U.S. patent application number 17/468118 was filed with the patent office on 2021-12-30 for devices, systems, and methods to evaluate cardiovascular function.
This patent application is currently assigned to CVDevices, LLC. The applicant listed for this patent is CVDevices, LLC. Invention is credited to Ghassan S. Kassab.
Application Number | 20210401318 17/468118 |
Document ID | / |
Family ID | 1000005825778 |
Filed Date | 2021-12-30 |
United States Patent
Application |
20210401318 |
Kind Code |
A1 |
Kassab; Ghassan S. |
December 30, 2021 |
DEVICES, SYSTEMS, AND METHODS TO EVALUATE CARDIOVASCULAR
FUNCTION
Abstract
Methods of determining an index of vessel and heart function are
disclosed. The methods determine the maximum volume and rate of
change of volume so that an efficiency of the heart can be
determined. Conductance readings indicative of the heart can be
taken from a variety of locations such as the lumen of a vessel,
the lumen of a heart, the pericardial space, and the epicardial
surface. Said conductance readings are then used to determine the
efficiency of the heart.
Inventors: |
Kassab; Ghassan S.; (La
Jolla, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CVDevices, LLC |
San Diego |
CA |
US |
|
|
Assignee: |
CVDevices, LLC
San Diego
CA
|
Family ID: |
1000005825778 |
Appl. No.: |
17/468118 |
Filed: |
September 7, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16365379 |
Mar 26, 2019 |
11109772 |
|
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17468118 |
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12521258 |
Jun 25, 2009 |
10238311 |
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PCT/US08/00739 |
Jan 22, 2008 |
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16365379 |
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60881841 |
Jan 23, 2007 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/0538 20130101;
A61B 5/053 20130101 |
International
Class: |
A61B 5/053 20060101
A61B005/053; A61B 5/0538 20060101 A61B005/0538 |
Claims
1. A method of determining an index of heart function, the method
comprising the steps of: positioning an impedance device at a heart
location selected from the group consisting of: a pericardial space
on a surface of the heart, a lumen of the heart, or an epicardial
surface of the heart; measuring a conductance at the heart location
during a cardiac cycle using the impedance device; and generating
an efficiency model of the heart from the conductance, wherein the
conductance comprises parallel conductance.
2. The method of claim 1, wherein the step of measuring the
conductance during the cardiac cycle further comprises the step of
obtaining a parallel conductance measurement.
3. The method of claim 1, wherein the step of measuring a
conductance during a cardiac cycle further comprises the step of
measuring a change in conductance; and the step of generating an
efficiency model of the heart further comprises the step of
generating an efficiency model of the heart from the measurement of
the change in conductance.
4. The method of claim 3, further comprising the step of
calculating a max rate of change of a cross sectional area of the
heart based on the change in conductance; and wherein the step of
generating an efficiency model of the heart further comprises
generating an efficiency model of the heart from the calculated max
rate of change of the cross sectional area.
5. The method of claim 1, wherein the step of generating an
efficiency model further comprises the step of comparing the
conductance to a rate of volumetric change of the heart.
6. The method of claim 1, wherein the step of measuring a
conductance comprises multiple conductance measurements to
determine the volume of the heart.
7. The method of claim 1, wherein the step of generating an
efficiency model further comprises the step of evaluating the
maximum rate of volumetric change of the heart.
8. A method of determining an index of heart function, the method
comprising the steps of: positioning an impedance device directly
onto an epicardial surface of the heart, the impedance device
comprising a first excitation electrode, a second excitation
electrode, a first detection electrode, and a second detection
electrode; measuring a conductance during a cardiac cycle from the
epicardial surface of the heart using the impedance device; and
generating an efficiency model of the heart from the conductance,
wherein the conductance comprises parallel conductance.
9. The method of claim 8, wherein the step of measuring the
conductance during the cardiac cycle further comprises the step of
obtaining a parallel conductance measurement.
10. The method of claim 8, wherein the step of measuring a
conductance during a cardiac cycle further comprises the step of
measuring a change in conductance; and the step of generating an
efficiency model of the heart further comprises the step of
generating an efficiency model of the heart from the measurement of
the change in conductance.
11. The method of claim 10, further comprising the step of
calculating a max rate of change of a cross sectional area of the
heart based on the change in conductance; and wherein the step of
generating an efficiency model of the heart further comprises
generating an efficiency model of the heart from the calculated max
rate of change of the cross sectional area.
