Hemodynamic performance evaluation of neonatal ECMO double lumen cannula using fluid-structure interaction

Extra corporeal membrane oxygenation (ECMO) is an artificial oxygenation facility, employed in situations of cardio-pulmonary failure. Some diseases i.e., acute respiratory distress syndrome, pulmonary hypertension, corona virus disease (COVID-19) etc. affect oxygenation performance of the lungs thus requiring the need of artificial oxygenation. Critical care teams used ECMO technique during the COVID-19 pandemic to support the heart and lungs of COVID-19 patients who had an acute respiratory or cardiac failure. Double Lumen Cannula (DLC) is one of the most critical components of ECMO as it resides inside the patient and, connects patient with external oxygenation circuit. DLC facilitates delivery and drainage of blood from the patient's body. DLC is characterized by delicate balance of internal and external flows inside a limited space of the right atrium (RA). An optimal performance of the DLC necessitates structural stability under biological and hemodynamic loads, a fact that has been overlooked by previously published studies. In the past, many researchers experimentally and computationally investigated the hemodynamic performance of DLC by employing Eulerian approach, which evaluate instantaneous blood damage without considering blood shear exposure history (qualitative assessment only). The present study is an attempt to address the aforementioned limitations of the previous studies by employing Lagrangian (quantitative assessment) and incorporating the effect of fluid-structure interaction (FSI) to study the hemodynamic performance of neonatal DLC. The study was performed by solving three-dimensional continuity, momentum, and structural mechanics equation(s) by numerical methods for the blood flow through neonatal DLC. A two-way coupled FSI analysis was performed to analyze the effect of DLC structural deformation on its hemodynamic performance. Results show that the return lumen was the most critical section with maximum pressure drop, velocity, shear stresses, and blood damage. Recirculation and residence time of blood in the right atrium (RA) increases with increasing blood flow rates. Considering the structural deformation has led to higher blood damage inside the DLC-atrium system. Maximum Von-Mises stress was present on the side edges of the return lumen that showed direct proportionality with the blood flow rate.

The hemodynamic performance of balloon-expandable aortic bioprostheses in the elderly: a comparison between rapid deployment and transcatheter implantation

BACKGROUND

Surgical aortic valve replacement with a rapid deployment valve (RDV) is a relatively recent treatment option. Aim of this study was to compare the hemodynamic performance of balloon-expandable (BE)-RDVs and BE-transcatheter heart valves (THVs) in a high surgical risk and frail-elderly population.

METHODS

BE-THVs and BE-RDVs were respectively implanted in 138 and 47 patients, all older than 75 years and with a Canadian Study of Health and Aging category of 5 or above. Echocardiographic assessment was performed at discharge and at six months.

RESULTS

At discharge, transprosthetic pressure gradients and indexed effective orifice area (iEOA) were similar in both cohorts. At six-month follow-up, BE-RDV showed lower peak (14.69 vs 20.86 mmHg; p <0.001) and mean (7.82 vs 11.83 mmHg; p <0.001) gradients, as well as larger iEOA (1.05 vs 0.84 cm²/m²; p <0.001). Similar findings were also shown considering only small sized valves. Moderate-to-severe paravalvular leakage was more prevalent in BE-THVs at discharge (14.49 vs 0.00%; p=0.032) and, considering exclusively small prostheses, at six months too (57.69 vs 15.00%; p=0.014). Nevertheless, BE-THVs determined amelioration in left ventricular ejection fraction (53.79 vs 60.14%; p <0.001), pulmonary artery systolic pressure (35.81 vs 33.15 mmHg; p=0.042) and tricuspid regurgitation severity (40.58 vs 19.57%; p=0.031) from discharge to mid-term follow-up.

CONCLUSIONS

BE-RDVs showed better hemodynamic performance, especially when implanted in small annulus. Despite their worse baseline conditions, transcatheter patients still exhibited a greater improvement of their echocardiographic profile at mid-term follow-up.

