Hemodynamic Determinants of Elevated Blood Pressure and Hypertension in the Middle to Older-Age UK Population: A UK Biobank Imaging Study

BACKGROUND

Increased systemic vascular resistance and, in older people, reduced aortic distensibility, are thought to be the hemodynamic determinants of primary hypertension but cardiac output could also be important. We examined the hemodynamics of elevated blood pressure and hypertension in the middle to older-aged UK population participating in the UK Biobank imaging studies.

METHODS

Cardiac output, systemic vascular resistance, and aortic distensibility were measured from cardiac magnetic resonance imaging in 31 112 (distensibility in 21 178) participants (46.3% male, mean age±SD 63±7 years). Body composition including visceral adipose tissue volume and abdominal subcutaneous adipose tissue volume were measured in 19 645 participants.

RESULTS

Participants with higher blood pressure had higher cardiac output (higher by 17.9±26.6% in hypertensive compared with those with optimal blood pressure) and higher systemic vascular resistance (higher by 11.4±27.9% in hypertensive compared with those with optimal blood pressure). These differences were little changed after adjustment for body size and adiposity. The contribution of cardiac output relative to systemic vascular resistance was more marked in younger compared with older subjects. Aortic distensibility decreased with age and was lower in participants with higher compared with lower blood pressure but with a greater difference in younger compared with older subjects.

CONCLUSIONS

In the middle to older-aged UK population, cardiac output plays an important role in contributing to elevated mean arterial blood pressure, particularly in younger compared with older subjects. Reduced aortic distensibility contributes to a rise in pulse pressure and systolic blood pressure at all ages.

Impaired Distensibility of the Proximal Aorta in Fetuses With Tetralogy of Fallot

Background Increased aortic wall stiffness, which even persists after repair, has been reported in patients with tetralogy of Fallot (TOF). We aimed to observe the distensibility of the ascending aorta and descending aorta in fetuses with TOF and explore its relation with aortic blood flow volume and aortic and pulmonary annular size. Methods and Results Twenty-three fetuses with TOF and 23 gestational age-matched normal fetuses were included in this prospective cross-sectional study. The distensibilities of the ascending aorta and descending aorta were assessed by aortic strain (AS), which was defined as follows: 100×(maximum internal diameter in the systolic phase-minimum internal diameter in the diastolic phase)/minimum internal diameter in the diastolic phase. The maximum internal diameter in the systolic phase and minimum internal diameter in the diastolic phase of the ascending aorta and descending aorta were measured by M-mode echocardiography. Associations between AS and aortic blood flow volume and aortic and pulmonary valve diameters were assessed in both groups. AS of the ascending aorta in TOF group was lower than that in controls (20.48%±4.19% versus 28.17%±4.54%; P<0.001), whereas there was no significant difference in the descending aorta. The multivariate regression model demonstrated that AS was significantly related to aortic valve size (P=0.014) and aortic blood flow volume (P=0.022) in fetuses with TOF, whereas only aortic blood flow volume was significantly correlated with AS in the control group (P=0.01). No significant association was found between AS and pulmonary valve size. Conclusions Impaired distensibility of proximal aorta was observed in fetuses with TOF. Both intrinsic abnormalities of the aortic wall and aortic volume overload probably play roles in the altered aortic distensibility.

Thickness and Volume of Epicardial Adipose Tissue in Relation to Stiffness and Elasticity of Aorta Assessed by Computed Tomography Angiography

PURPOSE

The aim of the study was to assess the importance of the measurements of thickness and volume of epicardial adipose tissue (EAT) in coronary computed tomography angiography (CCTA) as a predictive factor of increased stiffness and impaired elasticity of aorta.

METHODS AND MATERIALS

The study involved a group of 97 patients (63.48 ± 8.50 years). In accordance with the medians of epicardial adipose tissue (EAT) parameters, aortic elasticity and stiffness parameters, patients were divided into subgroups: EAT thickness median 9.40 mm, EAT volume median 61.95 mL, EAT thickness index 5.08 mm/m² and EAT volume index 34.33 mL/m².

RESULTS

The mean coronary artery calcium score was 162.24 (±317.69). The mean aortic stiffness index was 4.18 (±0.81). The assessed mean aortic elasticity parameters were 3.29% (±2.37) and 0.12 cm²/dyn (±0.09) for strain and distensibility, respectively. A positive linear correlation was observed between EAT parameters and aortic stiffness (0.21), volume (0.51), thickness index (0.24), volume index (0.55) and, for aorta elasticity, a negative linear correlation between the following EAT parameters was observed: thickness (-0.32 and -0.30), volume (-0.49 and -0.48), thickness index (-0.34 and -0.31), volume index (-0.51 and -0.49) and aortic elasticity parameters (aorta strain and aorta distensibility, respectively).

CONCLUSION

The study showed that CCTA illustrates a relationship between the parameters of EAT and an increased stiffness of the aorta, while the most predictive factor of stiffness was the volume index.

