Gender specific patterns of age-related decline in aortic stiffness: a cardiovascular magnetic resonance study including normal ranges.

BACKGROUND: Young females exhibit lower cardiovascular event rates that young men, a pattern which is lost, or even reversed with advancing age. As aortic stiffness is a powerful risk factor for cardiovascular events, a gender difference with advancing age could provide a plausible explanation for this pattern. METHODS: 777 subjects (♀n = 408, ♂n = 369) across a wide range of age (21-85 years) underwent cardiovascular magnetic resonance to assess aortic pulse wave velocity (PWV) and, in addition, aortic distensibility at three levels; 1) ascending aorta (Ao) and 2) proximal descending aorta (PDA) at the level of the pulmonary artery and 3) the abdominal aorta (DDA). RESULTS: There was a strong negative correlation between increasing age and regional aortic distensibility (Ao♀R-0.84, ♂R-0.80, PDA♀R-0.82, ♂R-0.77, DDA♀R-0.80, ♂R-0.71 all p < 0.001) and a strong positive correlation with PWV, (♀R0.53, ♂R 0.63 both p < 0.001). Even after adjustment for mean arterial pressure, body mass index, heart rate, smoking and diabetes, females exhibited a steeper decrease in all distensibility measures in response to increasing age (Ao♀-1.3 vs ♂-1.1 mmHg-1, PDA ♀-1.2 vs ♂-1.0 mmHg, DDA ♀-1.8 vs ♂-1.4 mmHg-1 per 10 years increase in age all p < 0.001). No gender difference in PWV increase with age was observed (p = 0.11). CONCLUSION: Although advancing age is accompanied by increased aortic stiffness in both males and females, a significant sex difference in the rate of change exists, with females showing a steeper decline in aortic elasticity. As aortic stiffness is strongly related to cardiovascular events our observations may explain the increase in cardiovascular event rates that accompanies the menopausal age in women.

Observational study of regional aortic size referenced to body size: production of a cardiovascular magnetic resonance nomogram.

BACKGROUND: Cardiovascular magnetic resonance (CMR) is regarded as the gold standard for clinical assessment of the aorta, but normal dimensions are usually referenced to echocardiographic and computed tomography data and no large CMR normal reference range exists. As a result we aimed to 1) produce a normal CMR reference range of aortic diameters and 2) investigate the relationship between regional aortic size and body surface area (BSA) in a large group of healthy subjects with no vascular risk factors. METHODS: 447 subjects (208 male, aged 19-70 years) without identifiable cardiac risk factors (BMI range 15.7-52.6 kg/m2) underwent CMR at 1.5 T to determine aortic diameter at three levels: the ascending aorta (Ao) and proximal descending aorta (PDA) at the level of the pulmonary artery, and the abdominal aorta (DDA), at a level 12 cm distal to the PDA. In addition, 201 of these subjects had aortic root imaging, allowing for measurements at the level of the aortic valve annulus (AV), aortic sinuses and sinotubular junction (STJ). RESULTS: Normal diameters (mean ±2 SD) were; AV annulus male(♂) 24.4 ± 5.4, female (♀) 21.0 ± 3.6 mm, aortic sinus♂ 32.4 ± 7.7, ♀27.6 ± 5.8 mm, ST-junction ♂25.0 ± 7.4, ♀21.8 ± 5.4 mm, Ao ♂26.7 ± 7.7, ♀25.5 ± 7.4 mm, PDA ♂20.6 ± 5.6, +18.9 ± 4.0 mm, DDA ♂17.6 ± 5.1, ♀16.4 ± 4.0 mm. Aortic root and thoracic aortic diameters increased at all levels measured with BSA. No gender difference was seen in the degree of dilatation with increasing BSA (p>0.5 for all analyses). CONCLUSION: Across both genders, increasing body size is characterized by a modest degree of aortic dilatation, even in the absence of traditional cardiovascular risk factors.

Gender-specific differences in left ventricular remodelling in obesity: insights from cardiovascular magnetic resonance imaging.

