[Biophysical basis and cardiac lesions caused by different techniques of cardiac arrhythmia ablation]

Abstract

Although pharmacological treatment of cardiac arrhythmias remains by far the most widely used, non-pharmacological methods are acquiring an increasing role in their management. This update concerns ablation techniques of the normal and accessory pathways and arrhythmogenic foci and the biophysical basis and the mechanisms of the lesions. A number of energy sources and ablation catheters were used to treat the arrhythmias. Continuous electrical current of fulguration was the first energy source to be used. This required a classical external defibrillator connected to an "active" electrode at the tip of a catheter and to a larger skin electrode ("passive"). The mechanism of ablation in fulguration uses the thermal energy produced at the tip of the electrode. Other mechanisms such as the creation of an electrical field and a sudden increase in pressure ("barotrauma") also play a role. The lesions produced are deep and proportional to the energy, size and form of the electrodes and the form of the electrical current. The radiofrequency current has replaced fulguration in most indications. It uses alternate current with frequencies usually ranging between 350 and 700 kHz delivered between a wide distal electrode (7 F, 4 mm) tip and a skin electrode. They are on small and characterised by the destruction of the cellular architecture by coagulation or dessication related to the hyperthermia. The size of the lesions depends on the amount of energy delivered, the size of electrode and the quality of contact with the cardiac tissues. Other types of ablation are under study but have not yet been shown to be superior to radiofrequency energy.