The Influence of Mitral Valve Asymmetry for an Improved Choice of Valve Repair or Replacement

The study of valve asymmetry represents an important avenue for modern cardiac surgery. The correct choice of leaflet reconstruction may indicate a new path in the quality and long-term survival of patients. A systematic investigation was performed with a total of 25 numerical simulations using a healthy ventricle and an ideal valve with varying degrees of valve asymmetry. An overall assessment is made in terms of vorticity, kinetic energy, dissipated energy, and hemodynamic forces. The results indicate that the optimal asymmetry to consider for a valve repair or prosthetic design is between 0.2 and 0.4 with an optimal point of about 0.3. Out of this range, the heart is subjected to an excessive workload, which can only worsen the patient’s state of health

Fluid flow in a helical vessel in presence of a stenosis

Large arteries are not straight and rather present curvature and torsion. The present study analyzed fluid flow in a helical vessel without and with a stenosis in comparison with an analogous rectilinear vessel. The analysis is performed by threedimensional numerical simulation of the Navier\u2013Stokes equations under steady conditions considering stenosis as an axially symmetric reduction of vessel lumen. Results show that the double curvature gives rise to persistent secondary motion which combines with the vorticity separated behind the constriction to develop a complex three-dimensional vorticity structure. The curved streamlines and the three-dimensional vortex wake result in a increase of energetic losses in helical vessels. However, the same symmetry break due to the double curvature improves the capacity of self-cleaning and allows a more rapid wash-out of the flowing blood

Left Ventricular Fluid Mechanics: the long way from theoretical models to clinical applications

\u2014The flow inside the left ventricle is characterized by the formation of vortices that smoothly accompany blood from the mitral inlet to the aortic outlet. Computational fluid dynamics permitted to shed some light on the fundamental processes involved with vortex motion. More recently, patient-specific numerical simulations are becoming an increasingly feasible tool that can be integrated with the developing imaging technologies. The existing computational methods are reviewed in the perspective of their potential role as a novel aid for advanced clinical analysis. The current results obtained by simulation methods either alone or in combination with medical imaging are summarized. Open problems are highlighted and perspective clinical applications are discussed

clinical application of 2d speckle tracking strain for assessing cardio toxicity in oncology

Echocardiography has recently undergone innovations due to the availability of deformation parameters as strain, strain rate, torsion and rotation that allow an accurate assessment of myocardial function. Because of this general progress, the importance of myocardial deformation parameters has been highlighted, and some aspects of their clinical and research applications have recently been considered for the daily management of many acute and chronic metabolic diseases. The deformation parameters are largely proposed for the early detection of myocardial dysfunction, especially in the case of patients being completely asymptomatic. Strain analysis is extensively applied to cardiomyopathies, to coronary artery disease, or to the evaluation of the "forgotten chambers", such as the right ventricles and atria. More recently, several other clinical contexts, like non-communicable chronic diseases (NCCD), have actually been benefitting from specific evaluation by strain analysis. Lately, some specific aspects of strain evaluation, particularly Global Longitudinal Strain (GLS) have been shown to provide useful information of clinical relevance in the case of cancer patients. This paper presents an initial review of the recent applications of strain analysis in cardio-oncology, in order to share the recent experience in this field and to support the role of these parameters in cardio-oncology

Analysis of mitral valve regurgitation by computational fluid dynamics

The clinical syndrome of mitral insufficiency is a common consequence of mitral valve (MV) prolapse, when the MV leaflets do not seal the closed orifice and blood regurgitates back to the atrium during ventricular contraction. There are different types of MV prolapse that may influence the degree of regurgitation also in relation to the left ventricle (LV) geometry. This study aims to provide some insight into the fluid dynamics of MV insufficiency in view of improving the different measurements available in the clinical setting. The analysis is performed by a computational fluid dynamics model coupled with an asymptotic model of the MV motion. The computational fluid dynamics solution uses the immersed boundary method that is efficiently integrated with clinical imaging technologies. Healthy and dilated LVs obtained by multislice cardiac MRI are combined with simplified models of healthy and pathological MVs deduced from computed tomography and 4D-transesophageal echocardiography. The results demonstrated the properties of false regurgitation, blood that did not cross the open MV orifice and returns into the atrium during the backward motion of the MV leaflets, whose entity should be accounted when evaluating small regurgitation. The regurgitating volume is found to be proportional to the effective orifice area, with the limited dependence of the LV geometry and type of prolapse. These affect the percentage of old blood returning to the atrium which may be associated with thrombogenic risk

Influence of mitral valve elasticity on flow development in the left ventricle

The Mitral valve of the human heart has a great relevance for numerous cardiac pathologies; however, the knowledge of relationships between valvular properties and cardiac function is still limited. On one side, this is partly due to the limited resolution of clinical imaging technologies that do not allow routinely visualization of the valve during its motion. On the other, its modeling presents serious challenges either due to the strong flow\u2013tissueinteraction or because the mechanical properties of its constitutive elements are complex and not measurable in vivo. This work introduces a parametric model of the Mitral valve where the interaction with the blood flow obeys global balances and the overall elastic properties are summarized into a single functional parameter. This is integrated into a numerical model of left ventricular fluid dynamics with the aim to study the effect of varying the valvular stiffness. Results show that the elasticity of the valve influences the amplitude of the mitral opening, while the timings of opening/closure are driven by the transmitral blood flow due to the ventricular dynamics. In addition, the increase of stiffness increases the transvalvular pressure gradients required to ensure the same flow. These results are discussed in relation to parameters for monitoring valvular stiffness that are accessible through clinical imaging

