Function of the left atrial appendage (LAA) represented by LAA outflow is an important predictor for thrombus formation in patients with nonrheumatic atrial fibrillation, but the pattern of LAA flow in patients with complete atrioventricular (AV) block has rarely been studied. Twenty-one patients with complete AV block and an implanted WI or WIR pacemaker were studied with transesophageal echocardiography. The LAA outflow velocity obtained during the ventricular diastolic phase was significantly higher than that obtained during the ventricular systolic phase (41.5 ± 6.0vs. 34.9 ± 9.7cm/s; p < 0.001). The LAA inflow velocity obtained during the ventricular diastolic phase was also significantly higher than that obtained during the ventricular systolic phase (29.9 ± 7.8 vs. 26.4 ± 5.3 cm/s; p < 0.01). In addition, the LAA outflow and inflow velocity time integrals during the ventricular diastolic phase were significantly higher than those during the ventricular systolic phase (4.66 ± 0.96 vs. 4.08 ± 1.05 cm, p < 0.01, and 2.81 ± 0.77 vs. 2.56 ± 0.65 cm, p < 0.05, respectively). Thus, due to both diastolic augmentation of the LAA flow related to active atrial contraction and minor early diastolic LAA flow formation, left ventricle diastolic function might have some influence on LAA flow. This may have implications for the pathogenesis of LAA thrombi in left ventricular dysfunction.