Systolic Stress Research Articles

MACRO- AND MICROCIRCULATORY ABNORMALITIES OF VASCULAR WALL IN HYPERTENSIVE PATIENTS

Objective: To study arterial wall elasticity and stiffness in hypertensive's patients with moderate and high cardiovascular risk not receiving antihypertensive treatment. Design and method: The study included 41 hypertensive's patients (16 male and 27 female) with mean age of 61.1 ± 10.7 years, systolic, diastolic blood pressure (162.7 ± 20.8 mm Hg, 98.6 ± 11.2 mm Hg), hypertension duration 9.3 ± 7.2 years. Obesity was found in 32% of participants, 21% of patients were smokers. Carotid Doppler ultrasound study with intima-media thickness (IMT) measurement (using Aloka SSD 2000 ultrasound system) and photoplethysmography with augmentation index (AI), stiffness index (SI), delay in time between early and late systolic waves (dTPP), vascular age (VA) and stress index (SI) scores assessment (using Angioscan Professional system, Russia, 2015) were performed on all patients. Statistical analysis was done using Statistica 10.0 software. Results: There were 3 groups of patients: I (N = 14) with normal IMT (<0.9 mm) and no carotid atherosclerotic plaque present, II (N = 13) with increased IMT (>0.9 mm) and no plaques, and III (N = 14) with carotid atherosclerotic plaques (average number 2.0 ± 1.6 with the mean % narrowing of 32.4 ± 12.6). There were no differences in age, hypertension grade, obesity and smoking prevalence between the groups. With the increase in carotid atherosclerosis, a significant rise in AI was seen (−1.3 ± 19.7% in group I, 10.5 ± 12.7% in group II and 18.6 ± 13.8% in group III; p < 0.05), whereas dTPP was significantly lower in group III than in groups II and I (90.5 ± 30.7 vs 89.2 ± 17.2 ms vs 96.5 ± 29.3 ms, respectively; p < 0,05 between groups I and III). Significant difference in SI was found only between groups I and II (7.4 ± 1.07 m/s vs 8.2 ± 0.88 m/s, respectively; p < 0.05), while this parameter was 7.6 ± 1.09 m/s in group III. Patients from groups I, II, and III demonstrated a significant elevation of VA (44.7 ± 14.9 vs 58.3 ± 7.4 vs 63.5 ± 12.9 years, respectively; p < 0.05) and SI (3.1 ± 1.2 vs 3.5 ± 1.04 vs 3.9 ± 0.95, respectively; p < 0.05). A correlation between VA and carotid diameter (R = –0.7; p < 0.05), AI and the number of atherosclerotic plaques (R = 0.73; p < 0.05) was revealed in hypertensive's. Conclusions: Carotid atherosclerosis in hypertensive's is associated with microcirculatory abnormalities and increased vascular age and stress index scores.

Scan\u2013rescan reproducibility of segmental aortic wall shear stress as assessed by phase-specific segmentation with 4D flow MRI in healthy volunteers

ObjectiveThe aim was to investigate scan–rescan reproducibility and observer variability of segmental aortic 3D systolic wall shear stress (WSS) by phase-specific segmentation with 4D flow MRI in healthy volunteers.Materials and methodsTen healthy volunteers (age 26.5 ± 2.6 years) underwent aortic 4D flow MRI twice. Maximum 3D systolic WSS (WSSmax) and mean 3D systolic WSS (WSSmean) for five thoracic aortic segments over five systolic cardiac phases by phase-specific segmentations were calculated. Scan–rescan analysis and observer reproducibility analysis were performed.ResultsScan–rescan data showed overall good reproducibility for WSSmean (coefficient of variation, COV 10–15%) with moderate-to-strong intraclass correlation coefficient (ICC 0.63–0.89). The variability in WSSmax was high (COV 16–31%) with moderate-to-good ICC (0.55–0.79) for different aortic segments. Intra- and interobserver reproducibility was good-to-excellent for regional aortic WSSmax (ICC ≥ 0.78; COV ≤ 17%) and strong-to-excellent for WSSmean (ICC ≥ 0.86; COV ≤ 11%). In general, ascending aortic segments showed more WSSmax/WSSmean variability compared to aortic arch or descending aortic segments for scan–rescan, intraobserver and interobserver comparison.ConclusionsScan–rescan reproducibility was good for WSSmean and moderate for WSSmax for all thoracic aortic segments over multiple systolic phases in healthy volunteers. Intra/interobserver reproducibility for segmental WSS assessment was good-to-excellent. Variability of WSSmax is higher and should be taken into account in case of individual follow-up or in comparative rest–stress studies to avoid misinterpretation.

