Radiofrequency ablation has an increasingly important role in the management of cardiac arrhythmias. Ablation involves the destruction of re-entry circuits, which are often caused by a myocardial scar or a developmental anomaly.

Indications¹

The main indications for catheter ablation are:

• Symptomatic supraventricular tachycardia (SVT) due to atrioventricular nodal reentrant tachycardia (AVNRT), Wolff-Parkinson-White syndrome, unifocal atrial tachycardia, and atrial flutter (especially common right atrial forms).
• Atrial fibrillation with lifestyle-impairing symptoms, after inefficacy or intolerance of at least 1 antiarrhythmic agent.
• Symptomatic ventricular tachycardia (VT), especially idiopathic VT.

Other indications for catheter ablation include:

• Symptomatic drug-refractory idiopathic sinus tachycardia
• Lifestyle-impairing ectopic beats
• Symptomatic junctional ectopic tachycardia

Atrial fibrillation

• Atrial fibrillation ablation appears to be more effective than medical rhythm control therapy in carefully selected patients. Ablation is indicated in patients requiring rhythm control who have failed with at least one antiarrhythmic drug.²
• Ablation may be more successful in patients with paroxysmal atrial fibrillation rather than persistent atrial fibrillation.²
• Percutaneous radiofrequency ablation is a treatment option for symptomatic patients with atrial fibrillation refractory to anti-arrhythmic drug therapy or where medical therapy is contra-indicated because of comorbidity or intolerance.³
• Radiofrequency ablation of the atria can be performed via a catheter introduced through a femoral vein or by surgical radiofrequency ablation in patients undergoing concomitant open-heart surgery.⁴
• Cryoablation or high-intensity focused ultrasound (HIFU) ablation may be used in the management of atrial fibrillation for patients undergoing concomitant open heart surgery, e.g. mitral valve replacement or repair.^5,6
• Microwave ablation of the atria for patients with atrial fibrillation can be performed via a catheter introduced through a femoral vein or by surgical microwave ablation in patients undergoing concomitant open-heart surgery.⁷
• In experienced hands, paroxysmal atrial fibrillation can be eliminated in more than 85% of patients by ablation lasting less than 3 hours and with a risk of complications of 1-2%. Success rates are lower for patients with persistent atrial fibrillation.⁸
• However, there are only limited long-term data on the safety and efficacy of ablation therapy for atrial fibrillation ablation.²

Supraventricular tachycardias

• Catheter ablation provides a safe and highly effective treatment for symptomatic patients with supraventricular tachycardia.⁹ Ablation may be considered as first-line in some situations, (e.g. a symptomatic patient with Wolff-Parkinson-White syndrome). However, for patients with rhythm disturbances that are likely to spontaneously resolve (e.g. atrial tachycardia) or unlikely to recur (e.g. a first episode of atrial flutter), ablation would not be appropriate first-line therapy.¹⁰
• The common forms of SVT (e.g. AVNRT, SVT associated with Wolff-Parkinson-White syndrome) are treatable with a success rate up to 95%. Cure rates for unifocal atrial tachycardia and common right atrial flutter are about 90%. Recurrent tachyarrhythmias can occur in the first few months after ablation but these may be curable with a second procedure.
• In one major study, ablation success was particularly associated with ablation at the atrioventricular (AV) junction, AVNRT or left free-wall accessory pathway.¹¹ Recurrence was associated with ablation at the right free wall, postero-septal, septal, and multiple accessory pathways). Complications were more common with associated structural heart disease and the presence of multiple targets. Mortality was increased in the presence of heart disease, lower ejection fraction and with AV junction ablation.
• Catheter ablation of atrial flutter is usually effective, but there is a small risk of recurrent atrial flutter, and also a risk of atrial fibrillation during follow-up.¹²

Ventricular arrhythmias

• Most ventricular arrhythmias result from myocardial scarring, most often caused by myocardial infarction. Ablation is not usually curative but may make the rhythm disturbance easier to control by means of anti-arrhythmic agents or an implantable cardioverter-defibrillator (ICD).
• Idiopathic VT is curable with a success rate of about 80%. Ablation is therefore an alternative to anti-arrhythmic drugs for controlling frequent VT episodes. Ablation of multiple VTs and unstable VTs is often possible, but is usually adjunctive therapy to an ICD in these patients.¹³
• VTs associated with structural heart disease can be treated by catheter ablation but the success rate is much lower (about 50%).

