Agreement between methods of measurement of mean aortic wall thickness by MRI

Simultaneous Highly Efficient Contrast-Free Lumen and Vessel Wall MR Imaging for Anatomical Assessment of Aortic Disease

BACKGROUND

Bright-blood lumen and black-blood vessel wall imaging are required for the comprehensive assessment of aortic disease. These images are usually acquired separately, resulting in long examinations and potential misregistration between images.

PURPOSE

To characterize the performance of an accelerated and respiratory motion-compensated three-dimensional (3D) cardiac MRI technique for simultaneous contrast-free aortic lumen and vessel wall imaging with an interleaved T2 and inversion recovery prepared sequence (iT2Prep-BOOST).

STUDY TYPE

Prospective.

POPULATION

A total of 30 consecutive patients with aortopathy referred for a clinically indicated cardiac MRI examination (9 females, mean age ± standard deviation: 32 ± 12 years).

FIELD STRENGTH/SEQUENCE

1.5-T; bright-blood MR angiography (diaphragmatic navigator-gated T2-prepared 3D balanced steady-state free precession [bSSFP], T2Prep-bSSFP), breath-held black-blood two-dimensional (2D) half acquisition single-shot turbo spin echo (HASTE), and 3D bSSFP iT2Prep-BOOST.

ASSESSMENT

iT2Prep-BOOST bright-blood images were compared to T2prep-bSSFP images in terms of aortic vessel dimensions, lumen-to-myocardium contrast ratio (CR), and image quality (diagnostic confidence, vessel sharpness and presence of artifacts, assessed by three cardiologists on a 4-point scale, 1: nondiagnostic to 4: excellent). The iT2Prep-BOOST black-blood images were compared to 2D HASTE images for quantification of wall thickness. A visual comparison between computed tomography (CT) and iT2Prep-BOOST was performed in a patient with chronic aortic dissection.

STATISTICAL TESTS

Paired t-tests, Wilcoxon signed-rank tests, intraclass correlation coefficient (ICC), Bland-Altman analysis. A P value < 0.05 was considered statistically significant.

RESULTS

Bright-blood iT2Prep-BOOST resulted in significantly improved image quality (mean ± standard deviation 3.8 ± 0.5 vs. 3.3 ± 0.8) and CR (2.9 ± 0.8 vs. 1.8 ± 0.5) compared with T2Prep-bSSFP, with a shorter scan time (7.8 ± 1.7 minutes vs. 12.9 ± 3.4 minutes) while providing a complementary 3D black-blood image. Aortic lumen diameter and vessel wall thickness measurements in bright-blood and black-blood images were in good agreement with T2Prep-bSSFP and HASTE images (<0.02 cm and <0.005 cm bias, respectively) and good intrareader (ICC > 0.96) and interreader (ICC > 0.94) agreement was observed for all measurements.

DATA CONCLUSION

iT2Prep-BOOST might enable time-efficient simultaneous bright- and black-blood aortic imaging, with improved image quality compared to T2Prep-bSSFP and HASTE imaging, and comparable measurements for aortic wall and lumen dimensions.

EVIDENCE LEVEL

2.

TECHNICAL EFFICACY

Stage 2.

Arterial Remodeling of the Intracranial Arteries in Patients With Hypertension and Controls: A Postmortem Study

