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.