Association of Impaired Left Ventricular Mitral Filling from 4D Flow Cardiac MRI and Prognosis of Hypertrophic Cardiomyopathy

Purpose To investigate whether the peak early filling rate normalized to the filling volume (PEFR/FV) estimated from four-dimensional (4D) flow cardiac MRI may be used to assess impaired left ventricular (LV) filling and predict clinical outcomes in individuals with hypertrophic cardiomyopathy (HCM). Materials and Methods Cardiac MRI with a 4D flow sequence and late gadolinium enhancement (LGE), as well as echocardiography, was performed in 88 individuals: 44 participants with HCM from a French prospective registry (ClinicalTrials.gov; NCT01091480) and 44 healthy volunteers matched for age and sex. In participants with HCM, a composite primary end point was assessed at follow-up, including unexplained syncope, new-onset atrial fibrillation, hospitalization for congestive heart failure, ischemic stroke, sustained ventricular arrhythmia, septal reduction therapy, and cardiac death. A Cox proportional hazard model was used to analyze associations with the primary end point. Results PEFR/FV was significantly lower in the HCM group (mean age, 51.8 years ± 18.5 [SD]; 29 male participants) compared with healthy volunteers (mean, 3.35 sec-1 ± 0.99 [0.90-5.20] vs 4.42 sec-1 ± 1.68 [2.74-11.86]; P < .001) and correlated with both B-type natriuretic peptide (BNP) level (r = -0.31; P < .001) and the ratio of pulsed Doppler early transmitral inflow to Doppler tissue imaging annulus velocities (E/E'; r = -0.54; P < .001). At a median follow-up of 2.3 years (IQR, 1.7-3.3 years), the primary end point occurred in 14 (32%) participants. A PEFR/FV of 2.61 sec-1 or less was significantly associated with occurrence of the primary end point (hazard ratio, 9.46 [95% CI: 2.61, 45.17; P < .001] to 15.21 [95% CI: 3.51, 80.22; P < .001]), independently of age, BNP level, E/E', LGE extent, and LV and left atrial strain according to successive bivariate models. Conclusion In HCM, LV filling evaluated with 4D flow cardiac MRI correlated with Doppler and biologic indexes of diastolic dysfunction and predicted clinical outcomes. Keywords: Diastolic Function, Left Ventricular Filling, Hypertrophic Cardiomyopathy, Cardiac MRI, 4D Flow Sequence Clinical trial registration no. NCT01091480 Supplemental material is available for this article. © RSNA, 2024.

Morphological and dynamic analysis of the normal aortic valve with 4D computed tomography

OBJECTIVES

To evaluate the precise dimensions of the normal aortic root, especially the true aortic annulus, during the cardiac cycle using an innovative reconstruction method based on multiphase cardiac computed tomography and to assess the feasibility and the reproducibility of this method for aortic root analysis.

METHODS

Between January 2019 and June 2021, 30 optimal consecutive ECG-gated multiphase cardiac computed tomography of patients with normal tricuspid aortic valve were analysed using an in-house software. Aortic annulus border was pinpointed on 9 reconstructed planes and the 3D coordinates of the 18 consecutive points were interpolated into a 3D curve using a cubic spline. Three additional planes were generated at the level of the left ventricular outflow tract, the level of the Valsalva sinus and the level of the sinotubular junction. This procedure was repeated for all the 10 temporal phases of the RR interval.

RESULTS

The aortic annulus mean 3D and 2D areas were 7.67 ± 1.51 and 5.16 ± 1.40 cm2, respectively. The mean 2D diameter was 2.51 ± 0.23 cm. The mean global area expansion was 11.8 ± 3.5% and the mean perimeter expansion of 7.1 ± 2.6%. During the cardiac cycle, the left ventricle outflow tract expands, reaching its maximum surface at the end of diastole, followed by the aortic annulus, the Valsalva sinuses and the sinotubular junction. The aorta changes from a clover-shaped cone during diastole to more cylindrical shape during systole. Compared to the 3D measurements, the analysis of the virtual basal ring significantly underestimates the annulus area, perimeter, and mean diameter.

CONCLUSIONS

4D morphometric analysis enables to have a precise and reproducible evaluation of the aortic annulus. The aortic annulus and root are deformable structures that undergo a unique expansion sequence during the cardiac cycle which should be considered for procedural planning.

Automatic thoracic aorta calcium quantification using deep learning in non-contrast ECG-gated CT images

Thoracic aorta calcium (TAC) can be assessed from cardiac computed tomography (CT) studies to improve cardiovascular risk prediction. The aim of this study was to develop a fully automatic system to detect TAC and to evaluate its performance for classifying the patients into four TAC risk categories. The method started by segmenting the thoracic aorta, combining three UNets trained with axial, sagittal and coronal CT images. Afterwards, the surrounding lesion candidates were classified using three combined convolutional neural networks (CNNs) trained with orthogonal patches. Image datasets included 1190 non-enhanced ECG-gated cardiac CT studies from a cohort of cardiovascular patients (age 57 ± 9 years, 80% men, 65% TAC > 0). In the test set (N = 119), the combination of UNets was able to successfully segment the thoracic aorta with a mean volume difference of 0.3 ± 11.7 ml (<6%) and a median Dice coefficient of 0.947. The combined CNNs accurately classified the lesion candidates and 87% of the patients (N = 104) were accurately placed in their corresponding risk categories (Kappa = 0.826, ICC = 0.9915). TAC measurement can be estimated automatically from cardiac CT images using UNets to isolate the thoracic aorta and CNNs to classify calcified lesions.

Abdominal aortic calcium and geometry in patients with essential hypertension

PURPOSE

Abdominal aorta calcium (AAC) burden and dilatation are associated with an increased risk of mortality. The purpose of this study was to investigate determinants of AAC and abdominal aorta size in patients with essential hypertension.

MATERIALS AND METHODS

Patients with uncomplicated essential hypertension who had undergone non-enhanced abdominal CT to rule out secondary hypertension in addition to biological test were recruited between 2010 and 2018. A semi-automatic system was designed to estimate the aortic size (diameter, length, volume) and quantify the AAC from mesenteric artery to bifurcation using the Agatston score. Determinants of aortic size and those related to AAC were searched for using uni- and multivariables analyses.

RESULTS

Among 293 randomly selected patients with hypertension (age 52 ± 11 [SD] years) included, 23% had resistant hypertension. Mean abdominal aorta diameter was 20.1 ± 2.1 (SD) mm. Eight (3%) patients had abdominal aorta aneurysm ≥ 30 mm and 58 (20%) had dilated abdominal aorta ≥ 27 mm. Median AAC score was 38 and calcifications were detected in the infra- and supra-renal abdominal aortic portions in 59% and 26% of the patients, respectively. After adjustment for age, male sex and body surface area, abdominal aorta diameter was positively associated with diastolic blood pressure (P = 0.0019). Smoking was the single variable associated with calcified abdominal aorta (P < 0.001) after adjustment for cofactors. In patients with calcifications of abdominal aorta, the score increased with smoking history (P < 0.001), statins treatment (P < 0.01), greater number of anti-hypertensive drugs (P < 0.01), larger abdominal aorta (P < 0.05) and greater systolic blood pressure (P < 0.05). Patients with resistant hypertension had more AAC in the supra-renal abdominal aorta portion than those without resistant hypertension (P < 0.01).

