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

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

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

Effect of Aging on Intraventricular Kinetic Energy and Energy Dissipation

: In recent years, analysis of kinetic energy (KE) and the rate of kinetic energy dissipation (KED) or energy loss (EL) within the cardiac chambers, obtained by cardiac imaging techniques, has gained increasing attention. Thus, there is a need to clarify the effect of physiological variables, specifically aging, on these energetic measures. To elucidate this aspect, we reviewed the literature on this topic. Overall, cardiac magnetic resonance and echocardiographic studies published so far indicate that aging affects the energetics of left and right intraventricular blood flow, although not all energy measures during the cardiac cycle seem to be affected by age in the same way. Current studies, however, have limitations. Additional large, multicenter investigations are needed to test the effect of physiological variables on intraventricular KE and KED/EL measures

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

Principles of cardiovascular magnetic resonance feature tracking and echocardiographic speckle tracking for informed clinical use

Tissue tracking technology of routinely acquired cardiovascular magnetic resonance (CMR) cine acquisitions has increased the apparent ease and availability of non-invasive assessments of myocardial deformation in clinical research and practice. Its widespread availability thanks to the fact that this technology can in principle be applied on images that are part of every CMR or echocardiographic protocol. However, the two modalities are based on very different methods of image acquisition and reconstruction, each with their respective strengths and limitations. The image tracking methods applied are not necessarily directly comparable between the modalities, or with those based on dedicated CMR acquisitions for strain measurement such as tagging or displacement encoding. Here we describe the principles underlying the image tracking methods for CMR and echocardiography, and the translation of the resulting tracking estimates into parameters suited to describe myocardial mechanics. Technical limitations are presented with the objective of suggesting potential solutions that may allow informed and appropriate use in clinical applications

Analysis of the distribution and orientation of oxygenated and non-oxygenated blood in a double outlet right ventricle

Double outlet right ventricle (DORV) is a malformation of the fetal heart in utero that affects the ventricular chambers. It usually presents with a displacement of the aorta and more than half the circumference of both arterial valves in the right ventricle. A peculiar characteristic is given by an interventricular septal defect (VSD), which allows communication between the left ventricle and the right with consequent mixing of oxygenated and non-oxygenated blood inside the cavities. A crucial question in assessing the degree of severity of functional dysfunction concerns the percentage of oxygenated blood that is ejected into the primary circulation via the aorta, a result that depends on the details of the vortex flow pattern within the two ventricular chambers. This study analyzes a complete DORV case through the use of numerical simulations that allow to identify the concentrations of oxygenated and non-oxygenated blood passing through this geometry. Results show that the VSD presents a significant impact on the fluid dynamic performance of the two ventricles. The analysis of blood concentration allowed to quantify the presence of oxygenated blood ejected into the pulmonary artery and of non-oxygenated blood into the aortic artery. The analysis of this specific case aims to demonstrate how the fluid dynamics analysis of this rare malformation, properly coupled with imaging technology, can provide information that could not be obtained otherwise and that are relevant for a careful clinical management including timely therapeutic intervention