valve orifice area
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Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Andrew D Wisneski ◽  
Yunjie Wang ◽  
Reza Salari ◽  
Steve Levine ◽  
Jiang Yao ◽  
...  

Introduction: Grading aortic stenosis (AS) has traditionally relied on measuring hemodynamic parameters of transvalvular pressure gradient, ejection jet velocity, or estimating valve orifice area. Recent research has highlighted limitations of these criteria at effectively grading AS in presence of left ventricle (LV) dysfunction. We hypothesize that simulations coupling the aorta and LV will provide meaningful insight into myocardial biomechanical derangements that accompany AS. Reference data from the normal ventricle should first be obtained. Methods: A multi-domain cardiac model with representative anatomy and material properties was used to create AS simulations. Finite element analysis was performed with ABAQUS FEA®. An anisotropic hyperelastic model was assigned to the aorta and LV passive properties, while time-varying elastance function governed LV active response. Mild and severe AS were created by restricting the aortic valve orifice area. Results: Global LV myofiber end systolic (ES) stress (mean±SD) was 9.31±10.33 kPa at baseline (no AS), 13.13±10.29 kPa for mild AS, and 16.18±10.59 kPa with severe AS. Mean LV myofiber ES strains were -22.4±8.7%, -22.2±8.9%, and -21.9±9.2%, respectively. Mild and severe AS had significant stress elevation compared to baseline (mild AS vs base; p<0.01, severe AS vs base; p<0.001) and when compared to each other (p<0.01). See Figure 1 . Ventricular regions that experienced greatest magnitude ES stress were (severe AS vs baseline) basal inferior (39.87±14.73 vs 30.02±12.08 kPa; p<0.01), mid-anteroseptal (32.29±11.56 vs 24.79±12.00 kPa; p<0.001), and apex (27.99±8.44 vs 23.52±10.19 kPa; p<0.001). Conclusions: Isolated AS in a normal heart was simulated, and significantly elevated LV myofiber stress was quantified. This data serves as a comparison to future studies that will incorporate patient-specific ventricular geometries and material parameters, aiming to correlate LV biomechanics to AS severity.


Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Sandra Hadjadj ◽  
Afonso B. Freitas-Ferraz ◽  
Amélie Paquin ◽  
Mathieu Bernier ◽  
Kim O'Connor ◽  
...  

Introduction: The MitraClip procedure is a non-surgical alternative for patients with severe mitral regurgitation and high surgical risk. However, the MitraClip may lead to a reduction in the mitral valve orifice area (MVOA) and elevated transmitral mean gradients (TMG). The objectives of this study are to assess the value of baseline MVOA by different imaging methods and explore the value of MVOA indexed for left ventricular (LV) forward stroke volume (SV) to predict postprocedural TMG. Methods: Preprocedural echo images were retrospectively reviewed in 76 consecutive patients. MVOA from 2D transthoracic (MVOA TTE ), 2D transgastric (MVOA TG ) and 3D transesophageal (MVOA 3D ) echocardiography were measured and then indexed by the SV measured by Doppler in the LV outflow tract (MVOA/SV) . Postprocedural TMG was measured at one month and survival rate at one year. Results: Patients with postprocedural TMG >5 mmHg (18/76, 24%) had significantly smaller preprocedural MVOA 3D (3.9±0.9 vs 5.2±1.3 cm 2 , p<0.01) and MVOA TTE (4.9±1.1 vs 5.9±1.5 cm 2 , p=0.02). No significant difference was found for MVOA TG (5.5±1.4 vs 5.9±1.4 cm 2 , p=0.2). Best threshold values for MVOA 3D and MVOA TTE to predict postprocedural TMG >5 mmHg were respectively 3.9 cm 2 (AUC=0.80, IC95%: 0.67-0.94, p<0.01; sensitivity (Se) 62%, specificity (Sp) 87%) and 4,6 cm 2 (AUC=0.69, IC95%: 0.54-0.83, p=0.02; Se 50%, Sp 84%). MVOA/SV from each echocardiographic modality were smaller in patients with postprocedural TMG >5 mmHg (3D: 80 [62-95] vs 113 [99-129] cm 2 /L; TTE: 92 [81-105] vs 130 [100-166] cm 2 /L; TG: 104 [83-123] vs 135 [104-166] cm 2 /L; p<0.01 for all). MVOA/SV 3D was overall the best predictor of postprocedural TMG >5 mmHg, with an optimal threshold of 96 cm 2 /L (AUC=0.86, IC95%: 0.76-0.97, p<0.001; Se 84%, Sp 81%). Patients with MVOA 3D <3.9 cm 2 and MVOA/SV 3D <96 cm 2 /L tend to be at higher risk for mortality at one-year follow-up (69% vs 84%, p=0.14 and 67% vs 87%, p=0.11 respectively). Conclusion: Unlike preprocedural MVOAs assessed by 3D echocardiography, preprocedural MVOAs measured by 2D echocardiographic modalities were poor predictors of high TMG after MitraClip. Preprocedural MVOA 3D <3.9 cm 2 and MVOA/SV 3D <96 cm 2 /L were found to be the best cut-off values to predict postprocedural TMG >5 mmHg.


