Accuracy of the main Doppler methods for evaluating the degree of carotid stenoses (continuous wave, pulsed wave, and color Doppler)

Flexible electronics for cardiovascular healthcare monitoring

Cardiovascular diseases (CVDs) are one of the most urgent threats to humans worldwide, which are responsible for almost one-third of global mortality. Over the last decade, research on flexible electronics for monitoring and treatment of CVDs has attracted tremendous attention. In contrast to conventional medical instruments in hospitals that are usually bulky, hard to move, monofunctional, and time-consuming, flexible electronics are capable of continuous, noninvasive, real-time, and portable monitoring. Notable progress has been made in this emerging field, and thus a number of significant achievements and concomitant research prospects deserve attention for practical implementation. Here, we comprehensively review the latest progress of flexible electronics for CVDs, focusing on new functions provided by flexible electronics. First, the characteristics of CVDs and flexible electronics and the foundation of their combination are briefly reviewed. Then, four representative applications of flexible electronics for CVDs are elaborated: blood pressure (BP) monitoring, electrocardiogram (ECG) monitoring, echocardiogram monitoring, and direct epicardium monitoring. Their operational principles, progress, merits and demerits, and future efforts are discussed. Finally, the remaining challenges and opportunities for flexible electronics for cardiovascular healthcare are outlined.

The effect of norepinephrine on common carotid artery blood flow in septic shock patients

This study was designed to evaluate the hemodynamic effect of norepinephrine (NE) on the peak systolic velocity (PSV), diameter, and blood flow of the common carotid artery (CCA) using the point-of-care ultrasound (POCUS) in patients with septic shock. The study involved patients above 18 years old with septic shock. Arterial monitoring, carotid ultrasonography, and transthoracic echocardiography were performed before NE administration (T₀). When the mean arterial pressure exceeded 65 mmHg after NE administration (T₁), the measurement was repeated. Twenty-four patients (median age 67 [interquartile range: 54–77] years; 42% female) with septic shock were examined in this study. Before (T₀) and after (T₁) NE administration, the PSV (mean, standard deviation [SD]) changed from 85.3 (21.1) cm/s to 83.5 (23.5) cm/s (p = 0.417); this change was not significant. However, the diameter and blood flow of the CCA increased significantly from 0.6 (0.09) cm and 0.75 (0.27) L/min to 0.66 (0.09) cm and 0.85 (0.27) L/min, respectively (p < 0.001). The diameter of the left ventricular outflow tract (LVOT) remained unchanged, but the velocity time integral of the LVOT increased significantly from 21.7 (4.39) cm to 23.6 (5.14) cm. There was no significant correlation between changes in blood flow of the CCA and changes in cardiac output (coefficient −0.365, p = 0.079). In conclusion, NE increased the diameter and blood flow of the CCA significantly, without changing the PSV in patients with septic shock.

Quantitative evaluation of graded hindlimb ischemia based on pharmacokinetic modelling and hemodynamic analysis of indocyanine green

OBJECTIVE

Accurate evaluation of the degree of hindlimb ischemia is challenging but essential for the diagnosis and treatment of peripheral vascular insufficiency. The aim of the study is to apply a multiparametric method for the quantitative estimation of mouse models with different degrees of hindlimb ischemia based on a dynamic fluorescence imaging-based strategy.

APPROACH

An adjustable hydraulic occluder was placed around the thigh root of one hindlimb to induce six different degrees of hindlimb ischemia. Five parameters were extracted to quantitatively evaluate the degree of ischemia, including perfusion rate (PR) and perfusion vascular density (PVD) from a mathematical model of indocyanine green (ICG) pharmacokinetics, rising time (T _rise), blood flow index (BFI) and mean fluorescence intensity (MFI) from time-series analysis of ICG hemodynamics.

MAIN RESULTS

The results showed that the normalized PR and BFI decreased while the normalized T _rise increased progressively with the degree of ischemia. The normalized PVD and MFI first increased and then decreased with the degree of ischemia. High correlation was observed between the degree of ischemia and the arterial oxygen saturation which was measured by an oximeter.

SIGNIFICANCE

The results of this work demonstrated that PR, BFI and T _rise can be used for the quantitative and comprehensive evaluation of graded hindlimb ischemia.

