Reproducibility of functional aortic analysis using magnetic resonance imaging: the MESA

Association of Cardiovascular Fibrosis, Remodeling, and Dysfunction With Frailty, Prefrailty, and Functional Performance: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Cardiovascular disease is associated with higher incidence of frailty. However, the nature of the mechanisms underlying this association remains unclear. The purpose of this study is to identify cardiovascular phenotypes most associated with physical frailty and functional performance in the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS

As part of the MESA study, 3 045 participants underwent cardiovascular magnetic resonance and computed tomography between 2010 and 2012. Of these, 1 743 completed a Six-Minute Walk test (6MWT) and questionnaires (follow-up exam: 2016-2018) which were used to generate a binary combined frail/prefrail versus robust score according to a modified FRAIL Scale (self-report questionnaire). Multivariable logistic (binary frail outcome) or linear (6MWT) regression assessed the association between frailty and cardiovascular structure and function, aortic stiffness, coronary artery calcium, and myocardial fibrosis (ECV, extracellular volume fraction).

RESULTS

Participants were 66 ± 8 years, 52% female at the time of imaging, and 29.4% were classified as frail or prefrail. Older age and female gender were associated with greater odds of being in the frail/prefrail group. Concentric left ventricular remodeling (odds ratio [OR] 1.89, p = .008; Coef. -52.9, p < .001), increased ECV (OR 1.10, p = .002; Coef. -4.0, p = .001), and worsening left atrial strain rate at early diastole (OR 1.56, p ≤ .001; Coef. -22.75, p = .027) were found to be associated with a greater likelihood of being in a frail state and lower 6MWT distance (m). All associations with 6MWT performance were attenuated with adjustments for risk factors whereas ECV and LA strain rate remained independently associated with frailty.

CONCLUSIONS

These findings suggest a significant overlap in pathways associated with subclinical cardiac dysfunction, cardiovascular fibrosis, and physical frailty.

Thoracic Aortic Volume as a Predictor of Cardiovascular Events: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

It is unclear whether thoracic aortic volume (TAV) is useful for cardiovascular (CV) disease prognosis and risk assessment.

PURPOSE

This study evaluated cross-sectional associations of TAV with CV risk factors, and longitudinal association with incident CV events in the multiethnic study of atherosclerosis.

STUDY TYPE

Retrospective cohort analysis of prospective data.

POPULATION

1182 participants (69 ± 9 years, 54% female, 37% Caucasian, 18% Chinese, 31% African American, 14% Hispanic, 60% hypertensive, and 20% diabetic) without prior CV disease.

FIELD STRENGTH AND SEQUENCES

Axial black-blood turbo spin echo or bright blood steady-state free precession images on 1.5T scanners.

ASSESSMENT

TAV was calculated using Simpson's method from axial images, and included the ascending arch and descending segments. Traditional CV risk factors were assessed at the time of MRI. CV outcomes over a 9-year follow-up period were recorded and represented a composite of stroke, stroke death, coronary heart disease (CHD), CHD death, atherosclerotic death, and CVD death.

STATISTICAL TESTS

Multivariable linear regression models adjusted for height and weight were used to determine the relationship (β coefficient) between TAV and CV risk factors. Cox regression models assessed the association of TAV and incident CV events. A P-value of <0.05 was deemed statistically significant.

RESULTS

Mean TAV was = 139 ± 41 mL. In multivariable regression, TAV was directly associated with age (β = 1.6), male gender (β = 23.9), systolic blood pressure (β = 0.1), and hypertension medication use (β = 7.9); and inversely associated with lipid medication use (β = -5.3) and treated diabetes (β = -8.9). Compared to Caucasians, Chinese Americans had higher TAV (β = 11.4), while African Americans had lower TAV (β = -7.0). Higher TAV was independently associated with incident CV events (HR: 1.057 per 10 mL).

CONCLUSION

Greater TAV is associated with incident CV events, increased age, and hypertension in a large multiethnic population while treated diabetes and lipid medication use were associated with lower TAV.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Subclinical association of aortic stiffness with cardiac structure and function in African-Americans: The Jackson Heart Study

Cardiovascular disease (CVD) morbidity and mortality are high among black adults. We aimed to study the granular subclinical relations of aortic stiffness and left ventricular (LV) function and remodeling in blacks, in whom limited data are available. In the Jackson Heart Study, 1050 U.S. community-dwelling black adults without CVD underwent 1.5 T cardiovascular magnetic resonance. We assessed regional and global aortic stiffness and LV structure and function, including LV mass indexed to body surface area (LVMI), end-diastolic volume (LVEDV), ejection fraction (EF), and global and regional circumferential strain (Ecc). Phase contrast images of the cross-sectional aorta at the pulmonary artery bifurcation and abdominal aorta bifurcation were acquired to measure pulse wave velocity of the aortic arch (AA-PWV) and thoracic aorta (T-PWV). Results of multivariable-adjusted analyses are presented as SD unit change in LV variables per SD change in PWV variables. Participants were 62% women with mean age of 59 ± 10 years. Higher AA-PWV and T-PWV were associated with greater LVMI: for T-PWV, β = 0.10, 95% CI = 0.03-0.16, p = 0.002. Higher AA-PWV and T-PWV were associated with worse (more positive) Ecc at the LV base (for AA-PWV, β = 0.13, 95% CI = 0.05-0.20, p = 0.0007), but not mid-LV or apex. AA-PWV and T-PWV were not associated with LV mass/LVEDV or EF. In this cross-sectional study of blacks without CVD in the U.S., aortic stiffness is associated with subclinical adverse LV function in basal segments. Future studies may elucidate the temporal relationships of aortic stiffness on the pattern and progression of LV remodeling, dysfunction, and associated prognosis in blacks.

