Aortic stiffness determines diastolic blood flow reversal in the descending thoracic aorta: potential implication for retrograde embolic stroke in hypertension

The value of diastolic flow reversal in the descending thoracic aorta as a determinant of invasively measured aortic pulse pressure

AIM

Although the diastolic flow reversal of the descending aorta has been recognized in patients with aortic regurgitation, its generation without this condition is still unknown. This study was performed to investigate whether flow patterns of the descending thoracic aorta, as measured by echocardiography, can represent invasively measured aortic pulse pressure (APP).

METHODS

A total of 100 patients (age, 62.3±11.0 years; men, 62.0%) undergoing invasive coronary angiography (ICA) was analyzed. APP was measured at ascending thoracic aorta using pigtail catheter before ICA. Flow in the descending thoracic aorta was assessed using pulse wave Doppler echocardiography, and R/F ratio was defined as reverse peak velocity (R)/forward peak velocity (F).

RESULTS

Eighty patients (80.0%) had obstructive coronary artery disease (CAD) (≥50% stenosis of one or more epicardial coronary arteries) in ICA. APP and R/F ratio were significantly higher in patients with obstructive CAD than those without (P<.05 for each). Both R/F ratio (β=0.379, P<.001) and APP (β=0.255, P<.001) were positively correlated with age. In simple linear regression analysis, there was a significant positive correlation between R/F ratio and APP (β=0.266, P<.001). This correlation remained significant even after controlling for potential confounders including age, gender, E/e', and left atrial volume index in multiple linear regression analysis (β=0.193, P=.036).

CONCLUSIONS

R/F ratio may be independently associated with APP in patients undergoing ICA.

Focus on the Novel Cardiovascular Drug LZC696: from Evidence to Clinical Consideration

LCZ696, a first-in-class angiotensin receptor neprilysin inhibitor (ARNI), is comprised of the angiotensin receptor blocker valsartan and the neprilysin inhibitor pro-drug sacubitril (AHU377). After oral administration, AHU377 is rapidly metabolized to the active neprilysin inhibitor LBQ657. LCZ696 exerts its effects of diuresis, natriuresis, vasodilation and aldosterone secretion inhibition through simultaneous renin-angiotensin-aldosterone system (RAAS) blockade and natriuretic peptides system (NPS) enhancement. Powerful evidence including PARAMETER and PRARDIGM-HF trials have shown that LCZ696 outperforms RAAS inhibition in treating patients with hypertension and heart failure with reduced ejection fraction (HFrEF), and is well tolerated. In addition, accumulating evidence also suggests its potential use in heart failure with preserved ejection fraction (HFpEF), chronic kidney disease (CKD), post-myocardium infarction (post-MI) and stroke. Both the FDA and CHMP have approved LCZ696 for treatment of HFrEF. Despite all this, some special issues (e.g. use in specific subgroups, adverse events, contraindications and cost-effectiveness analysis) should be considered before its implementation in clinical practice.

Aortic Atherosclerosis Determines Increased Retrograde Blood Flow as a Potential Mechanism of Retrograde Embolic Stroke

BACKGROUND

Retrograde brain embolization from complex plaques of the proximal descending aorta (DAo) has been identified as a new potential mechanism of stroke. Our purpose was to identify predictors of increased retrograde aortic blood flow indicating an elevated risk of brain embolization from the DAo.

METHODS

A total of 485 patients with acute ischemic stroke were prospectively included and underwent transesophageal echocardiography. Blood flow velocities in the proximal DAo were studied using 2D pulse-wave Doppler ultrasound. Velocity-time integrals (VTI) were calculated for antegrade and retrograde velocity directions. The ratio (VTIretrograde/VTIantegrade) was used to estimate retrograde flow extent. Associations between patient demographics, cardiovascular risk factors, echocardiographic parameters, and VTIratio were analyzed using multivariate linear regression.

