Left Atrial Appendage: Embryology, Anatomy, Physiology, Arrhythmia and Therapeutic Intervention

Known for the pathological connection to atrial fibrillation (AF), the left atrial appendage (LAA) is the most common source of thromboembolism in patients with AF and may be an arrhythmogenic source for the maintenance of AF. Potential interventions of the LAA for stroke prevention have recently been developed through better understanding its anatomy and physiology. Occlusion of the LAA is an alternative to the use of life-long anticoagulation in selected nonvalvular AF cases. The PROTECT-AF (The WATCHMAN LAA Closure Device for Embolic PROTECTion in Patients with Atrial Fibrillation) and PREVAIL (Randomized Trial of LAA Closure vs. Warfarin for Stroke/Thromboembolic Prevention in Patients with Non-valvular Atrial Fibrillation) randomized controlled trials demonstrated that LAA exclusion using the Watchman percutaneous device is not inferior to warfarin. However, the appendage is structurally complex and has considerable morphological variations among individuals, and it can be challenging to generalize the device for all patients. Continued technological developments including occlusion/ligation through epicardial, endocardial, or surgical approaches, as well as operator expertise regarding LAA anatomy, physiology, and pathophysiology, should improve interventional outcomes. Furthermore, the optimal strategy for re-entrant tachyarrhythmias arising from LAA remains unknown. Whereas an observational study suggested that LAA isolation was more effective than focal ablation, LAA isolation may be associated with significant impairments in LAA contractility, predisposing individuals to a risk of thrombosis.