Background: A more sensitive transthoracic color Doppler technology (convergent color Doppler), along with a heart rate (HR) reduction and new tomographic planes, can greatly improve coronary blood flow velocity (BFV) recordings in the left main (LMCA) and left anterior descending (LAD) coronary arteries, allowing the detection of even a slight acceleration of BFV due to mild coronary stenosis.
Methods: A group of 26 patients underwent convergent color Doppler transthoracic echocardiography (CC-Doppler TTE) in the LMCA and in the LAD coronary arteries before and after HR lowering. A second group of 71 patients scheduled for intravascular ultrasound, expanded to 96 with 25 more patients with normal LAD (by angiography/low likelihood of disease), underwent BFV Doppler recordings by CC-Doppler TTE of the whole LAD (specifically the proximal, mid and distal segments) to detect a localized increase in BFV, after attaining maximal and reference BFV in each segment.
Results: In the first group, HR reduction dramatically improved the detection of optimal flow in the LMCA and LAD, from 4 to 54% and from 6 to 94% of the segments, respectively (P < 0.001). In the second group intravascular ultrasonography (IVUS) showed mild stenoses in 60 patients. The maximum velocity was higher in the diseased segment than normal segments (49 ± 24 vs. 33 ± 11 cm/s; P < 0.001) and as the reference velocity was similar (32 ± 9 vs. 33 ± 11 cm/s; P = ns), the % increase was also higher (52 ± 52 vs. 0.7 ± 3%; P < 0.001). Using a >21% increase in velocity as a cutoff value, the sensitivity and specificity of CC-Doppler TTE in detecting at least one LAD plaque were 87% (52/60 patients [pts]) and 100% (36/36 pts), respectively.
Conclusion: CC-Doppler TTE evaluation of LAD BFV is greatly improved after reducing HR, allowing accurate noninvasive assessment of mild LAD stenosis with no radiation exposure.