RESULTS

Retrograde blood flow in the DAo occurred in all patients. Velocity profiles in the proximal DAo were as follows (mean ± SD): VTIantegrade = 21.1 ± 6.5, VTIretrograde = 11.0 ± 3.6, and VTIratio = 0.54 ± 0.16. Diameter (r = 0.25, p < 0.001), presence of complex plaques (r = 0.12, p = 0.007), and reduced strain of the DAo (r = -0.23, p < 0.001) had significant partial effects in a predictor model based on predefined variables, which predicted 26% (adjusted R2 = 0.26) of the variance in VTIratio. A unit increase in the DAo diameter was associated with a 2% increase in VTIratio (95% CI 1-2.8%, p < 0.001). Presence of complex plaques increased VTIratio by 7% (95% CI 2-13%, p = 0.007) and an increase in strain by 0.1 indicated a decrease in VTIratio by about 11% (95% CI 6.2-15.5%, p < 0.001). Complex atheroma was found in the proximal DAo of 79 subjects, of which 40 (50.6%) had a VTIratio above average (VTIratio ≥0.54) compared to 87 of 261 (33.3%) patients without any complex plaques (p < 0.001). Twenty-five of 79 (31.7%) patients with complex DAo plaques had a VTIratio ≥0.60, which indicates a high likelihood of retrograde pathline length of ≥3 cm and thus increased risk of retrograde cerebral embolization. Stroke etiology of those 25 patients was determined in 13 and cryptogenic in 12 cases.

CONCLUSIONS

Retrograde blood flow in the DAo was found in all stroke patients. However, it increased further in patients with concomitant complex plaques, low strain, and/or large aortic diameter, that is, in those with atherosclerosis of the DAo. Accordingly, such patients may be predisposed to retrograde embolization in case of occurrence of a complex plaque in proximity to a brain-supplying artery.

Aortic–Brachial Pulse Wave Velocity Ratio

Aortic stiffness, a cardiovascular risk factor, depends on the operating mean arterial pressure (MAP). The impact of aortic stiffness on cardiovascular outcomes is proposed to be mediated by the attenuation or the reversal of the arterial stiffness gradient. We hypothesized that arterial stiffness gradient is less influenced by changes in MAP. We aimed to study the relationship between MAP and aortic stiffness, brachial stiffness, and arterial stiffness gradient. In a cross-sectional study of a dialysis cohort (group A, n=304) and a cohort of hypertensive or kidney transplant recipient with an estimated glomerular filtration rate of >45 mL/min/1.73 m 2 (group B, n=114), we assessed aortic and brachial stiffness by measuring carotid–femoral and carotid–radial pulse wave velocities (PWV). We used aortic–brachial PWV ratio as a measure of arterial stiffness gradient. Although there was a positive relationship between MAP and carotid–femoral PWV ( R 2 =0.10 and 0.08; P <0.001 and P =0.003) and MAP and carotid–radial PWV ( R 2 =0.22 and 0.12; P <0.001 and P <0.001), there was no statistically or clinically significant relationship between MAP and aortic–brachial PWV ratio ( R 2 =0.0002 and 0.0001; P =0.8 and P =0.9) in group A and B, respectively. Dialysis status and increasing age increased the slope of the relationship between MAP and cf-PWV. However, we found no modifying factor (age, sex, dialysis status, diabetes mellitus, cardiovascular disease, and class of antihypertensive drugs) that could affect the lack of relationship between MAP and aortic–brachial PWV ratio. In conclusion, these results suggest that aortic–brachial PWV ratio could be considered as a blood pressure–independent measure of vascular aging.

Cross-Sectional Associations of Flow Reversal, Vascular Function, and Arterial Stiffness in the Framingham Heart Study

OBJECTIVE

Experimental studies link oscillatory flow accompanied by flow reversal to impaired endothelial cell function. The relation of flow reversal with vascular function and arterial stiffness remains incompletely defined.

APPROACH AND RESULTS

We measured brachial diastolic flow patterns along with vasodilator function in addition to tonometry-based central and peripheral arterial stiffness in 5708 participants (age 47±13 years, 53% women) in the Framingham Heart Study Offspring and Third Generation cohorts. Brachial artery diastolic flow reversal was present in 35% of the participants. In multivariable regression models, the presence of flow reversal was associated with lower flow-mediated dilation (3.9±0.2 versus 5.0±0.2%; P<0.0001) and reactive hyperemic flow velocity (50±0.99 versus 57±0.93 cm/s; P<0.0001). The presence of flow reversal (compared with absence) was associated with higher central aortic stiffness (carotid-femoral pulse wave velocity 9.3±0.1 versus 8.9±0.1 m/s), lower muscular artery stiffness (carotid-radial pulse wave velocity 9.6±0.1 versus 9.8±0.1 m/s), and higher forearm vascular resistance (5.32±0.03 versus 4.66±0.02 log dyne/s/cm⁵; P<0.0001). The relations of diastolic flow velocity with flow-mediated dilation, aortic stiffness, and forearm vascular resistance were nonlinear, with a steeper decline in vascular function associated with increasing magnitude of flow reversal.