Cardiovascular Interactions of Renin-Angiotensin-Aldosterone System Assessed by Cardiac Magnetic Resonance: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

The effects of the renin-angiotensin-aldosterone system in cardiovascular system have been described based on small studies. The aim of this study was to evaluate the relationship between aldosterone and plasma renin activity (PRA) and cardiovascular structure and function.

METHODS

We studied a random sample of Multi-Ethnic Study of Atherosclerosis participants who had aldosterone and PRA blood assays at 2003-2005 and underwent cardiac magnetic resonance at 2010. Participants taking angiotensin-converting enzyme inhibitors or angiotensin receptor blockers were excluded.

RESULTS

The aldosterone group was composed by 615 participants, mean age 61.6 ± 8.9 years, while the renin group was 580 participants, mean age 61.5 ± 8.8 years and both groups had roughly 50% females. In multivariable analysis, 1 SD increment of log-transformed aldosterone level was associated with 0.07 g/m2 higher left ventricle (LV) mass index (P = 0.04) and 0.11 ml/m2 higher left atrium (LA) minimal volume index (P < 0.01). Additionally, higher log-transformed aldosterone was associated with lower LA maximum strain and LA emptying fraction (P < 0.01). Aldosterone levels were not significantly associated with aortic measures. Log-transformed PRA was associated with lower LV end diastolic volume index (β standardized = 0.08, P = 0.05). PRA levels were not significantly associated with LA and aortic structural or functional differences.

CONCLUSIONS

Higher levels of aldosterone and PRA are associated with concentric LV remodeling changes. Moreover, aldosterone was related to deleterious LA remodeling changes.

Neighborhood characteristics and arterial stiffness among Black adults - Results from the Jackson Heart Study and Morehouse-Emory Cardiovascular Center for Health Equity

INTRODUCTION

Poor quality neighborhood environments are independent risk factors for cardiovascular disease (CVD) but are understudied in Black adults, who face large CVD health disparities. Arterial stiffness, a marker of early vascular aging, precedes development of hypertension and adverse CVD events but the effect of neighborhood on arterial stiffness among Black adults remains unknown.

OBJECTIVE

We compared the association between neighborhood environment and arterial stiffness among Black adults in Jackson, MS and Atlanta, GA.

METHODS

We studied 1582 Black adults (mean age 53 ± 10, 35% male) living in Jackson, MS from the Jackson Heart Study (JHS) and 451 Black adults (mean age 53 ± 10, 39% male) living in Atlanta, GA from the Morehouse-Emory Cardiovascular Center for Health Equity (MECA) study, without known CVD. Neighborhood problems (includes measures of aesthetic quality, walking environment, food access), social cohesion (includes activity with neighbors), and violence/safety were assessed using validated questionnaires. Arterial stiffness was measured as pulse wave velocity (PWV) using magnetic resonance imaging in JHS and as PWV and augmentation index (AIx) using applanation tonometry (SphygmoCor, Inc.) in MECA. Multivariable linear regression models were used to examine the association between neighborhood characteristics and arterial stiffness, adjusting for potential confounders.

RESULTS

Improved social characteristics, measured as social cohesion in JHS (β = -0.32 [-0.63, -0.02], p = 0.04) and activity with neighbors (β = -0.23 [-0.40, -0.05], p = 0.01) in MECA, were associated with lower PWV in both cohorts and lower AIx (β = -1.74 [-2.92, - 0.56], p = 0.004) in MECA, after adjustment for CVD risk factors and income. Additionally, in MECA, better food access (β = -1.18 [-2.35, - 0.01], p = 0.05) was associated with lower AIx and, in JHS, lower neighborhood problems (β = -0.33 [-0.64, - 0.02], p = 0.04) and lower violence (β = -0.30 [-0.61, 0.002], p = 0.05) were associated with lower PWV.

CONCLUSION

Neighborhood social characteristics show an independent association with the vascular health of Black adults, findings that were reproducible in two distinct American cities.

Cross-Sectional Relationships of Proximal Aortic Stiffness and Left Ventricular Diastolic Function in Adults in the Community

Background Stiffness of the proximal aorta may play a critical role in adverse left ventricular (LV)-vascular interactions and associated LV diastolic dysfunction. In a community-based sample, we sought to determine the association between proximal aortic stiffness measured by cardiovascular magnetic resonance (CMR) and several clinical measures of LV diastolic mechanics. Methods and Results Framingham Heart Study Offspring adults (n=1502 participants, mean 67±9 years, 54% women) with available 1.5T CMR and transthoracic echocardiographic measures were included. Measures included proximal descending aortic strain and aortic arch pulse wave velocity by CMR (2002-2006) and diastolic function (mitral Doppler E and A wave velocity, E wave area, and LV tissue Doppler e' velocity) by echocardiography (2005-2008). Multivariable linear regression analysis was used to relate CMR aortic stiffness measures to measures of echocardiographic LV diastolic function. All continuous variables were standardized. In multivariable-adjusted regression analyses, aortic strain was inversely associated with E wave deceleration time (estimated β=-0.10±0.032, P=0.001), whereas aortic arch pulse wave velocity was inversely associated with E/A ratio (estimated β=-0.094±0.027, P=0.0006), E wave area (estimated β=-0.070±0.027, P=0.010), and e' (estimated β=-0.061±0.027, P=0.022), all indicating associations of higher aortic stiffness by CMR with less favorable LV diastolic function. Compared with men, women had a larger inverse relationship between pulse wave velocity and E/A ratio (interaction β=-0.085±0.031, P=0.0064). There was no significant effect modification by age or a U-shaped (quadratic) relation between aortic stiffness and LV diastolic function measures. Conclusions Higher proximal aortic stiffness is associated with less favorable LV diastolic function. Future studies may clarify temporal relations of aortic stiffness with varying patterns and progression of LV diastolic dysfunction.