Association of variant arch anatomy with type B aortic dissection and hemodynamic mechanisms

ObjectiveCongenital aortic arch variations are more common in patients with thoracic aortic disease for reasons unknown. Additionally, little is understood about their relation to type B aortic dissections (TBAD) specifically. We investigated the prevalence of variant aortic arch anatomy in patients with TBAD compared with controls. To understand the implications of how variant aortic arch anatomy may contribute to degenerative aortic disease, we compared flow hemodynamics of three variations of aortic arches using four-dimensional flow magnetic resonance imaging (4D flow MRI). MethodsArch anatomy on computed tomography imaging was reviewed and compared between patients with TBAD and age/sex-matched controls free of aortic pathology. Arch variants were defined as follows: common origin of innominate and left common carotid artery (bovine arch), aberrant right subclavian artery, and right-sided aortic arch. Demographics, TBAD characteristics, and follow-up data were abstracted. Patients with TBAD with variant and conventional aortic arches were compared. Additionally, three matched healthy controls with conventional, bovine, and aberrant right subclavian artery arches underwent 4D flow MRI evaluation to assess if there were differences in flow patterns by arch type. Indices of regional hemodynamic wall sheer stress were compared. ResultsComputed tomography scans of 185 patients with TBAD (mean age, 58.1 ± 12.4 years; 72.4% males; 71.4% Caucasian) and 367 controls (mean age, 62.5 ± 13.4 years; 67% males; 77.9% Caucasian) were reviewed. Variant arch anatomy was more prevalent in patients with TBAD (40.5% vs 24.5%; P < .001). In patients with TBAD, there were no differences in the mean age of presentation and descending thoracic aorta diameter among those with variant or conventional arch anatomy. Patients with TBAD with variant arch anatomy had a higher percentage of dissection related thoracic aortic repairs (54.7% vs 33.6%; P = .004) with repairs occurring predominantly in the acute phase. 4D flow MRI demonstrated a higher systolic wall shear stress along the inner curve of the bovine arch compared with the conventional aberrant right subclavian artery arches. ConclusionsVariant aortic arch anatomy is significantly more prevalent in patients with TBAD. patients with TBAD with variant arch anatomy had a higher percentage of dissection-related aortic repair. Preliminary 4D flow MRI data show differences in hemodynamic flow patterns between variant and conventional arches. Studies of long-term outcomes based on arch anatomy may offer additional insight to TBAD genesis and possibly influence management decisions.

Clinical validation and assessment of aortic hemodynamics using computational fluid dynamics simulations from computed tomography angiography

BackgroundHemodynamic information including peak systolic pressure (PSP) and peak systolic velocity (PSV) carry an important role in evaluation and diagnosis of congenital heart disease (CHD). Since MDCTA cannot evaluate hemodynamic information directly, the aim of this study is to provide a noninvasive method based on a computational fluid dynamics (CFD) model, derived from multi-detector computed tomography angiography (MDCTA) raw data, to analyze the aortic hemodynamics in infants with CHD, and validate these results against echocardiography and cardiac catheter measurements.MethodsThis study included 25 patients (17 males, and 8 females; a median age of 2 years, range: 4 months–4 years) with CHD. All patients underwent both transthoracic echocardiography (TTE) and MDCTA within 2 weeks prior to cardiac catheterization. CFD models were created from MDCTA raw data. Boundary conditions were confirmed by lumped parameter model and transthoracic echocardiography (TTE). Peak systolic velocity derived from CFD models (PSVCFD) was compared to TTE measurements (PSVTTE), while the peak systolic pressure derived from CFD (PSPCFD) was compared to catheterization (PSPCC). Regions with low and high peak systolic wall shear stress (PSWSS) were also evaluated.ResultsPSVCFD and PSPCFD showed good agreements between PSVTTE (r = 0.968, p < 0.001; mean bias = − 7.68 cm/s) and PSPCC (r = 0.918, p < 0.001; mean bias = 1.405 mmHg). Regions with low and high PSWSS) can also be visualized. Skewing of velocity or helical blood flow was also observed at aortic arch in patients.ConclusionsOur result demonstrated that CFD scheme based on MDCTA raw data is an accurate and convenient method in obtaining the velocity and pressure from aorta and displaying the distribution of PSWSS and flow pattern of aorta. The preliminary results from our study demonstrate the capability in combining clinical imaging data and novel CFD tools in infants with CHD and provide a noninvasive approach for diagnose of CHD such as coarctation of aorta in future.

