Hemodynamic Assessment of Aortic Stenosis

Fluid Structure Interaction on Paravalvular Leakage of Transcatheter Aortic Valve Implantation Related to Aortic Stenosis: A Patient-Specific Case

This study investigated the impact of paravalvular leakage (PVL) in relation to the different valve openings of the transcatheter aortic valve implantation (TAVI) valve using the fluid structure interaction (FSI) approach. Limited studies were found on the subject of FSI with regards to TAVI-PVL condition, which involves both fluid and structural responses in coupling interaction. Hence, further FSI simulation with the two-way coupling method is implemented to investigate the effects of hemodynamics blood flow along the patient-specific aorta model subjected to the interrelationship between PVL and the different valve openings using the established FSI software ANSYS 16.1. A 3D patient-specific aorta model is constructed using MIMICS software. The TAVI valve identical to Edward SAPIEN XT 26 (Edwards Lifesciences, Irvine, California), at different Geometrical Orifice Areas (GOAs), is implanted into the patient's aortic annulus. The leaflet opening of the TAVI valve is drawn according to severity of GOA opening represented in terms of 100%, 80%, 60%, and 40% opening, respectively. The result proved that the smallest percentage of GOA opening produced the highest possibility of PVL, increased the recirculatory flow proximally to the inner wall of the ascending aorta, and produced lower backflow velocity streamlines through the side area of PVL region. Overall, 40% GOA produced 89.17% increment of maximum velocity magnitude, 19.97% of pressure drop, 65.70% of maximum WSS magnitude, and a decrement of 33.62% total displacement magnitude with respect to the 100% GOA.

Moderate Aortic Stenosis and Coronary Artery Bypass Grafting: Clinical Update for the Perioperative Echocardiographer

Incidental aortic stenosis in the setting of coronary artery bypass surgery may be a perioperative challenge. The accurate assessment of the degree of aortic stenosis remains an important determinant. Although severe aortic stenosis is an indication for valve replacement, current guidelines advise a balanced approach to the management of moderate aortic stenosis in this setting. Multiple factors should be considered in a team discussion to balance risks versus benefits for the various management options in the given patient. The rapid progress in aortic valve technologies also offer alternatives for definitive management of moderate aortic stenosis in this setting that will likely become even safer in the near future.

TAVI 2012: state of the art

The development of "transcatheter aortic valve implantation (TAVI)" is changing the field of cardiovascular medicine rapidly. The basic principle of TAVI is the percutaneous implantation of a bioprosthesis mounted in a metal frame. The prosthesis, which is attached to the tip of the catheter, is positioned in the native aortic valve and expanded. The first successful implantation was made by Alain Cribier in 2002. Several smaller mono- and multicenter studies later confirmed the technical feasibility of this procedure. Its true value as an important, therapeutic alternative to open heart surgery in inoperable and high-risk patients is now confirmed in large multicenter registries and by the prospective, randomized PARTNER trial. Decisive for the future acceptance of the procedure and for a possible expansion of the indication spectrum will be (1) continuous further development of the implantation technique and the prosthesis design, (2) reduction of TAVI-associated complications, (3) confirmation of the initial positive long-term results and (4) confirmation of the promising results in the treatment of surgical prosthesis dysfunctions and of patients with low to intermediate risk.

Computational analysis of an aortic valve jet with Lagrangian coherent structures

Important progress has been achieved in recent years in simulating the fluid-structure interaction around cardiac valves. An important step in making these computational tools useful to clinical practice is the development of postprocessing techniques to extract clinically relevant information from these simulations. This work focuses on flow through the aortic valve and illustrates how the computation of Lagrangian coherent structures can be used to improve insight into the transport mechanics of the flow downstream of the valve, toward the goal of aiding clinical decision making and the understanding of pathophysiology.

Optimum management of elderly patients with calcified aortic stenosis

Increased life-expectancy has led to a growing elderly population frequently presenting with aortic stenosis. This review focuses on the pathogenesis of calcific aortic stenosis, diagnosis and possible ways to halt the progression to severe symptomatic aortic stenosis, methods of assessing symptoms and severity, and modalities and timing of aortic valve replacement. At present the treatment of aortic stenosis for the majority of patients is surgical, and any patient with symptomatic severe aortic stenosis should be considered for aortic valve replacement. This article also discusses the role of emerging techniques of closed heart valve implantation either transfemoral or transapical, and which patients might be candidates for these new approaches to the treatment of aortic stenosis in the elderly population.

Assessing aortic valve area in aortic stenosis by continuity equation: a novel approach using real-time three-dimensional echocardiography

AIMS

Two-dimensional echocardiographic (2DE) continuity-equation derived aortic valve area (AVA) in aortic stenosis (AS) relies on non-simultaneous measurement of left ventricular outflow tract (LVOT) velocity and geometric assumptions of LVOT area, which can amplify error, especially in upper septal hypertrophy (USH). We hypothesized that real-time three-dimensional echocardiography (RT3DE) can improve accuracy of AVA by directly measuring LVOT stroke volume (SV) in one window.

METHODS AND RESULTS

RT3DE colour Doppler and 2DE were acquired in 68 AS patients (74 +/- 12 yrs) prospectively. SV was derived from flow obtained from a sampling curve placed orthogonal to LVOT (Tomtec Imaging). Agreement between continuity-equation derived AVA by RT3DE (AVA(3D-SV)) and 2DE (AVA(2D)) and predictors of discrepancies were analysed. Validation of LVOT SV was performed by aortic flow probe in a sheep model with balloon inflation of septum to mimic USH. There was only modest correlation between AVA(2D) and AVA(3D-SV) (r = 0.71, difference 0.11 +/- 0.23 cm(2)). The degree of USH was significantly associated with difference in AVA calculation (r = 0.4, P = 0.005). In experimentally distorted LVOT geometry in sheep, RT3DE correlated better with flow probe assessment (r = 0.96, P < 0.001) than 2DE (r = 0.71, P = 0.006).

CONCLUSION

RT3DE colour Doppler-derived LVOT SV in the calculation of AVA by continuity equation is more accurate than 2D, including in situations such as USH, common in the elderly, which modify LVOT geometry.