Feasibility of Wave Intensity Analysis from 4D Cardiovascular Magnetic Resonance Imaging Data

Congenital heart defects (CHD) introduce haemodynamic changes; e.g., bicuspid aortic valve (BAV) presents a turbulent helical flow, which activates aortic pathological processes. Flow quantification is crucial for diagnostics and to plan corrective strategies. Multiple imaging modalities exist, with phase contrast magnetic resonance imaging (PC-MRI) being the current gold standard; however, multiple predetermined site measurements may be required, while 4D MRI allows for measurements of area (A) and velocity (U) in all spatial dimensions, acquiring a single volume and enabling a retrospective analysis at multiple locations. We assessed the feasibility of gathering hemodynamic insight into aortic hemodynamics by means of wave intensity analysis (WIA) derived from 4D MRI. Data were collected in n = 12 BAV patients and n = 7 healthy controls. Following data acquisition, WIA was successfully derived at three planes (ascending, thoracic and descending aorta) in all cases. The values of wave speed were physiological and, while the small sample limited any clinical interpretation of the results, the study shows the possibility of studying wave travel and wave reflection based on 4D MRI. Below, we demonstrate for the first time the feasibility of deriving wave intensity analysis from 4D flow data and open the door to research applications in different cardiovascular scenarios.

Haemodynamic Adaptive Mechanisms at High Altitude: Comparison between European Lowlanders and Nepalese Highlanders

Background: Exposure to high altitudes determines several adaptive mechanisms affecting in a complex way the whole cardiovascular, respiratory, endocrine systems because of the hypobaric hypoxic condition. The aim of our study was to evaluate the circulatory adaptive mechanisms at high altitudes, during a scientific expedition in the Himalayas. Methods: Arterial distensibility was assessed measuring carotid-radial and carotid-femoral pulse wave velocity. Tests were carried out at several altitudes, from 1350 to 5050 m above sea level, on 8 lowlander European researchers and 11 highlander Nepalese porters. Results: In Europeans, systolic blood pressure and pulse pressure increased slightly but significantly with altitude (p < 0.05 and p < 0.001, respectively). Norepinephrine showed a significant increase after the lowlanders had spent some time at high altitude (p < 0.001). With increasing altitude, a progressive increase in carotid-radial and carotid-femoral pulse wave velocity values was observed in lowlanders, showing a particularly significant increase (p < 0.001) after staying at high altitude (carotid-radial pulse wave velocity, median value (interquartile range) from 9.2 (7.9−10.0) to 11.2 (10.9−11.8) m/s and carotid-femoral pulse wave velocity from 8.5 (7.9−9.0) to 11.3 (10.9−11.8) m/s). At high altitudes (3400 and 5050 m above sea level), no significant differences were observed between highlanders and lowlanders in hemodynamic parameters (blood pressure, carotid-radial and carotid-femoral pulse wave velocity). Conclusions: The progressive arterial stiffening with altitude observed in European lowlanders could explain the increase in systolic and pulse pressure values observed at high altitudes in this ethnic group. Further studies are needed to evaluate the role of aortic stiffening in the pathogenesis of acute mountain sickness.

Aortic distensibility is equal in prepubertal girls and boys and increases with puberty in girls

Windkessel function is governed by conductance artery compliance that is associated with cardiovascular disease in adults independently of other risk factors. Sex-related differences in conductance artery compliance partly explain the sex-related differences in risk of cardiovascular disease. Studies on sex-related differences in conductance artery function in prepubertal children are few and inconclusive. This study determined conductance artery compliance and cardiac function by magnetic resonance imaging in 150 healthy children (75 girls) aged 7-10 years. Any sex-related difference in conductance artery function was determined with correction for other potential predictors in multivariable linear regression models. Our data showed that ascending (crude mean difference 1.11 95% CI (0.22; 2.01)) and descending (crude mean difference 1.10 95% CI (0.09; 1.91)) aortic distensibility were higher in girls, but differences disappeared after adjustment for pubertal status and other identified potential predictors. Systolic and diastolic blood pressure, cardiac output, left ventricle (LV) systolic function, and total peripheral resistance did not differ between the sexes. In girls, heart rate was 7 bpm higher, whereas pulse pressure (by 2 mmHg), and LV end-diastolic volume index (by 7 mL) and stroke volume (by 5 mL) were lower. LV peak filling rate indexed to LV end-diastolic volume was 0.5 s^-1 higher in girls. In conclusion, prepubertal girls and boys have equal conductance artery function. Thus, the well-known sex difference in adult conductance artery function seems to develop after the onset of puberty with girls initially increasing aortic distensibility.

Limited Effect of 60-Days Strict Head Down Tilt Bed Rest on Vascular Aging

Background

Cardiovascular risk may be increased in astronauts after long term space flights based on biomarkers indicating premature vascular aging. We tested the hypothesis that 60 days of strict 6° head down tilt bed rest (HDTBR), an established space analog, promotes vascular stiffening and that artificial gravity training ameliorates the response.

Methods

We studied 24 healthy participants (8 women, 24–55 years, BMI = 24.3 ± 2.1 kg/m²) before and at the end of 60 days HDTBR. 16 subjects were assigned to daily artificial gravity. We applied echocardiography to measure stroke volume and isovolumetric contraction time (ICT), calculated aortic compliance (stroke volume/aortic pulse pressure), and assessed aortic distensibility by MRI. Furthermore, we measured brachial-femoral pulse wave velocity (_bfPWV) and pulse wave arrival times (PAT) in different vascular beds by blood pressure cuffs and photoplethysmography. We corrected PAT for ICT (cPAT).

