Aortic Flow Patterns Research Articles

Abnormal aortic flow conduction is associated with increased viscous energy loss in patients with repaired tetralogy of Fallot.

Aortopathy in tetralogy of Fallot (TOF) is characterized by increased aortic stiffness, dilation and reduced left ventricular (LV) function. Repair in infancy normalizes aortic dimensions in early childhood. Our prior work demonstrated that early TOF repair does not normalize aortic compliance and that abnormal ascending aortic flow patterns are prevalent. The objectives of this study were to: (i) determine whether proximal aortic flow-mediated viscous energy loss (EL') is elevated in patients with early TOF repair compared with healthy controls, and (ii) determine whether the degree of EL' is associated with LV function. Forty-one patients post TOF repair with normalized aortic size and 15 healthy controls underwent 4-dimenisonal-flow magnetic resonance imaging flow analysis and EL' assessment. Correlations between EL', aortic size, and LV function were assessed. The TOF group had increased peak systolic thoracic aorta EL' (3.8 vs 1.5 mW, P = 0.004) and increased averaged EL' throughout the cardiac cycle (1.2 vs 0.5 mW, P = 0.003). Peak and mean systolic EL' in the ascending aorta was increased 2-fold in the TOF group compared with control (peak: 2.0 vs 0.9 mW, P = 0.007). Peak EL' measured along the entire thoracic aortic length correlated with LV ejection fraction (R = -0.45, P = 0.009), indexed LV end-systolic volume (R = -0.40, P = 0.010), and right ventricular end-systolic volume (R = -0.37, P = 0.034). Patients with repaired TOF exhibit abnormal aortic flow associated with increased EL' in the thoracic aorta. The magnitude of EL' is associated with LV function and volumes. Increased aortic EL' in TOF is likely due to inherently abnormal LV outflow geometry and or right ventricular interaction. Reduced aortic flow efficiency in TOF increases cardiac work and may be an important factor in long-term cardiac performance.

Coronary Microcirculation in Aortic Stenosis.

Aortic stenosis is a heterogeneous disorder. Variations in the pathological and physiological responses to pressure overload are incompletely understood and generate a range of flow and pressure gradient patterns, which ultimately cause varying microvascular effects. The impact of cardiac-coronary coupling depends on these pressure and flow effects. In this article, we explore important concepts concerning cardiac physiology and the coronary microcirculation in aortic stenosis and their impact on myocardial remodeling, aortic valve flow patterns, and clinical progression.

Time-resolved 3-dimensional magnetic resonance phase contrast imaging (4D Flow MRI) reveals altered blood flow patterns in the ascending aorta of patients with valve-sparing aortic root replacement

ObjectiveThe aim of this study was to compare aortic flow patterns in patients after David valve-sparing aortic root replacement with physiologically shaped sinus prostheses or conventional tube grafts in healthy volunteers. MethodsTwelve patients with sinus prostheses (55 ± 15 years), 6 patients with tube grafts (58 ± 12 years), 12 age-matched, healthy volunteers (55 ± 6 years), and 6 young, healthy volunteers (25 ± 3 years) were examined with time-resolved 3-dimensional magnetic resonance phase contrast imaging (4D Flow MRI). Primary and secondary helical, as well as vortical flow patterns, were evaluated. Aortic arch anatomy as a flow influencing factor was determined. ResultsCompared with volunteers, both sinus prostheses and tube grafts developed more than 4 times as many secondary flow patterns in the ascending aorta (sinus prostheses n = 1.6 ± 0.8; tube grafts n = 1.3 ± 0.6; age-matched, healthy volunteers n = 0.3 ± 0.5; young, healthy volunteers n = 0; P ≤ .012) associated with a kinking of the prosthesis itself or at its distal anastomosis. As opposed to round aortic arches in volunteers (n = 16/18), cubic or gothic-shaped arches predominated in patients (n = 16/18, P < .001). In all but 3 volunteers, 2 counter-rotating helices were confirmed in the ascending aorta and were defined as a primary flow pattern. This primary flow pattern did not develop in patients who underwent valve-sparing aortic root replacement. ConclusionsIn patients after valve-sparing aortic root replacement, there was an increased number of secondary flow patterns in the ascending aorta. This seems to be related to surgically altered aortic geometry with kinking. Because flow alterations are known to affect wall shear stress, there seems to be an increased risk for vessel wall remodeling. Compared with previous 4D Flow MRI studies, primary flow patterns in the ascending aorta in healthy subjects were confirmed to be more complex. This underlines the importance of thorough examination of 4D Flow MRI data.

