Inequalities for Left Atrial Ablation.

Abstract

Great teaching value can come from showcasing an unusual phenomenon that serves as an aid to explain how best to approach mundane, common problems. In this installment of teaching rounds, Wakabayashi et al1 use an unusual activation sequence observed along the mitral annular atrial myocardium that was observed after ablation of the mitral isthmus to teach us about the pitfalls created by the complex terrain in the left atrium (LA). See Article Much of what we initially learned about linear ablation is from ablation of the cavotricuspid isthmus for typical right atrial flutter. Although this experience is helpful, we need to be alert to the fact that we cannot equate this relatively simple ablation approach to the complex-interlinked isthmus anatomy in the LA. In their approach to this complex and instructional case, the authors stress the initial importance of pulmonary vein isolation when approaching mitral isthmus–dependent flutter. Unlike the human inferior vena cava, the left lower pulmonary vein does not serve as an anchor point for ablation of the mitral isthmus. This is because of the myocardial sleeves that extend into this pulmonary vein. As a result, to truly anchor the mitral isthmus line and obtain isthmus block at this site, either the ablation needs to go into the pulmonary vein (which would have a prohibitive risk of pulmonary vein stenosis) or the pulmonary vein must be circumferentially isolated with LA ablation. The usual method for determining whether the pulmonary vein is indeed isolated …