scholarly journals A Framework for Evaluating Myocardial Stiffness Using 3D-Printed Hearts

2021 ◽  
Author(s):  
Fikunwa Kolawole ◽  
Mathias Peirlinck ◽  
Tyler E. Cork ◽  
Vicky Y. Wang ◽  
Seraina A. Dual ◽  
...  
Keyword(s):  
Constitutive Modeling ◽  
Ground Truth ◽  
Diastolic Filling ◽  
Uniaxial Tensile ◽  
Myocardial Stiffness ◽  
Uniaxial Tensile Testing ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
3D Printed

AbstractMRI-driven computational modeling is increasingly used to simulate in vivo cardiac mechanical behavior and estimate subject-specific myocardial stiffness. However, in vivo validation of these estimates is exceedingly difficult due to the lack of a known ground-truth in vivo myocardial stiffness. We have developed 3D-printed heart phantoms of known myocardium-mimicking stiffness and MRI relaxation properties and incorporated the heart phantoms within a highly controlled MRI-compatible setup to simulate in vivo diastolic filling. The setup enables the acquisition of experimental data needed to evaluate myocardial stiffness using computational constitutive modeling: phantom geometry, loading pressures, boundary conditions, and filling strains. The pressure-volume relationship obtained from the phantom setup was used to calibrate an in silico model of the heart phantom undergoing simulated diastolic filling. The model estimated stiffness was compared with ground-truth stiffness obtained from uniaxial tensile testing. Ultimately, the setup is designed to enable extensive validation of MRI and FEM-based myocardial stiffness estimation frameworks.

Continuity and Affine Fiber Kinematics in Biaxial Tension of the Supraspinatus Tendon

2011 ◽  
Author(s):  
Spencer E. Szczesny ◽  
John Peloquin ◽  
Sarah Ilkhani-Pour ◽  
Daniel H. Cortes ◽  
Jennifer A. Kadlowec ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Material Properties ◽  
Biaxial Tension ◽  
Supraspinatus Tendon ◽  
Recent Analysis ◽  
Uniaxial Tensile ◽  
Angle Distribution ◽  
Fiber Angle ◽  
Uniaxial Tensile Testing

The human supraspinatus tendon (SST) exhibits strong heterogeneity in fiber alignment and material properties [1,2]. The relationship between fiber angle distribution and material properties has been previously described by a structurally based continuum model [3], which provided new quantitative structure-function relationships to explain the observed SST heterogeneity; however, in some locations and testing directions, the model predictions were not consistent with a continuum assumption [3]. More recent analysis of the change in fiber angle during loading showed that samples with less aligned fibers have less affine kinematics in uniaxial tensile loading [4]. That is, in uniaxial tensile testing, where the transverse edges freely contract, the fiber strain did not match the tissue strain. Because the SST is somewhat transversely constrained by surrounding rotator cuff structures in vivo and has distributed fibers to support multidirectional loading, the freely contracting edges of uniaxial tension may not appropriately constrain the tendon. Therefore, the objective of this study was to evaluate SST stress-strain behavior and affine deformation under biaxial tension. Specifically, if behaving as a continuum, we expected that applying a fixed boundary condition in the transverse direction would produce a higher apparent modulus, a smaller toe-region, and more affine fiber realignment than a free boundary condition.

scholarly journals Cross-linking Electrospun Polydioxanone-Soluble Elastin Blends: Material Characterization

2008 ◽  
Vol 3 (1) ◽  
pp. 155892500800300 ◽  
Author(s):  
Michael J. McClure ◽  
Scott A. Sell ◽  
Catherine P. Barnes ◽  
Whitney C. Bowen ◽  
Gary L. Bowlin
Keyword(s):  
Femoral Artery ◽  
Material Properties ◽  
In Vivo Studies ◽  
Uniaxial Tensile ◽  
Cross Linking ◽  
Materials Testing ◽  
Uniaxial Tensile Testing ◽  
The Cross