Method

• A cardiac catheter is introduced via the peripheral vascular system. A radiofrequency current is passed through an electrode on the end of the cardiac catheter.
• The lesions created are small, homogeneous, approximately 5-7 mm in diameter and 3-5 mm in depth.¹ This has no effect on cardiac function.
• The procedure may take several hours or even longer. The patient may feel slight discomfort during the ablation.
• Patients appear to be particularly aware of their normal heartbeat after the procedure but this sensation disappears after a period of a few weeks. Patients do not require long-term follow-up if the arrhythmia has been cured.

Contra-indications¹

• Left atrial ablation and ablation for persistent atrial flutter should not be performed in the presence of known atrial thrombus.
• Mobile left ventricular thrombus is a contra-indication to left ventricular ablation.
• Mechanical prosthetic heart valves are generally not crossed with ablation catheters.

Complications¹

• Death (0.1-0.2% of all procedures)
• Cardiac complications, e.g. high-grade atrioventricular (AV) block, cardiac tamponade, coronary artery spasm or thrombosis, pericarditis, valve trauma
• Vascular complications, e.g. retroperitoneal bleeding, haematoma, vascular Injury, transient ischaemic attack or stroke, hypotension, thromboembolism or air embolism
• Pulmonary complications, e.g. pulmonary hypertension, pneumothorax
• Other complications include left atrial-oesophageal fistula, acute pyloric spasm or gastric hypomotility, phrenic nerve paralysis, radiation or electrically induced skin damage, infection at access site, inappropriate sinus tachycardia, pro-arrhythmia
• Initially, successful radiofrequency catheter ablation has a low, long-term recurrence rate (4%). Recurrence of accessory-pathway-mediated tachycardia is observed during the first month. ¹⁴
• Radiation risk is low, but it may be greater than the risk from routine X-rays.
• Ablation of a pathway close to the AV node may require implantation of a pacemaker (less than 1% of cases).
• Cardiac wall perforation is rare and is usually due to catheter manipulation rather than the lesion created by ablation.

Document references

1. Greenberg ML; Catheter Ablation. eMedicine, October 2008.
2. Lubitz SA, Fischer A, Fuster V; Catheter ablation for atrial fibrillation. BMJ. 2008 Apr 12;336(7648):819-26.
3. Percutaneous radiofrequency catheter ablation for atrial fibrillation, NICE Interventional Procedure Guideline (April 2006)
4. Radiofrequency ablation for atrial fibrillation in association with other cardiac surgery, NICE Interventional Procedure Guideline (May 2005)
5. Cryoablation for atrial fibrillation in association with other cardiac surgery, NICE (2005)
6. High-intensity focused ultrasound ablation for atrial fibrillation as an associated procedure with other cardiac surgery, NICE (2006)
7. Microwave ablation for atrial fibrillation in association with other cardiac surgery, NICE Interventional Procedure Guideline (2005)
8. Shah D; Catheter ablation for atrial fibrillation: mechanism-based curative treatment. Expert Rev Cardiovasc Ther. 2004 Nov;2(6):925-33. [abstract]
9. Morady F; Radio-frequency ablation as treatment for cardiac arrhythmias. N Engl J Med. 1999 Feb 18;340(7):534-44.
10. Tracy CM et al; American College of Cardiology/American Heart Association Clinical Competence Statement on Invasive Electrophysiology Studies, Catheter Ablation, and Cardioversion. Circulation 2000;102:2309.
11. Calkins H, Yong P, Miller JM, et al; Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group. Circulation. 1999 Jan 19;99(2):262-70. [abstract]
12. Calkins H, Canby R, Weiss R, et al; Results of catheter ablation of typical atrial flutter. Am J Cardiol. 2004 Aug 15;94(4):437-42. [abstract]
13. Stevenson WG; Catheter ablation of monomorphic ventricular tachycardia. Curr Opin Cardiol. 2005 Jan;20(1):42-7. [abstract]
14. Schlapfer J, Fromer M; Late clinical outcome after successful radiofrequency catheter ablation of accessory pathways. Eur Heart J. 2001 Apr;22(7):605-9. [abstract]

Acknowledgements