Aortic Blood Flow Research Articles

Pulsatile blood flow in healthy aorta: An application of nonlinear evolution equation

Fluid flow dynamics in nature and its applications including hemodynamics are subjected to periodic velocity modulations. The nonlinear evolution equations are perused to understand such fundamental dynamical challenges in hemodynamics. Assuming cardiovascular hemodynamic system as a finite dissipative system and blood as an incompressible Newtonian fluid, a nonlinear evolution equation for pulsatile blood flow in the aorta during the cardiac cycle is modeled. The main results for generalized [Formula: see text]-dimensional nonlinear evolution equation, using the Lie group of transformations method are introduced. The implications of traveling wave solutions to describe the pulsatile blood flow in the aorta are discussed. It is found that the self-interactions among solitary waves along with generation of relatively small-scale and unstable wave fields contribute to turbulence.

Impaired Myocardial Mitochondrial Function in an Experimental Model of Anaphylactic Shock.

Simple SummaryAnaphylactic shock (AS) is the most severe allergic hypersensitivity reaction. In the early stage of shock, AS was associated with hemodynamic impairments: severe failure in arterial blood pressure and cardiac dysfunction. Mitochondrial disorders are associated with a high incidence of acute or chronic cardiac dysfunctions. The aim of the study was to evaluate mitochondrial involvement in cardiac dysfunction at the early stage of AS. In control (CON) and sensitized Brown Norway rats, anaphylactic shock (AS) was induced with ovalbumin iv bolus injection. Aortic abdominal blood flow (ABF), mean blood arterial pressure (MAP), and lactatemia were assessed during 15 min. The myocardial mitochondrial defect in AS was assessed by mitochondrial respiration, oxidative stress production, total superoxide dismutase activity (SODs), and oxidative damage. An ultrastructural evaluation of myocardial mitochondria was also performed using electronic microscopy. AS was associated with a rapid and dramatic decrease in MAP, ABF, and severe hyperlactatemia 15 min after AS induction. Non-phosphorylating mitochondrial respiration and OXPHOS states involving mitochondrial complex II were significantly impaired in the AS group. Oxidative stress was observed with a significant increase in SODs activity after AS induction. Moreover, in the AS group we observed an increase in oxidative damage via lipid peroxidation. No modifications of the mitochondrial ultrastructure were shown at the early stage of AS. In this experimental model, AS was associated with a rapid and significant myocardial mitochondrial dysfunction with oxidative damage that could explain cardiac anaphylaxis dysfunction.Anaphylactic shock (AS) is associated with a profound vasodilation and cardiac dysfunction. The cellular mechanisms underlying AS-related cardiac dysfunction are unknown. We hypothesized that myocardial mitochondrial dysfunction may be associated with AS cardiac dysfunction. In controls and sensitized Brown Norway rats, shock was induced by ovalbumin i.v bolus, and abdominal aortic blood flow (ABF), systemic mean arterial pressure (MAP), and lactatemia were measured for 15 min. Myocardial mitochondrial function was assessed with the evaluation of mitochondrial respiration, oxidative stress production by reactive oxygen species (ROS), reactive nitrogen species (RNS), and the measurement of superoxide dismutases (SODs) activity. Oxidative damage was assessed by lipid peroxidation. The mitochondrial ultrastructure was assessed using transmission electronic microscopy. AS was associated with a dramatic drop in ABF and MAP combined with a severe hyperlactatemia 15 min after shock induction. CI-linked substrate state (197 ± 21 vs. 144 ± 21 pmol/s/mg, p < 0.05), OXPHOS activity by complexes I and II (411 ± 47 vs. 246 ± 33 pmol/s/mg, p < 0.05), and OXPHOS activity through complex II (316 ± 40 vs. 203 ± 28 pmol/s/mg, p < 0.05) were significantly impaired. ROS and RNS production was not significantly increased, but SODs activity was significantly higher in the AS group (11.15 ± 1.02 vs. 15.50 ± 1.40 U/mL/mg protein, p = 0.02). Finally, cardiac lipid peroxidation was significantly increased in the AS group (8.50 ± 0.67 vs. 12.17 ± 1.44 µM/mg protein, p < 0.05). No obvious changes were observed in the mitochondrial ultrastructure between CON and AS groups. Our experimental model of AS results in rapid and deleterious hemodynamic effects and was associated with a myocardial mitochondrial dysfunction with oxidative damage and without mitochondrial ultrastructural injury.

Velocity-Encoded Phase-Contrast MRI for Measuring Mesenteric Blood Flow in Patients With Newly Diagnosed Small-Bowel Crohn Disease.