Impaired aortic strain and distensibility by cardiac MRI in children with chronic kidney disease

Renal disease is associated with increased arterial stiffness. The aim was to investigate the effect of renal disease on regional aortic strain and distensibility in children with chronic kidney disease (CKD) by cardiac magnetic resonance imaging (MRI). The study included 30 children with CKD on hemodialysis, and ten healthy control subjects. Using cardiac MRI, maximal and minimal aortic areas were measured in axial cine steady state free precision images at the ascending aorta, proximal descending, and aorta at diaphragm. Regional strain and distensibility were calculated using previously validated formulas. Second reader aortic areas measurements were used to assess inter-observer agreement. Ascending aorta strain was significantly reduced in patients (38.4 ± 17.4%) compared to the control group (56.1 ± 17%), p-value 0.011. Ascending Aorta distensibility was significantly reduced in patients (9.1 ± 4.4 [× 10⁻³ mm Hg⁻¹]) compared to the control group (13.9 ± 4.9 [× 10⁻³ mm Hg⁻¹]), p-value 0.006. Strain and distensibility were reduced in proximal descending aorta and aorta at diaphragm but did not reach statistical significance. Only ascending aorta strain and distensibility had significant correlations with clinical and cardiac MRI parameters. Inter-observer agreement for strain and distensibility was almost perfect or strong in the three aortic regions. Aortic strain and distensibility by cardiac MRI are important imaging biomarkers for initial clinical evaluation and follow up of children with CKD.

Deep Learning-based Automated Aortic Area and Distensibility Assessment: the Multi-Ethnic Study of Atherosclerosis (MESA)

This study details application of deep learning for automatic segmentation of the ascending and descending aorta from 2D phase-contrast cine magnetic resonance imaging for automatic aortic analysis on the large MESA cohort with assessment on an external cohort of thoracic aortic aneurysm (TAA) patients. This study includes images and corresponding analysis of the ascending and descending aorta at the pulmonary artery bifurcation from the MESA study. Train, validation, and internal test sets consisted of 1123 studies (24,282 images), 374 studies (8067 images), and 375 studies (8069 images), respectively. The external test set of TAAs consisted of 37 studies (3224 images). CNN performance was evaluated utilizing a dice coefficient and concordance correlation coefficients (CCC) of geometric parameters. Dice coefficients were as high as 97.55% (CI: 97.47-97.62%) and 93.56% (CI: 84.63-96.68%) on the internal and external test of TAAs, respectively. CCC for maximum and minimum and ascending aortic area were 0.969 and 0.950, respectively, on the internal test set and 0.997 and 0.995, respectively, for the external test. The absolute differences between manual and deep learning segmentations for ascending and descending aortic distensibility were 0.0194 × 10^-4 ± 9.67 × 10^-4 and 0.002 ± 0.001 mmHg^-1, respectively, on the internal test set and 0.44 × 10^-4 ± 20.4 × 10^-4 and 0.002 ± 0.001 mmHg^-1, respectively, on the external test set. We successfully developed a U-Net-based aortic segmentation and analysis algorithm in both MESA and in external cases of TAA.

Effects of Exercise and Weight Loss on Proximal Aortic Stiffness in Older Adults With Obesity

BACKGROUND

Obesity may accelerate age-related increases in aortic stiffness. Although aerobic exercise training generally has favorable effects on aortic structure and function, exercise alone may not be sufficient to improve aortic stiffness in older adults with obesity. We determined the effects of aerobic exercise training with and without moderate- to high-caloric restriction (CR) on the structure and function of the proximal aorta in 160 older (65-79 years) men and women with obesity (body mass index=30-45 kg/m²).

METHODS

Participants were randomly assigned to 1 of 3 groups: aerobic exercise training only (treadmill 4 days/week for 30 minutes at 65% to 70% of heart rate reserve; n=56), aerobic exercise training plus moderate CR (n=55), or aerobic exercise training plus more intensive CR (n=49) for 20 weeks. Aortic pulse wave velocity, aortic distensibility, and other measures of aortic structure and function were assessed by cardiovascular magnetic resonance imaging. Pearson correlation coefficients were examined to assess associations between changes in proximal aortic stiffness and changes in fitness, fatness, and other potential confounders.

