From the Guidelines
The atrial appendage, particularly the left atrial appendage (LAA), plays a crucial role in cardiac function, serving as a reservoir for blood and aiding in the regulation of blood pressure through the production of atrial natriuretic peptide (ANP). The LAA's unique structure can, however, promote blood stasis and thrombus formation, especially in conditions like atrial fibrillation, making it a significant factor in stroke prevention strategies 1.
Key Functions of the Atrial Appendage
- Reservoir for blood during ventricular systole
- Contractile structure that helps empty blood into the ventricle during atrial contraction
- Endocrine functions, including the production of ANP, which regulates blood pressure by promoting sodium and water excretion and vasodilation
Clinical Significance
The LAA is considered the most common site for thrombus formation in atrial fibrillation patients, which is why LAA occlusion or exclusion procedures are sometimes performed in patients with atrial fibrillation who cannot tolerate anticoagulation therapy 1. Surgical left atrial appendage occlusion should be considered as an adjunct to oral anticoagulation in patients with AF undergoing endoscopic or hybrid AF ablation to prevent ischemic stroke and thromboembolism. Stand-alone endoscopic surgical closure of the left atrial appendage may be considered in patients with AF and contraindications for long-term anticoagulant treatment to prevent ischemic stroke and thromboembolism 1.
Considerations for LAA Occlusion
- The WATCHMAN device and other percutaneous LAA occlusion devices have shown efficacy in reducing the risk of stroke and systemic embolism, but are associated with periprocedural complications and require careful patient selection 1
- Surgical techniques for LAA exclusion have variable success rates and do not currently allow for the avoidance of oral anticoagulation in patients at risk of stroke 1
From the Research
Function of the Atrial Appendage
The atrial appendage plays a crucial role in the heart's functioning, particularly in relation to atrial fibrillation and thrombus formation. Some key points about its function include:
- The left atrial appendage (LAA) affects body homeostasis via atrial natriuretic peptide and the renin-angiotensin-aldosterone system and plays an important role in atrial compliance 2.
- Approximately 90% of clots in nonvalvular atrial fibrillation (AF) are formed in the LAA, highlighting its significance in thrombus formation 2.
- The LAA is a finger-like extension originating from the main body of the left atrium, and its anatomy and function are crucial in evaluating and assessing patients with AF to determine the risk for cardioembolic complications 3.
Role in Thrombus Formation and Stroke
The atrial appendage is closely linked to thrombus formation and stroke, as evidenced by the following points:
- Atrial fibrillation (AF) increases the risk of thromboembolic stroke via stasis in the left atrium and subsequent embolization to the brain, with the LAA being a common site for thrombus formation 4.
- Oral anticoagulation is effective in preventing strokes secondary to AF, reducing overall stroke numbers by approximately 64%, but the presence of thrombus in the LAA despite anticoagulant therapy is a significant concern 4, 5.
- Left atrial appendage occlusion is a promising approach for preventing stroke in AF patients, particularly those with a high risk of thromboembolic events 2, 4.