Efficient estimation of personalized biventricular mechanical function employing gradient-based optimization.

Individually personalized computational models of heart mechanics can be used to estimate important physiological and clinically‐relevant quantities that are difficult, if not impossible, to directly measure in the beating heart. Here, we present a novel and efficient framework for creating patient‐specific biventricular models using a gradient‐based data assimilation method for evaluating regional myocardial contractility and estimating myofiber stress. These simulations can be performed on a regular laptop in less than 2 h and produce excellent fit between measured and simulated volume and strain data through the entire cardiac cycle. By applying the framework using data obtained from 3 healthy human biventricles, we extracted clinically important quantities as well as explored the role of fiber angles on heart function. Our results show that steep fiber angles at the endocardium and epicardium are required to produce simulated motion compatible with measured strain and volume data. We also find that the contraction and subsequent systolic stresses in the right ventricle are significantly lower than that in the left ventricle. Variability of the estimated quantities with respect to both patient data and modeling choices are also found to be low. Because of its high efficiency, this framework may be applicable to modeling of patient specific cardiac mechanics for diagnostic purposes.

Determining Significant Morphological and Hemodynamic Parameters to Assess the Rupture Risk of Cerebral Aneurysms

Hemodynamics and morphology are recognized as major factors in the rupture risk of cerebral aneurysms, and exploration of their relationship is necessary to establish a method that can be employed by clinicians to assess the likelihood of rupture. In this work, morphological analysis and computational fluid dynamics were carried out to examine a database of 58 lateral cerebral aneurysms (26 ruptured and 32 unruptured) distributed among 49 patients. Eight morphological and six hemodynamic parameters were calculated and evaluated for statistical significance. It was observed that size ratio (SR), systolic wall shear stress (SWSS), diastolic wall shear stress (DWSS) and relative residence time (RRT) were statistically significant. The SR, DWSS, SWSS, and RRT were employed in multivariate logistic regression, obtaining a combined morphological–hemodynamic model, a pure morphological model, and a pure hemodynamic model to evaluate the odds ratio for rupture risk. The combined model had the highest efficiency, but no distinctive difference existed in the predictive capacity of the three models.

Left-Ventricular Energetics in Pulmonary Arterial Hypertension-Induced Right-Ventricular Hypertrophic Failure.

Pulmonary arterial hypertension (PAH) alters the geometries of both ventricles of the heart. While the right ventricle (RV) hypertrophies, the left ventricle (LV) atrophies. Multiple lines of clinical and experimental evidence lead us to hypothesize that the impaired stroke volume and systolic pressure of the LV are a direct consequence of the effect of pressure overload in the RV, and that atrophy in the LV plays only a minor role. In this study, we tested this hypothesis by examining the mechanoenergetic response of the atrophied LV to RV hypertrophy in rats treated with monocrotaline. Experiments were performed across multiple-scales: the whole-heart in vivo and ex vivo, and its trabeculae in vitro. Under the in vivo state where the RV was pressure-overloaded, we measured reduced systemic blood pressure and LV ventricular pressure. In contrast, under both ex vivo and in vitro conditions, where the effect of RV pressure overload was circumvented, we found that LV was capable of developing normal systolic pressure and stress. Nevertheless, LV atrophy played a minor role in that LV stroke volume remained lower, thereby contributing to lower LV mechanical work output. Concomitantly lower oxygen consumption and change of enthalpy were observed, and hence LV energy efficiency was unchanged. Our internally consistent findings between working-heart and trabecula experiments explain the rapid improvement of LV systolic function observed in patients with chronic pulmonary hypertension following surgical relief of RV pressure overload.