RESULTS

Weight loss in the aerobic exercise training plus moderate CR (-8.0 kg [95% CI, -9.17 to -6.87]) and aerobic exercise training plus more intensive CR (-8.98 kg [95% CI, -10.23 to -7.73) groups was significantly greater compared with the aerobic exercise training-only group (-1.66 kg [95% CI, -2.94 to -0.38]; P<0.017 for both). There were significant treatment effects for descending aorta distensibility (P=0.008) and strain (P=0.004) and aortic arch pulse wave velocity (P=0.01) with the aerobic exercise training plus moderate CR group having a 21% increase in distensibility (P=0.016) and an 8% decrease in pulse wave velocity (P=0.058). None of the aortic stiffness measures changed significantly in the aerobic exercise training-only or aerobic exercise training plus more intensive CR groups, and there were no significant changes in any other measure of aortic structure or function in these groups. Overall, increases in aortic distensibility were correlated with improvements in body weight and body fat distribution, but these associations were not statistically significant after adjustment for multiple comparisons.

CONCLUSIONS

In older adults with obesity, combining aerobic exercise with moderate CR leads to greater improvements in proximal aortic stiffness than exercise alone. Registration: URL: https://clinicaltrials.gov; Unique identifier: NCT01048736.

Circulatory efficiency in patients with severe aortic valve stenosis before and after aortic valve replacement

BACKGROUND

Circulatory efficiency reflects the ratio between total left ventricular work and the work required for maintaining cardiovascular circulation. The effect of severe aortic valve stenosis (AS) and aortic valve replacement (AVR) on left ventricular/circulatory mechanical power and efficiency is not yet fully understood. We aimed to quantify left ventricular (LV) efficiency in patients with severe AS before and after surgical AVR.

METHODS

Circulatory efficiency was computed from cardiovascular magnetic resonance (CMR) imaging derived volumetric data, echocardiographic and clinical data in patients with severe AS (n = 41) before and 4 months after AVR and in age and sex-matched healthy subjects (n = 10).

RESULTS

In patients with AS circulatory efficiency was significantly decreased compared to healthy subjects (9 ± 3% vs 12 ± 2%; p = 0.004). There were significant negative correlations between circulatory efficiency and LV myocardial mass (r = - 0.591, p < 0.001), myocardial fibrosis volume (r = - 0.427, p = 0.015), end systolic volume (r = - 0.609, p < 0.001) and NT-proBNP (r = - 0.444, p = 0.009) and significant positive correlation between circulatory efficiency and LV ejection fraction (r = 0.704, p < 0.001). After AVR, circulatory efficiency increased significantly in the total cohort (9 ± 3 vs 13 ± 5%; p < 0.001). However, in 10/41 (24%) patients, circulatory efficiency remained below 10% after AVR and, thus, did not restore to normal values. These patients also showed less reduction in myocardial fibrosis volume compared to patients with restored circulatory efficiency after AVR.

CONCLUSION

In our cohort, circulatory efficiency is reduced in patients with severe AS. In 76% of cases, AVR leads to normalization of circulatory efficiency. However, in 24% of patients, circulatory efficiency remained below normal values even after successful AVR. In these patients also less regression of myocardial fibrosis volume was seen. Trial Registration clinicaltrials.gov NCT03172338, June 1, 2017, retrospectively registered.

Variability of MRI Aortic Stiffness Measurements in a Multicenter Clinical Trial Setting: Intraobserver, Interobserver, and Intracenter Variability of Pulse Wave Velocity and Aortic Strain Measurement

PURPOSE

To assess intraobserver, interobserver, and scan-rescan variability of MRI aortic stiffness measurements in a multicenter trial setting.

MATERIALS AND METHODS

This study was a retrospective analysis of prospectively collected data in a multicenter prospective clinical trial (clinicaltrials.gov ID NCT01870739). Forty-five adult patients (31 men; mean age, 58 years ± 12 [standard deviation]; 15 patients per center; three centers) with arterial hypertension underwent standardized 3-T baseline MRI assessments between June and September 2014. Aortic strain was calculated from maximum and minimum aortic area measurements repeated three times by three readers at three aortic levels on three retrospectively gated axial gradient-echo (GRE) data sets. Pulse wave velocity (PWV) was assessed three times by five readers as Δx/Δt: Δx was measured on a parasagittal GRE image of the aortic arch, and Δt was extracted from ascending and descending aortic velocity curves created on three axial phase-contrast acquisitions. Intraobserver, interobserver, and scan-rescan variability was calculated using percentage coefficient of variation (COV).

RESULTS

Aortic strain variability was lowest at the level of the distal descending aorta (DDA) with median COVs of 1.6% for intraobserver variability, 4.0% for interobserver variability, and 10.3% for scan-rescan variability. It was highest at the ascending aorta (AA) with COVs of 3.6% for intraobserver variability, 10.7% for interobserver variability, and 19.8% for scan-rescan variability. Variability of PWV was low: 0.7% for intraobserver variability, 1.5% for interobserver variability, and 8.1% for scan-rescan variability.

CONCLUSION

Low variability can be achieved for aortic strain and PWV measurements in a multicenter trial setting using standardized MRI protocols. Although COV was lower when measuring aortic strain at DDA compared with AA, variability was acceptable at both anatomic locations.Supplemental material is available for this article.© RSNA, 2020.