Interplay between Geometry, Fluid Dynamics, and Structure in the Ventricles of the Human Heart

Natural structures conveying fluid flow exhibit an interplay between flow-mediated forces and long-term adaptation. This phenomenon is relevant in the cardiovascular system where the geometric remodelling of the heart chambers is the main mechanism underlying pathological progression leading to hearth failure. Cardiac adaptation is analyzed here in children with a single right ventricle (SRV) in their heart. In these patients, the left ventricle (LV) is not well-developed and the healthy right ventricle (RV) is surgically reconnected, early after birth, to take the functional role of the systemic ventricle. Such a condition represents a special model to investigate cardiac adaptation and this study takes advantage of the availability of an uncommon dataset (64 normal RV, 64 normal LV, 64 SRV with clinically normal function). The ventricular functional performance is analyzed in terms of fluid dynamics and tissue deformation with the objective of verifying to which degree the SRV configuration adapts from the original RV and progresses toward the function of a LV. Results show that SRV immediately assumes a larger volume and a wider geometry due to the higher operating pressure. However, the fluid dynamics is weakly turbulent and produces a reduced propulsion. The surrounding tissue develops muscular thickening with multi-directional orientation of myofibers that mimic a LV. However, the reduced flow performance and a lower structural consistency makes the SRV at higher risk of progressive dysfunctional adaptations. This study demonstrates how the interplay between cardiac flow and tissue response represents the driving macroscopic factor underlying the development of heart failure. More in general, the combined evaluation of fluid dynamics and structural functional properties can be a requirement for the exploration of of the adaptation processes across the different time-scales

Simplified mitral valve modeling for prospective clinical application of left ventricular fluid dynamics

The fluid dynamics inside the left ventricle of the human heart is considered a potential indicator of long term cardiovascular outcome. In this respect, numerical simulations can play an important role for integrating existing technology to reproduce flow details and even conditions associated to virtual therapeutic solutions. Nevertheless, numerical models encounter serious practical difficulties in describing the interaction between flow and surrounding tissues due to the limited information inherently available in real clinical applications. This study presents a computational method for the fluid dynamics inside the left ventricle designed to be efficiently integrated in clinical scenarios. It includes an original model of the mitral valve dynamics, which describes an asymptotic behavior for tissues with no elastic stiffness other than the constrain of the geometry obtained from medical imaging; in particular, the model provides an asymptotic description without requiring details of tissue properties that may not be measurable in vivo. The advantages of this model with respect to a valveless orifice and its limitations with respect to a complete tissue modeling are verified. Its performances are then analyzed in details to ensure a correct interpretation of results. It represents a potential option when information about tissue mechanical properties is insufficient for the implementations of a full fluid-structure interaction approach

The effect of exercise training on left ventricular function in young elite athletes

<p>Abstract</p> <p>Background</p> <p>Regular training, in particular endurance exercise, induces structural myocardial adaptation, so-called "athlete's heart". In addition to the 2D standard echo parameters, assessment of myocardial function is currently possible by deformation parameters (strain, rotation and twist). Aim of study is to assess the role of rotation and twist parameters for better characterize the heart performance in trained elite young athletes from different kind of sports. Eventually, verify early on any possible impact due to the regular sport activity not revealed by the standard parameters.</p> <p>Methods</p> <p>50 young athletes (16 cyclists, 17 soccer players, 17 basket players) regularly trained at least three times a week for at least 9 months a year and 10 young controls (mean age 18.5 ± 0.5 years) were evaluated either by to 2D echocardiography or by a Speckle Tracking (ST) multi-layer approach to calculate Left Ventricle (LV) endocardial and epicardial rotation, twist, circumferential strain (CS) and longitudinal strain (LS). Data were compared by ANOVA test.</p> <p>Results</p> <p>All the found values were within the normal range. Left Ventricle Diastolic Diameter (LVDD 51.7 ± 2.6 mm), Cardiac Mass index (CMi 114.5 ± 18.5 g/m²), epi-CS, epi-LS, epicardial apex rotation and the Endo/Epi twist were significantly higher only in cyclists. In all the groups, a physiological difference of the Endo/Epi basal circumferential strain and twist values have been found. A weak but not significant relationship between the Endo and twist values and LVDD (r²= 0.44, p = .005) and CMi was also reported in cyclists.</p> <p>Conclusions</p> <p>Progressive increase of apical LV twist may represent an important component of myocardial remodelling. This aspect is particularly evident in the young cyclists group where the CMi and the LVDD are higher. ST multilayer approach completes the LV performance evaluation in young trained athletes showing values similar to adults.</p

Cardiac fluid dynamics anticipates heart adaptation

Hemodynamic forces represent an epigenetic factor during heart development and are supposed to influence the pathology of the grown heart. Cardiac blood motion is characterized by a vortical dynamics, and it is common belief that the cardiac vortex has a role in disease progressions or regression. Here we provide a preliminary demonstration about the relevance of maladaptive intra-cardiac vortex dynamics in the geometrical adaptation of the dysfunctional heart. We employed an in vivo model of patients who present a stable normal heart function in virtue of the cardiac resynchronization therapy (CRT, bi-ventricular pace-maker) and who are expected to develop left ventricle remodeling if pace-maker was switched off. Intra-ventricular fluid dynamics is analyzed by echocardiography (Echo-PIV). Under normal conditions, the flow presents a longitudinal alignment of the intraventricular hemodynamic forces. When pacing is temporarily switched off, flow forces develop a misalignment hammering onto lateral walls, despite no other electro-mechanical change is noticed. Hemodynamic forces result to be the first event that evokes a physiological activity anticipating cardiac changes and could help in the prediction of longer term heart adaptations