CONCLUSION

In patients with essential hypertension, abdominal aorta dilation is related with diastolic blood pressure while AAC is associated with smoking history and resistant hypertension when located to the supra-renal abdominal aorta portion.

Computed tomographic analysis of the morphometrics and dynamics of the tricuspid annulus in secondary functional tricuspid regurgitation

Objectives

Secondary functional tricuspid regurgitation (FTR) management remains controversial mainly due to the lack of knowledge in its pathogenesis and the difficulties to measure the actual dimensions of tricuspid annulus (TA) with current imaging methods. Using a novel method based on multiphase cardiac computed tomography (CT) scan acquisition to accurately analyze the right atrioventricular junction size, we sought to explore modifications of TA morphometry and dynamics in secondary FTR.

Methods

Echocardiographic and cardiac CT studies were obtained from 21 patients with severe mitral regurgitation (MR group) and 21 patients with dilated cardiomyopathy (DCMP group). Using an in-house software, a 3-dimensiontal (3D) semiautomated delineation of the TA perimeter was assessed. Modifications of diameters, 2-dimensional/3D areas and perimeters were analyzed through time. These 2 groups of patients were compared with 30 healthy subjects, considering the presence of a significant (≥2+) versus nonsignificant (<2+) FTR in each group.

Results

Maximum TA 3D areas were 7.0 ± 1.2 cm2/m2 in healthy subjects at mid-to-late diastole and were smaller than in the MR group (9.8 ± 2.1 cm2/m2, P < .001) and the DCMP group (9.2 ± 3.0 cm2/m2, P < .001). In the MR group, patients with FTR <2+ had also larger TA areas and diameters than healthy patients (P < .01 for all 3D/2-dimensional parameters). TA shape was more circular only in the DCMP group with FTR ≥2+ compared with other patients (P < .05 for eccentricity). In multivariate analysis, both RA area (P < .001) and RV volume (P = .002) were independently related to TA dilatation.

Conclusions

Based on multiphase CT image analyses, TA dilatation was directly related to RV and RA enlargement. Patients with severe mitral myxomatous disease and nondysfunctional tricuspid valve had yet dilated TA, which questioned the current cut-off recommendation for concomitant tricuspid annuloplasty in this specific population.

4D flow magnetic resonance imaging to assess right ventricular outflow tract in patients undergoing transcatheter pulmonary valve replacement

INTRODUCTION AND OBJECTIVES

Magnetic resonance imaging (MRI) including 4D flow is used before percutaneous pulmonary valve implantation (PPVI). As PPVI is limited by the size of the right ventricular outflow tract (RVOT), accurate sizing is needed to plan the intervention. The aim of this study was to compare different MRI modalities and invasive angiography to balloon sizing of RVOT.

METHODS

Single-center prospective study of patients who underwent PPVI for isolated pulmonary regurgitation assessed by 4D flow MRI, 3D steady-state free precession/gradient echo (3D SSFP/GRE) and contrast magnetic resonance angiography. Balloon sizing was considered as the reference.

RESULTS

A total of 23 adults were included (mean age, 38.4±12.5 years). Eighteen patients underwent successful primary PPVI. The average of the narrowest RVOT diameter was 25.4±4.3 mm by balloon sizing. Compared to balloon sizing, RVOT diameters were better correlated when estimated by systolic 4D flow MRI (r=0.89, P<.001) than by diastolic 4D flow MRI (r=0.71, P <.001), 3D contrast magnetic resonance angiography (r=0.73; P <.001) and 3D SSFP/GRE (r=0.50; P=.04) and was not significantly correlated when estimated by 2D in diastole and systole. The mean difference between systolic 4D flow MRI and balloon sizing was 0.2 mm (95%CI, -3.5 to 3.9 mm), whereas it was wider with other techniques.

CONCLUSIONS

Beyond the quantification of pulmonary valve regurgitation, 4D flow allows accurate estimation of RVOT diameters, especially in systole, which is fundamental before planning PPVI.

Discordance between 2D and 4D flow in the assessment of pulmonary regurgitation severity: a right ventricular remodeling follow-up study

OBJECTIVES

Pulmonary regurgitation (PR) is common in adult congenital heart disease (ACHD). 2D phase contrast MRI is the reference method for the quantification of PR and helps in the decision of pulmonary valve replacement (PVR). 4D flow MRI can be an alternative method to estimate PR but more validation is still needed. Our purpose was to compare 2D and 4D flow in PR quantification using the degree of right ventricular remodeling after PVR as the reference standard.

METHODS

In 30 adult patients with a pulmonary valve disease recruited between 2015 and 2018, PR was assessed using both 2D and 4D flow. Based on the clinical standard of care, 22 underwent PVR. The pre PVR estimate of PR was compared using the post-operative decrease in right ventricle end-diastolic volume on follow-up exam as reference.

RESULTS

In the overall cohort, regurgitant volume (Rvol) and regurgitant fraction (RF) of PR measured by 2D and 4D flow were well correlated but with moderate agreement in the overall cohort (r = 0.90, mean diff.  -14 ± 12.5 mL; and r = 0.72, mean diff.  -15 ± 13%; all p < 0.0001). Correlations between Rvol estimates and right ventricle end-diastolic volume decrease after PVR was higher with 4D flow (r = 0.80, p < 0.0001) than with 2D flow (r = 0.72, p < 0.0001).

CONCLUSIONS

In ACHD, PR quantification from 4D flow better predicts post-PVR right ventricle remodeling than that from 2D flow. Further studies are needed to evaluate the added value of this 4D flow quantification for guiding replacement decision.

KEY POINTS

• Using 4D flow MRI allows a better quantification of pulmonary regurgitation in adult congenital heart disease than 2D flow when taking right ventricle remodeling after pulmonary valve replacement as a reference. • A plane positioned perpendicular to the ejected flow volume as allowed by 4D flow provides better results to estimate pulmonary regurgitation.

Case–Control Study of 3D Morphology in Isolated Mesenteric Artery Dissection

INTRODUCTION

Isolated mesenteric artery dissection (IMAD) is uncommon and has not been investigated in detail. This study aimed to accurately identify the morphological differences of IMAD patients with control individuals using a detailed 3D volumetric analysis.