Surrogates for myocardial power and power efficiency in patients with aortic valve disease

We aimed to assess surrogate markers for left ventricular (LV) myocardial power and efficiency in patients with isolated aortic stenosis (AS) and combined stenosis/regurgitation (AS/AR). In AS (n = 59), AS/AR (n = 21) and controls (n = 14), surrogates for LV myocardial power and circulatory/external myocardial efficiency were obtained from cardiac MRI. Median surrogate LV myocardial power was increased in AS, 7.7 W/m² (interquartile range 6.0–10.2; p = 0.010) and AS/AR, 10.8 W/m² (8.9–13.4; p < 0.001) when compared to controls, 5.4 W/m² (4.2–6.5), and was lower in AS than AS/AR (p < 0.001). Surrogate circulatory efficiency was decreased in AS, 8.6% (6.8–11.1; p < 0.001) and AS/AR, 5.4% (4.1–6.2; p < 0.001) when compared to controls, 11.8% (9.8–16.9). Surrogate external myocardial efficiency was higher in AS, 15.2% (11.9–18.6) than in AS/AR, 12.2% (10.1–14.2; p = 0.031) and was significantly lower compared to controls, 12.2% (10.7–18.1) in patients with reduced ejection fraction (EF), 9.8% (8.1–11.7; p = 0.025). In 16% of all cases, left ventricular mass/volume indices and EF were within normal ranges, wheras surrogate LV myocardial power was elevated and patients were symptomatic. Although influenced by pressure/volume load, the myocardium is additionally affected by remodelling processes. Surrogates for circulatory efficiency and LV myocardial power gradually reflect alterations in patients with AS and AS/AR, even when surrogate external myocardial efficiency, EF, mass and volume indices still remain compensated.

Obstructive Sleep Apnea and Structural/Functional Properties of the Thoracic Ascending Aorta: The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Structural and functional properties of the proximal thoracic aorta have important implications in clinical and subclinical cardiovascular disease (CVD). We examined whether obstructive sleep apnea (OSA) is associated with proximal aortic size and aortic stiffness in a multi-ethnic community-based cohort.

METHODS

The sample included the Multi-Ethnic Study of Atherosclerosis (MESA) Sleep Ancillary study participants without known CVD who underwent cardiac magnetic resonance imaging. The main exposure variable was OSA severity based on the polysomnography-derived apnea hypopnea index (AHI; normal, AHI <5/h; mild, 5≤ AHI <15/h; moderate to severe, AHI ≥15/h). The study outcomes were ascending aortic diameter (AoD, cm), aortic pulse wave velocity (AoPWV, m/s), and ascending aortic distensibility (AAD, %/mm Hg). Analyses were performed in the overall sample and in sex-specific strata, adjusted for multiple potential confounders.

RESULTS

The 708 participants were 55.9% female and on average 68 years old (54-93 years). There was a significant trend (p < 0.0001) of greater mean (SD) AoD across the three OSA groups: normal (n = 87), 3.13 cm (0.35); mild (n = 215), 3.25 (0.34); moderate to severe (n = 406), 3.37 (0.36). In adjusted analysis, participants with moderate to severe OSA had a greater mean AoD compared with the normal group: adjusted mean difference (95% CI), 0.12 cm (0.05, 0.20), p = 0.002. This AoD gradient was observed in women but not in men (p for interaction = 0.02). No differences were found in AoPWV or AAD among the OSA groups.

CONCLUSION

In a diverse community-based cohort, moderate to severe OSA (vs. no OSA) was associated with a larger ascending AoD in women.

Regional assessment of carotid artery pulse wave velocity using compressed sensing accelerated high temporal resolution 2D CINE phase contrast cardiovascular magnetic resonance

BACKGROUND

Cardiovascular magnetic resonance (CMR) allows for non-invasive assessment of arterial stiffness by means of measuring pulse wave velocity (PWV). PWV can be calculated from the time shift between two time-resolved flow curves acquired at two locations within an arterial segment. These flow curves can be derived from two-dimensional CINE phase contrast CMR (2D CINE PC CMR). While CMR-derived PWV measurements have proven to be accurate for the aorta, this is more challenging for smaller arteries such as the carotids due to the need for both high spatial and temporal resolution. In this work, we present a novel method that combines retrospectively gated 2D CINE PC CMR, high temporal binning of data and compressed sensing (CS) reconstruction to accomplish a temporal resolution of 4 ms. This enables accurate flow measurements and assessment of PWV in regional carotid artery segments.

METHODS

Retrospectively gated 2D CINE PC CMR data acquired in the carotid artery was binned into cardiac frames of 4 ms length, resulting in an incoherently undersampled ky-t-space with a mean undersampling factor of 5. The images were reconstructed by a non-linear CS reconstruction using total variation over time as a sparsifying transform. PWV values were calculated from flow curves by using foot-to-foot and cross-correlation methods. Our method was validated against ultrasound measurements in a flow phantom setup representing the carotid artery. Additionally, PWV values of two groups of 23 young (30 ± 3 years, 12 [52%] women) and 10 elderly (62 ± 10 years, 5 [50%] women) healthy subjects were compared using the Wilcoxon rank-sum test.

RESULTS

Our proposed method produced very similar flow curves as those measured using ultrasound at 1 ms temporal resolution. Reliable PWV estimation proved possible for transit times down to 7.5 ms. Furthermore, significant differences in PWV values between healthy young and elderly subjects were found (4.7 ± 1.0 m/s and 7.9 ± 2.4 m/s, respectively; p < 0.001) in accordance with literature.

CONCLUSIONS

Retrospectively gated 2D CINE PC CMR with CS allows for high spatiotemporal resolution flow measurements and accurate regional carotid artery PWV calculations. We foresee this technique will be valuable in protocols investigating early development of carotid atherosclerosis.