AIMS: As obesity-related cardiovascular mortality, although elevated when compared with normal weight, is lower in females than in males at every body mass index (BMI) level, we aimed to investigate gender-specific differences in left ventricular (LV) hypertrophy in obesity, which themselves have been shown to have varying prognostic value. METHOD AND RESULTS: In total, 741 subjects (female, n = 399) without identifiable cardiovascular risk factors (BMI 15.7-59.2 kg/m(2)) underwent cardiovascular magnetic resonance (1.5 T) to determine LV mass, end-diastolic volume (EDV, mL), and LV mass/volume ratio (LVM/VR). Across both sexes, there was a strong positive correlation between BMI and LV mass (male r = 0.44, female r = 0.57, both P < 0.001), with males showing a greater LV hypertrophic response (male +2.3 vs. female +1.6 g per BMI point increase, P = 0.001). Concentric hypertrophy was present in both sexes and LVM/VR positively correlated to BMI (male r = 0.45, female r = 0.29, both P < 0.001) on linear regression analysis. However, the degree of concentric hypertrophy was greater in males (male +0.13 vs. female +0.06 LVM/VR increase per BMI point increase, P = 0.001). On the other hand, females showed a greater LV cavity dilatory response (female +1.1 vs. male +0.3 mL per BMI point increase, P < 0.001). Indeed, in contrast to females, where BMI and LV-EDV were positively correlated (r = 0.38, P < 0.001), BMI did not correlate with EDV in men (r = 0.03, P = 0.62). CONCLUSION: In the absence of traditional cardiovascular risk factors, obese men show predominantly concentric hypertrophy, whereas obese women exhibit both eccentric and concentric hypertrophy. As concentric hypertrophy is more strongly related to cardiovascular mortality than eccentric hypertrophy, our observations may explain the observed gender difference in obesity-related mortality.

Heritability of haemodynamics in the ascending aorta.

Blood flow in the vasculature can be characterised by dimensionless numbers commonly used to define the level of instabilities in the flow, for example the Reynolds number, Re. Haemodynamics play a key role in cardiovascular disease (CVD) progression. Genetic studies have identified mechanosensitive genes with causal roles in CVD. Given that CVD is highly heritable and abnormal blood flow may increase risk, we investigated the heritability of fluid metrics in the ascending aorta calculated using patient-specific data from cardiac magnetic resonance (CMR) imaging. 341 participants from 108 British Caucasian families were phenotyped by CMR and genotyped for 557,124 SNPs. Flow metrics were derived from the CMR images to provide some local information about blood flow in the ascending aorta, based on maximum values at systole at a single location, denoted max, and a 'peak mean' value averaged over the area of the cross section, denoted pm. Heritability was estimated using pedigree-based (QTDT) and SNP-based (GCTA-GREML) methods. Estimates of Reynolds number based on spatially averaged local flow during systole showed substantial heritability ([Formula: see text], [Formula: see text]), while the estimated heritability for Reynolds number calculated using the absolute local maximum velocity was not statistically significant (12-13%; [Formula: see text]). Heritability estimates of the geometric quantities alone; e.g. aortic diameter ([Formula: see text], [Formula: see text]), were also substantially heritable, as described previously. These findings indicate the potential for the discovery of genetic factors influencing haemodynamic traits in large-scale genotyped and phenotyped cohorts where local spatial averaging is used, rather than instantaneous values. Future Mendelian randomisation studies of aortic haemodynamic estimates, which are swift to derive in a clinical setting, will allow for the investigation of causality of abnormal blood flow in CVD.

Marked variation in heritability estimates of left ventricular mass depending on modality of measurement.

