The association between cardiovascular risk and cardiovascular magnetic resonance measures of fibrosis: the Multi-Ethnic Study of Atherosclerosis (MESA).

BACKGROUND: Risk scores for cardiovascular disease (CVD) are in common use to integrate multiple cardiovascular risk factors in order to identify individuals at greatest risk for disease. The purpose of this study was to determine if individuals at greater cardiovascular risk have T1 mapping indices by cardiovascular magnetic resonance (CMR) indicative of greater myocardial fibrosis. METHODS: CVD risk scores for 1208 subjects (men, 50.8%) ages 55-94 years old were evaluated in the Multiethnic Study of Atherosclerosis (MESA) at six centers. T1 times were determined at 1.5Tesla before and after gadolinium administration (0.15 mmol/kg) using a modified Look-Locker pulse sequence. The relationship between CMR measures (native T1, 12 and 25 minute post-gadolinium T1, partition coefficient and extracellular volume fraction) and 14 established different cardiovascular risk scores were determined using regression analysis. Bootstrapping analysis with analysis of variance was used to compare different CMR measures. CVD risk scores were significantly different for men and women (p < 0.001). RESULTS: 25 minute post gadolinium T1 time showed more statistically significant associations with risk scores (10/14 scores, 71%) compared to other CMR indices (e.g. native T1 (7/14 scores, 50%) and partition coefficient (7/14, 50%) in men. Risk scores, particularly the new 2013 AHA/ASCVD risk score, did not correlate with any CMR fibrosis index. CONCLUSIONS: Men with greater CVD risk had greater CMR indices of myocardial fibrosis. T1 times at greater delay time (25 minutes) showed better agreement with commonly used risk score indices compared to ECV and native T1 time. CLINICAL TRIAL REGISTRATION: http://www.mesa-nhlbi.org/, NCT00005487.

Impact of Abdominal Obesity on Proximal and Distal Aorta Wall Thickness in African Americans: The Jackson Heart Study.

OBJECTIVE: Abdominal obesity and wall thickness of the central arteries have been associated with higher risk of cardiovascular disease. Despite the higher burden of overweight and cardiovascular disease among African Americans, limited data are available on the association of abdominal obesity with aortic wall thickness in African Americans. We assessed the cross-sectional and the longitudinal associations of abdominal obesity with aortic intima-media thickness (aIMT) in a cohort of African Americans from the Jackson Heart Study. METHODS: Data on aIMT and repeated measures of waist circumference (WC) and waist to height ratio from 1,572 participants, as well as on abdominal subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and aIMT from 1,223 participants, were analyzed. aIMT was measured at proximal ascending aorta (PA-aIMT), proximal descending aorta (PD-aIMT), and distal aorta (bifurcation) using cardiac magnetic resonance. SAT and VAT were measured using computerized tomography. RESULTS: WC and WHtR were longitudinally associated with PA-aIMT and PD-aIMT; SAT and VAT were associated with PA-aIMT only. Only WC was associated with distal aIMT. CONCLUSIONS: Abdominal obesity measures are associated with increased proximal aIMT in adult African Americans. Only WC is associated with wall thickness in all three segments of the aorta.

Association of myocardial fibrosis and cardiovascular events: the multi-ethnic study of atherosclerosis.

Aims: We used contrast-enhanced cardiac magnetic resonance (CMR) to evaluate differences in myocardial fibrosis measured at the year-10 examination between participants with and without cardiovascular (CV) events accrued in a large population based study over the preceding 10-year follow-up period in this retrospective study. Methods and results: The MESA study enrolled 6814 participants free of CV disease at baseline (2000-2002). We included MESA participants who underwent contrast-enhanced CMR at the MESA year-10 exam (N = 1840). We defined a composite CV endpoint of coronary heart disease, heart failure, atrial fibrillation, stroke, and peripheral artery disease. Using CMR, we characterized myocardial fibrosis with late-gadolinium enhancement for scar and T1 mapping indices of diffuse fibrosis. Demographic and CV-risk adjusted logistic (presence of scar) and linear regression (pre-contrast T1, T1 at 12 and 25 min post-contrast, and extracellular volume fraction or ECV) models were used to assess the relationship between fibrosis and events. The mean values of T1 indices were-pre-contrast T1: 977 ± 45 ms; T1 at 12': 456 ± 40 ms; T1 at 25': 519 ± 41 ms; ECV: 27.1 ± 3.2%. One-hundred and forty-six (7.9%) participants had myocardial scar. The presence of scar was strongly associated with prior CV events (adjusted coeff: 1.36, P < 0.001). Lower post-contrast T1 times and higher ECV, indicative of greater diffuse fibrosis were strongly associated with CV events (T1 at 12': coeff = -10.0 ms, P = 0.004; T1 at 25': coeff =-9.2 ms, P = 0.008; ECV: coeff = 1.31%, P < 0.001). Conclusion: Individuals who suffered prior CV events have greater likelihood of diffuse myocardial fibrosis when compared with event-free individuals living in the same community.