Comparison of Aortic Flow Patterns in Patients with and without Aortic Valve Disease: Hemodynamic Simulation Based on PC-MRI and CTA Data

Recent studies have revealed that aortic valve diseases are associated with the increased incidence of the aortopathy development. However, the influence of aortic valve diseases on aortic hemodynamics remains unclear. The purpose of this study was therefore to investigate the hemodynamic differenecs in patients with and without aortic valve disease through patient-specific simulations performed on two aorta models (BAV with severe stenosis vs. normal tricuspid aortic valve (TAV)). Realistic geometries and boundary conditions were obtained from computed tomography angiography (CTA) and phase-contrast magnetic resonance imaging (PC-MRI) measurements, respectively. In addition, 4D-MRI were performed to validate the the numerical methods used to simulate transient flow characteristics. Obtained results shown that the 3D streamlines in the patient with normal TAV were relatively symmetric and evenly distributed. For the patient with BAV, concentrated and high-speed inflow jets were found to impinge on the ascending aorta accompanied by strong vortices. These results indicate that the aortic valve phenotype plays a crucial role in featuring the disturbed flows primarily in ascending aorta, which may relate to the development of aortic diseases.

Acute Tachycardia Increases Aortic Distensibility, but Reduces Total Arterial Compliance Up to a Moderate Heart Rate.

Background: The differential effects of rapid cardiac pacing on small and large vessels have not been well-established. The objective of this study was to investigate the effect of pacing-induced acute tachycardia on hemodynamics and arterial stiffness.Methods: The pressure and flow waves in ascending aorta and femoral artery of six domestic swine were recorded simultaneously at baseline and heart rates (HR) of 135 and 155 beats per minutes (bpm) and analyzed by the models of Windkessel and Womersley types. Accordingly, the flow waves were simultaneously measured at carotid and femoral arteries to quantify aortic pulse wave velocity (PWV). The arterial distensibility was identified in small branches of coronary, carotid and femoral arteries with diameters of 300–600 μm by ex vivo experiments.Results: The rapid pacing in HR up to 135 bpm reduced the total arterial compliance, stroke volume, systemic pulse pressure, and central systolic pressure by 36 ± 17, 38 ± 26, 29 ± 16, and 23 ± 12%, respectively, despite no statistical difference of mean aortic pressure, cardiac output, peripheral resistance, and vascular flow patterns. The pacing also resulted in a decrease of distensibility of small muscular arteries, but an increase of aortic distensibility. Pacing from 135 to 155 bpm had negligible effects on systemic and local hemodynamics and arterial stiffness.Conclusions: There is an acute mismatch in the response of aorta and small arteries to pacing from basal HR to 135 bpm, which may have important pathological implications under chronic tachycardia conditions.

Transcatheter aortic valve replacement alters ascending aortic blood flow and wall shear stress patterns: A 4D flow MRI comparison with age-matched, elderly controls

BackgroundWith the implementation of transcatheter aortic valve replacement (TAVR) in lower-risk patients, evaluation of blood flow characteristics and the effect of TAVR on aortic dilatation becomes of considerable interest. We employed 4D flow MRI in the ascending aorta of patients after TAVR to assess wall shear stress (WSS) and compare blood flow patterns with surgical aortic valve replacement (SAVR) and age- and gender-matched controls.MethodsFourteen post-TAVR patients and ten age- and gender-matched controls underwent kt-PCA accelerated 4D flow MRI of the thoracic aorta at 3.0 Tesla. Velocity and wall shear stress was compared between the two groups. In addition, aortic flow eccentricity and displacement was assessed and compared between TAVR patients, controls and 14 SAVR patients recruited as part of an earlier study.ResultsCompared to controls, abnormally elevated WSS was present in 30±10% of the ascending aortic wall in TAVR patients. Increased WSS was present along the posterior mid-ascending aorta and the anterior distal-ascending aorta in all TAVR patients. TAVR results in eccentric and displaced flow in the mid- and distal-ascending aorta, whereas blood flow displacement in SAVR patients occurs only in the distal-ascending aorta.ConclusionThis study shows that TAVR results in increased blood flow velocity and WSS in the ascending aorta compared to age- and gender-matched elderly controls. This finding warrants longitudinal assessment of aortic dilatation after TAVR in the era of potential TAVR in lower-risk patients. Additionally, TAVR results in altered blood flow eccentricity and displacement in the mid- and distal-ascending aorta, whereas SAVR only results in altered blood flow eccentricity and displacement in the distal-ascending aorta.Key Points• TAVR results in increased blood flow velocity and WSS in the ascending aorta.• Longitudinal assessment of aortic dilatation after TAVR is warranted in the era of potential TAVR in lower-risk patients.• Both TAVR and SAVR result in altered blood flow patterns in the ascending aorta when compared to age-matched controls.

