Thoracic and abdominal aortic diameters in a general population: MRI-based reference values and association with age and cardiovascular risk factors

Measuring early vascular aging in youth: an expert consensus document from the Youth Vascular Consortium

Since the conceptualization of early vascular aging (EVA) in 2008, significant efforts have been made to develop and improve its assessment. Initially lead by the investigation of arterial stiffness through pulse wave velocity (PWV), several additional vascular aging biomarkers have gained prominence in recent years. Despite expanding literature addressing methodological concerns associated with these biomarkers in youth, a standardized approach for clinical evaluation of EVA remains elusive, leaving pertinent gaps in understanding the optimal methodology. This article, resulting from international consensus efforts from the Youth Vascular Consortium, aims to provide an updated overview of methods available to measure EVA in youth and to discuss challenges in translating these methods into clinical practice.

Variations in stiffness and structure of the human aorta along its length

This study investigates the regional mechanical, structural, and morphological properties of the human aorta using fresh tissues from 10 middle-aged and elderly donors (62 ± 11 years old, 30% female). Four locations were analyzed: descending thoracic aorta (TA), supraceliac aorta (SC), infrarenal aorta (IFR), and distal abdominal aorta (dAA). Planar biaxial testing revealed location-specific stiffness, with distal regions exhibiting significantly reduced stretch at physiological stress levels. At 75 kPa, the circumferential stretch decreased from 1.24 in the TA to 1.12 in the dAA, while longitudinal stretch declined from 1.18 to 1.12. Elastin density in the medial layer showed a marked reduction, decreasing from 23.5% in the TA to 8.9% in the dAA, accompanied by thinning and fragmentation of elastic lamellae distally. Glycosaminoglycans were primarily localized near the intima and exhibited a consistent density (~ 5-6%) across all locations. Morphometric analysis revealed a progressive decrease in wall thickness in load-free conditions from 3.10 mm in the TA to 2.77 mm in the dAA, while stress-free configurations highlighted greater residual stresses in distal segments. Constitutive modeling using four common constitutive relations, including a four-fiber family model, provided parameters for computational simulations, with the four-fiber model offering the best fit. These findings provide quantitative insights into location-specific variations in the human aorta, advancing our understanding of its biomechanical and structural heterogeneity and informing computational models and therapeutic approaches.

Association of aortic diameters and mortality in the general population-an MRI-based study

BACKGROUND

Increased diameters of the aorta are associated with increased mortality risk. In the present analyses, we assessed whether aortic diameters are associated with cardiovascular and all-cause mortality in community-dwelling individuals free of known cardiovascular disease (CVD).

METHODS

MRI-derived vascular parameters of the thoracic and abdominal aorta from 2668 participants (median age = 53 years; 51.1% women) of the population-based SHIP-START-2 and SHIP-TREND-0 cohorts without CVD were analyzed. Age- and sex-adjusted, as well as multivariable-adjusted Cox-proportional hazard models, were used to estimate associations of diameters of six different aortic segments to mortality.

RESULTS

Over a median follow-up time of 10.6 years (IQR: 8.7; 12.4), a total of 188 participants (126 men and 62 women) died, of which 38 deaths were due to CVD. In unadjusted models, mortality rates were higher in participants with aortic diameters above the median compared to below the median for all investigated aortic sections (all log-rank p < 0.001). In multivariable-adjusted models, the diameters of the ascending thoracic aorta (HR = 1.34 95% CI: 1.04; 1.72, p = 0.022) and of the infrarenal aorta (HR = 3.75 95% CI: 1.06; 13.3, p = 0.040), modeled continuously, were associated with greater cardiovascular mortality. The diameter of the subphrenic aorta was associated with higher cardiovascular mortality only in the age and sex-adjusted model (HR = 3.65 95% CI: 1.01; 13.3, p = 0.049). None of the investigated aortic segments were associated with all-cause mortality.

CONCLUSION

Non-indexed diameters of the ascending thoracic and infrarenal aorta were associated with higher cardiovascular mortality but not with all-cause mortality in a population sample free of clinically overt CVD at baseline.

CLINICAL RELEVANCE STATEMENT

Increased aortic diameter is associated with cardiovascular mortality and can help to identify high-risk patients.

KEY POINTS

Increased aortic diameter is associated with mortality. Non-indexed diameters of the ascending and infrarenal aorta are associated with cardiovascular mortality but not all-cause mortality. Aortic diameter measurements support the estimate of cardiovascular mortality.

Effect of a reduced arterial axial pre-stretch ratio during aging on the cardiac output and cerebral blood flow in the healthy elders

BACKGROUND AND OBJECTIVE

It is an indisputable physiological phenomenon that the arterial axial pre-stretch ratio (AAPSR) decreases with age, but little attention has been paid to the effect of this reduction on chronic diseases during aging.

METHODS

Here we reported an experimental method to simulate arteries aging, developed a fluid-structure interaction model with the effect of AAPSR changes, and compared it with the anatomy data and structural parameters of the human thoracic aorta.

RESULTS

We showed that with the process of aging, the decrease of AAPSR leads to a decline of arterial elasticity, a decrease of arterial elastic strain energy, which weakens the ability to promote blood circulation, the corresponding decrease in cardiac output (CO) and cerebral blood flow (CBF) causes distal organ and body tissue ischemia, which is one of the main causes of increased blood pressure and decreased cerebral perfusion in the elderly.

