Pressure-independent relationship of aortic characteristic impedance with left ventricular mass and geometry in untreated hypertension

TEVAR and EVAR, the unknown knowns of the cardiovascular hemodynamics; and the immediate and long-term consequences of fabric material on major adverse clinical outcome

This review discusses the impact of endovascular aneurysm repair on cardiovascular (CV) hemodynamics and the role of stent-graft material, i.e., polytetrafluoroethylene (PTFE) vs. polyester in post-procedural outcomes. Endovascular aneurysm repair has been widely employed in the last decades for thoracic and abdominal aneurysm repair. However, aortic endografts are stiff and alter the native flow hemodynamics. This failure to simulate the native aorta could lead to added strain on the heart, manifesting as increased left ventricular strain, higher pulse pressure, and congestive heart failure later. This could result in adverse CV outcomes. Also, evidence is mounting to support the implication of stent-graft materials, i.e., PTFE vs. polyester, in adverse post-procedural outcomes. However, there is an absence of level one evidence. Therefore, the only way forward is to plan and perform a randomised controlled trial to demonstrate the alterations in the CV hemodynamics in the short and long run and compare the available stent-graft materials regarding procedural and clinical outcomes. We believe the best solution, for now, would be to reduce the stented length of the aorta. At the same time, in the longer term, encourage continuous improvement in stent-graft materials and design.

Combined thoracic endovascular aortic repair and endovascular aneurysm repair and the long-term consequences of altered cardiovascular haemodynamics on morbidity and mortality: case series and literature review

Background

Thoracic and abdominal aortic stent grafts are firmer and more rigid than the native aorta. Aortic implanted devices have been implicated in the development of acute systolic hypertension, elevated pulse pressure, and reduced coronary perfusion.

Case summary

We report four cases of staged thoracic endovascular aortic repair (TEVAR) and then endovascular aneurysm repair (EVAR). All patients had TEVAR first for thoracic aortic aneurysm and later on developed infra-renal abdominal aortic aneurysm (AAA) that required EVAR. There were three males and one female with a median age of 74.5 years (range 67.5-78.5). None of the patients developed aortic-related major clinical adverse effects or required any aortic intervention during their follow-up. However, within 2 years, all patients developed symptomatic left ventricular hypertrophy with diastolic dysfunction. All patients had bilateral lower limb oedema, with on and off chest pain and shortness of breath (SOB), necessitating coronary angiograms, which showed no evidence of coronary artery disease. Three patients died from cardiovascular-related morbidities, and the fourth patient is still complaining of SOB despite a normal coronary angiogram.

Discussion

Aortic-endograft compliance mismatch is an invisible enemy, with troubling consequences for the aorta proximal and distal to the endograft. Aortic stiffness due to vascular endograft could lead to cardiovascular adverse events, even in the absence of direct aortic-related complications. After combined TEVAR and EVAR, the compliance mismatch and elasticity loss are even more pronounced than with TEVAR alone, which necessitates patient monitoring for the development of cardiovascular complications.

Disparate Information Provided by Pulse Wave Velocity versus Other Measures of Aortic Compliance in End-Stage Renal Disease

INTRODUCTION

Unfavorable changes in cardiac and arterial function are related to poor prognosis in chronic kidney disease (CKD). We compared hemodynamic profiles between subjects with end-stage renal disease and 2 control groups with corresponding pulse wave velocities (PWVs).

METHODS

Noninvasive hemodynamics were recorded during passive head-up tilt in CKD stage 5 patients (n = 35), patients with primary hypertension (n = 35, n = 30 with antihypertensive medications), and subjects without cardiovascular or renal diseases and cardiovascular medications (n = 70). The groups were selected to have corresponding age, sex, body mass index, and PWV. Hemodynamic data were captured using whole-body impedance cardiography and radial tonometric pulse wave analysis.

RESULTS

Supine blood pressure did not differ between the groups, but upright diastolic blood pressure was lower in CKD patients than in the 2 control groups (p ≤ 0.001 for both, RANOVA). Despite similar PWV, supine aortic pulse pressure was higher in CKD patients versus nonmedicated subjects (p = 0.029). Two additional measures indicated reduced aortic compliance in CKD patients versus both control groups: lower ratio of stroke index to aortic pulse pressure (p ≤ 0.023) and higher aortic characteristic impedance (p ≤ 0.003). The subendocardial viability ratio was lower in the CKD group than in both control groups (p ≤ 0.039).