Quantitative Study of Abdominal Blood Flow Patterns in Patients with Aortic Dissection by 4-Dimensional Flow MRI

The purpose of this study is to evaluate the hemodynamic characteristics of the true lumen (TL) and the false lumen (FL) in 16 patients with aortic dissection (AD) using 4D flow magnetic resonance imaging (MRI) and thoracic and abdominal computed tomography (CT) angiography. The quantitative parameters that were measured in the TL and FL included velocity and flow. The mean area and regurgitant fraction of the TL were significantly lesser at all four levels (p < 0.05); the average through-plane velocity, peak velocity magnitude, average net flow, peak flow, and net forward volume in the TL were considerably higher (p < 0.05). The intimal entry’s size was negatively correlated with the blood flow velocity and flow rate in the TL (p < 0.05) and positively correlated with the average through-plane velocity, average net flow, and peak flow in the FL (p < 0.05); the blood flow indices in the TL were enhanced with an increase in the intimal entry numbers (p < 0.05) and the peak flow in the FL was lowered (p = 0.025); if FL thrombosis existed, the average through-plane velocity and peak velocity magnitude in the TL were substantially higher (p < 0.05). 4D flow MRI facilitates qualitative and quantitative analysis of the alterations in the abdominal aortic blood flow patterns.

4D flow characterization of aortic blood flow after valve sparing root reimplantation procedure

Valve-sparing aortic root replacement (VSRR) with reimplantation technique is an effective alternative for young patients with dilated roots and preserved cusps, which avoids the risks of lifelong anticoagulation or valve degeneration. New grafts with anatomically-shaped sinuses have been developed in order to preserve aortic root physiology, which could decrease complication rates and improve durability. However, controversy remains regarding the effect of recreation of the sinuses of Valsalva during VSRR on long-term outcomes. The novel 4D flow technique, exploiting its unique ability to combine anatomical evaluation of the root with fluid-dynamic assessment of aortic flow, enables integrated analysis of the close interaction between graft design, valvular morphology and three-dimensional (3D) flow characteristics. Early experimental studies have shown how graft shape affects the aortic root flow pattern, formation of vortexes and helicity of downstream flow; however, the clinical significance of these findings is yet to be clarified. Various and still unexplored knowledge can be obtained from the qualitative and quantitative analysis of these complex datasets, that could shed more light on which is the best among myriad surgical techniques and grafts adopted in VSRR. The extraordinary potential 4D flow imaging opens new boundless horizons in the perspective of an increasingly patient-tailored surgical planning.

Relationship Between Proximal Aorta Morphology and Progression Rate of Aortic Stenosis

The aim of this study was to examine the association between abnormal morphology of the proximal aorta and aortic stenosis (AS) progression rate. The main hypothesis was that morphologic changes of the proximal aorta, such as effacement of the sinotubular junction (STJ), result in increased biomechanical stresses and contribute to calcification and progression of AS. Between 2010 and 2012, 426 patients with mild to moderate AS were included in this study. Proximal aortic dimensions were measured at three different levels (i.e., sinus of Valsalva, STJ, and ascending aorta), and sinuses of Valsalva/STJ and ascending aorta/STJ ratios were used to determine degree of aortic deformity. AS progression rate was assessed by annualized increase in mean gradient (median follow-up time, 3.1years; interquartile range, 2.6-3.9years). The degree of aortic flow turbulence was examined in 18 matched patients with and without STJ effacement using cardiac magnetic resonance phase-contrast imaging. Patients' mean age was 71±13years, and 64% were men. Patients with low ratios had greater AS progression (P<.05). After comprehensive adjustment, sinuses of Valsalva/STJ (P=.025) and ascending aorta/STJ (P=.027) ratios were independently associated with greater AS progression rate. Compared with patients without STJ effacement, those with effacement of the STJ had higher degrees of aortic flow turbulence (24.4% vs 17.2%, P=.038). Effacement of the STJ is independently associated with greater AS progression, regardless of arterial hemodynamics, aortic valve phenotype, or baseline AS severity. Patients with abnormal proximal aortic geometry had disturbed aortic flow patterns. These findings suggest an interrelation between proximal aorta morphology and stenosis progression.