CONCLUSIONS

Thus, reduced AAPSR is the one of main manifestation of arteries aging and has an important impact on hypertension and hypoperfusion of the brain in the process of human aging. The research contributes to a better understanding of the physiological and pathological mechanisms of aging-related diseases.

Quantitative analysis of systemic perfusion and cerebral blood flow in the modeling of aging and orthostatic hypotension

Introduction: Orthostatic hypotension (OH) is common among the older population. The mechanism hypothesized by OH as a risk factor for cognitive decline and dementia is repeated transient cerebral blood flow deficiency. However, to our knowledge, quantitative evaluation of cardiac output and cerebral blood flow due to acute blood pressure changes resulting from postural changes is rare. Methods: We report a new fluid-structure interaction model to analyze the quantitative relationship of cerebral blood flow during OH episodes. A device was designed to simulate the aging of blood vessels. Results and Discussion: The results showed that OH was associated with decreased transient cerebral blood flow. With the arterial aging, lesions, the reduction in cerebral blood flow is accelerated. These findings suggest that systolic blood pressure regulation is more strongly associated with cerebral blood flow than diastolic blood pressure, and that more severe OH carries a greater risk of dementia. The model containing multiple risk factors could apply to analyze and predict for individual patients. This study could explain the hypothesis that transient cerebral blood flow deficiency in recurrent OH is associated with cognitive decline and dementia.

Relationship between low relative muscle mass and aortic regional morphological changes in adults underwent contrast CT scans for cancer diagnostics

OBJECTIVES

Low muscle mass is related to cardiovascular risk factors. This study aimed to investigate whether relative low muscle mass is related to the diameter and tortuosity of the aorta.

METHODS

We performed a cross-sectional study of 208 adults without known cardiovascular disease who underwent Computed Tomography (CT) enhanced scan between 2020 and 2021. Skeletal muscle index (SMI) was estimated. The morphology of the aorta was measured by diameter and tortuosity using CT. We assessed the relationship between SMI and diameter and tortuosity of the aorta using Spearman correlation analysis and univariate and multivariate-adjusted regression models.

RESULTS

Of all -individuals, 124 (59.6%) were male. The average age was 60.13 ± 16.33 years old. SMI was inversely associated with the diameter and tortuosity of the aorta (p < 0.05). Specifically, in a multivariable-adjusted model adjusting for potential confounders, a one-unit increase in the SMI was associated with a -13.56mm(95% confidence intervals (CI): -18.16 to -8.96, p < 0.001), -7.93 mm (95% CI: -10.85 to -5.02, p < 0.001), -8.01 mm (95% CI: -11.30 to -4.73, p < 0.001), -5.16 mm (95% CI: -7.57 to -2.75, p < 0.001) and -2.73 mm (95% CI: -5.18 to -0.27, p = 0.031) increase in L1-L5 diameter respectively, a -0.89 (95% CI: -1.14 to -0.64, p < 0.001) increase in the aorta tortuosity, a -0.48 (95% CI: -0.59 to -0.36, p < 0.001) increase in the descending thoracic aorta tortuosity, and a -0.44 (95% CI: -0.52 to -0.35, p < 0.001) increase in the abdominal aorta tortuosity.

CONCLUSIONS

Relative muscle mass was negatively associated with the diameter and tortuosity of the aorta, suggesting muscle mass maintenance may play a role in preventing aortic morphological changes.

A Ratio Between Infrarenal and Suprarenal Aortic Diameters Corrects for Absolute Aortic Diameter Variations due to Patients' Sex and Body Size

OBJECTIVES

Aortic diameters may differ significantly between patients with different gender and body size. The aim of this study was to relate absolute aortic diameters to age, sex, height, and weight of the patients and to correct for these factors by calculating the ratio between the infrarenal and the suprarenal aortic diameters.

METHODS

A total of 458 patients who underwent elective endovascular aneurysm repair (EVAR) between 2004 and 2018 were included. The aortic anatomy in this group of elective EVAR patients was compared with a control group of 75 patients without an abdominal aortic aneurysm (AAA). The aortic diameter was measured at 4 suprarenal points and 4 infrarenal points. Ratios were calculated by dividing the mean infrarenal neck diameter by 4 suprarenal measurements.

RESULTS

Patients in the aneurysm group had significantly larger suprarenal and infrarenal aortic diameters. The ratios between the mean infrarenal neck diameter and all 4 suprarenal measurements were larger in the AAA group than in the control group. In both groups, there was a significant correlation between the mean infrarenal neck diameter and sex, height, weight, and body surface area (BSA). However, in both groups, all 4 ratios between the mean infrarenal neck diameter and suprarenal aortic diameters were not correlated with age, sex, height, weight, or BSA, except for the ratio between the mean infrarenal neck diameter and the aortic diameter measurement proximal to the upper renal artery, which was correlated to weight and BSA in the control group.

CONCLUSION

The mean infrarenal neck diameter is correlated with sex, height, weight, and BSA. However, when the suprarenal aortic diameter was used as an internal control for the mean infrarenal neck diameter, we were able to correct for these variations in aortic diameters due to sex and body size. The clinical relevance of this ratio in patients treated by EVAR has yet to be assessed in future research.