CONCLUSION

In the absence of differences in PWV, higher aortic pulse pressure and characteristic impedance, and lower ratio of stroke index to aortic pulse pressure, suggest reduced aortic compliance and impaired left ventricular function in CKD patients. A lower subendocardial viability ratio predisposes the CKD patients to impaired cardiac oxygen supply versus hypertensive patients and nonmedicated controls.

Sex and Gender Aspects in Vascular Ageing - Focus on Epidemiology, Pathophysiology, and Outcomes

Sex and gender are important modifiers of cardiovascular system physiology, pathophysiology, and disease development. The atherosclerosis process, together with the progressive loss of arterial elasticity with age, is a major factor influencing the development of overt cardiovascular, renal, and cerebrovascular disease. While differences between women and men in epidemiology and pathophysiology of vascular ageing are increasingly reported, sex-disaggregated data are still scarcely available for prospective studies. A better knowledge of sex differences in physiological ageing as well as in disease-related changes in vascular ageing trajectories is crucial to avoid misdiagnosis and mistreatment. This review presents key concepts and knowledge gaps identified in vascular ageing due to gonadal function, vascular physiology, pathophysiology, psychosocial factors, pregnancy, and prognostic relevance. Gender roles determine the effectiveness of any cardiovascular preventive strategy and acceptance for non-invasive or invasive diagnostics and therapeutics. Gender differences in health behaviour, also due to sociocultural norms conditioned by society, contribute to behaviours that may lead to premature arterial vascular ageing. These include differences in risk behaviours like smoking, diet, exercise, and in stress, but also conditions such as housing, noise pollution, poverty, disability, and any kind of stigmatisation. The VascAgeNet Gender Expert Group aims to advance the use of non-invasive vascular ageing measures in routine clinical settings by providing facts to fill in the gaps concerning sex and gender differences at each step of this process, and to search for solutions.

Reflected wave intensity increases based on aortic diameter after endovascular aortic therapy in a goat model

Reflected wave increases after endovascular aortic repair (EVAR) in patients with aortic aneurysm. This affects the left ventricular (LV) diastolic function and leads to a poor prognosis. This study aimed to evaluate the relationship between increased reflected wave amplitude and aortic diameter after EVAR. EVAR was performed in seven healthy goats. We assessed wave intensity (WI), aortic diameter, and stiffness parameter β. Moreover, we evaluated the relationship between negative reflected wave (NW, reflected waves toward the heart from the periphery by WI) and other parameters after EVAR. Results showed an increase in stiffness parameter β (3.5 ± 0.3 vs 15.9 ± 4.7, p = 0.018) and a decrease in the change of aortic diameter (6.9 ± 0.7 vs 2.7 ± 0.4%, p = 0.018) after EVAR. The NW was significantly amplified after EVAR from baseline (−589.8 ± 143.4 to  − 1192.3 ± 303.7 mmHg-m/sec³, p = 0.043). The NW showed a significant correlation with maximum aortic diameter (R = 0.707, p = 0.038) and minimum aortic diameter (R = 0.724, p = 0.033). The reflected wave was enhanced after EVAR and was correlated to the aortic diameter at the stent-graft site. It is important to consider that patients with smaller aortic diameters in landing zone who undergo EVAR may develop LV dysfunction.

Aortic Pulse Wave Velocity Predicts Cardiovascular Events and Mortality in Patients Undergoing Coronary Angiography: A Comparison of Invasive Measurements and Noninvasive Estimates

