Low Blood Flow Velocity Research Articles

Effects of acupuncture on carotid intima-media thickness and cerebral blood flow velocity in patients with mild-to-moderate hypertension

To observe the characteristics of carotid intima-media thickness (IMT) and cerebral blood flow velocity in patients with mild-to-moderate hypertension, and to evaluate the effects of acupuncture on carotid IMT and blood flow velocity of middle cerebral artery and vertebral-basilar artery. A total of 240 patients with mild-to-moderate hypertension who met the inclusion criteria were treated with Huoxue Sanfeng acupuncture method proposed by academician SHI Xue-min. The acupoints of Renying (ST 9), Quchi (LI 11), Hegu (LI 4), Zusanli (ST 36) and Taichong (LR 3) were selected. The treatment was given once a day, five times a week for 3 months. The carotid ultrasonography and transcranial color Doppler were performed before treatment and 3 months after treatment to evaluate the improvements of carotid IMT and brain blood flow velocity. Among 175 patients, 94.3% suffered from impaired carotid IMT. After acupuncture intervention, 7.7%-10.9% patients had improved IMT but 4.6%-6.3% had aggravated carotid IMT. There was no significant difference of carotid IMT before and after treatment (P>0.05). About 50% patients had abnormal intracranial blood flow velocity; after acupuncture intervention, 27.4%-33.3% patients who had the abnormal blood flow velocity had normal one, but 27.0%-52.5% patients who had normal blood flow velocity had abnormal one. After acupuncture intervention, the low-speed blood flow of MCA, VA and BA in female patients aged 41-60 years and the low-speed blood flow of MCA and VA in female patients aged 61-70 years were significantly improved (all P<0.05); the high-speed blood flow of MCA and VA in male patients aged 61-70 years and the high-speed blood flow of VA and BA in female patients aged 41-60 years were significantly decreased (all P<0.05). Nearly 95% of patients with mild-to-moderate hypertension had carotid IMT, and about 50% had abnormal blood flow velocity of intracranial artery. The present study failed to found significant effects of acupuncture on carotid IMT, but it shows acupuncture can generally improve the low blood flow velocity in women with mild-to-moderate hypertension.

Transcranial Doppler and Magnetic Resonance in Tanzanian Children With Sickle Cell Disease.

Background and Purpose- We determined prevalences of neurological complications, vascular abnormality, and infarction in Tanzanian children with sickle cell disease. Methods- Children with sickle cell disease were consecutively enrolled for transcranial Doppler; those with slightly elevated (>150 cm/s), low (<50 cm/s) or absent cerebral blood flow velocity (CBFv) were invited for brain magnetic resonance imaging and magnetic resonance angiography. Results- Of 200 children (median age 9; range 6-13 years; 105 [2.5%] boys), 21 (11%) and 15 (8%) had previous seizures and unilateral weakness, respectively. Twenty-eight (14%) had elevated and 39 (20%) had low/absent CBFv, all associated with lower hemoglobin level, but not higher indirect bilirubin level. On multivariable analysis, CBFv>150 cm/s was associated with frequent painful crises and low hemoglobin level. Absent/low CBFv was associated with low hemoglobin level and history of unilateral weakness. In 49 out of 67 children with low/absent/elevated transcranial Doppler undergoing magnetic resonance imaging, 43% had infarction, whereas 24 out of 48 (50%) magnetic resonance angiographies were abnormal. One had hemorrhagic infarction; none had microbleeds. Posterior circulation infarcts occurred in 14%. Of 11 children with previous seizure undergoing magnetic resonance imaging, 10 (91%) had infarction (5 silent) compared with 11 out of 38 (29%) of the remainder ( P=0.003). Of 7 children with clinical stroke, 2 had recurrent stroke and 3 died; 4 out of 5 had absent CBFv. Of 193 without stroke, 1 died and 1 had a stroke; both had absent CBFv. Conclusions- In one-third of Tanzanian children with sickle cell disease, CBFv is outside the normal range, associated with frequent painful crises and low hemoglobin level, but not hemolysis. Half have abnormal magnetic resonance angiography. African children with sickle cell disease should be evaluated with transcranial Doppler; those with low/absent/elevated CBFv should undergo magnetic resonance imaging/magnetic resonance angiography.

