Two or three physicians are involved during the procedure, for positioning the catheter and for collection, analysis and interpretation of the intracardiac signals obtained during the conventional or computerized cardiac mapping.

 

RF ablation is performed around the orifice of the pulmonary veins (PVs), one by one or two by two, using a low level of energy to avoid narrowing of the vessel or atrial perforation. Veins are successfully isolated in 100% of cases. In paroxysmal AF, PV isolation terminates AF in 60 – 70 % of cases. In other cases, additional ablation is performed at the appropriate sites until termination of AF.

 

Ablation in the right atrium (cavotricuspid isthmus) is also performed systematically (unless previously carried out) to prevent right atrial flutter; in this case, linear block is successful in 99 % of cases.

In persistent AF (lasting > 48 hours or where there is a history of electrical conversion), PV isolation is still the first step but may not be sufficient on its own. The second step is to apply radiofrequency energy to eliminate spots of extrapulmonary vein sources and areas of rapid activity identified by mapping in the left atrium and afferent veins, and sometimes in the right atrium. In the most resistant cases (usually long-lasting AF) the last step is linear ablation analogous to surgical incision. Linear ablation is performed in the left atrium between the two superior PV (roof line) and/or from vein to mitral annulus (mitral 'isthmus') with successful linear block in 90 % of cases. AF that has been chronic for between 1 month and 5 years can be terminated in 85% of cases using the above protocol.

 

Success is dependent on the feasibility of achieving continuous and coalescent cauterizing points to create a complete barrier. Any gap in the line, of even just one millimeter, can allow electrical impulses to cross and thus cancel out the ablation result. A persistent gap is due either to an atrial wall that is too thick or the (unpredictable) recovery of atrial tissue during the 1- to 4-week healing process following ablation.

Pain or discomfort associated with cauterization are controlled by Midazolam and Morphine.