scholarly journals Uncertainty quantification and sensitivity analysis of left ventricular function during the full cardiac cycle

2020 ◽  
Vol 378 (2173) ◽  
pp. 20190381 ◽  
Author(s):  
J. O. Campos ◽  
J. Sundnes ◽  
R. W. dos Santos ◽  
B. M. Rocha
Keyword(s):  
Uncertainty Quantification ◽  
Wall Thickness ◽  
Cardiac Cycle ◽  
Fibre Orientation ◽  
Left Ventricular ◽  
Sensitivity Analyses ◽  
Patient Specific ◽  
Model Parameters ◽  
Fibre Direction ◽  
Active Stress

Patient-specific computer simulations can be a powerful tool in clinical applications, helping in diagnostics and the development of new treatments. However, its practical use depends on the reliability of the models. The construction of cardiac simulations involves several steps with inherent uncertainties, including model parameters, the generation of personalized geometry and fibre orientation assignment, which are semi-manual processes subject to errors. Thus, it is important to quantify how these uncertainties impact model predictions. The present work performs uncertainty quantification and sensitivity analyses to assess the variability in important quantities of interest (QoI). Clinical quantities are analysed in terms of overall variability and to identify which parameters are the major contributors. The analyses are performed for simulations of the left ventricle function during the entire cardiac cycle. Uncertainties are incorporated in several model parameters, including regional wall thickness, fibre orientation, passive material parameters, active stress and the circulatory model. The results show that the QoI are very sensitive to active stress, wall thickness and fibre direction, where ejection fraction and ventricular torsion are the most impacted outputs. Thus, to improve the precision of models of cardiac mechanics, new methods should be considered to decrease uncertainties associated with geometrical reconstruction, estimation of active stress and of fibre orientation. This article is part of the theme issue ‘Uncertainty quantification in cardiac and cardiovascular modelling and simulation’.

Assessment of Myocardial Viability in Persistent Defects on Thallium-201 SPECT after Reinjection Using Gradient-Echo MRI

1996 ◽  
Vol 35 (05) ◽  
pp. 146-152 ◽  
Author(s):  
A. Kögler ◽  
H.-A. Schmitt ◽  
D. Emrich ◽  
H. Kreuzer ◽  
D. L. Munz ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Myocardial Viability ◽  
Cardiac Cycle ◽  
Single Photon ◽  
Contractile Function ◽  
Left Ventricular ◽  
Wall Thickening ◽  
Gradient Echo ◽  
Systolic Wall Thickening

SummaryThis prospective study assessed myocardial viability in 30 patients with coronary heart disease and persistent defects despite reinjection on TI-201 single-photon computed tomography (SPECT). In each patient, three observers graded TI-201 uptake in 7 left ventricular wall segments. Gradient-echo magnetic resonance imaging in the region of the persistent defect generated 12 to 16 short axis views representing a cardiac cycle. A total of 120 segments were analyzed. Mean end-diastolic wall thickness and systolic wall thickening (± SD) was 11.5 ± 2.7 mm and 5.8 ± 3.9 mm in 48 segments with normal TI-201 uptake, 10.1 ± 3.4 mm and 3.7 ± 3.1 mm in 31 with reversible lesions, 11.3 ± 2.8 mm and 3.3 ± 1.9 mm in 10 with mild persistent defects, 9.2 ± 2.9 mm and 3.2 ±2.2 mm in 15 with moderate persistent defects, 5.8 ± 1.7 mm and 1.3 ± 1.4 mm in 16 with severe persistent defects, respectively. Significant differences in mean end-diastolic wall thickness (p <0.0005) and systolic wall thickening (p <0.005) were found only between segments with severe persistent defects and all other groups, but not among the other groups. On follow-up in 11 patients after revascularization, 6 segments with mild-to-moderate persistent defects showed improvement in mean systolic wall thickening that was not seen in 6 other segments with severe persistent defects. These data indicate that most myocardial segments with mild and moderate persistent TI-201 defects after reinjection still contain viable tissue. Segments with severe persistent defects, however, represent predominantly nonviable myocardium without contractile function.