CLINICAL IMPACT

In the assessment for EVAR suitability the absolute diameter of the aneurysm neck is taken into account. We believe that using absolute diameters is not the appropriate way to assess this suitability, but that patient characteristics such as age, gender and body size, should be factored into this assessment. In this paper, we show that suprarenal and infrarenal aortic diameters are both significantly increased in patients with an aneurysm compared with patients without an aneurysm. Besides, we found that mean infrarenal aortic diameter is correlated with sex, height, weight, and body surface area. Finally, we propose a new ratio system, using suprarenal diameters as an internal control, to correct for aortic diameter variations due to sex and body size.

Reference values of normal abdominal aortic areas in Chinese population measured by contrast-enhanced computed tomography

Objective

To generate reference values of the normal areas of the abdominal aorta at various levels among Chinese people and to explore the factors that may promote the expansion of the abdominal aorta.

Methods

The areas of normal abdominal aortas were gauged at various levels based on inner-to-inner measurements in 1,066 Chinese adult patients (&gt;18 years) without the abdominal aortic disease. The areas of subphrenic abdominal, suprarenal abdominal, infrarenal abdominal, and distal abdominal aortas were measured. The demographic and clinical characteristics were collected into a specifically designed electronic database. Multivariable linear regression was used to analyze the potential risk factors promoting the expansion of the abdominal aorta.

Results

In males, the median areas of the subphrenic abdominal aorta, suprarenal abdominal aorta, infrarenal abdominal aorta, and distal abdominal aorta were 412.1, 308.0, 242.2, and 202.2 mm2, respectively. In females, the median areas of the subphrenic abdominal aorta, suprarenal abdominal aorta, infrarenal abdominal aorta, and distal abdominal aorta were 327.7, 243.4, 185.4, and 159.6 mm2, respectively. The areas of the abdominal aorta at different levels were larger in males than in females and increased with age. Multiple linear stepwise regression analysis showed that the subphrenic abdominal aortic area was significantly related to age (β = 0.544, p &lt; 0.001), sex (β = 0.359, p &lt; 0.001), and hypertension (β = 0.107, p &lt; 0.001). Suprarenal abdominal aortic area was related to age (β = 0.398, p &lt; 0.001), sex (β = 0.383, p &lt; 0.001), history of smoking (β = 0.074, p = 0.005), and hypertension (β = 0.111, p &lt; 0.001). The infrarenal abdominal aortic area was correlated with age (β = 0.420, p &lt; 0.001), sex (β = 0.407, p &lt; 0.001), and history of smoking (β = 0.055, p = 0.036). The distal abdominal aortic area was correlated with age (β = 0.463, p &lt; 0.001), sex (β = 0.253, p &lt; 0.001), and hypertension (β = 0.073, p = 0.013).

Conclusion

The abdominal aortic areas at different levels were larger in males than in females. Aging, hypertension, and smoking prompt the expansion of abdominal aorta.

A fluid-structure interaction model accounting arterial vessels as a key part of the blood-flow engine for the analysis of cardiovascular diseases

According to the classical Windkessel model, the heart is the only power source for blood flow, while the arterial system is assumed to be an elastic chamber that acts as a channel and buffer for blood circulation. In this paper we show that in addition to the power provided by the heart for blood circulation, strain energy stored in deformed arterial vessels in vivo can be transformed into mechanical work to propel blood flow. A quantitative relationship between the strain energy increment and functional (systolic, diastolic, mean and pulse blood pressure) and structural (stiffness, diameter and wall thickness) parameters of the aorta is described. In addition, details of blood flow across the aorta remain unclear due to changes in functional and other physiological parameters. Based on the arterial strain energy and fluid-structure interaction theory, the relationship between physiological parameters and blood supply to organs was studied, and a corresponding mathematical model was developed. The findings provided a new understanding about blood-flow circulation, that is, cardiac output allows blood to enter the aorta at an initial rate, and then strain energy stored in the elastic arteries pushes blood toward distal organs and tissues. Organ blood supply is a key factor in cardio-cerebrovascular diseases (CCVD), which are caused by changes in blood supply in combination with multiple physiological parameters. Also, some physiological parameters are affected by changes in blood supply, and vice versa. The model can explain the pathophysiological mechanisms of chronic diseases such as CCVD and hypertension among others, and the results are in good agreement with epidemiological studies of CCVD.

The Impact of Suprarenal Diameter on Outcomes Following Endovascular Aneurysm Repair: A Retrospective Cohort Study

OBJECTIVES

To determine the association between suprarenal aortic diameters and complications that may be attributed to a dilating phenotype following endovascular abdominal aortic aneurysm repair.

DESIGN

This study is a retrospective review.

METHODS

We measured the abdominal aortas of 147 consecutive patients with a mean age of 78.5 (range 60-93) years, who had a mean Endovascular aneurysm repair (EVAR) follow-up of 3 years (6 months to 8 years) at a public Hospital. Aortic calibres measured 5 mm above the highest renal artery were recorded, patients were categorised according to suprarenal diameter; Group A: greater than 25 mm, Group B: less than or equal to 25 mm. Stent migration, aneurysmal sac growth, presence of an endoleak and its type, occlusion events, rupture, interventions and mortality, as well as clinical history and demographic data were compared between groups.