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

AIMS: To assess the test-retest, intra- and inter-reader reliability of thoracic aorta measurements by magnetic resonance imaging (MRI). METHODS AND RESULTS: Twenty-five participants underwent aortic MRI twice over 13 ± 7 days. All aortic variables from baseline and repeat MR were analysed using a semi-automated method by the ARTFUN software. To assess the inter-study reproducibility of aortic variables, we calculated intraclass correlation coefficient (ICC) for individual aortic measurements. Intra- and inter-observer variability was also assessed using the baseline MR data. Mean ascending aortic strain had moderate inter-study reproducibility (11.53 ± 6.44 vs. 10.55 ± 6.64, P = 0.443, ICC = 0.53, P < 0.01). Mean descending aortic strain and arch pulse wave velocity (PWV) had good inter-study reproducibility (descending aortic strain: 8.65 ± 5.30 vs. 8.35 ± 5.26, P = 0.706, ICC = 0.74, P < 0.001; PWV: 9.92 ± 4.18 vs. 9.94 ± 4.55, P = 0.968, ICC = 0.77, P < 0.001, respectively). All aortic variables had excellent intra- and inter-observer reproducibility (intra-: ICC range, 0.87-0.99, inter-: ICC range, 0.56-0.99, respectively). CONCLUSION: Inter-study reproducibility of all aortic variables was acceptable. Intra- and inter-observer reproducibility of all aortic variables was excellent. MRI can provide a repeatable method of measuring aortic structural and functional parameters.

Diastolic function assessed from tagged MRI predicts heart failure and atrial fibrillation over an 8-year follow-up period: the multi-ethnic study of atherosclerosis.

OBJECTIVES: The strain relaxation index (SRI), a novel diastolic functional parameter derived from tagged magnetic resonance imaging (MRI), is used to assess myocardial deformation during left ventricular relaxation. We investigated whether diastolic function indexed by SRI predicts heart failure (HF) and atrial fibrillation (AF) over an 8-year follow-up. METHODS: As a part of the multi-ethnic study of atherosclerosis, 1544 participants free of known cardiovascular disease (CVD) underwent tagged MRI in 2000-02. Harmonic phase analysis was used to compute circumferential strain. Standard parameters, early diastolic strain rate (EDSR) and the peak torsion recoil rate were calculated. An SRI was calculated as difference between post-systolic and systolic times of the strain peaks, divided by the EDSR peak. It was normalized by the total interval of relaxation. Over an 8-year follow-up period, we defined AF (n = 57) or HF (n = 36) as combined (n = 80) end-points. Cox regression assessed the ability of SRI to predict events adjusted for risk factors and markers of subclinical disease. Integrated discrimination index (IDI) and net reclassification index (NRI) of SRI, compared with conventional indices, were also assessed. RESULTS: The hazard ratio for SRI remained significant for the combined HF and AF end-points as well as for HF alone after adjustment. For the combined end-point, IDI was 1.5% (P < 0.05) and NRI was 11.4% (P < 0.05) for SRI. Finally, SRI was more robust than all other existing cardiovascular magnetic resonance diastolic functional parameters. CONCLUSION: SRI predicts HF and AF over an 8-year follow-up period in a large population free of known CVD, independent of established risk factors and markers of subclinical CVD.

Proximal aortic distensibility is an independent predictor of all-cause mortality and incident CV events: the MESA study.

