4.4 Implications for LAPW isolation
Reducing the ablation power and duration of radiofrequency application was commonly performed during LAPW ablation in an attempt to avoid excessive damage to the esophagus. However, taking these measures was empirical, and the ability of the procedure to ensure safety was hard to demonstrate due to the very low incidence of AEF. Thus, we envisaged that it might be safer to perform MPL instead of CPL since MPL was relatively farther from the esophagus than CPL; moreover, we considered the higher presence of the fat pad might protect the esophagus from ablation injury.12 The electrical isolation of the LAPW by linear lesions is always technically difficult because of the complex structure of the LA musculature and the unavoidable gaps in the ablation line.20 For the goal of electrically isolating LAPW, more energy is expected to be delivered on the ablation line. Lee et al.21 reported that the achievement of the bidirectional block of the CPL in LAPW isolation was not mandatory due to the risk of esophageal injury and that additional LAPW focal ablation was needed. McLellan et al6 reported a similar adjunct radiofrequency ablation at the midportion of CPL by using adenosine challenge. It was predictable that the risk of esophageal injury might be increased by the adjunct ablation on CPL. Further, the MPL ran much inferior, compared with CPL, where the inferior left ganglionated plexi (GP) and inferior right GP were anatomically located,22 hence, it is possible that a modification effect of GP might reduce AF recurrence when MPL is performed. One of the predisposing factors of AEF has been suggested, which is a thin posterior LA wall with reduced soft tissue between the esophagus and the LA in slim patients.23 In view of the thicker LAPW myocardium and fat pad in the course of MPL, we found it relatively safer to perform MPL instead of CPL.