Left ventricular (LV) hypertrophy is a strong risk factor for heart failure and cardiovascular death. ECG measures of LV mass are estimated as heritable in twin and family-based analyses and heritability estimates of LV mass measured by echocardiography are lower. We hypothesised that CMR-derived measurements, being more precise than echocardiographic measurements, would advance our understanding of heritable LV traits. We phenotyped 116 British families (427 individuals) by CMR and ECG, and undertook heritability analyses using variance-components (QTDT) and GWAS SNP-based (GCTA-GREML) methods. ECG-based traits such as LV mass and Sokolow-Lyon duration showed substantial estimates of heritability (60%), whereas CMR-derived LV mass was only modestly heritable (20%). However, the ECG LV mass was positively correlated with the lateral diameter of the chest (rho = 0.67), and adjustment for this attenuated the heritability estimate (42%). Finally, CMR-derived right ventricular mass showed considerable heritability (44%). Heritability estimates of LV phenotypes show substantial variation depending on the modality of measurement, being greater when measured by ECG than CMR. This may reflect the differences between electrophysiological as opposed to anatomical hypertrophy. However, ECG LV hypertrophy traits are likely to be influenced by genetic association with anthropometric measures, inflating their overall measured heritability.

Assessment of myocardial fibrosis by late gadolinium enhancement imaging and biomarkers of collagen metabolism in chronic rheumatic mitral regurgitation.

BACKGROUND: In chronic rheumatic mitral regurgitation (CRMR), involvement of the myocardium in the rheumatic process has been controversial. Therefore, we sought to study the presence of fibrosis using late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR) and biomarkers of collagen turnover in CRMR. METHODS: Twenty-two patients with CRMR underwent CMR and echocardiography. Serum concentrations of matrix metalloproteinase- 1 (MMP-1), tissue inhibitor of MMP-1 (TIMP- 1), MMP-1-to-TIMP-1 ratio, procollagen III N-terminal pro-peptide (PIIINP) and procollagen type IC peptide (PIP) were measured. RESULTS: Four patients had fibrosis on LGE-CMR. PICP and PIIINP concentrations were similar to those of the controls, however MMP-1 concentration was increased compared to that of the controls (log MMP-1 3.5 ± 0.7 vs 2.7 ± 0.9, p = 0.02). There was increased MMP-1 activity as the MMP-1-to- TIMP-1 ratio was higher in CRMR patients compared to the controls ( -1.2 ± 0.6 vs -2.1 ± 0.89, p = 0.002). CONCLUSIONS: Myocardial fibrosis was rare in CRMR patients. CRMR is likely a disease characterised by the predominance of collagen degradation rather than increased synthesis and myocardial fibrosis.

Efficacy of cardiac magnetic resonance imaging in a sub-aortic aneurysm case.

Sub-aortic (SA) aneurysms are a rare entity of variable aetiology. We report the first case of a SA aneurysm assessed using cardiac magnetic resonance imaging (MRI). A 33-year-old female with human immunodeficiency virus and on highly active antiretroviral treatment presented with syncope and dyspnoea. Clinical examination suggested moderate to severe aortic regurgitation (AR) confirmed by transthoracic and transoesophageal echocardiograms. However, echocardiography was suboptimal in defining the precise mechanism and severity of AR. A cardiac MRI was done to elucidate the aetiology, severity and mechanism of regurgitation. It confirmed the presence of a SA aneurysm below the left coronary cusp and its retraction, resulting in an eccentric AR jet. An assessment of moderate AR, based on regurgitant volume, was made. Furthermore, the anatomical relationships of the aneurysm were clearly defined. Cardiac MRI allowed comprehensive assessment of this SA aneurysm.

Improvements in ECG accuracy for diagnosis of left ventricular hypertrophy in obesity.

