DIASTOLIC OPENING OF THE AORTIC VALVE (AV) IN A CASE OF AORTIC INSUFFICIENCY DUE TO AV FENESTRATION

A patient with severe aortic insufficiency due to fenestration of the non-coronary aortic valve leaflet is described. A preoperative echocardiogram demonstrated early closure of the mitral valve and early diastolic separation of the aortic valve leaflets. These findings disappeared after partial surgical correction and subsequent hemodynamic improvement. Premature opening of the aortic valve is common in severe aortic insufficiency.     

Quadricuspid aortic valve: intraoperative transesophageal echocardiograph image

Quadricuspid aortic valve is an extremely rare congenital anomaly. In Quadricuspid aortic valve, the aortic valve has four distinct leaflets. The most common type A variant has four equal cusps. The most common presentation is aortic insufficiency. A 70-year-old woman and a 32-year-old man presented to our practice in a 3-month time span were described here.     

Systolic fluid–structure interaction model of the congenitally bicuspid aortic valve: assessment of modelling requirements

A transient fluid–structure interaction (FSI) model of a congenitally bicuspid aortic valve has been developed which allows simultaneous calculation of fluid flow and structural deformation. The valve is modelled during the systolic phase (the stage when blood pressure is elevated within the heart to pump blood to the body). The geometry was simplified to represent the bicuspid aortic valve in two dimensions. A congenital bicuspid valve is compared within the aortic root only and within the aortic arch. Symmetric and asymmetric cusps were simulated, along with differences in mechanical properties. A moving arbitrary Lagrange–Euler mesh was used to allow FSI. The FSI model requires blood flow to induce valve opening and induced strains in the region of 10%. It was determined that bicuspid aortic valve simulations required the inclusion of the ascending aorta and aortic arch. The flow patterns developed were sensitive to cusp asymmetry and differences in mechanical properties. Stiffening of the valve amplified peak velocities, and recirculation which developed in the ascending aorta. Model predictions demonstrate the need to take into account the category, including any existing cusp asymmetry, of a congenital bicuspid aortic valve when simulating its fluid flow and mechanics.     

Two-dimensional color-mapping of turbulent shear stress distribution downstream of two aortic bioprosthetic valves in vitro.

Since artificial heart valve related complications such as thrombus formation, hemolysis and calcification are considered related to flow disturbances caused by the inserted valve, a thorough hemodynamic characterization of heart valve prostheses is essential. In a pulsatile flow model, fluid velocities were measured one diameter downstream of a Hancock Porcine (HAPO) and a Ionescu-Shiley Pericardial Standard (ISPS) aortic valve. Hot-film anemometry (HFA) was used for velocity measurements at 41 points in the cross-sectional area of the ascending aorta. Three-dimensional visualization of the velocity profiles, at 100 different instants during one mean pump cycle, was performed. Turbulence analysis was performed as a function of time by calculating the axial turbulence energy within 50 ms overlapping time windows during the systole. The turbulent shear stresses were estimated by using the correlation equation between Reynolds normal stress and turbulent (Reynolds) shear stress. The turbulent shear stress distribution was visualized by two-dimensional color-mapping at different instants during one mean pump cycle. Based on the velocity profiles and the turbulent shear stress distribution, a relative blood damage index (RBDI) was calculated. It has the feature of combining the magnitude and exposure time of the estimated shear stresses in one index, covering the entire cross-sectional area. The HAPO valve showed a skewed jet-type velocity profile with the highest velocities towards the left posterior aortic wall. The ISPS valve revealed a more parabolic-shaped velocity profile during systole. The turbulent shear stresses were highest in areas of high or rapidly changing velocity gradients. For the HAPO valve the maximum estimated turbulent shear stress was 194 N m-2 and for the ISPS valve 154 Nm-2. The RBDI was the same for the two valves. The turbulent shear stresses had magnitudes and exposure times that might cause endothelial damage and sublethal or lethal damage to blood corpuscules. The RBDI makes comparison between different heart valves easier and may prove important when making correlation with clinical observations.     