The intracranial arteries play a major role in cerebrovascular disease, but arterial remodeling due to hypertension has not been well described in humans. We aimed to quantify this remodeling for: the basilar artery, the vertebral, internal carotid, middle/anterior (inferior)/posterior cerebral, posterior communicating, and superior cerebellar arteries of the circle of Willis. Ex vivo circle of Willis specimens, selected from individuals with (n=24) and without (n=25) a history of hypertension, were imaged at 7T magnetic resonance imaging using a 3-dimensional gradient-echo sequence. Subsequently, histological analysis was performed. We validated the vessel wall thickness and area measurements from magnetic resonance imaging against histology. Next, we investigated potential differences in vessel wall thickness and area between both groups using both techniques. Finally, using histological analysis, we investigated potential differences in arterial wall stiffness and atherosclerotic plaque severity and load. All analyses were unadjusted. Magnetic resonance imaging and histology showed comparable vessel wall thickness (mean difference: 0.04 mm (limits of agreement:-0.12 to 0.19 mm) and area (0.43 mm² [-0.97 to 1.8 mm²]) measurements. We observed no statistically significant differences in vessel wall thickness and area between both groups using either technique. Histological analysis showed early and advanced atherosclerotic plaques in almost all arteries for both groups. The arterial wall stiffness was significantly higher for the internal carotid artery in the hypertensive group. Concluding, we did not observe vessel wall thickening in the circle of Willis arteries in individuals with a history of hypertension using either technique. Using histological analysis, we observed a difference in vessel wall composition for the internal carotid artery.

High-sensitivity cassette for reducing limit of detection for diesel particulate matter sampling

NIOSH researchers designed a high-sensitivity (HS) cassette to improve the limit of detection of the National Institute for Occupational Safety and Health's (NIOSH) method 5040 and the Airtec near real-time diesel particulate matter (DPM) monitor. This was achieved by reducing the size of the diesel particulate matter deposition spot from 8.0 cm² (NIOSH method 5040 mining samples) and 7.6 cm² (Airtec samples) to 0.5 cm². When compared with the standard cassette, the new high-sensitivity cassette improves the limit of detection of NIOSH method 5040 by approximately five times, and the differences between the elemental carbon results from the HS cassette and the standard three-piece cassette were within statistical error. The limit of detection for Airtec measurements improved by approximately 15 times, and the elemental carbon results with the HS cassette between the Airtec and NIOSH method 5040 were within statistical agreement. When used in the Airtec monitor, the high-sensitivity cassette showed promise for measuring short-duration spot checks of ambient concentrations but was limited when performing some long-term sampling due to the resultant loss of dynamic range. Only up to 7 μg of elemental carbon was collected onto the HS cassette before the increase in pump backpressure caused the flow fluctuations to exceed targeted values by unacceptable levels. The HS cassette shows promise for effective engineering evaluations of control technologies and strategies and near real-time diesel particulate matter measurements for a variety of occupations.

Vessel wall and lumen characteristics with age in healthy participants using 3T intracranial vessel wall magnetic resonance imaging

BACKGROUND

Intracranial vessel wall imaging (VWI) at a clinical field strength of 3T has become more widely available. However, how vessel measurements change with age and sex, over an age range spanning a typical lifespan, are needed.

PURPOSE/HYPOTHESIS

To assess for identifiable changes in arterial wall thickness, outer vessel wall diameter, and lumen diameter with age cross-sectionally in healthy controls without cerebrovascular disease risk factors at the spatial resolution afforded by currently recommended 3T VWI approaches.

STUDY TYPE

Prospective.

POPULATION/SUBJECTS

Healthy subjects (n = 82; age = 8-79 years).

FIELD STRENGTH/SEQUENCE

3T intracranial VWI, angiography, and T1 -weighted anatomical imaging.

ASSESSMENT

Two readers measured lumen and outer wall diameters of the supraclinoid internal carotid artery (ICA) and distal basilar artery. Wall thickness and intraclass correlation coefficients (ICCs) were calculated.

STATISTICAL TESTS

Separate linear regressions were performed to understand the relationship between wall measurements (lumen diameter, outer vessel wall diameter, and wall thickness) and age, gender, side (left or right); significance: two-sided P < 0.05.