RESULTS

There was a significantly higher occurrence of stent migration (11% v 0%; P = .01) in patients with larger suprarenal aortas (Group A). The occurrence of any endoleak did not differ between the groups, however, significantly more complications resulting in secondary intervention, excluding occlusions, were noted in Group A (34% vs 17%, P = .04).

CONCLUSIONS

The results from this study suggest that patients with above-average suprarenal diameters (categorised as dilators) may have a higher occurrence of specific complications following EVAR. A more detailed study to establish the association of suprarenal calibre with types of complications following EVAR is warranted.

Potential influencing factors of aortic diameter at specific segments in population with cardiovascular risk

Background

Aortic diameter is a critical parameter for the diagnosis of aortic dilated diseases. Aortic dilation has some common risk factors with cardiovascular diseases. This study aimed to investigate potential influence of traditional cardiovascular risk factors and the measures of subclinical atherosclerosis on aortic diameter of specific segments among adults.

Methods

Four hundred and eight patients with cardiovascular risk factors were prospectively recruited in the observational study. Comprehensive transthoracic M-mode, 2-dimensional Doppler echocardiographic studies were performed using commercial and clinical diagnostic ultrasonography techniques. The aortic dimensions were assessed at different levels: (1) the annulus, (2) the mid-point of the sinuses of Valsalva, (3) the sinotubular junction, (4) the ascending aorta at the level of its largest diameter, (5) the transverse arch (including proximal arch, mid arch, distal arch), (6) the descending aorta posterior to the left atrium, and (7) the abdominal aorta just distal to the origin of the renal arteries. Multivariable linear regression analysis was used for evaluating aortic diameter-related risk factors, including common cardiovascular risk factors, co-morbidities, subclinical atherosclerosis, lipid profile, and hematological parameters.

Results

Significant univariate relations were found between aortic diameter of different levels and most traditional cardiovascular risk factors. Carotid intima-media thickness was significantly correlated with diameter of descending and abdominal aorta. Multivariate linear regression showed potential effects of age, sex, body surface area and some other cardiovascular risk factors on aortic diameter enlargement. Among them, high-density lipoprotein cholesterol had a significantly positive effect on the diameter of ascending and abdominal aorta. Diastolic blood pressure was observed for the positive associations with diameters of five thoracic aortic segments, while systolic blood pressure was only independently related to mid arch diameter.

Conclusion

Aortic segmental diameters were associated with diastolic blood pressure, high-density lipoprotein cholesterol, atherosclerosis diseases and other traditional cardiovascular risk factors, and some determinants still need to be clarified for a better understanding of aortic dilation diseases.

SHIP-MR and Radiology: 12 Years of Whole-Body Magnetic Resonance Imaging in a Single Center

The Study of Health in Pomerania (SHIP), a population-based study from a rural state in northeastern Germany with a relatively poor life expectancy, supplemented its comprehensive examination program in 2008 with whole-body MR imaging at 1.5 T (SHIP-MR). We reviewed more than 100 publications that used the SHIP-MR data and analyzed which sequences already produced fruitful scientific outputs and which manuscripts have been referenced frequently. Upon reviewing the publications about imaging sequences, those that used T1-weighted structured imaging of the brain and a gradient-echo sequence for R2* mapping obtained the highest scientific output; regarding specific body parts examined, most scientific publications focused on MR sequences involving the brain and the (upper) abdomen. We conclude that population-based MR imaging in cohort studies should define more precise goals when allocating imaging time. In addition, quality control measures might include recording the number and impact of published work, preferably on a bi-annual basis and starting 2 years after initiation of the study. Structured teaching courses may enhance the desired output in areas that appear underrepresented.

Association between hepatic fat and subclinical vascular disease burden in the general population

OBJECTIVE

It is still controversial if increased hepatic fat independently contributes to cardiovascular risk. We aimed to assess the association between hepatic fat quantified by MRI and various subclinical vascular disease parameters.

DESIGN

We included two cross-sectional investigations embedded in two independent population-based studies (Study of Health in Pomerania (SHIP): n=1341; Cooperative Health Research in the Region of Augsburg (KORA): n=386). The participants underwent a whole-body MRI examination. Hepatic fat content was quantified by proton-density fat fraction (PDFF). Aortic diameters in both studies and carotid plaque-related parameters in KORA were measured with MRI. In SHIP, carotid intima-media thickness (cIMT) and plaque were assessed by ultrasound. We used (ordered) logistic or linear regression to assess associations between hepatic fat and subclinical vascular disease.

RESULTS

The prevalence of fatty liver disease (FLD) (PDFF >5.6%) was 35% in SHIP and 43% in KORA. In SHIP, hepatic fat was positively associated with ascending (β, 95% CI 0.06 (0.04 to 0.08)), descending (0.05 (0.04 to 0.07)) and infrarenal (0.02 (0.01 to 0.03)) aortic diameters, as well as with higher odds of plaque presence (OR, 95% CI 1.22 (1.05 to 1.42)) and greater cIMT (β, 95% CI 0.01 (0.004 to 0.02)) in the age-adjusted and sex-adjusted model. However, further adjustment for additional cardiometabolic risk factors, particularly body mass index, attenuated these associations. In KORA, no significant associations were found.

