The diastolic deceleration slope of coronary flow velocity is steeper in patients with substantial `no reflow' phenomenon than in those without it. This study investigated whether functional outcomes in patients with anterior wall acute myocardial infarction (AMI) can be predicted by analyzing the coronary flow velocity pattern recorded with transthoracic Doppler (TTD) echocardiography. Coronary blood flow velocity in the distal left anterior descending coronary artery was recorded with TTD at day-2 after primary percutaneous transluminal coronary angioplasty/Stent in 51 patients with anterior AMI and the diastolic deceleration half time (DHT, ms) was measured. The wall motion score index (WMSI) was measured at day-1 and -21. In the retrospective study, the DHT was much shorter in those with a poor outcome than in those with good outcome (152±109 vs 395±128 ms, p<0.05). Receiver-operating characteristic analysis documented that DHT ≥300 ms is a suitable cut-off point (sensitivity of 83% and specificity of 93%). In the prospective study (n=30), ΔWMSI(d1-d21) was significantly higher in those with a DHT ≥300 ms than those without (0.3±0.5 vs 1.6±0.7, p<0.001). DHT correlated significantly with ΔWMSI(d1-d21) (r=0.76, p<0.001). Patients with a shorter DHT of diastolic coronary flow velocity have a poorer functional outcome among patients with anterior AMI. The TTD-determined DHT is a useful predictor of myocardial viability after an anterior AMI. (Jpn Circ J 2001; 65: 717 - 722)