Age related changes of human aortic distensibility: evaluation with ECG-gated CT

Magnetic Resonance Imaging and Computed Tomography for the Noninvasive Assessment of Arterial Aging: A Review by the VascAgeNet COST Action

Magnetic resonance imaging and computed tomography allow the characterization of arterial state and function with high confidence and thus play a key role in the understanding of arterial aging and its translation into the clinic. Decades of research into the development of innovative imaging sequences and image analysis techniques have led to the identification of a large number of potential biomarkers, some bringing improvement in basic science, others in clinical practice. Nonetheless, the complexity of some of these biomarkers and the image analysis techniques required for their computation hamper their widespread use. In this narrative review, current biomarkers related to aging of the aorta, their founding principles, the sequence, and postprocessing required, and their predictive values for cardiovascular events are summarized. For each biomarker a summary of reference values and reproducibility studies and limitations is provided. The present review, developed in the COST Action VascAgeNet, aims to guide clinicians and technical researchers in the critical understanding of the possibilities offered by these advanced imaging modalities for studying the state and function of the aorta, and their possible clinically relevant relationships with aging.

Towards a Clinical Implementation of Measuring the Elastic Modulus of the Aorta from Cardiac Computed Tomography Images

OBJECTIVE

The elasticity of the aortic wall varies depending on age, vessel location, and the presence of aortic diseases. Noninvasive measurement will be a powerful tool to understand the mechanical state of the aorta in a living human body. This study aimed to determine the elastic modulus of the aorta using computed tomography images.

METHODS

We constructed our original formulae based on mechanics of materials. Then, we performed computed tomography scans of a silicon rubber tube by applying four pressure conditions to the lumen. The segment elastic modulus was calculated from the scanned images using our formulae. The actual modulus was measured using a tensile loading test for comparison.

RESULTS

The segment moduli of elasticity from the images were 0.525 [0.524, 0.527], 0.524 [0.520, 0.524], 0.520 [0.515, 0.523], and 0.522 [0.516, 0.532] (unit: MPa, median [25%, 75% quantiles]) for the four pressure conditions, respectively. The corresponding measurements in the tensile test were 0.548 [0.539, 0.566], 0.535 [0.528, 0.553], 0.526 [0.513, 0.543], and 0.523 [0.508, 0.530], respectively. These results indicated errors of 4.2%, 2.1%, 1.1%, and 0.2%, respectively.

CONCLUSION

Our formulae provided good estimations of the segment elastic moduli of a silicon rubber tube under physiological pressure conditions using the computed tomography images.

SIGNIFICANCE

In addition to the elasticity, the formulae provide the strain energy as well. These properties can be better predictors of aortic diseases. The formulae consist of clinical parameters commonly used in medical settings (pressure, diameter, and wall thickness).

An in silico study of the influence of vessel wall deformation on neointimal hyperplasia progression in peripheral bypass grafts

Neointimal hyperplasia (NIH) is a major obstacle to graft patency in the peripheral arteries. A complex interaction of biomechanical factors contribute to NIH development and progression, and although haemodynamic markers such as wall shear stress have been linked to the disease, these have so far been insufficient to fully capture its behaviour. Using a computational model linking computational fluid dynamics (CFD) simulations of blood flow with a biochemical model representing NIH growth mechanisms, we analyse the effect of compliance mismatch, due to the presence of surgical stitches and/or to the change in distensibility between artery and vein graft, on the haemodynamics in the lumen and, subsequently, on NIH progression. The model enabled to simulate NIH at proximal and distal anastomoses of three patient-specific end-to-side saphenous vein grafts under two compliance-mismatch configurations, and a rigid wall case for comparison, obtaining values of stenosis similar to those observed in the computed tomography (CT) scans. The maximum difference in time-averaged wall shear stress between the rigid and compliant models was 3.4 Pa, and differences in estimation of NIH progression were only observed in one patient. The impact of compliance on the haemodynamic-driven development of NIH was small in the patient-specific cases considered.