CONCLUSIONS

The relation between hepatic fat and subclinical vascular disease was not independent of overall adiposity. Given the close relation of FLD with cardiometabolic risk factors, people with FLD should still be prioritised for cardiovascular disease screening.

Sex-specific normal values and determinants of infrarenal abdominal aortic diameter among non-aneurysmal elderly population

To establish age- and sex-specific distribution of the infrarenal abdominal aortic diameters (IAD) among non-aneurysmal elderly population and to investigate the associations between traditional cardiovascular risk factors and IAD in men and women. We included 4032 participants (mean age 67.2 years; 60.4% women) from the population-based Rotterdam Study, free of cardiovascular disease, who underwent IAD ultrasound assessment between 2009-2014. Linear regression analysis was used to identify determinants of IAD. The medians (inter-quartile range) of absolute IAD and body surface area (BSA)-adjusted IAD were 17.0 (15.0-18.0) mm and 9.3 (8.5-10.2) mm for women and 19.0 (18.0-21.0) mm and 9.4 (8.6-10.3) mm for men, respectively. There was a non-linear relationship between age and IAD. IAD increased steeply with advancing age and up to 70 years. After around 75 years of age, the diameter values reached a plateau. Waist circumference and diastolic blood pressure were associated with larger diameters in both sexes. Body mass index [Effect estimate (95% CI): 0.04 (0.00 to 0.08)], systolic blood pressure [- 0.01(- 0.02 to 0.00)], current smoking [0.35 (0.06 to 0.65)], total cholesterol levels [- 0.21 (- 0.31 to - 0.11)], and lipid-lowering medication [- 0.43 (- 0.67 to - 0.19)] were significantly associated with IAD in women. Sex differences in IAD values diminished after taking BSA into account. The increase in diameters was attenuated after 70 years. Differences were observed in the associations of several cardiovascular risk factors with IAD among men and women.

Assessment of thoracic aorta in different cardiac phases in patients with non-aorta diseases using cardiac CT

The aim was to evaluate the thoracic aorta in different cardiac phases to obtain the correct cardiac phase for measuring the maximum diameter required to predict aortic disease. Cardiac CT was performed on 97 patients for suspected coronary artery disease. The average diameter of ascending (AAD) and descending aorta (DAD) in the plane of pulmonary bifurcation, in the plane of the sinus junction (AAD [STJ] and DAD [STJ]), descending aorta in the plane of the diaphragm (DAD [Dia]), the diameter of the main pulmonary artery (MPAD), distance from the sternum to the spine (S-SD), and distance from the sternum to the ascending aorta (S-AAD) were assessed at 20 different time points in the cardiac cycle. Differences in aortic diameter in different cardiac phases and the correlation between aortic diameter and traditional risk factors were analyzed by the general linear mixed model. The diameter of the thoracic aorta reached the minimum at the phase of 95–0%, and reached the maximum at 30–35%. The maximum values of AAD, AAD (STJ), DAD, DAD (STJ), and DAD (Dia) were 32.51 ± 3.35 mm, 28.86 ± 3.01 mm, 23.46 ± 2.88 mm, 21.85 ± 2.58 mm, and 21.09 ± 2.66 mm, respectively. The maximum values of MPAD/AAD and DAD/AAD (STJ) were 0.8140 ± 0.1029, 0.7623 ± 0.0799, respectively. The diameter of the thoracic aorta varies with the cardiac phase. Analyzing the changes in aortic diameter, which can be done using cardiac CT, could provide a more accurate clinical measurement for predicting aortic disease.

Relationship between the abdominal aortic diameter and carotid atherosclerosis in middle-aged patients without established atherosclerotic cardiovascular diseases

BACKGROUND

The purpose of our research was to study the relationship between the diameter of abdominal aorta (AA) and subclinical atherosclerosis in patients without established atherosclerotic cardiovascular diseases (ASCD) in the absence of pathological enlargement of AA.

METHODS

The study included 136 patients (52.9% male, 47.1% female), median age was 51.0 (45.5; 58.0) years. The maximum diameter of AA was measured in the infrarenal region at a level between the place of origin of the lower renal artery and bifurcation in cross section. Measurement of the anteroposterior diameter of AA was carried out from the outer-to-outer edge (OTO). Also, we determined the Aortic Size Index (ASI) with respect to body surface area (BSA), using the values of BSA obtained by five different formulas validated for use in clinical practice. All patients underwent carotid duplex ultrasound scanning with assessment of degree of carotid stenosis (according to ECST criteria).

RESULTS

An increase in the anteroposterior diameter of AA was directly correlated with maximum stenosis of carotid arteries (r=0.186; P=0.030). According to the results of a logistic regression analysis an increase in the diameter of AA by 1 mm was associated with an increase in the relative risk of carotid stenosis ≥50% by 1.37 times (95% CI: 1.01-1.85; P=0.041) after adjustment. Thus, an increase in diameter of AA of more than 1.75 cm with a sensitivity of 71.4% and a specificity of 73.0% made it possible to predict the presence of stenosis of the carotid arteries ≥50%. An increase in ASI<inf>Boyd</inf> (BSA was calculated using Boyd's formula) of more than 0.84 allowed predicting the presence of stenosis of the carotid arteries ≥50% with a sensitivity of 85.7% and a specificity of 65.6%.

