Assessing mild coronary atherosclerosis by means of transthoracic enhanced Doppler echocardiography in convergent color Doppler mode. A validation study versus intravascular ultrasound

Background: Transthoracic enhanced echo Doppler of coronaries (CED) has the potential to detect coronary flow and its acceleration at the stenosis site over the entire left anterior descending coronary artery (LAD). CED has recently enhanced its feasibility thanks both to new technologies (convergent color Doppler mode) and new tomographic planes. As blood flow velocity (BFV) is inversely related to vessel radius elevated to the power, we hypothesized that even mild coronary narrowing plaque, as assessed by intravascular ultrasound (IVUS), can cause enough acceleration to be detected by CED. Methods: Fifty consecutive patients (pts) (age 55±12years, males 74%, BMI =28±4) scheduled for cath and IVUS were evaluated by CED in convergent color Doppler mode . Color guided pulsed waved Doppler mapping of the whole LAD (specifically the proximal, mid and distal part) was performed in order to attain for each segment maximal and reference BFV. Results: CED feasibility was 100%. IVUS showed 45 patients with mild severity atherosclerosis involving one or more segments of LAD and 5 with totally normal LAD. Maximal velocity was higher in the diseased segment than in the normal segments (54±25 cm/s vs 31±6 cm/s; p<0.001); as the reference velocity was similar (30±6cm/s vs 29±6cm/s; p=ns), the percentage increase in velocity was also higher (77±56% vs 4±9%; p<0.001). Using a cutoff value of a 22% increase in velocity, sensitivity and specificity to detect at least one plaque involving LAD was respectively 82% (37/45 pts) and 100% (5/5 pts) The location of the BFV acceleration (aliasing zone at color Doppler) strictly corresponded to IVUS plaque location in proximal and mid LAD: 34 pts showed concordant location (11 with proximal plaque, 10 with mid plaques and 15 with both segments plaques) and 11 discordant (8 pts with plaques missed and 3 with plaques misplaced by CED) (Cramer’s V = 0,84, P<0,001). In corresponding segments lumen area stenosis (%) as assessed by CED (continuity equation) concurred with that assessed by IVUS (44±14 % vs. 37±16%) with r = 0,42 (p=0.014). Conclusion: BFV evaluation in the LAD by means of CED is feasible and reliable in assessing LAD mild atherosclerosis in a totally non-invasive way