Aortic flow patterns and wall shear stress maps by 4D-flow cardiovascular magnetic resonance in the assessment of aortic dilatation in bicuspid aortic valve\xa0disease

BackgroundIn patients with bicuspid valve (BAV), ascending aorta (AAo) dilatation may be caused by altered flow patterns and wall shear stress (WSS). These differences may explain different aortic dilatation morphotypes. Using 4D-flow cardiovascular magnetic resonance (CMR), we aimed to analyze differences in flow patterns and regional axial and circumferential WSS maps between BAV phenotypes and their correlation with ascending aorta dilatation morphotype.MethodsOne hundred and one BAV patients (aortic diameter ≤ 45 mm, no severe valvular disease) and 20 healthy subjects were studied by 4D-flow CMR. Peak velocity, flow jet angle, flow displacement, in-plane rotational flow (IRF) and systolic flow reversal ratio (SFRR) were assessed at different levels of the AAo. Peak-systolic axial and circumferential regional WSS maps were also estimated. Unadjusted and multivariable adjusted linear regression analyses were used to identify independent correlates of aortic root or ascending dilatation. Age, sex, valve morphotype, body surface area, flow derived variables and WSS components were included in the multivariable models.ResultsThe AAo was non-dilated in 24 BAV patients and dilated in 77 (root morphotype in 11 and ascending in 66). BAV phenotype was right-left (RL-) in 78 patients and right-non-coronary (RN-) in 23. Both BAV phenotypes presented different outflow jet direction and velocity profiles that matched the location of maximum systolic axial WSS. RL-BAV velocity profiles and maximum axial WSS were homogeneously distributed right-anteriorly, however, RN-BAV showed higher variable profiles with a main proximal-posterior distribution shifting anteriorly at mid-distal AAo. Compared to controls, BAV patients presented similar WSS magnitude at proximal, mid and distal AAo (p = 0.764, 0.516 and 0.053, respectively) but lower axial and higher circumferential WSS components (p < 0.001 for both, at all aortic levels). Among BAV patients, RN-BAV presented higher IRF at all levels (p = 0.024 proximal, 0.046 mid and 0.002 distal AAo) and higher circumferential WSS at mid and distal AAo (p = 0.038 and 0.046, respectively) than RL-BAV. However, axial WSS was higher in RL-BAV compared to RN-BAV at proximal and mid AAo (p = 0.046, 0.019, respectively). Displacement and axial WSS were independently associated with the root-morphotype, and circumferential WSS and SFRR with the ascending-morphotype.ConclusionsDifferent BAV-phenotypes present different flow patterns with an anterior distribution in RL-BAV, whereas, RN-BAV patients present a predominant posterior outflow jet at the sinotubular junction that shifts to anterior or right anterior in mid and distal AAo. Thus, RL-BAV patients present a higher axial WSS at the aortic root while RN-BAV present a higher circumferential WSS in mid and distal AAo. These results may explain different AAo dilatation morphotypes in the BAV population.

Differential flow improvements after valve replacements in bicuspid aortic valve disease: a cardiovascular magnetic resonance assessment

BackgroundAbnormal aortic flow patterns in bicuspid aortic valve disease (BAV) may be partly responsible for the associated aortic dilation. Aortic valve replacement (AVR) may normalize flow patterns and potentially slow the concomitant aortic dilation. We therefore sought to examine differences in flow patterns post AVR.MethodsNinety participants underwent 4D flow cardiovascular magnetic resonance: 30 BAV patients with prior AVR (11 mechanical, 10 bioprosthetic, 9 Ross procedure), 30 BAV patients with a native aortic valve and 30 healthy subjects.ResultsThe majority of subjects with mechanical AVR or Ross showed normal flow pattern (73% and 67% respectively) with near normal rotational flow values (7.2 ± 3.9 and 10.6 ± 10.5 mm2/ms respectively vs 3.8 ± 3.1 mm2/s for healthy subjects; both p > 0.05); and reduced in-plane wall shear stress (0.19 ± 0.13 N/m2 for mechanical AVR vs. 0.40 ± 0.28 N/m2 for native BAV, p < 0.05). In contrast, all subjects with a bioprosthetic AVR had abnormal flow patterns (mainly marked right-handed helical flow), with comparable rotational flow values to native BAV (20.7 ± 8.8 mm2/ms and 26.6 ± 16.6 mm2/ms respectively, p > 0.05), and a similar pattern for wall shear stress. Data before and after AVR (n = 16) supported these findings: mechanical AVR showed a significant reduction in rotational flow (30.4 ± 16.3 → 7.3 ± 4.1 mm2/ms; p < 0.05) and in-plane wall shear stress (0.47 ± 0.20 → 0.20 ± 0.13 N/m2; p < 0.05), whereas these parameters remained similar in the bioprosthetic AVR group.ConclusionsAbnormal flow patterns in BAV disease tend to normalize after mechanical AVR or Ross procedure, in contrast to the remnant abnormal flow pattern after bioprosthetic AVR. This may in part explain different aortic growth rates post AVR in BAV observed in the literature, but requires confirmation in a prospective study.

Abnormal Haemodynamic Flow Patterns in Bicuspid Pulmonary Valve Disease.