Relation of Sex Hormone Levels With Prevalent and 10-Year Change in Aortic Distensibility Assessed by MRI: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Women experience a steeper decline in aortic elasticity related to aging compared to men. We examined whether sex hormone levels were associated with ascending aortic distensibility (AAD) in the Multi-Ethnic Study of Atherosclerosis.

METHODS

We studied 1,345 postmenopausal women and 1,532 men aged 45-84 years, who had serum sex hormone levels, AAD measured by phase-contrast cardiac magnetic resonance imaging, and ejection fraction>50% at baseline. Among these participants, 457 women and 548 men returned for follow-up magnetic resonance imaging 10-years later. Stratified by sex, and using mixed effects linear regression methods, we examined associations of sex hormones (as tertiles) with baseline and annual change in log-transformed AAD (mm Hg-110-3), adjusting for demographics, body size, lifestyle factors, mean arterial pressure, heart rate, hypertensive medication use (and in women, for hormone therapy use and years since menopause).

RESULTS

The mean (SD) age was 65 (9) for women and 62 (10) years for men. AAD was lower in women than men (P < 0.001). In adjusted cross-sectional analysis, the highest tertile of free testosterone (compared to lowest) in women was significantly associated with lower AAD [-0.10 (-0.19, -0.01)] and the highest tertile of estradiol in men was associated with greater AAD [0.12 (0.04, 0.20)]. There were no associations of sex hormones with change in AAD over 10 years, albeit in a smaller sample size.

CONCLUSIONS

Lower free testosterone in women and higher estradiol in men were associated with greater aortic distensibility at baseline, but not longitudinally. Sex hormone levels may account for differences in AAD between women and men.

Imaging Insights on the Aorta in Aging

The aorta has 2 main functions, conduit and cushion, and is designed to transmit blood to the periphery and buffer pulsatile stress from ventricular contraction. In the interaction between the structural and functional changes of the aorta, aging and disease processes impact on aortic material properties and hemodynamics. For a comprehensive assessment of changes in aortic structure and function associated with aging and disease, noninvasive cardiovascular imaging techniques, especially magnetic resonance imaging, have recently been developed. Magnetic resonance imaging allows for direct and accurate measurement of different aortic characteristics including structural measures such as aortic area or volume, aortic length, curvature, and aortic wall thickness and functional measures such as aortic strain, distensibility, and pulse wave velocity. Excellent reproducibility of magnetic resonance imaging methods allows us to assess the response of the whole aorta to both pharmacological and nonpharmacological therapies. Aortic flow and functional assessment could be added to clinical routine cardiac magnetic resonance as a comprehensive imaging modality primarily performed for the noninvasive evaluation of left ventricular function, left ventricular load, and vascular/ventricular coupling. New techniques such as 4-dimensional flow could provide and further elucidate the combined age-related effects of altered aortic geometry and function. This following review will describe the pathophysiological aspects of the aorta and the ability, value, and prospects of cardiovascular imaging, especially magnetic resonance imaging, to study age-related changes in aortic structure and function and assess the relationship between these alterations and cardiovascular disease.

Renal sympathetic denervation restores aortic distensibility in patients with resistant hypertension: data from a multi-center trial

Renal sympathetic denervation (RDN) is under investigation as a treatment option in patients with resistant hypertension (RH). Determinants of arterial compliance may, however, help to predict the BP response to therapy. Aortic distensibility (AD) is a well-established parameter of aortic stiffness and can reliably be obtained by CMR. This analysis sought to investigate the effects of RDN on AD and to assess the predictive value of pre-treatment AD for BP changes. We analyzed data of 65 patients with RH included in a multicenter trial. RDN was performed in all participants. A standardized CMR protocol was utilized at baseline and at 6-month follow-up. AD was determined as the change in cross-sectional aortic area per unit change in BP. Office BP decreased significantly from 173/92 ± 24/16 mmHg at baseline to 151/85 ± 24/17 mmHg (p < 0.001) 6 months after RDN. Maximum aortic areas increased from 604.7 ± 157.7 to 621.1 ± 157.3 mm² (p = 0.011). AD improved significantly by 33% from 1.52 ± 0.82 to 2.02 ± 0.93 × 10⁻³ mmHg⁻¹ (p < 0.001). Increase of AD at follow-up was significantly more pronounced in younger patients (p = 0.005) and responders to RDN (p = 0.002). Patients with high-baseline AD were significantly younger (61.4 ± 10.1 vs. 67.1 ± 8.4 years, p = 0.022). However, there was no significant correlation of baseline AD to response to RDN. AD is improved after RDN across all age groups. Importantly, these improvements appear to be unrelated to observed BP changes, suggesting that RDN may have direct effects on the central vasculature.

Longitudinal assessment of marrow fat content using three-point Dixon technique in osteoporotic rabbits

OBJECTIVE

In this longitudinal pilot study, we aimed to investigate the intra-, interobserver, and scan-rescan reproducibility of marrow fat fraction (FF) measurements using three-point Dixon imaging in osteoporotic rabbits: comparison with histopathology.

METHODS

Twenty female rabbits were randomly assigned to sham-operation and ovariectomy in combination with daily methylprednisolone hemisuccinate groups (n = 10 per group). Marrow FF by three-point Dixon technique and bone density by dual-energy x-ray absorptiometry were assessed at baseline, 6 and 12 weeks after operation. Intra-, inter-reader, and scan-rescan reliability of FF measurements were evaluated using intraclass correlation coefficient (ICC) and Bland-Altman 95% limit of agreement. Histomorphometry was performed to quantify marrow adipocyte parameters.