Two-Year Clinical Follow-Up Assessment of the Novel Cingular Surgical Bovine Pericardial Valve

Objectives: To evaluate the 2-year clinical safety and hemodynamic outcomes of the Cingular bovine pericardial bioprosthesis. Methods: A prospective, multicenter, single-arm trial was conducted in patients who required aortic or mitral valve replacement. From March 2016 to October 2017, 197 patients were implanted with the Cingular bovine pericardial valve at five sites in China. The clinical outcomes and hemodynamic performance were assessed through a 2-year follow-up. Clinical safety events were reviewed by an independent clinical events committee, and echocardiographic data were assessed by an independent core laboratory. Results: The mean age was 66.9 ± 4.9 years. The 2-year survival rate was 96.4%. A complete 2-year clinical follow-up was achieved in 189 of 190 survivors. No case of structural valve deterioration, major perivalvular leak, prosthetic valve endocarditis, or valve-related reoperation was seen. For the aortic valve, the mean pressure gradient observed was 12.5 ± 4.0 mm Hg, and the effective orifice area (EOA) was 2.0 ± 0.3 cm2. For the smaller size aortic valves, 19 mm and 21 mm, respective mean EOA values of 1.7 ± 0.2 cm2 and 1.8 ± 0.2 cm2 were found. The values for mean pressure gradient and mean EOA for mitral bioprostheses were 4.0 ± 1.4 mm Hg and 2.2 ± 0.3 cm2, respectively. There was no significant change between 1-year and 2-year hemodynamic performance. Conclusions: The Cingular bovine pericardial valve showed favorable clinical safety and hemodynamic outcomes over a 2-year follow-up. Further follow-up is required to validate the long-term durability.

Effects of a Short-Term Left Ventricular Assist Device on Hemodynamics in a Heart Failure Patient-Specific Aorta Model: A CFD Study

Patients with heart failure (HF) or undergoing cardiogenic shock and percutaneous coronary intervention require short-term cardiac support. Short-term cardiac support using a left ventricular assist device (LVAD) alters the pressure and flows of the vasculature by enhancing perfusion and improving the hemodynamic performance for the HF patients. However, due to the position of the inflow and outflow of the LVAD, the local hemodynamics within the aorta is altered with the LVAD support. Specifically, blood velocity, wall shear stress, and pressure difference are altered within the aorta. In this study, computational fluid dynamics (CFD) was used to elucidate the effects of a short-term LVAD for hemodynamic performance in a patient-specific aorta model. The three-dimensional (3D) geometric models of a patient-specific aorta and a short-term LVAD, Impella CP, were created. Velocity, wall shear stress, and pressure difference in the patient-specific aorta model with the Impella CP assistance were calculated and compared with the baseline values of the aorta without Impella CP support. Impella CP support augmented cardiac output, blood velocity, wall shear stress, and pressure difference in the aorta. The proposed CFD study could analyze the quantitative changes in the important hemodynamic parameters while considering the effects of Impella CP, and provide a scientific basis for further predicting and assessing the effects of these hemodynamic signals on the aorta.

The Comparison of Different Constitutive Laws and Fiber Architectures for the Aortic Valve on Fluid-Structure Interaction Simulation

Built on the hybrid immersed boundary/finite element (IB/FE) method, fluid-structure interaction (FSI) simulations of aortic valve (AV) dynamics are performed with three different constitutive laws and two different fiber architectures for the AV leaflets. An idealized AV model is used and mounted in a straight tube, and a three-element Windkessel model is further attached to the aorta. After obtaining ex vivo biaxial tensile testing of porcine AV leaflets, we first determine the constitutive parameters of the selected three constitutive laws by matching the analytical stretch-stress relations derived from constitutive laws to the experimentally measured data. Both the average error and relevant R-squared value reveal that the anisotropic non-linear constitutive law with exponential terms for both the fiber and cross-fiber directions could be more suitable for characterizing the mechanical behaviors of the AV leaflets. We then thoroughly compare the simulation results from both structural mechanics and hemodynamics. Compared to the other two constitutive laws, the anisotropic non-linear constitutive law with exponential terms for both the fiber and cross-fiber directions shows the larger leaflet displacements at the opened state, the largest forward jet flow, the smaller regurgitant flow. We further analyze hemodynamic parameters of the six different cases, including the regurgitant fraction, the mean transvalvular pressure gradient, the effective orifice area, and the energy loss of the left ventricle. We find that the fiber architecture with body-fitted orientation shows better dynamic behaviors in the leaflets, especially with the constitutive law using exponential terms for both the fiber and cross-fiber directions. In conclusion, both constitutive laws and fiber architectures can affect AV dynamics. Our results further suggest that the strain energy function with exponential terms for both the fiber and cross-fiber directions could be more suitable for describing the AV leaflet mechanical behaviors. Future experimental studies are needed to identify competent constitutive laws for the AV leaflets and their associated fiber orientations with controlled experiments. Although limitations exist in the present AV model, our results provide important information for selecting appropriate constitutive laws and fiber architectures when modeling AV dynamics.