BACKGROUND. Intestinal inflammation is associated with radiologic and histologic hyperemia. A paucity of studies have used MRI to measure mesenteric blood flow in patients with Crohn disease. OBJECTIVE. The purpose of this study was to evaluate the application of velocity-encoded phase-contrast MRI for measuring mesenteric blood flow in patients with newly diagnosed small-bowel Crohn disease. METHODS. This prospective study included 20 patients with ileal Crohn disease newly diagnosed between December 2018 and October 2021 (eight female participants, 12 male participants; median age, 14.0 years), and 15 healthy control participants (eight female participants, seven male participants; median age, 17.0 years). Patients with Crohn disease underwent investigational MRI and laboratory assessments at diagnosis and at 6 weeks and 6 months after initiating anti-tumor necrosis factor-α medical therapy; control participants underwent a single investigational MRI examination. All MRI examinations included a velocity-encoded phase-contrast acquisition, which was used to measure blood flow in the abdominal aorta, superior mesenteric artery (SMA), and superior mesenteric vein (SMV). Mann-Whitney U test was used to compare blood flow measurements (ratios of SMA and SMV blood flow to aorta blood flow [hereafter, SMA-to-aorta and SMV-to-aorta blood flow, respectively]) between groups; Friedman test was used to evaluate temporal changes in blood flow. Spearman correlation was used to assess relationships between blood flow measurements and laboratory markers of intestinal inflammation. Diagnostic performance was assessed by ROC analysis. RESULTS. At baseline, SMA-to-aorta blood flow in patients versus control participants was 0.44 versus 0.30 (p = .003), and SMV-to-aorta blood flow was 0.36 versus 0.21 (p = .002). At 6 weeks and 6 months, SMA-to-aorta blood flow in patients decreased to 0.30 and 0.27 (p < .001), and SMV-to-aorta blood flow decreased to 0.27 and 0.21 (p = .02), respectively. SMA-to-aorta and SMV-to-aorta blood flow were positively correlated with C-reactive protein (rho, 0.34 [p = .01] and 0.35 [p = .008], respectively) and fecal calprotectin (rho, 0.34 [p = .01] vs 0.47 [p < .001]). AUCs for differentiating patients from controls were 0.79 for SMA-to-aorta (sensitivity, 60%; specificity, 100%) and 0.82 for SMV-to-aorta (sensitivity, 75%; specificity, 87%) blood flow. CONCLUSION. Mesenteric blood flow is quantifiable using velocity-encoded phase-contrast MRI. The measurements differ between patients with ileal Crohn disease and healthy control participants and change in response to medical therapy. CLINICAL IMPACT. MRI-based mesenteric blood flow measurements provide a potential novel marker of intestinal inflammation.

Aortic-tibial transiliac wing extra-anatomic bypass with distal fistula for treatment of an infected deep femoral pseudoaneurysm.