RESULTS

Readers showed excellent agreement for lumen and outer wall diameters (ICC 0.83-094). Linear regression of supraclinoid ICA wall measurements showed a statistically significant increase in wall thickness (P = 0.00051) and outer vessel wall diameter (P = 0.030) with age. ICA lumen and outer vessel wall diameters were statistically greater in males vs. females (lumen diameter 3.69 ± 0.41 vs. 3.54 ± 0.35 mm, P = 0.026; outer wall diameter 5.78 ± 0.52 vs. 5.56 ± 0.44 mm, P = 0.0089) with a trend toward increase in wall thickness (1.05 ± 0.12 vs. 1.01 ± 0.10 mm, P = 0.055). No significant difference was found in basilar artery wall thickness (P = 0.45, P = 0.72), lumen diameter (P = 0.15, P = 0.42), or outer vessel wall diameter (P = 0.34, P = 0.41) with age or gender, respectively.

DATA CONCLUSION

Intracranial vessel wall measurements were shown to be consistent between readers. At the available spatial resolution of 3T intracranial VWI sequences, supraclinoid ICA vessel wall thickness and outer vessel wall diameter appear to mildly increase with age. There was no detectable change in basilar artery vessel wall characteristics with age.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:1452-1460.

Data on vessel wall thickness measurements of intracranial arteries derived from human circle of Willis specimens

In this article, we report data on vessel wall thickness parameters derived from different arterial segments of the circle of Willis and its primary branches in patients with and without cerebrovascular disease. Also data on inter-rater reliability and agreement of the derived vessel wall parameters are reported. For further interpretation and discussion please refer to the research article “ex vivo vessel wall thickness measurements of the human circle of Willis using 7T MRI” (Harteveld et al., in press) [1].

Ex vivo vessel wall thickness measurements of the human circle of Willis using 7T MRI

BACKGROUND AND AIMS

MRI can detect intracranial vessel wall thickening before any luminal stenosis is present. Apart from representing a vessel wall lesion, wall thickening could also reflect normal (age-related) variations in vessel wall thickness present throughout the intracranial arterial vasculature. The aim of this study was to perform vessel wall thickness measurements of the major intracranial arteries in ex vivo circle of Willis (CoW) specimens using 7T MRI, to obtain more detailed information about wall thickness variations of the intracranial arteries.

METHODS

Fifteen human CoW specimens were scanned at 7T MRI with an ultrahigh-resolution T₁-weighted sequence. Five specimens were used for validation of MRI measurements with histology and evaluation of inter-rater reliability and agreement. The other 10 specimens from patients with (n = 5) and without (n = 5) cerebrovascular disease were used for vessel wall thickness measurements over the entire length of the major arterial segments of the CoW using MRI only.

RESULTS

MRI measurements showed excellent agreement with histology. Mean wall thickness varied from 0.45 to 0.66 mm, minimum wall thickness from 0.31 to 0.42 mm, maximum wall thickness from 0.52 to 0.86 mm, and normalized wall index from 0.64 to 0.75. On average, vessel walls were thicker for symptomatic patients compared to asymptomatic patients.

CONCLUSIONS

High-resolution MRI enables accurate measurement of vessel wall thickness in ex vivo CoW specimens. Vessel wall thickness measurements over the entire length of segments showed considerable variation both within and between arterial segments of patients.

Growth Description for Vessel Wall Adaptation: A Thick-Walled Mixture Model of Abdominal Aortic Aneurysm Evolution

(1) Background: Vascular tissue seems to adapt towards stable homeostatic mechanical conditions, however, failure of reaching homeostasis may result in pathologies. Current vascular tissue adaptation models use many ad hoc assumptions, the implications of which are far from being fully understood; (2) Methods: The present study investigates the plausibility of different growth kinematics in modeling Abdominal Aortic Aneurysm (AAA) evolution in time. A structurally motivated constitutive description for the vessel wall is coupled to multi-constituent tissue growth descriptions; Constituent deposition preserved either the constituent’s density or its volume, and Isotropic Volume Growth (IVG), in-Plane Volume Growth (PVG), in-Thickness Volume Growth (TVG) and No Volume Growth (NVG) describe the kinematics of the growing vessel wall. The sensitivity of key modeling parameters is explored, and predictions are assessed for their plausibility; (3) Results: AAA development based on TVG and NVG kinematics provided not only quantitatively, but also qualitatively different results compared to IVG and PVG kinematics. Specifically, for IVG and PVG kinematics, increasing collagen mass production accelerated AAA expansion which seems counterintuitive. In addition, TVG and NVG kinematics showed less sensitivity to the initial constituent volume fractions, than predictions based on IVG and PVG; (4) Conclusions: The choice of tissue growth kinematics is of crucial importance when modeling AAA growth. Much more interdisciplinary experimental work is required to develop and validate vascular tissue adaption models, before such models can be of any practical use.