Abnormal flow patterns in the aortas of those with bicuspid aortic valves (BAVs) are increasingly recognized as important in the pathogenesis of aortic dilatation but pulmonary flow patterns in bicuspid pulmonary valves have not been studied. Bicuspid pulmonary valve disease is rare and a small numbers of case reports describe concomitant pulmonary artery dilation similar to the dilation of the ascending aorta, which is often seen in BAVs disease. We examined three cases of bicuspid pulmonary valve disease, 10 healthy volunteers and 10 patients with BAV disease but a tricuspid pulmonary valve. All participants underwent anatomical and functional imaging of the pulmonary valve, pulmonary artery, and right ventricle as well as advanced time-resolved 3-dimensional cardiac magnetic resonance imaging (4D flow) to assess the flow pattern in the pulmonary artery. All patients with a bicuspid pulmonary valve had pulmonary artery dilation and showed distinct helical flow abnormalities with increased rotational flow and increased flow displacement compared to a mild left-handed flow pattern in the healthy volunteers. Additionally, there was marked asymmetry seen in the systolic wall shear stress (WSS) pattern, with the highest values in the anterior wall of the pulmonary artery. In comparison, patients with a BAV but a tricuspid pulmonary valve had normal flow patterns in the pulmonary artery. These haemodynamic findings are similar to recent studies in bicuspid aortic disease, and suggest the importance of flow patterns in the pathophysiology of vessel dilation in both aortic and pulmonary bicuspid valve disease.

The study on hemodynamic effect of series type LVAD on aortic blood flow pattern: a primary numerical study.

BackgroundLeft ventricular assist device (LVAD) has become an alternative treatment for end-stage heart failure patients. Series type of LVAD, as a novel LVAD, has attracted more and more attention. The hemodynamic effects of series type LVAD on aortic blood pattern are considered as its important characteristics; however, the precise mechanism of it is still unclear.MethodsTo clarify the hemodynamic effects of series type LVAD on aortic blood flow pattern, a comparative study on the aortic blood flow pattern and hemodynamic states were carried out numerically for two cases, including series type LVAD support and normal condition. The steady-state computational fluid dynamic (CFD) approach was employed. The blood flow streamline, blood velocity vector and distribution of wall shear stress (WSS) were calculated to evaluate the differences of hemodynamic effects between both conditions.ResultsThe results demonstrated that the aortic flow pattern under series type LVAD showed significant different from that of normal condition. The strength of aortic swirling flow was significantly enhanced by the series type LVAD support. Meanwhile, the rotating direction of swirling flow under LVAD support was also dominated by the rotating direction of series type LVAD. Moreover, the blood velocity and WSS under LVAD support were also significantly enhanced, compared with that under normal condition.ConclusionThe hemodynamic states, including the aortic swirling flow characteristic, was significantly dominated by LVAD support. Present investigation could provide not only a useful information on the vascular complications caused by LVAD support, but also provide a useful guide for optimal the structure of the series type LVAD.

Altered aortic 3D hemodynamics and geometry in pediatric Marfan syndrome patients

BackgroundBlood flow dynamics make it possible to better understand the development of aortopathy and cardiovascular events in patients with Marfan syndrome (MFS). Aortic 3D blood flow characteristics were investigated in relation to aortic geometry in children and adolescents with MFS.MethodsTwenty-five MFS patients (age 15.6 ± 4.0 years; 11 females) and 21 healthy controls (age 16.0 ± 2.6 years; 12 females) underwent magnetic resonance angiography and 4D flow CMR for assessment of thoracic aortic size and 3D blood flow velocities. Data analysis included calculation of aortic diameter and BSA-indexed aortic dimensions (Z-score) along the thoracic aorta, 3D mean systolic wall shear stress (WSSmean) in ten aortic segments and assessment of aortic blood flow patterns.ResultsAortic root (root), ascending (AAo) and descending (DAo) aortic size was significantly larger in MFS patients than healthy controls (Root Z-score: 3.56 ± 1.45 vs 0.49 ± 0.78, p < 0.001; AAo Z-score 0.21 ± 0.95 vs −0.54 ± 0.64, p = 0.004; proximal DAo Z-score 2.02 ± 1.60 vs 0.56 ± 0.66, p < 0.001). A regional variation in prevalence and severity of flow patterns (vortex and helix flow patterns) was observed, with the aortic root and the proximal DAo (pDAo) being more frequently affected in MFS. MFS patients had significantly reduced WSSmean in the proximal AAo (pAAo) outer segment (0.65 ± 0.12 vs. 0.73 ± 0.14 Pa, p = 0.029) and pDAo inner segment (0.74 ± 0.17 vs. 0.87 ± 0.21 Pa, p = 0.021), as well as higher WSSmean in the inner segment of the distal AAo (0.94 ± 0.14 vs. 0.84 ± 0.15 Pa, p = 0.036) compared to healthy subjects. An inverse relationship existed between pDAo WSSmean and both pDAo diameter (R = −0.53, p < 0.001) and % diameter change along the pDAo segment (R = −0.64, p < 0.001).ConclusionsMFS children and young adults have altered aortic flow patterns and differences in aortic WSS that were most pronounced in the pAAo and pDAo, segments where aortic dissection or rupture often originate. The presence of vortex flow patterns and abnormal WSS correlated with regional size of the pDAo and are potentially valuable additional markers of disease severity.