CONCLUSIONS

In our large, community-based sample, brachial artery flow reversal was common and associated with impaired vasodilator function and higher aortic stiffness. Our findings are consistent with the concept that flow reversal may contribute to vascular dysfunction.

Fortune or misfortune: asymptomatic, delayed presentation of complete dehiscence of mechanical aortic valve conduit and pseudoaneurysm

Complete dehiscence of a composite aortic valve graft with pseudoaneurysm formation is a rare complication following aortic root replacement. This complication often takes place in the setting of acute graft infection and accompanies symptoms of heart failure, valve insufficiency or sepsis. We present a delayed, asymptomatic presentation of this complication in a young man with distant history of aortic root replacement and medically treated prosthetic valve endocarditis a year postoperatively. He had been non-adherent to warfarin over 10 years, but otherwise maintained a healthy life. After being lost to follow-up, he re-presented 12 years after the initial operation with new-onset seizures. Echocardiogram revealed complete dehiscence of a composite valved conduit at the proximal anastomosis site with a resultant large pseudoaneurysm. The patient underwent an urgent re-operation with resection of the pseudoaneurysm and insertion of a tissue valved conduit. He had an uncomplicated postoperative recovery and promised close follow-up on discharge.

Transcathether Valve Replacement and Valve Repair

Transcatheter aortic valve replacement for treatment of aortic stenosis has now become an accepted alternative to surgical valve replacement for some patients. In addition, transcatheter mitral valve repair is also routinely used in high surgical risk patients with mitral regurgitation. Other transcatheter procedures are in rapid development. The current review attempts to summarize the procedures and echocardiographic imaging used for transcatheter valve replacement or valve repair.

Aortic Arch Stiffness Is Associated With Incipient Brain Injury in Patients With Hypertension

BACKGROUND

It has been shown that microstructural brain tissue damage can be detected in hypertension patients, while the underlying mechanisms are not fully understood. We aim to explore the association between diffusion tensor imaging (DTI) measures of brain injury and aortic arch pulse wave velocity (PWV) in hypertensive patients without clinically manifest cerebrovascular disease.

METHODS

Sixty-six hypertension patients (30 men, mean age 46±14 years) were prospectively included. Aortic arch PWV was assessed using velocity-encoded magnetic resonance imaging (VE-MRI). Brain tissue integrity was assessed by using DTI. Multivariable linear regression analysis was performed to assess the association between aortic arch PWV and fractional anisotropy (FA), axial diffusivity (AxD), and radial diffusivity (RD).

RESULTS

Increased aortic arch PWV was associated with decreased white matter FA (β = -0.30, P = 0.018), increased gray matter AxD (β = 0.28, P = 0.016), and increased gray and white matter RD (β = 0.30, P = 0.008 and β = 0.35, P = 0.003, respectively). These effects were independent of age, sex, body mass index, smoking, and white matter hyperintensity (WMH) volume.

CONCLUSIONS

Aortic arch stiffness relates to incipient brain injury before overt brain abnormalities may become apparent in patients with hypertension.

BAY 41-2272 Treatment Improves Acetylcholine-Induced Aortic Relaxation in L-NAME Hypertensive Rats