Comparison of degree of stenosis and plaque volume for the assessment of carotid atherosclerosis using 2-D ultrasound

The degree of carotid stenosis (%ST) remains the most frequently used parameter for identifying patients with high risk of stroke but the relationship between %ST and the occurrence of stroke remains controversial. The objectives of this study were to check (1) the relationship between the %ST and the plaque volume index (PVI) as measured by echography and Doppler, (2) the relationship between the intima media thickness (IMT), a vessel wall remodeling index and the PVI an atheromatous growth index. For each of the 128 patients, (165 carotid stenosis), we measured the % ST (section or diameter), the max stenosis velocity (V(max)), the PVI and the common carotid IMT. The %ST (section) ranged from 10% to 93% (mean 66+/-18), V(max) from 0.3m/s to 3m/s (mean 1.2+/-0.8), PVI from 0.61cm(3) to 1.17cm(3) (mean 0.41+/-0.21) and the IMT from 0.08cm up to 0.31cm (mean 0.12+/-0.03). There was no significant correlation between either PVI and %ST (section or diameter), PVI and minimal stenosis section area (S1) or between PVI and V(max). There was no significant correlation between IMT and both %ST area and PVI. PVI was significantly correlated with the whole artery section area (S2) and the plaque length (L). The %ST (section or diameter) was significantly correlated with S1 but not with S2. The absence of correlation between the PVI and the %ST confirm that these two parameters describe two different processes of the atheromatous development.

Doppler ultrasound signals simulation from vessels with various stenosis degrees

As a non-invasive method, the Doppler ultrasound technique is used to detect the vessel stenosis. To search for characteristics of Doppler ultrasound signals sensitive to the stenosis, a computer simulation approach is proposed in this paper to generate Doppler ultrasound signals from vessels with various stenosis degrees. The blood flow velocity distribution in a stenosed vessel is firstly calculated using the transient finite element method (FEM). Then the power spectral density of Doppler signals is estimated using the overall-distribution nonparametric estimation method. Finally Doppler signals are generated using the cosine-superposed method. The proposed approach is proved to be useful for simulating Doppler ultrasound signals from vessels with various stenosis degrees. It is also shown that characteristics of Doppler ultrasound signals may be used to estimate the vessel's stenosis degree.

Color Doppler, power Doppler and B-flow ultrasound in the assessment of ICA stenosis: Comparison with 64-MD-CT angiography

The purpose of this study is to investigate the diagnostic potential of color-coded Doppler sonography (CCDS), power-Doppler (PD) and B-flow ultrasound in assessing the degree of extracranial internal carotid artery (ICA) stenosis in comparison to CT-angiography (MD-CTA). Thirty-two consecutive patients referred for CTA with 41 ICA-stenoses were included in this prospective study. MD-CTA was performed using a 64 row scanner with a CTDIvol of 13.1 mGy/cm. In CTA, CCDS, PD and B-flow, the degree of stenosis was evaluated by the minimal intrastenotic diameter in comparison to the poststenotic diameter. Two radiologists performed a quantitative evaluation of the stenoses in consensus blinded to the results of ultrasound. These were correlated to CTA, CCDS, PD and B-flow, intraoperative findings and clinical follow-up. Grading of the stenoses in B-flow ultrasound outperformed the other techniques in terms of accuracy with a correlation coefficient to CTA of 0.88, while PD and CCDS measurements yield coefficients of 0.74 and 0.70. Bland-Altman analysis additionally shows a very little bias of the three US methods between 0.5 and 3.2 %. There is excellent correlation (coefficient 0.88, CI 0.77-0.93) with 64-MD-CTA and B-flow ultrasound in terms of accuracy for intrastenotic and poststenotic diameter. Duplex sonography is useful for screening purposes.

High-grade stenoses of the internal carotid artery: comparison of high-resolution contrast enhanced 3D MRA, duplex sonography and power Doppler imaging

PURPOSE

The objective of this study was to determine the agreement and diagnostic accuracy of high-resolution contrast enhanced magnetic resonance angiography (MRA) with integrated parallel acquisition techniques (iPAT), color coded duplex ultrasound (CCDS) and power Doppler ultrasound (PD) in the assessment of high-grade stenoses of the internal carotid artery (ICA).