Three-dimensional extent of flow stagnation in transcatheter heart valves.

The recent unexpected discovery of thrombosis in transcatheter heart valves (THVs) has led to increased concerns of long-term valve durability. Based on the clinical evidence combined with Virchow's triad, the primary hypothesis is that low-velocity blood flow around the valve could be a primary cause for thrombosis. However, due to limited optical access in such unsteady three-dimensional biomedical flows, measurements are challenging. In this study, for the first time, we employ a novel single camera volumetric velocimetry technique to investigate unsteady three-dimensional cardiovascular flows. Validation of the novel volumetric velocimetry technique with standard planar particle image velocimetry (PIV) technique demonstrated the feasibility of adopting this new technique to investigate biomedical flows. This technique was used to quantify the three-dimensional velocity field in the vicinity of a validated, custom developed, transparent THV in a bench-top pulsatile flow loop. Large volumetric regions of flow stagnation were observed in the neo-sinus throughout the cardiac cycle, with stagnation defined as a velocity magnitude lower than 0.05 m s-1. The volumetric scalar viscous shear stress quantified via the three-dimensional shear stress tensor was within the range of low shear-inducing thrombosis observed in the literature. Such high-fidelity volumetric quantitative data and novel imaging techniques used to obtain it will enable fundamental investigation of heart valve thrombosis in addition to providing a reliable and robust database for validation of computational tools.

Motor cortex neurovascular coupling: inputs from ultra-high-frequency ultrasound imaging in humans.

Neurovascular coupling reflects the link between neural activity and changes in cerebral blood flow. Despite many technical advances in functional exploration of the brain, including functional MRI, there are only a few reports of direct evidence of neurovascular coupling in humans. The authors aimed to explore, for the first time in humans, the local cerebral blood flow of the primary motor cortex using ultra-high-frequency ultrasound (UHF-US) Doppler imaging to detect low blood flow velocity (1 mm/sec). Four consecutive patients underwent awake craniotomy for glioma resection using cortical direct electrostimulation for brain mapping. The primary motor cortical area eliciting flexion of the contralateral forearm was identified. UHF-US color Doppler imaging of this cortical area was acquired at rest, during repeated spontaneous forearm flexion, and immediately after the movement's termination. In each condition, the surface areas of the detectable vessels were measured after extraction of non-zero-velocity colored pixels and summed. During movement, local cerebral blood flow increased significantly by 14.4% (range 5%-30%) compared with baseline. Immediately after the termination of movements, the local hyperemia decreased significantly by 8.6% (range 1.9%-15.7%). To the authors' knowledge, this study is the first to provide a real-time demonstration of the neurovascular coupling in the human cortex by ultrasound imaging. They assume that UHF-US may be used to gather original and advanced data on brain functioning, which could be used to help in the identification of functional cortical areas during brain surgery.Clinical trial registration no.: NCT03179176 (clinicaltrials.gov).

Impact of dense “smoke” detected on transesophageal echocardiography on stroke risk in patients with atrial fibrillation undergoing catheter ablation

