PURPOSE: The aim of this study was to test the feasibility and the clinical usefulness of detection and measurement of distal left anterior descending coronary artery (LAD) flow using transthoracic echocardiography. METHODS: We prospectively examined 200 consecutive subjects(age 56+/-12 yrs, M:F=23:77). Of these subjects, 79 patients underwent coronary angiography. After obtaining the tubular color flow signals of distal LAD using an ultra-band transducer (5-12 MHz) with a special preset program of a low velocity range, the width and length of color Doppler signals, peak diastolic and systolic pulsed Doppler velocity (PDV) and velocity time integral(VTI) were measured. The echocardiographic findings of distal LAD flow were compared with the coronary angiogram. RESULTS: 1. In 142 of 200 subjects (71%), the color and pulsed Doppler signals with clear envelops were identified. 2. Forward biphasic flow in 86(60.6%) subjects and only diastolic flow in 56(39.4%) subjects were detected. 3.The mean length and width of color flow signals were 4.7+/-2.8mm (range 1.1-15.0 mm) and 1.6+/-0.7 mm (range 0.5-4.7 mm), respectively. 4.The mean PDV and VTI were 21.4+/-9.0 cm/sec(range 7.7-58.0 cm/sec) and 8.4+/-4.1 cm(range 2.8-26 cm), respectively. 5. The mean velocity range for obtaining the optimal Doppler signals of distal LAD was 13.0+/-4.2 cm/sec (range 6.4-32 cm/sec). 6. 14 of 22 (63%) subjects who distal LAD color flow signals were not identified showed the total or near total occlusion of LAD on the coronary angiogram. CONCLUSION: Detection and measurement of distal LAD flow are feasible in a high percentage of subjects by use of high frequency transthoracic Doppler echocardiography. The color and pulsed Doppler signals of distal LAD using transthoracic echocardiography at resting state may give the useful clinical information about coronary artery disease.