Respiratory- and cardiac-triggered three-dimensional sheath inked rapid acquisition with refocused echoes imaging (SHINKEI) of the abdomen for magnetic resonance neurography of the celiac plexus

The visualisation of the celiac plexus using respiratory- and cardiac-triggered three-dimensional (3D) sheath inked rapid acquisition with refocused echoes imaging (SHINKEI) was evaluated. After ethical approval and written informed consent, eight volunteers (age 27 ± 5 years, mean ± standard deviation) were scanned at 1.5 and 3 T. Displacement of the celiac ganglia due to aortic pulsatility was studied on axial single-slice breath-hold balanced turbo field-echo cine sequences in five volunteers and found to be 3.0 ± 0.5 mm (left) and 3.1 ± 0.4 mm (right). Respiratory- and cardiac-triggered 3D SHINKEI images were compared to respiratory- and cardiac-triggered fat-suppressed 3D T2-weighted turbo spin-echo and respiratory-triggered 3D SHINKEI in all volunteers. Visibility of the celiac ganglia was rated by three radiologists as visible or non-visible. On 3D SHINKEI with double-triggering at 1.5 T, the left and right ganglia were seen by all observers in 7/8 and 8/8 volunteers, respectively. At 3 T, this was the case for 6/8 and 7/8 volunteers, respectively. The nerve-to-muscle signal ratio increased from 1.9 ± 0.5 on fat-suppressed 3D T2-weighted turbo spin-echo to 4.7 ± 0.8 with 3D SHINKEI. Anatomical validation was performed in a human cadaver. An expert in anatomy confirmed that the hyperintense structure visible on ex vivo 3D SHINKEI scans was the celiac plexus. In conclusion, double-triggering allowed visualisation of the celiac plexus using 3D SHINKEI at both 1.5 T and 3 T.

Quantitative Aortic Distensibility Measurement Using CT in Patients with Abdominal Aortic Aneurysm: Reproducibility and Clinical Relevance

Purpose. To investigate the reproducibility of aortic distensibility (D) measurement using CT and assess its clinical relevance in patients with infrarenal abdominal aortic aneurysm (AAA). Methods. 54 patients with infrarenal abdominal aortic aneurysm were studied to determine their distensibility by using 64-MDCT. Aortic cross-sectional area changes were determined at two positions of the aorta, immediately below the lowest renal artery (level 1.) and at the level of its maximal diameter (level 2.) by semiautomatic segmentation. Measurement reproducibility was assessed using intraclass correlation coefficient (ICC) and Bland-Altman analyses. Stepwise multiple regression analysis was performed to assess linear associations between aortic D and anthropometric and biochemical parameters. Results. A mean distensibility of D_{level  1.} = (1.05 ± 0.22) × 10⁻⁵  Pa⁻¹ and D_{level  2.} = (0.49 ± 0.18) × 10⁻⁵  Pa⁻¹ was found. ICC proved excellent consistency between readers over two locations: 0.92 for intraobserver and 0.89 for interobserver difference in level 1. and 0.85 and 0.79 in level 2. Multivariate analysis of all these variables showed sac distensibility to be independently related (R² = 0.68) to BMI, diastolic blood pressure, and AAA diameter. Conclusions. Aortic distensibility measurement in patients with AAA demonstrated high inter- and intraobserver agreement and may be valuable when choosing the optimal dimensions graft for AAA before endovascular aneurysm repair.

Associations Between Cardio–Ankle Vascular Index and Aortic Structure and Sclerosis Using Multidetector Computed Tomography

Aortic pulse wave velocity (PWV) has been accepted as the gold standard for arterial stiffness measurement. However, PWV depends on blood pressure (BP). To eliminate the BP dependency of PWV, the cardio–ankle vascular index (CAVI) was developed. This study aimed to define the relationship between CAVI and aortic atherosclerosis or structure on multidetector computed tomography (MDCT). Patients with (n = 49) or without (n = 49) coronary artery disease were studied. The lumen and vessel diameters and wall thickness were calculated from the cross-sectional area at the pulmonary bifurcation level by 64-slice MDCT. The CAVI was measured within 3 days before MDCT. Multivariate analysis showed that the vessel diameter of the ascending and descending aorta on MDCT depends on age, body surface area, and diastolic BP. The CAVI significantly correlated with the vessel diameter ( r = .453) and wall thickness ( r = .387) of the thoracic descending aorta ( P < .001, respectively). The CAVI was an independent predictor of the descending aortic wall thickness on multiple stepwise regression analysis. These data suggest that CAVI, a simple index, is useful for evaluating thoracic aortic atherosclerosis.