Spontaneous echocardiographic contrast ("smoke") within the left atrial cavity on transesophageal echocardiography (TEE) suggests low blood flow velocities in the heart that may lead to thromboembolic (TE) events. The purpose of this study was to evaluate the risk of TE events in the periprocedural period and at long-term follow-up in atrial fibrillation (AF) patients having dense smoke on preprocedural TEE. A total of 2511 patients undergoing AF ablation were included in this analysis. They were classified as group 1 (dense smoke detected on TEE at baseline; n = 234) and group 2 (no smoke on baseline TEE; n = 2277). Patients were followed up for TE events, which included both stroke and transient ischemic attacks (TIAs). In order to attenuate the observed imbalance in baseline covariates between the study groups, a propensity score matching technique was used (covariates were age, sex, AF type, diabetes, and CHADS2VASc score). In the periprocedural period, no TE events were reported in group 1 and 3 events (0.13%) were reported in group 2. At follow-up of 6.62 ± 2.01 years, 6 (2.6%) TE complications (2 TIA, 4 stroke) occurred in group 1 and 16 (0.70%) TE complications (6 TIA, 10 stroke) in group 2 (P = .004). In the propensity-matched population, 6 (2.56%) TE complications occurred in group 1 and 1 (0.2%) in group 2 (P = .007). In our study population, the presence of dense left atrial smoke did not show any correlation with periprocedural TE events in patients undergoing catheter ablation with uninterrupted anticoagulation. However, significant association was observed with late stroke/TIA, irrespective of CHA2DS2-VASc score.

Role of ultrasound doppler examination in choice of surgical tactics in portal hypertension

Introduction: Сhoice of surgical tactics in complicated portal hypertension (PH) is actual.More than 400 examinations of hepatic blood flow in patients with complicated PH, including 16 patients, operated by the method of liver tunneling, were fulfilled. Methods: One hundred protocols were chosen randomly. Comparison of distribution indices revealed different occurrence frequency of ultrasound symptoms of PH, having different etiology. Seventy patients with viral etiology of PH prevailed. Varix dilatation of cardia is revealed in 47% of patients. Splenorenal venous shunt (SRVS) is visualized in 43%, recanalization of umbilical vein - in 23% of patients. All types of anhepatic portosystemic shunts are visualized in majority of patients with cirrhosis of ethanol etiology. Liver is always enlarged in fatty hepatosis. In spite of low linear blood flow velocity in PV, its compensatory dilatation is not typical. Damage of PV architectonics is revealed in patients with subhepatic PH, enlargement of PV diameter is naturally absent, splenorenal venous shunt is always observed. Results: Ultrasound Doppler examination is the method of early diagnosis of PH type, its stage and prognosis of bleeding risk. It permits to choose optimal treatment method and evaluate its efficiency by comparison of indices before and after treatment. Conclusion: Indications to application of splenorenal venous anastomosis are doubtful due to natural formation of shunt in 43% of patients with viral hepatitis and 62% - with ethanol liver cirrhosis. Formation of SRVS in anhepatic PH is a compensatory mechanism. In this situation splenectomy or application of splenorenal venous anastomosis can be fatal.

Sensitivity analysis of geometrical parameters to study haemodynamics and thrombus formation in the left atrial appendage.

The left atrial appendage (LAA) is a complex and heterogeneous protruding structure of the left atrium (LA). In atrial fibrillation patients, it is the location where 90% of the thrombi are formed. However, the role of the LAA in thrombus formation is not fully known yet. The main goal of this work is to perform a sensitivity analysis to identify the most relevant LA and LAA morphological parameters in atrial blood flow dynamics. Simulations were run on synthetic ellipsoidal left atria models where different parameters were individually studied: pulmonary veins and mitral valve dimensions; LAA shape; and LA volume. Our computational analysis confirmed the relation between large LAA ostia, low blood flow velocities and thrombus formation. Additionally, we found that pulmonary vein configuration exerted a critical influence on LAA blood flow patterns. These findings contribute to a better understanding of the LAA and to support clinical decisions for atrial fibrillation patients.

Gender-differences in prevalence and outcome of ischemic stroke and promoting factors of atrial thrombi

