The Left Atrial Appendage in Humans: Structure, Physiology, and Pathogenesis

Nabeela Karim; Siew Yen Ho; Edward Nicol; Wei Li; Filip Zemrak; Vias Markides; Vivek Reddy; Tom Wong


Europace. 2020;22(1):5-18. 

In This Article

Future Directions

Over time, we have come to understand that the LAA is not just an embryological remnant, but a fully functional organ with an important role in cardiac haemodynamics, thrombogenesis, and arrhythmogenesis (Figure 5).

Figure 5.

Summary of the role of the LAA. AA, atrial arrhythmia; AF, atrial fibrillation; LAA, left atrial appendage; TIA, transient ischaemic attack.

Further work is needed to understand the role LAA morphology and flow velocities has on stratification of stroke risk, especially in patients with low CHA2DS2-VASc scores and those deemed to have no stroke risk based on this score. Studies into LAA function in under-represented subgroups such as amongst different ethnic groups, are needed. Similarly, investigations are necessary to determine the role of LAA occlusion in high stroke risk cohorts where anticoagulation is also challenging, such as end-stage renal patients. In addition, studies investigating the long-term effects of LAA closure on left atrial function and how it may affect haemodynamics in HF patients, including HF patients with preserved ejection fraction, are needed.

With regards to nomenclature, LAA occlusion or exclusion is often interchangeable in the literature. However, it is clear that methods of LAA occlusion leading to tissue necrosis (i.e. suture ligation with the LARIAT device or surgical intervention) have implications beyond prevention of thrombosis and include electrical isolation,[120] as well as changes to biomarkers and hemodynamics.[43,45] Therefore, we propose that 'LAA closure' be used as an all-encompassing term, with intervention that results in tissue necrosis referred to as 'LAA exclusion' and only devices that occlude the LAA cavity without affecting the LAA tissue, be referred to as 'LAA occlusion'.

More work is needed into fully understanding the secretion of neurohormonal factors and in particular, the role of the autonomic innervation of the LAA. The effects of LAA exclusion on blood pressure reduction is an area of particular interest, and investigations into underlying neurohormonal mechanisms and clinical impact, are warranted.

Finally, further randomized control trials are needed to investigate the implication of LAA electrical isolation on AF outcomes as well as the need for studies to determine the mechanism in the role of the LAA as a non-pulmonary vein trigger in the generation and maintenance of AF.