Porous medium finite element model of the beating left ventricle

1992 ◽  
Vol 262 (4) ◽  
pp. H1256-H1267 ◽  
Author(s):  
J. M. Huyghe ◽  
T. Arts ◽  
D. H. van Campen ◽  
R. S. Reneman
Keyword(s):  
Left Ventricle ◽  
Wall Thickness ◽  
Cardiac Cycle ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Fiber Direction ◽  
Intraventricular Pressure ◽  
Angle Distribution ◽  
Fiber Angle ◽  
Intramyocardial Pressure

The axisymmetric model described represents myocardial tissue as a spongy anisotropic viscoelastic material. It includes torsion around the axis of symmetry of the ventricle, transmural variation of fiber angle, and redistribution of intracoronary blood in the myocardial wall. In simulations, end-systolic principal strains were equal to 0.45, -0.01, and -0.24 at two-thirds of the wall thickness from the epicardium and 0.26, 0.00, and -0.19 at one-third of the wall thickness from the epicardium. The direction of maximal shortening varied by less than 30 degrees from epicardium to endocardium, whereas fiber direction varied by greater than 100 degrees from epicardium to endocardium. During a normal cardiac cycle peak, equatorial intramyocardial pressure differed by less than 5% from peak intraventricular pressure. When redistribution of intracoronary blood in the ventricular wall was suppressed, peak equatorial intramyocardial pressure was found to exceed peak intraventricular pressure by greater than 30%. Simulated contraction of an unloaded left ventricle (left ventricular pressure = 0 kPa) produced similar magnitude for systolic intramyocardial pressures as the normal cardiac cycle. Transmural systolic fiber stress distribution was very sensitive to the chosen transmural fiber angle distribution.

scholarly journals Uncertainty Quantification of Regional Cardiac Tissue Properties in Arrhythmogenic Cardiomyopathy Using Adaptive Multiple Importance Sampling

2021 ◽  
Vol 12 ◽  
Author(s):  
Nick van Osta ◽  
Feddo P. Kirkels ◽  
Tim van Loon ◽  
Tijmen Koopsen ◽  
Aurore Lyon ◽  
...  
Keyword(s):  
Uncertainty Quantification ◽  
Importance Sampling ◽  
Left Ventricular ◽  
Patient Specific ◽  
Intraobserver Variability ◽  
Posterior Distributions ◽  
Arrhythmogenic Cardiomyopathy ◽  
True Parameter ◽  
Tissue Properties ◽  
Multiple Importance Sampling

Introduction: Computational models of the cardiovascular system are widely used to simulate cardiac (dys)function. Personalization of such models for patient-specific simulation of cardiac function remains challenging. Measurement uncertainty affects accuracy of parameter estimations. In this study, we present a methodology for patient-specific estimation and uncertainty quantification of parameters in the closed-loop CircAdapt model of the human heart and circulation using echocardiographic deformation imaging. Based on patient-specific estimated parameters we aim to reveal the mechanical substrate underlying deformation abnormalities in patients with arrhythmogenic cardiomyopathy (AC).Methods: We used adaptive multiple importance sampling to estimate the posterior distribution of regional myocardial tissue properties. This methodology is implemented in the CircAdapt cardiovascular modeling platform and applied to estimate active and passive tissue properties underlying regional deformation patterns, left ventricular volumes, and right ventricular diameter. First, we tested the accuracy of this method and its inter- and intraobserver variability using nine datasets obtained in AC patients. Second, we tested the trueness of the estimation using nine in silico generated virtual patient datasets representative for various stages of AC. Finally, we applied this method to two longitudinal series of echocardiograms of two pathogenic mutation carriers without established myocardial disease at baseline.Results: Tissue characteristics of virtual patients were accurately estimated with a highest density interval containing the true parameter value of 9% (95% CI [0–79]). Variances of estimated posterior distributions in patient data and virtual data were comparable, supporting the reliability of the patient estimations. Estimations were highly reproducible with an overlap in posterior distributions of 89.9% (95% CI [60.1–95.9]). Clinically measured deformation, ejection fraction, and end-diastolic volume were accurately simulated. In presence of worsening of deformation over time, estimated tissue properties also revealed functional deterioration.Conclusion: This method facilitates patient-specific simulation-based estimation of regional ventricular tissue properties from non-invasive imaging data, taking into account both measurement and model uncertainties. Two proof-of-principle case studies suggested that this cardiac digital twin technology enables quantitative monitoring of AC disease progression in early stages of disease.

Left ventricular wall stress normalization in chronic pressure-overloaded heart: a mathematical model study

2000 ◽  
Vol 279 (3) ◽  
pp. H1120-H1127 ◽  
Author(s):  
Patrick Segers ◽  
Nikos Stergiopulos ◽  
Jan J. Schreuder ◽  
Berend E. Westerhof ◽  
Nico Westerhof
Keyword(s):  
Blood Pressure ◽  
Wall Thickness ◽  
Alternative Hypothesis ◽  
Pressure Overload ◽  
Wall Stress ◽  
Quantitative Agreement ◽  
Left Ventricular ◽  
Lumped Parameter Model ◽  
Model Parameters