METHODS

Forty-four patients with 52 known or suspected stenoses of the internal carotid artery (ICA) were included in this prospective study. High-resolution MRA scans with a spatial resolution of 0.9 mm x 0.7 mm x 0.9 mm were acquired with an iPAT acceleration factor of 2 on a 1.5T MR system (Sonata Maestro Class, Siemens Medical Solutions, Erlangen, Germany) with a head, neck and body coil. For the 3D-CE MRA a fast spoiled gradient echo sequence (FLASH) was used. To compensate for the inherent signal loss with parallel imaging, a 1M contrast agent (gadobutrol, Gadovist, Schering, Berlin, Germany) was used. Stenoses were quantified by two readers in consensus in cross-sectional area measurements and graded according to the NASCET criteria. Using color coded duplex ultrasound (CCDS) and power Doppler (PD; Logiq 9, GE), the stenoses were also graded by two readers in consensus according to the NASCET criteria from intra- and post-stenotic diameter measurements. The results of MRA, CCDS and PD were compared to intraoperative findings or to follow-up examinations.

RESULTS

High-resolution MRA allowed an excellent grading of vascular stenoses. In 70-90% degrees of stenosis there was an underestimation of the degree of stenosis in MRA as well as in CCDS. However, there was an overestimation of 90% stenoses in both MRA and CCDS. Pseudoocclusions with a lumen of less than one millimeter were occasionally rated as a complete occlusion in MRA.

CONCLUSION

A combination of MRA and duplex sonography seems reasonable for the accurate grading of stenoses and determination of distal stenoses downstream. However, the accuracy of duplex ultrasound depends on the examiner's experience.

Sleep apnoea inducing hypoxemia is associated with early signs of carotid atherosclerosis in males

The intima-media thickness (IMT) of carotid arteries as a marker of preclinical atherosclerosis was measured by ultrasonography in 49 subjects to determine, how strongly the obstructive sleep apnoea (OSA) syndrome is associated with atherosclerosis. Maximal IMT was higher in patients with cardiovascular diseases and with or without risk factors of atherosclerosis, presenting also OSA (apnoea-hypopnoea index=26.1+/-15.6/h) compared to controls without OSA (0.91+/-0.21 mm versus 0.77+/-0.18 mm, p<0.05). The prevalence of IMT > or = 0.85 mm was also higher in patients with cardiovascular pathology presenting OSA than without it (p<0.05). IMT(max) was increased in subjects with mild to moderate OSA alone (AHI=20.4+/-8.7/h) versus healthy controls (0.83+/-0.14 mm versus 0.63+/-0.08 mm, p<0.01). Regression analysis revealed a correlation of IMT(max) with the frequency, intensity and duration of intermittent hypoxemia reflected by AHI (p<0.01), minimal oxygen saturation (p<0.01) and time spent with Sa(O2) < 90% (p<0.05) in patients presenting OSA. The results indicate clear association between early signs of carotid atherosclerosis and moderate OSA in males with and without concomitant cardiovascular pathology.

Diagnostics and characterisation of preocclusive stenoses and occlusions of the internal carotid artery with B-flow

The purpose was to evaluate whether B-flow can improve the ultrasonographic diagnosis of preocclusive stenosis and occlusion of the internal carotid artery (ICA) compared with colour-coded Doppler and power Doppler. Ninety patients with occlusions or preocclusive stenoses of the ICA suspected by Doppler sonography were examined with B-flow in comparison with colour-coded Doppler sonography (CCDS), power Doppler (PD) and intra-arterial digital subtraction angiography (DSA). Intrastenotic flow detection and lengths of stenoses were the main criteria. Ulcerated plaques found by surgery in 42/90 patients were compared by ultrasonography (US). Diagnosis of ICA occlusion with CCDS, PD and B-flow was correct in all 42 cases. A preocclusive ICA stenosis in DSA was detected correctly in all 48/48 cases (100%) for B-flow, in 44/48 (92%) for PD and in 39/48 (81%) for CCDS. Surgical findings showed in 17/42 cases ulcerated plaques; 15/17 (89%) of these cases were detected with B-flow, 12/17 (71%) with PD, 10/17 (59%) with CCDS, and 8/17 (47%) with DSA. With B-flow the extent of stenosis was appraised more precisely than with PD and CCDS (P<0.0001). In conclusion, B-flow is a reliable method for preocclusive stenosis of the ICA with less intrastenotic flow artefacts. B-flow facilitates the characterization of plaque morphologies.