A new inverse method for estimation of in vivo mechanical properties of the aortic wall

The aortic wall is always loaded in vivo, which makes it challenging to estimate the material parameters of its nonlinear, anisotropic constitutive equation from in vivo image data. Previous approaches largely relied on either computationally expensive finite element models or simplifications of the geometry or material models. In this study, we investigated a new inverse method based on aortic wall stress computation. This approach consists of the following two steps: (1) computing an "almost true" stress field from the in vivo geometries and loading conditions, (2) building an objective function based on the "almost true" stress fields, constitutive equations and deformation relations, and estimating the material parameters by minimizing the objective function. The method was validated through numerical experiments by using the in vivo data from four ascending aortic aneurysm (AsAA) patients. The results demonstrated that the method is computationally efficient. This novel approach may facilitate the personalized biomechanical analysis of aortic tissues in clinical applications, such as in the rupture risk analysis of ascending aortic aneurysms.

Continuous measurement of aortic dimensions in Turner syndrome: a cardiovascular magnetic resonance study

BACKGROUND

Severity of thoracic aortic disease in Turner syndrome (TS) patients is currently described through measures of aorta size and geometry at discrete locations. The objective of this study is to develop an improved measurement tool that quantifies changes in size and geometry over time, continuously along the length of the thoracic aorta.

METHODS

Cardiovascular magnetic resonance (CMR) scans for 15 TS patients [41 ± 9 years (mean age ± standard deviation (SD))] were acquired over a 10-year period and compared with ten healthy gender and age-matched controls. Three-dimensional aortic geometries were reconstructed, smoothed and clipped, which was followed by identification of centerlines and planes normal to the centerlines. Geometric variables, including maximum diameter and cross-sectional area, were evaluated continuously along the thoracic aorta. Distance maps were computed for TS and compared to the corresponding maps for controls, to highlight any asymmetry and dimensional differences between diseased and normal aortae. Furthermore, a registration scheme was proposed to estimate localized changes in aorta geometry between visits. The estimated maximum diameter from the continuous method was then compared with corresponding manual measurements at 7 discrete locations for each visit and for changes between visits.

RESULTS

Manual measures at the seven positions and the corresponding continuous measurements of maximum diameter for all visits considered, correlated highly (R-value = 0.77, P < 0.01). There was good agreement between manual and continuous measurement methods for visit-to-visit changes in maximum diameter. The continuous method was less sensitive to inter-user variability [0.2 ± 2.3 mm (mean difference in diameters ± SD)] and choice of smoothing software [0.3 ± 1.3 mm]. Aortic diameters were larger in TS than controls in the ascending [TS: 13.4 ± 2.1 mm (mean distance ± SD), Controls: 12.6 ± 1 mm] and descending [TS: 10.2 ± 1.3 mm (mean distance ± SD), Controls: 9.5 ± 0.9 mm] thoracic aorta as observed from the distance maps.

CONCLUSIONS

An automated methodology is presented that enables rapid and precise three-dimensional measurement of thoracic aortic geometry, which can serve as an improved tool to define disease severity and monitor disease progression.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier - NCT01678274 . Registered - 08.30.2012.