2018 ◽  
pp. 105-111 ◽  
Author(s):  
C Bleakley ◽  
M Eskandari ◽  
O Aldalati ◽  
K Moschonas ◽  
M Huang ◽  
...  

Background The mitral valve orifice area (MVOA) is difficult to assess accurately by 2D echocardiography because of geometric assumptions; therefore, 3D planimetry may offer advantages. We studied the differences in MVOA measurements between the most frequently used methods, to determine if 3D planimetry would result in the re-grading of severity in any cases, and whether it was a more accurate predictor of clinical outcomes. Methods This was a head-to-head comparison of the three most commonly used techniques to grade mitral stenosis (MS) by orifice area and to assess their impact on clinical outcomes. 2D measurements (pressure half-time (PHT), planimetry) and 3D planimetry were performed retrospectively on patients with at least mild MS. The clinical primary endpoint was defined as a composite of MV balloon valvotomy, mitral valve repair or replacement (MVR) and/or acute heart failure (HF) admissions. Results Forty-one consecutive patients were included; the majority were female (35; 85.4%), average age 55 (17) years. Mean and peak MV gradients were 9.4 (4) mmHg and 19 (6) mmHg, respectively. 2D and 3D measures of MVOA differed significantly; mean 2D planimetry MVOA was 1.28 (0.40) cm2, mean 3D planimetry MVOA 1.15 (0.29) cm2 (P = 0.003). Mean PHT MVOA was 1.43 (0.44) cm2 (P = 0.046 and P < 0.001 in comparison to 2D and 3D planimetry methods, respectively). 3D planimetry reclassified 7 (17%) patients from mild-to-moderate MS, and 1 (2.4%) from moderate to severe. Overall, differences between the two methods were significant (X2, P < 0.001). Only cases graded as severe by 3D predicted the primary outcome measure compared with mild or moderate cases (odds ratio 5.7). Conclusion 3D planimetry in MS returns significantly smaller measurements, which in some cases results in the reclassification of severity. Routine use of 3D may significantly influence the management of MS, with a degree of prediction of clinical outcomes.


2016 ◽  
Vol 69 (9) ◽  
pp. 772-776 ◽  
Author(s):  
Antoine S Kishabongo ◽  
Philippe Katchunga ◽  
Justin C Cikomola ◽  
Filip M De Somer ◽  
Marc L De Buyzere ◽  
...  

