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Extracranial carotid artery aneurysms (ECCA) lead to rupture and neurologic symptoms from embolisation, with potentially fatal outcomes. Investigating the biomechanical behaviour of EECA with blood flow dynamics is crucial for identifying regions more susceptible to rupture. A coupled three-dimensional (3D) Windkessel-framework and hyperelastic fluid-structure interaction (FSI) analysis of ECCAs with patient-specific geometries, was developed in this paper with a particular focus on hemodynamic parameters and the arterial wall's biomechanical response. The blood flow has been modelled as non-Newtonian, pulsatile, and turbulent. The biomechanical characteristics of the aneurysm and artery are characterised employing a 5-parameter Mooney-Rivlin hyperelasticity model. The Windkessel effect is also considered to efficiently simulate pressure profile of the outlets and to capture the dynamic changes over the cardiac cycle. The study found the aneurysm carotid artery exhibited the high levels of pressure, wall shear stress (WSS), oscillatory shear index (OSI), and relative residence time (RRT) compared to the healthy one. The deformation of the arterial wall and the corresponding von Mises (VM) stress were found significantly increased in aneurysm cases, in comparison to that of no aneurysm cases, which strongly correlated with the hemodynamic characteristics of the blood flow and the geometric features of the aneurysms. This escalation would intensify the risk of aneurysm wall rupture. These findings have critical implications for enhancing treatment strategies for patients with extracranial aneurysms. [ABSTRACT FROM AUTHOR]

Background: Aortic elasticity creates a cushion that protects the heart from pressure injury, and a recoil that helps perfuse the coronary arteries. TEVAR has become first-line therapy for many aortic pathologies including trauma, but stent-grafts stiffen the aorta and likely increase LV afterload. Objective: Test the hypothesis that trauma TEVAR is associated with LV mass increase and adverse off-target aortic remodeling. Methods: Computed Tomography Angiography (CTA) scans of 20 trauma TEVAR patients (17 M/3 F) at baseline [age 34.9 ± 18.5 (11.4–71.5) years] and 5.1 ± 3.1 (1.1–12.3) years after repair were used to measure changes in LV mass, LV mass index, and diameters and lengths of the ascending thoracic aorta (ATA). Measurements were compared with similarly-aged control patients without aortic repair (21 M/21 F) evaluated at similar follow-ups. Results: LV mass and LV mass index of TEVAR patients increased from 138.5 ± 39.6 g and 72.35 ± 15.17 g/m2 to 173.5 ± 50.1 g and 85.48 ± 18.34 g/m2 at the rate of 10.03 ± 12.79 g/yr and 6.25 ± 10.28 g/m2/yr, whereas in control patients LV characteristics did not change. ATA diameters of TEVAR patients increased at a rate of 0.60 ± 0.80 mm/yr, which was 2.4-fold faster than in controls. ATA length in both TEVAR and control patients increased at 0.58 mm/yr. Half of TEVAR patients had hypertension at follow-up compared to only 5% at baseline. Conclusions: TEVAR is associated with LV mass increase, development of hypertension, and accelerated expansile remodeling of the ascending aorta. Although younger trauma patients may adapt to these effects, these changes may be even more important in older patients with other aortic pathologies and diminished baseline cardiac function. [ABSTRACT FROM AUTHOR]

Arterial blood pressure monitoring is a major part of the decision-making process for every anesthetic. It is important to recognize the advantages, disadvantages, and limitations of available measurement modalities as well as have some understanding of the engineering principles on which these measurements are based. Oscillometry is by far the most common modality used but is limited by its intermittent nature and inaccuracy during hypotension and hypertension. Arterial catheterization is the gold standard for measuring blood pressure but is an invasive procedure that is expensive and not without risk of harm to the patient. Volume clamp and tonometric technologies are relatively new and allow for continuous noninvasive monitoring of the blood arterial waveform, but their accuracy when compared with oscillometry is not well described, and they have not been widely incorporated into standard practice. Additional research is needed to determine whether continuous noninvasive blood pressure monitors can improve outcomes. [ABSTRACT FROM AUTHOR]

Models of haemodynamics play a central role in current research directed to understanding and addressing cardiovascular disease. Although conventional windkessel and wave models are very useful, they are incompatible due to conflicting assumptions and neither comprehensively explain the basis and interdependencies of pressure/flow waves, mean pressure and reservoir filling/discharge phenomena. The hybrid reservoir-wave model was proposed to address this gap, but is not widely accepted due to theoretical inconsistencies and negative results from validation studies. We recently described a unified model of haemodynamics based on the concept of ‘wave potential’, which identifies physically meaningful information from the absolute values of the forward/backward components of pressure and flow. Within this paradigm, hydraulic power may also be separated into forward/backward components, thus allowing study of time-dependent cardiac and vascular effects that influence hydraulic power output and efficiency. Based on in vivo and numerical experiments, it has been shown that 1) absolute values of the pressure/flow/power components represent wave potential, spatial gradients of which produce waves that transfer hydraulic energy, 2) mean pressure is generated by waves, 3) wave potential is a measure of local conduit arterial reservoir function and stored hydraulic energy, and 4) the diastolic pressure decay and associated ‘self-cancelling’ diastolic waves can be explained purely on the basis of wave reflection and distal leakage of wave potential. Wave potential provides a unified and analytically simple paradigm of arterial haemodynamics that extends and is fully compatible with conventional wave separation, while overcoming the difficulties encountered with the reservoir-wave paradigm. [ABSTRACT FROM AUTHOR]

This paper aims to summarize and map contemporary views on some contentious aspects of arterial hemodynamics that have remained unresolved despite years of research. These were discussed during a workshop entitled Arterial hemodynamics: past, present and future held in London on June 14 and 15, 2016. To do this we formulated a list of potential consensus statements informed by discussion at the meeting in London and quantified the degree of agreement and invited comments from the participants of the workshop. Overall the responses and comments show a high measure of quantitative agreement with the various proposed ‘consensus’ statements. Taken together, these statements seem a useful basis for proceeding with a more detailed and comprehensive consensus document on the current understanding and approaches to analysis of the pulse waveform. Future efforts should be directed at identifying remaining areas of dispute and future topics for research. [ABSTRACT FROM AUTHOR]

Abstract: Optimization of fluid status, perfusion pressure and cardiac output in intraoperative and critical care settings improves clinical outcomes. Cardiac output is a measure of the blood pumped around the circulation. Modelling of the circulation facilitates estimation of cardiac output from readily measured variables. Methods include thermodilution, analysis of arterial pressure waveforms, Doppler measurements of blood flow velocity, electrical bioimpedance and regional oxygenation. Physical limitations of each measurement technique produce predictable as well as unquantifiable errors, leading to over- or underestimates of cardiac output. [Copyright &y& Elsevier]

Summary It has been recognised for nearly 200 years that the human pressure waveform changes in shape with ageing and disease. The shape of the pressure waveform has been explained in terms of two fundamental models: the Windkessel (reservoir) and wave theory. In its simplest form the Windkessel model satisfactorily explains the pressure waveform in diastole but cannot model pressure changes in systole. Wave theory satisfactorily models the pressure waveform but predicts the existence of ‘self-cancelling’ forward and backward waves in diastole which are difficult to explain in biological terms. We propose that a hybrid reservoir–wave model better describes the pressure waveform and may enable assessment of aortic function from pressure measurements made at any large systemic artery. [ABSTRACT FROM AUTHOR]