Prognostic significance of blood pressure response during vasodilator stress Rb-82 positron emission tomography myocardial perfusion imaging

BackgroundA drop in blood pressure (BP) or blunted BP response is an established high-risk marker during exercise myocardial perfusion imaging (MPI); however, data are sparse regarding the prognostic value of BP response in patients undergoing vasodilator stress rubidium-82 (Rb-82) Positron Emission Tomography (PET) MPI. Methods and ResultsFrom the PET Prognosis Multicenter Registry, a cohort of 3413 patients underwent vasodilator stress Rb-82 PET MPI with dipyridamole or adenosine. We used multivariable Cox proportional hazard regression to analyze the association with mortality of four BP variables: stress minus rest systolic BP (∆SBP), stress minus rest diastolic BP (∆DBP), resting systolic BP (rSBP), and resting diastolic BP (rDBP). Covariates that had univariate P values <.10 were entered into the multivariable model. After median 1.7 years follow-up, 270 patients died. In univariate analyses, ∆SBP (P = .082), rSBP (P = .008), and rDBP (P < .001) were of potential prognostic value (P < .10), but ∆DBP was not (P = .96). After adjustment for other clinical and MPI variables, ∆SBP no longer independently predicted mortality (P = .082); only lower rSBP (P = .026) and lower rDBP (P = .045) remained independently prognostic. ConclusionsIn patients undergoing vasodilator stress MPI, only lower resting BP is an independent predictor of mortality along with other clinical and MPI variables; BP response does not appear to add to risk stratification in these patients.

Echocardiographic and electrocardiographic parameters during the normal postpartum period in toy breeds of dogs

The aim of this study was to evaluate echocardiographic and electrocardiographic parameters during the normal canine postpartum period. Twenty clinically healthy pregnant bitches of toy breeds (11 Miniature poodles, five Yorkshire terriers, two Maltese terriers and two Bichons Frises) were evaluated on days −3, 3, 10, 17, 24, 38, 52 and 80 relative to parturition (day 0). During the first postpartum week, the width of the interventricular septum in systole, the shortening fraction and the left atrium size decreased, while the left ventricle internal diameter in systole and end systolic stress increased. There were progressive decreases in the velocity of circumferential fibre shortening, stroke volume, cardiac output, and mitral E and A wave values. Systolic blood pressure increased markedly during the first postpartum week to gradually increase thereafter. Heart rate and corrected QT interval progressively decreased, while P wave amplitude increased. QRS complex amplitude decreased in the second week after parturition and then increased during the following weeks. In conclusion, there were changes in systolic function and some structural adaptive changes in the bitch during the first 80days postpartum. In addition, maternal heart rate and corrected QT interval decreased, while P wave and QRS amplitudes increased.

Left ventricular systolic function in sickle cell anaemia: an echocardiographic evaluation in adult Nigerian patients.

Reliable diagnostic measures for the evaluation of left ventricular systolic performance in the setting of altered myocardial loading characteristics in sickle cell anaemia remains unresolved. The study was designed to assess left ventricular systolic function in adult sickle cell patients using non-invasive endsystolic stress - end-systolic volume index ratio. A descriptive cross sectional comparative study was done using 52 patients recruited at the adult sickle cell anaemia clinic of the University of Nigeria Teaching Hospital Enugu. An equal number of age and sex-matched healthy volunteers served as controls. All the participants had haematocrit estimation, haemoglobin electrophoresis, as well as echocardiographic evaluation. The mean age of the patients and controls were 23.93 ± 5.28 (range 18-42) and 24.17 ± 4.39 (range 19 -42) years respectively, (t = 0.262; p= .794). No significant difference was seen in estimate of fractional shortening, and ejection fraction. The cardiac out-put, cardiac index and velocity of circumferential shortening were all significantly increased in the cases compared with the controls. The end systolic stress - end systolic volume index ratio (ESS/ESVI) was significantly lower in cases than controls. There were strong positive correlation between the ejection phase indices (ejection fraction and fractional shortening) and end systolic stress and ESS/ESVI. The study findings suggest the presence of left ventricular systolic dysfunction in adult sickle cell anaemia. This is best detected using the loading-pressures independent force-length relationship expressed in ESS/ESVI ratio.

