Radiofrequency Ablation for Cardiac Arrhythmia
The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic drugs, cardioversion-defibrillation,implantable cardioverter-defibrillators (ICDs), pacemakers (and a special form of pacing, cardiac resynchronization therapy), or a combination, is used.
If a tachyarrhythmia depends on a specific pathway or ectopic site of automaticity, the site can be ablated by low-voltage, high-frequency (300 to 750 MHz) electrical energy, applied through an electrode catheter. This energy heats and necroses an area < 1 cm in diameter and up to 1 cm deep. Before energy can be applied, the target site or sites must be mapped during an electrophysiologic study.
Success rate is > 90% for reentrant supraventricular tachycardias (via the atrioventricular [AV] node or an accessory pathway), focal atrial tachycardia and flutter, and focal idiopathic ventricular tachycardia (VT—right ventricular outflow tract, left septal, or bundle branch reentrant VT). Because atrial fibrillation (AF) often originates or is maintained by an arrhythmogenic site in the pulmonary veins, this source can be electrically isolated by ablations at the pulmonary vein–left atrial junction or in the left atrium. Alternatively, in patients with refractory AF and rapid ventricular rates, the AV node may be ablated after permanent pacemaker implantation. RF ablation is sometimes successful in patients with VT refractory to drugs particularly when ischemic heart disease is present.
RF ablation is safe; mortality is < 1/2000. Complications include valvular damage, pulmonary vein stenosis or occlusion (if used to treat atrial fibrillation), stroke or other embolism, cardiac perforation, tamponade (1%), and unintended AV node ablation.