The efficacy of oral anticoagulant therapy in reducing the risk of stroke and systemic embolism has been demonstrated in patients with nonrheumatic atrial fibrillation, but anticoagulation may introduce the risk for serious complications or adversely affect the patient's usual activities. Because the left atrial appendage(LAA) is the most likely site of thrombus formation in patients with nonrheumatic atrial fibrillation, evaluation of the LAA function with transesophageal echocardiography(TEE) may be helpful to deterrnine the high risk group for ischemic stroke.

Twenty patients with nonrheumatic atrial fibrillation(group I ), eighteen patients with rheumatic atrial fibillation(group II ) and twenty subjects in normal sinus rhythm without valvular heart disease(group III ) were underwent multiplane TEE examination. We measured maximal and minimal areas, ejection-fraction, and peak contraction and relaxation velocities of LAA. We also observed the presence or absence of thrombus and spontaneous echo contrast (SEC) in the left atrium or LAA.

Maximal area of LAA was larger in group I and II compared with group III but there was no difference between group I and group II. Ejection fraction of LAA was much decreased in group I and II compared with group III. Peak contraction and relaxation velocities of LAA were over 45cm/sec in all cases from group Ill, but there was nearly negligible flow measurable in cases from group II. Patients from group I showed two distinct LAA flow patterns, either well defined saw tooth flow pattem(9 cases) or very low flow pattern like that of group II (11 cases). Therefore, patients from group I could be divided into two subgroups according to LAA flow profile. High flow profile subgroup had clear saw tooth flow pattern and revealed over 20cm/sec of peak contraction and relaxation velocities. The other low flow profile subgroup showed under 20cm/sec of both velocities. LAA ejection fraction was more increased in high flow profile subgroup but not significantly. Ischemic stroke occurred in six patients from group I, and all were in the low flow profile subgroup(p<0.05). SEC was observed in eight cases(73%) of the low flow profile subgroup but in only one case(11%) of the high profile sbugroup(p<0.05). All three cases with LAA thrombus belonged to the low flow profile subgroup.

The assessrnent of LAA function by TEE may be helpful to discriminate the high risk group for the potential ischemic stroke in patients with nonrheumatic atrial firillation.