It is generally accepted that the left ventricle (LV) hypertrophies (LVH) to normalize systolic wall stress (ςs) in chronic pressure overload. However, LV filling pressure (Pv) may be elevated as well, supporting the alternative hypothesis of end-diastolic wall stress (ςd) normalization in LVH. We used an LV time-varying elastance model coupled to an arterial four-element lumped-parameter model to study ventricular-arterial interaction in hypertension-induced LVH. We assessed model parameters for normotensive controls and applied arterial changes as observed in hypertensive patients with LVH (resistance +40%, compliance −25%) and assumed 1) no cardiac adaptation, 2) normalization of ςs by LVH, and 3) normalization of ςs by LVH and increase in Pv, such that ςd is normalized as well. In patients, systolic and diastolic blood pressures increase by ∼40%, cardiac output (CO) is constant, and wall thickness increases by 30–55%. In scenarios 1 and 2, blood pressure increased by only 10% while CO dropped by 20%. In scenario 2, LV wall thickness increased by only 10%. The predictions of scenario 3 were in qualitative and quantitative agreement with in vivo human data. LVH thus contributes to the elevated blood pressure in hypertension, and cardiac adaptations include an increase in Pv, normalization of ςs, and preservation of CO in the presence of an impaired diastolic function.

scholarly journals Phenotyping heart failure using model-based analysis and physiology-informed machine learning

2021 ◽  
Author(s):  
Edith Jones ◽  
E. Benjamin Randall ◽  
Scott L. Hummel ◽  
David Cameron ◽  
Daniel A. Beard ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiovascular System ◽  
Specific Treatment ◽  
Left Ventricular ◽  
Patient Specific ◽  
Health Improvement ◽  
Model Parameters ◽  
Loop Model ◽  
Improvement Project ◽  
Model Based

AbstractTo determine the underlying mechanistic differences between diagnoses of Heart Failure (HF) and specifically heart failure with reduced and preserved ejection fraction (HFrEF & HFpEF), a closed loop model of the cardiovascular system coupled with patient specific transthoracic echocardiography (TTE) and right heart catheterization (RHC) measures was used to identify key parameters representing cardiovascular hemodynamics. Thirty-one patient records (10 HFrEF, 21 HFpEF) were obtained from the Cardiovascular Health Improvement Project (CHIP) database at the University of Michigan. Model simulations were tuned to match RHC and TTE pressure, volume and cardiac output measures in each patient with average error between data and model of 4.87 ± 2%. The underlying physiological model parameters were then plotted against model-based norms and compared between the HFrEF and HFpEF group. Our results confirm that the main mechanistic parameter driving HFrEF is reduced left ventricular contractility, while for HFpEF a much wider underlying phenotype is presented. Conducting principal component analysis (PCA), k-means, and hierarchical clustering on the optimized model parameters, but not on clinical measures, shows a distinct group of HFpEF patients sharing characteristics with the HFrEF cohort, a second group that is distinct as HFpEF and a group that exhibits characteristics of both. Significant differences are observed (p-value<.001) in left ventricular active contractility and left ventricular relaxation, when comparing HFpEF patients to those grouped as similar to HFrEF. These results suggest that cardiovascular system modeling of standard clinical data is able to phenotype and group HFpEF as different subdiagnoses, possibly elucidating patient-specific treatment strategies.

Myoglobin oxygenation remains constant during the cardiac cycle

1983 ◽  
Vol 245 (2) ◽  
pp. H237-H243 ◽  
Author(s):  
N. Makino ◽  
H. Kanaide ◽  
R. Yoshimura ◽  
M. Nakamura
Keyword(s):  
Steady State ◽  
Oxygen Saturation ◽  
Fiber Optics ◽  
Wall Thickness ◽  
Cardiac Cycle ◽  
Left Ventricular ◽  
Isolated Rat Heart ◽  
Left Ventricular Free Wall ◽  
Absorbance Change ◽  
Aerobic And Anaerobic

Oxygen saturation of myoglobin (Mb) during the cardiac cycle was recorded spectrophotometrically by incorporating fiber optics in the isolated rat heart perfused using the Langendorff procedure. Oxygen saturation of Mb was continuously measured from absorbancy increments at 581-592 nm of transmitted light through the left ventricular free wall. In addition, quantification in the Mb oxygen saturation induced by the change of wall thickness during cardiac cycle was assessed from the absorbance change at 568-592 nm, namely, dual wavelengths of two isosbestic points. The results show that to obtain actual Mb oxygen saturation the absorbance change induced by the change in the wall thickness has to be subtracted from the absorbance change of 581-592 nm and that the Mb oxygen saturation in a steady state determines the amount of subtraction. On the basis of these procedures, it was found that the myocardial Mb oxygen saturation and hence myocardial oxygen tension during pulsation in aerobic and anaerobic steady state did not vary during the cardiac cycle.

scholarly journals The impact of wall thickness and curvature on wall stress in patient-specific electromechanical models of the left atrium

