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Non-invasive assessment of patient-specific aortic haemodynamics from four-dimensional flow MRI data.

ABSTRACT: We introduce a parameter estimation framework for automatically and robustly personalizing aortic haemodynamic computations from four-dimensional magnetic resonance imaging data. The framework is based on a reduced-order multiscale fluid-structure interaction blood flow model, and on two calibration procedures. First, Windkessel parameters of the outlet boundary conditions are personalized by solving a system of nonlinear equations. Second, the regional mechanical wall properties of the aorta are personalized by employing a nonlinear least-squares minimization method. The two calibration procedures are run sequentially and iteratively until both procedures have converged. The parameter estimation framework was successfully evaluated on 15 datasets from patients with aortic valve disease. On average, only 1.27 ± 0.96 and 7.07 ± 1.44 iterations were required to personalize the outlet boundary conditions and the regional mechanical wall properties, respectively. Overall, the computational model was in close agreement with the clinical measurements used as objectives (pressures, flow rates, cross-sectional areas), with a maximum error of less than 1%. Given its level of automation, robustness and the short execution time (6.2 ± 1.2 min on a standard hardware configuration), the framework is potentially well suited for a clinical setting.

SUBMITTER: Itu L

PROVIDER: S-EPMC5740219 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Non-invasive assessment of patient-specific aortic haemodynamics from four-dimensional flow MRI data.

Itu Lucian L Neumann Dominik D Mihalef Viorel V Meister Felix F Kramer Martin M Gulsun Mehmet M Kelm Marcus M Kühne Titus T Sharma Puneet P

Interface focus 20171215 1

We introduce a parameter estimation framework for automatically and robustly personalizing aortic haemodynamic computations from four-dimensional magnetic resonance imaging data. The framework is based on a reduced-order multiscale fluid-structure interaction blood flow model, and on two calibration procedures. First, Windkessel parameters of the outlet boundary conditions are personalized by solving a system of nonlinear equations. Second, the regional mechanical wall properties of the aorta ar ...[more]

PMID: 29285343

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Project description:BACKGROUND:While primarily a right heart disease, pulmonary arterial hypertension (PAH) can impact left heart function and aortic flow through a shifted interventricular septum from right ventricular pressure overload and reduced left ventricular preload, among other mechanisms. In this study, we used phase contrast (PC) MRI and a modest exercise challenge to examine the effects of PAH on systemic circulation. While exercise challenges are typically performed with ultrasound in the clinic, MRI exercise studies allow for more reproducible image alignment, more accurate flow quantification, and improved tissue contrast. METHODS:Six PAH patients and fifteen healthy controls (8 older age-matched, 7 younger) exercised in the magnet bore with an MRI-compatible exercise device that allowed for scanning immediately following cessation of exercise. PC scans were performed in the ascending aorta during a breath hold immediately after modest exercise to non-invasively measure stroke volume (SV), cardiac output (CO), aortic peak systolic flow (PSF), and aortic wall stiffness via relative area change (RAC). RESULTS:Images following exercise showed mild blurring, but were high enough quality to allow for segmentation of the aorta. While SV was approximately 30% lower in PAH patients (SVPAH,rest?=?67?±?16?mL; SVPAH,stress?=?90?±?42?mL) than age-matched controls (SV,older,rest?=?93?±?16?mL; SVolder,stress?=?133?±?40?mL) at both rest and following exercise, CO was similar for both groups following exercise (COPAH,stress?=?10.8?±?5.7?L/min; COolder,stress?=?11.8?±?5.0?L/min). This was achieved through a compensatory increase in heart rate in the PAH subjects (74% increase as compared to 29% in age-matched controls). The PAH subjects also demonstrated reduced aortic peak systolic flow relative to the healthy controls (PSFPAH,rest?=?309?±?52?mL/s; PSFolder,rest?=?416?±?114?mL/s; PSFPAH,stress?=?388?±?113?mL/s; PSFolder,stress?=?462?±?176?mL/s). PAH patients and older controls demonstrated stiffer aortic walls when compared to younger controls (RACPAH,rest?=?0.15?±?0.05; RAColder,rest?=?0.17?±?0.05; RACyoung,rest?=?0.28?±?0.08). CONCLUSIONS:PC MRI following a modest exercise challenge was capable of detecting differences in left heart dynamics likely induced from PAH. These results demonstrated that PAH can have a significant influence on systemic flow, even when the patient has no prior left heart disease. Image quantification following exercise could likely be improved in future studies through the implementation of free-breathing or real-time MRI acquisitions. TRIAL REGISTRATION:Retrospectively registered on 02/26/2018 (TRN: NCT03523910 ).

Project description:AimsIn patients with aortic stenosis (AS), B-type natriuretic peptide (BNP) is a prognostic marker. However, there is little information on the association between BNP and invasive haemodynamics in AS. The aim of the present study was to assess the hitherto not well-defined relationship between BNP and invasive haemodynamics in patients with severe AS undergoing aortic valve replacement (AVR) with a view to understand the link between high BNP and poor prognosis in these patients. In particular, we were interested in the association between BNP and combined pre-capillary and post-capillary pulmonary hypertension (CpcPH).Methods and resultsBNP was measured in 252 patients (age 74 ± 10 years, 58% male patients) with severe AS [indexed aortic valve area 0.4 ± 0.1 cm2 /m2 and left ventricular ejection fraction (LVEF) 57 ± 12%] the day before cardiac catheterization. Patients were followed for a median (interquartile range) period of 3.1 (2.3-4.3) years after surgical (n = 157) or transcatheter (n = 95) AVR. The prevalence of CpcPH (mean pulmonary artery pressure ≥ 25 mmHg, mean pulmonary artery wedge pressure > 15 mmHg, and pulmonary vascular resistance > 3 Wood units) was 13%. The median BNP plasma concentration was 188 (78-452) ng/L. The indexed aortic valve area was similar across BNP quartiles (P = 0.21). Independent predictors of higher BNP (ln transformed) included lower haemoglobin (beta = -0.18; P < 0.001), lower LVEF (beta = -0.20; P < 0.001), more severe mitral regurgitation (beta = 0.20; P < 0.001), higher mean pulmonary artery wedge pressure (beta = -0.37; P < 0.001), and higher pulmonary vascular resistance (beta = 0.21; P < 0.001). In a multivariate model with CpcPH rather than its haemodynamic components, CpcPH was independently associated with higher BNP (0.21; P < 0.001). Higher ln BNP was associated with higher mortality [hazard ratio 1.90 (95% confidence interval 1.33-2.71); P < 0.001] in the univariate analysis. Patients in the third and fourth BNP quartiles had a more than six-fold risk of death compared with patients in the first and second quartiles [hazard ratio 6.29 (95% confidence interval 1.86-21.27); P = 0.003]. In the multivariate analysis, lower LVEF [hazard ratio 0.96 (95% confidence interval 0.94-0.99) per 1% increase; P = 0.01] and CpcPH [hazard ratio 4.58 (95% confidence interval 1.89-11.09); P = 0.001] but not BNP were independently associated with mortality. The areas under the receiver operator characteristics curve for BNP for the prediction of CpcPH and mortality were 0.88 and 0.74, respectively.ConclusionsIn patients with severe AS, higher BNP is a marker of the presence of CpcPH and its contributors. The association between BNP and such an adverse haemodynamic profile at least in part explains the ability of BNP to predict long-term post-AVR mortality.

Dataset Information

Non-invasive assessment of patient-specific aortic haemodynamics from four-dimensional flow MRI data.

Publications

Non-invasive assessment of patient-specific aortic haemodynamics from four-dimensional flow MRI data.

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