Computational evaluation of aortic occlusion and the proposal of a novel, improved occluder: Constrained endo-aortic balloon occlusion

Because aortic occlusion is arguably one of the most dangerous aortic manipulation maneuvers during cardiac surgery in terms of perioperative ischemic neurological injury, the purpose of this investigation is to assess the structural mechanical impact resulting from the use of existing and newly proposed occluders. Existing (clinically used) occluders considered include different cross-clamps (CCs) and endo-aortic balloon occlusion (EABO). A novel occluder is also introduced, namely, constrained EABO (CEABO), which consists of applying a constrainer externally around the aorta when performing EABO. Computational solid mechanics are employed to investigate each occluder according to a comprehensive list of functional requirements. The potential of a state of occlusion is also considered for the first time. Three different constrainer designs are evaluated for CEABO. Although the CCs were responsible for the highest strains, largest deformation, and most inefficient increase of the occlusion potential, it remains the most stable, simplest, and cheapest occluder. The different CC hinge geometries resulted in poorer performance of CC used for minimally invasive procedures than conventional ones. CEABO with a profiled constrainer successfully addresses the EABO shortcomings of safety, stability, and positioning accuracy, while maintaining its complexities of operation (disadvantage) and yielding additional functionalities (advantage). Moreover, CEABO is able to achieve the previously unattainable potential to provide a clinically determinable state of occlusion. CEABO offers an attractive alternative to the shortcomings of existing occluders, with its design rooted in achieving the highest patient safety. Copyright © 2016 John Wiley & Sons, Ltd.

Cardiovascular risk factors and thoracic aortic wall thickness in a general population

PURPOSE

To evaluate the association of cardiovascular risk factors with wall thickness of the ascending and descending thoracic aorta in the general population.

MATERIALS AND METHODS

The study included 1,176 individuals (523 women) 21-83 years old from the Study of Health in Pomerania without history of stroke or myocardial infarction. Aortic wall thickness (AWT) was determined by cine magnetic resonance imaging. The associations of AWT with the cardiovascular risk factors male sex, age, smoking, body mass index (BMI), systolic and diastolic blood pressure, hemoglobin A1c, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides were assessed by multivariable linear regression models, and interaction effects were tested.

RESULTS

Male sex (β = .086, P < .001), age (β = .006, P < .001), and BMI (β = .013, P < .001) were positively associated with the AWT of the ascending aorta. Male sex (β = .105, P < .001), age (β = .006, P < .001), current smoker (β = .044, P = .010), BMI (β = .013, P < .001), and HDL-C (β = .057, P = .008) revealed a positive association with AWT of the descending aorta. LDL-C (β = -.024, P = .009; β = -.018, P = .010) was inversely associated with the AWT of the ascending and descending aorta, respectively. Triglyceride levels (β = .024, P = .027; β = .018, P = .024) showed a positive association with the AWT of the ascending and descending aorta, respectively, in men, but not in women.

CONCLUSIONS

Established cardiovascular risk factors, including male sex, older age, smoking, high BMI, and high triglyceride levels, were associated with increasing thoracic AWT of the ascending and descending aorta. High HDL-C and low LDL-C levels were correlated with AWT.

MRI-based determination of reference values of thoracic aortic wall thickness in a general population

OBJECTIVES

To provide age- and sex-specific reference values for MRI-derived wall thickness of the ascending and descending aorta in the general population.

MATERIALS AND METHODS

Data of 753 subjects (311 females) aged 21-81 years were analysed. MRI was used to determine the aortic wall thickness (AWT). Equations for reference value calculation according to age were established for females and males.

RESULTS

Median wall thickness of the ascending aorta was 1.46 mm (5th-95th range: 1.15-1.88 mm) for females and 1.56 mm (1.22-1.99 mm) for males. Median wall thickness of the descending aorta was 1.26 mm (0.97-1.58 mm) in females and 1.36 mm (1.04-1.75 mm) in males. While median and 5th and 95th percentiles for the ascending and descending aorta increased with age in both sexes, the association between age and median AWT was stronger in males than in females for both the ascending and descending aorta.

CONCLUSIONS

Reference values for the ascending and descending AWT are provided. In a healthy sample from the general population, the wall of the ascending aorta is thicker than the wall of the descending aorta, and both walls are thicker in males than females. The increase in wall thickness with age is greater in males.

