4) Double Potential Mapping : A Novel Technique for Locating the Site of Incomplete Ablation

Objectives : In atrial fibrillation (AF) surgery, whereas pulmonary vein isolation can be easily tested by pacing and sensing across the ablation line, verification of linear ablation on the atrial free wall requires activation mapping and considerable time to draw isochronal maps. Double potentials recorded by bipolar electrodes straddling the ablation line should identify the site of incomplete ablation without analyzing the activation maps. The purpose of the study is to examine the feasibility and efficacy of the double potential mapping for locating the site of an incomplete ablation in AF surgery. Methods : To examine if double potential mapping locates the site of incomplete ablation, bipolar electrograms were recorded using 11 custom-made bipolar electrodes (intra-electrode distance = 10 mm, inter-electrode distance = 3 mm) straddling the ablation line created by a bipolar radiofrequency ablation device on the right and left atria in 5 canines. A linear ablation was made with the ablation device, of which one jaw was inserted into the atrium through a purse string suture. A 3 mm width tape was placed on both jaws 10 mm from the tip of the ablation electrode to intentionally create an incomplete ablation lesion. The electrograms were recorded during continuous pacing 5, 10, 20, and 30 minutes after ablation. The activation times at each dipole across the ablation line were determined as the times of the maximum positive and negative derivative of the double potentials. The site of incomplete ablation was determined as the site of the earliest activation across the linear ablation. Results : The double potential mapping located the site of incomplete ablation within one minute without displaying any activation maps. The mapping method is quick and the result is shown on a real-time basis with fewer electrodes. Conclusions : The double potential mapping quickly and precisely locates the site of incomplete ablation on a real-time basis, with fewer electrodes and sufficient accuracy, without drawing any activation maps.