Catheter ablation (CA) involves placing an ablation electrode at the myocardial tissue associated with arrhythmias. Energy sources such as radiofrequency, cryoablation, pulsed electric fields, laser, and microwave are used to destroy the tissue, altering its automaticity and conductivity to treat arrhythmias. Radiofrequency catheter ablation (RFCA), introduced clinically in 1989, is the most common method for treating tachyarrhythmias. For atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia, and paroxysmal atrial fibrillation, catheter ablation is a safe and effective first-line treatment.
In different energy-based catheter ablations，radiofrequency ablation heats the catheter tip for ablation; cryoablation uses a balloon to release a cryogen (liquid nitrous oxide or liquid nitrogen) to freeze surrounding tissues; pulsed electric field ablation has recently been applied clinically, with its efficacy and safety still under evaluation; and laser and microwave energy sources are still in research or clinical exploration stages.
Indications
Supraventricular tachycardia
- Patients with atrioventricular nodal or atrioventricular reentrant tachycardia
- Symptomatic supraventricular tachycardia unresponsive to antiarrhythmic drugs, including focal or multifocal atrial tachycardia, and atrial flutter
Atrial fibrillation
- Symptomatic paroxysmal atrial fibrillation
- Persistent atrial fibrillation poorly responsive or intolerant to drug therapy
- Symptomatic atrial fibrillation with reduced left ventricular ejection fraction
Ventricular arrhythmias
- Symptomatic frequent premature ventricular contractions originating from the right ventricular outflow tract without structural heart disease, unresponsive or intolerant to antiarrhythmic drugs
- Recurrent polymorphic ventricular tachycardia or idiopathic ventricular fibrillation triggered by identical premature ventricular contractions
Method
Electrodes are placed through conventional venous routes (femoral or subclavian veins) into the high right atrium, His bundle, coronary sinus, and right ventricle to display intracardiac electrophysiological maps of normal cardiac conduction. Programmed electrical stimulation with various electrode catheters is performed to induce arrhythmias and determine their mechanisms. Differential diagnostic techniques, such as entrainment mapping or para-Hisian pacing, may be used as needed. The target site is determined based on the mechanism and accessed through venous or arterial routes (femoral vein or artery) with an ablation catheter. Different ablation techniques are used for various conditions, such as modified slow pathway ablation or linear ablation of critical isthmuses. Atrial fibrillation ablation often involves circumferential pulmonary vein isolation due to its complex mechanisms. Success is confirmed by criteria such as the disappearance of accessory pathway conduction or the inability to reinduce the original arrhythmia.
Complications
Complications of catheter ablation include pericardial effusion/cardiac perforation/cardiac tamponade, atrioventricular block, pulmonary vein stenosis, and left atrial-esophageal fistula/left atrial-pericardial fistula, with a low clinical incidence.