KEY POINTS

Ascending aortic wall thickness is greater than descending aortic wall thickness. Ascending and descending aortic wall thickness is greater in males. Thoracic aortic wall thickness increases with age in both sexes. The age-related increase in aortic wall thickness is stronger in males.

Mean thoracic aortic wall thickness determination by cine MRI with steady-state free precession: validation with dark blood imaging

RATIONALE AND OBJECTIVES

To assess the validity and reliability of measuring mean aortic wall thickness (MAWT) of the ascending and descending aorta using cine steady-state free precession (SSFP) imaging compared to dark blood (DB) imaging.

MATERIALS AND METHODS

DB and SSFP images of the thoracic aorta acquired at 1.5 T in 50 volunteers (26 women, 24 men; mean age: 50.2 ± 13.1 years) were used. MAWT was calculated on DB and SSFP images for the ascending and descending aorta at the level of the right pulmonary artery by two independent observers. Validity was assessed using Bland-Altman analysis, Passing-Bablok regression, and Spearman correlation. Reliability was assessed using Bland-Altman analysis and intraclass coefficients (ICCs).

RESULTS

The mean MAWT of the ascending aorta on DB and SSFP images was 1.89 ± 0.21 mm and 1.87 ± 0.20 mm. The measurements for the descending aorta were 1.60 ± 0.22 and 1.63 ± 0.20 mm, respectively. Comparison of DB and SSFP measurements revealed a mean bias of 1.3% (95% limits of agreement (LOA): -7.9, 10.5%) for the ascending and of -2.1% (LOA: -10.5, 6.3%) for the descending aorta. The corresponding regression equation was y = 0.042 + 0.960 × (r = 0.91; P < .0001) and y = 0.118 + 0.939 × (r = 0.95; P < .0001), respectively. Intra- and interobserver variability showed a mean bias of less than 2.0% and LOA of less than ±15.0%. ICCs were greater than or equal to 0.85.

CONCLUSIONS

MAWT determination in the ascending and descending aorta using cine SSFP sequences is highly valid and reliable compared to DB imaging.

Abdominal aortic atherosclerosis at MR imaging is associated with cardiovascular events: the Dallas heart study

PURPOSE

To determine the value of two abdominal aortic atherosclerosis measurements at magnetic resonance (MR) imaging for predicting future cardiovascular events.

MATERIALS AND METHODS

This study was approved by the institutional review board and complied with HIPAA regulations. The study consisted of 2122 participants from the multiethnic, population-based Dallas Heart Study who underwent abdominal aortic MR imaging at 1.5 T. Aortic atherosclerosis was measured by quantifying mean aortic wall thickness (MAWT) and aortic plaque burden. Participants were monitored for cardiovascular death, nonfatal cardiac events, and nonfatal extracardiac vascular events over a mean period of 7.8 years ± 1.5 (standard deviation [SD]). Cox proportional hazards regression was used to assess independent associations of aortic atherosclerosis and cardiovascular events.

RESULTS

Increasing MAWT was positively associated with male sex (odds ratio, 3.66; P < .0001), current smoking (odds ratio, 2.53; P < .0001), 10-year increase in age (odds ratio, 2.24; P < .0001), and hypertension (odds ratio, 1.66; P = .0001). A total of 143 participants (6.7%) experienced a cardiovascular event. MAWT conferred an increased risk for composite events (hazard ratio, 1.28 per 1 SD; P = .001). Aortic plaque was not associated with increased risk for composite events. Increasing MAWT and aortic plaque burden both conferred an increased risk for nonfatal extracardiac events (hazard ratio of 1.52 per 1 SD [P < .001] and hazard ratio of 1.46 per 1 SD [P = .03], respectively).

CONCLUSION

MR imaging measures of aortic atherosclerosis are predictive of future adverse cardiovascular events.

