Non-invasive estimation of the mechanical properties of the heart
Inventors
Torres, William M. • Spinale, Francis G. • Shazly, Tarek M.
Assignees
University of South Carolina • US Department of Veterans Affairs
Publication Number
US-11304682-B2
Publication Date
2022-04-19
Expiration Date
2039-07-29
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Abstract
Methods and systems for utilizing myocardial strain imaging in an inverse framework to identify mechanical properties of the heart and to determine structural and functional milestones for the development and progression to heart failure.
Core Innovation
The invention provides methods and systems for utilizing myocardial strain imaging, specifically two-dimensional speckle-tracking echocardiography (STE), in an inverse finite element framework to identify mechanical properties of the left ventricular myocardium. This approach removes dependencies on hemodynamic load and left ventricular geometry, allowing for non-invasive quantification of regional mechanical stiffness and wall stress of the heart. It involves generating patient-specific finite-element meshes from echocardiographic images and applying a pattern search optimization algorithm to match simulated strains and geometric parameters with experimental measurements.
Heart failure arises from impaired left ventricular ejection performance (HFrEF) or impaired filling (HFpEF), each involving progressive left ventricular remodeling characterized by changes in geometry, composition, and mechanical properties. Current global measures like ejection fraction can be insensitive to early remodeling changes, and although STE offers more regional sensitivity, its clinical utility is limited by load and geometric dependencies. The invention addresses these limitations by integrating STE-derived strain, geometry, and ventricular pressure to inversely determine regional myocardial stiffness, enabling a comprehensive biomechanical analysis that is more sensitive to disease progression than existing methods.
Claims Coverage
The patent contains one independent claim outlining a method with several inventive features related to analyzing passive left ventricular myocardial stiffness using echocardiographic data and inverse finite element modeling.
Integration of regional geometry and strain measurements within an inverse finite-element framework
The method accurately measures regional left ventricular geometry and myocardial strain, and integrates these measurements with an estimation of ventricular pressure to compute mechanical properties of the myocardium.
Generation of patient-specific finite-element mesh from mid-myocardial node positions
The left ventricular configuration is generated from mid-myocardial nodes positioned at the onset of diastole, and the mesh includes endocardial and epicardial nodes estimated from wall thickness, constructing a trilinear hexahedral finite element mesh spanning these nodes.
Definition of quasi-static structural mechanics steps with specific boundary conditions
Two sequential steps are defined: one applying prescribed translation to basal nodes based on echocardiographic data, and another fixing basal nodes while applying end-diastolic pressure to the endocardial surface, optionally including opposing pressure on epicardial nodes to mimic physiological tethering effects.
Use of objective function to optimize distribution of regional stiffness indices
An objective function combining differences in end-diastolic area, regional strain, and wall thickness between computational and in-vivo data is minimized via a pattern search optimization algorithm to identify spatially varying myocardial mechanical properties.
Generation of spatiotemporal maps of passive myocardial stiffness and diastolic stress
The method outputs detailed spatial distributions of regional passive myocardial stiffness and end-diastolic stresses, providing clinically relevant biomechanical information about the heart.
These inventive features collectively enable non-invasive, sensitive assessment of left ventricular myocardial mechanical properties by integrating echocardiographic strain data with advanced finite element modeling and optimization, facilitating improved diagnosis and monitoring of heart disease progression.
Stated Advantages
Provides a sensitive biomechanical marker that is independent of hemodynamic load and left ventricular geometry, improving the identification and tracking of left ventricular remodeling.
Complements standard echocardiographic analysis by offering detailed regional mechanical property maps, enhancing disease diagnosis and prognosis.
Allows non-invasive and potentially serial assessment of myocardial mechanical properties at the point of care, facilitating personalized evaluation of heart failure progression.
Enables comprehensive biomechanical analysis from routinely acquired echocardiographic images without the need for additional imaging or invasive procedures.
Documented Applications
Assessment and monitoring of left ventricular remodeling in heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF) phenotypes.
Non-invasive determination of regional myocardial passive stiffness and diastolic wall stress in clinical settings as a complement to standard transthoracic echocardiography.
Application to other soft tissues, contingent on availability of deformation imaging and load estimation, such as biomechanical analysis of thoracic or abdominal aortic aneurysms to inform surgical decisions.
Tracking disease progression and evaluating treatment efficacy in patients presenting with heart disease symptoms.
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