Pulsatile Performance of Two Valved Conduits Used as Cardiac Valve Replacements

Author(s):  
C R Gentle ◽  
S E Leefe

Pulsatile in vitro flow tests are reported on a Björk-Shiley conduit disc valve and a prototype ball valve conduit, both used as replacements for the aortic valve and ascending aorta. Comparison is made with a model of the aortic stenosis which the conduits would be used to replace. It is found that although the ball valve is considerably better than the disc valve, in terms of pressure drop and power loss for a given cardiac output, both prostheses offer large improvements on the stenotic situation.

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Hoda Maleki ◽  
Shahrokh Shahriari ◽  
Michel Labrosse ◽  
Philippe Pibarot ◽  
Lyes Kadem

A significant number of elderly patients with severe symptomatic aortic stenosis are denied surgical aortic valve replacement (SAVR) because of high operative risk. Transcatheter aortic valve implantation (TAVI) has emerged as a valid alternative to SAVR in these patients. One of the main characteristics of TAVI, when compared to SAVR, is that the diseased native aortic valve remains in place. For hemodynamic testing of new percutaneous valves and clinical training, one should rely on animal models. However, the development of an appropriate animal model of severe aortic stenosis is not straightforward. This work aims at developing and testing an elastic model of the ascending aorta including a severe aortic stenosis. The physical model was built based on a previous silicone model and tested experimentally in this study. Experimental results showed that the error between the computer-aided design (CAD) file and the physical elastic model was <5%, the compliance of the ascending aorta was 1.15 ml/mm Hg, the effective orifice area (EOA) of the stenotic valve was 0.86 cm2, the peak jet velocity was 4.9 m/s and mean transvalvular pressure gradient was 50 mm Hg, consistent with as severe. An EDWARDS-SAPIEN 26 mm valve was then implanted in the model leading to a significant increase in EOA (2.22 cm2) and a significant decrease in both peak jet velocity (1.29 m/s) and mean transvalvular pressure gradient (3.1 mm Hg). This model can be useful for preliminary in vitro testing of percutaneous valves before more extensive animal and in vivo tests.


2020 ◽  
Vol 21 (Supplement_1) ◽  
Author(s):  
A Ruocco ◽  
M Previtero ◽  
N Bettella ◽  
D Muraru ◽  
S Iliceto ◽  
...  

Abstract Clinical Presentation: a 18-year-old woman with Turner’s syndrome (TS), with history of hypothyroidism treated with L-thyroxin, asymptomatic moderately stenotic bicuspid aortic valve (AV) and without any known cardiovascular risk factor, was admitted to our emergency department (ED) because of syncope and typical chest pain after dinner associated with dyspnea. Chest pain lasted for an hour with spontaneous regression. In the ED the patient (pt) was normotensive. An ECG showed sinus rhythm (88 bpm), nonspecific repolarization anomalies (T wave inversion) in the inferior and anterior leads. Myocardial necrosis biomarkers were negative. A 3D transthoracic echocardiography showed normal biventricular systolic function with left ventricular hypertrophy, dilatation of the ascending aorta, unicuspid AV with severe aortic stenosis (peak/mean gradient 110/61 mmHg, aortic valve area 0,88 cm2-0,62 cm2/m2), mild pericardial effusion (Figure Panel A, B, C). Five days after, the pt had a new episode of typical chest pain without ECG changes. A computerized tomography (CT) was performed to rule out the hypothesis of aortic dissection and showed a dilation of the ascending aorta and pericardial effusion localized in the diaphragmatic wall, no signs of dissection or aortic hematoma. However, CT was of suboptimal quality because of sinus tachycardia (120 bpm) and so the pt underwent a coronary angiography and aortography that ruled out coronary disease, confirmed the dilatation of ascending aorta (50 mm) and showed images of penetrating atherosclerotic ulcer of the ascending aorta (Figure panel D). The pt underwent urgent transesophageal echocardiography (TOE) that confirmed the severely stenotic unicuspid AV and showed a localized type A aortic dissection (Figure Panel E, F, G). The pt underwent urgent AV and ascending aorta replacement (Figure Panel H). Learning points Chest pain and syncope are challenging symptoms in pts presenting in ED. AV pathology and aortic dissection should be always suspected and ruled out. TS is associated with multiple congenital cardiovascular abnormalities and is the most common established cause of aortic dissection in young women. 30% of Turner’s pts have congenitally AV abnormalities, and dilation of the ascending aorta is frequently associated. However, unicuspid AV is a very rare anomaly, usually stenotic at birth and requiring replacement. The presence of pericardial effusion in a pt with chest pain and syncope should raise the suspicion of aortic dissection, even if those symptoms usually accompany severe aortic stenosis. Even if CT is the gold standard imaging technique to rule out aortic dissection, the accuracy of a test is critically related to the image quality. When the suspicion of dissection is high and the reliability of the reference test is low, it’s reasonable to perform a different test to rule out the pathology. Aortography and TOE were pivotal to identify the limited dissection of the ascending aorta. Abstract P190 Figure.