Transiliac wing bypass has been reported to be a viable extra-anatomic alternative technique for patients presenting with a history of groin infection or irradiation.1Enzmann F.K. Nierlich P. Eder S.K. Aspalter M. Dabernig W. Aschacher T. et al.Trans-iliac bypass grafting for vascular groin complications.Eur J Vasc Endovasc Surg. 2019; 58: 930-935Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar Of the 32 reported cases, only two patients had undergone transiliac aortic–tibial or iliotibial bypass.2Sekanina G. Lemminger F. Bruecher D. Iliaco-crural bypass through a borehole in the iliac fossa as extra-anatomic vascular bypass in infected inguinal canal and posterior aspect of the knee.Chirurg. 1995; 66: 142-145PubMed Google Scholar,3Heldenberg E. Lorber J. Cheyn D. Bass A. Transiliac wing alternate route bypass for infected groin vascular graft.J Vasc Surg. 2014; 60: 504-505Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar We report the case of a 72-year-old man with a complex history of multiple lower limb revascularizations, who had been admitted for a deep femoral infected anastomotic pseudoaneurysm (A) and left chronic limb threatening ischemia. Computed tomography showed chronic occlusions at the femoropopliteal level, with a previous thrombosed obturator canal bypass. The only patent lower leg artery was the posterior tibial artery (PTA) from its mid-third to the foot.A transiliac wing aortic–tibial prosthetic bypass was performed through a pararectal retroperitoneal approach (B/Cover). The infrarenal aorta and common iliac arteries were cross-clamped before implanting an 8-mm expanded polytetrafluoroethylene graft soaked in rifampicin at the terminal aorta level. It was tunneled into the retroperitoneal space, over the psoas muscle. A U-shape osteotomy was performed at the anterior left iliac wing border through a second lateral incision to guide the bypass. Another incision was made at the lateral side of the thigh to guide the graft route between the femoral condyles. It was associated with a distal arteriovenous bypass between the PTA and a fibular vein (C), before the distal anastomosis of the aortic–tibial bypass, to partially deviate the aortic blood flow from the PTA into the venous circulation.The second part of the procedure consisted of deep femoral pseudoaneurysm repair. It was developed at the distal anastomosis level of the thrombosed obturator canal bypass, which was removed to the obturator canal during the same procedure. The deep femoral artery was then ligated with 5-0 polypropylene suture. Transiliac wing bypass has been reported to be a viable extra-anatomic alternative technique for patients presenting with a history of groin infection or irradiation.1Enzmann F.K. Nierlich P. Eder S.K. Aspalter M. Dabernig W. Aschacher T. et al.Trans-iliac bypass grafting for vascular groin complications.Eur J Vasc Endovasc Surg. 2019; 58: 930-935Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar Of the 32 reported cases, only two patients had undergone transiliac aortic–tibial or iliotibial bypass.2Sekanina G. Lemminger F. Bruecher D. Iliaco-crural bypass through a borehole in the iliac fossa as extra-anatomic vascular bypass in infected inguinal canal and posterior aspect of the knee.Chirurg. 1995; 66: 142-145PubMed Google Scholar,3Heldenberg E. Lorber J. Cheyn D. Bass A. Transiliac wing alternate route bypass for infected groin vascular graft.J Vasc Surg. 2014; 60: 504-505Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar We report the case of a 72-year-old man with a complex history of multiple lower limb revascularizations, who had been admitted for a deep femoral infected anastomotic pseudoaneurysm (A) and left chronic limb threatening ischemia. Computed tomography showed chronic occlusions at the femoropopliteal level, with a previous thrombosed obturator canal bypass. The only patent lower leg artery was the posterior tibial artery (PTA) from its mid-third to the foot. A transiliac wing aortic–tibial prosthetic bypass was performed through a pararectal retroperitoneal approach (B/Cover). The infrarenal aorta and common iliac arteries were cross-clamped before implanting an 8-mm expanded polytetrafluoroethylene graft soaked in rifampicin at the terminal aorta level. It was tunneled into the retroperitoneal space, over the psoas muscle. A U-shape osteotomy was performed at the anterior left iliac wing border through a second lateral incision to guide the bypass. Another incision was made at the lateral side of the thigh to guide the graft route between the femoral condyles. It was associated with a distal arteriovenous bypass between the PTA and a fibular vein (C), before the distal anastomosis of the aortic–tibial bypass, to partially deviate the aortic blood flow from the PTA into the venous circulation. The second part of the procedure consisted of deep femoral pseudoaneurysm repair. It was developed at the distal anastomosis level of the thrombosed obturator canal bypass, which was removed to the obturator canal during the same procedure. The deep femoral artery was then ligated with 5-0 polypropylene suture. Appendix

Contrast Agent-Free Assessment of Blood Flow and Wall Shear Stress in the Rabbit Aorta using Ultrasound Image Velocimetry.

Blood flow velocity and wall shear stress (WSS) influence and are influenced by vascular disease. Their measurement is consequently useful in the laboratory and clinic. Contrast-enhanced ultrasound image velocimetry (UIV) can estimate them accurately but the need to inject contrast agents limits utility. Singular value decomposition and high-frame-rate imaging may render contrast agents dispensable. Here we determined whether contrast agent-free UIV can measure flow and WSS. In simulation, accurate measurements were achieved with a signal-to-noise ratio of 13.5 dB or higher. Signal intensity in the rabbit aorta increased monotonically with mechanical index; it was lowest during stagnant flow and uneven across the vessel. In vivo measurements with contrast-free and contrast-enhanced UIV differed by 4.4% and 1.9% for velocity magnitude and angle and by 9.47% for WSS. Bland–Altman analysis of waveforms revealed good agreement between contrast-free and contrast-enhanced UIV. In five rabbits, the root-mean-square errors were as low as 0.022 m/s (0.81%) and 0.11 Pa (1.7%). This study indicates that with an optimised protocol, UIV can assess flow and WSS without contrast agents. Unlike contrast-enhanced UIV, contrast-free UIV could be routinely employed.

Prediction of fluid responsiveness following liver compression in pediatric patients with single ventricle physiology.