12. The method of claim 8, wherein the step of generating an
efficiency model further comprises the step of comparing the
conductance to a rate of volumetric change of the heart.
13. The method of claim 8, wherein the step of measuring a
conductance comprises multiple conductance measurements to
determine the volume of the heart.
14. The method of claim 8, wherein the step of generating an
efficiency model further comprises the step of evaluating the
maximum rate of volumetric change of the heart.
15. A method of determining an index of vessel function, the method
comprising the steps of: introducing an impedance device into a
lumen of a vessel; measuring a conductance from the lumen of the
vessel during a cardiac cycle using the impedance device; and
generating an efficiency model of the heart from the conductance,
wherein the conductance measurement comprises a parallel
conductance.
16. The method of claim 15 wherein the step of measuring the
conductance during the cardiac cycle further comprises the step of
obtaining a parallel conductance measurement.
17. The method of claim 1, wherein the step of measuring a
conductance during a cardiac cycle further comprises the step of
measuring a change in conductance; and the step of generating an
efficiency model of the heart further comprises the step of
generating an efficiency model of the heart from the measurement of
the change in conductance.
18. The method of claim 17, further comprising the step of
calculating a max rate of change of a cross sectional area of the
heart based on the change in conductance; and wherein the step of
generating an efficiency model of the heart further comprises
generating an efficiency model of the heart from the calculated max
rate of change of the cross sectional area.
19. The method of claim 15, wherein the step of generating an
efficiency model further comprises the step of comparing the
conductance to a rate of volumetric change of the heart.
20. The method of claim 15, wherein the step of generating an
efficiency model further comprises the step of evaluating the
maximum rate of volumetric change of the heart.
Description
PRIORITY
[0001] The present application is related to, claims the priority
benefit of, and is a continuation patent application of, U.S.
patent application Ser. No. 16/365,379 filed on Mar. 26, 2019 and
issued as U.S. Pat. No. 11,109,772 on Sep. 7, 2021, which is
related to, claims the priority benefit of, and is a continuation
patent application of, U.S. patent application Ser. No. 12/521,258,
filed Jun. 25, 2009 and issued as U.S. Pat. No. 10,238,311 on Mar.
26, 2019, which is related to, claims the priority benefit of, and
is a U.S. .sctn. 371 national phase application of, International
Patent Application Serial No. PCT/US2008/000739, filed Jan. 22,
2008, which is related to, and claims the priority benefit of, U.S.
Provisional Patent Application Ser. No. 60/881,841, filed Jan. 23,
2007. The contents of each of the aforementioned applications are
incorporated herein directly and by reference in their
entirety.
BACKGROUND
[0002] The disclosure of the present application relates generally
to vessel and heart efficiency and risk of disease. More
particularly, the disclosure of the present application relates to
techniques for evaluating cardiovascular function.
[0003] Many cardiovascular diseases, including diabetes,
hypertension, and heart failure, have impaired arterial
vasoactivity, namely vasoconstriction and vasodilation.
Hypertension, for example, is associated with changes in vasomotor
tone and typically attenuates vasodilation. The vasoactivity may
also be altered under physiological conditions, such as in normal
growth, exercise, etc. The regulation of the vasomotor tone in
medium-sized arteries is of particular interest because of the
clinical relevance to vasospasm and atherosclerosis.
[0004] In addition to the active component (vasoactivity) of blood
vessels, there is great interest in the elasticity of vessels. One
of the reasons for the great interest stems from the observation
that increased stiffness of large elastic arteries represents an
early risk factor for cardiovascular diseases. Specifically,
increased aortic stiffness is associated with aging, hypertension,
diabetes, hyperlipidemia, atherosclerosis, heart failure, and
smoking. Furthermore, arterial stiffness has also been shown to be
an independent risk factor for cardiovascular events such as
primary coronary events, stroke, and mortality. Therefore, the
assessment of the passive and active mechanical properties of
vessels is particularly important for understanding the mechanisms
of cardiovascular disease.
[0005] Clinically, the compliance or stiffness of blood vessels is
used as an index of vascular mechanics, and hence, vessel function.
These measurements can be made from imaging (e.g., ultrasound) to
obtain the deformation (change of dimension) and loading
(pressure). The endothelial function is typically measured by the
degree of vasodilation or reactive hyperemia (namely the change of
diameter from imaging) post cuff occlusion. Unfortunately, these
measurements can be quite variable and the theoretical basis for
the measurements is not well founded. Hence, there is a need to
determine a theoretically-based parameter that quantifies the
function of blood vessels.
