Enhanced Extraction of Activation Time and Contractility From Myocardial Strain Data Using Parameter Space Features and Computational Simulations.

A computational model enables the extraction of two critical myocardial tissue properties: activation time (AT) and contractility (Con) from recorded cardiac strains. However, interference between these parameters reduces the precision and accuracy of the extraction process. This study investigates whether leveraging features in the parameter space can enhance parameter extraction.

Detection of physiological control inputs preload and afterload from intrinsic pump parameters in total artificial heart.

Background: In the total artificial heart (TAH), the inputs to the physiological control unit, preload, and afterload, are detected from intrinsic pump parameters (e.g., motor current).

Uniqueness of local myocardial strain patterns with respect to activation time and contractility of the failing heart: a computational study.

Background: Myocardial deformation measured by strain is used to detect electro-mechanical abnormalities in cardiac tissue. Estimation of myocardial properties from regional strain patterns when multiple pathologies are present is therefore a promising application of computer modelling. However, if different tissue properties lead to indistinguishable strain patterns ('degeneracy'), the applicability of any such method will be limited.

Three-wall segment (TriSeg) model describing mechanics and hemodynamics of ventricular interaction.

A mathematical model (TriSeg model) of ventricular mechanics incorporating mechanical interaction of the left and right ventricular free walls and the interventricular septum is presented. Global left and right ventricular pump mechanics were related to representative myofiber mechanics in the three ventricular walls, satisfying the principle of conservation of energy. The walls were mechanically coupled satisfying tensile force equilibrium in the junction.

Mechanical discoordination rather than dyssynchrony predicts reverse remodeling upon cardiac resynchronization.

By current guidelines a considerable part of the patients selected for cardiac resynchronization therapy (CRT) do not respond to the therapy. We hypothesized that mechanical discoordination [opposite strain within the left ventricular (LV) wall] predicts reversal of LV remodeling upon CRT better than mechanical dyssynchrony. MRI tagging images were acquired in CRT candidates (n = 19) and in healthy control subjects (n = 9).

Three-dimensional mapping of mechanical activation patterns, contractile dyssynchrony and dyscoordination by two-dimensional strain echocardiography: rationale and design of a novel software toolbox.

Background: Dyssynchrony of myocardial deformation is usually described in terms of variability only (e.g. standard deviations SD's).

Modeling ventricular interaction: a multiscale approach from sarcomere mechanics to cardiovascular system hemodynamics.

Direct ventricular interaction via the interventricular septum plays an important role in ventricular hemodynamics and mechanics. A large amount of experimental data demonstrates that left and right ventricular pump mechanics influence each other and that septal geometry and motion depend on transmural pressure. We present a lumped model of ventricular mechanics consisting of three wall segments that are coupled on the basis of balance laws stating mechanical equilibrium at the intersection of the three walls.

Continuous axial contraction wave in the free wall of the guinea pig left ventricle.

We studied the variation from the simultaneous contraction of the normal left ventricle (LV). The pattern of the contraction along the LV long axes was assessed on the LV free wall on seven guinea pig hearts in situ with ultra fast video system and epicardial markers by means of the latitude and the size of the areas defined by markers. We found that the contraction occurs as a continuous contraction wave from the apex towards the base, which might yield functional adaptation of these two regions to diastolic and systolic function, respectively.

The video technique developed for measuring epicardial strains on guinea pig's left ventricle.

Single-plain video used for measurements of epicardial strains is a technique that yields minor interference with the studied mechanical properties of the ventricle. Due to its low temporal resolution, the existing technique is, however, not appropriate for small animals. We questioned whether the technique could be improved enough to cope with higher heart rates and miniaturization necessary for experiments on rats, mice and guinea pigs.

Contraction wave in axial direction in free wall of guinea pig left ventricle.

Mechanical activation of the normal left ventricle (LV) is not simultaneous; however, the potential consequences of the ejection function of the ventricle are not entirely known. We studied contraction of the LV free wall to determine whether it reveals a contraction wave in the axial direction during ejection. Seven guinea pig hearts in situ were studied via thoracotomy.

The reversible displacement of the passive diastolic p-V curve in the isolated guinea pig left ventricle.

We studied viscoelastic behaviour of the isolated diastolic guinea pig left ventricle (LV), manifested in changes of the hysteresis loop of the pressure-volume (p-V) diagram, produced by acute volume loading. Specifically, we investigated how the width of the hysteresis depends on the way LV volume loading, and whether changes in the hysteresis width are reversible. Each of 11 LV was instrumented with a catheter for injection and withdrawal of saline, and a micromanometer (Millar, 2F) to measure LV pressure.