The left atrial appendage is a small organ attached to the left atrium of the heart. During normal heart function, as the left atrium constricts and forces blood into the left ventricle, the left atrial appendage does the same. The ability of the left atrial appendage to contract assists with improved filling of the left ventricle, thereby playing a role in maintaining cardiac output. However, in patients suffering from atrial fibrillation, the left atrial appendage may not properly contract, causing stagnant blood to pool within its interior, which can lead to the undesirable formation of thrombi within the left atrial appendage. As the heart beats, blood from the left atrial appendage, instead of being actively expelled by contraction of the left atrial appendage, may be pulled out of the left atrial appendage via suction effect created by the expansion of the left ventricle, thereby pulling thrombi into the blood stream. Thrombi forming in the left atrial appendage may contribute to stroke. As a treatment, medical devices have been developed which close off the ostium of the left atrial appendage, effectively removing the left atrial appendage from the circulatory system and reducing or eliminating the amount of thrombi which may enter the blood stream from the left atrial appendage.
Unfortunately, the left atrial appendage provides certain positive effects and closing the left atrial appendage off has a series of negative side-effects. For example, stretch receptors of the left atrial appendage play a role in mediating thirst in hypovolemia. Effectively eliminating these receptors by closing off the left atrial appendage may cause hypertension. Additionally, the left atrial appendage modulates the relationship between pressure and volume. Left atrial appendage clamping leads to an increase in diastolic transmitral and pulmonary flow velocities, and to an increase in left atrial mean pressure and size. Further still, the left atrial appendage is an endocrine organ which releases atrial natriuretic peptide (ANP). Endothelial cells of the left atrial appendage are specialized in the production and release of natriuretic peptides. In healthy human hearts, atrial natriuretic peptide concentration may be 40-fold higher in the left atrial appendage than in the rest of the atrial free wall and in the ventricles. A continuing need exists for improved medical devices and methods to control thrombus formation within the left atrial appendage of patients suffering from atrial fibrillation while accommodating the positive functionality of the left atrial appendage.