Ablation Options and Anatomical Challenges
The mitral isthmus traditionally refers to the left atrial region
between the mitral valve annulus and the anterior aspect of the left
inferior pulmonary vein (LIPV). However, there are, in fact, multiple
isthmuses to which ablative therapy may be applied to interrupt the
flutter circuit as it circumnavigates the mitral annulus, each
associated with different anatomical advantages and challenges. These
ablation lines are defined as follows (see Figure 1):
- The lateral mitral isthmus line connects the LIPV and the mitral valve
annulus at approximately the 4 o’clock position, lateral to the left
atrial appendage (LAA).
- The anterior mitral line connects the superior aspect of the mitral
annulus and the:
- left superior pulmonary vein (LSPV) septal to the LAA
(‘anterolateral line’)
- roof line (‘true anterior line’)
- right superior pulmonary vein (RSPV; ‘anteromedial line’)
- The superolateral mitral line connects the posterior base of the LAA
orifice adjacent to the LSPV and the mitral annulus.