Results

In the pooled sample, diastolic blood pressure (+8 ± 7 mmHg, p < 0.001), heart rate (+7 ± 9 bpm, p = 0.002) and ICT (+8 ± 13 ms, p = 0.036) increased during HDTBR. Stroke volume decreased by 14 ± 15 ml (p = 0.001). _bfPWV, aortic compliance, aortic distensibility and all cPAT remained unchanged. Aortic area tended to increase (p = 0.05). None of the parameters showed significant interaction between HDTBR and artificial gravity training.

Conclusion

60 days HDTBR, while producing cardiovascular deconditioning and cephalad fluid shifts akin to weightlessness, did not worsen vascular stiffness. Artificial gravity training did not modulate the response.

Structural and functional remodeling of the female Apoe-/- mouse aorta due to chronic cigarette smoke exposure

Despite a decline in popularity over the past several decades, cigarette smoking remains a leading cause of cardiovascular morbidity and mortality. Yet, the effects of cigarette smoking on vascular structure and function are largely unknown. To evaluate changes in the mechanical properties of the aorta that occur with chronic smoking, we exposed female apolipoprotein E-deficient mice to mainstream cigarette smoke daily for 24 wk, with room air as control. By the time of euthanasia, cigarette-exposed mice had lower body mass but experienced larger systolic/diastolic blood pressure when compared with controls. Smoking was associated with significant wall thickening, reduced axial stretch, and circumferential material softening of the aorta. Although this contributed to maintaining intrinsic tissue stiffness at control levels despite larger pressure loads, the structural stiffness became significantly larger. Furthermore, the aorta from cigarette-exposed mice exhibited decreased ability to store elastic energy and augment diastolic blood flow. Histological analysis revealed a region-dependent increase in the cross-sectional area due to smoking. Increased smooth muscle and extracellular matrix content led to medial thickening in the ascending aorta, whereas collagen deposition increased the thickness of the descending thoracic and abdominal aorta. Atherosclerotic lesions were larger in exposed vessels and featured a necrotic core overlaid by a thinned fibrous cap and macrophage infiltration, consistent with a vulnerable phenotype. Collectively, our data indicate that cigarette smoking decreases the mechanical functionality of the aorta, inflicts morphometric alterations to distinct segments of the aorta, and accelerates the progression of atherosclerosis.NEW & NOTEWORTHY We studied the effects of chronic cigarette smoking on the structure and function of the aorta in a mouse model of nose-only aerosol inhalation. Our data indicated that exposure to cigarette smoke impairs vascular function by reducing the ability of the aorta to store elastic energy and by decreasing aortic distensibility. Combined with a more vulnerable atherosclerotic phenotype, these findings reveal the biomechanical mechanisms that support the development of cardiovascular disease due to cigarette smoking.

Aortic Distensibility Can Predict Events in Patients With Premature Coronary Artery Disease: A Cardiac Magnetic Resonance Study

Noninvasive assessment of aortic distensibility (AD) is feasible with cardiac magnetic resonance (CMR). We investigated the relationship between AD (assessed by CMR) and coronary artery disease (CAD) severity (assessed by the SYNTAX score) in patients with premature CAD. We recruited 125 patients with CAD confirmed by coronary angiography (males were <55 years old and females <65 years old). We excluded patients with significant aortic disease or contraindications to CMR. We also recruited 25 age- and sex-matched healthy patients as controls. One-year follow-up was also carried out. Aortic distensibility at the aortic root (AR) and descending aorta (DA) was significantly (P < .001 for both) lower in the patient group. There was a significant negative correlation between SYNTAX score and AD at the AR (r = -0.56; P < .001) and DA (r = -0.34; P < .001), but insignificant correlation with distensibility at the ascending aorta (AA; r = -0.03; P = .81). AR, AA, and DA distensibility, as well as left ventricular ejection fraction were predictors of adverse events. The severity of CAD in young patients is associated with decreased AD, especially at the level of the AR. Aortic distensibility can predict adverse events in these patients.

Postoperative and mid-term hemodynamic changes after replacement of the ascending aorta

OBJECTIVES

To evaluate aortic distensibility and pulse waveform patterns associated with the ascending aortic aneurysm, and to analyze the postoperative and mid-term hemodynamic changes induced by prosthetic replacement of the ascending aorta.

METHODS

Central blood pressure waves were recorded at the carotid artery level by means of a validated transcutaneous arterial tonometer in 30 patients undergoing prosthetic replacement of ascending aortic aneurysm and in 30 control patients. Measurements were obtained the day before surgery and 5 to 7 days and 16 to 20 months after surgery.

RESULTS

The ascending aortic aneurysm was associated with a less steep slope of early systolic phase of the pressure curve (pulsus tardus) compared with a control group (0.54 ± 0.18 mm Hg/ms vs 0.69 ± 0.26 mm Hg/ms; P = .011). Replacing the ascending aorta with a noncompliant vascular prosthesis steepened the pulse pressure slope during the early systolic phase in the postoperative period (0.77 ± .29 mm Hg/ms), providing values comparable with those of the control group in the mid-term (0.67 ± .20 mm Hg/ms). No change in aortic stiffness was found either postoperatively or in the mid-term after ascending aorta surgical replacement (carotid-femoral pulse wave velocity: preoperative, 9.0 ± 2.6 m/s; postoperative, 9.0 ± 2.9 m/s; mid-term postoperative, 9.3 ± 2.8 m/s).