CONCLUSIONS

In middle-aged patients without established ASCD, the diameter of AA and ASI directly correlated with the degree of carotid stenosis (according to ECST criteria). The diameter of AA and ASI demonstrated good sensitivity and specificity for the presence of asymptomatic carotid stenosis of ≥50%.

Quantitative magnetic resonance imaging measures of three-dimensional aortic morphology in healthy aging and hypertension

Automated segmentation of three-dimensional (3D) aortic magnetic resonance imaging (MRI) renders a possible retrospective selection of any location to perform quantification of aortic caliber perpendicular to its centerline and provides regional and global 3D biomarkers such as length, diameter, or volume. However, normative age-related values of such measures are still lacking. The aim of this study was to provide normal values for 3D aortic morphological measures and investigate their changes in aging and hypertension. This was a retrospective study, in which 119 healthy controls (HC: 48 ± 14 years, 61 men) and 82 hypertensive patients (HT: 60 ± 14 years, 43 men) were enrolled. 1.5 and 3 T/3D steady state free precession or spoiled gradient echo were used. Automated 3D aortic segmentation provided aortic length, diameter, volume for the ascending (AAo), and descending aorta (DAo), along with cross-sectional diameters at three aortic landmarks. Age, sex, body surface area (BSA), smoking, and blood pressures were recorded. Both groups were divided into two subgroups (≤50 years, >50 years). Statistical tests performed were linear regression for age-related normal values and confidence intervals, Wilcoxon rank sum test for differences between groups (HC or HT), and multivariate analysis to identify main determinants of aortic morphological changes. In HC, linear regression revealed an increase in the AAo (respectively DAo) length by 2.84 mm (7.78 mm), maximal diameter by 1.36 mm (1.29 mm), and volume by 4.28 ml (8.71 ml) per decade. AAo morphological measures were higher in HT patients than in HC both ≤50 years but did not reach statistical significance (length: +2 mm, p = 0.531; diameter: +1.4 mm, p = 0.2936; volume:+6.8 ml, p = 0.1857). However, length (+6 mm, p = 0.003), maximal diameter (+4 mm, p < 0.001) and volume (+12 ml, p < 0.001) were significantly higher in HT patients than in HC, both >50 years. In a multivariate analysis, age, sex, and BSA were the major determinants of aortic morphology, irrespective of the presence of hypertension. Global and segmental aortic length, volume, and diameters at specific landmarks were automatically measured from 3D MRI to serve as normative measures of 3D aortic morphology. Such indices increased significantly with age and hypertension among the elderly subjects. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 3.

Effects of obstructive sleep apnea on the thoracic aorta and the main pulmonary artery: assessment by CT

STUDY OBJECTIVES

The influence of obstructive sleep apnea (OSA) on thoracic aortic size is debated. We aimed to identify possible relations between sleep parameters and the sizes of the ascending aorta (AA), the descending thoracic aorta (DTA), and the main pulmonary artery (MPA) in patients with untreated OSA and in a subgroup of participants without comorbidities capable of affecting the size of great thoracic vessels.

METHODS

We retrospectively measured AA, DTA, and MPA sizes on the chest computed tomography scans of 60 patients with OSA who underwent sleep studies within 1 year before or after the computed tomography. Univariate and multivariate analyses were performed on all patient findings, while an additional univariate analysis was conducted on the data for 22 participants without comorbidities. The latter had been divided into subgroups depending on the sleep parameters, and comparisons were made between them.

RESULTS

The logarithm of the time of oxygen saturation below 90% (CT90) significantly predicted AA and MPA sizes in all patients with OSA (P < .05). Oxygen desaturation index and minimum oxygen saturation were moderately correlated with AA and DTA sizes in patients without comorbidities (P < .01). In this group, subjects with oxygen desaturation index > 30 or minimum oxygen saturation < 81% had greater AA and DTA dimensions (P < .05).

CONCLUSIONS

In patients with OSA, time of oxygen saturation < 90% influenced AA and MPA sizes. In those patients without comorbidities, oxygen desaturation index and minimum oxygen saturation were moderately correlated with both AA and DTA sizes. Participants without comorbidities with oxygen desaturation index > 30 or minimum oxygen saturation < 81% had greater AA and DTA dimensions.

An unexpected paradox: wall shear stress in the aorta is less in patients with severe atherosclerosis regardless of obesity

BACKGROUND

Obesity is a widespread condition that is more prevalent in Western countries compared to others. Aortic atherosclerosis (AA) is a condition that frequently has been associated with obesity. An obesity paradox, where morbidly obese decedents had either no or minimal AA compared to nonobese decedents, recently has been described by some of us. The explanation for this almost counterintuitive paradox has yet to be determined, but a number of hypotheses were advanced, including hemodynamic factors producing aortic wall shear stress (WSS). The purpose of the present study was to determine if there was a relationship between AA and WSS, as determined by postmortem measurement of aortic wall diameters.

