Transesophageal echocardiography was performed in 46 healthy subjects to define characteristics of normal left atrial appendage blood flow. Three different flow wave patterns were observed that were heart rate dependent (p < 0.01). A quadriphasic pattern, consisting of 2 diastolic forward (emptying) flow waves each followed by a backward (filling) flow wave, was present in 36 subjects (78%). Triphasic appendage flow was observed in 6 subjects (13%) and biphasic flow in 4 (9%). Mean heart rates among subjects with quadri-, tri- and biphasic flows were 75 +/- 11, 95 +/- 6 and 112 +/- 7 beats/min, respectively. Analysis of pulsed Doppler recordings of subjects with quadriphasic or triphasic appendage flow patterns showed that the onset of transmitral early diastolic peak flow wave was followed at 17 +/- 15 ms by the onset of pulmonary venous diastolic flow and at 43 +/- 17 ms by the onset of the first diastolic forward flow in the appendage. This sequence was constant and independent of heart rate (p < 0.01), suggesting a causal relation between left ventricular relaxation and the first diastolic forward flow wave in the appendage. The second diastolic forward flow followed the P wave on the electrocardiogram at 79 +/- 23 ms. Thus, left atrial appendage blood flow pattern in normal subjects is heart rate dependent, and ventricular relaxation appears to initiate early diastolic emptying of the appendage.