RESULTS

Intra- and inter-reader reproducibility of FF measurements was "substantial" (ICC = 0.984 and 0.978, respectively). Although the ICC for scan-rescan reliability was excellent (ICC = 0.962), increased measurement variability was observed using Bland-Altman plot. Relative to the sham-operated rabbits, the adipocytes mean diameter, density, and percent adipocytes area in the osteoporotic rabbits increased by 23.4%, 68.9%, and 117.0%, respectively. Marrow FF was positively correlated with the quantitative parameters of adipocytes, particularly with percent adipocyte area, but inversely associated with bone density. At the relatively early stage, the percentage of bone loss was similar to that of elevated fatty marrow in the osteoporotic rabbits; at the later stage, the change for the latter outweighed that of the former.

CONCLUSIONS

Results of three-point Dixon technique demonstrated a very reproducible manner within and between observers and acceptable scan-rescan performance in the assessment of marrow fat in rabbits.

Cardiovascular magnetic resonance in an adult human population: serial observations from the multi-ethnic study of atherosclerosis

The Multi-Ethnic Study of Atherosclerosis (MESA) is the first large-scale multi-ethnic population study in the U.S. to use advanced cardiovascular magnetic resonance (CMR) imaging. MESA participants were free of cardiovascular disease at baseline between 2000 and 2002, and were followed up between 2009 and 2011 with repeated CMR examinations as part of MESA. CMR allows the clinician to visualize and accurately quantify volume and dimensions of all four cardiac chambers; measure systolic and diastolic ventricular function; assess myocardial fibrosis; assess vessel lumen size, vessel wall morphology, and vessel stiffness. CMR has a number of advantages over other imaging modalities such as echocardiography, computed tomography, and invasive angiography, and has been proposed as a diagnostic strategy for high-risk populations. MESA has been extensively evaluating CMR imaging biomarkers, as markers of subclinical disease, in the last 15 years for low-risk populations. On a more practical level, some of the imaging biomarkers developed and studied are translatable to at-risk populations. In this review, we discuss the progression of subclinical cardiovascular disease and the mechanisms responsible for the transition to symptomatic clinical outcomes based on our findings from MESA.

Aortic Arch Pulse Wave Velocity Assessed by Magnetic Resonance Imaging as a Predictor of Incident Cardiovascular Events: The MESA (Multi-Ethnic Study of Atherosclerosis)

The predictive value of aortic arch pulse wave velocity (PWV) assessed by magnetic resonance imaging for cardiovascular disease (CVD) events has not been fully established. The aim of the present study was to evaluate the association of arch PWV with incident CVD events in MESA (Multi-Ethnic Study of Atherosclerosis). Aortic arch PWV was measured using magnetic resonance imaging at baseline in 3527 MESA participants (mean age, 62±10 years at baseline; 47% men) free of overt CVD. Cox regression was used to evaluate the risk of incident CVD (coronary heart disease, stroke, transient ischemic attack, or heart failure) in relation to arch PWV adjusted for age, sex, race, and CVD risk factors. The median value of arch PWV was 7.4 m/s (interquartile range, 5.6-10.2). There was significant interaction between arch PWV and age for outcomes, so analysis was stratified by age categories (45-54 and >54 years). There were 456 CVD events during the 10-year follow-up. Forty-five to 54-year-old participants had significant association of arch PWV with incident CVD independent of CVD risk factors (hazard ratio, 1.44; 95% confidence interval, 1.07-1.95; P=0.018; per 1-SD increase for logarithmically transformed PWV), whereas >54-year group did not (P=0.93). Aortic arch PWV assessed by magnetic resonance imaging is a significant predictor of CVD events among middle-aged (45-54 years old) individuals, whereas arch PWV is not associated with CVD among an elderly in a large multiethnic population.

Ideal Cardiovascular Health, Cardiovascular Remodeling, and Heart Failure in Blacks: The Jackson Heart Study

BACKGROUND

The lifetime risk of heart failure (HF) is higher in the black population than in other racial groups in the United States.

METHODS AND RESULTS

We measured the Life's Simple 7 ideal cardiovascular health metrics in 4195 blacks in the JHS (Jackson Heart Study; 2000-2004). We evaluated the association of Simple 7 metrics with incident HF and left ventricular structure and function by cardiac magnetic resonance (n=1188). Mean age at baseline was 54.4 years (65% women). Relative to 0 to 2 Simple 7 factors, blacks with 3 factors had 47% lower incident HF risk (hazard ratio [HR], 0.53; 95% confidence interval [CI], 0.39-0.73; P<0.0001); and those with ≥4 factors had 61% lower HF risk (HR, 0.39; 95% CI, 0.24-0.64; P=0.0002). Higher blood pressure (HR, 2.32; 95% CI, 1.28-4.20; P=0.005), physical inactivity (HR, 1.65; 95% CI, 1.07-2.55; P=0.02), smoking (HR, 2.04; 95% CI, 1.43-2.91; P<0.0001), and impaired glucose control (HR, 1.76; 95% CI, 1.34-2.29; P<0.0001) were associated with incident HF. The age-/sex-adjusted population attributable risk for these Simple 7 metrics combined was 37.1%. Achievement of ideal blood pressure, ideal body mass index, ideal glucose control, and nonsmoking was associated with less likelihood of adverse cardiac remodeling by cardiac magnetic resonance.