METHODS

Circumferences of the aorta at the levels of the ascending, thoracic and abdominal aorta were measured in 274 consecutive autopsies over 2-year period of time. AA was assessed using a previously described grading scale as either mild or severe. Circumferences were mathematically converted to diameters and WSS was calculated using the Hagen-Poiseuille formula. Two different methods to estimate cardiac output were used, both based on literature methods, one of which was body mass index (BMI) dependent, and the other BMI independent. Univariate and multivariable analyses of the relationship between WSS, age, BMI, gender, race and severity of AA were performed.

RESULTS

Of the 274 decedents, 140 had mild and 134 had moderate to severe AA. BMI <35 was associated with moderate to severe AA. WSS was inversely correlated with AA in all these segments of the aorta in each BMI subgroup with the exception of the ascending aorta for decedents with BMI ≤35 kg/m². Contrary to what we had hypothesized, WSS was not a determinant of the obesity paradox. However, among all the variables analyzed, a history of hypertension, diabetes mellitus and age were significant factors for developing AA (relative risk [RR] 0.35, P = .039; RR 1.51, P = .0006, RR 1.19, P = .0001, respectively).

CONCLUSIONS

Our data demonstrate that WSS was unexpectedly lower in decedents with moderate and severe AA as compared to those with mild AA. This observation, which requires further investigations, was seen in all BMI ranges and was confirmed by 2 methods to calculate WSS.

Sex-specific distributions and determinants of thoracic aortic diameters in the elderly

Objective

To provide population-based distributions of thoracic aortic diameters in men and women aged 55 years or older and to identify determinants of thoracic aortic diameters.

Methods

From 2003 to 2006, 2505 participants (1208 men, mean age 69.1±6.8 years) from the prospective population-based Rotterdam Study underwent non-enhanced cardiac CT. The diameter of the ascending (AA) and descending aorta (DA) was measured at the level of the pulmonary bifurcation.

Results

The mean diameter of the ascending and descending aorta was substantially larger in men (38±4 mm and 30±2 mm) than in women (35±3 mm and 27±2 mm). An ascending aortic diameter of larger than 40 mm was found in 228 (18.9%) men and 76 (5.9%) women and a descending aortic diameter larger than 40 mm was found in two men and no women. Male sex was found to be independently associated with larger DA diameter (standardised β 0.24, 95% CI 0.19 to 0.30), while a statistically non-significant trend was found for the AA diameter (standardised β 0.06, 95% CI 0.00 to 0.12). Age, height, weight and traditional cardiovascular risk factors were also associated with larger AA and/or DA diameters. Diabetes was associated with smaller AA and DA diameters. We found no evidence for effect modification by sex.

Conclusions

In persons aged 55 years or older, an ascending aortic diameter of 40 mm or larger was found in 18.9% of men and 5.9% of women. Given the importance of sex, sex-specific distribution values may prove useful in clinical practice, even when correcting for body surface area or height.

High prevalence of ascending aortic dilatation in a consecutive coronary CT angiography patient population

Objectives

To clarify the prevalence and risk factors of ascending aortic (AA) dilatation according to ESC 2014 guidelines.

Methods

This study included 1000 consecutive patients scheduled for diagnostic coronary artery computed tomographic angiography. AA diameter was retrospectively measured in 3 planes: sinus valsalva, sinotubular junction, and tubular part. The threshold for AA dilatation was set to > 40 mm which has been suggested as an upper normal limit for AA diameter in ESC 2014 guidelines on aortic diseases. Aortic size index (ASI) using the ratio between aortic diameter and body surface area (BSA) was applied as a comparative measurement. The threshold for AA dilatation was set to the upper limit of normal distribution exceeding two standard deviations (95%). Risk factors for AA dilatation were collected from medical records.

Results

The patients’ mean age was 52.9 ± 9.8 years (66.5% women). The prevalence of AA dilatation was 23.0% in the overall study population (52.5% males) and 15.1% in the subgroup of patients with no coronary artery disease or bicuspid (BAV)/mechanical aortic valve (n = 365). According to the normal-distributed ASI values, the threshold for sinus valsalva was defined as 23.2 mm/m² and for tubular part 22.2 mm/m² in the subgroup. Higher BSA was associated with larger AA dimensions (r = 0.407, p < 0.001). Male gender (p < 0.001), BAV (p < 0.001), hypertension (p = 0.009) in males, and smoking (p < 0.001) appeared as risk factors for AA dilatation.

Conclusions

The prevalence of AA dilatation is high with current ESC guidelines for normal AA dimension, especially in males. Body size is strongly associated with AA dimensions; it would be more reliable to use BSA-adjusted AA diameters for the definition of AA dilatation.

Key Points

• The prevalence of AA dilatation is high in patients who are candidates for coronary CT angiography.

• Body size is strongly associated with AA dimensions.

Ascending aortic size in aortic coarctation depends on aortic valve morphology: Understanding the bicuspid valve phenotype

BACKGROUND

In roughly half of patients with coarctation of the aorta (CoA), the aorta may be enlarged. It is uncertain whether enlargement is independent of aortic valve morphology. We sought to compare aortic size in CoA with a tricuspid valve (TAV) to those with bicuspid aortic valve (BAV).