METHODS

In this retrospective case-control study, cases were patients with acute symptomatic IMAD treated in a French intestinal stroke center between January 2016 and November 2019. Case-control matching was (1:3) by age, gender, and body mass index (BMI). The semi-automatic morphological analysis of the mesenteric artery included volumetric measurements of the true and false lumen size, the centerline curvature and the 3D aortomesenteric angles.

RESULTS

Seventeen IMAD cases (mean age 56 ± 4 years, 94% men) were matched with 51 controls. The mean overall lumen (OL) volume was higher in IMAD patients as compared to controls (+ 64%, p < 0.001). In the same way, the mean OL cross-sectional area and diameters were higher in IMAD patients: + 77% for OL area (< 0.001) and + 34% for OL diameters (< 0.001). Meanwhile, no significant difference was found in terms of true lumen (TL) volume (p = 0.16) or cross-sectional area (p = 0.30) between IMAD patients and controls, whereas the mean TL diameter was lower in the IMAD group (p < 0.05). Patients with acute mesenteric ischemia had a lower [TL/OL volume] ratio (45% vs. 59%, p < 0.05) and longer dissections (63 mm vs. 48 mm, p < 0.01). The 3D aortomesenteric angle was significantly higher in IMAD patients at both 2 cm (p < 0.01) and 4 cm (p < 0.05) from the ostium.

CONCLUSION

Using an original 3D semi-automated analysis, this study shows that IMAD induces significant morphological changes compared to control individuals: a larger aortomesenteric 3D angle, an increased overall volume and area. IMAD patients with acute mesenteric ischemia presented with a more severe morphological profile.

Morphological and Dynamic Analysis of the Right Atrioventricular Junction in Healthy Subjects with 4D Computed Tomography

PURPOSE

To improve knowledge of the tricuspid valve and right atrioventricular junction (RAVJ) coupling, four-dimensional (4D) imaging is mandatory (3D + time). Based on multiphase cardiac-volume computed tomography (CT) and innovative 4D analysis, we proposed to assess dynamical features of tricuspid annulus (TA) in relation to the right ventricle (RV) and right atrial (RA) functions.

METHODS

Cardiac-volume CT data sets through time were obtained in 30 healthy patients (Male 57%, mean age 57 ± 11 years). Using an in-house software, 3D semi-automated delineation of 18 points around TA perimeter were defined through 10 cardiac phases within RR interval and used to calculate TA features such as 3D/2D areas, perimeters, 360°-diameters and vertical deformation. RV and RA inner contours were also delineated. Bi-dimensional parameters were compared with multiplanar reconstruction (MPR) measurements.

RESULTS

TA was elliptical in horizontal projection with a maximal eccentricity index (EcI_max) of 0.58 ± 0.12; and saddle-shaped in vertical projection with a horn nearby the antero-septal commissure. This feature remained throughout the cardiac cycle, but TA was more planar and less circular in late diastole (TA-height: 4.53 ± 1.06 mm, EcI_max = 0.61 ± 0.14) when TA 3D area and perimeter reached a maximum of 7.05 ± 1.23 and 7.48 ± 0.93cm/m², respectively. Correlations between minimal and maximal TA 3D areas and TA Projected 2D areas were excellent (r = 0.993 and r = 0.995, p < 0.001). TA 2D area measurements by MPR overestimated the projected values by 22 to 24%. Correlation between RV concentric strain and TA maximal diameter shortening was r = 0.452 (p = 0.01).

CONCLUSIONS

Cardiac-volume CT improves physiological knowledge of the relationships between the RAVJ components in healthy subjects.

Echocardiographic measurements of the left heart chambers size in a large cohort of subjects: comparison of body surface area and height indexation to account for effects of obesity

BACKGROUND

The assessment of cardiac chamber size in the obese population is a challenging subject. Values usually indexed to body surface area (BSA) are smaller in obese subjects and prone to overcorrection. This study aimed to find reference thresholds to account for effects of obesity from a large cohort of patients and to evaluate the indexation by height as an alternative to BSA.

METHODS

The last 10-years records of our Echocardiography Unit were retrospectively analyzed and 14,007 subjects without known cardiac disease were included (45±15 years, 54% women, 20% obese). Measurements included left atrial diameter, area and volume (LAD, LAA and LAV), left ventricular (LV) end-diastolic (LVEDD) and end-systolic diameters (LVESD), aortic root diameter (ARD) and LV mass (LVM). Absolute, BSA and height indexed maximum thresholds (mean+1.96.SD) were calculated. An allometric indexation of the form variable/Height^β was tested. Correlation coefficients between indexed and absolute values were calculated to evaluate their proportional association (ideally r=1). Correlations between indexed values and body size represented residual associations to be minimized (ideally r=0).

RESULTS

The strongest association of echocardiographic measurements with body size was observed for BSA (r=0.36-0.63), whereas the isometric and allometric height models showed lower comparable values (r=0.28-0.48). Positive correlations with BMI were mostly observed for LA size (r≈0.36) and LVM (r≈0.36) measurements. Scaling exponents β for the allometric height indexation were 1.72 for LAV and 2.33 for LVM. Correlations between indexed and absolute values were higher for height than BSA (0.80-0.98 vs 0.44-0.92). Correlations between indexed values and height were closer to zero than for BSA, particularly using the allometric model. The overcorrection observed with increasing obesity class after BSA indexation was avoided after height indexation.

CONCLUSIONS

Unlike BSA, height indexing provided an adequate body size scaling of left heart chambers size avoiding overcorrection using allometric models in particular.

Thoracic Aorta Calcium Detection and Quantification Using Convolutional Neural Networks in a Large Cohort of Intermediate-Risk Patients

Arterial calcification is an independent predictor of cardiovascular disease (CVD) events whereas thoracic aorta calcium (TAC) detection might anticipate extracoronary outcomes. In this work, we trained six convolutional neural networks (CNNs) to detect aortic calcifications and to automate the TAC score assessment in intermediate CVD risk patients. Cardiac computed tomography images from 1415 patients were analyzed together with their aortic geometry previously assessed. Orthogonal patches centered in each aortic candidate lesion were reconstructed and a dataset with 19,790 images (61% positives) was built. Three single-input 2D CNNs were trained using axial, coronal and sagittal patches together with two multi-input 2.5D CNNs combining the orthogonal patches and identifying their best regional combination (BRC) in terms of lesion location. Aortic calcifications were concentrated in the descending (66%) and aortic arch (26%) portions. The BRC of axial patches to detect ascending or aortic arch lesions and sagittal images for the descending portion had the best performance: 0.954 F1-Score, 98.4% sensitivity, 87% of the subjects correctly classified in their TAC category and an average false positive TAC score per patient of 30. A CNN that combined axial and sagittal patches depending on the candidate aortic location ensured an accurate TAC score prediction.