CONCLUSIONS

This study does not confirm the assumption that substitution of the viscoelastic ascending aorta with a rigid prosthesis can cause serious hemodynamic alterations downstream, because we did not observe a worsening of global aortic distensibility after insertion of a rigid prosthetic aorta. The ascending aortic aneurysm is associated with a pulsus tardus.

Parathyroid Hormone and Ischemic Cerebrovascular Event

BACKGROUND

Increased parathyroid hormone (PTH) level is associated with coronary artery disease, hypertension and left ventricular hypertrophy which are all predisposing factors for the ischemic cerebrovascular event (ICVE). Carotid intima-media thickness (CIMT) and aortic distensibility are the two early, subclinical predictors of atherosclerosis. The relation of PTH with CIMT and aortic distensibility in patients with ICVE has not been previously studied.

OBJECTIVE

Our aim was to study the relationship of PTH levels with aortic distensibility and CIMT in patients with ICVE.

METHODS

Sixty-four ICVE patients and 50 control group were enrolled in the study. PTH levels, aortic distensibility and CIMT were measured in all individuals.

RESULTS

PTH levels were significantly higher in ICVE patients than in the controls (60.1±21.6 vs. 52.3±6.2 pg/ml) (p=0. 008). PTH levels were found to be inversely correlated with aortic distensibility (r= -0. 420, p=0.001) and positively correlated with CIMT (r:0, 285, p=0,002).

CONCLUSION

The present study shows that PTH levels are increased in patients with acute ischemic cerebrovascular event compared to the control group. It also demonstrates that PTH levels are inversely related to aortic distensibility of ascending aorta and positively associated with CIMT.

Aortic stiffness in families with inherited non-syndromic thoracic aortic disease

BACKGROUND

In families with an inherited form of non-syndromic thoracic aortic disease (TAAD), aortic diameter alone is not a reliable marker for disease occurrence or progression. To identify other parameters of aortic function, we studied aortic stiffness in families with TAAD. We also compared diameter measurements obtained by transthoracic echocardiography (TTE) and magnetic resonance imaging (MRI).

METHODS

Seven families, including 116 individuals, with non-syndromic TAAD, were studied. The aortic diameter was measured by TTE and MRI. Aortic stiffness was assessed as local distensibility in the ascending aorta and as regional and global pulse wave velocity (PWV). Individuals with a dilated thoracic aorta (n = 21) were compared with those without aortic dilatation (n = 95).

RESULTS

Ascending aortic diameter measured by TTE strongly correlated with the diameter measured by MRI (r² = 0.93). The individuals with dilated aortas were older than those without dilatation (49 vs 37 years old). Ascending aortic diameter increased and distensibility decreased with increasing age; while, PWV increased with age and diameter. Some young subjects without aortic dilatation showed increased aortic stiffness. Individuals with a dilated thoracic aorta had significantly higher PWV and lower distensibility, measured by MRI than individuals without dilatation.

CONCLUSIONS

Diameters measured with TTE agree with those measured by MRI. Aortic stiffness might be a complementary marker for aortic disease and progression when used with aortic diameter, especially in young individuals.

Aortic elasticity and the influence of valve morphology in children with bicuspid aortic valve

AimWe investigated dimensions and elasticity of whole aorta in patients with bicuspid aortic valve and influence of valve phenotype.

METHOD

The study group included 44 patients and 42 controls. Patients were divided into groups according to the type of valve opening as horizontal - fusion between right and left coronary cusps - and vertical - fusion between right-non-coronary cusps; according to age they were divided into younger (5-10 years) and older patients (11-16 years). Our study did not include valve phenotype with fusion between left and non-coronary cusps. Systolic-diastolic diameters of aortic annulus, sinus valsalva, sinutubular junction, arcus, and ascending-descending and abdominal aorta were measured and z-scores were obtained. Aortic strain, distensibility, and stiffness index were calculated. Flow-mediated dilatation of brachial artery was studied.

RESULTS

z-Scores at annulus, sinus valsalva, sinutubular junction, and ascending aorta were higher in study patients (p=0.001, p=0.0001, p=0.0001, p=0.0001, respectively). z-Scores of sinus valsalva and sinotubular junction were higher in the horizontal group than in the vertical group (p=0.006, p=0.023, respectively). z-Score was over +2 in 51% of patients with horizontal morphology and 33% of patients with vertical morphology (p=0.0001). Ascending aorta was more distensible and less stiff in the study group (11.3±5.63 versus 7.91±4.5, p=0.002; 4.76±3.60 versus 6.19±3.44 cm2.dyn-1.10-6, p=0.033, respectively). Stiffness index of ascending, arcus, and abdominal aorta were higher in the horizontal group (p=0.004, p=0.038, p=0.006, respectively). Ascending aorta was more distensible and less stiff in the younger group (p=0.007, p=0.027, respectively) but did not differ in the older group compared with the control group.

CONCLUSION

Aortic dimensions are enlarged in patients with bicuspid aortic valve starting from childhood, suggesting the presence of generalised aortopathy. Aortic elasticity is increased at young age and decreased with age.