The purpose of this study was to establish whether material properties of elastin co-electrospun with polydioxanone (PDO) would change over time in both the uncross-linked state and the cross-linked state. First, uncross-linked scaffolds were placed in phosphate buffered saline (PBS) for three separate time periods: 15 minutes, 1 hour, and 24 hours, and subsequently tested using uniaxial materials testing. Several cross-linking reagents were then investigated to verify their ability to crosslink elastin: 1–ethyl-3–(dimethylaminopropyl)-carbodiimide (EDC), ethylene glycol diglycidyl ether (EGDE), and genipin. Uniaxial tensile testing was performed on scaffolds cross-linked with EDC and genipin, yielding results that warranted further investigation for PDO-elastin blends. Material properties of the cross-linked scaffolds were then found within range of both pig femoral artery and human femoral artery. These results demonstrate PDO-elastin blends could potentially be favorable as vascular grafts, thus warranting future in vitro and in vivo studies.

Pressure-volume-based single-beat estimations cannot predict left ventricular contractility in vivo

2002 ◽  
Vol 282 (5) ◽  
pp. H1739-H1750 ◽  
Author(s):  
Knut E. Kjørstad ◽  
Christian Korvald ◽  
Truls Myrmel
Keyword(s):  
Systolic Pressure ◽  
Left Ventricular ◽  
Clinical Applications ◽  
Volume Data ◽  
Ventricular Contractility ◽  
Limits Of Agreement ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
State Pressure

The end-systolic pressure-volume relationship is regarded as a useful index for assessing the contractile state of the heart. However, the need for preload alterations has been a serious limitation to its clinical applications, and there have been numerous attempts to develop a method for calculating contractility based on one single pressure-volume loop. We have evaluated four of these methods. Pressure-volume data were obtained by combined pressure and conductance catheters in 37 pigs. All four methods were applied to 88 steady-state pressure-volume files, including eight files sampled during dopamine infusions. Estimates of single-beat contractility (elastance) were compared with preload-varied multiple-beat elastance [ E es(MB)]. All methods had a low average bias (−0.3 to 0.5 mmHg/ml) but limits of agreement (±2 SD) were unacceptably high (±2.6 to ±3.8 mmHg/ml). In the dopamine group, E es(MB) showed an increase of 1.7 ± 0.8 mmHg/ml (mean ± SD) compared with baseline ( P < 0.001). None of the single-beat methods predicted this increase in contractility. It is therefore doubtful whether any of the methods allow for single-beat assessment of contractility.

Development of a Non-Blood Contacting Cardiac Assist and Support Device: An In Vivo Proof of Concept Study

2011 ◽  
Vol 5 (4) ◽  
Author(s):  
Michael R. Moreno ◽  
Saurabh Biswas ◽  
Lewis D. Harrison ◽  
Guilluame Pernelle ◽  
Matthew W. Miller ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Output ◽  
Support Function ◽  
Diastolic Pressure ◽  
Cardiac Motion ◽  
Proof Of Concept ◽  
Concept Study ◽  
Volume Relationship ◽  
Pressure Volume Relationship

One of the maladaptive changes following a heart attack is an initial decline in pumping capacity, which leads to activation of compensatory mechanisms, and subsequently, a phenomenon known as cardiac or left ventricular remodeling. Evidence suggests that mechanical cues are critical in the progression of congestive heart failure. In order to mediate two important mechanical parameters, cardiac size and cardiac output, we have developed a direct cardiac contact device capable of two actions: (1) adjustable cardiac support to modulate cardiac size and (2) synchronous active assist to modulate cardiac output. In addition, the device was designed to (1) remain in place about the heart without tethering, (2) allow free normal motion of the heart, and (3) provide assist via direct cardiac compression without abnormally inverting the curvature of the heart. The actions and features described above were mapped to particular design solutions and assessed in an acute implantation in an ovine model of acute heart failure (esmolol overdose). A balloon catheter was inflated in the vena cava to reduce preload and determine the end-diastolic pressure-volume relationship with and without passive support. A Millar PV Loop catheter was inserted in the left ventricle to acquire pressure-volume data throughout the experiments. Fluoroscopic imaging was used to investigate effects on cardiac motion. Implementation of the adjustable passive support function of the device successfully modulated the end-diastolic pressure-volume relationship toward normal. The active assist function successfully restored cardiac output and stroke work to healthy baseline levels in the esmolol induced failure model. The device remained in place throughout the experiment and when de-activated, did not inhibit cardiac motion. In this in vivo proof of concept study, we have demonstrated that a single device can be used to provide both passive constraint/support and active assist. Such a device may allow for controlled, disease specific, flexible intervention. Ultimately, it is hypothesized that the combination of support and assist could be used to facilitate cardiac rehabilitation therapy. The principles guiding this approach involve simply creating the conditions under which natural growth and remodeling processes are guided in a therapeutic manner. For example, the passive support function could be incrementally adjusted to gradually reduce the size of the dilated myocardium, while the active assist function can be implemented as necessary to maintain cardiac output and decompress the heart.