2019 ◽  
Vol 19 (3) ◽  
pp. 1015-1034 ◽  
Author(s):  
Christoph M. Augustin ◽  
Thomas E. Fastl ◽  
Aurel Neic ◽  
Chiara Bellini ◽  
John Whitaker ◽  
...  
Keyword(s):  
Left Atrium ◽  
Wall Thickness ◽  
Wall Stress ◽  
Sensitivity Analyses ◽  
Patient Specific ◽  
Cauchy Stress ◽  
Contraction Phase ◽  
Relative Contribution ◽  
Complex Anatomy ◽  
The Impact

AbstractThe left atrium (LA) has a complex anatomy with heterogeneous wall thickness and curvature. The anatomy plays an important role in determining local wall stress; however, the relative contribution of wall thickness and curvature in determining wall stress in the LA is unknown. We have developed electromechanical finite element (FE) models of the LA using patient-specific anatomical FE meshes with rule-based myofiber directions. The models of the LA were passively inflated to 10mmHg followed by simulation of the contraction phase of the atrial cardiac cycle. The FE models predicted maximum LA volumes of 156.5 mL, 99.3 mL and 83.4 mL and ejection fractions of 36.9%, 32.0% and 25.2%. The median wall thickness in the 3 cases was calculated as $$1.32\, \pm \,0.78$$1.32±0.78 mm, $$1.21\, \pm \,0.85$$1.21±0.85 mm, and $$0.74\,\pm \,0.34$$0.74±0.34 mm. The median curvature was determined as $$0.159\,\pm \,0.080$$0.159±0.080 $$\hbox {mm}^{-1}$$mm-1, $$0.165\,\pm \,0.079\,\hbox {mm}^{-1}$$0.165±0.079mm-1, and $$0.166\,\pm \,0.077\,\hbox {mm}^{-1}$$0.166±0.077mm-1. Following passive inflation, the correlation of wall stress with the inverse of wall thickness and curvature was 0.55–0.62 and 0.20–0.25, respectively. At peak contraction, the correlation of wall stress with the inverse of wall thickness and curvature was 0.38–0.44 and 0.16–0.34, respectively. In the LA, the 1st principal Cauchy stress is more dependent on wall thickness than curvature during passive inflation and both correlations decrease during active contraction. This emphasizes the importance of including the heterogeneous wall thickness in electromechanical FE simulations of the LA. Overall, simulation results and sensitivity analyses show that in complex atrial anatomy it is unlikely that a simple anatomical-based law can be used to estimate local wall stress, demonstrating the importance of FE analyses.

Nonlinear Anisotropic Stress Analysis of Anatomically Realistic Cerebral Aneurysms

2006 ◽  
Vol 129 (1) ◽  
pp. 88-96 ◽  
Author(s):  
Baoshun Ma ◽  
Jia Lu ◽  
Robert E Harbaugh ◽  
Madhavan L. Raghavan
Keyword(s):  
Disease Process ◽  
Elastic Strain Energy ◽  
Cerebral Aneurysms ◽  
Static Deformation ◽  
Sensitivity Analyses ◽  
Patient Specific ◽  
Deformation Analysis ◽  
Accurate Estimation ◽  
Model Parameters ◽  
Aneurysm Wall

Background. Static deformation analysis and estimation of wall stress distribution of patient-specific cerebral aneurysms can provide useful insights into the disease process and rupture. Method of Approach. The three-dimensional geometry of saccular cerebral aneurysms from 27 patients (18 unruptured and nine ruptured) was reconstructed based on computer tomography angiography images. The aneurysm wall tissue was modeled using a nonlinear, anisotropic, hyperelastic material model (Fung-type) which was incorporated in a user subroutine in ABAQUS. Effective material fiber orientations were assumed to align with principal surface curvatures. Static deformation of the aneurysm models were simulated assuming uniform wall thickness and internal pressure load of 100mmHg. Results. The numerical analysis technique was validated by quantitative comparisons to results in the literature. For the patient-specific models, in-plane stresses in the aneurysm wall along both the stiff and weak fiber directions showed significant regional variations with the former being higher. The spatial maximum of stress ranged from as low as 0.30MPa in a small aneurysm to as high as 1.06MPa in a giant aneurysm. The patterns of distribution of stress, strain, and surface curvature were found to be similar. Sensitivity analyses showed that the computed stress is mesh independent and not very sensitive to reasonable perturbations in model parameters, and the curvature-based criteria for fiber orientations tend to minimize the total elastic strain energy in the aneurysms wall. Within this small study population, there were no statistically significant differences in the spatial means and maximums of stress and strain values between the ruptured and unruptured groups. However, the ratios between the stress components in the stiff and weak fiber directions were significantly higher in the ruptured group than those in the unruptured group. Conclusions. A methodology for nonlinear, anisotropic static deformation analysis of geometrically realistic aneurysms was developed, which can be used for a more accurate estimation of the stresses and strains than previous methods and to facilitate prospective studies on the role of stress in aneurysm rupture.

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