[0006] Regarding the heart, much effort has gone into quantifying
myocardial function, independent of ventricular loading conditions.
In the left ventricle (LV), the peak first time-derivative of LV
intracavitary pressure, dP/dt.sub.max, is a sensitive cardiac index
of inotropicity and the current detection `gold standard.`
Currently, the ability to obtain an accurate determination of
dP/dt.sub.max requires measurement of intraventricular LV pressure
using invasive cardiac catheterization. In general, it is very
difficult to accurately assess ventricular pressure
non-invasively.
[0007] An additional difficulty with LV dP/dt.sub.max is that it is
not preload-independent. Conceivably, LV pressure-volume
relationship and elastance reflect LV contractile function more
accurately formalized as the time-varying elastance of the
ventricle, by defining elastance, E. Elastance is defined as
E(t)=P(t)/(V(t)-V.sub.d), where P(t) and V(t) are ventricular
pressure and volume that vary with time (t), respectively. V.sub.d
is the LV volume corresponding to zero LV pressure obtained by
drawing a tangent to the pressure-volume curves at the
end-ejection.
[0008] It has been shown that the end-systolic pressure volume
(ESPV) relationship, which is the loci of pressure and volume
points at end-systole, is insensitive to variations of both the
end-diastolic volume (preload) and the mean arterial pressure
(afterload). The ESPV relationship is usually a straight line with
a slope of E.sub.es. It is found that arterial pressure
(afterload). The ESPV relationship is usually a straight line with
a slope of E.sub.es remains essentially constant if the preload and
afterload are allowed to vary within the physiologic range, but is
sensitive to inotropic agents and ischemia. Hence, arterial
pressure (afterload). The ESPV relationship is usually a straight
line with a slope of E.sub.es has been proposed as a "load
independent" index of contractility of the ventricle. Elastance
measures also require cardiac catheterization for measurement of
pressure which further reduces their clinical utility. An
additional limitation of arterial pressure (afterload). The ESPV
relationship is usually a straight line with a slope of E.sub.es is
that it is not easy to change afterload and obtain multiple
pressure-volume data points in a given subject while maintaining a
constant contractility. As such, it is impractical to use arterial
pressure (afterload). The ESPV relationship is usually a straight
line with a slope of E.sub.es clinically for patient-specific LV
catheterization-ventriculography data. Hence, there is a need for a
cardiac index that is more readily accessible and practical.
BRIEF SUMMARY
[0009] The disclosure of the present application measures an index
of vessel and heart function to evaluate the efficiency of the
cardiovascular system and risk of disease. The measurements are
taken with an impedance catheter. The catheter may be inserted into
the lumen of the vessel or heart chamber. Alternatively, the
catheter may be inserted into the pericardial space or directly
placed on the heart as during open heart surgery. A patch
containing the excitation and detection electrodes can be made to
adhere to the surface through glue that is introduced through the
lumen of the catheter into pores of the patch if the percutaneous
approach is used. Alternatively, the patch may be glued on by hand
with the open surgery approach. The electrodes are then interfaced
with an impedance module to measure voltage differences. The
voltage differences are then either compared to an average model,
or combined with other measurements to create an average model.
[0010] In at least one embodiment of a device for determining the
index of a heart and/or vessel function according to the present
disclosure, the device comprises an impedance catheter comprising a
patch, the patch comprising a first excitation electrode, a second
excitation electrode, a first detection electrode, and a second
detection electrode, and a conductance reader in connection with
the catheter, the conductance reader operable to detect conductance
from the first detection electrode and the second detection
electrode, whereby an assessment of the index of a heart and/or
vessel function may be determined based upon the conductance
detected from the first detection electrode and the second
detection electrode. In another embodiment, the conductance reader
comprises a data acquisition and processing system. In yet another
embodiment, the data acquisition and processing system comprises a
processor, a storage medium operably connected to the processor,
the storage medium capable of receiving and storing conductance
data, and a program stored upon the storage medium, the program
operable by the processor upon the conductance data to compare the
conductance data to a rate of volumetric change of a heart and/or
vessel.
