Embryology and Anatomy of the Left Atrial Appendage: Why Does Thrombus Form?

Left Atrial Appendage Depth and Tachycardia Bradycardia Syndrome as Important Predictors of Left Atrial Appendage Thrombus in Patients with Nonvalvular Atrial Fibrillation

Background

Atrial fibrillation (AF) is the most common heart rhythm disorder that has been shown to be associated with a significant increase in stroke and systemic embolism risk. The left atrial appendage (LAA) is a finger-like extension originating from the left atrium; the formation of thrombus in LAA is the main reason of stroke and systemic embolism in patients with nonvalvular atrial fibrillation (NVAF). This study is aimed at finding out the risk of left atrial appendage thrombus (LAAT) in patients with nonvalvular atrial fibrillation (NVAF).

Method

We retrospectively examined the clinic and left atrial computer tomography angiography (CTA) features of patients assessed in Zhengzhou No. 7 People's Hospital between January 2020 and January 2021 derivation. Student's t-test, chi-square test, receiver operating characteristics (ROC) curves, and logistic regression analysis were used to identify predictors of LAAT.

Result

Of 480 patients included in the analysis, LAAT was found in approximately 9.2% of all patients. Univariate demographic predictors of LAAT included left atrium top and bottom diameter (LTD), left atrial appendage depth (LAAD), CHA2DS2-VASc, tachycardia bradycardia syndrome (TBS), and nonparoxysmal atrial fibrillation (PAF). In a multiple logistic regression analysis, the independent predictors of thrombus were LAAD > 23.45 mm (odds ratio: 4.216, 95% CI: 1.869-9.510, P = 0.001), TBS (odds ratio: 4.076, 95% CI: 1.655-10.038, P = 0.002), and non-PAF (odds ratio: 2.896, 95% CI: 1.183-7.094, P = 0.02).

Conclusion

In NVAF patients with LAAT, evidence suggested that larger LAAD, non-PAF, and TBS present a high risk of LAAT. This is the first report demonstrating that the LAAD and TBS are associated with LAAT in patients with NVAF.

LARIAT Trial Updates

The thrombus formed within the LAA is responsible for the vast (about 90%) majority of strokes. Anticoagulation, although effective therapy for stroke prevention is not feasible in a significant minority of patients due to various reasons. Two percutaenous LAA exclusion techniques have been developed in an effort to decrease risk for stroke: endocardial closure/plugging of the LAA (Watchman, Amplatzer devices) and epicardial LAA ligation (LARIAT). The aim of this study is to review the trial data to date for the LARIAT device. The LARIAT suture has been used in more than 4500 patients with high success of LAA complete closure (92-100%), mostly in the patients unable to take anticoagulation and in a small minority as antiarrhythmic option. The LARIAT technique has evolved with a change in pericardial access method that resulted in dramatic improvement of safety. LAA closure performance with LARIAT system seems to be similar to Watchman device, with small leaks during follow-up in 6-24% of the cases, which do not to correlate with thrombo-embolic events. LAA has been proven to play an important triggering role in patients with persistent atrial fibrillation. Small studies had shown that LAA ligation with LARIAT could terminate persistent atrial fibrillation and possible improve ablation success. Ongoing aMAZE randomized trial is studying if LAA ligaiton using LARIAT suture leads to improved atrial fibrillation ablation success. Available data suggests that LAA closure using LARIAT epicardial suture is a good alternative for stroke risk reduction in patients who are unable to be on anticoagulation therapy. LARIAT system might improve success of AF ablation for patients with persistent and long persistent AF, pending the results of the ongoing aMAZE trial.

A review of the LARIAT device: insights from the cumulative clinical experience

Atrial fibrillation (AF) is the most common arrhythmic disorder world-wide, accounting for 15 % of all strokes. Management of stroke risk in AF is complicated by intolerance of anti-coagulation (AC) therapy and difficulty maintaining therapeutic range in patients treated with warfarin. The left atrial appendage (LAA) is a source of thrombus in AFrelated thrombo-embolic events and surgical LAA exclusion (LAAO) is commonly performed during cardiac surgery in AF patients. Surgical approaches are limited by a high incidence of incomplete closure with a potential for consequent thrombo-embolic events as well as the morbidity of an open-heart procedure. More recently, percutaneous approaches to LAAO have been developed. The LARIAT device is an epicardial LAA exclusion system that enables percutaneous suture ligation of the LAA via combined, pericardial and trans-septal access. The device has 510k Federal Drug Administration (FDA) clearance for soft-tissue ligation and has been studied in canine models in pre-clinical studies as well as published series of clinical experience with LARIAT LAAO. The history, patient selection, procedural technique and complications of LARIAT LAAO are reviewed here. Additionally, insights and procedural improvements that have been elucidated from clinical series and outcomes from the collective experience are discussed. The LARIAT’s epicardial approach to LAA ligation is unique compared with other percutaneous LAA exclusion devices, however more data regarding device safety and efficacy is needed for the LARIAT to emerge as an established therapy for stroke prevention in AF.