BackgroundIschemic stroke is an important cause of death and disability. However, data about gender-differences in stroke are controversial. MethodsIn the nationwide sample, male and female inpatients were selected by screening for ischemic stroke by ICD-Code(I63) and compared. In a second study, we performed a retrospective analysis of patients who underwent transesophageal echocardiography (TEE) and screened for gender specific associations between clinical and echocardiographic parameters and atrial thrombi formation. ResultsMales had a higher incidence of ischemic stroke than females (372 vs. 340 per 100,000 citizens) with a substantial age-depending increase. Percentage of stroke patients with atrial fibrillation/flutter (AF, 34.2% vs. 26.5%) and the case-fatality rate (9.4% vs. 7.1%) were higher in females. AF seems to aggravate stroke events. In the retrospective study, 227 patients were enrolled (87 females (38.3%)). Females were older (IQR 72.0 (72.0–79.0) vs. 66.5 (57.3–76.8) years, P = 0.013), showed smaller right atrial (RA) area and slower blood flow velocity in left atrial appendage (LAA) (41.2 (29.2–58.5) vs. 50.0 (34.3–67.1) cm*sec−1, P = 0.038). Promoting factors of atrial thrombi in both genders were lower blood-flow velocity in LAA, larger LAA diameters, higher CHA2DS2-VASc-score and heart failure. AF, larger atrial septal-lateral diameters and areas were associated with atrial thrombi especially in males. ConclusionsOur study demonstrated gender-specific differences in ischemic stroke. Incidence of ischemic stroke was higher in males than in females increasing exponentially with growing age in both genders. Females had a higher case-fatality rate presumably due to higher rate of AF. Promoting factors of atrial thrombi differ especially regarding atrial volumes and blood flow velocity in the LAA.

Evaluation of Intraplaque Neovascularization Using Superb Microvascular Imaging and Contrast-Enhanced Ultrasonography

Several studies have shown a linkage between intraplaque neovascularization (IPN) and plaque instability. Although contrast-enhanced ultrasonography (CEUS) may help visualize IPN in the carotid artery, its benefits are limited in Japan, where there is no health insurance coverage for contrast agents in medical imaging. Superb microvascular imaging (SMI), however, enables the depiction of low-velocity blood flow. The current study compares the diagnostic accuracy of SMI and CEUS in the evaluation of IPN. The SMI and CEUS video images were transferred to a workstation and then analyzed to determine whether intraplaque blood flow signals were detected with SMI and whether plaques were contrast-enhanced with carotid artery CEUS. The images generated were independently interpreted by 2 radiologic technologists and 1 neurologist. Intraplaque enhancement was observed in 19 patients using CEUS while intraplaque blood flow signals were observed in 12 patients using SMI. A 100% specificity was recorded for SMI (all 12 patients with SMI-detected intraplaque blood flow showed contrast-enhanced plaques), while its sensitivity was 63% (8 of the 15 patients with no SMI-detected intraplaque blood flow showed contrast-enhanced plaques on CEUS). The results of this study show that patients with SMI-detected blood flow will tend to have plaque enhancement using CEUS. This suggests that SMI, as a simpler, safer, and noninvasive technique, can facilitate the visualization of carotid artery IPN without the use of a contrast agent, as well as in the clinical evaluation of plaque instability.

Visibility of the graft hepatic artery using superb microvascular imaging in liver transplantation recipients: initial experience.

Background Hepatic artery (HA) obstruction is one of the most threatening complications following liver transplantation (LT); however, conventional color Doppler imaging (CDI) suffers from technical limitations regarding the visualization of fine vessels and low-velocity blood flow. Purpose To test the visibility of HA in postoperative evaluation of LT using a superb microvascular imaging (SMI). Material and Methods This retrospective study was approved by our institutional review board. Fifty-five consecutive patients (58 grafts; mean age = 56 years) who underwent LT with Doppler ultrasonography (US) on postoperative day 1 were included. We compared the subjective visibility of HA and objective measurements of HA caliber, visible HA length on CDI, monochrome SMI (mSMI), contrast-enhanced mSMI (CE-mSMI), and contrast harmonic imaging (CHI). Reproducibility of HA caliber measurements on SMI techniques were also evaluated by using intraclass correlation coefficients (ICCs). Results The subjective image quality for visibility of HA tended to be graded higher with mSMI than CDI, and with CE-mSMI than mSMI ( P < 0.001). The overall reproducibility of HA caliber measurements was good to excellent for both mSMI and CE-mSMI (ICC = 0.674-0.855). HA caliber measurements on mSMI and CE-mSMI strongly correlated with CHI ( R = 0.785, 0.798, P < 0.001), while mean HA length on mSMI was significantly longer than on CDI (1.88 ± 0.83 vs. 1.42 ± 1.01cm, P = 0.004), and even longer on CE-mSMI (vs. 3.28 ± 1.11 cm, P < 0.001). Conclusion The mSMI technique shows good reproducibility and correlates well with currently used methods for postoperative evaluation of HA in LT recipients. It is further improved by administration of an US contrast agent.