4D flow MRI: impact of region of interest size, angulation and spatial resolution on aortic flow assessment

Objectives.In cardiovascular magnetic resonance, the 3D time-resolved phase-contrast technique, also known as 4D flow, is gaining increasing attention due to applications that exploit three-directional velocity encoding throughout the cardiac cycle. Blood flow volume assessment usually requires an expert to draw regions of interest (ROI) around the vessel cross section, whereas the errors involved in this estimation have not been thoroughly investigated. Our objective is to quantify the influence of ROI sizing, angulation and spatial resolution of the reconstructed plane employed in blood flow measurements using 4D flow.Approach.Three circular ROIs were drawn around the ascending, arch and descending aorta of healthy volunteers (n= 27) and patients with a dilated ascending aorta or bicuspid valve (n= 37). We applied systematic changes of ROI diameter (up to ±10%), tilt angle (up to ±25°) and spatial resolution (from 0.25 to 2 mm) of the reconstructed oblique planes, calculating the effects on net, forward and backward blood flow volumes.Main results.Patients had a larger ascending aorta than healthy volunteers with similar ages and male sex proportion (60 ± 15 y.o. vs 58 ± 16 y.o. and 84% vs 70%, respectively). Higher forward and backward flow volumes were observed in the ascending aorta and the aortic arch of the patients with respect to controls (p< 0.001), whereas net volumes were similar: 74.0 ± 20.8 ml versus 75.7 ± 21.8 ml (p= 0.37), respectively. The ascending aorta was the most sensitive to ROI modifications. Changes of ±10% in the ROI diameter and ±25° in tilt angles produced flow volume differences of up to 9 ml (10%) and 18 ml (15%) in controls and patients, respectively. Modifying the reconstructed planes spatial resolution produced flow volume changes below 2 ml.Significance.Since the setting of the ROI size and plane angle could produce errors that represent up to 20% of the forward and/or backward aortic flow volume, a good standardization for vessel segmentation and plane positioning is desirable.

Comprehensive assessment of local and regional aortic stiffness in patients with tricuspid or bicuspid aortic valve aortopathy using magnetic resonance imaging

BACKGROUND

We aimed to provide a comprehensive aortic stiffness description using magnetic resonance imaging (MRI) in patients with ascending thoracic aorta aneurysm and tricuspid (TAV-ATAA) or bicuspid (BAV) aortic valve.

METHODS

This case-control study included 18 TAV-ATAA and 19 BAV patients, with no aortic valve stenosis/severe regurgitation, who were 1:1 age-, gender- and central blood pressures (BP)-matched to healthy volunteers. Each underwent simultaneous aortic MRI and BP measurements. 3D anatomical MRI provided aortic diameters. Stiffness indices included: regional ascending (AA) and descending (DA) aorta pulse wave velocity (PWV) from 4D flow MRI; local AA and DA strain, distensibility and theoretical Bramwell-Hill (BH) model-based PWV, as well as regional arch PWV from 2D flow MRI.

RESULTS

Patient groups had significantly higher maximal AA diameter (median[interquartile range], TAV-ATAA: 47.5[42.0-51.3]mm, BAV: 45.0[41.0-47.0]mm) than their respective controls (29.1[26.8-31.8] and 28.1[26.0-32.0]mm, p < 0.0001), while BP were similar (p ≥ 0.25). Stiffness indices were significantly associated with age (ρ ≥ 0.33), mean BP (arch PWV: ρ = 0.25, p = 0.05; DA distensibility: ρ = -0.30, p = 0.02) or AA diameter (arch PWV: ρ = 0.28, p = 0.03; DA PWV: ρ = 0.32, p = 0.009). None of them, however, was significantly different between TAV-ATAA or BAV patients and their matched controls. Finally, while direct PWV measures were significantly correlated to BH-PWV estimates in controls (ρ ≥ 0.40), associations were non-significant in TAV-ATAA and BAV groups (p ≥ 0.18).

CONCLUSIONS

The overlap of MRI-derived aortic stiffness indices between patients with TAV or BAV aortopathy and matched controls highlights another heterogeneous feature of aortopathy, and suggests the urgent need for more sensitive indices which might help better discriminate such diseases.

High-resolution analysis with multiphase computed tomography of the left atrio-ventricular junction in mitral annular disjunction

Background

Mitral annular disjunction (MAD) has been associated with myxomatous mitral valve disease (MMVD) but functional analyses of the mitral annulus (MA) and the entire left atrio-ventricular junction (LAVJ) are lacking from high-resolution imaging to understand MAD physiopathology.

Purpose

Using multiphase cardiac computed tomography imaging (4D-MCCTI), we aimed at characterizing the morphological changes of MA and LAVJ throughout the cardiac cycle.

Methods

Volume imaging data sets through time were obtained from 4D-MCCTI of 2 groups of 10 patients as defined by echocardiographic diagnosis of MMVD and/or MAD: MMVD+MAD+, MMVD+MAD− and 20 case-controls without mitral regurgitation (MMVD−). Data were implemented in a custom software for 3D semi-automated delineation of 18 points around MA perimeter. Coordinates of these points in each of the 10 time-phases within an RR interval were used for MA reconstruction and calculation of areas, perimeters, 360°-diameters and parameters of planar/vertical deformation. Subsequently, left ventricle (LV) and left atrium (LA) inner contours were delineated.

Results

Groups were similar for age, body surface area and LV ejection fraction. Compared to the 2 other groups, MA expansion in MMVD+MAD+ started early after end-diastole, following LA expansion, and reached a maximum at end-systole (ES): 3D-area ES: 13.9±4.0cm2/m2, 3D-perimeterE S: 10.4±1.6cm/m2 versus respectively 8.8±3.0cm2/m2, 7.9±1.4cm/m2 in MMVD+MAD− (p&lt;0.001) and 6.1±1.3cm2/m2, 7.0±1.1cm/m2 in MVVD− (p&lt;0.001). However throughout the cardiac cycle, MA perimeter reduction was not altered in MMVD+MAD+: −14.0±6.3%, compared to MMVD+MAD−: −10.1±5.6% and MMVD−: −8.7±2.3% (p=0.09). MA shape modification was different in MMVD+MAD+ group, MA becoming more elliptical during systole, whereas MA reached a minimal eccentricity index (EcI) at ES in both MMVD+MAD− and MMVD− groups: EcIES = 0.63±0.09 versus 0.52±0.15 and 0.49±0.13 (p=0.04), respectively (Figure). Surprisingly, vertical deformation of MA increased during early systole in MMVD+MAD+ group when MA became more planar in the MMVD+MAD− and MMVD− groups.

Conclusions

MA function was globally preserved in MAD but was desynchronized with respect to LV contraction.