OBJECTIVES: The electrocardiogram (ECG) is the most commonly used tool to screen for left ventricular hypertrophy (LVH), and yet current diagnostic criteria are insensitive in modern increasingly overweight society. We propose a simple adjustment to improve diagnostic accuracy in different body weights and improve the sensitivity of this universally available technique. METHODS: Overall, 1295 participants were included-821 with a wide range of body mass index (BMI 17.1-53.3 kg/m(2)) initially underwent cardiac magnetic resonance evaluation of anatomical left ventricular (LV) axis, LV mass and 12-lead surface ECG in order to generate an adjustment factor applied to the Sokolow-Lyon criteria. This factor was then validated in a second cohort (n=520, BMI 15.9-63.2 kg/m(2)). RESULTS: When matched for LV mass, the combination of leftward anatomical axis deviation and increased BMI resulted in a reduction of the Sokolow-Lyon index, by 4 mm in overweight and 8 mm in obesity. After adjusting for this in the initial cohort, the sensitivity of the Sokolow-Lyon index increased (overweight: 12.8% to 30.8%, obese: 3.1% to 27.2%) approaching that seen in normal weight (37.8%). Similar results were achieved in the validation cohort (specificity increased in overweight: 8.3% to 39.1%, obese: 9.4% to 25.0%) again approaching normal weight (39.0%). Importantly, specificity remained excellent (>93.1%). CONCLUSIONS: Adjusting the Sokolow-Lyon index for BMI (overweight +4 mm, obesity +8 mm) improves the diagnostic accuracy for detecting LVH. As the ECG, worldwide, remains the most widely used screening tool for LVH, implementing these findings should translate into significant clinical benefit.

Myocardial tissue phase mapping reveals impaired myocardial tissue velocities in obesity.

Although obesity is linked to heart failure on a population level, not all obese subjects develop cardiac failure. As a result, identifying obese subjects with subclinical changes in myocardial velocities may enable earlier detection of those susceptible to developing overt heart failure. As echocardiography is limited in obesity due to limited acoustic window, we used phase contrast magnetic resonance imaging to assess myocardial velocities in obese and normal weight subjects. Normal weight (BMI 23 ± 3; n = 40) and obese subjects (BMI 37 ± 7; n = 59) without identifiable cardiovascular risk factors underwent MRI (1.5 Tesla) to determine left ventricular myocardial velocities using phase contrast tissue phase mapping. Systolic function was not different between normal and obese subjects (LVEF 67 ± 5 vs 68 ± 4, p = 0.22). However, obesity was associated with significantly impaired peak radial and longitudinal diastolic myocardial velocity (by 13 and 19 % respectively, both p < 0.001). In addition time-to-peak longitudinal diastolic velocity was delayed in obesity (by 39 ms, p < 0.001). In addition, peak longitudinal diastolic strain was 20 % lower in obesity (p = 0.015) and time-to-peak longitudinal diastolic strain rate significantly delayed in obesity (by 92 ms, p < 0.001).Although peak radial systolic velocity was similar between obese and normal weight subjects (p = 0.14) peak longitudinal systolic velocity was 7 % lower in the obese cohort (p = 0.02). In obesity without co-morbidities, tissue phase mapping has shown subclinical changes in systolic and diastolic function. Given the link between obesity and heart failure, early detection of changes may become clinically important to prevent disease progression.

Obese subjects show sex-specific differences in right ventricular hypertrophy.

BACKGROUND: As right ventricular (RV) remodeling in obesity remains underinvestigated, and the impact of left ventricular (LV) diastolic dysfunction on RV hypertrophy is unknown, we aimed to investigate whether (1) sex-specific patterns of RV remodeling exist in obesity and (2) LV diastolic dysfunction in obesity is related to RV hypertrophy. METHODS AND RESULTS: Seven hundred thirty-nine subjects (women, n=345; men, n=394) without identifiable cardiovascular risk factors (body mass index [BMI], 15.3-59.2 kg/m2) underwent cardiovascular magnetic resonance (1.5 T) to measure RV mass (g), RV end-diastolic volume (mL), RV mass/volume ratio, and LV diastolic peak filling rate (mL/s). All subjects were normotensive (average, 119±11/73±8 mm Hg), normoglycaemic (4.8±0.5 mmol/L), and normocholesterolaemic (4.8±0.9 mmol/L) at the time of scanning. Across both sexes, there was a moderately strong positive correlation between BMI and RV mass (men, +0.8 g per BMI point increase; women, +1.0 g per BMI point increase; both P<0.001). Whereas women exhibited RV cavity dilatation (RV end-diastolic volume, +1.0 mL per BMI point increase; P<0.001), BMI was not correlated with RV end-diastolic volume in men (R=0.04; P=0.51). Concentric RV remodeling was present in both sexes, with RV mass/volume ratio being positively correlated to BMI (men, R=0.41; women, R=0.51; both P<0.001). Irrespective of sex, the LV peak filling rate was negatively correlated with both RV mass (men, R=-0.43; women, R=-0.44; both P<0.001) and RV mass/volume ratio (men, R=-0.37; women, R=-0.35; both P<0.001). CONCLUSIONS: A sex difference in RV remodeling exists in obesity. Whereas men exhibit concentric RV remodeling, women exhibit a mixed pattern of eccentric and concentric remodeling. Regardless of sex, reduced LV diastolic function is associated with concentric RV remodeling.