The role of liver compression in predicting fluid responsiveness in children with a single ventricle has never been evaluated. The purpose of this study was to assess whether blood pressure changes during liver compression predict fluid responsiveness in children with single ventricle physiology. This prospective, interventional study included children aged 3months to 5years who underwent surgery for bidirectional cavopulmonary shunt or extracardiac Fontan operation. Before fluid loading, the right upper abdomen was compressed at 30mmHg for 10s, and changes in the blood pressure waves were recorded before administering 10mlkg-1 of crystalloid solution. Systolic arterial pressure, diastolic arterial pressure, central venous pressure, pleth variability index, respiratory variation in aortic blood flow peak velocity, and stroke volume were measured before and after fluid loading. A volume responder was defined as a patient with >15% increase in stroke volume index. Thirty patients underwent bidirectional cavopulmonary shunt (15 responders and 15 non-responders), and 32 underwent Fontan surgery (17 responders and 15 non-responders). In children with bidirectional cavopulmonary shunt, Δsystolic arterial pressure>8mmHg (sensitivity 76.9% and specificity 93.3%), Δdiastolic arterial pressure>7mmHg (sensitivity 69.2% and specificity 93.3%), and Δmean arterial pressure>7mmHg (sensitivity 69.2% and specificity 100%) during liver compression predicted fluid responsiveness. The areas under the receiver operating characteristic curves of Δsystolic arterial pressure, Δdiastolic arterial pressure, and Δmean arterial pressure were 0.928, 0.859, and 0.874 (all p<.001). In children who underwent Fontan surgery, only Δsystolic arterial pressure>16mmHg was predictive of fluid responsiveness (sensitivity of 41.2% and specificity of 100%), with the areas under the receiver operating characteristic curves curve of 0.786 (p<.001). Pleth variability index and respiratory variation in aortic blood flow peak velocity had no predictive value for fluid responsiveness after both types of surgeries. In BCPS patients, liver compression increases the inferior vena cava flow which directly leads to an increase in preload. On the other hand, blood flow from the liver drains directly into the pulmonary arteries in Fontan circulation. Because of this characteristics for preload determination, the clinical application of liver compression to monitor hemodynamic changes might be more useful in patients with bidirectional cavopulmonary shunt than those with Fontan circulation. Increase in blood pressure induced by liver compression is predictive of fluid responsiveness in children with single ventricle physiology.

Hemodynamics and Wall Shear Stress of Blood Vessels in Aortic Coarctation with Computational Fluid Dynamics Simulation

The purpose of this study was to identify the characteristics of blood flow in aortic coarctation based on stenotic shape structure, stenosis rate, and the distribution of the wall load delivered into the blood vessels and to predict the impact on aneurysm formation and rupture of blood vessels by using a computational fluid dynamics modeling method. It was applied on the blood flow in abdominal aortic blood vessels in which stenosis occurred by using the commercial finite element software ADINA on fluid-solid interactions. The results of modeling, with an increasing stenosis rate and Reynolds number, showed the pressure drop was increased and the velocity was greatly changed. When the stenosis rate was the same, the pressure drop and the velocity change were larger in the stenosis with a symmetric structure than in the stenosis with an asymmetric one. Maximal changes in wall shear stress were observed in the area before stenosis and minimal changes were shown in stenosis areas. The minimal shear stress occurred at different locations depending on the stenosis shape models. With an increasing stenosis rate and Reynolds number, the maximal wall shear stress was increased and the minimal wall shear stress was decreased. Through such studies, it is thought that the characteristics of blood flow in the abdominal aorta where a stenosis is formed will be helpful in understanding the mechanism of growth of atherosclerosis and the occurrence and rupture of the abdominal aortic flow.

Novel Methods for Predicting Fluid Responsiveness in Critically Ill Patients-A Narrative Review.

In patients with acute circulatory failure, fluid administration represents a first-line therapeutic intervention for improving cardiac output. However, only approximately 50% of patients respond to fluid infusion with a significant increase in cardiac output, defined as fluid responsiveness. Additionally, excessive volume expansion and associated hyperhydration have been shown to increase morbidity and mortality in critically ill patients. Thus, except for cases of obvious hypovolaemia, fluid responsiveness should be routinely tested prior to fluid administration. Static markers of cardiac preload, such as central venous pressure or pulmonary artery wedge pressure, have been shown to be poor predictors of fluid responsiveness despite their widespread use to guide fluid therapy. Dynamic tests including parameters of aortic blood flow or respiratory variability of inferior vena cava diameter provide much higher diagnostic accuracy. Nevertheless, they are also burdened with several significant limitations, reducing the reliability, or even precluding their use in many clinical scenarios. This non-systematic narrative review aims to provide an update on the novel, less employed dynamic tests of fluid responsiveness evaluation in critically ill patients.

Computational Fluid Dynamics to Assess the Future Risk of Ascending Aortic Aneurysms.