Analysis of carotid artery plaque and wall boundaries on CT images by using a semi-automatic method based on level set model

INTRODUCTION

The purpose of this study was to evaluate the potentialities of a semi-automated technique in the detection and measurement of the carotid artery plaque.

METHODS

Twenty-two consecutive patients (18 males, 4 females; mean age 62 years) examined with MDCTA from January 2011 to March 2011 were included in this retrospective study. Carotid arteries are examined with a 16-multi-detector-row CT system, and for each patient, the most diseased carotid was selected. In the first phase, the carotid plaque was identified and one experienced radiologist manually traced the inner and outer boundaries by using polyline and radial distance method (PDM and RDM, respectively). In the second phase, the carotid inner and outer boundaries were traced with an automated algorithm: level-set-method (LSM). Data were compared by using Pearson rho correlation, Bland-Altman, and regression.

RESULTS

A total of 715 slices were analyzed. The mean thickness of the plaque using the reference PDM was 1.86 mm whereas using the LSM-PDM was 1.96 mm; using the reference RDM was 2.06 mm whereas using the LSM-RDM was 2.03 mm. The correlation values between the references, the LSM, the PDM and the RDM were 0.8428, 0.9921, 0.745 and 0.6425. Bland-Altman demonstrated a very good agreement in particular with the RDM method.

CONCLUSION

Results of our study indicate that LSM method can automatically measure the thickness of the plaque and that the best results are obtained with the RDM. Our results suggest that advanced computer-based algorithms can identify and trace the plaque boundaries like an experienced human reader.

Circulating levels of matrix metalloproteinase-9 and abdominal aortic pathology: from the Dallas Heart Study

Prior reports have associated increased circulating levels of matrix metalloproteinase-9 (MMP-9), an endopeptidase active in the extracellular matrix, with the formation and rupture of aortic aneurysms, raising the possibility that MMP-9 may be a useful diagnostic or therapeutic target for aortic pathology. However, associations between MMP-9 and pathological abdominal aortic phenotypes in the general population have not been reported. In the Dallas Heart Study, a population-based sample of Dallas County residents (n = 2304), we measured MMP-9 and performed magnetic resonance imaging (MRI) of the abdominal aorta, measuring aortic compliance, plaque, wall thickness and luminal diameter. After adjustment for traditional cardiac risk factors and body size, higher MMP-9 quartiles were independently associated with higher aortic wall thickness and larger luminal diameter (p < 0.0001 for each), but not abdominal aortic plaque (p = 0.08), coronary artery calcium (p = 0.20) or the aortic luminal diameter/aortic wall thickness ratio (p = 0.37), supporting the hypothesis that therapies targeting MMP-9 may affect the abdominal aortic wall and modify aortic pathology.

Race-specific associations of myeloperoxidase with atherosclerosis in a population-based sample: the Dallas Heart Study

OBJECTIVE

Myeloperoxidase (MPO) is a leukocyte-derived enzyme that appears to be directly involved in atherosclerosis development. We evaluated the association of circulating MPO with coronary and aortic atherosclerosis in a large, multiethnic population.

METHODS AND RESULTS

Plasma levels of MPO were measured in 3294 subjects participating in the Dallas Heart Study, a probability-based population sample. Coronary artery calcification (CAC) was measured by EBCT, and abdominal aorta plaque prevalence (AP) and burden (APB), as well as abdominal aorta wall thickness (AWT) were determined by MRI. Associations between MPO and atherosclerosis phenotypes were assessed in multivariable analyses adjusting for traditional atherosclerosis risk factors. MPO levels in the 4th compared with 1st quartile independently associated with prevalent AP (OR 1.41, 95% CI 1.08-1.84), APB (beta coefficient 0.23, p = 0.02), and AWT (beta coefficient 0.04, p = 0.03), but not with prevalent CAC (OR 0.84, 95% CI 0.61-1.17). MPO remained associated with aortic atherosclerosis phenotypes but not coronary calcification after adjustment for other inflammatory biomarkers. A significant interaction was observed between race/ethnicity, MPO and AP (p(interaction) = 0.038), such that MPO levels in the 4th vs 1st quartile associated with prevalent AP in African Americans, (OR 1.81, 95% CI 1.23-2.65) but not in White or Hispanic participants (OR 0.99, 95% CI 0.68-1.44).