Eccentricity index of mitral annulus

Funding Acknowledgement

Type of funding source: None

Dynamics of the right atrio-ventricular junction in human: a spatial high-resolution study with multiphase computed tomography

Introduction

In order to improve knowledge of the tricuspid valve (TV) function and its coupling with the right atrio-ventricular junction (RAVJ) and right ventricle (RV), new four-dimensional high-definition imagery methods are mandatory (3D+t).

Purpose

Using an innovative reconstruction method based on multiphase cardiac computed tomography imaging (4D-MCCTI), we finely analyzed the morphological & dynamical features of tricuspid annulus (TA) and RAVJ components in order to assess new functional parameters of TV and RV functions.

Methods

Volume imaging data sets through time were obtained from 4D-MCCTI of 30 subjects (sex ratio 1, mean age 57±11y.) with no rhythm, valvular or ventricular abnormalities on echocardiography and implemented in a custom software for 3D semi-automated delineation of 18 points around TA perimeter. Coordinates of these points in each of the 10 time-phases within an RR interval were used to calculate specific geometrical features of TA such as 3D/2D areas, perimeters, 360°-diameters and vertical deformation. Subsequently, RV and Right Atrium (RA) inner contours were also delineated (Figure).

Results

TA shape was elliptical in horizontal projection with a mean eccentricity index (EcI) of 0.58±0.12; and saddle-shapped in vertical projection with a horn nearby the antero-septal commissure. This feature remained throughout the cardiac cycle but TA was more planar (minimal TA-height: 4.47±1.04 mm) and circular (minimal EcI=0.44±0.14) in mid-diastole when TA-3Darea and TA-3Dperimeter reached a maximum of 6.98±1.21 cm2/m2 and 7.41±0.91 cm, respectively. Correlation between TA-3Darea, TA-2Darea and latero-septal diameter (LSD) were R2=0.99 and R2=0.73, respectively. LSD was minimal in early-systole (18.83±3.04 mm/m2) and maximal in mid-diastole (20.04±3.05 mm/m2). Correlation of TA-3Darea with RV and RA cross-sectional areas were R2=0.82 and R2=0.71, respectively. Conversely, there was no significant correlation between TA, RV and RA concentric contractions.

Conclusions

Our method for 4D-MTCCI analysis has allowed confirming the shape and dynamics function of RAVJ throughout the cardiac cycle in healthy subjects, and giving new reference parameters for TV and RV evaluation.

Software multiplanar view of TA

Funding Acknowledgement

Type of funding source: None

Association of calcium density in the thoracic aorta with risk factors and clinical events

OBJECTIVES

In the ascending aorta, calcification density was independently and inversely associated with cardiovascular disease (CVD) risk prediction. Until now, the density of thoracic aorta calcium (TAC) was estimated as the Agatston score divided by the calcium area (D_AG). We thought to analyze TAC density in a full Hounsfield unit (HU) range and to study its association with TAC volume, traditional risk factors, and CVD events.

METHODS

Non-enhanced CT images of 1426 patients at intermediate risk were retrospectively reviewed. A calcium density score was estimated as the average of the maximum HU attenuation in all calcified plaques of the entire thoracic aorta (D_AV).

RESULTS

During a mean 4.0 years follow-up, there were 26 events for a total of 674 patients with TAC > 0. TAC volume and D_AV were positively correlated (R = 0.72). The median D_AV value was 457 HU (IQ 323-603 HU) and was exponentially related to D_AG (R = 0.86). D_AV was inversely associated with systolic pressure (p < 0.05), pulse pressure (p < 0.01), hypertension (p < 0.05), and 10-year FRS (p < 0.001) after adjusting for TAC volume. When TAC volume and D_AV were included in a logistic model, a significant improvement was shown in CVD risk estimation beyond coronary artery calcium (CAC) (AUC = 0.768 vs 0.814, p < 0.05). In multivariable Cox models, TAC volume and D_AV showed an independent association with CVD.

CONCLUSIONS

In intermediate risk patients, TAC density was inversely associated with several risk factors after adjustment for TAC volume. A significant improvement was observed over CAC when TAC volume and density were added into the risk prediction model.

KEY POINTS

• Calcifications in the aorta can be non-invasively assessed using CT images • A higher calcium score is associated with a higher cardiovascular risk • Measuring the calcifications size and the density separately can improve the risk prediction.

Comparison of different methods for the estimation of aortic pulse wave velocity from 4D flow cardiovascular magnetic resonance

BACKGROUND

Arterial pulse wave velocity (PWV) is associated with increased mortality in aging and disease. Several studies have shown the accuracy of applanation tonometry carotid-femoral PWV (Cf-PWV) and the relevance of evaluating central aorta stiffness using 2D cardiovascular magnetic resonance (CMR) to estimate PWV, and aortic distensibility-derived PWV through the theoretical Bramwell-Hill model (BH-PWV). Our aim was to compare various methods of aortic PWV (aoPWV) estimation from 4D flow CMR, in terms of associations with age, Cf-PWV, BH-PWV and left ventricular (LV) mass-to-volume ratio while evaluating inter-observer reproducibility and robustness to temporal resolution.

METHODS

We studied 47 healthy subjects (49.5 ± 18 years) who underwent Cf-PWV and CMR including aortic 4D flow CMR as well as 2D cine SSFP for BH-PWV and LV mass-to-volume ratio estimation. The aorta was semi-automatically segmented from 4D flow data, and mean velocity waveforms were estimated in 25 planes perpendicular to the aortic centerline. 4D flow CMR aoPWV was calculated: using velocity curves at two locations, namely ascending aorta (AAo) and distal descending aorta (DAo) aorta (S1, 2D-like strategy), or using all velocity curves along the entire aortic centreline (3D-like strategies) with iterative transit time (TT) estimates (S2) or a plane fitting of velocity curves systolic upslope (S3). For S1 and S2, TT was calculated using three approaches: cross-correlation (TTc), wavelets (TTw) and Fourier transforms (TTf). Intra-class correlation coefficients (ICC) and Bland-Altman biases (BA) were used to evaluate inter-observer reproducibility and effect of lower temporal resolution.

RESULTS

4D flow CMR aoPWV estimates were significantly (p < 0.05) correlated to the CMR-independent Cf-PWV, BH-PWV, age and LV mass-to-volume ratio, with the strongest correlations for the 3D-like strategy using wavelets TT (S2-TTw) (R = 0.62, 0.65, 0.77 and 0.52, respectively, all p < 0.001). S2-TTw was also highly reproducible (ICC = 0.99, BA = 0.09 m/s) and robust to lower temporal resolution (ICC = 0.97, BA = 0.15 m/s).

CONCLUSIONS

Reproducible 4D flow CMR aoPWV estimates can be obtained using full 3D aortic coverage. Such 4D flow CMR stiffness measures were significantly associated with Cf-PWV, BH-PWV, age and LV mass-to-volume ratio, with a slight superiority of the 3D strategy using wavelets transit time (S2-TTw).

