The left atrial appendage: from embryology to prevention of thromboembolism

Giuseppe Patti¹*, Vittorio Pengo², Rossella Marcucci³, Plinio Cirillo⁴, Giulia Renda⁵, Francesca Santilli⁶, Paolo Calabrò⁷, Alberto Ranieri De Caterina^5,8, Ilaria Cavallari¹, Elisabetta Ricottini¹, Vito Maurizio Parato^9,10, Giacomo Zoppellaro², Giuseppe Di Gioia¹, Pietro Sedati¹, Vincenzo Cicchitti⁹, Giovanni Davì⁶, Enrica Golia⁷, Ivana Pariggiano⁷, Paola Simeone⁶, Rosanna Abbate³, Domenico Prisco³, Marco Zimarino⁵, Francesco Sofi^3,11, Felicita Andreotti¹², and on behalf of the Working Group of Thrombosis of the Italian Society of Cardiology

¹Institute of Cardiology, Campus Bio-Medico University, Rome, Italy; ²Department of Cardiac, Thoracic and Vascular Sciences, University of Padova, Padova, Italy; ³Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy; ⁴Department of Advanced Biological Sciences, University Federico II, Naples, Italy; ⁵Institute of Cardiology, G. d'Annunzio University, Chieti, Italy; ⁶Department of Medicine and Aging, G. d'Annunzio University, Chieti, Italy; ⁷Division of Cardiology, Department of Cardiothoracic Sciences, Second University of Naples, Naples, Italy; ⁸G Pasquinucci Hospital, Massa, Italy; ⁹Cardiology Unit, Madonna del Soccorso Hospital, San Benedetto del Tronto, Italy; ¹⁰Politecnica Delle Marche University, San Benedetto del Tronto, Italy; ¹¹Don Carlo Gnocchi Foundation, Florence, Italy; and ¹²Department of Cardiovascular Science, Catholic University, Rome, Italy

The left atrial appendage (LAA) is the main source of thromboembolism in patients with non-valvular atrial fibrillation (AF). As such, the LAA can be the target of specific occluding device therapies. Optimal management of patients with AF includes a comprehensive knowledge of the many aspects related to LAA structure and thrombosis. Here we provide baseline notions on the anatomy and function of the LAA, and then focus on current imaging tools for the identification of anatomical varieties. We also describe pathogenetic mechanisms of LAA thrombosis in AF patients, and examine the available evidence on treatment strategies for LAA thrombosis, including the use of non-vitamin K antagonist oral anticoagulants and interventional approaches.

Figure 1 Computed tomography/magnetic resonance imaging of the left atrial appendage. (A–D) Computed tomography three-dimensional volume rendering reconstructions illustrating different left atrial appendage shapes. In (A), a windsock morphology (arrow) with a dominant lobe and an accessory secondary lobe; note the left circumflex coronary artery below the left atrial appendage (curved arrow). In (B), a chickenwing shape, with an evident bend in the proximal part of the dominant lobe (arrow). In (C), a cauliflower morphology (arrow). In (D), a cactus-like shape, with a dominant central lobe and secondary lobes extending from the central lobe in both superior and inferior directions (arrow). (E) Computed tomography image delineating the entire extension of the LAA with a filling defect in the apex consistent with intracavitary thrombus (curved arrow). Left ventricle is indicated. (F) Computed tomography three-dimensional volume rendering reconstruction showing a reduced colour brightness in the apex of the left atrial appendage (curved arrow) due to lack of intracavitary contrast enhancement caused by in situ thrombosis. (G) Left atrial appendage (arrow) on a two-chamber magnetic resonance imaging (magnetic resonance imaging-SSFP sequence). (H) Left atrial appendage with in situ thrombosis (curved arrow) on magnetic resonance imaging.