Critical Care Ultrasound

Critical Care Ultrasound is an electronic and print textbook that presents the use of ultrasound in intensive care. Although thorough enough for an in-depth understanding of critical care ultrasound, the concise text and excellent visuals allow this book to be used as a quick reference as well. The authors write the book with a concept they call “The Holistic Approach” to an ultrasound examination. This defines the critical care ultrasound as the part of a patient examination, which visualizes anatomic structures and function “in their live, interconnected state.” Therefore, rather than merely describe a specific ultrasound modality, the authors write each chapter within the context of the physiology, pathophysiology, and anatomy. Section I outlines the fundamental concepts of ultrasound, including a review of physics, imaging modes, image optimization, and common artifacts encountered during an examination. The section closes with a comprehensive visual review of ultrasound anatomy and pathology. Systems reviewed include head and neck, chest, abdominal, and musculoskeletal. Section II details the use of ultrasound in neurocritical care. The section opens with a chapter on transcranial Doppler. The authors describe its multiple applications, including vasospasm monitoring after aneurysmal subarachnoid hemorrhage, ischemic stroke evaluation, diagnosis of cerebral circulatory arrest, and assessment of autoregulation. Included in this section is a description of optic nerve sheath diameter as a surrogate for intracranial pressure. The text progresses to Section III: Vascular Ultrasound, beginning with an overview of arterial and venous system anatomy and pathophysiology. The deep venous thrombosis chapter describes both the basic and advanced ultrasound diagnostic techniques and strategies for a successful examination. The central venous and arterial access chapters go beyond basic ultrasound-guided technique. The text details advanced knowledge of catheterization including ultrasound-guided subclavian access, evaluation of traumatic hematoma after line placement, and criteria for choosing the appropriate vein for cannulation. The book transitions to the general chest ultrasound and echocardiography sections. The chest section describes the ultrasound as an adjuvant in diagnosing common lung pathologies including pneumothorax, pleural effusion, and pneumonia. The section includes the use of ultrasound in trauma, acute dyspnea, acute respiratory distress syndrome, and the difficult to wean mechanically ventilated patient. The echocardiography chapters describe the use of echocardiography in the evaluation of circulatory failure, septic shock, pulmonary embolism, and cardiac arrest. The hemodynamic monitoring section first presents general concepts, such as static-based parameters, dynamic arterial waveform analysis, and passive leg raising. The authors tie the use of ultrasound to these basic concepts. They describe measuring fluid responsiveness by both static and dynamic ultrasound measurements. These include measurement of inferior vena cava diameter, mitral valve inflow patterns, and respiratory variations in both aortic and inferior vena cava flow patterns. A highlight of the section is a well-organized flow chart describing the use of ultrasound as a guide in the evaluation of circulatory failure. The book transitions to abdominal and emergency ultrasound. This includes chapters on the extended FAST examination and ultrasound evaluation of abdominal compartment syndrome. There is an excellent online video, which demonstrates a FAST examination being performed on a sample patient. The final clinical section discusses soft tissue and miscellaneous uses of ultrasound. These chapters include details on evaluating musculoskeletal injury and masses. In addition, there is a chapter on ultrasound-guided percutaneous tracheostomy, which highlights the use of ultrasound in determining stoma site selection and tracheostomy size. The electronic version of the textbook is available in 3 formats: an online version through Expert Consult, as a PDF, and as an ePub book. The Expert Consult version of the book is simple and navigable. There are videos and pictures, which are organized as both a list and embedded in the chapters. This organization allows the reader to either quickly select a video for quick review or view the content within the chapter for more detail. In addition, each online chapter includes a detailed set of references if further information on a topic is desired. Unfortunately, the PDF version of the book does not provide the same seamless integration. The links provided in the PDF documents are irregular and do not always link to the referenced material. In conclusion, Critical Care Ultrasound is an excellent handbook for the intensivist or anesthesiologist. The greatest strength of the book, however, is its greatest weakness. At times, because the chapters are so brief, there are details that are omitted. Furthermore, the text does not transition well to the PDF format. Regardless of the few weaknesses, Critical Care Ultrasound is an excellent addition to the library of any intensivist or anesthesiologist. Anthony F. Dempsey, MDJudson Mehl, DODepartment of AnesthesiologyUniversity of Kentucky College of MedicineLexington, Kentucky[email protected]

