A new noninvasive method for assessing mild coronary atherosclerosis: transthoracic convergent color Doppler after heart rate reduction. Validation vs. intracoronary ultrasound

Abstract

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.

Coronary Flow and Reserve by Enhanced Transthoracic Doppler Trumps Coronary Anatomy by Computed Tomography in Assessing Coronary Artery Stenosis

“…He was overweight so his standard echocardiography window was limited. Owing to obesity and the suboptimal heart rate reductions, the examination was of suboptimal quality but nonetheless fully diagnostic (this kind of examination has a feasibility of ∼ =100%, as recently reported) [5]. It took 45 min (including the CFR assessment).…”

“…The color Doppler signal was attained in convergent color-Doppler mode at 2.5 MHz transmission frequency, while spectral Doppler was performed in fundamental mode at either 2.0 or 2.5 MHz. The color-coded Doppler setting was adjusted to maximize scanning sensitivity (pulse repetition frequency was set at 16 cm/s (2.5 MHz) and maximizing the sample volume of color flow mapping) without significantly reducing the frame rate (the color box size was reduced to remain within a frame rate of >30 Hz) [5].…”

“…Before the examination, the heart rate was reduced with beta blockers (100 mg of metoprolol PO) to a suboptimal value of 65 b/m [5]. He had refrained from drinking beverages containing caffeine already three days before the hospital admission.…”

“…Trans-thoracic enhanced Doppler echocardiography (E-Doppler TTE) can assess the blood flow velocity in the left main coronary artery (LMCA) and the whole left anterior descending coronary artery (LAD). It has recently been demonstrated to have very Diagnostics 2021, 11, 245 2 of 12 high feasibility, thanks to the combination with three technological advances: new power Doppler-based technology (convergent color-Doppler mode), along with pharmacologically lowering the heart rate, and new tomographic planes [5]. This method allows the assessment in these two vessels primarily of the transtenotic coronary flow velocity that is usually expressed as percentage velocity increment with respect to a reference site.…”

“…Such a velocity increment is an adaptive mechanism to compensate for lumen narrowing in order to keep the flow constant [6]. It can be accurately measured by E-Doppler TTE thanks to the very recent technical advances [5], and the severity of the stenosis can be assessed by applying the continuity equation [5]. Moreover, it allows the assessment of the distal coronary flow reserve (CFR), a major parameter for assessing global coronary physiology [7][8][9][10].…”