Objective: To compare the opening mechanics of porcine valve substitutes with those of a normal human aortic valve. Background: All commercially available porcine valves are pretreated with glutaraldehyde. This study was undertaken to evaluate the consequences of such treatment on valve mechanics. Methods: The opening mechanics of the aortic valve, especially the time taken to open fully from a closed position, and the duration for which the valve is maximally open, were compared in a normal aortic valve, a stent-mounted porcine valve, and a stentless porcine valve, using a finite element model. Results: Despite a 4-fold higher gradient, stent-mounted porcine valves were slower in attaining the fully open position, and the time for which the valve was fully open was almost 25% less than a normal valve. In stentless valves, the compliant root made the initial opening mechanics similar to those of a normal valve. Once this effect was over, the effect of porcine leaflet properties took over, and there was a corresponding delay in the valve opening. Conclusions: Fixing the root with a stent and stiffening the leaflets with glutaraldehyde result in delayed valve opening and decrease the duration for which the valve is fully open, thus contributing to inferior hemodynamics. © 2012 The Author(s).

Ramarathnam Krishna Kumar

Department of Engineering Design

glutaraldehyde

AORTA VALVE

article

biomechanics

BIOPROSTHESIS

Computer simulation

finite element analysis

HEART HEMODYNAMICS

nonhuman

Swine

SYSTOLE

AORTIC VALVE

Animals

FIXATIVES

GLUTARAL

HEART VALVE PROSTHESIS

Hemodynamics

Humans

materials testing

Models, Cardiovascular

Prosthesis Design

Time Factors

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Normal aortic valves stay open much longer in systole than porcine substitutes

Asian Cardiovascular and Thoracic Annals

Comparative study among aortic valves requires the use of an unbiased and relevant boundary condition. Pressure and flow boundary conditions used in literature are not sufficient for an unbiased analysis. We need a different boundary condition to analyze the valves in an unbiased, relevant environment. The proposed boundary condition is a combination of the pressure and flow boundary condition methods, which is chosen considering the demerits of the pressure and flow boundary conditions. In order to study the valve in its natural environment and to give a comparative analysis between different boundary conditions, a fluid-structure interaction analysis is made using the pressure and the proposed boundary conditions for a normal aortic valve. Commercial software LS-DYNA is used in all our analysis. The proposed boundary condition ensures a full opening of the valve with reduced valve regurgitation. It is found that for a very marginal raise in the ventricular pressure caused by pumping a fixed stroke volume, the cardiac output is considerably raised. The mechanics of the valve is similar between these two boundary conditions, however we observe that the importance of the root to raise the cardiac output may be overstated, considering the importance of the fully open nodule of arantius. Our proposed boundary condition delivers all the insights offered by the pressure and flow boundary conditions, along with providing an unbiased framework for the analysis of different valves and hence, more suitable for comparative analysis. © 2015 Elsevier Ltd.

Journal of Biomechanics

Aortic valve dynamics using a fluid structure interaction model - The physiology of opening and closing

Background. The major aim of this study was to examine the leaflet/aortic root interaction during the cardiac cycle, including the stresses developed during the interaction. Methods. Dynamic finite element analysis was used along with a geometrically accurate model of the aortic valve and the sinuses. Shell elements along with proper contact conditions were also used in the model. Pressure patterns during the cardiac cycle were given as an input, and a linear elastic model was assumed for the material. Results. We found that aortic root dilation starts before the opening of the leaflet and is substantial by the time leaflet opens. Dilation of the root alone helps in opening the leaflet to about 20%. The equivalent stress pattern shows an instantaneous increase in stress at the coaptation surface during closure. Stresses increase as the point of attachment is approached from the free surface. Conclusions. The complex interplay of the geometry of the valve system can be effectively analyzed using a sophisticated dynamic finite element model. Results not previously brought out by the earlier static analysis shed new light on the root/valve interaction. © 2002 by The Society of Thoracic Surgeons.

Annals of Thoracic Surgery

Dynamic analysis of the aortic valve using a finite element model

European Heart Journal

Stentless vs. stented aortic valve bioprostheses: a prospective randomized controlled trial

The Annals of Thoracic Surgery

Root Replacement Using Stentless Valves in the Small Aortic Root: A Propensity Score Analysis

The Journal of Thoracic and Cardiovascular Surgery

Stentless bioprostheses improve postoperative coronary flow more than stented prostheses after valve replacement for aortic stenosis

Stentless Aortic Valves are Hemodynamically Superior to Stented Valves During Mid-Term Follow-Up: A Large Retrospective Study

Journal	Asian Cardiovascular and Thoracic Annals
ISSN	02184923
Open Access	No