Over-Wrapping of the Aortic Wall with an Elastic Extra-Aortic Wrap Results in Luminal Creasing

Elastic extra-aortic wrapping is a potential non-pharmacological way to improve aortic compliance and treat isolated systolic hypertension associated with a stiffened aorta. We aimed to use computer simulations to re-evaluate whether there is aortic shape distortion in aortic wrapping to achieve greater elasticity of the wrapped aortic segment. Non-linear transient numerical analysis based on an idealized hyper-elastic single-layered aorta model was performed to simulate the force/displacement regimes of external aortic wrapping. Pressure-displacement relationships were used to establish model aortic wall distensibilities of 4.3 and 5.5 (10⁻³ mmHg⁻¹). A physiological pulsatile lumen pressure was employed to estimate the potential improvements in aortic distensibility by compression forces representing elastic aortic wrapping. In the less distensible model of the aortic wall there was increased systolic expansion in the wrapped segment. We found a risk of creasing of the aortic luminal wall with wrapping. Sufficient unloading of a thick and elastic aortic wall to induce increased compliance, as observed in elastic wrapping, is associated with the potential risk of over compression and folding (creasing) inside the lumen.

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.

Age and hypertension strongly induce aortic stiffening in rats at basal and matched blood pressure levels

Age and hypertension are major causes of large artery remodeling and stiffening, a cardiovascular risk factor for heart and kidney damage. The aged spontaneously hypertensive rat (SHR) model is recognized for human cardiovascular pathology, but discrepancies appeared in studies of arterial stiffness. We performed experiments using a robust analysis via echo tracking in 20-week adult (n = 8) and 80-week-old SHR (n = 7), with age-matched normotensive Wistar Kyoto rats (WKY, n = 6;6) at basal and matched levels of blood pressure (BP). After anesthesia with pentobarbital, abdominal aortic diameter and pressure were recorded and BP was decreased by clonidine i.v. At basal BP, aortic pulse distension, compliance, and distensibility (AD) were reduced and stiffness index increased with age and hypertension and further altered with age + hypertension. When BP was adjusted in SHR to that of normotensive rats (130 mmHg), there was no difference between 20-week-old SHR and WKY Importantly, the age effect was maintained in both WKY and SHR and accentuated by hypertension in old rats. At 130 mmHg, with similar pulse pressure in the four groups, AD (kPa(-3)) = 24.2 ± 1 in 20 weeks WKY, 19.7 ± 1.4 in 20 weeks SHR, 12.4 ± 1.3 in 80 weeks WKY and 6.6 ± 0.6 in 80 weeks SHR; distension = 7.6 ± 0.4%, 6.7 ± 0.6%, 3.7 ± 0.3%, and 1.8 ± 0.2% in the same groups. In conclusion, reduced distensibility, that is, stiffening due to age is clearly shown here in both WKY and SHR as well as a synergistic effect of age and hypertension. This technique will allow new studies on the mechanisms responsible and drug intervention.

Aortic distensibility as a surrogate for intertwin pulse pressure differences in monochorionic pregnancies with and without twin-twin transfusion syndrome

OBJECTIVES

Twin-twin transfusion syndrome (TTTS) complicates 10-15% of monochorionic diamniotic (MCDA) twin pregnancies. The donor response to hypovolemia allows the transfer of vasoactive mediators to the recipient, causing increased recipient afterload and hypertension. Our objective was to apply a novel speckle-tracking technique to measure the aortic fractional area change (AFAC) during the cardiac cycle in MCDA twins with and without TTTS, and identify intertwin differences in AFAC and parameters of cardiac function.

METHODS

High-frame rate four-chamber views of the fetal heart, including the mid-thoracic aorta, were collected prospectively in MCDA twin pairs referred to our center between June 2014 and April 2015. Using speckle-tracking software, the endovascular border of the aorta was traced manually during systole, with guidance on cardiac cycle timing by anatomical M-mode. AFAC, defined as the difference between maximum and minimum area divided by minimum area, expressed as a percentage, was calculated offline and averaged over three cardiac cycles. Tissue Doppler and displacement were used to measure long-axis cardiac function. Intra- and interclass correlation coefficients were used to test observer variability.

RESULTS

Fifty-one MCDA twin pregnancies were included, comprising uncomplicated MCDA (n = 14), TTTS Stages 1/2 (n = 21) and TTTS Stages 3/4 (n = 16). Median gestational age was 20.4 (range, 16.2-27.5) weeks. Mean ± SD heart rate was 142.6 ± 7.2 bpm with no significant intertwin pair differences. AFAC was significantly higher in recipients than in donors of TTTS pairs (Stages 1/2: 72.3 ± 29.9% vs 43.7 ± 19.3%, P < 0.001; Stages 3/4: 75.2 ± 29.2% vs 42.5 ± 18.4%, P = 0.002), consistent with higher recipient pulse pressure. No intertwin differences in AFAC were seen in uncomplicated MCDA pairs. Inter- and intraclass correlation coefficients for AFAC were 0.894 and 0.888. AFAC correlated significantly with combined cardiac output (r = 0.252, P = 0.011) and left and right E/E' ratio (left: r = 0.302, P = 0.004; right: r = 0.247, P = 0.030).