CONCLUSIONS

Cardiovascular risk factors in midlife (specifically elevated blood pressure, physical inactivity, smoking, and poor glucose control) are associated with incident HF in blacks and represent targets for intensified HF prevention.

The importance of accurate measurement of aortic stiffness in patients with chronic kidney disease and end-stage renal disease

Cardiovascular (CV) disease is the leading cause of death in chronic kidney disease (CKD) and end-stage renal disease (ESRD). A key driver in this pathology is increased aortic stiffness, which is a strong, independent predictor of CV mortality in this population. Aortic stiffening is a potentially modifiable biomarker of CV dysfunction and in risk stratification for patients with CKD and ESRD. Previous work has suggested that therapeutic modification of aortic stiffness may ameliorate CV mortality. Nevertheless, future clinical implementation relies on the ability to accurately and reliably quantify stiffness in renal disease. Pulse wave velocity (PWV) is an indirect measure of stiffness and is the accepted standard for non-invasive assessment of aortic stiffness. It has typically been measured using techniques such as applanation tonometry, which is easy to use but hindered by issues such as the inability to visualize the aorta. Advances in cardiac magnetic resonance imaging now allow direct measurement of stiffness, using aortic distensibility, in addition to PWV. These techniques allow measurement of aortic stiffness locally and are obtainable as part of a comprehensive, multiparametric CV assessment. The evidence cannot yet provide a definitive answer regarding which technique or parameter can be considered superior. This review discusses the advantages and limitations of non-invasive methods that have been used to assess aortic stiffness, the key studies that have assessed aortic stiffness in patients with renal disease and why these tools should be standardized for use in clinical trial work.

Association of Aortic Stiffness With Left Ventricular Remodeling and Reduced Left Ventricular Function Measured by Magnetic Resonance Imaging: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

This study sought to assess cross-sectional associations of aortic stiffness assessed by magnetic resonance imaging with left ventricular (LV) remodeling and myocardial deformation in the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS AND RESULTS

Aortic arch pulse wave velocity (PWV) was measured with phase contrast cine magnetic resonance imaging. LV circumferential strain (Ecc), torsion, and early diastolic strain rate were determined by tagged magnetic resonance imaging. Multivariable linear regression models were used to adjust for demographics and cardiovascular risk factors. Of 2093 participants, multivariable linear regression models demonstrated that higher arch PWV was associated with higher LV mass index (B=0.53 per 1 SD increase for log-transformed PWV, P<0.05) and LV mass to volume ratio (B=0.015, P<0.01), impaired LV ejection fraction (LVEF; B=-0.84; P<0.001), Ecc (B=0.55; P<0.001), torsion (B=-0.11; P<0.001), and early diastolic strain rate (B=-0.003; P<0.05). In sex stratified analysis, higher arch PWV was associated with higher MVR (B=0.02; P<0.05), impaired Ecc (B=0.60; P<0.001), and LVEF (B=-0.45; P<0.05), but with maintained torsion in women. Higher PWV was associated with impaired Ecc (B=0.49; P<0.001) and LVEF (B=-1.21; P<0.001), with lower torsion (B=-0.17; P<0.001) in men.

CONCLUSIONS

Higher arch PWV is associated with LV remodeling, and reduced LV systolic and diastolic function in a large multiethnic population. Greater aortic arch stiffness is associated with concentric LV remodeling and relatively preserved LVEF with maintained torsion in women, whereas greater aortic arch stiffness is associated with greater LV dysfunction demonstrated as impaired Ecc, torsion, and LVEF, with less concentric LV remodeling in men.

Ten-year longitudinal change in aortic stiffness assessed by cardiac MRI in the second half of the human lifespan: the multi-ethnic study of atherosclerosis

AIMS

Longitudinal determinants of aortic stiffness (AS) measured by magnetic resonance imaging (MRI) have not been assessed in a large community-based population. Our aim was to examine the determinants of change in thoracic AS over 10 years of follow-up in a multi-ethnic population of individuals 45 years of age and older measured by MRI.

METHODS AND RESULTS

We studied 1160 participants (mean age = 60 ± 9 years at baseline, 45% male) with aortic MRI at both the MESA Year 0 and Year 10 examinations. Ascending and descending aorta distensibility (AAD/DAD) and aortic arch pulse-wave velocity (PWV) were measured using MRI. Determinants of the change in AS parameters over 10 years were assessed using linear regression adjusted for baseline values, demographic variables, baseline risk factors and change in risk factors, and chronic risk exposure. AAD and DAD decreased slightly (5% decrease in median for AAD: 1.33-1.26 mmHg(-1) · 10(-3), P = 0.008; 5% decrease in median for DAD: 1.73-1.64 mmHg(-1) · 10(-3), P < 0.001), and PWV increased over 10 years (18% increase in median: 6.8-8.0 m/s P < 0.001). Baseline age was related to a reduction in AAD and DAD and an increase in PWV throughout the follow-up period. Baseline and change in mean blood pressure and continued smoking were associated with a reduction in AAD and an increase in PWV. Furthermore, baseline heart rate was also related to a reduction in AAD and DAD. Blood pressure normalization was related to less aortic stiffening throughout the follow-up period.

CONCLUSIONS

In our longitudinal, community-based cohort study of adult individuals aged 45 years or greater, greater mean blood pressure and a history of smoking history were associated with increased aortic stiffening over 10 years as assessed by MRI.