Prolapse of noncoronary aortic cusp with severe aortic regurgitation after a tear of the aortic root

A patient with acute aortic regurgitation, a dissecting aneurysm with a localized transverse tear just above the aortic valve, and an aortic noncoronary cusp eversion is discussed. The valvular defects were considered to be of recent etiology, and the patient underwent successful aortic valve replacement and repair of the dissection.     

Geometric modeling of functional trileaflet aortic valves: development and clinical applications

The dimensions of the aortic valve components condition its ability to prevent blood from flowing back into the heart. While the theoretical parameters for best trileaflet valve performance have already been established, an effective approach to describe other less optimal, but functional models has been lacking. Our goal was to establish a method to determine by how much the dimensions of the aortic valve components can vary while still maintaining proper function. Measurements were made on silicone rubber casts of human aortic valves to document the range of dimensional variability encountered in normal adult valves. Analytical equations were written to describe a fully three-dimensional geometric model of a trileaflet valve in both the open and closed positions. A complete set of analytical, numerical and graphical tools was developed to explore a range of component dimensions within functional aortic valves. A list of geometric guidelines was established to ensure safe operation of the valve during the cardiac cycle, with practical safety margins. The geometry-based model presented here allows determining quickly if a certain set of valve component dimensions results in a functional valve. This is of great interest to designers of new prosthetic heart valve models, as well as to surgeons involved in valve-sparing surgery.     

Estimation of turbulent shear stresses in pulsatile flow immediately downstream of two artificial aortic valves in vitro

Measuring turbulent shear stresses is of major importance in artificial heart valve evaluation. Bi- and unidirectional fluid velocity measurements enable calculation of Reynolds shear stress ( ) and Reynolds normal stress ( ). τ is important due to the relation to hemolysis and thrombus formation, but σ is the only obtainable parameter in vivo. Therefore, determination of a correlation factor between τ and σ is pertinent.In a pulsatile flow model, laser Doppler (LDA) and hot-film (HFA) anemometry were used for simultaneous bi- and unidirectional fluid velocity measurements downstream of a Hall Kaster and a Hancock Porcine aortic valve. Velocities were registered in two flow field locations and at four cardiac outputs. The velocity signals were subjected to analog signal processing prior to digital turbulence analysis, as a basis for calculation of τ and σ.A correlation factor of 0.5 with a correlation coefficient of 0.97 was found between the maximum Reynolds shear stress and Reynolds normal stress, implying . In vitro estimation of turbulent shear stresses downstream of artificial aortic valves, based on the axial velocity component alone, seems possible.     

Estimation of turbulent shear stresses in pulsatile flow immediately downstream of two artificial aortic valves in vitro

Measuring turbulent shear stresses is of major importance in artificial heart valve evaluation. Bi- and unidirectional fluid velocity measurements enable calculation of Reynolds shear stress ( ) and Reynolds normal stress ( ). τ is important due to the relation to hemolysis and thrombus formation, but σ is the only obtainable parameter in vivo. Therefore, determination of a correlation factor between τ and σ is pertinent.

In a pulsatile flow model, laser Doppler (LDA) and hot-film (HFA) anemometry were used for simultaneous bi- and unidirectional fluid velocity measurements downstream of a Hall Kaster and a Hancock Porcine aortic valve. Velocities were registered in two flow field locations and at four cardiac outputs. The velocity signals were subjected to analog signal processing prior to digital turbulence analysis, as a basis for calculation of τ and σ.

A correlation factor of 0.5 with a correlation coefficient of 0.97 was found between the maximum Reynolds shear stress and Reynolds normal stress, implying . In vitro estimation of turbulent shear stresses downstream of artificial aortic valves, based on the axial velocity component alone, seems possible.     

Bicuspid stenotic aortic valves: clinical characteristics and morphological assessment using MRI and echocardiography

Background

Bicuspid aortic valve (BAV) is one of the most common congenital heart defects with a population prevalence of 0.5% to 1.3%. Identifying patients with BAV is clinically relevant because BAV is associated with aortic stenosis, endocarditis and ascending aorta pathology.

