ABSTRACT
Introduction Arrhythmia management has had a chequered history. Only relatively recently have the shortcomings of antiarrhythmic drug therapy been recognized. Antiarrhythmic surgery and the implantable cardioverter defibrillator were born out of the disillusionment with drug options. Surgery was developed for the management of the arrhythmias of Wolff-Parkinson-White (WPW) syndrome and has also been applied extensively to the management of sustained post infarction ventricular tachycardia. A successful surgical attack on an arrhythmia demands detailed knowledge of the arrhythmia anatomy. Intraoperative mapping has revealed that many arrhythmias arise from an apparent point source. A focal arrhythmia may be due to different mechanisms such as re-entry or abnormal automaticity, but irrespective of the mechanism the essence of interventional antiarrhythmic strategies is finding the small well-defined zones of cardiac tissue crucial to the maintenance of the arrhythmia. While WPW surgical techniques involved, by present criteria, extravagant dissection of around 50% of the mitral or tricuspid annulus and while directional current (DC) ablation traumatized tissue many centimetres away from the electrode tip, radio frequency (RF) ablation achieves the same results with lesions of between 5 and 10 mm in diameter. Thus RF ablation has forced a major re-evaluation of arrhythmia management and cardiac mapping. RF ablation is indicated for the management of accessory pathway arrhythmias, atrioventricular junctional re-entry tachycardias, true atrial tachycardias, atrial flutter and some forms of ventricular tachycardia. It also has a role in the management of
Principles of RF production Tissue heating by RF energy delivery occurs at sites of high current density where there is high tissue impedance.1 Heat is generated in the thin rim of tissue in direct contact with the catheter electrode and is then conducted passively to deeper tissues. The temperature rises rapidly at the tip but much slower in deeper tissues. Irreversible tissue injury occurs at temperatures >52°C.