CONCLUSION

Higher levels of MPO associated with aortic but not coronary atherosclerosis, with significant associations limited to African American participants. These findings suggest that MPO might be a novel risk factor contributing to racial disparities in peripheral vascular disease.

Sex, race, and age distributions of mean aortic wall thickness in a multiethnic population-based sample

BACKGROUND

Reference values and age-related changes of the wall thickness of the abdominal aorta have not been described in the general population. We characterized age-, race-, and gender-specific distributions, and yearly rates of change of mean aortic wall thickness (MAWT), and associations between MAWT and cardiovascular risk factors in a multi-ethnic population-based probability sample.

METHODS

Magnetic resonance imaging measurements of MAWT were performed on 2466 free-living white, black, and Hispanic adult subjects. MAWT race/ethnicity- and gender-specific percentile values across age were estimated using regression analyses.

RESULTS

MAWT was greater in men than in women and increased linearly with age in all the groups and across all the percentiles. Hispanic women had the thinnest and black men the thickest aortas. Black men had the highest and white women the lowest age-related MAWT increase. Age, gender, ethnicity, smoking status, systolic blood pressure, low-density lipoprotein-cholesterol levels, high-density lipoprotein-cholesterol levels, and fasting glucose levels were independent predictors of MAWT.

CONCLUSIONS

Age, gender, and racial/ethnic differences in MAWT distributions exist in the general population. Such differences should be considered in future investigations assessing aortic atherosclerosis and the effects of anti-atherosclerotic therapies.

Left ventricular hypertrophy, aortic wall thickness, and lifetime predicted risk of cardiovascular disease:the Dallas Heart Study

OBJECTIVES

To examine whether individuals with low short-term risk of coronary heart disease but high lifetime predicted risk of cardiovascular disease (CVD) have greater prevalence of left ventricular (LV) hypertrophy and increased aortic wall thickness (AWT) than those with low short-term and low lifetime risk.

BACKGROUND

Lifetime risk prediction can be used for stratifying individuals younger than 50 years of age into 2 groups: low short-term/high lifetime and low short-term/low lifetime predicted risk of CVD. Individuals with low short-term/high lifetime risk have a greater burden of subclinical atherosclerosis as measured by coronary artery calcium and carotid intima-media thickness. However, >75% of individuals with low short-term/high lifetime risk do not have detectable coronary artery calcium, suggesting the presence of alternative subclinical abnormalities.

METHODS

We stratified 1,804 Dallas Heart Study subjects between the ages of 30 and 50 years who had cardiac magnetic resonance into 3 groups: low short-term (<10% 10-year risk of coronary heart disease)/low lifetime predicted risk (<39% lifetime risk of CVD), low short-term (<10%)/high lifetime risk (> or =39%), and high short-term risk (> or =10%, prevalent diabetes, or previous stroke, or myocardial infarction). In those with low short-term risk, we compared measures of LV hypertrophy and AWT between those with low versus high lifetime risk.

RESULTS

Subjects with low short-term/high lifetime risk compared with those with low short-term/low lifetime risk had increased LV mass (men: 95 +/- 17 g/m(2) vs. 90 +/- 12 g/m(2) and women: 75 +/- 14 g/m(2) vs. 71 +/- 10 g/m(2), respectively; p < 0.001 for both). LV concentricity (mass/volume), wall thickness, and AWT were also significantly greater in those with high lifetime risk in this comparison (p < 0.001 for all), but LV end-diastolic volume was not (p > 0.3). These associations persisted among participants without detectable coronary artery calcium.

CONCLUSIONS

Among individuals 30 to 50 years of age with low short-term risk, a high lifetime predicted risk of CVD is associated with concentric LV hypertrophy and increased AWT.