes and Efficacy of Catheter Ablation

• Efficacy and risks of catheter ablation of atrial fibrillation are areas of active debate.
• A worldwide survey of the outcomes of 8745 ablation procedures demonstrated a 52% success rate (ranging from 14.5% to 76.5% among centers), with an additional 23.9% of patients becoming asymptomatic with addition of an antiarrhythmic medication.
  • In 27.3% of patients, more than one procedure was required to attain these results.
  • There was at least one major complication in 6% of patients.
• A thorough discussion of results of catheter ablation was published in 2007.
  • It notes that results are widely variable, due in part to differences in technique, follow-up, definitions of success, use of antiarrhythmic therapy, and in experience and technical proficiency.

Prevention of Recurrence After Ablation

• NICE guideline updated in 2021 recommends to use antiarrhythmic agents in order to prevent atrial fibrillation recurrence after ablation.
• It is important to consider patient's preference and side effects before starting antiarrhythmic agents.
• 3 months after starting antiarrhythmic agents to prevent atrial fibrillation recurrence, patients should be evaluated and necessicity for continuing antiarrhythmic agents should be assessed again.

Complications of Catheter Ablation

Catheter ablation of atrial fibrillation (AF) is one of the most complex interventional electrophysiologic procedures. Therefore the risk associated with atrial fibrillation (AF) ablation is higher. The following are complications associated with catheter ablation of atrial fibrillation (AF).

• Atrio-esophageal fistula and esophageal injury
• Bleeding
• Cardiac perforation
• Cardiac tamponade
• Deep sternal wound infection/mediastinitis following cardiac surgery
• Gastric motility/pyloric spasm disorders
• Myocardial infarction
• Pericarditis
• Phrenic nerve paralysis
• Pulmonary vein stenosis
• Silent cerebral embolism
• Stroke or Transient ischemic attack (TIA) post ablation
• Unanticipated adverse device effect
• Vagal nerve injury
• Vascular access complications like hematoma, AV fistula and pseudoaneurysm

2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society

Recommendation for Catheter Ablation in HF Referenced studies that support the new recommendation are summarized in Online Data Supplement 7

Class IIb

1.   AF catheter ablation may be reasonable in selected patients with symptomatic AF and HF with reduced left ventricular (LV) ejection fraction (HFrEF) to potentially lower mortality rate and reduce hospitalization for HF.S6.3.4-1,S6.3.4-2NEW: New evidence, including data on improved mortality rate, has been published for AF catheter ablation compared with medical therapy in patients with HF. (Level of Evidence: B-R)

2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation (DO NOT EDIT)

Rhythm Control

AF catheter ablation to Maintain Sinus Rhythm

Class I

"1. AF catheter ablation is useful for symptomatic paroxysmal AF refractory or intolerant to at least 1 class I or III antiarrhythmic medication when a rhythm control strategy is desired. (Level of Evidence: A)"

"2. Prior to consideration of AF catheter ablation, assessment of the procedural risks and outcomes relevant to the individual patient is recommended. (Level of Evidence: C)"

Class III: Harm

"1. AF catheter ablation should not be performed in patients who cannot be treated with anticoagulant therapy during and following the procedure. (Level of Evidence: C)"

"2. AF catheter ablation to restore sinus rhythm should not be performed with the sole intent of obviating the need for anticoagulation (Level of Evidence: C)"

Class IIa

"1. AF catheter ablation is reasonable for selected patients with symptomatic persistent AF refractory or intolerant to at least 1 class I or III antiarrhythmic medication. (Level of Evidence: A)"

"2. In patients with recurrent symptomatic paroxysmal AF, catheter ablation is a reasonable initial rhythm control strategy prior to therapeutic trials of antiarrhythmic drug therapy, after weighing risks and outcomes of drug and ablation therapy. (Level of Evidence: B)"

Class IIb

"1. AF catheter ablation may be considered for symptomatic long-standing (>12 months) persistent AF refractory or intolerant to at least 1 class I or III antiarrhythmic medication, when a rhythm control strategy is desired. (Level of Evidence: B)"

"2. AF catheter ablation may be considered prior to initiation of antiarrhythmic drug therapy with a class I or III antiarrhythmic medication for symptomatic persistent AF, when a rhythm control strategy is desired. (Level of Evidence: C)"

Sources

• 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation

References

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