In Silico Shear and Intramural Stresses are Linked to Aortic Valve Morphology in Dilated Ascending Aorta

The development of ascending aortic dilatation in patients with bicuspid aortic valve (BAV) is highly variable, and this makes surgical decision strategies particularly challenging. The purpose of this study was to identify new predictors, other than the well established aortic size, that may help to stratify the risk of aortic dilatation in BAV patients. Using fluid-structure interaction analysis, both haemodynamic and structural parameters exerted on the ascending aortic wall of patients with either BAV (n=21) or tricuspid aortic valve (TAV; n=13) with comparable age and aortic diameter (42.7±5.3mm for BAV and 45.4±10.0mm for TAV) were compared. BAV phenotypes were stratified according to the leaflet fusion pattern and aortic shape. Systolic wall shear stress (WSS) of BAV patients was higher than TAV patients at the sinotubular junction (6.8±3.3N/m2 for BAV and 3.9±1.3N/m2 for TAV; p=.006) and mid-ascending aorta (9.8±3.3N/m2 for BAV and 7.1±2.3N/m2 for TAV; p=.040). A statistically significant difference in BAV versus TAV was also observed for the intramural stress along the ascending aorta (e.g., 2.54×105±0.32×105N/m2 for BAV and 2.04×105±0.34×105N/m2 for TAV; p<.001) and pressure index (0.329±0.107 for BAV and 0.223±0.139 for TAV; p=.030). Differences in the BAV phenotypes (i.e., BAV type 1 vs. BAV type 2) and aortopathy (i.e., isolated tubular vs. aortic root dilatations) were associated with asymmetric WSS distributions in the right anterior aortic wall and right posterior aortic wall, respectively. These findings suggest that valve mediated haemodynamic and structural parameters may be used to identify which regions of aortic wall are at greater stress and enable the development of a personalised approach for the diagnosis and management of aortic dilatation beyond traditional guidelines.

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.

Vascular Endothelial Growth Factor Prevents Endothelial-to-Mesenchymal Transition in Hypertrophy

In hypertrophy, progressive loss of function caused by impaired diastolic compliance correlates with advancing cardiac fibrosis. Endothelial cells contribute to this process through endothelial-to-mesenchymal transition (EndMT) resulting from inductive signals such as transforming growth factor (TGF-β). Vascular endothelial growth factor (VEGF) has proven effective in preserving systolic function and delaying the onset of failure. In this study, we hypothesize that VEGF inhibits EndMT and prevents cardiac fibrosis, thereby preserving diastolic function. The descending aorta was banded in newborn rabbits. At 4 and 6 weeks, hypertrophied animals were treated with intrapericardial VEGF protein and compared with controls (n= 7 per group). Weekly transthoracic echocardiography measured peak systolic stress. At 7 weeks, diastolic stiffness was determined through pressure-volume curves, fibrosis by Masson trichrome stain and hydroxyproline assay, EndMT by immunohistochemistry, and activation of TGF-β and SMAD2/3 by quantitative real-time polymerase chain reaction. Peak systolic stress was preserved during the entire observation period, and diastolic compliance was maintained in treated animals (hypertrophied: 20 ± 1 vs treated: 11 ± 3 and controls: 12 ± 2; p < 0.05). Collagen was significantly higher in the hypertrophied group by Masson trichrome (hypertrophied: 3.1 ± 0.9 vs treated: 1.8± 0.6) and by hydroxyproline assay (hypertrophied: 2.8± 0.6 vs treated: 1.4 ± 0.4; p < 0.05). Fluorescent immunostaining showed active EndMT in the hypertrophied group but significantly less in treated hearts, which was directly associated with a significant increase in TGF-β/SMAD-2 messenger RNA expression. EndMT contributes to cardiac fibrosis in hypertrophied hearts. VEGF treatment inhibits EndMT and prevents the deposition of collagen that leads to myocardial stiffness through TGF-β/SMAD-dependent activation. This presents a therapeutic opportunity to prevent diastolic failure and preserve cardiac function in pressure-loaded hearts.

