A cavalpulmonary assist device utilising impedance pumping enhanced by peristaltic effect.

Background: Fontan procedure, the standard surgical palliation to treat children with single ventricular defects, causes systemic complications over years due to lack of pumping at cavopulmonary junction. A device developed specifically for cavopulmonary support is thus considered, while current commercial ventricular assist devices (VAD) induce high shear rates to blood, and have issues with paediatric suitability.

Aim: To demonstrate the feasibility of a small, valveless, non-invasive to blood and pulsatile rotary pump, which integrates impedance and peristaltic effects.

Manufacturing an artificial arterial tree using 3D printing.

Models of the arterial network are useful in studying mechanical cardiac assist devices as well as complex pathological states that are difficult to investigate in-vivo otherwise. Earlier work of artificial arterial tree (AAT) have been constructed to include some of the major arteries and their branches for in-vitro experiments which focused on the aorta, using dipping or painting techniques, which resulted in inaccuracies and inconsistent wall thickness. Therefore, the aim of this work is to use 3D printing for manufacturing AAT based on physiologically correct dimensions of the largest 45 segments of the human arterial tree.

A comparison of different methods to maximise signal extraction when using central venous pressure to optimise atrioventricular delay after cardiac surgery.

Objective: Our group has shown that central venous pressure (CVP) can optimise atrioventricular (AV) delay in temporary pacing (TP) after cardiac surgery. However, the signal-to-noise ratio (SNR) is influenced both by the methods used to mitigate the pressure effects of respiration and the number of heartbeats analysed. This paper systematically studies the effect of different analysis methods on SNR to maximise the accuracy of this technique.

Lower limb hyperthermia augments functional hyperaemia during small muscle mass exercise similarly in trained elderly and young humans.

New Findings: What is the central question of the study? Ageing is postulated to lead to underperfusion of human limb tissues during passive and exertional hyperthermia, but findings to date have been equivocal. Thus, does age have an independent adverse effect on local haemodynamics during passive single-leg hyperthermia, single-leg knee-extensor exercise and their combination? What is the main finding and its importance? Local hyperthermia increased leg blood flow over three-fold and had an additive effect during knee-extensor exercise with no absolute differences in leg perfusion between the healthy, exercise-trained elderly and the young groups. Our findings indicate that age per se does not compromise lower limb hyperaemia during local hyperthermia and/or small muscle mass exercise.

The contribution of upper and lower body arterial vessels to the aortic root reflections: A one-dimensional computational study.

Background And Objectives: Reflections measured at the aortic root are of physiological and clinical interest and thought to be composed of the superimposed reflections arriving from the upper and lower parts of the circulatory system. However, the specific contribution of each region to the overall reflection measurement has not been thoroughly examined. This study aims to elucidate the relative contribution of reflected waves arising from the upper and lower human body vasculature to those observed at the aortic root.

Arterial pulse wave modeling and analysis for vascular-age studies: a review from VascAgeNet.

Arterial pulse waves (PWs) such as blood pressure and photoplethysmogram (PPG) signals contain a wealth of information on the cardiovascular (CV) system that can be exploited to assess vascular age and identify individuals at elevated CV risk. We review the possibilities, limitations, complementarity, and differences of reduced-order, biophysical models of arterial PW propagation, as well as theoretical and empirical methods for analyzing PW signals and extracting clinically relevant information for vascular age assessment. We provide detailed mathematical derivations of these models and theoretical methods, showing how they are related to each other.

Techniques to aid prediction of pacing dependence at 30 days in patients requiring pacemaker implantation after cardiac surgery.

Permanent pacemaker (PPM) implantation occurs in up to 5 % of patients after cardiac surgery but there is little consensus on how long to wait between surgery and PPM insertion. Predicting the likelihood of a patient being pacing dependent 30 days after implant can aid with this timing decision and avoid unnecessary observation time waiting for intrinsic conduction to recover. In this paper, we introduce a new approach for the prediction of PPM dependency at 30 days after implant in patients who have undergone recent cardiac surgery.

Time-course of the human thoracic aorta ageing process assessed using uniaxial mechanical testing and constitutive modelling.

Age-related remodelling of the arterial wall shifts the load bearing from the compliant elastin network to the stiffer collagen fibres. While this phenomenon has been widely investigated in animal models, human studies are lacking due to shortage of donors' arteries. This work aimed to characterise the effect of ageing on the mechanical properties of the human aortic wall in the circumferential direction.

Subject-Specific Pressure Normalization of Local Pulse Wave Velocity: Separating Intrinsic From Acute Load-Dependent Stiffening in Hypertensive Patients.

Pulse wave velocity (PWV) is a powerful predictor of cardiovascular events. However, its intrinsic blood pressure (BP)-dependency complicates distinguishing between acute and chronic effects of increased BP on arterial stiffness. Based on the assumption that arteries exhibit a nearly exponential pressure-area (-) relationship, this study proposes a method to assess intersubject differences in local PWV independently from BP.

Noninvasive carotid pressure-diameter loops to identify viscoelastic properties in ageing, hypertension and type 2 diabetes.

Objectives: Arterial stiffness as pulse wave velocity (PWV) predicts cardiovascular events independently of blood pressure (BP). PWV does not distinguish between stiffness in systole and diastole. This cross-sectional study aimed to test the hypothesis that viscous and elastic carotid wall properties differ between systole and diastole, distinguishing effects of ageing, hypertension and T2 diabetes (T2DM).

Mock circulatory loops used for testing cardiac assist devices: A review of computational and experimental models.

Heart failure is a major health risk, and with limited availability of donor organs, there is an increasing need for developing cardiac assist devices (CADs). Mock circulatory loops (MCL) are an important in-vitro test platform for CAD's performance assessment and optimisation. The MCL is a lumped parameter model constructed out of hydraulic and mechanical components aiming to simulate the native cardiovascular system (CVS) as closely as possible.