Interrelation between end-systolic pressure-volume and pressure-wall thickness relations

1988 ◽  
Vol 255 (3) ◽  
pp. H679-H684
Author(s):  
J. D. Schipke ◽  
J. Alexander ◽  
Y. Harasawa ◽  
R. Schulz ◽  
D. Burkhoff
Keyword(s):  
Pressure Range ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Ventricular Contractility ◽  
Ventricular Systolic Pressure ◽  
Straight Line ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Left Ventricular Systolic Pressure

We predicted the shape of the end-systolic pressure-thickness relationship (ESPTR) by modeling the left ventricle as thick-walled sphere. To test the validity of the predicted relationships, we then measured the ESPTR over wide volume ranges in seven isolated blood-perfused canine hearts. Both simulation and experiments demonstrated that the ESPTR is curvilinear. However, within a physiological left ventricular systolic pressure range (80–150 mmHg), the ESPTR was described reasonably well by a straight line. Within that pressure range, changes in left ventricular contractile state, assessed by slope changes of the end-systolic pressure-volume relationship, were associated with almost parallel shifts in the ESPTR. In contrast, in a low pressure range (less than 80 mmHg), contractility changes were associated with slope changes of the ESPTR. We conclude that, in general, there are limitations in the application of ESPTR for assessing left ventricular contractility, but if the limitations are recognized and accounted for, then the ESPTR may be useful for assessing contractility changes in vivo.

Assessing Pressure–Volume Relationship in Developing Heart of Zebrafish In-Vivo

2021 ◽  
Author(s):  
Nabid Salehin ◽  
Cameron Villarreal ◽  
Tanveer Teranikar ◽  
Benjamin Dubansky ◽  
Juhyun Lee ◽  
...  
Keyword(s):  
Developing Heart ◽  
Volume Relationship ◽  
Pressure Volume Relationship

Modulation of Diastolic Filling Using an Epicardial Diastolic Recoil Device

2013 ◽  
Vol 7 (3) ◽  
Author(s):  
Timothy Snowden ◽  
Saurabh Biswas ◽  
John Criscione
Keyword(s):  
Diastolic Dysfunction ◽  
Diastolic Filling ◽  
Heart Model ◽  
Volume Changes ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Viable Method ◽  
Heart Wall ◽  
Support Devices

Diastolic dysfunction likely contributes to all cases of congestive heart failure and is solely responsible for many. Existing cardiac support devices largely ignore diastolic dysfunction and may exacerbate it. Current diastolic devices in development rely on either extensive extraventricular fixation or intraventricular implantation with complications associated with blood contact. A diastolic recoil device is proposed that pneumatically locks to the outside of the heart wall. The end-diastolic total biventricular pressure-volume relationship (EDTBPVR) was used to evaluate, in vitro, the ability of a recoil device to modulate filling mechanics through pneumatic locking as the method of fixation. The pressure in a model heart was incremented and the corresponding volume changes were measured. The heart model and device were pneumatically locked together using a vacuum sac to model the pericardium. The diastolic recoil component shifted the EDTBPVR towards lower pressures at low volumes, providing up to 0.9 kPa (9 cm H2O) of suction, demonstrating enhanced diastolic recoil at beginning diastole. We conclude that pneumatic locking appears to be a viable method for a recoil device to engage the heart.