BACKGROUND: The predictive value of ascending aortic distensibility (AAD) for mortality and hard cardiovascular disease (CVD) events has not been fully established. OBJECTIVES: This study sought to assess the utility of AAD to predict mortality and incident CVD events beyond conventional risk factors in MESA (Multi-Ethnic Study of Atherosclerosis). METHODS: AAD was measured with magnetic resonance imaging at baseline in 3,675 MESA participants free of overt CVD. Cox proportional hazards regression was used to evaluate risk of death, heart failure (HF), and incident CVD in relation to AAD, CVD risk factors, indexes of subclinical atherosclerosis, and Framingham risk score. RESULTS: There were 246 deaths, 171 hard CVD events (myocardial infarction, resuscitated cardiac arrest, stroke and CV death), and 88 HF events over a median 8.5-year follow-up. Decreased AAD was associated with increased all-cause mortality with a hazard ratio (HR) for the first versus fifth quintile of AAD of 2.7 (p = 0.008) independent of age, sex, ethnicity, other CVD risk factors, and indexes of subclinical atherosclerosis. Overall, patients with the lowest AAD had an independent 2-fold higher risk of hard CVD events. Decreased AAD was associated with CV events in low to intermediate- CVD risk individuals with an HR for the first quintile of AAD of 5.3 (p = 0.03) as well as with incident HF but not after full adjustment. CONCLUSIONS: Decreased proximal aorta distensibility significantly predicted all-cause mortality and hard CV events among individuals without overt CVD. AAD may help refine risk stratification, especially among asymptomatic, low- to intermediate-risk individuals.

Pericardial adipose tissue, atherosclerosis, and cardiovascular disease risk factors: the Jackson heart study.

OBJECTIVE: Pericardial adipose tissue (PAT), a regional fat depot that surrounds the heart, is associated with an unfavorable cardiometabolic risk factor profile. The associations among PAT, cardiometabolic risk factors, and coronary artery calcification (CAC) and abdominal aortic artery calcification (AAC) in African American populations have not been explored. RESEARCH DESIGN AND METHODS: A total of 1,414 African Americans (35% men; mean +/- SD age 58 +/- 11 years) drawn from the Jackson Heart Study (JHS) underwent multidetector computed tomography assessment of abdominal visceral adipose tissue (VAT) and PAT between 2007 and 2009. Cardiometabolic risk factors, CAC, and AAC were examined in relation to increments of PAT and VAT. RESULTS: PAT was significantly correlated with BMI, waist circumference, and VAT (r = 0.35, 0.46, and 0.69; all P < 0.0001). PAT (per 1-SD increase) was associated with elevated levels of systolic blood pressure (P < 0.04), fasting glucose, triglycerides, and C-reactive protein and lower levels of HDL (all P values<0.0001). PAT was also associated with metabolic syndrome (odds ratio [OR] 1.89; P < 0.0001), hypertension (1.48; P < 0.0006), and diabetes (1.40; P < 0.04); all associations were diminished after further adjustment for VAT (most P > 0.05). However, the association of PAT with CAC but not with AAC remained significant (OR 1.34 [95% CI 1.10-1.64]; P < 0.004) after multivariable and VAT adjustment. CONCLUSIONS: PAT is significantly correlated with most cardiometabolic risk factors and CAC in the JHS cohort. The results suggest that PAT is an important VAT depot that may exert a local effect on the coronary vasculature.

Left ventricular papillary muscle mass: relationship to left ventricular mass and volumes by magnetic resonance imaging.

OBJECTIVE: To evaluate the effect of papillary muscle mass on the calculation of left ventricular (LV) function and mass and to determine the relationship between papillary muscle mass with body size and sex. METHODS: Cardiac magnetic resonance imaging examinations from 50 men and 50 women were randomly selected from the Multi-Ethnic Study of Atherosclerosis database. The contours of the papillary muscles were traced manually, and the LV wall contours were outlined semiautomatically based on short-axis images. Papillary muscle mass, LV mass, and volumes were calculated. RESULTS: Inclusion of the papillary muscles results in significantly higher total LV mass values (P<0.001) and lower end-diastolic volume values (P<0.001) compared with measurements excluding papillary muscles from the LV mass. Papillary muscle mass accounts for 8.9% of the total LV mass and is correlated with LV wall mass (r=0.81, P<0.001). CONCLUSION: Papillary muscle mass significantly affects LV volumes and mass determined by cine magnetic resonance imaging.