CONCLUSION

AFAC is a quantifiable and reproducible method to assess aortic distensibility and is a promising tool to monitor the response to prelaser therapeutic interventions in pregnancies with TTTS. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Chronic vagal nerve stimulation prevents high-salt diet-induced endothelial dysfunction and aortic stiffening in stroke-prone spontaneously hypertensive rats

Parasympathetic activity is often reduced in hypertension and can elicit anti-inflammatory mechanisms. Thus we hypothesized that chronic vagal nerve stimulation (VNS) may alleviate cardiovascular end-organ damage in stroke-prone spontaneously hypertensive rats. Vagal nerve stimulators were implanted, a high-salt diet initiated, and the stimulators turned on (VNS, n = 10) or left off (sham, n = 14) for 4 wk. Arterial pressure increased equally in both groups. After 4 wk, endothelial function, assessed by in vivo imaging of the long posterior ciliary artery (LPCA) after stimulation (pilocarpine) and inhibition (N(ω)-nitro-l-arginine methyl ester) of endothelial nitric oxide synthase (eNOS), had significantly declined (-2.3 ± 1.2 μm, P < 0.05) in sham, but was maintained (-0.7 ± 0.8 μm, nonsignificant) in VNS. Furthermore, aortic eNOS activation (phosphorylated to total eNOS protein content ratio) was greater in VNS (0.83 ± 0.07) than in sham (0.47 ± 0.08, P < 0.05). After only 3 wk, ultrasound imaging of the aorta demonstrated decreased aortic strain (-9.7 ± 2.2%, P < 0.05) and distensibility (-2.39 ± 0.49 1,000/mmHg, P < 0.05) and increased pulse-wave velocity (+2.4 ± 0.7 m/s, P < 0.05) in sham but not in VNS (-3.8 ± 3.8%, -0.70 ± 1.4 1,000/mmHg, and +0.1 ± 0.7 m/s, all nonsignificant). Interleukin (IL)-6 serum concentrations tended to be higher in VNS than in sham (34.3 ± 8.3 vs. 16.1 ± 4.6 pg/ml, P = 0.06), and positive correlations were found between NO-dependent relaxation of the LPCA and serum levels of IL-6 (r = +0.70, P < 0.05) and IL-10 (r = +0.56, P < 0.05) and between aortic eNOS activation and IL-10 (r = +0.48, P < 0.05). In conclusion, chronic VNS prevents hypertension-induced endothelial dysfunction and aortic stiffening in an animal model of severe hypertension. We speculate that anti-inflammatory mechanisms may contribute to these effects.

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.

Early and late changes in markers of aortic stiffness with breast cancer therapy

BACKGROUND

Anthracyclines and trastuzumab are well recognised to cause cardiac toxicity. Further to their effects on left ventricular (LV) function, anthracyclines in particular are considered to cause negative arterial remodelling. Whether these changes reverse is unknown. In addition, whether trastuzumab causes specific effects on arterial remodelling is yet undetermined.

METHODS

Patients receiving these agents for treatment of breast cancer and healthy volunteers prospectively underwent clinical evaluation and cardiovascular magnetic resonance (CMR) imaging at baseline, 1, 4 and 14 months post-therapy, including functional assessment, measurement of aortic pulse wave velocity (PWV) using velocity encoded imaging and distensibility at ascending aorta (AA) and proximal descending aorta (PDA).

RESULTS

Twenty-nine patients pretherapy and 12 volunteers demonstrated no differences in PWV, distensibility and LV function. Among cancer subjects, PWV increased acutely, P = 0.002 (4 months), then decreased by 14 months (P < 0.001). In addition, a decrease was observed in distensibility at the AA within 1 (P = 0.001) and 4 months (P < 0.001) of commencing therapy. At the PDA, only significant reduction was observed at 14 month distensibility when compared with baseline, P < 0.001. Patients with anthracycline exposure only had a greater reduction in aortic distensibility in the AA with time, P = 0.005 at 1 month, P < 0.001 at 4 months and P = 0.009 at 14 months.

CONCLUSION

Acute changes are observed in PWV and distensibility at the AA following contemporary breast cancer chemotherapy and partially reverse a year after therapy is discontinued, with more severe effects seen with anthracyclines.

Effects of a new advanced glycation inhibitor, LR-90, on mitigating arterial stiffening and improving arterial elasticity and compliance in a diabetic rat model: aortic impedance analysis

BACKGROUND AND PURPOSE

We determined the effects of treatment with LR-90, an inhibitor of advanced glycation end products, on the mechanical properties of the arterial system in streptozotocin (STZ)-induced diabetic Sprague Dawley rats, using aortic impedance analysis, and further investigated the effects of LR-90 on the progression of aortic pathology.

EXPERIMENTAL APPROACH

STZ-induced diabetic rats were treated with or without LR-90 (50 mg L(-1) in drinking water) for 8 weeks and compared with control groups. Arterial BP measurements, various metabolic parameters, aortic histopathology, collagen cross-linking, AGE accumulation, and RAGE protein expression in aortic tissue were determined. Pulsatile parameters were evaluated using a standard Fourier series expansion technique and impulse response function of the filtered aortic input impedance spectra.

KEY RESULTS

LR-90 reduced glycated haemoglobin and triglycerides levels, although it had no effect on the glycaemic status. LR-90 did not affect arterial BP, but prevented the diabetes-induced increase in peripheral resistance and variations in aortic distensibility, as it reduced aortic characteristic impedance by 21%. LR-90 also prevented the elevation in wave reflection factor, as indicated by a 22.5% reduction and an associated increase of 23.5% in wave transit time, suggesting it prevents the augmentation of the systolic load of the left ventricle. Moreover, LR-90 inhibited collagen cross-linking and the accumulation of AGE and RAGE in the vasculature of diabetic rats.