Methods and Results

Patients with severe aortic stenosis necessitating aortic valve replacement surgery were included in this study. All dissected aortic valves were stored in the biobank of the University Medical Centre Utrecht. Additionally to the morphological assessment of the aortic valve by the surgeon and pathologist, echocardiographic and magnetic resonance imaging (MRI) images were evaluated. A total of 80 patients were included of whom 32 (40%) were diagnosed with BAV by the surgeon (gold standard). Patients with BAV were significantly younger (55 vs 71 years) and were more frequently male. Notably, a significant difference was found between the surgeon and pathologist in determining valve morphology. MRI was performed in 33% of patients. MRI could assess valve morphology in 96% vs 73% with echocardiography. The sensitivity of MRI for BAV in a population of patients with severe aortic stenosis was higher than echocardiography (75% vs 55%), whereas specificity was better with the latter (91% vs 79%). Typically, the ascending aorta was larger in patients with BAV.

Conclusion

Among unselected patients with severe aortic valve stenosis, a high percentage of patients with BAV were found. Imaging and assessment of the aortic valve morphology when stenotic is challenging.     

An approach to the simulation of fluid-structure interaction in the aortic valve

A pair of finite element models has been employed to study the interaction of blood flow with the operation of the aortic valve. A three-dimensional model of the left ventricle with applied wall displacements has been used to generate data for the spatially and time-varying blood velocity profile across the aortic aperture. These data have been used as the inlet loading conditions in a three-dimensional model of the aortic valve and its surrounding structures. Both models involve fluid-structure interaction and simulate the cardiac cycle as a dynamic event. Confidence in the models was obtained by comparison with data obtained in a pulse duplicator. The results show a circulatory flow being generated in the ventricle which produces a substantially axial flow through the aortic aperture. The aortic valve behaves in an essentially symmetric way under the action of this flow, so that the pressure difference across the leaflets is approximately uniform. This work supports the use of spatially uniform but temporally variable pressure distributions across the leaflets in dry or structural models of aortic valves. The study is a major advance through its use of truly three-dimensional geometry, spatially non-uniform loading conditions for the valve leaflets and the successful modelling of progressive contact of the leaflets in a fluid environment.     

A novel heart valve stent design: mechanical interaction with the aortic root

Percutaneous aortic valve implantation has become an alternative technique to surgical valve replacement in patients with high risk for open chest surgery. Vascular stents clinically used today for non-invasive aortic valve replacement tend, however, to impede the dimension changes of the compliant aortic root over the cardiac cycle. The purpose of the present work is to assess the influence of a novel heart valve stent, designed specifically to limit the traumatism in tissue, on the compliance of the aortic root. A theoretical approach is adopted to model the mechanical behaviour of the different stent parts and assess the compliance modification induced by the stent. The validity of the model is then tested experimentally. Both approaches show that the specific geometry of the stent makes it possible to keep the compliance of the aortic root close to the native root values.     

Management of a protruding right coronary artery stent during aortic valve replacement for aortic stenosis

ABSTRACT: We describe the successful management of a stent protruding from the right coronary ostium into the aortic root in the setting of aortic valve replacement for aortic stenosis. Due to advances in medical care more elderly patients present for aortic valve surgery after percutaneous coronary intervention. Therefore, with an aging population due to advances in medical care, more patients will present for aortic valve surgery after percutaneous coronary intervention. We suggest a degree of caution before valve deployment in transcatheter aortic valve intervention or during annular manipulation in patients undergoing traditional aortic valve replacement with coexisting patent proximal stents.     

Cardiologist and cardiac surgeon view on decision-making in prosthetic aortic valve selection: does profession matter?

Aims

Assess and compare among Dutch cardiothoracic surgeons and cardiologists: opinion on (1) patient involvement, (2) conveying risk in aortic valve selection, and (3) aortic valve preferences.

