Abstract 15658: Anatomical Characteristics of the Cavotricuspid Isthmus and Their Correlation With Obstructive Sleep Apnea

Introduction: Macro-reentrant arrhythmias involving the cavo-tricuspid isthmus (CTI) are common in patients with atrial fibrillation (AF). Bidirectional CTI block is the ablation strategy of choice, but it can be surprisingly difficult to obtain at times. Objective: Aim of this study was to systematically assess the characteristics of the CTI to determine its most common anatomical variants to be anticipated for ablation. Methods: This is a prospective observational study in which intracardiac echocardiography (ICE) was used to visualize the CTI of patients undergoing AF ablation. The presence of anatomical variants was recorded, and length was measured along the central CTI in atrial systole. CTI systolic shortening measured in sinus rhythm and defined as: [(diastolic length - systolic length)/(diastolic length)]x100. Results: 180 patients (65±9 years old, 31% female, 37% paroxysmal AF) are included in the study. Mean CTI length was 31±9 mm, with a systolic shortening of 25±13%. A prominent Eustachian ridge was present in 32%, a Chiari network in 11%, and at least one pouch-like recess in 35%, with a mean depth of 5.3±2.5 mm (Figure). A longer CTI was observed in patients with non-PAF compared with patients with PAF (33 vs. 27 mm, P Conclusion: Anatomical variants of the CTI are common and should be anticipated in case of a challenging CTI ablation. A long CTI is associated with OSA and might warrant further clinical screening to identify this common AF comorbidity. CTI systolic shortening correlates with the type of AF and could represent a measure of right atrial contractility.