An enhanced and objective approach to advancing the classification system for left atrial appendage morphology in atrial fibrillation
Authors: Pongratz J , Dorwarth U , Riess L , Wankerl M , Mohl A , Schlichting A , Rogowski S , Hoffmann E , Straube F 
Published: May 2024

Abstract
The left atrial appendage (LAA) is an important part of the heart that can contribute to the formation of blood clots and the development of arrhythmias. Managing the LAA is crucial in clinical practice. Besides oral anticoagulation, one approach is LAA occlusion, which can reduce the risk of blood clots in selected patients. Another approach is LAA ablation, which has been proposed in addition to pulmonary vein isolation (PVI) and might improve the success of treating atrial fibrillation (AF). Different types of LAA morphology have been identified, and these differences can affect the choice of treatment and strategies for individual patients. To refine current classification system, a new approach has been proposed.
The study utilized an observational single-center trial with blinded retrospective analysis of cardiac computed tomography angiography (CCTA) images from cryoballoon PVI patients. Statistical analysis included baseline characteristics and left atrium/LAA measurements. An LAA bounding box was introduced to enhance the current classification system, particularly focusing on distinguishing "chicken-wing" and "windsock," as well as "cauliflower" and "cactus" morphologies.
From 2012 to 2016 a total of 1.103 patients underwent second generation cryoballoon PVI. Prior to PVI, CCTA was available for 725 (65.7%) patients with sufficient quality for measuring in 473 (65.2%). Mean age was 66.3±9.5 years; Paroxysmal AF was present in 277 (58.6%) participants. The distribution of LAA morphological types was as follows: "windsock" 51%, "chicken-wing" 20%, "cauliflower" 15%, and "cactus" 13%. Inter-rater reliability, assessed using Cohen's Kappa with Landis and Koch criteria, demonstrated substantial agreement (Kappa = 0.69; p&lt;0.001). "Chicken-wing" morphology had the largest LAA volume at 9.9 (7.9; 12.8) mL, followed by "windsock" morphology with an LAA volume of 9.7 (7.7; 13.1) mL. "Cactus" and "cauliflower" morphologies had considerably smaller LAA volumes, measuring 5.4 (4.6; 7.5) mL and 5.6 (4.4; 7.6) mL, respectively.
Bounding box parameters were utilized to distinguish between "windsock" and "chicken-wing" as well as "cauliflower" and "cactus" morphologies. "Windsock" had a maximal LAA depth of 44.3±7.1 mm, while "chicken-wing" measured 40.1±8.6 mm (p&lt;0.001). The sinus values for the bounding box were 0.40±0.06 for "windsock" and 0.44±0.08 for "chicken-wing" (p&lt;0.001). For "cauliflower," the LAA depth averaged 30.42±5.0 mm, whereas for "cactus," it measured 33.4±4.3 mm (p&lt;0.001). The mean sinus of the bounding box was 0.48±0.08 for "cauliflower" and 0.44±0.07 for "cactus" (p&lt;0.05).
The utilization of novel bounding box parameters has the potential to aid in the differentiation between different LAA morphologies, such as 'chicken-wing' and 'windsock', as well as 'cactus' and 'cauliflower', especially in cases where the current classification system may not provide clear distinctions.