Association of Aortic Diameters with Coronary Artery Disease Severity and Albumin Excretion

Introduction. Aortic diameters, aortic distensibility, microalbuminuria, coronary artery disease which are all together related to vascular aging are investigated in this paper. Methods. Eighty consecutive nondiabetic patients undergoing elective coronary angiography were enrolled into the study. Systolic and diastolic aortic diameters, aortic distensibility, CAD severity by angiogram with the use of Gensini scoring, and albumin excretion rates were determined. Results. Cases with CAD had significantly larger systolic (30,72 ± 3,21 mm versus 34,19 ± 4,03 mm for cases without and with CAD, resp.) and diastolic aortic diameters measured 3 cm above aortic valve compared to patients without CAD (33,56 ± 4,07 mm versus 29,75 ± 3,12 mm). The systolic and diastolic diameters were significantly higher in albuminuria positive patients compared to albuminuria negative patients (p = 0.017 and 0.008, resp., for systolic and diastolic diameters). Conclusion. In conclusion aortic diameters are increased in patients with coronary artery disease and in patients with microalbuminuria. In CAD patients, systolic blood pressure, pulse pressure, aortic systolic and diastolic pressure, and albumin excretion rate were higher and aortic distensibility was lower.

Central aortic reservoir-wave analysis improves prediction of cardiovascular events in elderly hypertensives

Several morphological parameters based on the central aortic pressure waveform are proposed as cardiovascular risk markers, yet no study has definitively demonstrated the incremental value of any waveform parameter in addition to currently accepted biomarkers in elderly, hypertensive patients. The reservoir-wave concept combines elements of wave transmission and Windkessel models of arterial pressure generation, defining an excess pressure superimposed on a background reservoir pressure. The utility of pressure rate constants derived from reservoir-wave analysis in prediction of cardiovascular events is unknown. Carotid blood pressure waveforms were measured prerandomization in a subset of 838 patients in the Second Australian National Blood Pressure Study. Reservoir-wave analysis was performed and indices of arterial function, including the systolic and diastolic rate constants, were derived. Survival analysis was performed to determine the association between reservoir-wave parameters and cardiovascular events. The incremental utility of reservoir-wave parameters in addition to the Framingham Risk Score was assessed. Baseline values of the systolic rate constant were independently predictive of clinical outcome (hazard ratio, 0.33; 95% confidence interval, 0.13-0.82; P=0.016 for fatal and nonfatal stroke and myocardial infarction and hazard ratio, 0.38; 95% confidence interval, 0.20-0.74; P=0.004 for the composite end point, including all cardiovascular events). Addition of this parameter to the Framingham Risk Score was associated with an improvement in predictive accuracy for cardiovascular events as assessed by the integrated discrimination improvement and net reclassification improvement indices. This analysis demonstrates that baseline values of the systolic rate constant predict clinical outcomes in elderly patients with hypertension and incrementally improve prognostication of cardiovascular events.

The ascending aortic elasticity feature in normotensive subjects: evaluation with coronary CT angiography

To evaluate the ascending aortic elasticity feature, 118 normotensive subjects who underwent coronary computed tomography angiography (CCTA) were enrolled. Two groups of parameters assessing elasticity were calculated based on the measurements of volume and area of ascending aorta. Multivariate analysis revealed that some factors including age, systolic BP, diastolic BP, heart rate, smoking status and hyperlipidemia independently related to decreased aortic elasticity. Both measuring methods are applicable for evaluation of aortic elasticity. As the prevalence of CCTA, it is meaningful that CCTA can provide not only the structural details of ascending aorta but also functional information of the vessel elasticity.

Advancements in identifying biomechanical determinants for abdominal aortic aneurysm rupture

Abdominal aortic aneurysms are a common health problem and currently the need for surgical intervention is determined based on maximum diameter and growth rate criteria. Since these universal variables often fail to predict accurately every abdominal aortic aneurysms evolution, there is a considerable effort in the literature for other markers to be identified towards individualized rupture risk estimations and growth rate predictions. To this effort, biomechanical tools have been extensively used since abdominal aortic aneurysm rupture is in fact a material failure of the diseased arterial wall to compensate the stress acting on it. The peak wall stress, the role of the unique geometry of every individual abdominal aortic aneurysm as well as the mechanical properties and the local strength of the degenerated aneurysmal wall, all confer to rupture risk. In this review article, the assessment of these variables through mechanical testing, advanced imaging and computational modeling is reviewed and the clinical perspective is discussed.

The combined effect of hypertension and type 2 diabetes mellitus on aortic stiffness and endothelial dysfunction: an integrated study with high-resolution MRI

PURPOSE

The purpose of this study was to investigate the combined effect of hypertension and type 2 diabetes mellitus (DM2) on aortic stiffness and endothelial dysfunction by using an integrated MRI approach.