Abstract 17078: Myocardial Stiffness by Intrinsic Wave Propagation Method: Comparison With End-Diastolic Pressure-Volume Relationship

Circulation ◽  
2018 ◽  
Vol 138 (Suppl_1) ◽  
Author(s):  
Orawan Anupraiwan ◽  
Filip Ionescu ◽  
Ioana Petrescu ◽  
Patricia A Pellikka ◽  
Martha Grogan ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Diastolic Pressure ◽  
Left Ventricular ◽  
Frame Rate ◽  
Doppler Imaging ◽  
Wave Method ◽  
Myocardial Stiffness ◽  
Volume Relationship ◽  
Pressure Volume Relationship

Introduction: Intrinsic wave propagation is a novel approach to measure myocardial stiffness (MS) as validated in animal studies. Aims and Hypothesis: 1) To compare MS measured by the wave method with chamber stiffness (CS) derived from noninvasively estimated end-diastolic pressure-volume relationship (EDPVR) in patients; 2) To test the hypothesis that MS is superior to CS for predicting outcomes in patients with cardiac amyloidosis (CA). Methods: Prospective study in 56 patients with amyloidosis (CA: 38, noncardiac amyloidosis, NCA: 18; 90% AL-type; age 63 ± 10 yrs; ejection fraction 57 ± 11%) and 36 normal subjects (age 49 ± 13 years). Intrinsic velocity propagation of myocardial stretch (iVP), a measure of MS, was measured by ultra-high frame rate (250-465Hz) tissue Doppler imaging. Left ventricular (LV) EDPVR were reconstructed using the noninvasive single-beat method (Fig.A). Stiffness coefficients (α, β, load-independent) and CS (dP/dV) were calculated. End-diastolic pressure (EDP) was estimated from E/e’. Adverse events at follow-up (death, heart failure, stroke, significant arrhythmia) were recorded. Results: iVP was higher in CA compared to NCA and controls, indicating higher MS (Fig. B). This was confirmed by EDPVR, which were steeper and shifted leftward (Fig. A). The slope (β) of EDPVR and CS (dP/dV) were higher and LV capacitance (V 30 , volume at 30 mmHg) was lower in CA (Fig. A) and correlated with iVP (β: r = 0.59; CS dP/dV, r = 0.43; EDP, r = 0.61; all p<0.0001). Patients with higher LV thickness (r = 0.66), lower LV longitudinal strain (r = -0.57) and elevated NT-proBNP (r = 0.69) had higher iVP. At follow-up (median 2.5 years), after adjusting for relevant confounders, an iVP >2.7 m/s was strongly associated with excess events (p<0.0001; Fig. C) and was superior to measures of CS (dP/dV: p = 0.28; β >6.5: p = 0.03; Fig. D). Conclusions: Myocardial stiffness by intrinsic wave method shows similar findings to chamber stiffness by EDVPR, but is more strongly related to outcomes in patients with amyloidosis.

Viscoelastic Testing Methodologies for Tissue Engineered Blood Vessels

2005 ◽  
Vol 127 (7) ◽  
pp. 1176-1184 ◽  
Author(s):  
Joseph D. Berglund ◽  
Robert M. Nerem ◽  
Athanassios Sambanis
Keyword(s):  
Blood Vessels ◽  
Mechanical Performance ◽  
Uniaxial Tensile ◽  
Collagen Gels ◽  
Uniaxial Tensile Testing ◽  
Modeling Systems ◽  
Tissue Engineered Blood Vessels ◽  
Linear Viscoelastic

In order to function in vivo, tissue engineered blood vessels (TEBVs) must encumber pulsatile blood flow and withstand hemodynamic pressures for long periods of time. To date TEBV mechanical assessment has typically relied on single time point burst and/or uniaxial tensile testing to gauge the strengths of the constructs. This study extends this analysis to include creep and stepwise stress relaxation viscoelastic testing methodologies. TEBV models exhibiting diverse mechanical behaviors as a result of different architectures ranging from reconstituted collagen gels to hybrid constructs reinforced with either untreated or glutaraldhyde-crosslinked collagen supports were evaluated after 8 and 23 days of in vitro culturing. Data were modeled using three and four-parameter linear viscoelastic mathematical representations and compared to porcine carotid arteries. While glutaraldhyde-treated hybrid TEBVs exhibited the largest overall strengths and toughness, uncrosslinked hybrid samples exhibited time-dependent behaviors most similar to native arteries. These findings emphasize the importance of viscoelastic characterization when evaluating the mechanical performance of TEBVs. Limits of testing methods and modeling systems are presented and discussed.

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