Three-dimensional imaging of absolute blood flow velocity and blood vessel position under low blood flow velocity based on Doppler signal information included in scattered light from red blood cells

The development of a system for in vivo visualization of occluded distal blood vessels for diabetic patients is the main target of our research. We herein describe two-beam multipoint laser Doppler velocimetry (MLDV), which measures the instantaneous multipoint flow velocity and can be used to observe the blood flow velocity in peripheral blood vessels. By including a motorized stage to shift the measurement points horizontally and in the depth direction while measuring the velocity, the path of the blood vessel in the skin could be observed using blood flow velocity in three-dimensional space. The relationship of the signal power density between the blood vessel and the surrounding tissues was shown and helped us identify the position of the blood vessel. Two-beam MLDV can be used to simultaneously determine the absolute blood flow velocity distribution and identify the blood vessel position in skin.

Effects of predictive phased intervention on preventing lower extremity deep venous thrombosis in ICU patients

Objective To evaluate the preventive effects of predictive phased intervention on lower extremity deep vein thrombosis in ICU patients. Methods A total of 82 cases of critically ill patients admitted to our hospital from June 2013 to June 2016 were divided into observation group and control group according to the random number table method, with 41 cases respectively. Patients in the observation group received predictive phased intervention, while patients in the control group received routine nursing intervention. After 4 weeks of intervention, the lower extremity deep venous thrombosis rate, lower limb perimeter and blood flow velocity of lower extremity venous were compared between two groups. Results The incidence of lower extremity deep venous thrombosis was 2.44% in the observation group and 19.51% in the control group. The difference between two groups was statistically significant (χ2=6.604, P<0.05) . After the intervention, the lower limb perimeter of patients in the observation group was (30.01±2.34) cm, which was significantly lower than that of the control group; the venous blood flow velocity of the lower extremity of patients in the observation group was (25.43±3.01) cm/s, which was significantly higher than that of the control group (t=2.285, 2.357; P<0.05) . Conclusions Predictive phased intervention has obvious advantages in the prevention of lower extremity deep venous thrombosis in ICU patients and it is worth clinical promotion. Key words: Venous thrombosis; Intensive care units; Predictive phased intervention; Lower limb perimeter

A novel method to estimate blood flow velocity in the left atrial appendage using enhanced computed tomography: role of Hounsfield unit density ratio at two distinct points within the left atrial appendage

Low blood flow velocity in the left atrial appendage (LAA) indicates a high risk of thromboembolism. Although transesophageal echocardiography (TEE) has been the standard method with which to evaluate the LAA blood flow velocity, a clinically noninvasive method is desired. We hypothesized that the ratio of the Hounsfield unit (HU) density at two distinct points within the LAA represents the blood flow velocity in the LAA. We retrospectively investigated 60 consecutive patients with atrial fibrillation (paroxysmal type, n=29) who underwent enhanced computed tomography (CT) and TEE. The peak emptying flow velocity in the LAA (LAAPV) was evaluated using TEE. HU density was measured at proximal and distal sites of the LAA (LAAp and LAAd) on CT images. The LAAd/LAAp ratio was correlated with the LAAPV (P<0.01, r=0.69). Among several indices, the HU ratio was the most significant parameter associated with the LAAPV (β=0.469, CI 28.602-68.286, P<0.001). Receiver-operating characteristic analysis (area under the curve, 0.91) demonstrated that an HU density ratio cutoff of 0.32 discriminated a low LAAPV (<25cm/s) with sensitivity of 90% and specificity of 84%. Flow velocity of the LAA can be estimated by the HU density ratio at distal and proximal sites within the LAA. Our method might be a feasible substitution for TEE to discriminate patients with a reduced LAAPV.