ResumoFundamentos Uma metodologia para identificação de pacientes portadores de aneurisma de aorta ascendente (AAAs) sob alto risco de remodelamento aórtico não está completamente definida.Objetivo Esta pesquisa objetiva caracterizar numericamente o fluxo sanguíneo aórtico, relacionando a distribuição do estresse mecânico resultante com o crescimento de AAAs.Métodos Estudo analítico, observacional, unicêntrico, em que um protocolo de fluidodinâmica computacional (CFD - Computacional Fluid Dynamics) foi aplicado a imagens de angiotomografia computadorizada (ATC) de aorta de pacientes portadores de AAAs. Duas ATC de aorta com pelo menos um ano de intervalo foram obtidas. Dados clínicos dos pacientes foram registrados e, a partir das imagens de ATC, foram gerados modelos tridimensionais. Foram realizados estudos do campo de velocidade e estruturas coerentes (vórtices) com o objetivo de relacioná-los ao crescimento ou não do aneurisma e, posteriormente, compará-los com os dados clínicos dos pacientes. O teste de Kolmogorov-Smirnov foi utilizado para avaliar a normalidade da amostra e o teste não-paramétrico Wilcoxon signed-rank foi aplicado para comparações de dados pareados entre os ângulos aórticos. A significância estatística foi fixada em 5%.Resultados Para o grupo que apresentou crescimento do aneurisma, a incidência do jato na parede aórtica gerou áreas de recirculação posterior ao jato, induzindo à formação de vórtices complexos, ocasionando um incremento na pressão média no endotélio aórtico. O grupo sem crescimento do aneurisma apresentou diminuição na pressão média.Conclusão Este estudo piloto mostrou que a CFD baseada em ATC pode, em um futuro próximo, ser uma ferramenta auxiliar na identificação dos padrões de fluxo associados ao processo de remodelamento de AAAs.

Utility of Transfontanelle Ultrasound in Predicting the Fluid Responsiveness in Children After Repair of Congenital Heart Diseases: A Prospective Observational Study

Postoperative fluid management in children undergoing cardiac surgery requires a balanced optimization. The blood flow velocity variation in the internal carotid artery (ΔICA) measured through transfontanelle ultrasound has been shown to predict fluid responsiveness during cardiac surgery. It may provide an excellent window to study fluid responsiveness in infants during the postoperative period when the intensivist is faced with the challenges of poor echocardiographic window. The authors aimed to observe the correlation between ΔICA measured on transfontanelle ultrasound with the respiratory variability of peak aortic blood flow velocity (ΔVpeak) on transthoracic echocardiography as a marker of fluid responsiveness in infants on mechanical ventilation during the postoperative period after cardiac surgery. A prospective observational study. The postcardiac surgery intensive care unit (ICU) of a tertiary care hospital. Thirty infants undergoing congenital cardiac surgery. A fluid bolus of 10 mL/kg administered over 10 minutes at 1 and 6 hours after ICU admission. Patients were categorized into fluid responders and nonresponders based on >15% increase in the indexed stroke volume. A total of 50 fluid boluses were administered in 30 patients. Among these, 22 (73.33%) were responders and 8 (26.67%) were nonresponders. There was moderate correlation between ΔICA and peak aortic blood flow velocity variation (ΔVpeak) (r=0.59, p ≤ 0.001). The ΔVpeak >14.74% had 68% sensitivity and 75% specificity to predict fluid responsiveness (area under the receiver operating characteristic [AUROC], 0.749; p=0.001; positive likelihood ratio, 2.71; negative likelihood ratio, 0.43). The ΔICA >9.85% could predict fluid responsiveness in infants (AUROC, 0.728; p=0.003; 75% sensitivity; 60% specificity; positive likelihood ratio, 1.85; negative likelihood ratio, 0.42). Among children younger than 6 months, ΔICA >9.85% was a better predictor of fluid responsiveness (AUROC, 0.889; p=0.009) than ΔVpeak >15% (AUROC, 0.778; p=0.061). The ICA variability >9.85% measured via transfontanelle ultrasound is a good predictor of fluid responsiveness in infants, especially those younger than 6 months on mechanical ventilation after cardiac surgery.

Unraveling Bicuspid Aortic Valve Enigmas by Multimodality Imaging: Clinical Implications.

Multimodality imaging is the basis of the diagnosis, follow-up, and surgical management of bicuspid aortic valve (BAV) patients. Transthoracic echocardiography (TTE) is used in our clinical routine practice as a first line imaging for BAV diagnosis, valvular phenotyping and function, measurement of thoracic aorta, exclusion of other aortic malformations, and for the assessment of complications such are infective endocarditis and aortic. Nevertheless, TTE is less useful if we want to assess accurately other aortic segments such as mid-distal ascending aorta, where computed tomography (CT) and magnetic resonance (CMR) could improve the precision of aorta size measurement by multiplanar reconstructions. A major advantage of CT is its superior spatial resolution, which affords a better definition of valve morphology and calcification, accuracy, and reproducibility of ascending aorta size, and allows for coronary artery assessment. Moreover, CMR offers the opportunity of being able to evaluate aortic functional properties and blood flow patterns. In this setting, new developed sequences such as 4D-flow may provide new parameters to predict events during follow up. The integration of all multimodality information facilitates a comprehensive evaluation of morphologic and dynamic features, stratification of the risk, and therapy guidance of this cohort of patients.

