Effect of intra-myocardial algisyl-LVR™ injectates on fiber structure in porcine heart failure

Recent preclinical trials have shown that alginate injections are a promising treatment for ischemic heart disease. Although improvements in heart function and global structure have been reported following alginate implants, the underlying structure is poorly understood. Using high resolution ex vivo MRI and DT-MRI of the hearts of normal control swine (n=8), swine with induced heart failure (n=5), and swine with heart failure and alginate injection treatment (n=6), we visualized and quantified the fiber distribution and implant material geometry. Our findings show that the alginate injectates form solid ellipsoids with a retention rate of 68.7%±21.3% (mean±SD) and a sphericity index of 0.37±0.03. These ellipsoidal shapes solidified predominantly at the mid-wall position with an inclination of -4.9°±31.4° relative to the local circumferential direction. Overall, the change to left ventricular wall thickness and myofiber orientation was minor and was associated with heart failure and not the presence of injectates. These results show that alginate injectates conform to the pre-existing tissue structure, likely expanding along directions of least resistance as mass is added to the injection sites. The alginate displaces the myocardial tissue predominantly in the longitudinal direction, causing minimal disruption to the surrounding myofiber orientations

3D cardiac deformation from ultrasound images

Abstract. The quantitative estimation of regional cardiac deformation from 3D image sequences has important clinical implications for the assessment of viability in the heart wall. Such estimates have so far been obtained almost exclusively from Magnetic Resonance (MR) images, specifically MR tagging. In this paper we describe a methodology for estimating cardiac deformations from 3D ultrasound images. The images are segmented interactively and then initial correspondence is established using a shape-tracking approach. A dense motion field is then estimated using an anisotropic linear elastic model, which accounts for the fiber directions in the left-ventricle. The dense motion field is in turn used to calculate the deformation of the heart wall in terms of strain in cardiac specific directions. The strains obtained using this approach in open-chest dogs before and after coronary occlusion related to changes in blood flow, show good agreement with previously published results in the literature. This proposed method provides quantitative regional 3D estimates of heart deformation from ultrasound images.

Left ventricular shear strain in model and experiment

Mathematical modeling of cardiac mechanics could be a useful clinical tool, both in translating measured abnormalities in cardiac deformation into the underlying pathology, and in selecting a propertreatment. We investigated to what extent a previously published model of cardiac mechanics could predict deformation in the healthy left ventricle, as measured using MR tagging. The model adequately predicts circumferential strain, but fails to accurately predict shear strain. However, the time course of shear strain proves to be that sensitive tomyofiber orientation, that agreement between model predictions and experiment may be expected if fiber orientation is changed by only a few degrees

Numerical simulation of the non-Newtonian blood flow through a mechanical aortic valve

This work focuses on the comparison between Newtonian and non-Newtonian blood flows through a bileaflet mechanical heart valve in the aortic root. The blood, in fact, is a concentrated suspension of cells, mainly red blood cells, in a Newtonian matrix, the plasma, and consequently its overall behavior is that of a non-Newtonian fluid owing to the action of the cells’ membrane on the fluid part. The common practice, however, assumes the blood in large vessels as a Newtonian fluid since the shear rate is generally high and the effective viscosity becomes independent of the former. In this paper, we show that this is not always the case even in the aorta, the largest artery of the systemic circulation, owing to the pulsatile and transitional nature of the flow. Unexpectedly, for most of the pulsating cycle and in a large part of the fluid volume, the shear rate is smaller than the threshold level for the blood to display a constant effective viscosity and its shear thinning character might affect the system dynamics. A direct inspection of the various flow features has shown that the valve dynamics, the transvalvular pressure drop and the large-scale features of the flow are very similar for the Newtonian and non-Newtonian fluid models. On the other hand, the mechanical damage of the red blood cells (hemolysis), induced by the altered stress values in the flow, is larger for the non-Newtonian fluid model than for the Newtonian one

Do disease specific characteristics add to the explanation of mobility limitations in patients with different chronic diseases? A study in The Netherlands.

STUDY OBJECTIVES: To determine whether disease specific characteristics, reflecting clinical disease severity, add to the explanation of mobility limitations in patients with specific chronic diseases. DESIGN AND SETTING: Cross sectional study of survey data from community dwelling elderly people, aged 55-85 years, in the Netherlands. PARTICIPANTS AND METHODS: The additional explanation of mobility limitations by disease specific characteristics was examined by logistic regression analyses on data from 2830 community dwelling elderly people. MAIN RESULTS: In the total sample, chronic non-specific lung disease, cardiac disease, peripheral atherosclerosis, diabetes mellitus, stroke, arthritis and cancer (the index diseases), were all independently associated with mobility limitations. Adjusted for age, sex, comorbidity, and medical treatment disease specific characteristics that explain the association between disease and mobility mostly reflect decreased endurance capacity (shortness of breath and disturbed night rest in chronic non-specific lung disease, angina pectoris and congestive heart failure in cardiac disease), or are directly related to mobility function (stiffness and lower body complaints in arthritis). For atherosclerosis and diabetes mellitus, disease specific characteristics did not add to the explanation of mobility limitations. CONCLUSIONS: The results provide evidence that, to obtain more detailed information about the differential impact of chronic diseases on mobility, disease specific characteristics are important to take into account