MATERIALS AND METHODS

A total of 31 non-hypertensive DM2 patients and 31 hypertensive DM2 patients underwent 3.0-T MRI. Aortic distensibility (AD), pulse wave velocity (PWV) and brachial artery flow-mediated dilation (FMD) were assessed. Student's t-test, Mann-Whitney U test, chi-squared test, Pearson correlation analysis, and univariable and multiple linear regression analyses were used for statistical analyses.

RESULTS

The hypertensive patients showed lower AD at multiple levels (ascending aorta [AA]: 2.07±0.98×10(-3)mm Hg(-1) vs. 3.21±1.70×10(-3)mm Hg(-1), p<0.01; proximal thoracic descending aorta [PDA]: 2.58±0.72×10(-3)mm Hg(-1) vs. 3.58±1.47×10(-3)mm Hg(-1), p<0.01; distal descending aorta [DDA]: 3.11±1.84×10(-3)mm Hg(-1) vs. 4.27±1.75×10(-3)mm Hg(-1), p<0.01); faster PWV (7.46±2.28m/s vs. 5.82±1.12m/s, p<0.05) and lower FMD (12.67%±6.49% vs. 20.66%±9.7%; p<0.01). Systolic blood pressure was an independent predictor of PWV, AA-AD, DDA-AD and FMD. FMD was statistically significantly associated with PWV (r=-0.37, p<0.01) and AD (p<0.01).

CONCLUSIONS

Hypertension has a contributive effect on aortic stiffness and endothelial dysfunction in DM2 patients.

Influence of Cardiovascular Risk Factors on Aortic Wall Motion After Repair of Type A Aortic Dissection: An Electrocardiography-Gated Computed Tomography Study

BACKGROUND

We aimed to evaluate size changes of the thoracic aorta during the cardiac cycle with dynamic computed tomographic angiography (CTA) at specific anatomic landmarks in patients who previously underwent ascending aorta repair because of type A dissection, and to correlate aortic wall motion with several cardiovascular risk factors.

METHODS

From December 2008 to December 2010, 18 patients (14 men and 4 women, mean age 64 ± 12 years) with previous aortic repair underwent electrocardiography-gated CTA follow-up. Aortic systolic and diastolic diameter and cross-sectional area were measured at 4 levels: 1 cm proximal (level A) and 1 (B), 3 (C), and 10 cm (D) distal to the origin of the left subclavian artery. RESULTS were assessed according to age and presence of diabetes, hypertension, and smoking.

RESULTS

This morpho-functional evaluation of aortic wall motion demonstrated a significant influence (P < 0.05) of hypertension at level A and D and diabetes at level D. Smoking had a borderline significance at level C and D. No significant correlation with age was evident, with results not significantly different in patients ≤ 55 and > 55 years.

CONCLUSIONS

Smoking, diabetes, and hypertension play a role in impairing aortic size variations. These variations might predict wall structural alterations due to cardiovascular risk factors before they become morphologically evident. This might influence timing of surveillance following repair of acute dissection, allowing it to be specifically tailored for any single subject.

Age-dependent ascending aorta mechanics assessed through multiphase CT

Quantification of the age- and gender-specific in vivo mechanical characteristics of the ascending aorta (AA) will allow for identification of abnormalities aside from changes brought on by aging alone. Multiphase clinical CT scans of 45 male patients between the ages of 30 and 79 years were analyzed to assess age-dependent in vivo AA characteristics. The three-dimensional AA geometry for each patient was reconstructed from the CT scans for 9-10 phases throughout the cardiac cycle. The AA circumference was measured during each phase and was used to determine the corresponding diameter, circumferential strain, and wall tension at each phase. The pressure-strain modulus was also determined for each patient. The mean diastolic AA diameter was significantly smaller among young (42.6 ± 5.2 years) at 29.9 ± 2.8 mm than old patients (69.0 ± 5.2 years) at 33.2 ± 3.2 mm. The circumferential AA strain from end-diastole to peak-systole decreased from 0.092 ± 0.03 in young to 0.056 ± 0.03 in old patients. The pressure-strain modulus increased two-fold from 68.4 ± 30.5 kPa in young to 162.0 ± 93.5 kPa in old patients, and the systolic AA wall tension increased from 268.5 ± 31.3 kPa in young to 304.9 ± 49.2 kPa in old patients. The AA dilates and stiffens with aging which increases the vessel wall tension, likely predisposing aneurysm and dissection.

