Assessing cardiac contractility and cardiovascular interaction
First Claim
1. A method of determining an end-systolic pressure-volume relationship (ESPVR) of a human heart during steady state operation of the heart and without any load changes, comprising steps of:
- measuring a blood pressure of a left ventricle of the heart and producing a pressure signal indicative thereof;
measuring a volume of the left ventricle and producing a volume signal indicative thereof;
monitoring the heart to produce ECG timing signals indicative of its activity;
analyzing the pressure, the volume and the timing signals based on a previously determined model of normalized elastance function for a normalized time tN to determine the ESPVR; and
displaying the ESPVR.
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Accused Products
Abstract
A novel method for estimating the end-systolic pressure-volume relationship (ESPVR) is presented. The method provides for accurate estimation of the ESPVR from a single beat of the cardiac cycle. The method is based on normalized human time varying elastance curves [EN (tN)]. The ESPVR is estimated from one beat using PV data measured at normalized time tN and end-systole (tmax) to predict intercept: ##EQU1## and slope: Emax(SB) =P(tmax)/[V(tmax)-V0(SB) ]. The present invention provides a method for ESPVR estimation which is non-invasive and particularly applicable for bedside applications.
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Citations
31 Claims
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1. A method of determining an end-systolic pressure-volume relationship (ESPVR) of a human heart during steady state operation of the heart and without any load changes, comprising steps of:
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measuring a blood pressure of a left ventricle of the heart and producing a pressure signal indicative thereof; measuring a volume of the left ventricle and producing a volume signal indicative thereof; monitoring the heart to produce ECG timing signals indicative of its activity; analyzing the pressure, the volume and the timing signals based on a previously determined model of normalized elastance function for a normalized time tN to determine the ESPVR; and displaying the ESPVR. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An apparatus for determining an end-systolic pressure-volume relationship (ESPVR) during steady state operation of a human heart and without any load changes, comprising:
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a blood pressure monitor for measuring a blood pressure of a left ventricle of the human heart and producing a pressure signal indicative thereof; a volume measurement system for measuring a volume of the left ventricular chamber and producing a volume signal indicative thereof; an electrocardiograph monitor for monitoring the human heart and producing an ECG signal of the human heart; a computer for receiving the pressure signal, the volume signal, and the ECG signal, the computer including; means for determining the ESPVR based upon the pressure, the volume, and a timing derived from the ECG signal and determining the ESPVR. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. A method of determining an end-systolic pressure-volume relationship (ESPVR) of a human heart, comprising steps of:
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measuring a blood pressure of a left ventricle of the heart and producing a pressure signal indicative thereof; measuring a volume of the left ventricle and producing a volume signal indicative thereof; monitoring the heart to produce ECG timing signals indicative of its activity; analyzing the pressure, the volume and the timing signals based on a previously determined model of normalized elastance function for a normalized time tN to determine the ESPVR; and displaying the ESPVR, wherein; the analyzing comprises; recording the pressure signal and the volume signal over at least one cardiac cycle, identifying an R-wave of the ECG timing signal, sequencing the pressure signals into pressure signals of separate ones of the at least one cardiac cycle based on an identification of the R-wave, sequencing the volume signals into volume signals of the separate ones of the at least one cardiac cycle based on the identification of the R-wave, group averaging the pressure signals of the separate ones of the at least one cardiac cycle to produce a mean pressure, group averaging the volume signals of the separate ones of the at least one cardiac cycle to produce a mean volume, identifying an occurrence of end-ejection based on one of the volume signal from the step of measuring the volume and the pressure signal from the step of measuring the blood pressure, determining a time interval tmax between an occurrence of the R-wave and the occurrence of end-ejection, calculating an absolute time t based on the normalized time tN according to an equation t=tN ×
tmax,determining a pressure at time t, P(t), and a pressure at time tmax, P(tmax), based on the mean pressure, determining a volume at time t, V(t), and a volume at time tmax, V(tmax), based on the mean volume, determining a normalized pressure PN (tN) based on the P(t) and the P(tmax), calculating a normalized elastance function for the time tN, EN (tN), based on a stored mean elastance function, calculating a volume-axis intercept V0(SB) of the ESPVR based on an equation ##EQU8## and calculating a slope Emax(SB) according to an equation
space="preserve" listing-type="equation">E.sub.max(SB) =P(t.sub.max)/[V(t.sub.max)-V.sub.0(SB) ].25. - View Dependent Claims (25, 26, 27)
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28. A method of determining an end-systolic pressure-volume relationship (ESPVR) of a human heart, comprising steps of:
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measuring a blood pressure of a left ventricle of the heart and producing a pressure signal indicative thereof; measuring a volume of the left ventricle and producing a volume signal indicative thereof; monitoring the heart to produce ECG timing signals indicative of its activity; analyzing the pressure, the volume and the timing signals based on a previously determined model of normalized elastance function for a normalized time tN to determine the ESPVR; and displaying the ESPVR, wherein the method further comprises; determining a time interval t between an R-wave of the ECG signal and an onset of blood ejection from the heart'"'"'s left ventricle; determining a time interval tmax measured between the R-wave of the ECG signal and a termination of the blood ejection from the heart'"'"'s left ventricle, wherein the step of analyzing the pressure, the volume, and the ECG timing signals comprises; recording the blood pressure signal, the blood pressure signal including aortic systolic AO PSYS and diastolic AO PDIA blood pressures, recording the volume signal, the volume signal including ventricular end-diastolic EDV and end-systolic ESV volumes, calculating a normalized time tN from an equation
space="preserve" listing-type="equation">t.sub.N =t/t.sub.max,calculating a normalized elastance function for the time tN, EN (tN), based on a stored mean elastance function; estimating a volume-axis intercept V0(SB) of the ESPVR based on an equation ##EQU9## estimating a slope Emax(SB) based on an equation
space="preserve" listing-type="equation">E.sub.max(SB)-AOP =(0.9×
A.sub.o P.sub.SYS)/(ESV-V.sub.0(SB)),wherein the onset and the termination of the blood ejection are determined by one of M-mode echocardiography and by initiation and termination of a proximal aortic Doppler flow waveform. - View Dependent Claims (29)
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30. An apparatus for determining an end-systolic pressure-volume relationship (ESPVR), comprising:
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a blood pressure monitor for measuring a blood pressure of a left ventricle of a human heart and producing a pressure signal indicative thereof; a volume measurement system for measuring a volume of the left ventricular chamber and producing a volume signal indicative thereof; an electrocardiograph monitor for monitoring the human heart and producing an ECG signal of the human heart; a computer for receiving the pressure signal, the volume signal, and the ECG signal, the computer including; means for determining the ESPVR based upon the pressure, the volume, and a timing derived from the ECG signal and determining the ESPVR, wherein the determining means comprises; means for recording the pressure signal and the volume signal over a plurality of cardiac cycles, means for identifying an R-wave of the ECG timing signal, means for sequencing the pressure signals into pressure signals of separate ones of the plurality of cardiac cycles based on an identification of the R-wave, means for sequencing the volume signals into volume signals of the separate ones of the plurality of cardiac cycles based on the identification of the R-wave, means for group averaging the pressure signals of the separate ones of the plurality of cardiac cycles to produce a mean pressure, means for group averaging the volume signals of the separate ones of the plurality of cardiac cycles to produce a mean volume, means for identifying an occurrence of end-ejection based on one of the volume signal from the step of measuring the volume and the pressure signal from the step of measuring the blood pressure, means for determining a time interval tmax between an occurrence of the R-wave and the occurrence of end-ejection, means for calculating an absolute time t based on a normalized time tN according to an equation t=tN ×
tmax,means for determining a pressure at time t, P(t), and a pressure at time tmax, P(tmax), based on the mean pressure, means for determining a volume at time t, V(t), and a volume at time tmax, V(tmax), based on the mean volume, means for determining a normalized pressure PN (tN) based on the P(t) and the P(tmax), means for calculating a normalized elastance function for the time tN, EN (tN), based on a stored mean elastance function, means for calculating a volume-axis intercept V0(SB) of the ESPVR based on an equation ##EQU10## means for calculating a slope Emax(SB) according to an equation
space="preserve" listing-type="equation">E.sub.max(SB) =P(t.sub.max)/[V(t.sub.max)-V.sub.0(SB) ].31.
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31. An apparatus for determining an end-systolic pressure-volume relationship (ESPVR), comprising:
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a blood pressure monitor for measuring a blood pressure of a left ventricle of a human heart and producing a pressure signal indicative thereof; a volume measurement system for measuring a volume of the left ventricular chamber and producing a volume signal indicative thereof; an electrocardiograph monitor for monitoring the human heart and producing an ECG signal of the human heart; a computer for receiving the pressure signal, the volume signal, and the ECG signal, the computer including; means for determining the ESPVR based upon the pressure, the volume, and a timing derived from the ECG signal and determining the ESPVR, wherein the determining means comprises; means for recording the blood pressure signal, the blood pressure signal including aortic systolic AO PSYS and diastolic AO PDIA blood pressures, means for recording the volume signal, the volume signal including ventricular end-diastolic EDV and end-systolic ESV volumes, means for calculating a normalized time tN from an equation tN =t/tmax, where a time interval t is determined by the volume measurement system and the electrocardiograph monitor to be between an R-wave of the ECG signal and an onset of blood ejection from the heart'"'"'s left ventricle, and is input to the computer, a time interval tmax is determined by the volume measurement system and the electrocardiograph monitor to be between the R-wave of the ECG signal and a termination of the blood ejection from the heart'"'"'s left ventricle, and is input to the computer, means for calculating a normalized elastance function for the time tN, EN (tN), based on a stored mean elastance function, means for estimating a volume-axis intercept V0(SB) of the ESPVR based on an equation ##EQU11## means for estimating a slope Emax(SB) based on an equation
space="preserve" listing-type="equation">E.sub.max(SB)-AOP =(0.9×
A.sub.o P.sub.SYS)/(ESV-V.sub.0(SB)).
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Specification