[0011] In at least one embodiment of a device for determining the
index of a heart and/or vessel function according to the present
disclosure, the processor compares the conductance data from
conductance acquired from the epicardial surface of a heart. In
another embodiment, the processor compares the conductance data
from conductance acquired from the lumen surface of a heart. In yet
another embodiment, the conductance reader comprises a parallel
conductance reader, and wherein the parallel conductance reader is
operable to detect parallel conductance. In an additional
embodiment, the parallel conductance reader comprises a data
acquisition and processing system. In another embodiment, the data
acquisition and processing system comprises a processor, a storage
medium operably connected to the processor, the storage medium
capable of receiving and storing parallel conductance data, and a
program stored upon the storage medium, the program operable by the
processor upon the parallel conductance data to compare the
parallel conductance data to a rate of volumetric change of a heart
and/or vessel.
[0012] In at least one embodiment of a device according to the
present disclosure, the processor compares the parallel conductance
data from parallel conductance acquired from the epicardial surface
of a heart. In a further embodiment, the processor compares the
parallel conductance data from parallel conductance acquired from
the lumen surface of a heart. In another embodiment, the patch is
positioned upon the epicardial surface of a heart, and wherein the
conductance reader is operable to detect conductance from the
epicardial surface of the heart. In yet another embodiment, the
patch is positioned upon the lumen surface of a heart, and wherein
the conductance reader is operable to detect conductance from the
lumen surface of the heart. In an additional embodiment, the patch
is positioned upon the epicardial surface of a heart, and wherein
the parallel conductance reader is operable to detect parallel
conductance from the epicardial surface of the heart.
[0013] In at least one embodiment of a device for determining the
index of a heart and/or vessel function according to the present
disclosure, the patch is positioned upon the lumen surface of a
heart, and wherein the parallel conductance reader is operable to
detect parallel conductance from the lumen surface of the heart. In
another embodiment, the processor is operable to evaluate the
maximum rate of volumetric change of the heart. In yet another
embodiment, the processor is operable to evaluate the maximum rate
of volumetric change of the heart. In an additional embodiment, the
wherein the processor compares the conductance data from
conductance acquired from the outer surface of a vessel.
[0014] In at least one embodiment of a device for determining the
index of a heart and/or vessel function according to the present
disclosure, the processor compares the conductance data from
conductance acquired from the lumen surface of a vessel. In another
embodiment, the processor compares the parallel conductance data
from parallel conductance acquired from the outer surface of a
vessel. In yet another embodiment, the processor compares the
parallel conductance data from parallel conductance acquired from
the lumen surface of a vessel. In an additional embodiment, the
patch is positioned upon the epicardial surface of a vessel, and
wherein the conductance reader is operable to detect conductance
from the epicardial surface of the vessel.
[0015] In at least one embodiment of a device for determining the
index of a heart and/or vessel function according to the present
disclosure, the patch is positioned upon the lumen surface of a
vessel, and wherein the conductance reader is operable to detect
conductance from the lumen surface of the vessel. In another
embodiment, the patch is positioned upon the epicardial surface of
a vessel, and wherein the parallel conductance reader is operable
to detect parallel conductance from the epicardial surface of the
vessel. In yet another embodiment, the patch is positioned upon the
lumen surface of a vessel, and wherein the parallel conductance
reader is operable to detect parallel conductance from the lumen
surface of the vessel. In an additional embodiment, the processor
is operable to evaluate the maximum rate of lumen cross-sectional
area change of a vessel. In a further embodiment, the processor is
operable to evaluate the maximum rate of lumen cross-sectional area
change of a vessel.
[0016] In at least one embodiment of a device for determining the
index of a heart and/or vessel function according to the present
disclosure, the device further comprises a current source, the
current source operable to provide a supply of electrical current
to the first excitation electrode and the second excitation
electrode to facilitate the detection of conductance from the first
detection electrode and the second detection electrode. In another
embodiment, the device further comprises a current source, the
current source operable to provide a supply of electrical current
to the first excitation electrode and the second excitation
electrode to facilitate the detection of parallel conductance from
the first detection electrode and the second detection electrode.
In yet another embodiment, the first excitation electrode, the
second excitation electrode, the first detection electrode, and the
second detection electrode each comprise a wire, and wherein each
wire is insulated from the other wires.