Estimation of wall properties and wall strength of aortic aneurysms using modern imaging techniques. One more step towards a patient-specific assessment of aneurysm rupture risk

Abdominal aortic aneurysmal disease is a major health problem with rupture representing its main complication accompanied by great mortality. Elective repair is currently performed with mortality rates <3%, based upon size or expansion rate, with a recommended threshold of 5.5 cm maximum diameter or >1cm/year enlargement. It is well established that even small AAAs without indication for surgical repair can experience rupture with catastrophic outcomes whereas larger aneurysms often remain intact for a long period. It is recognized, therefore, that the currently used, maximum diameter criterion can not accurately predict AAAs evolution. There is increasing interest in the role of patient-specific biomechanical profiling of AAA development and rupture. Biomechanically, rupture of a vessel occurs when intravascular forces exceed vessel wall structural endurance. Peak Wall Stress (PWS) has been previously shown to better identify AAAs prone to rupture than maximum diameter, but currently stress analysis takes into account several assumptions that influence results to a large extent and limit their use. Moreover stress represents only one of two determinants of rupture risk according to the biomechanical perspective. Wall strength and mechanical properties on the other hand cannot be assessed in vivo but only ex vivo through mechanical studies with mean values of these parameters taken into account for rupture risk estimations. New possibilities in the field of aortic imaging offer promising tools for the validation and advancement of stress analysis and the in vivo evaluation of AAAs' wall properties and wall strength. Documentation of aortic wall motion during cardiac cycle is now feasible through ECG-gated multi-detector CT imaging offering new possibilities towards an individualized method for rupture risk and expansion-rate predictions based on data acquired in vivo.

Progression of arterial stiffness and coronary atherosclerosis: longitudinal evaluation by cardiac CT

OBJECTIVE

We sought to use cardiac CT angiography (CTA) to longitudinally examine the relationship between changes in aortic stiffness and of the atherosclerotic burden over time.

MATERIALS AND METHODS

One hundred sixty-four patients with suspected coronary artery disease underwent two retrospectively ECG-gated cardiac CTA studies an average of 12 ± 10 months apart. Arterial stiffness was represented by the aortic distensibility index (ADI) and atherosclerosis by segment involvement score (SIS) (defined as the number of coronary artery segments per patient displaying atherosclerotic plaque). Changes in ADI and SIS between the studies were compared using linear and logistic regression accounting for differences in clinical and demographic baseline characteristics.

RESULTS

Age (p = 0.004), time between studies (p = 0.02), and increase in SIS (p < 0.001) were associated with a decrease in ADI on univariate analysis. Increase in SIS remained a significant independent predictor of decreased ADI on both multivariate logistic regression (with change in ADI represented categorically) and multivariate linear regression (both p < 0.001).

CONCLUSION

On longitudinal evaluation with cardiac CTA, the progression of aortic stiffness is associated with the progression of coronary atherosclerosis. Although outcome studies are needed, a comprehensive assessment of vascular health with cardiac CTA, including both indexes of arterial stiffness and atherosclerotic burden, may improve risk stratification and therapy monitoring.

Aortic distensibility and its relationship to coronary and thoracic atherosclerosis plaque and morphology by MDCT: insights from the ROMICAT Trial

BACKGROUND

Multi-detector cardiac computed tomography (CT) allows for simultaneous assessment of aortic distensibility (AD), coronary atherosclerosis, and thoracic aortic atherosclerosis.

OBJECTIVES

We sought to determine the relationship of AD to the presence and morphological features in coronary and thoracic atherosclerosis.

METHODS

In 293 patients (53 ± 12 years, 63% male), retrospectively-gated MDCT were performed. We measured intraluminal aortic areas across 10 phases of the cardiac cycle (multiphase reformation 10% increments) at pre-defined locations to calculate the ascending, descending, and local AD (at locations of thoracic plaque). AD was calculated as maximum change in area/(minimum area × pulse pressure). Coronary and thoracic plaques were categorized as calcified, mixed, or non-calcified.

