Supraventricular tachycardias are quite common in clinical cardiology practice. Medical treatment of supraventricular tachycardias involves regular intake of drugs for several years. Poor efficacy and bothersome side effects of drugs, including proarrhythmia can be a problem. Arrhythmia surgery has largely been replaced by catheter ablation.

Catheter ablation be defined as the sse of an electrode catheter to destroy small areas of myocardial tissue or conduction system, or both, that are critical to the initiation or maintenance of cardiac arrhythmias.

Classification of supraventricular tachycardias

Supraventricular tachycardias can be broadly classified into regular and irregular tachycardias. Atrial fibrillation is the typical irregular supraventricular tachycardia. Catheter ablation of atrial fibrillation is an evolving field and the current discussion will not include the catheter ablation of atrial fibrillation.

The common regular supraventricular tachycardias are atrioventricular nodal reentrant tachycardia (AVNRT), atrioventricular reentrant tachycardia (AVRT) mediated by accessory pathways as in WPW syndrome or Mahaim fibre tachycardia, atrial tachycardia and atrial flutter.

Technique of Ablation

Equipment required for ablation are electrophysiology recorders, programmed stimulators and radiofrequency generators (ablator). Radiofrequency current has been use for catheter ablation since 1989. Two to five multi-polar electrode catheters are used for diagnostic studies. Distal pair of electrodes in each cathter can be used for pacing and delivery of programmed extra extra stimuli for induction of tachycardias. The ablation catheter is usually quadripolar and has a tip electrode with wider surface area for delivery of radiofrequency energy. Up to 50 W of radiofrequency energy is delivered for 30-60 second to produce small burns in the target area which is localised by catheter mapping. Target electrode tip temperature is 60-70°C, which is displayed on the ablator along with the time and impedance.