Method and system for non-invasive measurement of cardiac parameters
Inventors
Goor, Daniel A. • Frinerman, Efim • Granov, Evgeny • Granov, Igor
Assignees
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Publication Number
US-9808168-B2
Publication Date
2017-11-07
Expiration Date
Abstract
A method and system are presented for use in assessment of at least one cardiac parameter of an individual. An electrodes arrangement is applied to an individual's body, for applying an electrical field to the body and providing an electrical output indicative of a systolic impedance change and of a velocity of said change during a cardiac cycle. Also provided is additional data indicative of at least of the following conditions of the individual: a value of total peripheral resistance (TPR), a value of cardiac index (CI), and existence of the AHF condition. Data corresponding to these condition is analyzed to determine whether the TPR satisfies a first predetermined condition and/or the CI satisfies a predetermined second condition and/or whether the acute heart failure (AHF) condition is identified, to thereby use the data indicative of the measured electrical output and selectively calculate said at least one cardiac parameter based on either the systolic impedance change data or on said data of the velocity of the impedance change.
Core Innovation
The invention is an impedance measurement system that assesses at least one cardiac parameter of an individual using an electrodes arrangement configured to apply an electrical field through one electrode set and obtain an electrical output through the other electrode set. The system derives from a cardiac cycle both systolic impedance change, ΔR, and velocity of the systolic impedance change, dR/dt, during systole. Electrodes are arranged for attachment to an arm at a first lateral side and a leg at a second lateral side of the individual's body.
A control unit receives input data indicative of at least one condition of the individual and selects how to calculate the cardiac parameter. When the input data indicates the individual is sustained by acute heart failure (AHF), the control unit selects velocity data for calculating the at least one cardiac parameter. When the input data indicates the individual is not sustained by AHF, the control unit either selects systolic impedance change data, or analyzes additional input data indicative of other predetermined conditions, including total peripheral resistance (TPR) and cardiac index (CI), to determine whether to use ΔR data or dR/dt data.
The system provides conditional stroke volume (SV) computation based on velocimetric versus volumetric principles, where ΔR is linked to volumetric blood and arterial expansion and dR/dt is linked to blood-flow velocity effects. It introduces corrected SV equations, including a hydration factor (HF) and calibration coefficients, and a combined SV model in which coefficients enable conditional switching or weighting via kHR and kdr. The system also includes computing cardiac parameters such as TPR and cardiac index (CI), and generates an output indicative of the calculation result.
Claims Coverage
The document provides one independent claim (clm-00001). It is supported by dependent claims that refine specific cardiac parameters, including stroke volume, and specify how additional conditions such as TPR and CI are determined and used.
Arm-and-leg impedance electrodes yielding ΔR and dR/dt
An impedance measurement system in which a measurement unit includes first and second electrode sets configured to attach to one arm and one leg, respectively, to apply an electrical field through one electrode set and obtain an electrical output through the other electrode set, the output comprising measured data indicative of both systolic impedance change (ΔR) and velocity of a systolic impedance change (dR/dt) during a cardiac cycle.
Condition-based selection between ΔR and dR/dt
A control unit that receives input data indicative of whether the individual is sustained by acute heart failure (AHF), analyzes the input data, and upon identifying AHF selecting the velocity of systolic impedance change for calculating the at least one cardiac parameter; upon identifying not AHF, either selecting systolic impedance change data or analyzing additional input data indicative of predetermined conditions including at least one of total peripheral resistance (TPR) and a cardiac index (CI) to determine whether to use ΔR data or the velocity data.
Condition-refined stroke volume via corrected two-part SV model
A stroke volume calculation that computes cardiac stroke volume (SV) using two-part corrected equations based on either systolic impedance change and/or velocity of impedance change, with coefficients conditionally set based on whether specified conditions are satisfied, including calibration and correction factors such as hydration factor (HF) and coefficients kHR and kdr.
TPR determination using impedance change and blood pressure input
Determining TPR data by processing first measured systolic impedance change data and second measured data indicative of an individual's blood pressure.
Quantitative TPR range for an additional predetermined condition
Satisfying an additional predetermined condition when a measured TPR value exceeds a value in a range from about 1800 (dynes/cm^-5) to about 1900 (dynes/sec^-5).
Cardiac index threshold for an additional predetermined condition
Satisfying an additional predetermined condition when the cardiac index is above 2.5.
Across the independent claim and its refinements, the core claim coverage is the combination of arm-and-leg impedance measurement producing both ΔR and dR/dt, and a control-unit logic that selects which measured data to use based on acute heart failure status, with further selection driven by additional predetermined conditions such as TPR and CI, including quantitative constraints and conditional corrected SV computation.
Stated Advantages
Improved reliability of dR/dt in acute heart failure conditions [as described in the provided summary content].
Higher accuracy of ΔR in lower-TPR/post-surgical ICU conditions [as described in the provided summary content].
Generates an output indicative of the calculation result for at least one cardiac parameter based on condition-based selection between impedance-derived measures.
Documented Applications
Assessment of at least one cardiac parameter in individuals sustained by acute heart failure (AHF) [as described in the provided summary content].
Use in post-coronary surgery ICU conditions with lower-TPR for comparison between ΔR-based and dR/dt-based stroke volume assessment [as described in the provided summary content].
Comparative evaluation of stroke volume (SV) derived from ΔR-based and dR/dt-based approaches against thermodilution (TD) [as described in the provided summary content].
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