 Introduction/Background Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting 3% of the population [1,2], predisposing to circulatory stasis and formation of left atrial (LA) thrombi, mostly in the LA appendage (LAA) [1,3,4]. Endovascular treatment of AF continues to evolve, with favorable outcomes. Catheter ablation eliminates the electrical connection between the left atrium and ectopic pulmonary venous arrhythmogenic foci [5] and can be used to eliminate substrate for reentry within or adjacent to areas of LA fibrosis [6]. Imaging for preprocedural planning for LA ablation has been shown to improve success rate of procedures, minimize complications, exclude contraindications for the procedure, and minimize the risk of AF recurrence [7]. Endovascular device occlusion/closure of the LAA is used to reduce LAA thrombi from embolizing into the systemic circulation [8-10]. Cardioversion aims to restore a patient to normal sinus rhythm, and in such patients, precardioversion imaging is used to exclude the presence of LAA thrombus because up to 7% of patients have atrial thrombi despite anticoagulation regimens [7]. The document discusses imaging guidelines for the following preprocedural clinical tasks in patients needing endovascular treatment or cardioversion of AF: 1) before catheter ablation, to determine the anatomy of the pulmonary veins, the size of their ostia if using balloon technology, and to determine the relationship of the left atrium to adjacent structures (such as the esophagus) to minimize complications and exclude thrombi; 2) before LAA occlusion to assess LAA morphology and dimensions for device selection, exclude LAA thrombi, assess LAA relationship to adjacent cardiac, and extracardiac structures to aid in determining feasibility and preprocedural planning; and 3) before cardioversion, to exclude LA/LAA thrombi. aUniversity of Michigan, Ann Arbor, Michigan.
Preprocedural Planning for Left Atrial Procedures in Atrial Fibrillation.  Introduction/Background Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting 3% of the population [1,2], predisposing to circulatory stasis and formation of left atrial (LA) thrombi, mostly in the LA appendage (LAA) [1,3,4]. Endovascular treatment of AF continues to evolve, with favorable outcomes. Catheter ablation eliminates the electrical connection between the left atrium and ectopic pulmonary venous arrhythmogenic foci [5] and can be used to eliminate substrate for reentry within or adjacent to areas of LA fibrosis [6]. Imaging for preprocedural planning for LA ablation has been shown to improve success rate of procedures, minimize complications, exclude contraindications for the procedure, and minimize the risk of AF recurrence [7]. Endovascular device occlusion/closure of the LAA is used to reduce LAA thrombi from embolizing into the systemic circulation [8-10]. Cardioversion aims to restore a patient to normal sinus rhythm, and in such patients, precardioversion imaging is used to exclude the presence of LAA thrombus because up to 7% of patients have atrial thrombi despite anticoagulation regimens [7]. The document discusses imaging guidelines for the following preprocedural clinical tasks in patients needing endovascular treatment or cardioversion of AF: 1) before catheter ablation, to determine the anatomy of the pulmonary veins, the size of their ostia if using balloon technology, and to determine the relationship of the left atrium to adjacent structures (such as the esophagus) to minimize complications and exclude thrombi; 2) before LAA occlusion to assess LAA morphology and dimensions for device selection, exclude LAA thrombi, assess LAA relationship to adjacent cardiac, and extracardiac structures to aid in determining feasibility and preprocedural planning; and 3) before cardioversion, to exclude LA/LAA thrombi. aUniversity of Michigan, Ann Arbor, Michigan.