Nonlinear Dynamics of Dacron Aortic Prostheses Conveying Pulsatile Flow

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Eleonora Tubaldi ◽  
Michael P. Païdoussis ◽  
Marco Amabili
Keyword(s):  
Physical Activity ◽  
Blood Flow ◽  
Dynamic Response ◽  
Pulsatile Flow ◽  
Orthotropic Shell ◽  
Aortic Surgery ◽  
High Heart Rate ◽  
Lagrange Equations ◽  
Higher Harmonics ◽  
Pulsatile Pressure

This study addresses the dynamic response to pulsatile physiological blood flow and pressure of a woven Dacron graft currently used in thoracic aortic surgery. The model of the prosthesis assumes a cylindrical orthotropic shell described by means of nonlinear Novozhilov shell theory. The blood flow is modeled as Newtonian pulsatile flow, and unsteady viscous effects are included. Coupled fluid–structure Lagrange equations for open systems with wave propagation subject to pulsatile flow are applied. Physiological waveforms of blood pressure and velocity are approximated with the first eight harmonics of the corresponding Fourier series. Time responses of the prosthetic wall radial displacement are considered for two physiological conditions: at rest (60 bpm) and at high heart rate (180 bpm). While the response at 60 bpm reproduces the behavior of the pulsatile pressure, higher harmonics frequency contributions are observed at 180 bpm altering the shape of the time response. Frequency-responses show resonance peaks for heart rates between 130 bpm and 200 bpm due to higher harmonics of the pulsatile flow excitation. These resonant peaks correspond to unwanted high-frequency radial oscillations of the vessel wall that can compromise the long-term functioning of the prosthesis in case of significant physical activity. Thanks to this study, the dynamic response of Dacron prostheses to pulsatile flow can be understood as well as some possible complications in case of significant physical activity.

Nonlinear Response of Shells Conveying Pulsatile Flow With Pulse-Wave Propagation

2016 ◽  
Author(s):  
Eleonora Tubaldi ◽  
Marco Amabili ◽  
Michael P. Paidoussis
Keyword(s):  
Blood Flow ◽  
Wave Propagation ◽  
Pulsatile Flow ◽  
Pulse Wave ◽  
Pulse Wave Propagation ◽  
Vascular Prostheses ◽  
Axial Coordinate ◽  
Pulsatile Pressure ◽  
Velocity Changes ◽  
Oscillatory Pressure

In deformable shells conveying pulsatile flow, oscillatory pressure changes cause local movements of the fluid and shell wall, which propagate downstream in the form of a wave. In biomechanics, it is the propagation of the pulse that determines the pressure gradient during the flow at every location of the arterial tree. In this study, a woven Dacron vascular prosthesis is modelled as a transversely isotropic circular cylindrical shell described by means of nonlinear Novozhilov shell theory. Flexible boundary conditions are considered to simulate connection with the remaining tissue. Nonlinear vibrations of the shell conveying pulsatile flow and subjected to pulsatile pressure are investigated taking into account the effects of the pulse-wave propagation. An input oscillatory pressure at the shell entrance is considered and it propagates down the shell causing a wave motion within the shell where, as a consequence, the pressure gradient and the flow velocity are functions of both the axial coordinate and time. For the first time in literature, coupled fluid-structure Lagrange equations for a non-material volume with wave propagation in case of pulsatile flow are developed. The fluid is modeled as a Newtonian inviscid pulsatile flow and it is formulated using a hybrid model based on the linear potential flow theory and considering the unsteady viscous effects obtained from the unsteady time-averaged Navier-Stokes equations. Contributions of pressure and velocity changes’ propagation are also considered in the pressure drop along the shell and in the pulsatile frictional traction on the internal wall in the axial direction. A numerical bifurcation analysis employs a refined reduced order model to investigate the dynamic behavior of a pressurized Dacron vascular graft conveying blood flow. A pulsatile time-dependent blood flow model is considered in order to study the effect of pressurization by applying the first and second harmonic of the physiological waveforms of velocity and pressure during the heart beating period. Geometrically nonlinear vibration response to pulsatile flow and transmural pulsatile pressure considering the propagation of pressure and velocity changes inside the shell are here presented via frequency-response curves and time histories. It is shown how traveling waves of pressure and velocity cause a delay in the radial displacement of the shell at different values of the axial coordinate. This study provides a deep insight into the currently unknown nonlinear behavior of vascular prostheses whose dynamic response can cause unwanted hemodynamic effects leading to failure. Indeed, it is well known that vascular prostheses mechanical properties are very different from those of natural arteries. In particular, the compliance mismatch between the host artery and the prosthesis causes a different wave speed resulting in a change in the performance of the cardiovascular system. In the near future, a more refined model to the one here presented will be applied to reproduce and compare the dynamic behavior of vascular prostheses and the human aorta, helping in vascular prostheses design and implementation.