Hypertension, an emerging problem of recent era, and many pathophysiological factors are participating to produce the disease. Nitric oxide (NO) is an important constituent to ameliorate hypertensive condition. Inhibition of endogenous NO synthase by L-N^G-Nitroarginine methyl ester (L-NAME) was responsible for generating hypertension in rats. BAY 41-2272 (5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]-pyrimidin-4-ylamine), a soluble guanylyl cyclase activator, restricts rise of blood pressure and shows cardioprotective activity. The aim of the present study was to analyze effect of short-term BAY 41-2272 treatment on blood pressure and vascular function. Male Wistar rats were randomly divided into three groups such as control (group-A), hypertensive (group-B), and BAY 41-2272-treated hypertensive (group-C) rats. Normal saline was administered intramuscularly to control rats for last 3 days (days 40, 41, and 42) of total 42 days treatment, whereas rats of group-B and group-C were treated with L-NAME hydrochloride in drinking water at 50 mg/kg body weight daily for 42 days. Also, normal saline and BAY 41-2272 were administered for last 3 days at two different dosages at 1 and 3 mg/kg body weight/day intramuscularly to group-B and group-C rats, respectively. Administration of BAY 41-2272 for 3 days was not sufficient enough to decrease mean arterial pressure of hypertensive rats significantly. BAY at both the treatment dosages significantly ameliorate acetylcholine-induced maximal aortic relaxation compared with BAY-untreated hypertensive rats. Findings of the present study indicate that even shorter period of BAY 41-2272 treatment (3 days) improves vascular relaxation.

Central blood pressure and chronic kidney disease

In this review, we focused on the relationship between central blood pressure and chronic kidney diseases (CKD). Wave reflection is a major mechanism that determines central blood pressure in patients with CKD. Recent medical technology advances have enabled non-invasive central blood pressure measurements. Clinical trials have demonstrated that compared with brachial blood pressure, central blood pressure is a stronger risk factor for cardiovascular (CV) and renal diseases. CKD is characterized by a diminished renal autoregulatory ability, an augmented direct transmission of systemic blood pressure to glomeruli, and an increase in proteinuria. Any elevation in central blood pressure accelerates CKD progression. In the kidney, interstitial inflammation induces oxidative stress to handle proteinuria. Oxidative stress facilitates atherogenesis, increases arterial stiffness and central blood pressure, and worsens the CV prognosis in patients with CKD. A vicious cycle exists between CKD and central blood pressure. To stop this cycle, vasodilator antihypertensive drugs and statins can reduce central blood pressure and oxidative stress. Even in early-stage CKD, mineral and bone disorders (MBD) may develop. MBD promotes oxidative stress, arteriosclerosis, and elevated central blood pressure in patients with CKD. Early intervention or prevention seems necessary to maintain vascular health in patients with CKD.

Molecular mechanism of endothelial and vascular aging: implications for cardiovascular disease

Western societies are aging due to an increasing life span, decreased birth rates, and improving social and health conditions. On the other hand, the prevalence of cardiovascular (CV) and cerebrovascular (CBV) diseases rises with age. Thus, in view of the ongoing aging pandemic, it is appropriate to better understand the molecular pathways of aging as well as age-associated CV and CBV diseases. Oxidative stress contributes to aging of organs and the whole body by an accumulation of reactive oxygen species promoting oxidative damage. Indeed, increased oxidative stress produced in the mitochondria and cytosol of heart and brain is a common denominator to almost all CV and CBV diseases. The mitochondrial adaptor protein p66(Shc) and the family of deacetylase enzymes, the sirtuins, regulate the aging process, determine lifespan of many species and are involved in CV diseases. GDF11, a member of TGFβ superfamily with homology to myostatin also retards the aging process via yet unknown mechanisms. Recent evidence points towards a promising role of this novel 'rejuvenation' factor in reducing age-related heart disease. Finally, telomere length is also involved in aging and the development of age-related CV dysfunction. This review focuses on the latest scientific advances in understanding age-related changes of the CV and CBV system, as well as delineating potential novel therapeutic targets derived from aging research for CV and CBV diseases.

Contributing Mechanisms of Aortic Atheroma in Ischemic Cerebrovascular Disease

In recent years, the correlation between aortic atheroma (AA) and the occurrence and recurrence of ischemic cerebrovascular disease (ICVD) has attracted much attention, but the contributory mechanisms remain controversial. This review analyzes related research on the roles of AA in ICVD, and demonstrates the correlation between the formation and development of AA and abnormal metabolism, inflammation, hemodynamic changes, and other contributory factors. The presence of complex aortic plaque (CAP) in the ascending aorta and aortic arch increases the risk of cerebral embolism and degree of injury, while the association between CAP in the descending aorta and cerebral embolism remains ambiguous. AA also functions as an indicator of atherosclerosis burden as well as hypercoagulability, which may further increase the risk of ICVD. Further study on the relationship of AA to ICVD will improve diagnosis and treatment in clinical practice.