Morphometric Analysis of the Aorto-Esophageal Relationship in Swine for Trans-Esophageal Aortic Blood Flow Occlusion

Background&#x0D; Trans-esophageal aortic blood flow occlusion (TEABO) is an emerging technology undergoing laboratory research that offers a strategy for temporary hemorrhage control. The purpose of this study was to evaluate the anatomical relationship between the esophagus and descending thoracic aorta in two breeds of swine to support a porcine model for future TEABO investigations.&#x0D; Methods &#x0D; Thoracoabdominal CT scans were compared in Hanford miniature swine and Yorkshire swine. Measurements were taken at the five vertebral levels proximal to the gastroesophageal junction. Data collected included the distance between the center of the esophagus and the center of the descending aorta, the angle between the vertebral column, descending aorta, and esophagus, and the length the thoracic esophagus travels anteriorly to the descending aorta.&#x0D; Results &#x0D; Ten Hanford swine and ten Yorkshire swine were compared. In Hanford swine, the distal thoracic esophagus travels anteriorly to the descending aorta for a mean distance of 11.5 ± 2.3 cm. In Yorkshire swine, the thoracic esophagus travels to the right of the descending aorta. The mean angle between the vertebral body, descending aorta, and esophagus was 79.6 to 97.8 degrees higher in Hanfords compared to Yorkshires (p&lt;0.0001 at all five vertebral levels compared). The mean distance between the esophagus and descending aorta was 0.2 to 0.6 cm higher in Hanfords compared to Yorkshires with a significant difference found at only two vertebral levels (p=0.01 and p=0.02).&#x0D; Conclusion &#x0D; Hanford miniature swine possess an aorto-esophageal relationship comparable to humans and should be the preferred animal model for TEABO studies.

Aortic Pulse Wave Velocity Evaluated by 4D Flow MRI Across the Adult Lifespan.

Evaluation of aortic stiffness by pulse wave velocity (PWV) across the adult lifespan is needed to better understand normal aging in women and men. To characterize PWV in the thoracic aorta using 4D flow MRI in an age- and sex-stratified cohort of healthy adults. Retrospective. Ninety nine healthy participants (age: 46 ± 15 [19-79] years, 50% female), divided into young adults (<45 years) (N=48), midlife (45-65 years) (N=37), and later life (>65 years) (N=14) groups. 1.5 T or 3T, 2D cine bSSFP, 4D flow MRI. Cardiac functional parameters of end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and myocardial mass were assessed by 2D cine bSSFP. PWV and aortic blood flow velocity were assessed by 4D flow MRI. Reproducibility of PWV was evaluated in a subset of nine participants. Analysis of variance, Pearson's correlation coefficient (r), linear regression, intraclass correlation coefficient (ICC). A P value < 0.05 was considered statistically significant. PWV increased significantly with age (young adults: 5.4 ± 0.9m/sec, midlife: 7.2 ± 1.1m/sec, and later life: 9.4 ± 1.8m/sec) (r=0.79, slope=0.09 m/sec/year). PWV did not differ in women and men in entire sample (P=0.40) or within age groups (young adults: P=0.83, midlife: P=0.17, and later life: P=0.96). PWV was significantly correlated with EDV (r=-0.29), ESV (r=-0.23), SV (r=-0.28), myocardial mass (r=0.21), and mean aortic blood flow velocity (r=-0.62). In the test-retest subgroup (N=9), PWV was 6.7 ± 1.5 [4.4-9.3] m/sec and ICC=0.75. 4D flow MRI quantified higher aortic PWV with age, by approximately 1m/sec per decade, and significant differences between young adults, midlife and later life. Reproducibility analysis showed good test-retest agreement. Increased PWV was associated with decline in cardiac function and reduced aortic blood flow velocity. This study demonstrates the utility of 4D flow MRI-derived aortic PWV for studying aging. 2 TECHNICAL EFFICACY: Stage 2.

The effects of vasopressors with and without dobutamine on haemodynamics, metabolism and gut injury during endotoxic shock in rabbits. Acontrolled study.

