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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. Although the incidence of complications is low, serious complications can occur and include valvular disruption, coronary occlusion, cerebrovascular accident and death.
The main indications for catheter ablation are:
- Symptomatic supraventricular tachycardia (SVT) due to atrioventricular nodal re-entrant 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 one anti-arrhythmic 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.
- The success rate of catheter ablation for atrial fibrillation is superior to the efficacy of anti-arrhythmic drugs. Sinus rhythm is restored in approximately 85% of cases at one year and 52% at five years. Longer duration of atrial fibrillation and increased size of the left atrium increase the risk of recurrence. Ablation is also associated with a complication rate of 2-3%.
Indications for catheter ablation of atrial fibrillation:
- Symptomatic atrial fibrillation refractory or intolerant to at least one anti-arrhythmic medication: recommended for paroxysmal AF, reasonable for persistent AF and may be considered for long-standing persistent AF.
- Symptomatic AF prior to initiation of anti-arrhythmic drug therapy with an anti-arrhythmic agent: reasonable for paroxysmal AF and may be considered for persistent and for long-standing persistent AF.
- Ablation may be more successful in patients with paroxysmal atrial fibrillation rather than persistent atrial fibrillation.
- 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.
- 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.
- Cryoablation or high-intensity focused ultrasound (HIFU) ablation may be used in the management of atrial fibrillation for patients undergoing concomitant open heart surgery, eg mitral valve replacement or repair.
- 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.
- In experienced hands, paroxysmal atrial fibrillation can be eliminated in more than 85% of patients by ablation lasting less than three hours and with a risk of complications of 1-2%. Success rates are lower for patients with persistent atrial fibrillation.
- However, there are only limited long-term data on the safety and efficacy of ablation therapy for atrial fibrillation ablation.
The National Institute for Health and Clinical Excellence (NICE) does not currently recommend percutaneous (non-thoracoscopic) epicardial catheter radiofrequency ablation for atrial fibrillation.
Supraventricular tachycardias and atrial flutter
- Studies of radiofrequency ablation for the treatment of patients with typical atrial flutter and atrioventricular node-dependent supraventricular tachycardia report high efficacy rates and low rates of complications.
- Ablation may be considered as first-line in some situations (eg a symptomatic patient with Wolff-Parkinson-White syndrome). Selective radio frequency catheter ablation of the slow pathway is an ideal method to treat most patients with atrioventricular nodal re-entrant tachycardia (AVNRT). However, for patients with rhythm disturbances that are likely to resolve spontaneously (eg atrial tachycardia) or unlikely to recur (eg a first episode of atrial flutter), ablation would not be appropriate first-line therapy.
- The common forms of SVT (eg 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.
- 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. However, radio frequency catheter ablation is considered to be a relatively safe and effective procedure for the therapeutic treatment of typical atrial flutter.
- 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.
- VTs associated with structural heart disease can be treated by catheter ablation but the success rate is much lower (about 50%).
- 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. 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.
- 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.
- Women should not be exposed to fluoroscopy if there is any possibility that they are pregnant.
- Death (0.1-0.2% of all procedures).
- Cardiac complications, eg high-grade AV block, cardiac tamponade, coronary artery spasm or thrombosis, pericarditis, valve trauma.
- Vascular complications, eg retroperitoneal bleeding, haematoma, vascular Injury, transient ischaemic attack or stroke, hypotension, thromboembolism, air embolism.
- Pulmonary complications, eg pulmonary hypertension (secondary to pulmonary vein stenosis), pneumothorax.
- Other potential 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 and proarrhythmia.
- 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.
Further reading & references
- Tracy CM, Akhtar M, DiMarco JP, et al; American College of Cardiology/American Heart Association 2006 update of the Circulation. 2006 Oct 10;114(15):1654-68. Epub 2006 Sep 20.
- Greenberg ML et al, Catheter Ablation. Medscape, Mar 2011
- Tung R, Boyle NG, Shivkumar K; Catheter ablation of ventricular tachycardia. Circulation. 2011 May 24;123(20):2284-8.
- Management of Atrial Fibrillation, European Society of Cardiology (2010)
- Verma A, Macle L, Cox J, et al; Canadian Cardiovascular Society atrial fibrillation guidelines 2010: catheter Can J Cardiol. 2011 Jan-Feb;27(1):60-6.
- Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation, Heart Rhythm Society, 2012
- Lubitz SA, Fischer A, Fuster V; Catheter ablation for atrial fibrillation. BMJ. 2008 Apr 12;336(7648):819-26.
- Percutaneous radiofrequency catheter ablation for atrial fibrillation, NICE Interventional Procedure Guideline (April 2006)
- Radiofrequency ablation for atrial fibrillation in association with other cardiac surgery, NICE Interventional Procedure Guideline (May 2005)
- Cryoablation for atrial fibrillation in association with other cardiac surgery, NICE (2005)
- High-intensity focused ultrasound ablation for atrial fibrillation as an associated procedure with other cardiac surgery, NICE (2006)
- Microwave ablation for atrial fibrillation in association with other cardiac surgery, NICE Interventional Procedure Guideline (2005)
- Shah D; Catheter ablation for atrial fibrillation: mechanism-based curative treatment. Expert Rev Cardiovasc Ther. 2004 Nov;2(6):925-33.
- Percutaneous (non-thoracoscopic) epicardial catheter radiofrequency ablation for atrial fibrillation, NICE Interventional Procedure Guideline (March 2009)
- Spector P, Reynolds MR, Calkins H, et al; Meta-analysis of ablation of atrial flutter and supraventricular tachycardia. Am J Cardiol. 2009 Sep 1;104(5):671-7.
- Lee PC, Chen SA, Hwang B; Atrioventricular node anatomy and physiology: implications for ablation of Curr Opin Cardiol. 2009 Mar;24(2):105-12.
- 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.
- Rodgers M, McKenna C, Palmer S, et al; Curative catheter ablation in atrial fibrillation and typical atrial flutter: Health Technol Assess. 2008 Nov;12(34):iii-iv, xi-xiii, 1-198.
- Stevenson WG; Catheter ablation of monomorphic ventricular tachycardia. Curr Opin Cardiol. 2005 Jan;20(1):42-7.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
|Original Author: Dr Colin Tidy||Current Version: Dr Colin Tidy||Peer Reviewer: Prof Cathy Jackson|
|Last Checked: 19/07/2012||Document ID: 1739 Version: 23||© EMIS|