Correlation between beat-to-beat blood pressure variability and arterial stiffness in healthy adults in the cold pressor test

Blood pressure variability has a great effect on the progression of arterial stiffness, which has increasingly become a hot research topic recently. In this study, beat-to-beat recordings of blood pressure (BP), heart rate, cardiac output, total peripheral resistance, and left ventricular ejection time during the cold pressor test (CPT) were analyzed together. We recruited 101 young Chinese subjects (aged 21-33) with no known history of high BP into the study. We found that the mean level of beat-to-beat BP and the average real variability and successive variation of beat-to-beat diastolic BP variability in the CPT showed significant correlations with pulse wave velocity (PWV) (r = 0.22-0.34, P < 0.05). In addition, we also found correlations between beat-to-beat heart rate and heart rate variability indices and PWV in each phase of the CPT. At the same time, the standard deviation of the R-R intervals and square root of the mean squared difference of successive R-R intervals in the cold stimulus phase also showed significant correlations with PWV (r = 0.23-0.24, P < 0.05). In conclusion, the level and variability of beat-to-beat BP have a strong influence on arterial stiffness.

Arterial Stiffness Gradient

BACKGROUND

Aortic stiffness is a strong predictor of cardiovascular mortality in various clinical conditions. The aim of this review is to focus on the arterial stiffness gradient, to discuss the integrated role of medium-sized muscular conduit arteries in the regulation of pulsatile pressure and organ perfusion and to provide a rationale for integrating their mechanical properties into risk prediction.

SUMMARY

The physiological arterial stiffness gradient results from a higher degree of vascular stiffness as the distance from the heart increases, creating multiple reflective sites and attenuating the pulsatile nature of the forward pressure wave along the arterial tree down to the microcirculation. The stiffness gradient hypothesis simultaneously explains its physiological beneficial effects from both cardiac and peripheral microcirculatory points of view. The loss or reversal of stiffness gradient leads to the transmission of a highly pulsatile pressure wave into the microcirculation. This suggests that a higher degree of stiffness of medium-sized conduit arteries may play a role in protecting the microcirculation from a highly pulsatile forward pressure wave. Using the ratio of carotid-femoral pulse wave velocity (PWV) to carotid-radial PWV, referred to as PWV ratio, a recent study in a dialysis cohort has shown that the PWV ratio is a better predictor of mortality than the classical carotid-femoral PWV.

KEY MESSAGES

Theoretically, the use of the PWV ratio seems more logical for risk determination than aortic stiffness as it provides a better estimation of the loss of stiffness gradient, which is the unifying hypothesis that explains the impact of aortic stiffness both on the myocardium and on peripheral organs.

Aortic Blood Flow Reversal Determines Renal Function

Aortic stiffness determines the glomerular filtration rate (GFR) and predicts the progressive decline of the GFR. However, the underlying pathophysiological mechanism remains obscure. Recent evidence has shown a close link between aortic stiffness and the bidirectional (systolic forward and early diastolic reverse) flow characteristics. We hypothesized that the aortic stiffening–induced renal dysfunction is attributable to altered central flow dynamics. In 222 patients with hypertension, Doppler velocity waveforms were recorded at the proximal descending aorta to calculate the reverse/forward flow ratio. Tonometric waveforms were recorded to measure the carotid-femoral (aortic) and carotid-radial (peripheral) pulse wave velocities, to estimate the aortic pressure from the radial waveforms, and to compute the aortic characteristic impedance. In addition, renal hemodynamics was evaluated by duplex ultrasound. The estimated GFR was inversely correlated with the aortic pulse wave velocity, reverse/forward flow ratio, pulse pressure, and characteristic impedance, whereas it was not correlated with the peripheral pulse wave velocity or mean arterial pressure. The association between aortic pulse wave velocity and estimated GFR was independent of age, diabetes mellitus, hypercholesterolemia, and antihypertensive medication. However, further adjustment for the aortic reverse/forward flow ratio and pulse pressure substantially weakened this association, and instead, the reverse/forward flow ratio emerged as the strongest determinant of estimated GFR ( P =0.001). A higher aortic reverse/forward flow ratio was also associated with lower intrarenal forward flow velocities. These results suggest that an increase in aortic flow reversal (ie, retrograde flow from the descending thoracic aorta toward the aortic arch), caused by aortic stiffening and impedance mismatch, reduces antegrade flow into the kidney and thereby deteriorates renal function.