Three-dimensional ophthalmic artery model reconstruction and assessment captured by computed tomographic angiography in non-arteritic anterior ischemic optic neuropathy patients

Background

The ophthalmic artery (OA) was first reconstructed using computer software. The structural differences of ophthalmic arteries in non-arteritic anterior ischemic optic neuropathy (NAION) and normal eyes, in addition to hemodynamic alterations, were assessed.

Methods

Thirty-one NAION eyes, 19 uninvolved eyes with NAION, and a control group of 26 healthy eyes were retrospectively included. Computed tomographic angiography data were recorded, and corresponding three-dimensional OA models were constructed. Initial OA and internal carotid artery (ICA) diameters and the angle between them were analyzed. Three different OA models were used to evaluate hemodynamic performance. The statistical relationships between the initial diameters of the OA and ICA and the angle between the OA and ICA were described.

Results

OA diameters in NAION eyes were significantly smaller than those in both uninvolved and healthy eyes (P<0.05). There was no significant difference between uninvolved and healthy eyes (P=0.31). The initial ICA diameter and the angle between the OA and ICA did not significantly differ among the three groups. In the three models, the blood flow velocity in the initial ophthalmic arteries of uninvolved eyes was higher than that in the NAION eyes. The mass flows of the right and left ophthalmic arteries, accounting for the ipsilateral ICA in the control model, were 0.57%. However, these values in uninvolved and NAION eyes were 1.36% and 0.25%, respectively.

Conclusions

NAION is associated with a smaller initial OA diameter, which may be related to hypoperfusion. To our knowledge, this is the first pilot study to analyze hemodynamic alterations using OA models.

Implantation and 30-Day Follow-Up on All 4 Valve Sizes Within the Portico Transcatheter Aortic Bioprosthetic Family

OBJECTIVES

The aim of this study was to evaluate the short-term safety and performance of the full range of valve sizes offered within the Portico transcatheter aortic valve replacement system.

BACKGROUND

The Portico transcatheter aortic heart valve is a fully resheathable, repositionable, and self-expanding bioprosthesis designed to achieve optimal valve position and hemodynamic performance and limit conduction disturbances.

METHODS

Patients (n = 222) with symptomatic (New York Heart Association functional class ≥II) severe aortic stenosis considered by a multidisciplinary heart team to be at high surgical risk were recruited between December 2011 and September 2015 in this prospective, nonrandomized, multicenter study. Patients were implanted with the full range of Portico heart valves (23, 25, 27, and 29 mm) using the transfemoral approach. The primary endpoint was all-cause mortality at 30 days. Secondary endpoints included valve performance, improvement in functional class, and procedural outcomes as defined by Valve Academic Research Consortium criteria.

RESULTS

A total of 220 patients (mean age 83.0 ± 4.6 years, 74.3% women, mean Society of Thoracic Surgeons score 5.8%) had valves implanted. All resheathing and repositioning attempts (n = 72) were successful. At 30 days, all-cause mortality was 3.6%. Procedural outcomes included disabling (major) stroke (3.2%), major vascular complications (7.2%), and permanent pacemaker implantation (13.5%). Compared with baseline, 75.8% of patients improved by ≥1 New York Heart Association functional class at 30 days. The rate of moderate paravalvular leak was 5.7%, with no severe paravalvular leak reported. No differences in paravalvular leak incidence and severity were observed among valve sizes (p = 0.24).

CONCLUSIONS

Across all valve sizes, use of the repositionable Portico transcatheter aortic valve replacement system resulted in safe and effective treatment of aortic stenosis in high-risk patients.