A Mock Circulation Loop for In Vitro Hemodynamic Evaluation of Aorta: Application in Aortic Dissection

2021 ◽  
pp. 152660282110348
Author(s):  
Duanduan Chen ◽  
Shichao Liang ◽  
Zhenfeng Li ◽  
Yuqian Mei ◽  
Huiwu Dong ◽  
...  
Keyword(s):  
Aortic Dissection ◽  
False Lumen ◽  
Peripheral Resistance ◽  
Flow Distribution ◽  
Circulation Loop ◽  
Patient Specific ◽  
Mock Circulation ◽  
Blood Transport ◽  
Mock Circulation Loop

Purpose Aortic dissection (AD) is a catastrophic disease with complex hemodynamic conditions, however, understandings regarding its perfusion characteristics were not sufficient. In this study, a mock circulation loop (MCL) that integrated the Windkessel element and patient-specific silicone aortic phantoms was proposed to reproduce the aortic flow environment in vitro. Materials and Methods Patient-specific normal and dissected aortic phantoms with 12 branching vessels were established and embedded into this MCL. Velocities for aortic branches based on 20 healthy volunteers were regarded as the standardized data for flow division. By altering boundary conditions, the proposed MCL could mimic normal resting and left-sided heart failure (LHF) conditions. Flow rates and pressure status of the aortic branches could be quantified by separate sensors. Results In normal resting condition, the simulated heart rate and systemic flow rate were 60 bpm and 4.85 L/minute, respectively. For the LHF condition, the systolic and diastolic blood pressures were 75.94±0.77 mmHg and 57.65±0.35 mmHg, respectively. By tuning the vascular compliance and peripheral resistance, the flow distribution ratio (FDR) of each aortic branch was validated by the standardized data in the normal aortic phantom (mean difference 2.4%±1.70%). By comparing between the normal and dissected aortic models under resting condition, our results indicated that the AD model presented higher systolic (117.82±0.60 vs 108.75±2.26 mmHg) and diastolic (72.38±0.58 vs 70.46±2.33 mmHg) pressures, the time-average velocity in the true lumen (TL; 36.95 cm/s) was higher than that in the false lumen (FL; 22.95 cm/s), and the blood transport direction between the TL and FL varied in different re-entries. Conclusions The proposed MCL could be applied as a research tool for in vitro hemodynamic analysis of the aorta diseases under various physical conditions.

An advanced mock circulation loop for in vitro cardiovascular device evaluation

2020 ◽  
Vol 44 (6) ◽  
Author(s):  
Shaun D. Gregory ◽  
Jo P. Pauls ◽  
Eric L. Wu ◽  
Andrew Stephens ◽  
Ulrich Steinseifer ◽  
...  
Keyword(s):  
Circulation Loop ◽  
Mock Circulation ◽  
Mock Circulation Loop

A Compact Mock Circulation Loop for the In Vitro Testing of Cardiovascular Devices

2010 ◽  
Vol 35 (4) ◽  
pp. 384-391 ◽  
Author(s):  
Daniel L. Timms ◽  
Shaun D. Gregory ◽  
Nicholas A. Greatrex ◽  
Mark J. Pearcy ◽  
John F. Fraser ◽  
...  
Keyword(s):  
Circulation Loop ◽  
In Vitro Testing ◽  
Cardiovascular Devices ◽  
Mock Circulation ◽  
Mock Circulation Loop

Abstract 102: Number of Reentry Tears Influences Flap Motion and Flow Reversal in an in vitro Model of Type B Aortic Dissection

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Joav Birjiniuk ◽  
Mark Young ◽  
Lucas H Timmins ◽  
Bradley G Leshnower ◽  
John N Oshinski ◽  
...  
Keyword(s):  
Aortic Dissection ◽  
False Lumen ◽  
Flow Reversal ◽  
Patient Specific ◽  
Type B ◽  
True Lumen ◽  
Flow Rates ◽  
Custom Made ◽  
Type B Dissection

Objectives: Aortic remodeling after dissection is poorly understood. Thus, optimal patient-specific recommendations for treatment are lacking. An in vitro aortic model of Type B dissection was used to interrogate local aortic hemodynamic parameters implicated in thrombosis and aneurysm formation. We hypothesize that dissections with multiple reentry tears will exhibit decreased flap motion, and, as a result, reduce flow reversal. Methods: Anatomic models of aortic dissection with fidelity to patient CT images were fabricated out of silicone. Models with primary entry and single fenestration (Figure 1A), two fenestrations (Figure 1B), and three fenestrations (Figure 1C) were installed in a flow loop. Physiologic flow was established at a cardiac index of 4 L/min. Flow velocities were acquired using phase contrast magnetic resonance (PCMR) imaging. Flow rates and flap motion were quantified using custom made software. Results: Relative true lumen area (RTLA) varied along the dissection (entry: 55% +/- 3, middle: 34% +/-7, exit: 91%+/-3, p<0.00001 pair-wise for 2-tear model). At mid-dissection, RTLA was lower in dissections with fewer tears (p<0.01). Total flow was nearly identical in all cases, while true and false lumen flow rates differed significantly across tear configurations and along the dissection (p<0.01). Secondary tears allowed for flow communication within the dissected portion of the aortic model. Flow reversal was seen in the false lumen at the mid-dissection plane in the absence of secondary tears (Figure 1D). However, as secondary tears were added, the flow reversal in the false lumen decreased, with concomitant flow reversal in the true lumen (Figure 1E,F). Conclusions: Anatomic characteristics of dissection, such as number of tears, affect blood flow and motion of the dissection flap, as shown quantitatively. This compliant aorta model illustrates alterations in flow reversal in both true and false lumina that may lead to aneurysmal degeneration.

