Advancing the Classification System for Left Atrial Appendage Morphology in Atrial Fibrillation: An Enhanced and Objective Approach

Janis Pongratz (München)1, U. Dorwarth (München)1, L. Rieß (München)1, M. Wankerl (München)1, A. Schlichting (München)1, A. Mohl (München)1, S. Rogowski (München)1, E. Hoffmann (München)1, F. Straube (München)1

1München Klinik Bogenhausen Klinik für Kardiologie und Internistische Intensivmedizin München, Deutschland


Background: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 and might improve the success of treating atrial fibrillation. Different types of LAA morphology have been identified, and these differences can affect the choice of treatment and strategies for individual patients. In an effort to improve the current classification system, a new approach has been proposed.

Methods: The study employed an observational single-center trial design, incorporating a blinded retrospective analysis of cardiac computed tomography angiography (CCTA) images of patients undergoing cryoballoon PVI. The statistical analysis comprised the analysis of baseline characteristics along with measurement data of the left atrium and the left atrial appendage. Furthermore, an LAA bounding box was introduced and assessed with the aim of enhancing the existing classification system, with particular emphasis on distinguishing between "chicken-wing" and "windsock," as well as "cauliflower" and "cactus" morphologies.

Results: 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; PAF was present in 277 (58.6%) participants. The distribution of LAA morphological types was as follows: "windsock" 51.6%, "chicken-wing" 20.7%, "cauliflower" 15.2%, and "cactus" 12.5%. Inter-rater reliability, assessed using Cohen's Kappa with Landis and Koch criteria, demonstrated substantial agreement (Kappa = 0.69; p<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.

Major bounding box parameters were utilized to differentiate between "windsock" and "chicken-wing" morphologies, as well as to distinguish between "cauliflower" and "cactus" morphologies. The mean maximal LAA depth for "windsock" measured 44.3±7.1 mm, while for "chicken-wing," it was 40.1±8.6 mm (p<0.001). Regarding the sinus of the bounding box, "windsock" had a mean value of 0.40±0.06, and "chicken-wing" had a mean value of 0.44±0.08 (p<0.001). For "cauliflower," the LAA depth averaged 30.42±5.0 mm, whereas for "cactus," it measured 33.4±4.3 mm (p<0.001). The mean sinus of the bounding box was 0.48±0.08 for "cauliflower" and 0.44±0.07 for "cactus" (p<0.05).

Conclusion: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.

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