Effects on Aortoiliac Fluid Dynamics After Endovascular Sealing of Abdominal Aneurysms

OBJECTIVES:

To evaluate the effects on aortoiliac fluid dynamics after the implantation of an endograft based on endovascular aneurysm sealing (EVAS) versus endovascular aneurysm repair (EVAR) strategy.

METHODS:

An adaptive geometrical deformable model was used for aortic lumen segmentation in 8 patients before and after the surgery. Abdominal aneurysms were treated with an endograft based on the EVAS system (Nellix, n = 4) and with a device based on an anatomical fixation technology (n = 4). Pressure, blood velocity, and wall shear stress (WSS) were estimated at different aortic regions using computational fluid dynamics methods. Physiologic inlet/outlet flow values at the abdominal aorta, the celiac trunk, and the mesenteric and the renal arteries were set. Pressure references were set at iliac arteries outlet.

RESULTS:

Maximum aneurysm sizes were similar for both groups in the preoperative scans. The lumen area was lower after EVAR ( P < .05) and EVAS ( P < .01) compared to preoperative aortic lumen sizes. Pressure increase was higher in the proximal abdominal aorta after EVAS compared to EVAR (2.3 ± 0.3 mm Hg vs 0.9 ± 0.3 mm Hg, P < .001). Peak blood velocities inside the endografts were 3-fold higher for EVAS compared to EVAR (54 ± 5 cm/s vs 17 ± 4 cm/s, P < .01). Velocities at the iliac arteries also remained higher for EVAS (38 ± 4 cm/s vs 24 ± 4 cm/s, P < .05). Peak WSS at the iliac arteries remained higher for EVAS compared to EVAR group ( P < .05).

CONCLUSION:

The significant modification of the aortic bifurcation anatomy after EVAS alters aortoiliac fluid dynamics, showing a pressure impact at the renal arteries level and an acceleration of the blood velocity at the iliac region with a concomitant increase in peak WSS.

Stroke and Neurodegeneration Induce Different Connectivity Aberrations in the Insula

BACKGROUND AND PURPOSE

Stroke and neurodegeneration cause significant brain damage and cognitive impairment, especially if the insular cortex is compromised. This study explores for the first time whether these 2 causes differentially alter connectivity patterns in the insular cortex.

METHODS

Resting state-functional magnetic resonance imaging data were collected from patients with insular stroke, patients with behavioral variant frontotemporal dementia, and healthy controls. Data from the 3 groups were assessed through a correlation function analysis. Specifically, we compared decreases in connectivity as a function of voxel Euclidean distance within the insular cortex.

RESULTS

Relative to controls, patients with stroke showed faster connectivity decays as a function of distance (hypoconnectivity). In contrast, the behavioral variant frontotemporal dementia group exhibited significant hyperconnectivity between neighboring voxels. Both patient groups evinced global hypoconnectivity. No between-group differences were observed in a volumetrically and functionally comparable region without ischemia or neurodegeneration.

CONCLUSIONS

Functional insular cortex connectivity is affected differently by cerebral ischemia and neurodegeneration, possibly because of differences in the cause-specific pathophysiological mechanisms of each disease. These findings have important clinical and theoretical implications.

Continuous assessment of carotid intima-media thickness applied to estimate a volumetric compliance using B-mode ultrasound sequences

Recent reports have shown that the carotid artery wall had significant movements not only in the radial but also in the longitudinal direction during the cardiac cycle. Accordingly, the idea that longitudinal elongations could be systematically neglected for compliance estimations became controversial. Assuming a dynamic change in vessel length, the standard measurement of cross-sectional compliance can be revised. In this work, we propose to estimate a volumetric compliance based on continuous measurements of carotid diameter and intima-media thickness (IMT) from B-mode ultrasound sequences. Assuming the principle of conservation of the mass of wall volume (compressibility equals zero), a temporal longitudinal elongation can be calculated to estimate a volumetric compliance. Moreover, elongations can also be estimated allowing small compressibility factors to model some wall leakage. The cross-sectional and the volumetric compliance were estimated in 45 healthy volunteers and 19 asymptomatic patients. The standard measurement underestimated the volumetric compliance by 25% for young volunteers (p < 0.01) and 17% for patients (p < 0.05). When compressibility factors different from zero were allowed, volunteers and patients reached values of 9% and 4%, respectively. We conclude that a simultaneous assessment of carotid diameter and IMT can be employed to estimate a volumetric compliance incorporating a longitudinal elongation. The cross-sectional compliance, that neglects the change in vessel length, underestimates the volumetric compliance.

Calcifications of the thoracic aorta on extended non-contrast-enhanced cardiac CT

Background

The presence of calcified atherosclerosis in different vascular beds has been associated with a higher risk of mortality. Thoracic aorta calcium (TAC) can be assessed from computed tomography (CT) scans, originally aimed at coronary artery calcium (CAC) assessment. CAC screening improves cardiovascular risk prediction, beyond standard risk assessment, whereas TAC performance remains controversial. However, the curvilinear portion of the thoracic aorta (TA), that includes the aortic arch, is systematically excluded from TAC analysis. We investigated the prevalence and spatial distribution of TAC all along the TA, to see how those segments that remain invisible in standard TA evaluation were affected.

Methods and Results

A total of 970 patients (77% men) underwent extended non-contrast cardiac CT scans including the aortic arch. An automated algorithm was designed to extract the vessel centerline and to estimate the vessel diameter in perpendicular planes. Then, calcifications were quantified using the Agatston score and associated with the corresponding thoracic aorta segment. The aortic arch and the proximal descending aorta, “invisible” in routine CAC screening, appeared as two vulnerable sites concentrating 60% of almost 11000 calcifications. The aortic arch was the most affected segment per cm length. Using the extended measurement method, TAC prevalence doubled from 31% to 64%, meaning that 52% of patients would escape detection with a standard scan. In a stratified analysis for CAC and/or TAC assessment, 111 subjects (46% women) were exclusively identified with the enlarged scan.

Conclusions

Calcium screening in the TA revealed that the aortic arch and the proximal descending aorta, hidden in standard TA evaluations, concentrated most of the calcifications. Middle-aged women were more prone to have calcifications in those hidden portions and became candidates for reclassification.

Arterial pressure fractality is highly dependent on wave reflection

Wave reflection is an important factor that influences pressure wave morphology and becomes more significant with aging, when cardiovascular risk increases. A pressure wave, measured at any location in the arterial tree, can be decomposed into its forward and backward components and depends on the corresponding amplitude and shifting time delays. Fractal dimension (FD) quantifies the time series complexity defined by its geometrical representation.

OBJECTIVE

The aim of this study was to evaluate the arterial pressure and diameter time series in order to assess the relationship between wave reflection and arterial pressure fractal dimension (FD).