[0017] In at least one embodiment of a device for determining the
index of a heart and/or vessel function according to the present
disclosure, the device comprises an impedance catheter comprising a
patch, the patch comprising a first excitation electrode, a second
excitation electrode, a first detection electrode, and a second
detection electrode, and a conductance reader in connection with
the catheter, the conductance reader operable to detect conductance
from the first detection electrode and the second detection
electrode, wherein the conductance reader comprises a data
acquisition and processing system comprising a processor, a storage
medium operably connected to the processor, the storage medium
capable of receiving and storing conductance data, and a program
stored upon the storage medium, the program operable by the
processor upon the conductance data to compare the conductance data
to a rate of volumetric change of a heart and/or vessel, whereby an
assessment of the index of a heart and/or vessel function may be
determined based upon the conductance detected from the first
detection electrode and the second detection electrode.
[0018] In at least one embodiment of a device for determining the
index of a heart and/or vessel function according to the present
disclosure, the device comprises an impedance catheter comprising a
patch, the patch comprising a first excitation electrode, a second
excitation electrode, a first detection electrode, and a second
detection electrode, and a parallel conductance reader in
connection with the catheter, the parallel conductance reader
operable to detect parallel conductance from the first detection
electrode and the second detection electrode, wherein the parallel
conductance reader comprises a data acquisition and processing
system comprising a processor, a storage medium operably connected
to the processor, the storage medium capable of receiving and
storing parallel conductance data, and a program stored upon the
storage medium, the program operable by the processor upon the
parallel conductance data to compare the parallel conductance data
to a rate of volumetric change of a heart and/or vessel, whereby an
assessment of the index of a heart and/or vessel function may be
determined based upon the parallel conductance detected from the
first detection electrode and the second detection electrode.
[0019] In at least one embodiment of a system for determining the
index of a heart and/or vessel function according to the present
disclosure, the system comprises an impedance catheter assembly,
the impedance catheter assembly comprising a catheter, the catheter
comprising a patch, and a conductance reader in connection with the
catheter assembly, the conductance reader operable to detect
conductance from the impedance catheter assembly, whereby an
assessment of the index of a heart and/or vessel function may be
determined based upon the conductance detected from the catheter
assembly. In another embodiment, the patch comprises a first
excitation electrode, a second excitation electrode, a first
detection electrode, and a second detection electrode. In yet
another embodiment, the conductance reader is operable to detect
conductance from the first detection electrode and the second
detection electrode, and whereby the assessment of the index of a
heart and/or vessel function may be determined based upon the
conductance detected from the first detection electrode and the
second detection electrode.
[0020] In at least one embodiment of a system according to the
present disclosure, the conductance reader comprises a data
acquisition and processing system. In another embodiment, the data
acquisition and processing system comprises a processor, a storage
medium operably connected to the processor, the storage medium
capable of receiving and storing conductance data, and a program
stored upon the storage medium, the program operable by the
processor upon the conductance data to compare the conductance data
to a rate of volumetric change of a heart and/or vessel. In an
additional embodiment, the processor compares the conductance data
from conductance acquired from the epicardial surface of a heart.
In a further embodiment, the processor compares the conductance
data from conductance acquired from the lumen surface of a
heart.
[0021] In at least one embodiment of a system for determining the
index of a heart and/or vessel function according to the present
disclosure, the conductance reader comprises a parallel conductance
reader, and wherein the parallel conductance reader is operable to
detect parallel conductance. In another embodiment, the parallel
conductance reader comprises a data acquisition and processing
system. In yet another embodiment, the data acquisition and
processing system comprises a processor, a storage medium operably
connected to the processor, the storage medium capable of receiving
and storing parallel conductance data, and a program stored upon
the storage medium, the program operable by the processor upon the
parallel conductance data to compare the parallel conductance data
to a rate of volumetric change of a heart and/or vessel. In an
additional embodiment, the processor compares the parallel
conductance data from parallel conductance acquired from the
epicardial surface of a heart. In yet an additional embodiment, the
processor compares the parallel conductance data from parallel
conductance acquired from the lumen surface of a heart.
[0022] In at least one embodiment of a system for determining the
index of a heart and/or vessel function according to the present
disclosure, the patch is positioned upon the epicardial surface of
a heart, and wherein the conductance reader is operable to detect
conductance from the epicardial surface of the heart. In another
embodiment, the patch is positioned upon the lumen surface of a
heart, and wherein the conductance reader is operable to detect
conductance from the lumen surface of the heart. In even another
embodiment, the patch is positioned upon the epicardial surface of
a heart, and wherein the parallel conductance reader is operable to
detect parallel conductance from the epicardial surface of the
heart. In yet another embodiment, the patch is positioned upon the
lumen surface of a heart, and wherein the parallel conductance
reader is operable to detect parallel conductance from the lumen
surface of the heart.
