Background
Peri-mitral flutter is a common cause of recurrent tachyarrhythmia
following atrial fibrillation (AF) ablation, accounting for up to 60%
of post-ablation atrial tachycardias (AT)1-5. As with
other atypical atrial flutters, its pathogenesis is dependent on the
presence of abnormal electrical substrate resulting in areas of slow
conduction. Accordingly, while occasionally seen de novo in the
ablation-naïve, the exponential rise in the incidence of peri-mitral
flutter has paralleled the rapid increase in AF ablations being
performed worldwide as well as techniques incorporating substrate
modification beyond pulmonary vein isolation (PVI).6,7The incidence of left atrial flutter steadily increases from
approximately 5% with PVI alone, to about 25% with the addition of
linear lesions and ablation of complex electrograms, to up to 50% with
the extensive stepwise approach to persistent AF
ablation.4,8-11 In the context of frequent recurrence
post cardioversion and generally inadequate control with anti-arrhythmic
drugs, cardiac electrophysiologists are increasingly called upon to
perform catheter ablation for post-procedural peri-mitral flutter. While
successful in eliminating recurrent tachyarrhythmia in the majority of
patients, achieving bidirectional block with catheter ablation is
challenging due to complex anatomic relationships. The importance of
attaining this endpoint has been previously highlighted by the
significant incidence of recurrent atrial flutters when the mitral
isthmus line is incomplete.12 Prior studies report the
majority of re-entrant left ATs post AF ablation traverse prior ablation
lines.13 The aim of this report is to review the
anatomic considerations and approaches to catheter ablation for
peri-mitral flutter.