Vasopressors increase arterial pressure but they may have deleterious effects on mesenteric blood flow. We aimed to evaluate the response of gut biomarkers and superior mesenteric blood flow to different vasopressors with and without dobutamine. Thirty New Zealand rabbits were included and randomly allocated to 5 groups: group A- sham group; group B - norepinephrine; group C - norepinephrine plus dobutamine; group D - vasopressin; and group E - vasopressin plus dobutamine. Mean arterial pressure (MAP) target was greater than 60 mmHg. Endotoxic shock was induced by intra-venous injection of lipopolysaccharide (LPS) in four of the five groups. Aortic blood flow (Qao), superior mesenteric artery flow (QSMA) and lactate were measured after LPS injection. Enterocyte damage was evaluated by measurements of serum citrulline and intestinal fatty acid-binding protein (I-FABP) after 4 h. The largest reduction in Qao occurred in group D (64 ± 17.3 to 38 ± 7.5 mL min-1; P = 0.04). QSMA also declined significantly in groups D and E and remained lower than in the other groups over 4 h (group D - baseline: 65 ± 31; 1 h: 37 ± 10; 2 h: 38 ± 10; 3 h: 46 ± 26; and 4 h: 48 ± 15 mL min-1; P < 0.005; group E - baseline: 73 ± 14; 1 h: 28 ± 4.0; 2 h: 37 ± 6.4; 3 h: 40 ± 11; and 4 h: 48 ± 11; P < 0.005; all in mL min-1). Serum citrulline was significantly lower in groups D (P = 0.014) and E (P = 0.019) in comparison to group A. The fluid administration regimen was similar in all groups. Vasopressin seems to negatively impact gut enterocyte function during endotoxic shock despite the association of an inodilator and adequate fluid replacement.

Fluid Structure Interaction Analysis of Aorta Using OpenFOAM and CalculiX

Currently, biomechanical simulations of blood vessels and organs are widely used in medical research, and it is expected to realize rapid and accurate medical diagnosis by personalized biological simulations for each individual using high-speed and high-precision 3D modeling of the body internal geometry by Multi Detector-row Computed Tomography (MDCT) and Magnetic Resonance Imaging (MRI). In particular, biomechanical simulation approach using Open Source Software (OSS) has been developed for use in the medical field, and recently, its application to more challenging multiphysics simulation has been studied. However, OSS has many issues such as assurance of accuracy and validity of the analysis, the computation time and stability of Fluid-Structure Interaction (FSI), and the lack of analysis functions for complex phenomena. In particular, blood flow simulation using OpenFOAM, a fluid analysis OSS, has issues in the representation of blood pressure changes caused by pulsation and body movement, and the stability of coupled analysis in conjunction with other structural analysis software. In this study, we added the Windkessel model, which is one of the models for expressing blood pressure changes, to OpenFOAM and developed a two-way coupled multi-physics simulation approach using OpenFOAM and CalculiX. As an example of personalized biomechanical simulation, we applied the method to simulate blood flow in the thoracic aorta and evaluated its effectiveness.

Application value of bedside ultrasound for assessing volume responsiveness in patients with septic shock

Background/Aim. Septic shock is a serious complication that can occur as consequence of infection. As the effective circulating blood volume is of vital importance in these cases, it is very important to keep track of this parameter constantly. The aim of this study was to explore the application value of bedside ultrasound for assessing volume responsiveness in patients with septic shock. Methods. A total of 102 patients with septic shock were selected. The volume load (VL) test was performed, and based on the results of the test, the patients were divided into the response group that had an increase in stroke volume (?SV ) ? 15% and non-response group (?SV &lt; 15%). Hemodynamic parameters were compared before and after the test. The correlation between ?SV and each hemodynamic index was explored by Pearson?s analysis. The receiver operating characteristic (ROC) curve was plotted. Results. There were 54 patients in response group and 48 patients in non-response group. Before VL test, retro-hepatic inferior vena cava (IVC) distensibility index (?IVC1), respiratory variation in IVC index (?IVC2), respiratory variation in aortic blood flow peak velocity index (?VpeakAO), respiratory variation in brachial artery blood flow peak velocity index (?VpeakBA) and respiratory variation in common femoral artery blood flow peak velocity index (?VpeakCFA) were all higher in response group than those in non-response group (p &lt; 0.05), while heart rate (HR), mean arterial pressure (MAP) and central venous pressure (CVP) were similar (p &gt; 0.05). After VL test, response group had significantly decreased HR, ?IVC1, ?IVC2, ?VpeakAO, ?VpeakBA and ?VpeakCFA, and increased MAP and CVP (p &lt; 0.05), while non-response group had significantly decreased CVP (p &lt; 0.05) and no significant changes in other indices. ?IVC1, ?IVC2, ?VpeakAO, ?VpeakBA and ?VpeakCFA significantly correlated with ?SV ( r= 0.589, r = 0.647, r = 0.697, r = 0.621, r = 0.766, p &lt; 0.05), but there was no correlation between CVP and ?SV (r = -0.345, p &gt; 0.05). The areas under the curves of ?IVC1, ?IVC2, ?VpeakAO, ?VpeakBA and ?VpeakCFA for predicting volume responsiveness were 0.839, 0.858, 0.878, 0.916 and 0.921, respectively, which were significantly larger than that of CVP (0.691), indicating higher sensitivity and specificity. Conclusion. Bedside ultrasound monitoring of ?IVC, ?VpeakAO, ?VpeakBA and ?VpeakCFA can better assess the volume responsiveness in patients with septic shock.