RESULTS

Ascending and descending AD were lower in patients with any coronary plaque, calcified or mixed plaque than those without (all p<0.0001) but not with non-calcified coronary plaque (p ≥ 0.46). Per 1mm Hg(-1) 10(-3) increase in ascending and descending AD, there was an 18-29% adjusted risk reduction for having any coronary, calcified plaque, or mixed coronary plaque (ascending AD only) (all p ≤ 0.04). AD was not associated with non-calcified coronary plaque or when age was added to the models (all p>0.39). Local AD was lower at locations of calcified and mixed thoracic plaque when compared to non-calcified thoracic atherosclerosis (p<0.04).

CONCLUSIONS

A stiffer, less distensible aorta is associated with coronary and thoracic atherosclerosis, particularly in the presence of calcified and mixed plaques, suggesting that the mechanism of atherosclerosis in small and large vessels is similar and influenced by advancing age.

Circumferential and longitudinal cyclic strain of the human thoracic aorta: age-related changes

OBJECTIVE

We developed a novel method using anatomic markers along the thoracic aorta to accurately quantify longitudinal and circumferential cyclic strain in nondiseased thoracic aortas during the cardiac cycle and to compute age-related changes of the human thoracic aorta.

METHODS

Changes in thoracic aorta cyclic strains were quantified using cardiac-gated computed tomography image data of 14 patients (aged 35 to 80 years) with no visible aortic pathology (aneurysms or dissection). We measured the diameter and circumferential cyclic strain in the arch and descending thoracic aorta (DTA), the longitudinal cyclic strain along the DTA, and changes in arch length and motion of the ascending aorta relative to the DTA. Diameters were computed distal to the left coronary artery, proximal and distal to the brachiocephalic trunk, and distal to the left common carotid, left subclavian, and the first and seventh intercostal arteries. Cyclic strains were computed using the Green-Lagrange strain tensor. Arch length was defined along the vessel centerline from the left coronary artery to the first intercostal artery. The length of the DTA was defined along the vessel centerline from the first to seventh intercostal artery. Longitudinal cyclic strain was quantified as the difference between the systolic and diastolic DTA lengths divided by the diastolic DTA length. Comparisons were made between seven younger (age, 41 +/- 7 years; 5 men) and seven older (age, 68 +/- 6 years; 5 men) patients.

RESULTS

The average increase of diameters of the thoracic aorta was 14% with age from the younger to the older (mean age, 41 vs 68 years) group. The average circumferential cyclic strain of the thoracic aorta decreased by 55% with age from the younger to the older group. The longitudinal cyclic strain decreased with age by 50% from the younger to older group (2.0% +/- 0.4% vs 1.0% +/- 1%, P = .03). The arch length increased by 14% with age from the younger to the older group (134 +/- 17 mm vs 152 +/- 10 mm, P = .03).

CONCLUSIONS

The thoracic aorta enlarges circumferentially and axially and deforms significantly less in the circumferential and longitudinal directions with increasing age. To our knowledge, this is the first quantitative description of in vivo longitudinal cyclic strain and length changes for the human thoracic aorta, creating a foundation for standards in reporting data related to in vivo deformation and may have significant implications in endoaortic device design, testing, and stability.

Heartbeat-related displacement of the thoracic aorta in patients with chronic aortic dissection type B: quantification by dynamic CTA

PURPOSE

The purpose of this study was to characterize the heartbeat-related displacement of the thoracic aorta in patients with chronic aortic dissection type B (CADB).

MATERIALS AND METHODS

Electrocardiogram-gated computed tomography angiography was performed during inspiratory breath-hold in 11 patients with CADB: Collimation 16 mm x 1 mm, pitch 0.2, slice thickness 1mm, reconstruction increment 0.8 mm. Multiplanar reformations were taken for 20 equidistant time instances through both ascending (AAo) and descending aorta (true lumen, DAoT; false lumen, DAoF) and the vertex of the aortic arch (VA). In-plane vessel displacement was determined by region of interest analysis.

RESULTS

Mean displacement was 5.2+/-1.7 mm (AAo), 1.6+/-1.0 mm (VA), 0.9+/-0.4 mm (DAoT), and 1.1+/-0.4mm (DAoF). This indicated a significant reduction of displacement from AAo to VA and DAoT (p<0.05). The direction of displacement was anterior for AAo and cranial for VA.

CONCLUSION

In CADB, the thoracic aorta undergoes a heartbeat-related displacement that exhibits an unbalanced distribution of magnitude and direction along the thoracic vessel course. Since consecutive traction forces on the aortic wall have to be assumed, these observations may have implications on pathogenesis of and treatment strategies for CADB.