METHODS

Simultaneous aortic pressure and diameter were measured in 14 conscious dogs. A pair of ultrasonic crystals, a pressure microtransducer and a pneumatic cuff occluder were positioned in the upper third of the descending aorta.

RESULTS

Total reflection induced by the occlusion maneuver decreased FD concomitant to the aortic stiffening.

CONCLUSION

Arterial pressure fractality is highly dependent on wave reflection.

Effects of aging on thoracic aorta size and shape: a non-contrast CT study

Measures of atherosclerosis burden like coronary artery calcification are performed using non-contrast heart CT. However, additional information can be derived from these studies, looking beyond the coronary arteries without exposing the patients to further radiation. We present a semi-automated method to assess ascending, arch and descending aorta geometry from non-contrast CT datasets in 250 normotensive patients. We investigated the effect of aging on thoracic aorta morphometry. The algorithm identifies the aortic centerline coordinates following a toroidal path for the curvilinear portion and axial planes for descending aorta. Then it reconstructs oblique planes orthogonal to the centerline direction and a circle fitting process estimates the vessel cross-section. Finally, global thoracic aorta dimensions (diameter, volume and length) and shape (vessel curvature and tortuosity, aortic arch width and height) are calculated. From a multivariate analysis, adjusted for gender and body-size area, aortic volume and arch width were the descriptors that better represented the aortic size and shape alterations with aging. The thoracic aorta suffers an expanding and unfolding process with aging that deserves further attention to prevent aortic aneurisms.

Non invasive assessment of carotid and femoral arterial pressure using B-mode ultrasound diameter waveforms

Non invasive local arterial blood pressure measurement has become a challenge over recent years. The aim of this study was to evaluate in a general population the validity of an alternative method to assess systolic local arterial blood pressure, from the analysis of B-mode diameter waveforms, and to estimate the accuracy when compared to carotid and femoral arterial tonometry. In 190 asymptomatic subjects (51±11 years, range: 24-73; pulse pressure: 51±11 mmHg, range: 31-93) systolic arterial pressure was obtained at the left carotid and left femoral artery by applanation tonometry (SBP(Car)_Ton and SBP(Fem)_Ton) and by automatic analysis of B-mode echographic images, calibrated using an iterative exponential model. Tonometry and echocardiography-derived pressure estimates correlated significantly (R=0.99, p&#60;0.05). Mean difference between the two methods was only -2.5±5.0 mmHg for carotid artery (SBP(Car)_Ton: 122±18 mHg), and -2.1±5.7 mmHg for femoral artery (SBP(Fem)_Ton: 134±21 mmHg), independent of pressure level. In conclusion, alternative method was found to allow an accurate and precise estimation of systolic local arterial pressure, with an underestimation error of ∼ 2%.

Three-dimensional evaluation of thoracic aorta enlargement and unfolding in hypertensive men using non-contrast computed tomography

Aging produces a simultaneous thoracic aorta (TA) enlargement and unfolding. We sought to analyze the impact of hypertension on these geometric changes. Non-contrast computed tomography images were obtained from coronary artery calcium scans, including the entire aortic arch, in 200 normotensive and 200 hypertensive asymptomatic men. An automated algorithm reconstructed the vessel in three-dimensions, estimating orthogonal aortic sections along the whole TA pathway, and calculated several geometric descriptors to assess TA morphology. Hypertensive patients were older with respect to normotensive (P<0.001). Diameter and volume of TA ascending, arch and descending segments were higher in hypertensive patients with respect to normotensive (P<0.001) and differences persisted after adjustment for age. Hypertension produced an accelerated unfolding effect on TA shape. We found increments in aortic arch width (P<0.001), radius of curvature (P<0.001) and area under the arch curve (P<0.01) with a concomitant tortuosity decrease (P<0.05) and no significant change in aortic arch height. Overall, hypertension produced an equivalent effect of 2-7-years of aging. In multivariate analysis adjusted for age and hypertension treatment, diastolic pressure was more associated to TA size and shape changes than systolic pressure. These data suggest that hypertension accelerates TA enlargement and unfolding deformation with respect to the aging effect.

Aging impact on thoracic aorta 3D morphometry in intermediate-risk subjects: looking beyond coronary arteries with non-contrast cardiac CT

An increasing number of intermediate risk asymptomatic subjects benefit from measures of atherosclerosis burden like coronary artery calcification studies with non-contrast heart computed tomography (CT). However, additional information can be derived from these studies, looking beyond the coronary arteries and without exposing the patients to further radiation. We report a semi-automatic method that objectively assesses ascending, arch and descending aorta dimension and shape from non-contrast CT datasets to investigate the effect of aging on thoracic aorta geometry. First, the segmentation process identifies the vessel centerline coordinates following a toroidal path for the curvilinear portion and axial planes for descending aorta. Then, reconstructing oblique planes orthogonal to the centerline direction, it iteratively fits circles inside the vessel cross-section. Finally, regional thoracic aorta dimensions (diameter, volume and length) and shape (vessel curvature and tortuosity) are calculated. A population of 200 normotensive men was recruited. Length, mean diameter and volume differed by 1.2 cm, 0.13 cm and 21 cm(3) per decade of life, respectively. Aortic shape uncoiled with aging, reducing its tortuosity and increasing its radius of curvature. The arch was the most affected segment. In conclusion, non-contrast cardiac CT imaging can be successfully employed to assess thoracic aorta 3D morphometry.

Validity of a new method to estimate mean arterial pressure at brachial level

The value of mean arterial pressure (MBP) is of clinical importance, and is required for peripheral resistance calculation as well as for central blood pressure calibration procedures. MBP is usually estimated at the upper arm using systolic and diastolic sphygmomanometers pressure values, as 33% of pulse pressure (PP) above diastolic pressure. In a previous work, we proposed to use 38%. The aim of this study was to investigate the validity of the proposed formula to calculate MBP, when assessing subjects with a wide range of blood pressure and pulse wave velocity (PWV) levels. In 73 volunteers (56 ± 10 years, range: 27-82; pulse pressure: 59 ± 12 mmHg, range: 43-86; PWV: 10 ± 2 m/s, range: 8-17) arterial pressure waveforms were obtained at the left brachial artery by applanation tonometry. Diastolic (DBP) and systolic (SBP) brachial pressure were obtained with oscillometric device. Brachial-radial PWV was obtained at the same arm using mechano-transducers. MBP computed as 38% of PP above diastolic pressure, introduces an error of only 0.1% in brachial MBP estimation, independent of pressure and PWV levels.

