Nikolaos Stergiopoulos

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The mismatch of elastic properties between the arterial tissue and the vascular grafts, commonly called compliance mismatch, is responsible for many deleterious post-operative complications. Currently, there is an absence of prostheses that conform with th ...

The study aim was to quantify the individual and combined contributions of both the arterial system and the heart to systolic blood pressure in hypertension. We assessed the parameters of a heart-arterial model for normotensive control subjects and hypertensive patients with left ventricular adaptation patterns classified as normal, concentric remodeling, concentric hypertrophy, or eccentric hypertrophy. The present simulations show that vascular stiffening alone increases the pulse pressure without increas

Cardiac and aortic characteristics are crucial for cardiovascular disease detection. However, noninvasive estimation of aortic hemodynamics and cardiac contractility is still challenging. This paper investigated the potential of estimating aortic systolic ...

We estimated total arterial compliance (C) in eight anesthetized mongrel dogs with (i) the area method (AM), (ii) the pulse pressure method (PPM), and (iii) the stroke volume-to-pulse pressure ratio (SV/PP). Average compliance was C(AM)=1.1+/-0.73 ml mm Hg(-1) using AM; C(PPM)=0.60+/-0.31 ml mm Hg(-1) using PPM and C(SV/PP)=0.87+/-0.49 ml mm Hg(-1) using SV/PP. Mean aortic pressure was 64+/-23 mm Hg. The overall agreement between C(AM) and C(PPM) was relatively poor (C(AM)=0.15+/-1.61 C(PPM); r2=0.48), with

In a progressively aging population, it is of utmost importance to develop reliable, noninvasive, and cost-effective tools to estimate biomarkers that can be indicative of cardiovascular risk. Various pathophysiological conditions are associated to changes ...

We have examined the diameter response of rat femoral artery segments in the presence and absence of endothelium to changes in flow rate. The segments were isolated, mounted on microcannulae, maintained at 37 degrees C, and perfused at 90 mmHg with Tyrode's solution. The external arterial diameter was measured using video-microscopy. The mean control diameter was 741+/-22 microm (mean+/-SEM,n=7). The arteries were preconstricted to 75+/-1% of the control diameter with a superfusion of 1 microM norepinephrin

Objective Several ultrasound-based methods are currently used to assess aortic diameter, circumferential strain and stiffness in mice, but none of them is flawless and a gold standard is lacking. We aimed to assess the validity and sensitivity of these met ...

Background: Pulmonary hypertension is characterized by extensive remodelling of the pulmonary tree, with enlargement of the pulmonary arteries. The predictive value of pulmonary hypertension in patients undergoing transcatheter aortic valve replacement (TAVR) has been demonstrated. We aimed to evaluate the prognostic impact of the pre-procedural main pulmonary artery (mPA) enlargement, assessed by computed tomography angiography, in patients undergoing TAVR for severe aortic stenosis (AS). Methods: We retro

In this paper we examine the importance of fluid friction and nonlinearities due to the area-pressure relationship and to the convective acceleration on the separation of arterial pressure and flow waves into their forward and backward components. Experiments were run in straight uniform nonlinearly elastic tubes. Different degrees of fluid friction and nonlinearities, covering the physiological range, have been tested. We predicted the forward and backward running pressure components using two wave separat

Angiotensin (Ang)-(1-7), acting through the receptor Mas, has athero-protective effects; however, its role on plaque vulnerability has been poorly studied. Here, we investigated the expression of the renin-angiotensin system (RAS) components in stable and ...

Abdominal aortic aneurysm (AAA) is a local expansion of the abdominal aorta wall caused by a complex multifactorial maladaptive vascular remodeling. Despite recent advances in the management of cardiovascular diseases, there currently is no established dru ...

Global assessment of both cardiac and arterial function is important for a meaningful interpretation of pathophysiological changes in animal models of cardiovascular disease. We simultaneously acquired left ventricular (LV) and aortic pressure and LV volume (V(LV)) in 17 open-chest anesthetized mice (26.7 +/- 3.2g) during steady-state (BL) and caval vein occlusion (VCO) using a 1.4-Fr dual-pressure conductance catheter and in a subgroup of eight animals during aortic occlusion (AOO). Aortic flow was obtaine

Platelets play a crucial role in arterial thrombus formation, offering potential for new antiplatelet therapies with reduced bleeding risk. Here, we investigated the role of the renin-angiotensin system (RAS) in human platelets and explored its potential l ...