Aortic pulse wave velocity (PWV) is directly related to arterial stiffness. Different methods for the determination of PWV coexist. The aim of this prospective study was to evaluate the prognostic value of PWV in high-risk patients with suspected coronary artery disease undergoing invasive angiography and to compare 3 different methods for assessing PWV. In 1040 patients, invasive PWV (iPWV) was measured during catheter pullback. Additionally, PWV was estimated with a model incorporating age, central systolic blood pressure, and pulse waveform characteristics obtained from noninvasive measurements (estimated PWV). As a third method, PWV was calculated with a formula solely based on age and blood pressure (formula-based PWV). Survival analysis was based on continuous PWV as well as using cutoff values. After a median follow-up duration of 1565 days, 24% of the patients reached the combined end point (cardiovascular events or mortality). Cox proportional hazard ratios per 1 SD were 1.35 for iPWV, 1.37 for estimated PWV, and 1.28 for formula-based PWV (P<0.0001 for all 3 methods) in univariate analysis, remaining statistically significant after comprehensive multivariable adjustments. In a model including a modified risk score for coronary artery disease, iPWV and estimated PWV remained borderline significant. The net reclassification improvement was significant for iPWV (0.173), formula-based PWV (0.181), and estimated PWV (0.230). All 3 methods for the determination of PWV predicted cardiovascular events and mortality in patients with suspected coronary artery disease. This indicates that iPWV as well as both noninvasive estimation methods are suitable for the assessment of arterial stiffness, bearing in mind their individual characteristics.

Carotid and aortic stiffness in essential hypertension and their relation with target organ damage: the CATOD study

OBJECTIVE

The objective of the study is to investigate in the hypertensive population the possible differential association between increased aortic and/or carotid stiffness and organ damage in multiple districts, such as the kidney, the vessels, and the heart.

METHODS

In 314 essential hypertensive patients, carotid-femoral pulse wave velocity (cfPWV, by applanation tonometry) and carotid stiffness (from ultrasound images analysis), together with left ventricular hypertrophy, carotid intima-media thickness, urinary albumin-creatinin ratio, and glomerular filtration rate were measured. Increased cfPWV and carotid stiffness were defined according to either international reference values or the 90th percentile of a local control group (110 age and sex-matched healthy individuals).

RESULTS

When considering the 90th percentile of a local control group, increased cfPWV was associated with reduced glomerular filtration rate, either when carotid stiffness was increased [odds ratio (OR) 13.27 (confidence limits (CL) 95% 3.86-45.58)] or not [OR 7.39 (CL95% 2.25-24.28)], whereas increased carotid stiffness was associated with left ventricular hypertrophy, either when cfPWV was increased [OR 2.86 (CL95% 1.15-7.09)] or not [OR 2.81 (CL95% 1.13-6.97)]. No association between increased cfPWV or carotid stiffness and target organ damage was found when cutoffs obtained by international reference values were used. The concomitance of both increased cfPWV and carotid stiffness did not have an additive effect on organ damage.

CONCLUSION

Aortic and carotid stiffness are differentially associated with target organ damage in hypertensive patients. Regional arterial stiffness as assessed by cfPWV is associated with renal organ damage and local carotid stiffness with cardiac organ damage.

Computational assessment of model-based wave separation using a database of virtual subjects

The quantification of arterial wave reflection is an important area of interest in arterial pulse wave analysis. It can be achieved by wave separation analysis (WSA) if both the aortic pressure waveform and the aortic flow waveform are known. For better applicability, several mathematical models have been established to estimate aortic flow solely based on pressure waveforms. The aim of this study is to investigate and verify the model-based wave separation of the ARCSolver method on virtual pulse wave measurements. The study is based on an open access virtual database generated via simulations. Seven cardiac and arterial parameters were varied within physiological healthy ranges, leading to a total of 3325 virtual healthy subjects. For assessing the model-based ARCSolver method computationally, this method was used to perform WSA based on the aortic root pressure waveforms of the virtual patients. Asa reference, the values of WSA using both the pressure and flow waveforms provided by the virtual database were taken. The investigated parameters showed a good overall agreement between the model-based method and the reference. Mean differences and standard deviations were -0.05±0.02AU for characteristic impedance, -3.93±1.79mmHg for forward pressure amplitude, 1.37±1.56mmHg for backward pressure amplitude and 12.42±4.88% for reflection magnitude. The results indicate that the mathematical blood flow model of the ARCSolver method is a feasible surrogate for a measured flow waveform and provides a reasonable way to assess arterial wave reflection non-invasively in healthy subjects.