scholarly journals Contrast Microsphere Destruction by a Continuous Flow Ventricular Assist Device: An In Vitro Evaluation Using a Mock Circulation Loop

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
David G. Platts ◽  
Nicole Bartnikowski ◽  
Shaun D. Gregory ◽  
Gregory M. Scalia ◽  
John F. Fraser
Keyword(s):  
Signal Intensity ◽  
Continuous Flow ◽  
Ventricular Assist Devices ◽  
Circulation Loop ◽  
Relative Reduction ◽  
Ventricular Assist ◽  
Pump Speed ◽  
Mock Circulation ◽  
Mock Circulation Loop

Objectives. Transthoracic echocardiography (TTE) is fundamental in managing patients supported with ventricular assist devices (VAD). However imaging can be difficult in these patients. Contrast improves image quality but they are hydrodynamically fragile agents. The aim was to assess contrast concentration following passage through a VAD utilising a mock circulation loop (MCL). Methods. Heartware continuous flow (CF) VAD was incorporated into a MCL. Definity® contrast was infused into the MCL with imaging before and after CF-VAD. 5 mm2 regions of interest were used to obtain signal intensity (decibels), as a surrogate of contrast concentration. Results. Four pump speeds revealed significant reduction in contrast signal intensity after CF-VAD compared to before CF-VAD (all p<0.0001). Combined pre- and postpump data at all speeds showed a 22.2% absolute reduction in contrast signal intensity across the CF-VAD (14.8 ± 0.8 dB prepump versus 11.6 ± 1.4 dB postpump; p<0.0001). Mean signal intensity reduction at each speed showed an inverse relationship between speed and relative reduction in signal intensity. Conclusion. Contrast microsphere transit through a CF-VAD within a MCL resulted in significant reduction in signal intensity, consistent with destruction within the pump. This was evident at all CF-VAD pump speeds but relative signal drop was inversely proportional to pump speed.

scholarly journals The effect of beta-blockers on hemodynamic parameters in patient-specific blood flow simulations of type-B aortic dissection: a virtual study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad Amin Abazari ◽  
Deniz Rafieianzab ◽  
M. Soltani ◽  
Mona Alimohammadi
Keyword(s):  
Aortic Dissection ◽  
Clinical Decision Making ◽  
Beta Blockers ◽  
False Lumen ◽  
Specific Treatment ◽  
Left Ventricular ◽  
Patient Specific ◽  
Type B ◽  
Windkessel Model ◽  
Computed Tomography Images

AbstractAortic dissection (AD) is one of the fatal and complex conditions. Since there is a lack of a specific treatment guideline for type-B AD, a better understanding of patient-specific hemodynamics and therapy outcomes can potentially control the progression of the disease and aid in the clinical decision-making process. In this work, a patient-specific geometry of type-B AD is reconstructed from computed tomography images, and a numerical simulation using personalised computational fluid dynamics (CFD) with three-element Windkessel model boundary condition at each outlet is implemented. According to the physiological response of beta-blockers to the reduction of left ventricular contractions, three case studies with different heart rates are created. Several hemodynamic features, including time-averaged wall shear stress (TAWSS), highly oscillatory, low magnitude shear (HOLMES), and flow pattern are investigated and compared between each case. Results show that decreasing TAWSS, which is caused by the reduction of the velocity gradient, prevents vessel wall at entry tear from rupture. Additionally, with the increase in HOLMES value at distal false lumen, calcification and plaque formation in the moderate and regular-heart rate cases are successfully controlled. This work demonstrates how CFD methods with non-invasive hemodynamic metrics can be developed to predict the hemodynamic changes before medication or other invasive operations. These consequences can be a powerful framework for clinicians and surgical communities to improve their diagnostic and pre-procedural planning.

PIV and LIF Measurements in Aortic Dissection Models

2017 ◽  
Author(s):  
Elie Salameh ◽  
Wadih Khoury ◽  
Charbel Saade ◽  
Ghanem F. Oweis
Keyword(s):  
Aortic Dissection ◽  
Flow Behavior ◽  
False Lumen ◽  
Blood Stream ◽  
Flow Patterns ◽  
Vascular Abnormalities ◽  
Transport Dynamics ◽  
Mixing Behavior ◽  
Contrast Ct

In this work an in-vitro flow experiment is conducted to elucidate the flow behavior in simplified aortic dissection (AD) disease geometries. In AD, the innermost layer of the aortic wall is locally and partially torn allowing blood to flow between the wall layers forming a parallel blood stream in what is known as the false lumen. The aim of this work is to elucidate the disease flow physics, and to provide guidance in diagnostic radiology, particularly contrast injected computed tomography (CT), where understanding flow patterns and mixing behavior is important for accurate diagnosis. In contrast-CT, dye is injected in the peripheral blood stream to illuminate the blood vessels and identify vascular abnormalities. The flow patterns and the dye transport dynamics impact the nature of the CT images and their interpretation. Particle image velocimetry (PIV) is used to quantify the AD flow fields, and laser-induced fluorescence (LIF) is implemented to visualize and assess the mixing behavior of dye in the false and true lumens. Interesting flow patterns are revealed and discussed in the context of their possible contribution to tear expansion and flapping, and to the elevated mean pressure in the false lumen that is reported in the literature.

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