Background: Although compelling evidence has established the physiological and clinical relevance of aortic SBP (a-SBP), no consensus exists regarding the validity of the available methods/techniques that noninvasively measure it. Objectives: The systemati ...

Minimally invasive medical procedures, such as endovascular catheterization, have considerably reduced procedure time and associated complications. However, many regions inside the body, such as in the brain vasculature, still remain inaccessible due to th ...

Tracheomalacia (TM) is a condition characterized by a weak tracheal cartilage and/or muscle, resulting in excessive collapse of the airway in the newborns. Current treatments including tracheal reconstruction, tracheoplasty, endo- and extra-luminal stents ...

Vasomotion, the phenomenon of vessel diameter oscillation, regulates blood flow and resistance. The main parameters implicated in vasomotion are particularly the membrane potential and the cytosolic free calcium in smooth muscle cells. In this study, these parameters were measured in rat perfused-pressurized mesenteric artery segments. The application of norepinephrine (NE) caused rhythmic diameter contractions and membrane potential oscillations (amplitude; 5.3 +/- 0.3 mV, frequency; 0.09 +/- 0.01 Hz). Ver

A computer model for simulating pressure and flow propagation in the human arterial system is developed. The model is based on the one-dimensional flow equations and includes nonlinearities arising from geometry and material properties. Fifty-five arterial segments, representing the various major arteries, are combined to form the model of the arterial system. Particular attention is paid to the development of peripheral pressure and flow pulses under normal flow conditions and under conditions of arterial

Percutaneous embolization and surgical repair are the current treatment options for varicocele, but determining method superiority remains controversial. In this retrospective study, we evaluate the technical success, complication and recurrence rates foll ...

A computer model for simulating pressure and flow propagation in the human arterial system is developed. The model is based on the one-dimensional flow equations and includes non-linearities arising from geometry and material properties. Fifty five arterial segments, representing the various major arteries, are combined to form the model of the arterial system. Particular attention is paid to the development of peripheral pressure and flow pulses under normal flow conditions and under conditions of arterial

Nikolaos Stergiopoulos

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Evaluation of a novel compliance-matching aortic graft in a swine model

Quantification of the contribution of cardiac and arterial remodeling to hypertension

Noninvasive estimation of aortic hemodynamics and cardiac contractility using machine learning

Pulse pressure method and the area method for the estimation of total arterial compliance in dogs: sensitivity to wave reflection intensity

On the assessment of arterial compliance from carotid pressure waveform

In vitro diameter response of rat femoral artery to flow in the presence and absence of endothelium

Performance Comparison of Ultrasound-Based Methods to Assess Aortic Diameter and Stiffness in Normal and Aneurysmal Mice

Prognostic Impact of Main Pulmonary Artery Enlargement in Patients Undergoing Transcatheter Aortic Valve Replacement

Effects of friction and nonlinearities on the separation of arterial waves into their forward and backward components

Treatment with Angiotensin-(1-7) reduces inflammation in carotid atherosclerotic plaques

Emerging Pharmacological Treatments to Prevent Abdominal Aortic Aneurysm Growth and Rupture

Conductance catheter-based assessment of arterial input impedance, arterial function, and ventricular-vascular interaction in mice

The renin-angiotensin system in healthy human platelets: expressed but inactive

Accuracy of commercial devices and methods for noninvasive estimation of aortic systolic blood pressure a systematic review and meta-analysis of invasive validation studies

Flow driven robotic navigation of microengineered endovascular probes

Wet adhesive hydrogels to correct malacic trachea (tracheomalacia) A proof of concept

Role of membrane potential in vasomotion of isolated pressurized rat arteries

Computer simulation of arterial flow with applications to arterial and aortic stenoses

Varicocele percutaneous embolization outcomes in a pediatric group: 7-year retrospective study

Numerical study of pressure and flow propagation in arteries