Reconstruction and quantification of the carotid artery bifurcation from 3-D ultrasound images

Three-dimensional (3-D) ultrasound is a relatively new technique, which is well suited to imaging superficial blood vessels, and potentially provides a useful, noninvasive method for generating anatomically realistic 3-D models of the peripheral vasculature. Such models are essential for accurate simulation of blood flow using computational fluid dynamics (CFD), but may also be used to quantify atherosclerotic plaque more comprehensively than routine clinical methods. In this paper, we present a spline-based method for reconstructing the normal and diseased carotid artery bifurcation from images acquired using a freehand 3-D ultrasound system. The vessel wall (intima-media interface) and lumen surfaces are represented by a geometric model defined using smoothing splines. Using this coupled wall-lumen model, we demonstrate how plaque may be analyzed automatically to provide a comprehensive set of quantitative measures of size and shape, including established clinical measures, such as degree of (diameter) stenosis. The geometric accuracy of 3-D ultrasound reconstruction is assessed using pulsatile phantoms of the carotid bifurcation, and we conclude by demonstrating the in vivo application of the algorithms outlined to 3-D ultrasound scans from a series of patient carotid arteries.

Carotid arteries: contrast-enhanced US angiography--preliminary clinical experience

B-mode ultrasonographic (US) angiography enhanced with a microbubble-based US contrast agent (FS069) was evaluated in human subjects with carotid artery disease. Results at contrast material-enhanced US angiography and duplex US were compared with those at conventional angiography. Both US angiography and duplex US accurately depicted stenoses of 70% or more compared with those depicted at conventional angiography. The percentage diameter stenosis of the internal carotid artery measured at US angiography strongly correlated with that measured at conventional angiography (r = 0.988). The percentage area stenosis measured at US angiography strongly correlated with ex vivo measurements of the resected carotid plaque at magnetic resonance imaging (r = 0.979). US angiography depicted unsuspected wall irregularities, ulceration, and dissection.

Spiral computed tomography angiography (SCTA) and color coded duplex ultrasound (CCDUS): two complementary diagnostic techniques for assessment of extracranial cerebral artery stenosis

Atherosclerotic lesions of the extracranial cerebral arteries account for ischemic stroke in over half of all cases. The risk of stroke associated with symptomatic carotid artery disease is related to the severity of the stenosis. Results of the two major clinical trials, North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST), showed that patients with symptomatic carotid artery disease may benefit from carotid endarterectomy. Therefore, detection and quantification of stenosis are essential. Discrepancies in the angiographic criteria used in both NASCET and ECST trials resulted in continued controversy about the most accurate method of measuring carotid artery stenosis. Moreover, to avoid complications related to the angiography procedure, a good evaluation of vessel wall and plaque composition need to be considered. Both SCTA and CCDUS are non invasive techniques that could overcome angiographic complications and give detailed information on stenosis grading and plaque characteristics. They have been used to evaluate carotid stenosis as a single or combined methods.

Serial measurement of cross-sectional area in peripheral vein grafts using three-dimensional ultrasound

Frequent surveillance of bypass grafts placed in the lower limbs can provide early detection of stenoses. A three-dimensional (3-D) ultrasound (US) imaging system has been used to produce serial surface reconstructions of regions of interest in vein grafts in the lower extremities. Using anatomical reference points, data sets from serial studies are registered in a common 3-D coordinate system. Cross-sectional area measurements are extracted from the surface reconstructions in planes normal to the vessel center axis. These measurements are compared at matched sites over time to track changes in the vessel configuration. The quantitative measurements are paired with surface displays of the vessels for a complete depiction of the changing geometry. Example studies from three patients are shown, for time periods up to 38 weeks. The cross-sectional area measurements highlight regions of remodeling and developing stenoses within the grafts.