Previous studies utilizing Doppler catheters to assess blood flow immediately following coronary artery interventions have failed to demonstrate significant improvement in proximal coronary artery velocities or vasodilator reserve. Measurement of blood flow velocity, flow reserve, and the phasic diastolic/systolic velocity ratio in the distal coronary artery has been performed following various interventional procedures utilizing a low profile (.018 in) Doppler angioplasty guidewire. Following balloon angioplasty in 38 patients, average peak velocity increased significantly from 19 +/- 12 to 35 +/- 16 cm/sec in the distal coronary artery. The diastolic/systolic flow ratio improved from 1.3 +/- 0.5 to 1.8 +/- 0.5 and coronary flow reserve remained unchanged. Similar improvement in distal mean velocities (200%) versus proximal mean velocities (90% increase), and improvement in phasic velocity patterns, total velocity integral, and peak diastolic velocity were also noted in a separate study of 29 patients, before and after balloon angioplasty. Following excimer laser angioplasty in 10 patients, average peak velocity in the distal coronary artery was noted to increase from 6.3 to 13.0 cm/sec following laser alone, with a further increase to 20.6 cm/sec following adjunctive balloon angioplasty. The diastolic/systolic flow ratio increased from a mean value of 1.1 to 2.0 following laser recanalization, with a further increase to 2.9 following adjunctive balloon angioplasty. Following directional coronary atherectomy only modest improvement in distal average peak velocity was noted (24.7 to 31.2 cm/sec), with no significant change in diastolic/systolic velocity ratio (1.78 vs 2.04) immediately following the procedure. Measurement of distal flow velocity parameters performed immediately following coronary interventions may prove useful in assessing the hemodynamic result of these interventions and may prove useful in clinical decision making.