Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-05-22
2002-01-01
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S500000, C600S508000
Reexamination Certificate
active
06334849
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heart-function monitor apparatus which monitors a function of the heart of a living subject by evaluating a blood-outputting ability of the left ventricle of the heart.
2. Related Art Statement
When a characteristic of the left ventricle of the heart as an elastic tube, that is, an elastic coefficient of the same, at a telesystolic time immediately before the aortic valve is closed, is defined as a left-ventricle telesystolic elastance E
es
, the elastance E
es
indicates a blood-outputting ability of the left ventricle. Accordingly, the elastance E
es
can be used as an important index of the function of the heart. For example, the elastance E
es
can be used as a quantitative index of the dynamic condition of the circulatory system of a patient under intensive care or anesthesia.
However, determination of the above left-ventricle telesystolic elastance E
es
, which is also known as the maximum pressure-volume ratio, or the left-ventricle telesystolic pressure-volume ratio, needs (a) detecting continuously respective changes of the inner pressure and inner volume of the left ventricle, (h) obtaining, in a two-dimensional coordinate system having a volume axis indicative of the inner volume of the left ventricle and a pressure axis indicative of the inner pressure of the same, a plurality of pressure-volume loops before and after preload or afterload is applied to the cardiac muscle, (c) estimating, based on the plurality of pressure-volume loops, a left-ventricle unstressed volume, V
0
, taken when the inner pressure would take zero, and (d) determining the telesystolic elastance E
es
by dividing a telesystolic pressure, P
es
, by the difference of a telesystolic volume, V
es
, and the unstressed volume V
0
. Thus, the determination of the telesystolic elastance E
es
needs measuring simultaneously the inner pressure and inner volume of the left ventricle. Conventionally, this determination has been carried out by an invasive method in which a cutting operation or a catheter insertion is needed. Thus, it has been very difficult to monitor the cardiac function.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a heart-function monitor apparatus which can non-invasively and easily monitor a left-ventricle telesystolic elastance E
es
of a living subject.
The Inventor has carried out extensive studies in the above-mentioned background, and has found the fact that when (a) a pressure-volume ratio, E(t), is obtained by dividing a continuously obtained left-ventricle inner pressure, P(t), by the difference, (V(t)−V
0
), of a continuously obtained left-ventricle inner volume, V(t), and the above-indicated unstressed volume V
0
, (b) a time-and-pressure-volume-ratio curve is drawn, as shown in
FIG. 8
, in a two-dimensional coordinate system having a time axis and a pressure-volume-ratio axis, (c) a first portion of a length of the time-and-pressure-volume-ratio curve between its start end and a maximum pressure-volume ratio, E
max
, i.e., a left-ventricle telesystolic elastance E
es
(the first portion corresponds to a pre-ejection period, PEP) is approximated by a straight line, L
1
, and a second portion of the length (the second portion corresponds to an ejection period, ET) is approximated by a straight line, L
2
, and (d) &agr;
0
is defined as being equal to the ratio, &agr;
2
/&agr;
1
, of a slope, &agr;
2
, of the straight line L
2
to a slope, &agr;
1
, of the straight line L
1
, the left-ventricle telesystolic elastance E
es
can be expressed by using a telediastolic aorta (blood) pressure, P
ad
, i.e., an aorta inner pressure at a telediastolic time of the heart; a telesystolic aorta pressure P
es
, i.e., an aorta inner pressure at a telesystolic time of the heart; the ejection period ET and the pre-ejection period PEP of the left ventricle; a stroke volume, SV, i.e., a volume of the blood outputted by one beat of the left ventricle; a telediastolic left-ventricle pressure, P
ed
, i.e., a left-ventricle inner pressure at the telediastolic time of the heart; and the ratio &agr;
0
. The present invention has been developed based on this finding.
(1) According to a first feature of the present invention, there is provided an apparatus for monitoring a function of a heart of a living subject, comprising a pre-ejection period measuring device which non-invasively measures a pre-ejection period from a time when contraction of a cardiac muscle of a left ventricle of the heart starts, to a time when ejection of blood from the left ventricle starts; an ejection-period measuring device which non-invasively measures an ejection period during which the blood is ejected from the left ventricle; an aorta-pressure estimating means for estimating blood pressure values in an aorta of the subject; a telediastolic-aorta-pressure determining means for determining, based on the aorta blood pressure values estimated by the aorta-pressure estimating means, a telediastolic blood pressure in the aorta at a telediastolic time of the heart; a telesystolic-aorta-pressure determining means for determining, based on the aorta blood pressure values estimated by the aorta-pressure estimating means, a telesystolic blood pressure in the aorta at a telesystolic time of the heart; a stroke-volume measuring device which non-invasively measures a stroke volume that is a volume of blood ejected from the left ventricle of the heart by a one-time beat of the heart; and a telesystolic-elastance determining means for determining, based on the measured pre-ejection period, the measured ejection period, the determined aorta telediastolic blood pressure, the determined aorta telesystolic blood pressure, and the measured stroke volume, a telesystolic elastance of the left ventricle of the heart, according to a predetermined relationship between (A) left-ventricle telesystolic elastance and (B) (b
1
) pre-ejection period, (b
2
) ejection period, (b
3
) aorta telediastolic blood pressure, (b
4
) aorta telesystolic blood pressure, and (b
5
) stroke volume.
According to this feature, the telesystolic-elastance determining means determines, based on the pre-ejection period, the ejection period, the telediastolic aorta blood pressure, the telesystolic aorta blood pressure, and the stroke volume all of which are non-invasively measured or determined, a telesystolic (i.e., end-systolic) elastance of the left ventricle of the heart of the subject, according the predetermined relationship. Thus, the present heart-function monitor apparatus can non-invasively and easily monitor the left ventricular end-systolic elastance corresponding to the cardiac function of the subject.
(2) According to a second feature of the present invention that includes the first feature (1), the telesystolic-elastance determining means comprises means for determining, according the predetermined relationship, the telesystolic elastance of the left ventricle of the heart, based on the measured pre-ejection period, the measured ejection period, the determined aorta telediastolic blood pressure, the determined aorta telesystolic blood pressure, the measured stroke volume, and a predetermined telediastolic (i.e., end-diastolic) pressure in the left ventricle at the telediastolic time of the heart. The left ventricular end-diastolic pressure is, e.g., 10 mmHg, but may be non-invasively estimated by the present monitor apparatus.
(3) According to a third feature of the present invention that includes the second feature (2), the predetermined relationship is defined by a following expression:
E
es
=[P
ad
+{(
P
ad
−P
ed
)/
PEP}×ET×&agr;
0
−P
es
]/SV
where
E
es
is the left-ventricle telesystolic elastance,
P
ad
is the aorta telediastolic blood pressure,
P
es
is the aorta telesystolic blood pressure,
P
ed
is the left-ventricle telediastolic pressure,
ET is the ejection period,
PEP is the pre-ejection period,
SV is the stroke volume, and
&agr;
0
is a coefficient.
The abov
Colin Corporation
Natnithithadha Navin
Oliff & Berridg,e PLC
Winakur Eric F.
LandOfFree
Heart-function monitor apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heart-function monitor apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heart-function monitor apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2825242