Recently, assessment of left anterior descending (LAD) coronary flow by transthorasic Doppler echocardiography (TTDE) has been emerged as a useful tool in evaluation of microcirculatory function of coronary circulation. The measuring site of coronary flow by TTDE is distal LAD. But it was not fully investigated whether the distal flow velocity is identical to that of proximal segment. The purpose of this study is to compare coronary blood flow velocity and coronary flow reserve (CFR) in normal LAD according to its level.

9 patients (1 male, 8 females; mean age 52.8±11.1years) were included for this study. Coronary flow velocity was measured with intracoronary Doppler guide wire at the proximal (before first diagonal branch), mid (after second diagonal branch), and distal segments of LAD at baseline and after intracoronary bolus injection of 18 microgram adenosine. Baseline and hyperemic average peak velocity (APV) and CFR were compared between segment.

Baseline and hyperemic APV appears to be diminished from proximal (24.6±3.5 cm/sec, 55.8±10.7 cm/sec) to distal (21.7±6.9 cm/sec, 49.7±17.2 cm/sec) LAD without statistical significance. But, CFR showed no significant difference in each segments (proximal, mid, and distal segment; 2.3±0.26, 2.3±0.32, 2.3±0.48, p=0.95). As the increment of peak systolic velocity (PSV) from baseline to hyperemic state was larger than that of peak diastolic velocity (PDV), diastolic to peak systolic velocity ratio (DSVR) was decreased significantly by hyperemic state in proximal and distal segment (baseline; 2.1±0.8, 2.1±0.5 vs hyperemia; 1.8±0.6, 1.7±0.3, p<0.05).

Coronary blood flow velocity appears to be decreased from proximal to distal segment of normal LAD without statistical significance. There were no differences in CFR between proximal, mid and distal segment of normal LAD.