[0023] In at least one embodiment of a system for determining the
index of a heart and/or vessel function according to the present
disclosure, the processor is operable to evaluate the maximum rate
of volumetric change of the heart. In another embodiment, the
processor is operable to evaluate the maximum rate of volumetric
change of the heart. In yet another embodiment, the processor
compares the conductance data from conductance acquired from the
outer surface of a vessel.
[0024] In at least one embodiment of a system according to the
present disclosure, the processor compares the conductance data
from conductance acquired from the lumen surface of a vessel. In
another embodiment, the processor compares the parallel conductance
data from parallel conductance acquired from the outer surface of a
vessel. In yet another embodiment, the processor compares the
parallel conductance data from parallel conductance acquired from
the lumen surface of a vessel.
[0025] In at least one embodiment of a system for determining the
index of a heart and/or vessel function according to the present
disclosure, the patch is positioned upon the epicardial surface of
a vessel, and wherein the conductance reader is operable to detect
conductance from the epicardial surface of the vessel. In another
embodiment, the patch is positioned upon the lumen surface of a
vessel, and wherein the conductance reader is operable to detect
conductance from the lumen surface of the vessel. In yet another
embodiment, the patch is positioned upon the epicardial surface of
a vessel, and wherein the parallel conductance reader is operable
to detect parallel conductance from the epicardial surface of the
vessel.
[0026] In at least one embodiment of a system according to the
present disclosure, the patch is positioned upon the lumen surface
of a vessel, and wherein the parallel conductance reader is
operable to detect parallel conductance from the lumen surface of
the vessel. In an additional embodiment, the processor is operable
to evaluate the maximum rate of lumen cross-sectional area change
of a vessel. In yet an additional embodiment, the processor is
operable to evaluate the maximum rate of lumen cross-sectional area
change of a vessel.
[0027] In at least one embodiment of a system according to the
present disclosure, the system further comprises a current source,
the current source operable to provide a supply of electrical
current to the first excitation electrode and the second excitation
electrode to facilitate the detection of conductance from the first
detection electrode and the second detection electrode. In another
embodiment, the system further comprises a current source, the
current source operable to provide a supply of electrical current
to the first excitation electrode and the second excitation
electrode to facilitate the detection of parallel conductance from
the first detection electrode and the second detection electrode.
In yet another embodiment, the first excitation electrode, the
second excitation electrode, the first detection electrode, and the
second detection electrode each comprise a wire, and wherein each
wire is insulated from the other wires.
[0028] In at least one embodiment of a system for determining the
index of a heart and/or vessel function according to the present
disclosure, the system comprises an impedance catheter assembly,
the impedance catheter assembly comprising a catheter, the catheter
comprising a patch, the patch comprising a first excitation
electrode, a second excitation electrode, a first detection
electrode, and a second detection electrode, and a conductance
reader in connection with the catheter assembly, the conductance
reader operable to operable to detect conductance from the first
detection electrode and the second detection electrode, wherein the
conductance reader comprises a data acquisition and processing
system comprising a processor, a storage medium operably connected
to the processor, the storage medium capable of receiving and
storing conductance data, and a program stored upon the storage
medium, the program operable by the processor upon the conductance
data to compare the conductance data to a rate of volumetric change
of a heart and/or vessel, whereby an assessment of the index of a
heart and/or vessel function may be determined based upon the
conductance detected from the first detection electrode and the
second detection electrode.
[0029] In at least one embodiment of a system for determining the
index of a heart and/or vessel function according to the present
disclosure, the system comprises an impedance catheter assembly,
the impedance catheter assembly comprising a catheter, the catheter
comprising a patch, the patch comprising a first excitation
electrode, a second excitation electrode, a first detection
electrode, and a second detection electrode, and a parallel
conductance reader in connection with the catheter assembly, the
parallel conductance reader operable to operable to detect parallel
conductance from the first detection electrode and the second
detection electrode, wherein the parallel conductance reader
comprises a data acquisition and processing system comprising a
processor, a storage medium operably connected to the processor,
the storage medium capable of receiving and storing parallel
conductance data, and a program stored upon the storage medium, the
program operable by the processor upon the parallel conductance
data to compare the parallel conductance data to a rate of
volumetric change of a heart and/or vessel, whereby an assessment
of the index of a heart and/or vessel function may be determined
based upon the parallel conductance detected from the first
detection electrode and the second detection electrode.