A Comparison Between Compounding Techniques Using Large Beam-Steered Plane Wave Imaging for Blood Vector Velocity Imaging in a Carotid Artery Model.

Conventional color Doppler imaging is limited, since it only provides velocity estimates along the ultrasound beam direction for a restricted field of view at a limited frame rate. High-frame-rate speckle tracking, using plane wave transmits, has shown potential for 2-D blood velocity estimation. However, due to the lack of focusing in transmit, image quality gets reduced, which hampers speckle tracking. Although ultrafast imaging facilitates improved clutter filtering, it still remains a major challenge in blood velocity estimation. Signal dropouts and poor velocity estimates are still present for high beam-to-flow angles and low blood flow velocities. In this paper, ultrafast plane wave imaging was combined with multiscale speckle tracking to assess the 2-D blood velocity vector in a common carotid artery (CCA) flow field. A multiangled plane wave imaging sequence was used to compare the performance of displacement compounding, coherent compounding, and compound speckle tracking. Zero-degree plane wave imaging was also evaluated. The performance of the methods was evaluated before and after clutter filtering for the large range of velocities (0-1.5 m/s) that are normally present in a healthy CCA during the cardiac cycle. An extensive simulation study was performed, based on a sophisticated model of the CCA, to investigate and evaluate the performance of the methods at different pulse repetition frequencies and signal-to-noise levels. In vivo data were acquired of a healthy carotid artery bifurcation to support the simulation results. In general, methods utilizing compounding after speckle tracking, i.e., displacement compounding and compound speckle tracking, were least affected by clutter filtering and provided the most robust and accurate estimates for the entire velocity range. Displacement compounding, which uses solely axial information to estimate the velocity vector, provided most accurate velocity estimates, although it required sufficiently high pulse repetition frequencies in high blood velocity phases and reliable estimates for all acquisition angles. When this latter requirement was not met, compound speckle tracking was most accurate, because it uses the possibility to discard angular velocity estimates corrupted by clutter filtering. Similar effects were observed for in vivo data obtained at the carotid artery bifurcation. Investigating a combination of these two compounding techniques is recommended for future research.

Computational fluid dynamics analysis on recurrence of simple coiling intracranial aneurysms with remnant neck

Hemodynamic factors are considered to play an important role in the initiation and recurrence of cerebral aneurysms. However, hemodynamic characteristics leading to the recurrence of aneurysms is not well recognized. This study analyzes the hemodynamics of simple-coiling and remnant-neck aneurysms, and discusses the impact of hemodynamic factors on the recurrence of cerebral aneurysms. This study selected three simple-coiled and remnant-neck aneurysms with at least once angiographic follow-up. The follow-up was conducted by 3D rotational DSA and the 3D reconstruction of the vessel. The aneurysms located on ophthalmic segment of ICA, including one recurrent case and two stable cases. We used a porous medium model to simulate and analyze the hemodynamics of aneurysms. For the recanalized aneurysm, in the immediate post-operative period, the WSS at the remnant neck decreased, low blood flow velocity and stagnant regions were found in the aneurysm sac. In the first follow-up, compared to immediately post-operative, at the residual neck, the WSS was higher, the flow impingement was stronger. In the sac, the stagnation area decreased and its contour limit shrank into the aneurysm. However, in the second follow-up, compared to the previous follow-up, at the remnant neck, the WSS was lower, the flow impingement weaker, while in the sac the stagnant region expanded. Aneurysm recurrence could occur in two phases: early coil compaction resulting from blood flow impingement and later vessel remodeling due to hemodynamic effects.

Estimating Retinal Blood Flow Velocities by Optical Coherence Tomography.