AimsHuman heart valves are prone to glycation, a fundamental process of ageing. The aim of this study was to establish the relationship between fructosamine formation and the mechanical properties of human aortic valves.Methods67 patients (age: 76±8 years) diagnosed with an aortic valve stenosis, who underwent an aortic valve replacement were enrolled. Fructosamine and calcium concentrations in aortic valves were determined. Using a transthoracic Doppler echocardiography, aortic valve orifice area and transvalvular pressure gradients were measured. In a subgroup of 32 patients, the aortic valve orifice area was sufficient to carry out mechanical testing on a LFPlus Universal material tester. An in vitro removal of fructosamine of the valve was initiated using ATP-dependent fructosamine 3-kinase (FN3K).ResultsA significant correlation was found between the aortic valve fructosamine concentration and the calculated aortic valve orifice area: Y (aortic valve orifice area, mm2)=1.050−0.228X (aortic valve fructosamine concentration, µmol/g valve) (r=−0.38). A significantly higher calcium concentration was measured in the aortic valves of diabetics in comparison with those of non-diabetics. A multiple regression analysis revealed that the presence of diabetes mellitus and aortic valve fructosamine concentration were the main predictors of the extensibility of the aortic valves. In the in vitro deglycation study, a significant lower aortic valve fructosamine concentration was detected after treatment with FN3K. This resulted in an increased flexibility of the aortic valves.ConclusionsAlthough no direct causativeness is proven with the presented results, which just show an association between fructosamine, the effect of FN3K and aortic valve stiffness, the present study points for the first time towards a possible additional role of the Amadori products in the biomechanical properties of ageing aortic valves.


Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Sumeet S Mitter ◽  
Gregory J Wagner ◽  
Alex J Barker ◽  
Michael Markl ◽  
James D Thomas

Introduction: Hydrodynamic theory predicts fluid approaches a point orifice with accelerating velocity in hemispheric shells, forming the basis for the proximal isovelocity surface area (PISA) method to quantify valve regurgitation. Previous CFD and in vitro work has shown that with a finite, non-point orifice, there is a small, systematic underestimation of flow that is approximately the ratio of contour velocity (va) to maximal orifice velocity (vo), e.g., roughly an 8% error if a 40 cm/s contour is used with a 5 m/s jet. The PISA method is further questioned in the setting of noncircular orifices, with concerns of further underestimation. We sought to quantify this impact with CFD. Hypothesis: Application of standard PISA analysis to an elliptical orifice leads to further flow underestimation, but the magnitude is negligible. Methods: Mathematical modeling of flow through a finite elliptical orifice was computed using the open-source incompressible flow solver Nalu. Forty-five permutations of valve flow were characterized by varying valve orifice area (0.1, 0.3 and 0.5 cm^2), ellipse axis ratios (1:1, 2:1, 3:1, 5:1, and 10:1), and max velocity (400, 500 and 600 cm/s). Computed hemispherical flow contours scaled to true orifice flow (Qc/Qo) and scaled computed area to true orifice area (Ac/Ao) were plotted against distance from the orifice scaled to a circular orifice with equivalent orifice area. Results: Qc/Qo and Ac/Ao for each ellipse axis ratio when plotted against normalized orifice distance produced the same curves for each permutation of valve orifice area and max velocity. Plotting Qc/Qo (or Ac/Ao) against va/vo reveals marginal underestimation of flow with physiologic elliptical axis ratios of 2:1 and 3:1 against a circular orifice with axis ratios of 1:1 (Figure 1). Conclusions: The added error in using PISA to approximate flow through an elliptical mitral valve orifice area is minimal compared to traditional assumptions of a circular mitral valve orifice.


2014 ◽  
Vol 596 ◽  
pp. 27-31
Author(s):  
Jia Chen ◽  
Ji Feng Xing ◽  
Bang Jun Lv

A dimensionless nonlinear state-space model was established considering the structural particularities of digital hydraulic cylinder, and dynamic bifurcation characteristics of the system were analyzed and validated based on MATCONT. The results show that, when the piston diameter, valve orifice area gradient, ball-screw pitch and the maximum desired speed are not designed appropriately, digital hydraulic cylinder is prone to Hopf bifurcation. Limit cycles that the stable and the unstable neutralize each other at subcritical Hopf bifurcation points, causing the system tracking outputs divergence from continuous oscillation to increasing oscillation. Losing synchronism of stepper motor is essentially a form of the instability caused by system supercritical Hopf bifurcation.


2012 ◽  
Vol 5 (5) ◽  
pp. 478-483 ◽  
Author(s):  
Selim R. Krim ◽  
Rey P. Vivo ◽  
Ankit Patel ◽  
Jiaqiong Xu ◽  
Stephen R. Igo ◽  
...  

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