Radiofrequency Catheter Ablation Targeting the Vein of Marshall in Difficult Mitral Isthmus Ablation or Pulmonary Vein Isolation

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The ligament of Marshall (LOM) is implicated in the initiation and maintenance of atrial fibrillation (AF). Its potential roles include the following: trigger of AF,1 electrical connection between neighboring myocardium and the left pulmonary vein (PV),3 and a source of arrhythmogenic autonomic innervation.3 Thus, the LOM has been suggested as a target of ablation in addition to PV isolation (PVI) in AF catheter ablation.3 The LOM contains varied structures, including fibrous tissue, nervous structures, muscle bundles, and vein of Marshall (VOM). The VOM, the remnant of the left superior vena cava, is a core structure of the LOM and drains into the coronary sinus (CS).6 Traditionally, balloon occlusive CS venography has been performed for visualization of the VOM.6 However, the procedure is inconvenient and carries the risk of vessel dissection due to high pressure during contrast injection inside the CS. Yamada et al. suggested a simple method of CS and great cardiac vein angiography that uses an open‐irrigated radiofrequency (RF) ablation catheter.7 This technique does not require ballooning of the CS or changing sheaths, and can visualize small peripheral branches of the great cardiac vein with reduced risk of CS dissection.7 Although this method has been applied for the visualization of VOM in a recent case report,8 its feasibility and safety have not been well evaluated yet in clinical practice.
Anatomically, the LOM runs obliquely in the left lateral ridge, posterior to the left atrial (LA) appendage, and lateral to the left superior PV. The proximal portions of the muscle tracts connect to the CS myocardial sleeves, whereas the distal portions extend upward into the PV or LA free wall.6 This oblique epicardial pathway may bridge over the mitral isthmus (MI) or left PV circumferential ablation line, making those lesion sets ineffective.4 VOM ablation may eliminate these connections and allow achieving a conduction block over the MI or left PVI ablation line. However, despite this important clinical implication, the benefit of VOM ablation has been evaluated in only a small number of subjects.8 In this study, we assessed the feasibility of VOM venography using an open‐irrigated RF catheter and evaluated the benefit of RF ablation targeting the VOM in cases that failed MI block or PVI.
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