CONCLUSIONS AND IMPLICATIONS

Treatment with LR-90 may impart significant protection against diabetes-induced aortic stiffening and cardiac hypertrophy and provides an additional therapeutic option for treatment of AGE associated diabetic complications.

Cardiovascular outcome associations among cardiovascular magnetic resonance measures of arterial stiffness: the Dallas heart study

BACKGROUND

Cardiovascular magnetic resonance (CMR) has been validated for the noninvasive assessment of total arterial compliance and aortic stiffness, but their associations with cardiovascular outcomes is unknown. The purpose of this study was to evaluate associations of CMR measures of total arterial compliance and two CMR measures of aortic stiffness with respect to future cardiovascular events.

METHODS

The study consisted of 2122 Dallas Heart Study participants without cardiovascular disease who underwent CMR at 1.5 Tesla. Aortic stiffness was measured by CMR-derived ascending aortic distensibility and aortic arch pulse wave velocity. Total arterial compliance was calculated by dividing left ventricular stroke volume by pulse pressure. Participants were monitored for cardiovascular death, non-fatal cardiac events, and non-fatal extra-cardiac vascular events over 7.8 ± 1.5 years. Cox proportional hazards regression was used to assess for associations between CMR measures and cardiovascular events.

RESULTS

Age, systolic blood pressure, and resting heart rate were independently associated with changes in ascending aortic distensibility, arch pulse wave velocity, and total arterial compliance (all p < .0001). A total of 153 participants (6.9%) experienced a cardiovascular event. After adjusting for traditional risk factors, total arterial compliance was modestly associated with increased risk for composite events (HR 1.07 per 1SD, p = 0.03) while the association between ascending aortic distensibility and composite events trended towards significance (HR 1.18 per 1SD, p = 0.08). Total arterial compliance and aortic distensibility were independently associated with nonfatal cardiac events (HR 1.11 per 1SD, p = 0.001 and HR 1.45 per 1SD, p = 0.0005, respectively), but not with cardiovascular death or nonfatal extra-cardiac vascular events. Arch pulse wave velocity was independently associated with nonfatal extra-cardiac vascular events (HR 1.18 per 1SD, p = 0.04) but not with cardiovascular death or nonfatal cardiac events.

CONCLUSIONS

In a multiethnic population free of cardiovascular disease, CMR measures of arterial stiffness are associated with future cardiovascular events. Total arterial compliance and aortic distensibility may be stronger predictors of nonfatal cardiac events, while pulse wave velocity may be a stronger predictor of nonfatal extra-cardiac vascular events.

The association between aortic distensibility and coronary flow reserve in newly diagnosed diabetic patients

INTRODUCTION

Aortic distensibility (AD) is an important parameter affecting coronary hemodynamics. Coronary flow velocity reserve (CFVR) is a reliable marker of coronary endothelial function in diabetic patients. The aim of this study was to investigate the association between AD and CFVR in newly diagnosed diabetic patients.

METHOD

We studied 77 patients with newly diagnosed diabetes mellitus (DM) and 30 age- and sex-matched healthy control subjects. CFVR was calculated as the hyperemic to resting coronary diastolic velocities ratio by using transthoracic echocardiography. Pulse pressure (PP) and AD were calculated.

RESULTS

Fasting blood glucose, HbA1c and PP were significantly higher in patients with diabetes (P < 0.001, P < 0.001 and P = 0.009, respectively). Other clinical and demographical characteristics, laboratory findings and echocardiographic findings were similar in both groups (P > 0.05, for all). The measurement of CFVR and AD in patients with diabetes were significantly lower compared with the controls (P < 0.001 and P = 0.001, respectively). CFVR was significantly negatively correlated with age, body mass index, HbA1c, systolic blood pressure, and PP, while significantly positively correlated with AD (P < 0.05, for all). Multivariate regression analysis showed that only AD (β = 0.485, P < 0.0001) and HbA1c (β = -0.362, P < 0.0001) were independently associated with CFVR. The cutoff value of AD obtained by the receiver operator characteristic (ROC) curve analysis was 2.44 for the prediction of impaired CFVR.

CONCLUSION

Aortic distensibility and HbA1c were independently associated with CFVR. The decrease in AD may be used as a marker of impaired coronary microcirculation in asymptomatic diabetic patients.

Serum 25-hydroxyvitamin D level is associated with aortic distensibility and left ventricle hypertrophy in newly diagnosed type 2 diabetes mellitus

We aimed to evaluate the association between serum vitamin D status and elastic properties of aorta in patients with diabetes mellitus (DM). We studied 136 patients with newly diagnosed DM (mean age: 62.9 ± 10.6 years). Serum 25-hydroxyvitamin D was measured using a direct competitive chemiluminescent immunoassay. Aortic distensibility was calculated from the echocardiographically derived ascending aorta diameters and haemodynamic pressure measurements. Left ventricle mass index (LVMI) was determined according to the Devereux formula. Multiple linear regression analysis showed that vitamin D level is independently associated with LVMI (β = -0.259, p = 0.001), aortic distensibility (β = 0.369, p < 0.001), high-sensitive C-reactive protein (hs-CRP) (β = -0.220, p = 0.002) and body mass index (β = -0.167, p = 0.015) in patients with DM. In diabetic patients, serum 25-hydroxyvitamin D level is independently associated with aortic distensibility. Vitamin D may play a role on pathogenesis of impaired elastic properties of aorta in type 2 DM.

