Aims: This study was undertaken to assess whether slow coronary flow (SCF) is related to low left atrial appendage (LAA) blood flow velocities. Methods: Study subjects consist of 44 patients with SCF and 11 volunteer subjects with normal coronary angiogram. The diagnosis of SCF was made using the TIMI frame count method. The blood flow velocities were obtained by placing a pulsed-wave Doppler sample volume inside the proximal third of the LAA. Results: The mean LAA emptying velocities (MEV) were significantly lower in patients than control subjects (34.5 +/- 9.9 cm/sec vs 84.0 +/- 12.1 cm/sec; P < 0.001). In bivariate analysis, significant correlation was found between MEV, and systolic pulmonary venous flow, mean TIMI frame count, deceleration time, and isovolumetric relaxation time (P < 0.05). By multiple linear regression analysis, mean TIMI frame count (ss =-0.865, P < 0.001) was identified as independent predictors of MEV. Conclusion: This study indicates that SCF phenomenon may be related to low LAA blood flows.