Nonlinear Vibrations of Woven Dacron Aortic Prostheses Conveying Pulsatile Flow

2017 ◽  
Author(s):  
Eleonora Tubaldi ◽  
Marco Amabili ◽  
Michael P. Païdoussis
Keyword(s):  
Pulsatile Flow ◽  
Structural Model ◽  
Stokes Equations ◽  
Orthotropic Shell ◽  
Linear Potential ◽  
Viscous Effects ◽  
Lagrange Equations ◽  
Response Curves ◽  
Flowing Fluid ◽  
Modal Damping

Woven Dacron grafts represent standard implants for replacements of the thoracic aorta in current medical practice. Wide knowledge about the distinctly different mechanical properties of the Dacron implants with respect to the native aorta is available in literature while very little is known about the dynamic behavior of these prostheses. This study addresses the dynamic response to pulsatile physiological blood flow and pressure of woven Dacron grafts currently used in thoracic aortic replacements. The structural model assumes a cylindrical orthotropic shell described by means of the nonlinear Novozhilov shell theory. Residual stresses because of pulsatile physiological pressurization are evaluated and included in the model. The pulsatile flowing fluid is formulated using a hybrid model that contains the unsteady effects obtained from linear potential flow theory and the viscous effects obtained from the unsteady time-averaged Navier–Stokes equations. Physiological waveforms of blood pressure and velocity are approximated with the first eight harmonics of the corresponding Fourier series. Coupled fluid-structure Lagrange equations for a non-material volume with wave propagation in case of pulsatile flow are utilized. Frequency-response curves in the physiological range show the geometrically nonlinear vibration response to pulsatile flow with several superharmonic resonance peaks in the high physiological frequency range. Different values of modal damping are considered; in the limit case of low modal damping values, flow-induced asymmetric vibration of the aortic prosthesis is possible. Finally, in order to reproduce the weave design of the woven Dacron fabrics, geometric imperfections are introduced in the structural model. The numerical natural frequencies of the pressurized prosthesis are compared with the experimental results obtained from the modal analysis of a woven Dacron graft.

The Mechanism of Pulse Pressure Affecting the Permeability of Arteries

2008 ◽  
Author(s):  
Qingping Yao ◽  
Danika M. Hayman ◽  
Qiuxia Dai ◽  
Merry L. Lindsey ◽  
Hai-Chao Han
Keyword(s):  
Blood Flow ◽  
Cardiopulmonary Bypass ◽  
Pulse Pressure ◽  
Pulsatile Flow ◽  
Ventricular Assist Devices ◽  
Ventricular Assist ◽  
Age Related ◽  
Pulsatile Pressure ◽  
Mean Pressure

Arteries are subjected to a pulsatile pressure centered on a constant mean pressure in vivo. This oscillating pressure may increase due to atherosclerotic and age-related wall stiffening, or may be disrupted by the use of cardiopulmonary bypass machines and ventricular assist devices. Previous research has reported that restoration of pulsatile flow improves microcirculation and blood flow to the organs, however little is known about how pulsatile pressure affects the vasculature.

