Dataset Information

Pulse wave imaging in normal, hypertensive and aneurysmal human aortas in vivo: a feasibility study.

ABSTRACT: Arterial stiffness is a well-established biomarker for cardiovascular risk, especially in the case of hypertension. The progressive stages of an abdominal aortic aneurysm (AAA) have also been associated with varying arterial stiffness. Pulse wave imaging (PWI) is a noninvasive, ultrasound imaging-based technique that uses the pulse wave-induced arterial wall motion to map the propagation of the pulse wave and measure the regional pulse wave velocity (PWV) as an index of arterial stiffness. In this study, the clinical feasibility of PWI was evaluated in normal, hypertensive, and aneurysmal human aortas. Radiofrequency-based speckle tracking was used to estimate the pulse wave-induced displacements in the abdominal aortic walls of normal (N = 15, mean age 32.5 ± 10.2 years), hypertensive (N = 13, mean age 60.8 ± 15.8 years), and aneurysmal (N = 5, mean age 71.6 ± 11.8 years) human subjects. Linear regression of the spatio-temporal variation of the displacement waveform in the anterior aortic wall over a single cardiac cycle yielded the slope as the PWV and the coefficient of determination r(2) as an approximate measure of the pulse wave propagation uniformity. The aortic PWV measurements in all normal, hypertensive, and AAA subjects were 6.03 ± 1.68, 6.69 ± 2.80, and 10.54 ± 6.52 m s(-1), respectively. There was no significant difference (p = 0.15) between the PWVs of the normal and hypertensive subjects while the PWVs of the AAA subjects were significantly higher (p < 0.001) compared to those of the other two groups. Also, the average r(2) in the AAA subjects was significantly lower (p < 0.001) than that in the normal and hypertensive subjects. These preliminary results suggest that the regional PWV and the pulse wave propagation uniformity (r(2)) obtained using PWI, in addition to the PWI images and spatio-temporal maps that provide qualitative visualization of the pulse wave, may potentially provide valuable information for the clinical characterization of aneurysms and other vascular pathologies that regionally alter the arterial wall mechanics.

SUBMITTER: Li RX

PROVIDER: S-EPMC4005727 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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Pulse wave imaging in normal, hypertensive and aneurysmal human aortas in vivo: a feasibility study.

Li Ronny X RX Luo Jianwen J Balaram Sandhya K SK Chaudhry Farooq A FA Shahmirzadi Danial D Konofagou Elisa E EE

Physics in medicine and biology 20130614 13

Arterial stiffness is a well-established biomarker for cardiovascular risk, especially in the case of hypertension. The progressive stages of an abdominal aortic aneurysm (AAA) have also been associated with varying arterial stiffness. Pulse wave imaging (PWI) is a noninvasive, ultrasound imaging-based technique that uses the pulse wave-induced arterial wall motion to map the propagation of the pulse wave and measure the regional pulse wave velocity (PWV) as an index of arterial stiffness. In th ...[more]

PMID: 23770991

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Project description:Pulse wave imaging (PWI) is an ultrasound imaging modality that estimates the wall stiffness of an imaged arterial segment by tracking the pulse wave propagation. The aim of the present study is to integrate PWI with vector flow imaging, enabling simultaneous and co-localized mapping of vessel wall mechanical properties and 2-D flow patterns. Two vector flow imaging techniques were implemented using the PWI acquisition sequence: 1) multiangle vector Doppler and 2) a cross-correlation-based vector flow imaging (CC VFI) method. The two vector flow imaging techniques were evaluated in vitro using a vessel phantom with an embedded plaque, along with spatially registered fluid structure interaction (FSI) simulations with the same geometry and inlet flow as the phantom setup. The flow magnitude and vector direction obtained through simulations and phantom experiments were compared in a prestenotic and stenotic segment of the phantom and at five different time frames. In most comparisons, CC VFI provided significantly lower bias or precision than the vector Doppler method ( ) indicating better performance. In addition, the proposed technique was applied to the carotid arteries of nonatherosclerotic subjects of different ages to investigate the relationship between PWI-derived compliance of the arterial wall and flow velocity in vivo. Spearman's rank-order test revealed positive correlation between compliance and peak flow velocity magnitude ( rs = 0.90 and ), while significantly lower compliance ( ) and lower peak flow velocity magnitude ( ) were determined in older (54-73 y.o.) compared with young (24-32 y.o.) subjects. Finally, initial feasibility was shown in an atherosclerotic common carotid artery in vivo. The proposed imaging modality successfully provided information on blood flow patterns and arterial wall stiffness and is expected to provide additional insight in studying carotid artery biomechanics, as well as aid in carotid artery disease diagnosis and monitoring.