Aortic flow patterns before and after personalised external aortic root support implantation in Marfan patients

Implantation of a personalised external aortic root support (PEARS) in the Marfan aorta is a new procedure that has emerged recently, but its haemodynamic implication has not been investigated. The objective of this study was to compare the flow characteristics and hemodynamic indices in the aorta before and after insertion of PEARS, using combined cardiovascular magnetic resonance imaging (CMR) and computational fluid dynamics (CFD). Pre- and post-PEARS MR images were acquired from 3 patients and used to build patient-specific models and upstream flow conditions, which were incorporated into the CFD simulations. The results revealed that while the qualitative patterns of the haemodynamics were similar before and after PEARS implantation, the post-PEARS aortas had slightly less disturbed flow at the sinuses, as a result of reduced diameters in the post-PEARS aortic roots. Quantitative differences were observed between the pre- and post-PEARS aortas, in that the mean values of helicity flow index (HFI) varied by −10%, 35% and 20% in post-PEARS aortas of Patients 1, 2 and 3, respectively, but all values were within the range reported for normal aortas. Comparisons with MR measured velocities in the descending aorta of Patient 2 demonstrated that the computational models were able to reproduce the important flow features observed in vivo.

Differences in aortic vortex flow pattern between normal and patients with stroke: qualitative and quantitative assessment using transesophageal contrast echocardiography.

The flow in the aorta forms a vortex, which is a critical determinant of the flow dynamics in the aorta. Arteriosclerosis can alter the blood flow pattern of the aorta and cause characteristic alterations of the vortex. However, this change in aortic vortex has not yet been studied. This study aimed to characterize aortic vortex flow pattern using transesophageal contrast echocardiography in normal and stroke patients. A total of 85 patients who diagnosed with ischemic stroke and 16 normal controls were recruited for this study. The 16 normal control subjects were designated as the control group, and the 85 ischemic stroke patients were designated as the stroke group. All subjects underwent contrast transesophageal echocardiography (TEE), and particle image velocimetry was used to assess aortic vortex flow. Qualitative and quantitative analyses of vortex flow morphology, location, phasic variation, and pulsatility were undertaken and compared between the groups. In the control group, multiple irregularly-shaped vortices were observed in a peripheral location in the descending thoracic aorta. In contrast, the stroke group had a single, round, merged, and more centrally located aortic vortex flow. In the quantitative analysis of vortex, vortex depth, which represents the location of the major vortex in the aorta, was significantly higher in the control group than in the stroke group (0.599±0.159 vs. 0.522±0.101, respectively, P=0.013). Vortex relative strength, which is the pulsatility parameter of the vortex itself, was significantly higher in the stroke group than in the control group (0.367±0.148 vs. 0.304±0.087, respectively, P=0.025). It was feasible to visualize and quantify the characteristic morphology and pulsatility of the aortic vortex flow using contrast TEE, and aortic vortex pattern significantly differed between normal and stroke patients.

Abstract 14155: Haemodynamic Changes After Aortic Valve Replacement in Bicuspid Aortic Valve Disease Differ With Prosthesis Type

Introduction: Bicuspid aortic valve disease (BAV) is associated with dilatation of the proximal aorta and abnormal flow patterns, particularly increased helical flow and changes in the aortic wall shear stress. We assess the effect of different types of aortic valve replacement (AVR) on aortic flow patterns. Hypothesis: Aortic valve replacement in bicuspid aortic valve disease normalises ascending aortic flow patterns. Methods: We prospectively enrolled 87 participants: 27 BAV patients with prior AVR (10 mechanical, 8 bioprosthetic, 9 Ross procedure), 30 BAV patients with a native aortic valve and 30 healthy volunteers. All underwent 4D flow cardiovascular magnetic resonance. Results: The majority of patients with mechanical AVR or Ross showed a normalised flow pattern (70% and 67% respectively) with near normal rotational flow values (7.4±1.2 and 10.6±3.5 mm 2 /s respectively; normal range -5 to +11 mm 2 /s). They also showed reduced in-plane wall shear stress compared to native BAV (0.13±0.04 N/m 2 for mechanical AVR vs. 0.37±0.05 N/m 2 for native BAV, p&lt;0.05). In contrast, all subjects with bioprosthetic AVR showed abnormal flow patterns (mainly marked right-handed helical flow), with similar rotational flow values to native BAV (20.7±3.3 mm 2 /s and 25.9±3.1 mm 2 /s respectively, p&gt;0.05) and similar wall shear stress pattern. Data before and after AVR (n=16) supported these findings: mechanical AVR showed a significant reduction in rotational flow (29.3±5.3 to 7.9±1.2 mm 2 /s, p&lt;0.05) and in-plane wall shear stress (0.45±0.07 to 0.20±0.04 N/m 2 , p&lt;0.05), whereas these remained unchanged in the bioprosthetic AVR group. Conclusions: Abnormal flow patterns in BAV are significantly reduced after mechanical AVR or Ross procedure, but remain similar after bioprosthetic AVR. This is the first insight indicating that the type of valve replacement may influence post-operative aortic flow patterns, and could have important implications for future aortic growth.

