Assessment of haemolysis models for a positive-displacement total artificial heart.

The assessment and reduction of haemolysis within mechanical circulatory support (MCS) remains a concern with regard to device safety and regulatory approval. Numerical methods for predicting haemolysis have typically been applied to rotary MCS devices and the extent to which these methods apply to positive-displacement MCS is unclear. The aim of this study was to evaluate the suitability of these methods for assessing haemolysis in positive-displacement blood pumps.

Fluid-structure interaction modelling of a positive-displacement Total Artificial Heart.

For those suffering from end-stage biventricular heart failure, and where a heart transplantation is not a viable option, a Total Artificial Heart (TAH) can be used as a bridge to transplant device. The Realheart TAH is a four-chamber artificial heart that uses a positive-displacement pumping technique mimicking the native heart to produce pulsatile flow governed by a pair of bileaflet mechanical heart valves. The aim of this work was to create a method for simulating haemodynamics in positive-displacement blood pumps, using computational fluid dynamics with fluid-structure interaction to eliminate the need for pre-existing in vitro valve motion data, and then use it to investigate the performance of the Realheart TAH across a range of operating conditions.

MRI-based strain measurements reflect morphological changes following myocardial infarction: A study on the UK Biobank cohort.

In a porcine experimental model of myocardial infarction, a localised, layer-specific, circumferential left ventricular strain metric has been shown to indicate chronic changes in ventricular function post-infarction more strongly than ejection fraction. This novel strain metric might therefore provide useful prognostic information clinically. In this study, existing clinical volume indices, global strains, and the novel, layer-specific strain were calculated for a large human cohort to assess variations in ventricular function and morphology with age, sex, and health status.

Video-based valve motion combined with computational fluid dynamics gives stable and accurate simulations of blood flow in the Realheart total artificial heart.

Background: Patients with end-stage, biventricular heart failure, and for whom heart transplantation is not an option, may be given a Total Artificial Heart (TAH). The Realheart® is a novel TAH which pumps blood by mimicking the native heart with translation of an atrioventricular plane. The aim of this work was to create a strategy for using Computational Fluid Dynamics (CFD) to simulate haemodynamics in the Realheart®, including motion of the atrioventricular plane and valves.

Comparison of the within-reader and inter-vendor agreement of left ventricular circumferential strains and volume indices derived from cardiovascular magnetic resonance imaging.

Purpose: Volume indices and left ventricular ejection fraction (LVEF) are routinely used to assess cardiac function. Ventricular strain values may provide additional diagnostic information, but their reproducibility is unclear. This study therefore compares the repeatability and reproducibility of volumes, volume fraction, and regional ventricular strains, derived from cardiovascular magnetic resonance (CMR) imaging, across three software packages and between readers.

Normal fluid stresses are prevalent in rotary ventricular assist devices: A computational fluid dynamics analysis.

Despite the evolution of ventricular assist devices, ventricular assist device patients still suffer from complications due to the damage to blood by fluid dynamic stress. Since rotary ventricular assist devices are assumed to exert mainly shear stress, studies of blood damage are based on shear flow experiments. However, measurements and simulations of cell and protein deformation show normal and shear stresses deform, and potentially damage, cells and proteins differently.

In silico coronary wave intensity analysis: application of an integrated one-dimensional and poromechanical model of cardiac perfusion.

Coronary wave intensity analysis (cWIA) is a diagnostic technique based on invasive measurement of coronary pressure and velocity waveforms. The theory of WIA allows the forward- and backward-propagating coronary waves to be separated and attributed to their origin and timing, thus serving as a sensitive and specific cardiac functional indicator. In recent years, an increasing number of clinical studies have begun to establish associations between changes in specific waves and various diseases of myocardium and perfusion.

Clinical Diagnostic Biomarkers from the Personalization of Computational Models of Cardiac Physiology.

Computational modelling of the heart is rapidly advancing to the point of clinical utility. However, the difficulty of parameterizing and validating models from clinical data indicates that the routine application of truly predictive models remains a significant challenge. We argue there is significant value in an intermediate step towards prediction.

Measurement and modeling of coronary blood flow.

Ischemic heart disease that comprises both coronary artery disease and microvascular disease is the single greatest cause of death globally. In this context, enhancing our understanding of the interaction of coronary structure and function is not only fundamental for advancing basic physiology but also crucial for identifying new targets for treating these diseases. A central challenge for understanding coronary blood flow is that coronary structure and function exhibit different behaviors across a range of spatial and temporal scales.

Comparison of vortical structures induced by arteriovenous grafts using vector Doppler ultrasound.

Arteriovenous prosthetic grafts are used in hemodialysis. Stenosis in the venous anastomosis is the main cause of occlusion and the role of local hemodynamics in this is considered significant. A new spiral graft design has been proposed to stabilize the flow phenomena in the host vein.

Multi-scale parameterisation of a myocardial perfusion model using whole-organ arterial networks.

A method to extract myocardial coronary permeabilities appropriate to parameterise a continuum porous perfusion model using the underlying anatomical vascular network is developed. Canine and porcine whole-heart discrete arterial models were extracted from high-resolution cryomicrotome vessel image stacks. Five parameterisation methods were considered that are primarily distinguished by the level of anatomical data used in the definition of the permeability and pressure-coupling fields.

Toward GPGPU accelerated human electromechanical cardiac simulations.

In this paper, we look at the acceleration of weakly coupled electromechanics using the graphics processing unit (GPU). Specifically, we port to the GPU a number of components of CHeart--a CPU-based finite element code developed for simulating multi-physics problems. On the basis of a criterion of computational cost, we implemented on the GPU the ODE and PDE solution steps for the electrophysiology problem and the Jacobian and residual evaluation for the mechanics problem.

Myocardial perfusion distribution and coronary arterial pressure and flow signals: clinical relevance in relation to multiscale modeling, a review.

Coronary artery disease, CAD, is associated with both narrowing of the epicardial coronary arteries and microvascular disease, thereby limiting coronary flow and myocardial perfusion. CAD accounts for almost 2 million deaths within the European Union on an annual basis. In this paper, we review the physiological and pathophysiological processes underlying clinical decision making in coronary disease as well as the models for interpretation of the underlying physiological mechanisms.

Parameterisation of multi-scale continuum perfusion models from discrete vascular networks.

Experimental data and advanced imaging techniques are increasingly enabling the extraction of detailed vascular anatomy from biological tissues. Incorporation of anatomical data within perfusion models is non-trivial, due to heterogeneous vessel density and disparate radii scales. Furthermore, previous idealised networks have assumed a spatially repeating motif or periodic canonical cell, thereby allowing for a flow solution via homogenisation.

OpenCMISS: a multi-physics & multi-scale computational infrastructure for the VPH/Physiome project.

The VPH/Physiome Project is developing the model encoding standards CellML (cellml.org) and FieldML (fieldml.org) as well as web-accessible model repositories based on these standards (models.