Heat transfer and hemodynamic analysis of systolic and diastolic hypertension on abdominal aortic thrombosis

Thrombosis is a blood clot formed in the vascular system and obstructs blood flow by reducing the cross-sectional area of blood vessels, posing a great threat to human health. Computational hemodynamics is a well-known method used for numerical simulation of blood flow behaviour. Diastolic and systolic hypertension can be investigated using the FVM and SIMPLE scheme for pressure-velocity coupling. Thanks to the utilization of MRI and DICOM, there is an acceptable 3D geometric accuracy based on which the geometry was constructed. In this study, a numerical study was performed on the behavior of the non-Newtonian blood flow in the abdominal aorta with different shapes of thrombus in three thermal fluxes generated by the body (i.e., running, sleeping, and standing). So, Blood flow behavior in three thrombus shapes of circular, rectangular, and triangular was also explored. This paper reported the influence of dimensionless numbers, including pressure drop, heat transfer coefficient, temperature, and Average Wall Shear Stress (AWSS). Based on clinical data, velocities in the abdominal aorta range from 1 to 1.2 m s−1, and blood temperature is 309.55 K. The results showed that the triangular thrombus was the most effective.

Hemodynamic evaluation of different stent graft schemes in aortic arch covered stent implantation

Implantation of the left subclavian artery (LSA) stent graft used in fenestration technique of the thoracic endovascular aortic repair (TEVAR) may interfere with the aortic helical blood flow that is believed to have important protective functions against atherogenesis. The present study investigated four different LSA stent graft implantation schemes for their resulted blood flow patterns in the thoracic aortic with hemodynamic computational simulation methods: the flush branch (FB), the protruding branch (PB), the straight cuff branch (SCB) and the cured cuff branch (CCB). The results showed that the PB scheme could slightly enhance helicity of the swirling flow in the aorta, but the other three schemes had less effect on blood flow helicity. The PB scheme produced low-TAWSS, high-OSI and high-RRT around the LSA root, and the FB scheme had similar TAWSS, OSI and RRT in both value and distribution to those in the aorta without LSA stent graft implantation. The SCB and CCB schemes led to less area of high-OSI and high-RRT values along the walls of the LSA branch arteries. The results also showed that the PB scheme would significantly reduce blood supply to the LSA, on the contrary, the CCB scheme enhanced LSA blood supply and less effect on the total blood supply to the three branches of the thoracic aorta. In summary, all of the four schemes have no significant effect on the aortic swirling flow, however, in the terms of TAWSS, OSI, RRT and blood supply to the LSA, the CCB model might be the best option with less area of low-WSS, high-OSI, high-RRT and well blood supply in the LSA.

Multi‐layered tissue models in patient‐specific simulations of aortic dissection

AbstractIn aortic dissections blood flows not only in the regular, true lumen but also between separated lamellae within the media of the aortic wall, in the so‐called false lumen. Both lumina are separated by a dissection membrane, which may move substantially during the cardiac cycle, linking blood flow and vessel deformation. We employ strongly coupled fluid‐structure interaction simulations incorporating an anisotropic, fiber‐reinforced, hyperelastic continuum including layer‐specific tissue parameters.

Noninvasive Bioreactance-Based Fluid Management Monitoring: A Review of Literature

AbstractBody fluid balance is an independent predictor of mortality. For each liter of fluid over and above 5 L, risk-adjusted excess mortality is seen. Mortality increased by 2.3% for each 1 L of fluid and hospital costs increased by $999. Accordingly, most recent guidelines have endorsed dynamic modeling. Passive leg raising-induced increase of aortic blood flow ≥ 10% predicts fluid responsiveness with a sensitivity of 97% and a specificity of 94%. Thus, passive leg raising is often used as gold standard for validation of other procedures (though it's usefulness to assess respiratory variation in vena cava is not conclusive). STARLING, a device based on bioreactance, works on phase shift or time delay while bioimpedance works on the amplitude of the thoracic impedance. Unlike bioimpedance, bioreactance is not affected by the size of the patient, thoracic fluids, or position of sensors.STARLING is equipped with four sensor pads. Each pad contains two sensors, the outer sensor is a transmitting electrode and the inner sensor is a receiving electrode. The STARLING monitor induces a 75-KHz AC current. It then measures the time delay/phase shift.STARLING system, a bioreactance-based dynamic assessment system for fluid responsiveness, predicts it accurately, precisely, and noninvasively. It reduces invasive risks and is independently validated against pulmonary artery catheter. It is not affected by vasopressors or shock and has wide range of application.