Transfer-function-free technique for the noninvasive determination of the human arterial pressure waveform.

The estimation of central aortic blood pressure is a cardinal measurement, carrying effective physiological, and prognostic data beyond routine peripheral blood pressure. Transfer function-based devices effectively estimate aortic systolic and diastolic blood pressure from peripheral pressure waveforms, but the reconstructed pressure waveform seems to preserve features of the peripheral waveform. We sought to develop a new method for converting the local diameter distension waveform into a pressure waveform, through an exponential function whose parameters depend on the local wave speed.

Regional thermal hyperemia in the human leg: Evidence of the importance of thermosensitive mechanisms in the control of the peripheral circulation.

Hyperthermia is thought to increase limb blood flow through the activation of thermosensitive mechanisms within the limb vasculature, but the precise vascular locus in which hyperthermia modulates perfusion remains elusive. We tested the hypothesis that local temperature-sensitive mechanisms alter limb hemodynamics by regulating microvascular blood flow. Temperature and oxygenation profiles and leg hemodynamics of the common (CFA), superficial (SFA) and profunda (PFA) femoral arteries, and popliteal artery (POA) of the experimental and control legs were measured in healthy participants during: (1) 3 h of whole leg heating (WLH) followed by 3 h of recovery (n = 9); (2) 1 h of upper leg heating (ULH) followed by 30 min of cooling and 1 h ULH bout (n = 8); and (3) 1 h of lower leg heating (LLH) (n = 8).

Five years of cardio-ankle vascular index (CAVI) and CAVI0: how close are we to a pressure-independent index of arterial stiffness?

Pulse wave velocity, a common metric of arterial stiffness, is an established predictor for cardiovascular events and mortality. However, its intrinsic pressure-dependency complicates the discrimination of acute and chronic impacts of increased blood pressure on arterial stiffness. Cardio-ankle vascular index (CAVI) represented a significant step towards the development of a pressure-independent arterial stiffness metric.

From Uniaxial Testing of Isolated Layers to a Tri-Layered Arterial Wall: A Novel Constitutive Modelling Framework.

Mechanical testing and constitutive modelling of isolated arterial layers yields insight into the individual layers' mechanical properties, but per se fails to recapitulate the in vivo loading state, neglecting layer-specific residual stresses. The aim of this study was to develop a testing/modelling framework that integrates layer-specific uniaxial testing data into a three-layered model of the arterial wall, thereby enabling study of layer-specific mechanics under realistic (patho)physiological conditions. Circumferentially and axially oriented strips of pig thoracic aortas (n = 10) were tested uniaxially.

Study Protocol: The Heart and Brain Study.

Background: It is well-established that what is good for the heart is good for the brain. Vascular factors such as hypertension, diabetes, and high cholesterol, and genetic factors such as the apolipoprotein E4 allele increase the risk of developing both cardiovascular disease and dementia. However, the mechanisms underlying the heart-brain association remain unclear.

Towards the non-invasive determination of arterial wall distensible properties: New approach using old formulae.

Arterial function and wall mechanical properties are important determinants of hemodynamics in the circulation. However, their non-invasive determination is not widely available. Therefore, the aim of this work is to present a novel approach for the non-invasive determination of vessel's distensibility and elastic modulus.

Mechanisms of Aortic Flow Deceleration and the Effect of Wave Reflection on Left Ventricular Function.

Increased wave reflection is an independent predictor of cardiovascular events, possibly due to effects on left ventricular (LV) function. We investigated the relationship between reflected waves in early systole, the forward decompression wave in mid-late systole and LV mechanical behavior. Invasively acquired ascending aortic velocity, pressure, and LV long and minor axes' dimensions were measured simultaneously in 11 anesthetized dogs during both control conditions and aortic occlusion to cause additional early wave reflection.

Experimental Devices Versus Hand-Sewn Anastomosis of the Aorta: A Systematic Review and Meta-Analysis.

Background: To minimize complications associated with the construction of the hand-sewn aortic anastomosis, alternative experimental methods have been pursued. This study aimed to evaluate the efficacy of experimental anastomotic devices in relation to time and point of rupture of the anastomosis in comparison to the conventional technique.

Materials And Methods: An electronic search was performed using MEDLINE, Scopus, Science Direct, and Cochrane Library databases by two independent authors.

Impact of varying diastolic pressure fitting technique for the reservoir-wave model on wave intensity analysis.

The reservoir-wave model assumes that the measured arterial pressure is made of two components: reservoir and excess. The effect of the reservoir volume should be excluded to quantify the effects of forward and backward traveling waves on blood pressure. Whilst the validity of the reservoir-wave concept is still debated, there is no consensus on the best fitting method for the calculation of the reservoir pressure waveform.

Review of the Techniques Used for Investigating the Role Elastin and Collagen Play in Arterial Wall Mechanics.

The arterial wall is characterised by a complex microstructure that impacts the mechanical properties of the vascular tissue. The main components consist of collagen and elastin fibres, proteoglycans, Vascular Smooth Muscle Cells (VSMCs) and ground matrix. While VSMCs play a key role in the active mechanical response of arteries, collagen and elastin determine the passive mechanics.

Weight Loss After Bariatric Surgery Significantly Improves Carotid and Cardiac Function in Apparently Healthy People with Morbid Obesity.

Purpose: Obesity clearly increases cardiovascular risk, often inducing high blood pressure (BP), impaired left ventricular (LV) function, and increased arterial stiffness. Intensive weight loss and bariatric surgery induce improvement in hypertension and diabetes for morbid obesity. Carotid artery haemodynamics is a powerful prognostic indicator for stroke and cognitive decline independent of BP.