Fractional order models of viscoelasticity as an alternative in the analysis of red blood cell (RBC) membrane mechanics

New lumped-element models of red blood cell mechanics can be constructed using fractional order generalizations of springs and dashpots. Such 'spring-pots' exhibit a fractional order viscoelastic behavior that captures a wide spectrum of experimental results through power-law expressions in both the time and frequency domains. The system dynamics is fully described by linear fractional order differential equations derived from first order stress-strain relationships using the tools of fractional calculus. Changes in the composition or structure of the membrane are conveniently expressed in the fractional order of the model system. This approach provides a concise way to describe and quantify the biomechanical behavior of membranes, cells and tissues.

Estimation of coronary length-volume allometric relations of human arteries in vivo using CT

Assessing the individual geometry of the coronary arteries in a patient can help to explain diffuse artery disease. Some allometric functions, relating arterial length and volume, were verified in porcine arteries and human autopsies but not in vivo. In this work we use skeletonization methods on MSCT images to render the whole coronary tree in healthy and cardiovascular patients. Twenty patients with and without coronary artery disease were recruited. The coronary was segmented with minimum user intervention. Vessels were separated and measured. A 3D coronary map was individually calculated. The allometric length-volume function L=k(v)V(β) was evaluated in each patient and plotted in a Log-Log scale. The coefficient k(v) ranged 1.00 ± 0.35. Slopes ranged β = 0.69-0.88 and seemed to overlap in the scatter Log plot. The analysis of covariance verified this perception and concluded that lines were parallel. In other words, the allometric function stood for all patients. Values were not different from other studies in humans and pigs. The combination of multislice CT with morphological extraction algorithms was effective to extract allometric functions from coronary arteries in patients and can be easily applied in the clinic.

Angle estimation of human femora in a three-dimensional virtual environment

The estimation of human femur morphology and angulation provide useful information for assisted surgery, follow-up evaluation and prosthesis design, cerebral palsy management, congenital dislocation of the hip and fractures of the femur. Conventional methods that estimate femoral neck anteversion employ planar projections because accurate 3D estimations require complex reconstruction routines. In a recent work, we proposed a cylinder fitting method to estimate bifurcation angles in coronary arteries and we thought to test it in the estimation of femoral neck anteversion, valgus and shaft-neck angles. Femora from 10 patients were scanned using multisliced computed tomography. Virtual cylinders were fitted to 3 regions of the bone painted by the user to automatically estimate the femoral angles. Comparisons were made with a conventional manual method. Inter- and intra-reading measurements were evaluated for each method. We found femoral angles from both methods strongly correlated. Average anteversion, neck-shaft and valgus angles were 17.5°, 139.5°, 99.1°, respectively. The repeatability and reproducibility of the automated method showed a 5-fold reduction in inter- and intra-reading variability. Accordingly, the coefficients of variation for the manual method were below 25% whereas for the automated method were below 6%. The valgus angle assessment was globally the most accurate with differences below 1°. Maximum distances from true surface bone points and fitting cylinders attained 6 mm. The employment of virtual cylinders fitted to different regions of human femora consistently helped to assess true 3D angulations.

Association between mechanics and structure in arteries and veins: theoretical approach to vascular graft confection

Biomechanical and functional properties of tissue engineered vascular grafts must be similar to those observed in native vessels. This supposes a complete mechanical and structural characterization of the blood vessels. To this end, static and dynamic mechanical tests performed in the sheep thoracic and abdominal aorta and the cava vein were contrasted with histological quantification of their main constituents: elastin, collagen and muscle cells. Our results demonstrate that in order to obtain adequate engineered vascular grafts, the absolute amount of collagen fibers, the collagen/elastin ratio, the amount of muscle cells and the muscle cells/elastic fibers ratio are necessary to be determined in order to ensure adequate elastic modulus capable of resisting high stretches, an adequate elastic modulus at low and normal stretch values, the correct viscous energy dissipation, and a good dissipation factor and buffering function, respectively.

Arterial complex elastic modulus was preserved after an intercontinental cryoconserved exchange

There is a pressing need to obtain adequate vascular substitutes for arterial by-pass or reconstruction. Since the performance of venous and commercially prosthetic grafts is not ideal and the availability of autologous arteries is limited, the use of cryopreserved arteries has emerged as a very attractive alternative. In this sense, the development of an inter-continental network for cryopreserved tissue exchange would improve international cooperation increasing the possibilities of obtaining the requested materials. In this work, the effects of an inter-continental shipment, which includes cryopreservation, on the biomechanical properties of sheep aortas were evaluated by means of the arterial complex elastic modulus. It is shown that these properties were preserved after the shipment. The actual possibilities of establishing a network for arterial exchange for the international cooperation are discussed.

Reactive hyperemia-related changes in carotid-radial pulse wave velocity as a potential tool to characterize the endothelial dynamics

Current methods used to evaluate the endothelial function have limitations. The analysis of the pulse wave velocity (PWV) response to transient ischaemia could be an alternative to evaluate the endothelial dynamics.

AIMS

To analyze (a) the carotid-radial PWV temporal profile during flow mediated dilatation test, and (b) the PWV changes considering its main vascular geometrical (diameter) and intrinsic (elastic modulus) determinants.

METHODS

Sixteen healthy young adults were included. The carotid-radial PWV (strain gauge mechano-transducers), wall thickness and brachial diameter (B-Mode ultrasound) were measured before (basal state), during a forearm cuff inflation (5 minutes) and after its deflation (10 minutes). The PWV, brachial diameter and elastic modulus changes and temporal profile were analyzed (basal state, 15, 30, 45, and 60 seconds after cuff deflation).

RESULTS

Transient ischaemia was associated with arterial stiffness changes, evidenced by carotid-radial PWV variations. The PWV and diastolic diameter changes, and temporal profiles differed. The arterial stiffness changes could not be explained only by geometrical (diameter) changes.

CONCLUSION

The carotid-radial PWV analysis, evaluated using robust and simple available techniques, could be used in the clinical practice to study the vascular response to transient ischaemia and the endothelial function.

Biomechanics of the ergometric stress tests: regional and local effects on elastic, transitional and muscular human arteries

Ergometric exercise stress tests (EST) give important information about the cardiovascular (CV) response to increased demands. The expected EST-related changes in variables like blood pressure and heart rate are known, but those in the arterial biomechanics are controversial and incompletely characterized.

AIMS

a) to characterize the regional and local arterial biomechanical behavior in response to EST, and its temporal profile in the post-EST recovery phase and (b) to compare different arteries biomechanical response to EST.

METHODS

In 16 non-trained healthy young subjects the carotid-femoral pulse wave velocity and the carotid, femoral and brachial arterial distensibility were non-invasively evaluated before (Rest) and after EST. Post exercise recordings were obtained 0-1, 4-5, and 9-10 minutes after exercise.

RESULTS

The EST resulted in an early increase in the arterial stiffness, evidenced by regional and local parameters. There were quali-quantitative differences among the arterial local stiffness response to EST, when analyzing conjunctly the different postEST recovery stages. The biomechanical changes could not be explained only by blood pressure variations.