Abstract 032: Uninterrupted Sitting Induces Unfavorable Changes In Resting Hemodynamics And Inflammatory And Vascular Biomarkers In Physically Inactive And Active Adults

Circulation ◽  
2021 ◽  
Vol 143 (Suppl_1) ◽  
Author(s):  
Megan C Nelson ◽  
Madeline P Casanova ◽  
Jennavere R Ball ◽  
Rachel D Midence ◽  
Timothy R Johnson ◽  
...  
Keyword(s):  
Physical Activity ◽  
Blood Flow ◽  
Mean Arterial Pressure ◽  
Shear Rate ◽  
Arterial Pressure ◽  
Vascular Function ◽  
Blood Velocity ◽  
Inflammatory Biomarkers ◽  
Active Adults ◽  
Over Time

Introduction: A single bout of uninterrupted sitting impairs vascular function in the legs, which may be due to reductions in blood flow and shear stress. Participating in regular moderate-to-vigorous physical activity (MVPA) has been identified as an effective approach for improving vascular function, and recent evidence suggests meeting the physical activity (PA) guidelines may attenuate some of the negative health outcomes associated with excessive sedentary behavior; however, it is not well understood how meeting the PA guidelines may influence the acute response to sitting. Our aim was to investigate the effects of 3 h of uninterrupted sitting on hemodynamics and vascular and inflammatory biomarkers in physically inactive and active adults. Hypothesis: We hypothesized active adults would experience less detrimental physiological changes after sitting compared to inactive adults. Methods: Eleven inactive (mean±SD, age: 47.1±8.9 y, body fat: 33.1±8.5%; 78.5% women) and 16 active adults (age: 46.1±8.9 y, body fat: 25.2±7.2%; 31.1% women) completed 3 h of uninterrupted sitting. Adults self-reported their PA with the International PA Questionnaire. Adults engaging in ≥150 min·wk -1 were classified as active and <150 min·wk -1 , inactive. Hemodynamic variables, and superficial femoral artery (SFA) diameter and blood velocity were measured each hour over 3 h of sitting. Mean arterial pressure, blood flow and shear rate were calculated. Serum vascular and inflammatory biomarkers were measured pre and post sitting. Linear mixed-effects modeling was used to assess changes in dependent variables over time and between inactive and active adults, controlling for sex. Results: Inactive and active adults self-reported 7.3±7.1 and 93.3±64.8 min·d -1 of MVPA, respectively. Endothelin-1 (baseline: 8.3±13.4 pg/mL, post: 81.1±103.0 pg/mL; p<0.001) and interleukin-6 (baseline: 0.08±0.06 pg/mL, post: 0.11±0.11 pg/mL; p=0.03) increased post sitting compared to baseline in all adults, regardless of PA status. Systolic blood pressure, mean arterial pressure, calf circumference, and SFA diameter, blood velocity, and mean blood flow decreased over time in both groups (p<0.05 for all). There was an interaction effect for mean shear rate (p=0.008); inactive adults experienced a decline over 3 h of sitting (baseline: 76.1±48.2 s -1 ; 1 h: 55.0±27.4 s -1 ; 2 h: 45.3±24.2 s -1 ; 3 h: 40.8±25.5 s -1 ) while active participants demonstrated no change (baseline: 36.6±21.4 s -1 ; 1 h: 28.1±21.4 s -1 ; 2 h: 26.1±20.9 s -1 ; 3 h: 23.8±19.5 s -1 ). Inactive adults also had a higher oscillatory shear index compared to active adults (p<0.001). Conclusion: Uninterrupted sitting induced unfavorable changes regardless of PA status; however, active adults demonstrated a more favorable shear profile. Meeting PA guidelines may attenuate some unfavorable changes within the vasculature associated with prolonged sitting.

scholarly journals Ross procedure and aortic valve repair: long-term echocardiographic outcomes, quality of life and physical activity of different aortic valve surgery procedures

2021 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
F Bianco ◽  
M Colaneri ◽  
V Bucciarelli ◽  
FC Surace ◽  
FC Iezzi ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Physical Activity ◽  
Aortic Valve ◽  
Aortic Surgery ◽  
Ross Procedure ◽  
Valve Repair ◽  
Sf 36