Methods and results

A survey among 117 cardiothoracic surgeons and cardiologists was conducted. Group responses were compared using the Mann–Whitney U test. Most respondents agreed that patients should be involved in decision-making, with surgeons leaning more toward patient involvement (always: 83 % versus 50 % respectively; p?<?0.01) than cardiologists. Most respondents found that ideally doctors and patients should decide together, with cardiologists leaning more toward taking the lead compared with surgeons (p?<?0.01). Major risks of the therapeutic options were usually discussed with patients, and less common complications to a lesser extent. A wide variation in valve preference was noted with cardiologists leaning more toward mechanical prostheses, while surgeons more often preferred bioprostheses (p?<?0.05).

Conclusion

Patient involvement and conveying risk in aortic valve selection is considered important by cardiologists and cardiothoracic surgeons. The medical profession influences attitude with regard to aortic valve selection and patient involvement, and preference for a valve substitute. The variation in valve preference suggests that in most patients both valve types are suitable and aortic valve selection may benefit from evidence-based informed shared decision-making.     

A numerical analysis of the backflow between the leaflets of a St Jude Medical cardiac valve prosthesis

Clinically significant, unexplained hemolysis has been reported to occur in St Jude Medical (SJM) cardiac valve prostheses. The leakage phase of backflow is identified as having the most hemolytic potential, when compared with the other phases of the cardiac cycle. A two-dimensional, laminar, constant fluid property finite element analysis (FEA) is used to calculate the peak shear stress obtained in the flow through the narrow slit formed by the closed leaflets of an idealized size 29 mm (tissue annulus diameter) SJM cardiac valve prosthesis, during the leakage phase of backflow. The flow geometry was such that the simple laminar flow theory (SLFT) could be used to model the flow through the region of peak shear stresses with reasonable accuracy. The SLFT predicts that the maximum shear stress depends upon the thickness of the clearance space and the average velocity through that space. These results suggest that the magnitude of the peak shear stress is of the order of 700-1000 Pa for a duration of the order of 0.5-0.4 ms for pressure drops across the valve of 150-300 torr. This suggests that hemolysis is possible for certain unfortunate combinations of clearances and pressure conditions. However, further research is needed before this flow phenomenon can be associated with the reported clinical hemolysis.     

The Role of Rubella in the Etiology of Supravalvular Aortic Stenosis

The possibility of an etiological relationship between rubella embryopathy and sporadic forms of supravalvular aortic stenosis is considered. A case is presented of a patient with rubella embryopathy and supravalvular aortic stenosis associated with pulmonary valvular and peripheral pulmonary artery stenosis, bicuspid aortic valve, aortic valve stenosis and subendothelial myocardial fibrosis. A review of the literature revealed many clinical and pathological features common to both syndromes. The hypothesis that rubella virus produced germ-cell mutation and subsequent persistence of rubella in the zygote produced further fetal damage is presented to explain these observations.     

Aortic valve replacement in a patient with severe hemophilia

Hemophilia A is an inherited bleeding disorder characterized by factor VIII deficiency. The basis for insufficient hemostasis lies within inadequate amplification of factor Xa production with the undersupplied factor VIII. We report on a young patient with critical aortic stenosis bearing all the clinical stigmata of severe hemophilia, in whom aortic valve replacement was performed with a tissue valve in order to avoid the need for long term anticoagulation.     

Earlier accumulation of calcium, phosphorus, and magnesium in the coronary artery in comparison with the ascending aorta, aortic valve, and mitral valve