[0030] In at least one embodiment of a program having a plurality
of program steps to be executed on a computer having a processor
and a storage medium to analyze conductance data according to the
present disclosure, the program is operable to receive conductance
data from a conductance reader, and analyze the conductance data to
determine the index of heart and/or vessel function. In another
embodiment, the program is further operable to evaluate the maximum
rate of volumetric change of the heart and/or vessel. In yet
another embodiment, the program is further operable to evaluate the
maximum rate of lumen cross-sectional area change of a vessel.
[0031] In at least one embodiment of a program having a plurality
of program steps to be executed on a computer having a processor
and a storage medium to analyze parallel conductance data according
to the present disclosure, the program is operable to receive
parallel conductance data from a parallel conductance reader, and
analyze the parallel conductance data to determine the index of
heart and/or vessel function. In an additional embodiment, the
program is further operable to evaluate the maximum rate of
volumetric change of the heart and/or vessel. In yet an additional
embodiment, the program is further operable to evaluate the maximum
rate of lumen cross-sectional area change of a vessel.
[0032] In at least one embodiment of a method of determining an
index of heart function according to the present disclosure, the
method comprises the steps of introducing an impedance catheter
into a pericardial space on the surface of a heart, measuring a
parallel conductance during a cardiac cycle, and generating an
efficiency model of the heart from the parallel conductance. In
another embodiment, the impedance catheter comprises a patch, the
patch comprising a first excitation electrode, a second excitation
electrode, a first detection electrode, and a second detection
electrode. In yet another embodiment, the step of measuring a
parallel conductance is performed by obtaining parallel conductance
from the first detection electrode and the second detection
electrode.
[0033] In at least one embodiment of a method of determining an
index of heart function according to the present disclosure, the
step of generating an efficiency model further comprises the step
of comparing the parallel conductance to a rate of volumetric
change of the heart. In another embodiment, the step of measuring a
parallel conductance comprises multiple parallel conductance
measurements to determine the volume of the heart. In yet another
embodiment, the step of measuring a parallel conductance comprises
the use of a parallel conductance reader operably coupled to the
impedance catheter. In even another embodiment, the step of
generating an efficiency model further comprises the step of
evaluating the maximum rate of volumetric change of the heart.
[0034] In at least one embodiment of a method of determining an
index of heart function according to the present disclosure, the
method comprises the steps of introducing an impedance catheter
into a pericardial space on the surface of a heart, measuring a
general conductance during a cardiac cycle, and generating an
efficiency model of the heart from the general conductance. In
another embodiment, the impedance catheter comprises a patch, the
patch comprising a first excitation electrode, a second excitation
electrode, a first detection electrode, and a second detection
electrode. In yet another embodiment, the step of measuring a
general conductance is performed by obtaining general conductance
from the first detection electrode and the second detection
electrode. In a further embodiment, the step of generating an
efficiency model further comprises the step of comparing the
general conductance to a rate of volumetric change of the
heart.
[0035] In at least one embodiment of a method of determining an
index of heart function according to the present disclosure, the
step of measuring a general conductance comprises multiple general
conductance measurements to determine the volume of the heart. In
another embodiment, the step of measuring a general conductance
comprises the use of a general conductance reader operably coupled
to the impedance catheter. In yet another embodiment, the step of
generating an efficiency model further comprises the step of
evaluating the maximum rate of volumetric change of the heart.
[0036] In at least one embodiment of a method of determining an
index of heart function according to the present disclosure, the
method comprises the steps of introducing an impedance catheter
into a lumen of a heart measuring a parallel conductance during a
cardiac cycle, and generating an efficiency model of the heart from
the parallel conductance. In another embodiment, the impedance
catheter comprises a patch, the patch comprising a first excitation
electrode, a second excitation electrode, a first detection
electrode, and a second detection electrode. In yet another
embodiment, the step of measuring a parallel conductance is
performed by obtaining parallel conductance from the first
detection electrode and the second detection electrode.