Aortic shear stress in patients with bicuspid aortic valve with stenosis and insufficiency

ObjectivesBicuspid aortic valve, characterized by valve malformation and risk for aortopathy, displays profound alteration in systolic aortic outflow and wall shear stress distribution. The present study performed 4-dimensional flow magnetic resonance imaging in patients with bicuspid aortic valve with right-left cusp fusion, focusing on the impact of valve function on hemodynamic status within the ascending aorta. MethodsFour-dimensional flow magnetic resonance imaging was performed in 50 subjects with right-left bicuspid aortic valve and 15 age- and aortic size–matched controls with tricuspid aortic valve. Patients with bicuspid aortic valve were categorized into 3 groups according to their aortic valve function as follows: bicuspid aortic valve with no more than mild aortic valve dysfunction (bicuspid aortic valve control, n = 20), bicuspid aortic valve with severe aortic insufficiency (n = 15), and bicuspid aortic valve with severe aortic stenosis (n = 15). ResultsAll patients with right-left bicuspid aortic valve exhibited peak wall shear stress at the right-anterior position of the ascending aorta (bicuspid aortic valve vs trileaflet aortic valve at the right-anterior position: 0.91 ± 0.23 N/m2 vs 0.43 ± 0.12 N/m2, P < .001) with no distinct alteration between bicuspid aortic valve with severe aortic insufficiency and bicuspid aortic valve with severe aortic stenosis. The predominance of dilatation involving the tubular ascending aorta (82%, type 2 aortopathy) persisted, with or without valve dysfunction. Compared with bicuspid aortic valve control subjects, the bicuspid aortic valve with severe aortic insufficiency group displayed universally elevated wall shear stress (0.75 ± 0.12 N/m2 vs 0.57 ± 0.09 N/m2, P < .01) in the ascending aorta, which was associated with elevated cardiac stroke volume (P < .05). The bicuspid aortic valve with severe aortic stenosis group showed elevated flow eccentricity in the form of significantly increased standard deviation of circumferential wall shear stress, which correlated with markedly increased peak aortic valve velocity (P < .01). ConclusionsThe location of peak aortic wall shear stress and type of aortopathy remained homogeneous among patients with right-left bicuspid aortic valve irrespective of valve dysfunction. Severe aortic insufficiency or stenosis resulted in further elevated aortic wall shear stress and exaggerated flow eccentricity.

Magnetic resonance imaging 4-D flow-based analysis of aortic hemodynamics in Turner syndrome.

Cardiovascular surveillance is important in Turner syndrome because of the increased risk of aortic dilation and dissection with consecutively increased mortality. To compare 4-D flow MRI for the characterization of aortic 3-D flow patterns, dimensions and vessel wall parameters in pediatric patients with Turner syndrome and age-matched controls. We performed 4-D flow MRI measuring in vivo 3-D blood flow with coverage of the thoracic aorta in 25 patients with Turner syndrome and in 16 female healthy controls (age mean ± standard deviation were 16 ± 5years and 17 ± 4years, respectively). Blood flow was visualized by time-resolved 3-D path lines. Visual grading of aortic flow in terms of helices and vortices was performed by two independent observers. Quantitative analysis included measurement of aortic diameters, quantification of peak systolic wall shear stress, pulsatility index and oscillatory shear index at eight defined sites. Patients with Turner syndrome had significantly larger aortic diameters normalized to BSA, increased vortices in the ascending aorta and elevated helix flow in the ascending and descending aorta compared to controls (all P<0.03). Patients with abnormal helical or vortical flow in the ascending aorta had significantly larger diameters of the ascending aorta (P<0.03). Peak systolic wall shear stress, pulsatility index and oscillatory shear index were significantly lower in Turner patients compared to controls (p=0.02, p=0.002 and p=0.01 respectively). Four-dimensional flow MRI provides new insights into the altered aortic hemodynamics and wall shear stress that could have an impact on the development of aortic dissections.