To explore reasons for a high accumulation of Ca and P occurring in the coronary artery of Thai with aging, the authors investigated age-related changes of elements in the coronary artery, ascending aorta near the heart, and cardiac valves in single individuals, and the relationships in the elements between the coronary artery and either the ascending aorta or cardiac valves. After an ordinary dissection by medical students at Chiang Mai University was finished, the anterior descending arteries of the left coronary artery, ascending aortas, mitral valves, and aortic valves were resected from the subjects. The subjects consisted of 17 men and 9 women, ranging in age from 46 to 76 yr. The element content was analyzed by inductively coupled plasma-atomic emission spectrometry. The average content of Ca and P was the highest in the coronary artery and decreased in the order aortic valve, ascending aorta, and mitral valve. The Ca, P, and Mg content increased in the coronary artery in the fifties and in the ascending aorta, aortic valve, and mitral valve in the sixties. It should be noted that the accumulation of Ca, P, and Mg occurred earlier in the coronary artery than in the ascending aorta, aortic valve, and mitral valve. It was found that with respect to the Ca, P, Mg, and Na contents, the coronary artery correlated well with both the aortic valve and ascending aorta, especially with the aortic valve, but it did not correlate with the mitral valves. This finding suggests that the accumulation of Ca, P, Mg, and Na occurs in the coronary artery together with the aortic valve and ascending aorta, but not together with the mitral valve. Because regarding the accumulation of Ca, P, and Mg, the ascending aorta and aortic valve are preceded by the coronary artery, it is unlikely that the accumulation of Ca, P, and Mg spreads from the ascending aorta or aortic valve to the coronary artery.     

Osteopontin controls endothelial cell migration in vitro and in excised human valvular tissue from patients with calcific aortic stenosis and controls

Calcific aortic stenosis (CAS) is a pathological condition of the aortic valve characterized by dystrophic calcification of the valve leaflets. Despite the high prevalence and mortality associated with CAS, little is known about its pathogenetic mechanisms. Characterized by progressive dystrophic calcification of the valve leaflets, the early stages of aortic valve degeneration are similar to the active inflammatory process of atherosclerosis including endothelial disruption, inflammatory cell infiltration, lipid deposition, neo-vascularization and calcification. In the vascular system, the endothelium is an important regulator of physiological and pathological conditions; however, the contribution of endothelial dysfunction to valvular degeneration at the cellular and molecular level has received little attention. Endothelial cell (EC) activation and neo-vascularization of the cusps characterizes all stages of aortic valvular degeneration from aortic sclerosis to aortic stenosis. Here we reported the role of osteopontin (OPN) in the regulation of EC activation in vitro and in excised tissue from CAS patients and controls. OPN is an important pro-angiogenic factor in several pathologies. High levels of OPN have been demonstrated in both tissue and plasma of patients with aortic valve sclerosis and stenosis. The characterization of valvular ECs as a cellular target for OPN will help us uncover the pathogenesis of aortic valve degeneration and stenosis, opening new perspectives for the prevention and therapy of this prevalent disease.     

Numerical simulation of steady turbulent flow through trileaflet aortic heart valves—II. Results on five models

Turbulent flow simulations are run for five aortic trileaflet valve geometries, ranging from a valve leaflet orifice area of 1.1 cm² (Model A1—very stenotic) to 5.0 cm² (Model A5—natural valve). The simulated data compares well with experimental measurements made downstream of various aortic trileaflet valves by Woo (PhD Thesis, 1984). The location and approximate width and length of recirculation regions are correctly predicted. The less stenotic valve models reattach at the end of the aortic sinus region, 1.1 diameters downstream of the valve. The central jet exiting the less stenotic valve models is not significantly different from fully developed flow, and therefore recovers very quickly downstream of the reattachment point. The more stenotic valves disturb the flow to a greater degree, generating recirculation regions large enough to escape the sinuses and reattach further downstream. Peak turbulent shear stress values downstream of the aortic valve models which approximated prosthetic valves are 125 and 300 N m⁻², very near experimental observations of 150 to 350 N m⁻². The predicted Reynolds stress profiles also present the correct shape, a double peak profile, with the location of the peak occuring at the location of maximum velocity gradient, which occurs near the recirculation region. The pressure drop across model A2 (leaflet orifice area 1.6 cm²) is 20 mmHg at 1.6 diameters downstream. This compares well with values ranging from 19.5 to 26.2 mmHg for valves of similar orifice areas. The pressure drop decreases with decreasing valve stenosis, to a negligible value across the least stenotic valve model. Based on the good agreement between experimental measurements of velocity, shear stress and pressure drop, compared to the simulated data, the model has the potential to be a valuable tool in the analysis of heart valve designs.