METHODS

Sixty-eight CoA patients and 20 healthy controls with prior cardiac magnetic resonance (CMR) imaging were included. CMR was retrospectively reanalyzed to measure aortic root and mid-ascending aorta. The maximum aortic diameter was compared between CoA with TAV, CoA with BAV, and control groups.

RESULTS

CoA with TAV patients (n=27) had smaller aortic root diameters than CoA with BAV (n=41) (32±4.9 vs. 37±5.8mm, p=0.001), despite being older (40 vs. 32years, p=0.01). Similarly, TAV CoA patients had a smaller mid-ascending aortic diameter (28±4.5 vs. 33±6.9mm, p=0.019) than BAV patients. TAV CoA was similar to controls in all metrics. Twenty-four patients (35%) with CoA had dilated aortas (>37mm), of which 79% had BAV. A history of hypertension did not predict larger aortic root or mid-ascending aortic dimensions.

CONCLUSIONS

In patients with CoA, TAV is associated with smaller aortic size compared to those with BAV, and similar to healthy controls. Aortic size in CoA is independent of hypertension. Therefore, aortopathy associated with BAV is likely a reflection of the BAV phenotype rather than CoA or its physiologic effects. This distinction may have implications for the frequency and types of monitoring and treatment of CoA patients.

Four-dimensional flow MRI of stented versus stentless aortic valve bioprostheses

Objectives

To evaluate aortic velocity, wall shear stress (WSS) and viscous energy loss (EL) of stented and stentless bioprostheses using 4D flow MRI 1 year after surgical aortic valve replacement.

Methods

For this cross-sectional study 28 patients with stented (n = 14) or stentless (n = 14) bioprosthesis underwent non-contrast-enhanced 4D-flow MRI at 1.5 T. Analyses included a comparison of velocity, WSS and EL in the ascending aorta during peak systole for both spatially averaged values and a comparison of local differences using per-voxel analysis.

Results

No significant differences were found in peak and mean velocity (stented vs. stentless: 2.45 m/s vs. 2.11 m/s; p = 0.09 and 0.60 m/s vs. 0.62 m/s; p = 0.89), WSS (0.60 Pa vs. 0.59 Pa; p = 0.55) and EL (10.17 mW vs. 7.82 mW; p = 0.10). Per-voxel analysis revealed significantly higher central lumen velocity, and lower outer lumen velocity, WSS and EL for stentless versus stented prostheses.

Conclusion

One year after aortic valve implantation with stented and stentless bioprostheses, velocity, WSS and EL were comparable when assessed for averaged values in the ascending aorta. However, the flow profile described with local analysis for stentless prosthesis is potentially favourable with a significantly higher central velocity profile and lower values for outer lumen velocity, WSS and EL.

Key Points

• Stentless bioprostheses can be implanted instead of stented aortic valve bioprostheses.

• Haemodynamic performance of valve prosthesis can be assessed using 4D flow MRI.

• Averaged ascending aorta PSV, WSS and EL are comparable 1 year post-implantation.

• Centreline velocity is highest, WSS and EL is lowest for stentless prosthesis.

Reference Values for Cardiac and Aortic Magnetic Resonance Imaging in Healthy, Young Caucasian Adults

Background

Reference values for morphological and functional parameters of the cardiovascular system in early life are relevant since they may help to identify young adults who fall outside the physiological range of arterial and cardiac ageing. This study provides age and sex specific reference values for aortic wall characteristics, cardiac function parameters and aortic pulse wave velocity (PWV) in a population-based sample of healthy, young adults using magnetic resonance (MR) imaging.

Materials and Methods

In 131 randomly selected healthy, young adults aged between 25 and 35 years (mean age 31.8 years, 63 men) of the general-population based Atherosclerosis-Monitoring-and-Biomarker-measurements-In-The-YOuNg (AMBITYON) study, descending thoracic aortic dimensions and wall thickness, thoracic aortic PWV and cardiac function parameters were measured using a 3.0T MR-system. Age and sex specific reference values were generated using dedicated software. Differences in reference values between two age groups (25–30 and 30–35 years) and both sexes were tested.

Results

Aortic diameters and areas were higher in the older age group (all p<0.007). Moreover, aortic dimensions, left ventricular mass, left and right ventricular volumes and cardiac output were lower in women than in men (all p<0.001). For mean and maximum aortic wall thickness, left and right ejection fraction and aortic PWV we did not observe a significant age or sex effect.

Conclusion

This study provides age and sex specific reference values for cardiovascular MR parameters in healthy, young Caucasian adults. These may aid in MR guided pre-clinical identification of young adults who fall outside the physiological range of arterial and cardiac ageing.

Population-based imaging biobanks as source of big data

Advances of computational sciences over the last decades have enabled the introduction of novel methodological approaches in biomedical research. Acquiring extensive and comprehensive data about a research subject and subsequently extracting significant information has opened new possibilities in gaining insight into biological and medical processes. This so-called big data approach has recently found entrance into medical imaging and numerous epidemiological studies have been implementing advanced imaging to identify imaging biomarkers that provide information about physiological processes, including normal development and aging but also on the development of pathological disease states. The purpose of this article is to present existing epidemiological imaging studies and to discuss opportunities, methodological and organizational aspects, and challenges that population imaging poses to the field of big data research.