Left ventricular diastolic function (LVDF) derived from the analysis of Doppler transmitral flow (TMF) has been analyzed. Since little is known about changes of LVDF during cardiac surgery, our aim of this study is to investigate TMF as a predictor of LVDF during the coronary artery bypass surgery (CAB). Twenty-eight patients were enrolled in this study and divided into two groups depending on the ratio of peak early filling (E) and atrial (A) velocity (E/A > or = 1; good LVDF, E/A < 1; impaired LVDF) measured by transesophageal echocardiography after induction of anesthesia. In both groups, E/A and E decreased significantly during internal mammalian artery dissection compared with after induction, suggesting left ventricular dysfunction. Especially in impaired LVDF group, peak A velocity did not increase in spite of the significant reduction in cardiac output and atrial contributions failed to compensate hemodynamics in this setting. More detailed features of cardiac function might be obtained by TMF analysis during CAB.