Stroke is a major cause of morbidity in western society, and an infrequent complication of cardiac surgery. The majority of thromboembolic strokes arise from the left atrium, in particular the left atrial appendage. This study aims to assess the short-term effects of left atrial appendage ligation in terms of postoperative clinical and biochemical parameters; and the long-term effects of left atrial appendage ligation in terms of stroke incidence.

In patients with non-rheumatic atrial fibrillation, the left atrial appendage is the origin of at least 90% of all left atrial clots, and the resulting systemic emboli cause approximately 25% of all strokes. The stroke rate in patients with atrial fibrillation older than 75 years of age is 8.1% per year with one clinical risk factor and is 12% per year at any age in clinical trial populations with a history of prior thromboembolism. Three-year stroke rates in elderly nursing home patients not anticoagulated are in excess of 50% (Atrial Fibrillation Investigators 1994). Anticoagulation is oftentimes withheld due to the perception of excessive risk in case of a fall; even when anticoagulation is prescribed, it is well known that therapeutic levels are not always maintained.

Left atrial appendage obliteration is commonly performed in a variety of cardiac surgical operations. There have been animal studies and theoretical arguments which demonstrate the importance of the atrial appendage in its role to support cardiac output and blood pressure, and modulate thirst and hypercoagulability (Stollberger 2003); however this has been poorly studied and documented in humans in the available literature. BNP and ANP have been shown to increase proportionately with left atrial appendage dysfunction, as have von Willebrands Factor, D-Dimer, and thrombin-antithrombin III complex (Igarashi 2001).

To date, there is not a single randomized controlled trial with adequate follow-up to assess the short- and long-term clinical effectiveness of concurrent prophylactic LAA ligation. This trial will fill that void.

Inclusion Criteria:

• Patients undergoing mitral valve repair or replacement surgery

Exclusion Criteria:

• Patients undergoing concurrent surgical anti-arrythmia procedure
• Heart transplant patients
• Patients with known hematologic hypercoagulability disorder