Abstract 18044: Predictors of Bicuspid Aortic Valve Associated Aortopathy in Pediatric Patients

Bicuspid aortic valve (BAV) is the most common congenital heart disease and is commonly associated with significant ascending aorta dilation. Valve morphology and function have been proposed as potential risk factors; however evaluating their role is difficult, as BAV morphology and valve function are inherently related. Our objective was to determine whether BAV morphology and function are independently associated with ascending aorta dilation in pediatric patients. We performed a multicenter, retrospective, cross-sectional study of pediatric patients with BAV that were followed after 2003. The last patient echocardiogram prior to valve intervention was analyzed for BAV morphology, presence and severity of aortic stenosis (AS) and insufficiency (AI), and aortic root and ascending aorta dimensions. The relationship of potential risk factors to ascending aorta dimensions at different ages was determined using linear regression. Data was obtained from 1725 patients (68% male). The most common BAV morphology was right-left (R-L) coronary cusp fusion (65%) followed by right-non (R-N) fusion (34%) and left-non fusion (1%). Fourteen percent of patients had at least moderate AS and 7% had at least moderate AI. R-L fusion was associated with coarctation (55%), while R-N fusion was less associated with coarctation (19%) and more associated with valve dysfunction (24% and 12% with at least moderate AS and AI). Twenty-seven percent of patients had significant ascending aorta dilation (Z score &gt;3). AS and AI were associated with more significant ascending aorta dilation and a faster Z-score progression over time. R-N fusion was associated with ascending aorta dilation; however, when valves with AS and AI were excluded, there were no differences related to morphology. In patients with no AS or AI, 15% had significant ascending aorta dilation. In this large pediatric cohort of patients with BAV, we show that valve morphology is not independently associated with ascending aorta dilation. Valve dysfunction (both AS and AI) is associated with more significant dilation; however, even in valves with normal function, there is significant ascending aorta dilation. We suggest that there is an inherent arterial abnormality, possibly modified by aortic flow patterns.

Comparison of Hemodynamics After Aortic Root Replacement Using Valve-Sparing or Bioprosthetic Valved Conduit

The purpose of this study is to compare aortic hemodynamics and blood flow patterns using in-vivo four-dimensional (4D) flow magnetic resonance imaging (MRI) in patients after valve-sparing aortic root replacement (VSARR) and aortic root replacement with bioprosthetic valves (BIO-ARR). In-vivo 4D flow MRI was performed in 11 patients after VSARR (47 ± 18 years, 6 bicuspid aortic valves, 5 trileaflet aortic valves), 16 patients after BIO-ARR (52 ± 14 years), and 10 healthy controls (47 ± 16 years). Analysis included three-dimensional blood flow visualization and grading of helix flow in the ascending aorta (AAo) and arch. Peak systolic velocity was quantified in 9 analysis planes in the AAo, aortic arch, and descending aorta. Flow profile uniformity was evaluated in the aortic root and ascending aorta. Peak systolic velocity (2.0 to 2.5m/second) in the aortic root and AAo in both VSARR and BIO-ARR were elevated compared with controls (1.1 to 1.3m/second, p < 0.005). Flow asymmetry in BIO-ARR was increased compared with VSARR, evidenced by more AAo outflow jets (9 of 16 BIO-ARR, 0 of 11 in VSARR). The BIO-ARR exhibited significantly (p < 0.001) increased helix flow in the AAo as a measure of increased flow derangement. Finally, peak systolic velocities were elevated at the aortic root for BIO-ARR (2.5 vs 2.0m/second, p < 0.05) but lower in the distal AAo when compared with VSARR. The VSARR results in improved hemodynamic outcomes when compared with BIO-ARR, as indicated by reduced peak velocities in the aortic root and less helix flow in the AAo by 4D flow MRI. Longitudinal research assessing the clinical impact of these differences in hemodynamic outcomes is warranted.