TRANSTHORACIC HIGH-FREQUENCY 2-DIMENSIONAL ECHOCARDIOGRAPHY, DOPPLER AND COLOR FLOW MAPPING TO DETERMINE ANATOMY AND BLOOD-FLOW PATTERNS IN THE DISTAL LEFT ANTERIOR DESCENDING CORONARY-ARTERY

Combined high-frequency transthoracic ultrasound, pulsed Doppler and color flow mapping were used to image and assess blood flow velocity in the distal left anterior descending artery (LAD) in 56 consecutive patients. All patients subsequently underwent coronary angiography. The LAD was imaged in 19 patients (34%), and the diameter was measured in 12 with high-quality images (mean diameter 1.8 mm +/- 0.08). In 1 patient, the penetrating branches of the LAD were imaged. The distal LAD appeared normal by ultrasound in 18 patients, and a significant stenosis was detected in 1; angiography confirmed the ultrasound findings. There were no false negative results. Characteristic biphasic flow with higher velocities in diastole were noted in all 19 patients. Color flow mapping demonstrated normal laminar flow, except in the patient with a distal stenosis. Pulsed Doppler confirmed an increased velocity distal to the stenosis in this patient. This study is the first transthoracic evaluation of the hemodynamic effects of a coronary artery stenosis, and the first in vivo description of blood flow disturbance at a distal coronary stenosis in humans. The clinical use of this technique is limited, because only the distal portion of the LAD is visualized. However, it may provide a noninvasive means of assessing distal LAD diameter and blood flow, and changes in these parameters under a variety of physiologic, pharmacologic and interventional stimuli.