Brachial-ankle pulse wave velocity for predicting functional outcome in acute stroke

BACKGROUND AND PURPOSE

We investigated whether the brachial-ankle pulse wave velocity (baPWV) has prognostic value for predicting functional outcome after acute cerebral infarction and whether the prognostic value differs between stroke subtypes.

METHODS

We included 1091 consecutive patients with first-ever acute cerebral infarction who underwent baPWV measurements. Stroke subtypes were classified using the Trial of Org 10172 in Acute Stroke Treatment classification. Poor functional outcomes were defined as modified Rankin Scale score >2 at 3 months after stroke onset.

RESULTS

We noted that 181 (16.59%) patients had a poor functional outcome. In multivariate logistic regression, patients in the highest tertile of baPWV (>22.25 m/s) were found to be at increased risk for poor functional outcome (adjusted odds ratio, 1.88; 95% confidence interval, 1.06-3.40) compared with those in the lowest tertile (<17.55 m/s). No significant interaction between baPWV and stroke subtype was noted. Receiver operating characteristic curve analysis indicated that the addition of baPWV to the prediction model significantly improved the discrimination ability for poor functional outcome.

CONCLUSIONS

baPWV has an independent prognostic value for predicting functional outcome after acute cerebral infarction. The prognostic value did not differ according to the stroke subtype.

Cerebral hemodynamics in normal aging: central artery stiffness, wave reflection, and pressure pulsatility

Blood ejected from the left ventricle perfuses the brain via central elastic arteries, which stiffen with advancing age and may elevate the risk of end-organ damage. The purpose of this study was to determine the impact of central arterial aging on cerebral hemodynamics. Eighty-three healthy participants aged 22 to 80 years underwent the measurements of cerebral blood flow (CBF) and CBF velocity (CBFV) using magnetic resonance imaging (MRI) and transcranial Doppler, respectively. The CBF pulsatility was determined by the relative amplitude of CBFV to the mean value (CBFV%). Central arterial stiffness (carotid-femoral pulse wave velocity), wave reflection (carotid augmentation index), and pressure were measured using applanation tonometry. Total volume of white-matter hyperintensity (WMH) was quantified from MR images. Total CBF decreased with age while systolic and pulsatile CBFV% increased and diastolic CBFV% decreased. Women showed greater total CBF and lower cerebrovascular resistance than men. Diastolic CBFV% was lower in women than in men. Age- and sex-related differences in CBF pulsatility were independently associated with carotid pulse pressure and arterial wave reflection. In older participants, higher pulsatility of CBF was associated with the greater total volume of WMH. These findings indicate that central arterial aging has an important role in age-related differences in cerebral hemodynamics.

Complex atheromatous plaques in the descending aorta and the risk of stroke: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

Proximal aortic plaques, especially in the aortic arch, have already been established as an important cause of stroke and peripheral embolism. However, aortic plaques situated in the descending thoracic aorta have recently been postulated as a potential embolic source in patients with cryptogenic cerebral infarction through retrograde aortic flow. The aim of the present study was to evaluate the potential association of descending aorta atheromatosis with cerebral ischemia.

METHODS

We conducted a systematic review and meta-analysis of all available prospective observational studies reporting the prevalence of complex atheromatous plaques in the descending aorta in patients with stroke and in unselected populations undergoing examination with transesophageal echocardiography.

RESULTS

We identified 11 eligible studies including a total of 4000 patients (667 patients with stroke and 3333 unselected individuals; mean age, 65 years; 55% men). On baseline transesophageal echocardiograpic examination, the prevalence of complex atheromatous plaques in the descending aorta was higher (P=0.001) in patients with stroke (25.4%; 95% confidence interval, 14.6-40.4%) compared with unselected individuals (6.1%; 95% confidence interval, 3.4-10%). However, no significant difference (P=0.059) in the prevalence of complex atheromatous plaques in the descending aorta was found between patients with cryptogenic (21.8%; 95% confidence interval, 17.5-26.9%) and unclassified (28.3%; 95% confidence interval, 23.9-33.1%) cerebral infarction.

