Ablation for Cardiac Arrhythmia

The decision to treat an arrhythmia depends on its symptoms and its potential severity. 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), catheter ablation, surgery, or a combination, is used.

If a tachyarrhythmia depends on a specific pathway or ectopic site of automaticity, the site can be purposefully destroyed (ablated) to effect a cure (1). Methods of ablation include

• Radiofrequency ablation

• Cryoablation

• Laser ablation

• Pulsed electric field ablation

Radiofrequency ablation is usually accomplished using transvenous catheter supplied low-voltage, high-frequency (300 to 750 MHz) electrical radiofrequency (RF) energy. This energy heats and necroses an area < 1 cm in diameter and up to 1 cm deep.

Cryoablation uses tissue freezing (to -70° C) to effect tissue destruction. Other delivery systems have been developed for intraoperative use.

Laser energy can be delivered using a transvenous catheter to ablate a target area.

Pulsed electrical field ablation uses a train of high voltage, short duration electrical impulses that kill cardiac myocytes in a non-thermal method. The electrical current causes pores to develop in the cell membrane, destroying the cell. Myocytes are more sensitive to this stimulus than many other cells so collateral structures may experience less damage. This ablation technique is sufficiently painful that general anesthesia is required.

Before energy can be applied, the target site or sites must be identified 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 atrial flutter, and focal idiopathic ventricular tachycardia (VT—right ventricular outflow tract, left septal, or bundle branch reentrant VT) (2, 3).

Because atrial fibrillation (AF) often originates in 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. Ablation is sometimes successful in patients with VT refractory to medications, particularly when ischemic heart disease is present.

Transcatheter ablation is safe. Major complications include vascular damage, valvular damage, pulmonary vein stenosis or occlusion (if used to treat atrial fibrillation), stroke or other embolism, cardiac perforation, tamponade, and unintended AV node ablation. Major complication rates range from 0.5 to 1% in straightforward supraventricular ablations to approximately 5% in complex VT ablations (4, 5). Mortality rates range from 0.02 to 0.04% in straightforward supraventricular ablations to 0.5% in complex ventricular tachycardia ablations (4, 5).