Catheter ablation: technique, indications and arrhythmia-specific outcomes
THE CONTEXT
Catheter ablation identifies and destroys arrhythmia-producing tissue. It is the treatment of choice for SVT or atrial flutter and is useful in selected patients with AF or ventricular arrhythmias.
Mapping and ablation technique
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Catheter electrodes are introduced through the venous system to record cardiac activation during sinus rhythm, tachycardia and pacing manoeuvres.
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After identifying the arrhythmia focus or circuit, such as an accessory pathway in WPW syndrome, a catheter ablates the culprit tissue.
The procedure takes approximately 1–4 hours and does not require general anaesthesia, although some discomfort may occur.
Benefits and complications
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For many arrhythmias, radiofrequency ablation offers the prospect of a lifetime cure and elimination of long-term drug therapy.
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Serious complications occur in fewer than 1% of procedures and include complete heart block requiring pacemaker implantation and cardiac tamponade.
Specific arrhythmias
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Ablation is the treatment of choice for AVNRT and AV re-entrant accessory pathway tachycardias, with cure in around 95% of cases.
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Focal atrial tachycardia and atrial flutter can also be treated with radiofrequency ablation, although some patients subsequently experience AF.
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AF ablation electrically isolates the pulmonary veins, which are usually the arrhythmia trigger. It reduces AF episodes in around 70%–80% of younger patients with structurally normal hearts.
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For permanent AF with poor rate control when drugs are ineffective or not tolerated, a permanent pacemaker can be implanted before AV node ablation. The induced complete AV block allows the pacemaker to assume heart rate control.
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Ablation is often effective for ventricular tachycardia in a structurally normal heart and can be life-saving for refractory ventricular tachycardia caused by ventricular scar or structural disease.