대학생의 알코올 사용장애 정도에 따른 혈압 및 스트레스의 영향요인

Purpose: The purpose of this study was to investigate the effects of general, health, and alcohol-related characteristics on blood pressure and stress according to the Alcohol Use Disorders Identification Test (AUDIT). Methods: This was a descriptive study. From participants in the 2013 Korea National Health and Nutrition Examination Survey, 319 participants who responded to the survey when they were attending college or university were selected. Data were analyzed using the SPSS Win 23.0 program for composite sample data reflecting the composite design elements of stratification, colonization, and weighting. Results: Mean age of onset of alcohol drinking was 17.91±0.16 years, the average AUDIT score was 7.56±0.41, and 25 (9.1%) participants fell into the high-risk drinking group. In the high-risk AUDIT group, systolic blood pressure was influenced by age, gender, institution, health status, body mass index, and suicidal ideation, and the explanatory power of the model (R2) was 75.0%. For diastolic blood pressure, institution and health status were the influential factors, and R2 was 66.2%. Predictors of stress were health status, depression, and the age of onset of drinking, and R2 was 57.2%. Conclusion: It was confirmed that the explanatory power of the variables in models of systolic and diastolic blood pressure and stress is greater in those with higher scores on AUDIT. Key Words: Students; Alcohols; Blood pressure; Stress Key Words: 대학생; 알코올; 혈압; ìŠ¤íŠ¸ë ˆìŠ¤

Longitudinal Evaluation of Aortic Hemodynamics in Marfan Syndrome: New Insights from a 4D Flow Cardiovascular Magnetic Resonance Multi-Year Follow-Up Study

BackgroundThe aim of this 4D flow cardiovascular magnetic resonance (CMR) follow-up study was to investigate longitudinal changes in aortic hemodynamics in adolescent patients with Marfan syndrome (MFS).Methods4D flow CMR for the assessment of in-vivo 3D blood flow with full coverage of the thoracic aorta was performed twice (baseline scan t1/follow-up scan t2) in 19 adolescent MFS patients (age at t1: 12.7 ± 3.6 years, t2: 16.2 ± 4.3 years) with a mean follow-up duration of 3.5 ± 1.2 years. Ten healthy volunteers (24 ± 3.8 years) served as a control group. Data analysis included aortic blood flow visualization by color-coded 3D pathlines, and grading of flow patterns (helices/vortices) on a 3-point scale (none, moderate, severe; blinded reading, 2 observers). Regional aortic peak systolic velocities and systolic 3D wall shear stress (WSS) along the entire aortic wall were quantified. Z-Scores of the aortic root and proximal descending aorta (DAo) were assessed.ResultsRegional systolic WSS was stable over the follow-up duration, except for a significant decrease in the proximal inner DAo segment (p = 0.02) between t1 and t2. MFS patients revealed significant lower mean systolic WSS in the proximal inner DAo compared with volunteers (0.78 ± 0.15 N/m2) at baseline t1 (0.60 ± 0.18 N/m2; p = 0.01) and follow-up t2 (0.55 ± 0.16 N/m2; p = 0.001). There were significant relationships (p < 0.01) between the segmental WSS in the proximal inner DAo, DAo Z-scores (r = −0.64) and helix/vortex pattern grading (r = −0.55) at both t1 and t2. The interobserver agreement for secondary flow patterns assessment was excellent (Cohen’s k = 0.71).ConclusionsMFS patients have lower segmental WSS in the inner proximal DAo segment which correlates with increased localized aberrant vortex/helix flow patterns and an enlarged diameter at one of the most critical sites for aortic dissection. General aortic hemodynamics are stable but these subtle localized DAo changes are already present at young age and tend to be more pronounced in the course of time.