Project description:Study on the objectivity of pulse diagnosis is inseparable from the instruments to obtain the pulse waves. The single-pulse diagnostic instrument is relatively mature in acquiring and analysing pulse waves, but the pulse information captured by single-pulse diagnostic instrument is limited. The sensor arrays can simulate rich sense of the doctor's fingers and catch multipoint and multiparameter array signals. How to analyse the acquired array signals is still a major problem in the objective research of pulse diagnosis. The goal of this study was to establish methods for analysing arrayed pulse waves and preliminarily apply them in hypertensive disorders. While a sensor array can be used for the real-time monitoring of twelve pulse wave channels, for each subject in this study, only the pulse wave signals of the left hand at the "guan" location were obtained. We calculated the average pulse wave (APW) per channel over a thirty-second interval. The most representative pulse wave (MRPW) and the APW were matched by their correlation coefficient (CC). The features of the MRPW and the features that corresponded to the array pulse volume (APV) parameters were identified manually. Finally, a clinical trial was conducted to detect these feature performance indicators in patients with hypertensive disorders. The independent-samples t-tests and the Mann-Whitney U-tests were performed to assess the differences in these pulse parameters between the healthy and hypertensive groups. We found that the radial passage (RP) APV h1, APV h3, APV h4, APV h3/h1 (P < 0.01), and APV h4/h1 (P < 0.05) were significantly higher in the hypertensive group than in the healthy group; the intermediate passage (IP) APV h4, APV h3/h1 (P < 0.05), and APV h4/h1 (P < 0.01) and the mean APV h3, APV h3/h1 (P < 0.05), and APV h4/h1 (P < 0.01) were significantly higher in the hypertensive group than in the healthy group, and the ulnar passage (UP) APV h4/h1 (P < 0.05) was clearly elevated in the hypertensive group. These results provide a preliminary validation of this novel approach for determining the APV by arrayed pulse wave analysis. In conclusion, we identified effective indicators of hypertensive vascular function. Traditional Chinese medicine (TCM) pulses comprise multidimensional information, and a sensor array could provide a better indication of TCM pulse characteristics. In this study, the validation of the arrayed pulse wave analysis demonstrates that the APV can reliably mirror TCM pulse characteristics.

Project description:Pulse wave attenuation characteristics reflect compliance and resistance properties of the vessel wall as well as initial pulse generation factors. Recently, it has become possible to measure and map the retinal vessel wall pulse wave amplitudes. Predictable pulse wave amplitude distribution may allow inferences to be made concerning vascular compliance and resistance. Twenty-eight eyes from sixteen subjects (8 male and 8 female) were examined using modified retinal photoplethysmography with simultaneous ophthalmodynamometry. This allowed the assessment of vessel wall pulsation amplitudes under a dynamic range of intraocular pressures. Pulse amplitudes were calculated using harmonic regression analysis. The pulse wave attenuation was measured under different ranges of ophthalmodynamometric force (ODF) as a function of distance along the vessel (VDist), which in turn was calculated in disc diameters (DD) from the center of the optic disc. A linear mixed-effects model with randomized slopes and intercepts was used to estimate the correlations between the logarithmically transformed harmonic regression wave amplitude (HRWa) and the Fourier trigonometric coefficients with the predictors (VDist and ODF). The retinal venous harmonic regression wave attenuation (coefficient value±standard error) -0.40±0.065/DD, (p-value < 0.00001, 95% confidence interval (CI) -0.53 to -0.27), which was approximately twice that of the arterial -0.17±0.048/DD, (p-value < 0.0004, 95% CI = -0.27 to -0.08). There was a positive correlation between attenuation of the harmonic regression wave and ophthalmodynamometric force in both vascular systems. The attenuation of all but the sine coefficient of the second Fourier harmonic (bn2) achieved statistical significance in the correlation with VDist. The cosine coefficient of the first Fourier harmonic an1 was the only coefficient to achieve statistical significance in the correlation with the predictors VDist and ODF in both vascular systems. The an1 coefficient value in the correlation with VDist was -3.79±0.78 and -1.269±0.37 (p < 0.0006), while this coefficient value in the correlation with ODF was 0.026±0.0099 and 0.009±0.04 (p < 0.01) in both the retinal veins and arteries respectively. The predictable attenuation characteristics in normal subjects suggest that this technique may allow the non-invasive quantification of retinal vascular compliance and other hemodynamic parameters.

Project description:The abdominal aortic aneurysm (AAA) is a silent and often deadly vascular disease caused by the localized weakening of the arterial wall. Previous work has indicated that local changes in wall stiffness can be detected with pulse wave imaging (PWI), which is a non-invasive technique for tracking the propagation of pulse waves along the aorta at high spatial and temporal resolutions. The aim of this study was to assess the capability of PWI to monitor and stage AAA progression in a murine model of the disease. ApoE/TIMP-1 knockout mice (N = 18) were given angiotensin II for 30 days via subcutaneously implanted osmotic pumps. The suprarenal sections of the abdominal aortas were imaged every 2-3 d after implantation using a 30-MHz VisualSonics Vevo 770 with 15-?m lateral resolution. Pulse wave propagation was monitored at an effective frame rate of 8 kHz by using retrospective electrocardiogram gating and by performing 1-D cross-correlation on the radiofrequency signals to obtain the displacements induced by the waves. In normal aortas, the pulse waves propagated at constant velocities (2.8 ± 0.9 m/s, r(2) = 0.89 ± 0.11), indicating that the composition of these vessels was relatively homogeneous. In the mice that developed AAAs (N = 10), the wave speeds in the aneurysm sac were 45% lower (1.6 ± 0.6 m/s) and were more variable (r(2) = 0.66 ± 0.23). Moreover, the wave-induced wall displacements were at least 80% lower within the sacs compared with the surrounding vessel. Finally, in mice that developed fissures (N = 5) or ruptures (N = 3) at the sites of their AAA, higher displacements directed out of the lumen and with no discernible wave pattern (r(2) < 0.20) were observed throughout the cardiac cycle. These findings indicate that PWI can be used to distinguish normal murine aortas from aneurysmal, fissured and ruptured ones. Hence, PWI could potentially be used to monitor and stage human aneurysms by providing information complementary to standard B-mode ultrasound.

Dataset Information

Pulse wave imaging in normal, hypertensive and aneurysmal human aortas in vivo: a feasibility study.

Publications

Pulse wave imaging in normal, hypertensive and aneurysmal human aortas in vivo: a feasibility study.

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