Abstract Funding Acknowledgements Type of funding sources: None. Background  To compare long-term outcomes of aortic valve repair (AVr) and pulmonary autograft replacement (Ross procedure) in terms of echocardiographic parameters, quality of life (QoL), physical activity (PA). Methods  In 2005-19, 129 patients (median age 22 [13, 33 IQR], 75% males) underwent aortic surgery in our Department: 40 were Ross (22 years [19, 51 IQR]), 67 AVr (17 years [1, 50 IQR]) and 22 aortic valve replacements (52 years [30, 80 IQR]). We focused on Ross and AVr. Retrospectively, relevant data were collected from medical records and phone re-calls. Physical activity (spontaneous and active) and QoL were assessed utilizing the IPAQ and SF-36 questionnaires. All patients underwent echocardiography pre/post-surgery and the follow-up lasted 12 ± 4 years. Results  At the baseline, Ross patients had more aortic stenosis than insufficiency (P = 0.045). At the follow-up, Ross procedures presented more right-ventricle and aortic annulus dilatation (P = 0.002 and P = 0.030, respectively), but higher left-ventricular global longitudinal strain (LV GLS: 18 ± 3.2 % vs. 16 ± 3.3, P = 0.0027). Conversely, AVr experienced more re-do operations (Log-rank P = 0.005). Ross reported better QoL (SF-36: 0.8 ± 0.07 vs. 19 ± 0.4, P-0.045) and were also more active in daily PA (IPAQ ≥ 2500 Mets: 63.8% vs. 6%; P = 0.006). Ross patients practiced more sports activities than AVr (P = 0.011). Conclusions  In a relatively small cohort of young and adults post aortic surgery patients, Ross procedures had better prognosis in terms of re-do operations; presented better ventricular function, as assessed by LV GLS. Ross patients had better long-term QoL and showed more spontaneous PA and involvement in sports activity.

Activity-Induced Increase in Achilles Tendon Blood Flow Is Age and Sex Dependent

2018 ◽  
Vol 46 (11) ◽  
pp. 2678-2686 ◽  
Author(s):  
Evi Wezenbeek ◽  
Dirk De Clercq ◽  
Nele Mahieu ◽  
Tine Willems ◽  
Erik Witvrouw
Keyword(s):  
Physical Activity ◽  
Blood Flow ◽  
Achilles Tendon ◽  
Physical Activities ◽  
Male Population ◽  
Flow Measurements ◽  
Increased Risk ◽  
Blood Flow Measurements ◽  
Rope Skipping ◽  
Effect Of Age

Background: Previous research of a young adult population identified a lower increase in Achilles tendon blood flow immediately after a running activity as a significant predictor for the development of Achilles tendinopathy (AT). Furthermore, advancing age is often mentioned as a risk factor for the development of AT, and the highest incidence for AT is reported to occur in middle-aged recreational male athletes. Purpose: To investigate the effect of age, sex, and type of physical activity on the increase in Achilles tendon blood flow. Study Design: Controlled laboratory study. Methods: Blood flow measurements of 33 subjects aged 18 to 25 years and 30 subjects aged 40 to 55 years were obtained before and after 4 physical activities performed in randomized order: running, cycling, dynamic stretching, and rope skipping. Blood flow measurements of the Achilles tendon were performed before, immediately after, 5 minutes after, and 10 minutes after the physical activities. The effect of age, sex, and physical activities on the increase in blood flow was investigated with linear mixed models. Results: The results of this study identified that running, rope skipping, and cycling resulted in a significant increase in tendon blood flow ( P ≤ .001), whereas stretching did not. Prominent was the finding that the increase in blood flow after activity was significantly lower in the older population as compared with the younger population ( P < .001). Furthermore, male participants in the older group showed a significantly lower increase in tendon blood flow than did their female counterparts ( P = .019). Conclusion: This study identified that sex and age significantly influence the increase in blood flow after activity, possibly explaining the increased risk for AT among middle-aged recreational athletes. Clinical Relevance: This study possibly identified one of the mechanisms explaining why an older male population is at increased risk for developing AT. Given that the lower increase in blood flow is an identified risk factor according to previous research, preventative measures should focus on improving this blood flow during physical activity in the physically active older male population. Registration: NCT03218605 ( ClinicalTrials.gov identifier).

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