The effect of viscous force on the prediction of muscle contractility in biohybrid cantilever-based experiments

The biohybrid cantilevers have been recently reported for high-throughput measurement of muscle contractility. In previous works, mechanical models were used to predict the contractile stress from the cantilever bending curvature. To derive those models, the cantilever bending process was considered as quasi-static and the viscous force was neglected. To ascertain the effect of the viscous force on the prediction of the muscle contractility in biohybrid cantilever-based experiments, we extend the modified Stoney’s equation to a dynamic model that takes into account both the viscous force and the inertia force. Parametric studies show that, because the viscous force hinders the movement of the cantilever, use of static models result in a system error between the calculated and true contractile stresses. When using static models, the diastolic stress will be over-estimated while the peak systolic stress will be under-estimated. The present work suggests that dynamic models can be used in biohybrid cantilever assays to calculate the muscle contractility with higher accuracy, or can be used to optimize the experimental parameters such that the error due to the use of static models is minimized.

PP.33.08] LONGITUDINAL LEFT VENTRICULAR CONTRACTILITY AND ISOLATED SYSTOLIC HYPERTENSION IN THE YOUNG

Objective: Background: Increased stroke volume and an unusual elevated amplification of the pulse wave are the main substratum of isolated systolic hypertension in the young. Objectives: to compare systolic and diastolic function in young isolated systolic and systolic-diastolic hypertensives to young normotensives. Design and method: Design and methods: under 40 years old non treated consecutives isolated systolic hypertensives, systolic-diastolic hypertensives and normotensives controls were included in a case control design. Left ventricular mass assessed by Devereux method, left ventricular hypertrophy considered > 95 g/m2 in women and > 115 g/m2 in men. Transmitral diastolic peak early flow to septal/lateral mitral annulus average peak early diastolic velocities (E/e’ ratio) measured. Systolic function assessed by tissue Doppler average interventricular septum/lateral wall mitral annulus rate systolic excursion (s wave). Left ventricular end diastolic volume, end systolic volume, stroke volume, stroke work and systolic stress were measure by volumetric methods and corrected by body surface. Statistical analysis by ANOVA test, statistically significant p < 0,05. Results: Results: 10 controls, 24 systolic – diastolic hypertensives and 14 isolated systolic hypertensives were included. Data are showed at the table.Conclusions: Conclusions: 1) LV end diastolic volume is increased in isolated systolic hypertension in the young which by Franck Starling law could recruit myocardial fibers and increased longitudinal LV contractility; 2) exaggerated LV longitudinal shortening could explain the increased stroke volume in isolated systolic young hypertensives.

Partial LVAD restores ventricular outputs and normalizes LV but not RV stress distributions in the acutely failing heart in silico.

PurposeHeart failure is a worldwide epidemic that is unlikely to change as the population ages and life expectancy increases. We sought to detail significant recent improvements to the Dassault Systèmes Living Heart Model (LHM) and use the LHM to compute left ventricular (LV) and right ventricular (RV) myofiber stress distributions under the following 4 conditions: (1) normal cardiac function; (2) acute left heart failure (ALHF); (3) ALHF treated using an LV assist device (LVAD) flow rate of 2 L/min; and (4) ALHF treated using an LVAD flow rate of 4.5 L/min.Methods and ResultsIncorporating improved systolic myocardial material properties in the LHM resulted in its ability to simulate the Frank-Starling law of the heart. We decreased myocardial contractility in the LV myocardium so that LV ejection fraction decreased from 56% to 28%. This caused mean LV end diastolic (ED) stress to increase to 508% of normal, mean LV end systolic (ES) stress to increase to 113% of normal, mean RV ED stress to decrease to 94% of normal and RV ES to increase to 570% of normal. When ALHF in the model was treated with an LVAD flow rate of 4.5 L/min, most stress results normalized. Mean LV ED stress became 85% of normal, mean LV ES stress became 109% of normal and mean RV ED stress became 95% of normal. However, mean RV ES stress improved less dramatically (to 342% of normal values).ConclusionsThese simulations strongly suggest that an LVAD is effective in normalizing LV stresses but not RV stresses that become elevated as a result of ALHF.