Author(s):  
Ruihang Zhang ◽  
Yan Zhang

Abstract Aortic stenosis (AS) is one of the most common valvular heart diseases around the globe. The accurate assessment of AS severity is important and strongly associated with accurate interpretation of the hemodynamic parameters across the stenotic valve. In this study, we conducted in vitro fluid dynamic experiments to investigate the pulsatile flow characteristics of a stenotic aortic valve as a function of heart rate. An in vitro cardiovascular flow simulator was used to generate pulsatile flow with a prescribed waveform (40% systolic period and 4L/min cardiac output) under varied heart rates (50 bpm, 75 bpm and 100 bpm). The stenotic valve was constructed by molding silicone into three-leaflet aortic valve geometries wrapping around thin fabrics which increases its stiffness and tensile strength. Two-dimensional phase-locked particle image velocimetry (PIV) was employed to quantify the flow field characteristics of the stenotic valve. Pressure waveforms were recorded to evaluate the severity of the stenosis via the Gorlin and Hakki equations. Results suggest that as the heart rate increases, the peak pressure gradient across the stenotic aortic valve increases significantly under the same cardiac output. Analysis also shows the estimated aortic valve area (AVA) decreases as the heart rate increases under the same cardiac output using Gorlin equation estimation, while the trend is reversed using Hakki equation estimation. Under phase-locked conditions, quantitative flow characteristics, such as phase-averaged flow velocity, turbulence kinetic energy (TKE) for the stenotic aortic valve were analyzed based on the PIV data. Results suggest that the peak systolic jet velocity downstream of the valve increases as the heart rate increases, implying a longer pressure recovery distance as heart rate increases. While the turbulence at peak systole is higher under the slower heart rate, the faster heart rate contributes to a higher turbulence during the late systole and early diastole phases. Based on the comparison with no-valve cases, the differences in TKE was mainly related to the dynamics of leaflets under different heart rates. Overall, the results obtained in this study demonstrate that the hemodynamics of a stenotic aortic valve is complex and the assessment of AS could be significantly affected by the pulsating rate of the flow.


Author(s):  
Neelakantan Saikrishnan ◽  
Nicole C. Milligan ◽  
Ajit P. Yoganathan

In about 1–2% of all live births, the human aortic valve only consists of two anomalous leaflets and is known as the bicuspid aortic valve (BAV). BAVs are the most common congenital cardiac anomaly, and are associated with significant valvular dysfunction, including calcific aortic stenosis (AS) and aortic regurgitation (AR), as well as aortic wall abnormalities including coarctation of the aorta, ascending aortic dilatation and aneurysms [1]. Many studies have proposed a common underlying genetic defect in progression of complications with BAVs [2]. However, other recent studies have also suggested that the altered hemodynamic environment associated with BAVs could also be responsible for accelerated disease progression in these patients [3, 4]. A recent in vitro study showed elevated levels of turbulence associated with BAVs, and indicated that fluid flow patterns in the aortic sinuses are also affected due to the altered valve morphology [5]. The present work seeks to compare the levels of turbulence in BAVs to pure trileaflet aortic stenosis models.


2019 ◽  
Vol 10 (5) ◽  
pp. 624-627
Author(s):  
Jeremy L. Herrmann ◽  
Amanda R. Stram ◽  
John W. Brown

Prosthesis choice for aortic valve replacement (AVR) in children is frequently compromised by unavailability of prostheses in very small sizes, the lack of prosthetic valve growth, and risks associated with long-term anticoagulation. The Ross procedure with pulmonary valve autograft offers several advantages for pediatric and adult patients. We describe our current Ross AVR technique including replacement of the ascending aorta with a prosthetic graft. The procedure shown in the video involves an adult-sized male with a bicuspid aortic valve, mixed aortic stenosis and insufficiency, and a dilated ascending aorta.


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