While optical coherence tomography (OCT) angiography has been considered to evaluate retinal capillary blood flow instead of fluorescein angiography, the reflectance pattern of blood vessels on structural OCT might also provide retinal capillary flow data in the absence of fluorescein angiography. This potential has been insufficiently explored, despite promising data concerning a possible relationship between the reflectance pattern of blood vessels and their perfusion velocity in a laboratory setting. To evaluate the potential of retinal blood flow velocity estimation by structural OCT. Cross-sectional observational study conducted from June to November 2015 at a tertiary clinical referral center. Sixty arteries (the superior and inferior temporal arteries) from 30 eyes of 30 patients (17 female, 13 male) were included in the study. Based on the intraluminal contrast patterns of retinal arteries on OCT, 3 independent graders categorized the blood flow velocities as low, medium, or high. These results and the results from a software-based intraluminal contrast analysis were compared with the retinal blood flow velocities measured by video fluorescein angiography. Among the 30 eyes of 30 patients (mean [SD] age, 72.6 [12.3] years; 17 female, 13 male), 15 were controls without retinal occlusion, 6 had a branch retinal artery occlusion, and 9 had a central retinal artery occlusion. When discriminating between low flow velocities and medium or high flow velocities, the graders' sensitivity ranged from 88.2% to 100% (grader 1: 88.2%; 95% CI, 63.6%-98.5%; grader 2: 88.2%; 95% CI, 63.6%-98.5%; and grader 3: 100%; 95% CI, 69.8%-100%) and their specificity ranged from 97.6% to 100% (grader 1: 100%; 95% CI, 87.7%-100%; grader 2: 97.6%; 95% CI, 87.4%-99.9%; and grader 3: 100%; 95% CI, 87.7%-100%). The κ coefficients of the comparison between the 3 graders and the angiography were 0.77 (95% CI, 0.60-0.93; P < .001), 0.64 (95% CI, 0.44-0.83; P < .001), and 0.87 (95% CI, 0.74-0.99; P < .001). In the computer-based assessment, the contrast reduction of the intraluminal pattern could be numerically expressed in a specific coefficient in the model (I2, describing the angular change of the backscattering intensity in the model), which presented nonoverlapping intervals between low flow velocities and medium or high flow velocities (mean [SD] I2, 0.3 [5.3], 20.4 [6.4], and 21.7 [4.0], respectively). This study suggests that a low retinal blood flow velocity reflects in a visually distinct contrast reduction of the intraluminal pattern of retinal vessels on OCT. Larger studies are required to assess the clinical benefits.

SMI for imaging of placental infarction

Since superb Micro-vascular Imaging (SMI) is a new blood flow imaging technique that employs a unique algorithm to minimize motion artifacts, it can visualize low-velocity blood flow in small vessels. We demonstrate SMI imaging of the placental infarction in a case with fetal growth restriction, comparing a normal placenta on the same gestation. While SMI image in normal placenta clearly shows structures from the branching vessels to the peripheral villous trees in the cotyledons, they could not be seen in the case of fetal growth restriction. We think that the clinical value and future potential of SMI in placental evaluation have been clearly demonstrated.

Abstract 295: Importance of the Rate of Platelet Activation by Thrombin for Regulating the Size of Thrombi Formed Under Low Blood Flow Velocity Conditions

Background: Platelets, coagulation cascade including thrombin and fibrin, and fibrinolysis by plasmin along with blood flow are known to play regulatory roles in thrombogenesis. However, quantitative and interactive contribution of these factors are not fully understood. Method: We developed a computer simulation model of thrombi at sites of vessel injury by implementing quantitative parameters of blood flow, platelet, coagulation cascade and fibrinolysis. In this model, we defined thrombi as the area where the amount of activated platelet become 80% or more of the global platelet count of 3.0х10 5 /mm 3 upon vessel damage We have measured the 3-dimensional size of thrombi as defined in various conditions with various parameters of flow velocity, rate of platelet activation by thrombin, rate of thrombin production on the surface of activated platelets, rate of fibrinolysis and rate of plasmin production. Results: Rate of platelet activation by thrombin had the largest influence on the size of thrombi under low flow rate condition of 0.5 (cm/sec) (Fig1 A). When blood flow rate increased to 2.0 (cm/sec), the absolute importance of this parameter decreased (Fig1 B). Conclusion: Our results show that the rate of platelet activation by thrombin, which are signaled with PAR-1 receptor in human, has a marked effect on the size of thrombi in low flow rate condition suggesting the benefit of blocking this receptor in low blood flow condition such as venous thrombosis.

