In acute myocardial infarction, the coronary blood flow velocity waveform changes with the damage in the infarcted myocardium. We developed a grading system using the shorter diastolic deceleration time (DDT), appearance of systolic flow reversal (SFR), and disappearance of systolic anterograde flow. We studied 72 patients with a first anterior acute myocardial infarction. Doppler guidewire monitoring and myocardial contrast echocardiography were performed 10 and 15 minutes after percutaneous coronary intervention, and left ventriculography was performed at discharge (24 +/- 2 days) to measure regional wall motion (SD/chord). Patients were classified into 4 groups according to the coronary blood flow velocity pattern: group I (n = 39), DDT >or=600 ms; group II (n = 10), DDT <600 ms; group III (n = 17), DDT <600 ms with SFR; and group IV (n = 14), DDT <600 ms with SFR and without systolic anterograde flow. The no-reflow phenomenon was observed in no patients in group I, in 3 in group II, in 11 in group III, and all 14 patients in group IV. Regional wall motion was highest in group I and decreased with increasing group number (groups I, II, III, and IV, -1.45 +/- 0.80, -2.36 +/- 0.60, -2.90 +/- 0.50, and -3.20 +/- 0.52 SD/chord, respectively). With the progression of damage in the infarcted myocardium, the DDT shortened first, followed by the appearance of SFR, and then the disappearance of systolic anterograde flow. In conclusion, analysis of the coronary blood flow velocity pattern allows assessment of the severity of microvascular dysfunction and prediction of left ventricular functional outcomes.