CONCLUSIONS

Our findings indicate that the presence of complex plaques in the descending aorta is presumably a marker of generalized atherosclerosis and high vascular risk. The present analyses do not provide any further evidence for a direct causal relationship between descending aorta atherosclerosis and cerebral embolism.

Effect of acute resistance exercise on carotid artery stiffness and cerebral blood flow pulsatility

Arterial stiffness is associated with cerebral flow pulsatility. Arterial stiffness increases following acute resistance exercise (RE). Whether this acute RE-induced vascular stiffening affects cerebral pulsatility remains unknown. Purpose: To investigate the effects of acute RE on common carotid artery (CCA) stiffness and cerebral blood flow velocity (CBFv) pulsatility. Methods: Eighteen healthy men (22 ± 1 yr; 23.7 ± 0.5 kg·m⁻²) underwent acute RE (5 sets, 5-RM bench press, 5 sets 10-RM bicep curls with 90 s rest intervals) or a time control condition (seated rest) in a randomized order. CCA stiffness (β-stiffness, Elastic Modulus (Ep)) and hemodynamics (pulsatility index, forward wave intensity, and reflected wave intensity) were assessed using a combination of Doppler ultrasound, wave intensity analysis and applanation tonometry at baseline and 3 times post-RE. CBFv pulsatility index was measured with transcranial Doppler at the middle cerebral artery (MCA). Results: CCA β-stiffness, Ep and CCA pulse pressure significantly increased post-RE and remained elevated throughout post-testing (p < 0.05). No changes in MCA or CCA pulsatility index were observed (p > 0.05). There were significant increases in forward wave intensity post-RE (p < 0.05) but not reflected wave intensity (p > 0.05). Conclusion: Although acute RE increases CCA stiffness and pressure pulsatility, it does not affect CCA or MCA flow pulsatility. Increases in pressure pulsatility may be due to increased forward wave intensity and not pressure from wave reflections.

Hemodynamic correlates of late systolic flow velocity augmentation in the carotid artery

Background. The contour of the common carotid artery (CCA) blood flow velocity waveform changes with age; CCA flow velocity increases during late systole, and this may contribute to cerebrovascular disease. Late systolic flow velocity augmentation can be quantified using the flow augmentation index (FAIx). We examined hemodynamic correlates of FAIx to gain insight into determinants of CCA flow patterns. Methods. CCA Doppler ultrasound and wave intensity analysis (WIA) were used to assess regional hemodynamics in 18 young healthy men (age 22 ± 1 years). Forward waves (W₁) and backward waves (negative area, NA) were measured and used to calculate the reflection index (NA/W₁ = RIx). Additional parameters included W₂ which is a forward travelling expansion/decompression wave of myocardial origin that produces suction, CCA single-point pulse wave velocity (PWV) as a measure of arterial stiffness, and CCA pressure augmentation index (AIx). Results. Primary correlates of FAIx included W₂ (r = − 0.52, P < 0.05), _logRIx (r = 0.56, P < 0.05), and AIx (r = 0.60, P < 0.05). FAIx was not associated with CCA stiffness (P > 0.05). Conclusions. FAIx is a complex ventricular-vascular coupling parameter that is associated with both increased expansion wave magnitude (increased suction from the left ventricle) and increased pressure from wave reflections.

Role of mitochondrial oxidative stress in hypertension

Based on mosaic theory, hypertension is a multifactorial disorder that develops because of genetic, environmental, anatomical, adaptive neural, endocrine, humoral, and hemodynamic factors. It has been recently proposed that oxidative stress may contribute to all of these factors and production of reactive oxygen species (ROS) play an important role in the development of hypertension. Previous studies focusing on the role of vascular NADPH oxidases provided strong support of this concept. Although mitochondria represent one of the most significant sources of cellular ROS generation, the regulation of mitochondrial ROS generation in the cardiovascular system and its pathophysiological role in hypertension are much less understood. In this review, the role of mitochondrial oxidative stress in the pathophysiology of hypertension and cross talk between angiotensin II signaling, pathways involved in mechanotransduction, NADPH oxidases, and mitochondria-derived ROS are considered. The possible benefits of therapeutic strategies that have the potential to attenuate mitochondrial oxidative stress for the prevention/treatment of hypertension are also discussed.