Arterial hypertension as a risk factor of intra-atrial thrombosis in patients with atrial fibrillation of non-valvular etiology

38 patients were examined (26 men and 12 women) aged 35 to 75 years with documented AF. Paroxysmal AF was diagnosed in 10 patients (26.32%). The persistent and permanent forms of arrhythmia were revealed in 14 cases (36.84%). Stage II-III hypertensive disease (HD) was diagnosed in 27 patients (71.1%). The transthoracic and transesophageal echocardiography was performed with the use of ultrasonic devices such as Aloka-SSD-4000 ProSound (Japan) and PhilipsIE 33 (USA). The analysis of results of echocardiography (both transthoracic and transesophageal) made it possible to detect intra-atrial clots in 54,8% of the patients with AF of non-valvular etiology. Atrial cavity thrombosis was registered in 15 of the 22 cases (68,2%) among the patients with hypertension as a direct cause of AF or another concomitant pathology. Lower blood flow velocity from the left atrial appendage was registered in hypertensive patients compared to those without hypertension - 29.0 (4.2) and 35.4 respectively (8.1) mm/s (p = 0.038; Student's t-test). The reduction of the peak bloodflow velocity in the left atrial appendage was proportional to the increase of hypertension (R = -0,861; p <0,001; R - Spearman's coefficient). The frequency of intra-atrial thrombosis did not depend on the form of atrialfibrillation and duration of the arrhythmic anamnesis. Hypertension is an independent predictor of thromboembolic complications in atrial fibrillation of non-valvular etiology.

Nursing intervention of deep vein thrombosis after major bone trauma

Objective To investigate the effect of nursing intervention on deep vein thrombosis after major bone trauma. Methods 59 cases of bone trauma surgery were selected as the research subjects, according to random number table method, they were randomly divided into the observation group and the control group.The patients of the control group received routine nursing care, and the patients of the observation group were given nursing intervention for postoperative deep vein thrombosis on the basis of the conventional nursing care.The pulmonary embolism, deep vein thrombosis and lower extremity swelling occurred rate before and after intervention of venous blood flow velocity, patients hospitalization time and quality of care scores were compared. Results The incidence rates of pulmonary embolism (0.0%), deep vein thrombosis (11.1%) and lower extremity swelling with postoperation (14.8%) of the observation group were significantly less than those in the control group(15.6%, 53.1%, 46.9%), there was significant differences (χ2=4.61, 11.54, 6.89, all P<0.05). After intervention, the lower extremity venous blood flow velocity of two groups [(20.9±5.3)cm/s, (27.5±7.4)cm/s] was significantly higher than before intervention [(19.2±4.6)cm/s, (19.8±5.3)cm/s], there was statistically significant difference (t=1.37, 4.40, all P<0.05). The stem prognosis of lower extremity venous blood flow velocity of the observation group [(27.5±7.4)cm/s] was significantly higher than (20.9±5.3)cm/s of the control group, there was significant difference (t=3.98, P<0.05). The hospitalization time in the observation group (45.2±5.4)d was less than (62.3±7.5)d in the control group, and the nursing quality score (98.7±1.1) was higher than (91.8±1.7) in the control group, and the differences were statistically significant (t=9.88, 18.12, all P<0.05). Conclusion Comprehensive nursing intervention can help improve venous blood flow velocity, reduce the incidence of deep vein thrombosis, shorten the hospital stay, and improve the quality of nursing. Key words: Hospital, osteopathic; Traumatology; Venous thromboembolism; Nursing care