Concentric left ventricular remodeling and aortic stiffness: a comparison of obesity and hypertension.

BACKGROUND: Increased thoracic ascending aortic stiffness is thought to contribute to concentric left ventricular hypertrophy and increased mortality, a pattern seen in hypertension. As such, aortic stiffness and increased left ventricular mass are candidates by which obesity increases cardiovascular risk. However, obesity is characterized predominantly by increased abdominal aortic stiffness and with eccentric left ventricular hypertrophy. METHODS: We aimed to establish whether or not, in addition to these changes, there is also an element of concentric remodeling in obesity that was predicted by ascending aortic stiffness. 301 subjects underwent cardiovascular magnetic resonance imaging to measure regional aortic distensibility and left ventricular morphology. To compare obesity with hypertension, subjects were separated into groups by hypertensive status and body mass index. RESULTS: In comparison to normotensive subjects, hypertension was linked with concentric remodeling (a 17% increase in left ventricular mass:volume ratio (LVM:VR), (p<0.001)) and reduced ascending aortic distensibility (by 64%,p<0.001). LVM:VR was negatively correlated with ascending aortic distensibility (R=-0.36,p<0.01). Obesity, in the absence of hypertension, was associated with elevated left ventricular mass when compared to normal weight normotensive subjects (by 27%, p<0.01), in an eccentric pattern with cavity dilatation (p<0.01). However, LVM:VR was also 14% larger than in normal weight normotensive subjects (p<0.01), indicative of additional concentric remodeling. LVM:VR in obesity was, however, not correlated with ascending aortic distensibility when adjusted for mean arterial pressure (R=-0.14,p<0.14). CONCLUSION: In summary, despite the predominantly eccentric pattern of left hypertrophy in obesity there is a concentric element of hypertrophy that, unlike in hypertension, is not linked to increased ascending aortic stiffness.

Atherosclerosis and arterial stiffness in obstructive sleep apnea--a cardiovascular magnetic resonance study.

OBJECTIVE: Obstructive sleep apnoea (OSA) has been linked to cardiovascular risk factors, such as hypertension, and clinical cardiovascular endpoints. Our aim was to assess whether OSA is independently associated with atherosclerosis and vascular dysfunction as assessed by cardiovascular magnetic resonance (CMR). METHODS: 58 patients with OSA and 39 matched control subjects without OSA underwent CMR of the aorta and carotid arteries. Carotid and aortic wall thickness and aortic distensibility were measured. Multi-weighted, high resolution CMR imaging was used for carotid atheroma characterization according to the American Heart Association (AHA) atheroma classification, modified for CMR. RESULTS: Carotid [1.47±0.03 mm vs. 1.26±0.05 mm, (P<0.01)] and aortic wall thickness [2.95±0.09 mm vs. 2.05±0.07 mm, (P<0.001)] were increased in patients with OSA compared to controls. Aortic distensibility was decreased in patients with OSA [3.62±0.3 vs. 4.75±0.2 mmHg(-1)×10(-3), (P<0.05)]. Prevalence of carotid plaque, average carotid atheroma class, and prevalence of high risk features of carotid atheroma were increased in patients with OSA (P<0.005 for all). On multivariate analysis, Oxygen desaturation index (ODI) emerged as an independent predictor of carotid and aortic wall thickness, but not of aortic stiffness. CONCLUSIONS: OSA is associated with increased carotid and aortic atheroma burden and with advanced, high risk carotid atherosclerotic plaques, but not with aortic stiffening.