Effect of radiotheraphy on impaired aortic elasticity and stiffness in patients with breast cancer

We evaluated the effect of radiotherapy (RT) on the elastic properties of the aorta using echocardiography in patients with breast cancer (BC). A total of 105 women with left-sided epidermal growth factor receptor 2 (erb-2) BC were divided into 2 groups, group 1 with patients who did not receive RT and group 2 with patients who received RT. In all patients, echocardiographic examination and serum high-sensitivity C-reactive protein (hs-CRP) levels were determined. A significant decrease in aortic distensibility (AD) and increase in hs-CRP were seen from group 1 to group 2. The AD was inversely correlated with left ventricle diastolic diameter, systolic blood pressure (SBP), left atrial diameter, age, and RT dose. The AD was significantly related to age, SBP, and RT dose. Increased RT dose is significantly correlated with impaired elastic properties that may contribute to the relation of RT and increased rate of cardiovascular events among patients with BC who received RT.

Aortic distensibility and extent and complexity of coronary artery disease in patients with stable hypertensive and nonhypertensive coronary artery disease

OBJECTIVE

To assess the relationship between aortic distensibility (AD) and the extent and complexity of atherosclerotic lesions assessed with SYNTAX score (SS) in patients with stable coronary artery disease.

SUBJECTS AND METHODS

Three hundred and seventy-six consecutive patients (230 males and 146 females; mean age: 61.6 ± 9.9 years) with angiographically proven coronary artery disease were included in the study. The SS was calculated using the SS algorithm on the baseline diagnostic angiogram in the 376 patients. AD was calculated from the echocardiographically derived ascending aorta diameters and hemodynamic pressure measurements in all patients. Frequencies of risk factors, biochemical and hematological data were recorded. The patients were divided into two groups according to the median AD value as AD(low) and AD(high) groups.

RESULTS

The SS was higher in the AD(low) group compared with the AD(high) group (18.5 ± 10.2 vs. 8.3 ± 5.9, p < 0.001). The AD was independently related to age (β = -0.104, p = 0.019), hypertension (β = -0.202, p < 0.001) and SS (β = -0.457, p < 0.001) and was more strongly associated with SS in hypertensive patients compared to nonhypertensive patients (r = -0.524 vs. r = -0.414, p < 0.001 for all).

CONCLUSION

The findings showed that impaired AD might be an independent predictor for the severity of coronary atherosclerosis, particularly in patients with hypertension.

Aminoguanidine prevents age-related aortic stiffening in Fisher 344 rats: aortic impedance analysis

(1) We determined the effects of long-term treatment with aminoguanidine (AG), an inhibitor of advanced glycation end products, on the mechanical properties of the arterial system in aged Fisher 344 rats, using the aortic impedance analysis. (2) Normotensive rats were treated from 18 to 24 months with AG (1 g/l-1 in drinking water) and compared with a control group. Pulsatile aortic pressure and flow signals were measured and then subjected to Fourier transformation for the analysis of aortic input impedance. Wave transit time was determined using the impulse response function of the filtered aortic input impedance spectra. (3) With no alteration in body weight, rats treated with AG had decreased heart weight compared with the aged untreated controls. (4) AG did not affect arterial blood pressure; however, the age-related increase in total peripheral resistance was prevented by AG. (5) AG retarded the age-related decline in aortic distensibility, as evidenced by a reduction of 25.2% in aortic characteristic impedance and an increase of 28.1% in wave transit time. (6) Meanwhile, the increase in wave reflection factor in aging rats was reduced by 32.3% by AG. Both the increased wave transit time and the decreased wave reflection factor suggest that AG may prevent the age-related augmentation in systolic loading condition for the left ventricle coupled to the arterial system. (7) We conclude that long-term treatment with AG may impart significant protection against aortic stiffening and cardiac hypertrophy in aged Fisher 344 rats.

Pencil excitation with interleaved fourier velocity encoding: NMR measurement of aortic distensibility

A technique is presented for rapidly and noninvasively determining aortic distensibility, by NMR measurement of pulse-wave velocity in the aorta. A cylinder of magnetization is excited along the aorta, with Fourier-velocity encoding and readout gradients applied along the cylinder axis. Cardiac gating and data interleaving improve the effective time resolution to as high as 3 ms. Wave velocities are determined from the position of the foot of the flow wave in the velocity profiles. Evidence of helical flow distal to the aortic arch can be seen in normal subjects, while disturbed flow patterns are visible in patients with aneurysms and dissections.

A one-dimensional velocity technique for NMR measurement of aortic distensibility

A technique is presented for rapidly and noninvasively determining aortic distensibility, by NMR measurement of wave velocity in the aorta. A two-dimensional NMR selective-excitation pulse is used to repeatedly excite a cylinder of magnetization in the aorta, with magnetization read out along the cylinder axis each time. A toggled bipolar flow-encoding pulse is applied prior to readout, to produce a non-dimensional phase-contrast flow image. Cardiac gating and data interleaving are employed to improve the effective time resolution to 2 ms. Wave velocities are determined from the slope of the leading edge of flow measured on the resulting M-mode velocity image. The technique is sensitive over a range of distensibilities from 10(-6) to 10(-3) m s2/kg. The average value in the descending thoracic aorta in seven normal subjects was found to be 4.8 x 10(-5) m s2/kg, with a significant inverse correlation with age.