Cardiorespiratory interactions: Noncontact assessment using laser Doppler vibrometry

The application of a noncontact physiological recording technique, based on the method of laser Doppler vibrometry (LDV), is described. The effectiveness of the LDV method as a physiological recording modality lies in the ability to detect very small movements of the skin, associated with internal mechanophysiological activities. The method is validated for a range of cardiovascular variables, extracted from the contour of the carotid pulse waveform as a function of phase of the respiration cycle. Data were obtained from 32 young healthy participants, while resting and breathing spontaneously. Individual beats were assigned to four segments, corresponding with inspiration and expiration peaks and transitional periods. Measures relating to cardiac and vascular dynamics are shown to agree with the pattern of effects seen in the substantial body of literature based on human and animal experiments, and with selected signals recorded simultaneously with conventional sensors. These effects include changes in heart rate, systolic time intervals, and stroke volume. There was also some evidence for vascular adjustments over the respiration cycle. The effectiveness of custom algorithmic approaches for extracting the key signal features was confirmed. The advantages of the LDV method are discussed in terms of the metrological properties and utility in psychophysiological research. Although used here within a suite of conventional sensors and electrodes, the LDV method can be used on a stand-alone, noncontact basis, with no requirement for skin preparation, and can be used in harsh environments including the MR scanner.

Associations of Alterations in Pulsatile Arterial Load With Left Ventricular Longitudinal Strain

BACKGROUND

Increased arterial stiffness leads to increased pulsatile load on the heart. We investigated associations of components of pulsatile load with a measure of left ventricular (LV) systolic function-global longitudinal strain (GLS), in a community-based cohort ascertained based on family history of hypertension.

METHODS

Arterial tonometry and echocardiography with speckle tracking were performed in 520 adults with normal LV ejection fraction (EF) (age 67±9 years, 70% hypertensive) to quantify measures of pulsatile load (characteristic aortic impedance (Zc), total arterial compliance (TAC), and augmentation index (AI)) and GLS. The associations of log-Zc, log-TAC, and AI with GLS were assessed using sex-specific z-scores for each measure of arterial load.

RESULTS

In univariable analyses, higher Zc was associated with worse GLS (less negative) and higher TAC and AI were associated with better GLS (all P < 0.001). In a multivariable model including age, sex, heart rate (HR), LVEF, mean arterial load (systemic vascular resistance), and measures of pulsatile load, Zc remained associated with GLS (β = 0.28, P < 0.001), while the associations of TAC and AI were no longer significant (P > 0.5). Additional adjustment for cardiovascular risk factors and history of coronary heart disease and stroke did not attenuate the association of Zc with GLS; Zc, sex, HR, LVEF remained associated with GLS after stepwise elimination (all P < 0.001).

CONCLUSIONS

Greater proximal aortic stiffness, as manifested by a higher Zc, is independently associated with worse LV longitudinal function.

Assessment of Model Based (Input) Impedance, Pulse Wave Velocity, and Wave Reflection in the Asklepios Cohort

Objectives

Arterial stiffness and wave reflection parameters assessed from both invasive and non-invasive pressure and flow readings are used as surrogates for ventricular and vascular load. They have been reported to predict adverse cardiovascular events, but clinical assessment is laborious and may limit widespread use. This study aims to investigate measures of arterial stiffness and central hemodynamics provided by arterial tonometry alone and in combination with aortic root flows derived by echocardiography against surrogates derived by a mathematical pressure and flow model in a healthy middle-aged cohort.

Methods

Measurements of carotid artery tonometry and echocardiography were performed on 2226 ASKLEPIOS study participants and parameters of systemic hemodynamics, arterial stiffness and wave reflection based on pressure and flow were measured. In a second step, the analysis was repeated but echocardiography derived flows were substituted by flows provided by a novel mathematical model. This was followed by a quantitative method comparison.

Results

All investigated parameters showed a significant association between the methods. Overall agreement was acceptable for all parameters (mean differences: -0.0102 (0.033 SD) mmHg*s/ml for characteristic impedance, 0.36 (4.21 SD) mmHg for forward pressure amplitude, 2.26 (3.51 SD) mmHg for backward pressure amplitude and 0.717 (1.25 SD) m/s for pulse wave velocity).

Conclusion

The results indicate that the use of model-based surrogates in a healthy middle aged cohort is feasible and deserves further attention.