[0037] In at least one embodiment of a method of determining an
index of heart function according to the present disclosure, the
step of generating an efficiency model further comprises the step
of comparing the parallel conductance to a rate of volumetric
change of the heart. In another embodiment, the step of measuring a
parallel conductance comprises multiple parallel conductance
measurements to determine the volume of the heart. In even another
embodiment, the step of measuring a parallel conductance comprises
the use of a parallel conductance reader operably coupled to the
impedance catheter. In yet another embodiment, the step of
generating an efficiency model further comprises the step of
evaluating the maximum rate of volumetric change of the heart.
[0038] In at least one embodiment of a method of determining an
index of heart function according to the present disclosure, the
method comprises the steps of introducing an impedance catheter
into a lumen of a heart, measuring a general conductance during a
cardiac cycle, and generating an efficiency model of the heart from
the general conductance. In an additional embodiment, the impedance
catheter comprises a patch, the patch comprising a first excitation
electrode, a second excitation electrode, a first detection
electrode, and a second detection electrode. In yet an additional
embodiment, the step of measuring a general conductance is
performed by obtaining general conductance from the first detection
electrode and the second detection electrode.
[0039] In at least one embodiment of a method of determining an
index of heart function according to the present disclosure, the
step of generating an efficiency model further comprises the step
of comparing the general conductance to a rate of volumetric change
of the heart. In another embodiment, the step of measuring a
general conductance comprises multiple general conductance
measurements to determine the volume of the heart. In yet another
embodiment, the step of measuring a general conductance comprises
the use of a general conductance reader operably coupled to the
impedance catheter. In even another embodiment, the step of
generating an efficiency model further comprises the step of
evaluating the maximum rate of volumetric change of the heart.
[0040] In at least one embodiment of a method of determining an
index of vessel function according to the present disclosure, the
method comprises the steps of introducing an impedance catheter
into a lumen of a vessel, measuring a parallel conductance during a
cardiac cycle, and generating an efficiency model of the vessel
from the parallel conductance. In another embodiment, the impedance
catheter comprises a patch, the patch comprising a first excitation
electrode, a second excitation electrode, a first detection
electrode, and a second detection electrode. In yet another
embodiment, the step of measuring a parallel conductance is
performed by obtaining parallel conductance from the first
detection electrode and the second detection electrode.
[0041] In at least one embodiment of a method of determining an
index of vessel function according to the present disclosure, the
step of generating an efficiency model further comprises the step
of comparing the parallel conductance to a rate of volumetric
change of the vessel. In an additional embodiment, the step of
measuring a parallel conductance comprises a single parallel
conductance measurement. In another embodiment, the step of
measuring a parallel conductance comprises the use of a parallel
conductance reader operably coupled to the impedance catheter. In
yet another embodiment, the step of generating an efficiency model
further comprises the step of evaluating the maximum rate of
volumetric change of the vessel.
[0042] In at least one embodiment of a method of determining an
index of vessel function according to the present disclosure, the
method comprises the steps of introducing an impedance catheter
into a lumen of a vessel; measuring a general conductance during a
cardiac cycle, and generating an efficiency model of the vessel
from the general conductance.
[0043] In another embodiment, the impedance catheter comprises a
patch, the patch comprising a first excitation electrode, a second
excitation electrode, a first detection electrode, and a second
detection electrode. In yet another embodiment, the step of
measuring a general conductance is performed by obtaining parallel
conductance from the first detection electrode and the second
detection electrode. In an additional embodiment, the step of
generating an efficiency model further comprises the step of
comparing the general conductance to a rate of volumetric change of
the vessel.
[0044] In at least one embodiment of a method of determining an
index of vessel function according to the present disclosure, the
step of measuring a general conductance comprises a single general
conductance measurement. In another embodiment, the step of
measuring a general conductance comprises the use of a general
conductance reader operably coupled to the impedance catheter. In
yet another embodiment, the step of generating an efficiency model
further comprises the step of evaluating the maximum rate of
volumetric change of the vessel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1A shows an embodiment of an engagement catheter and an
embodiment of a delivery catheter as disclosed herein;
[0046] FIG. 1B shows a percutaneous intravascular pericardial
delivery using another embodiment of an engagement catheter and
another embodiment of a delivery catheter as disclosed herein;
[0047] FIG. 2A shows a percutaneous intravascular technique for
accessing the pericardial space through a right atrial wall or
atrial appendage using the engagement and delivery catheters shown
in FIG. 1A;
[0048] FIG. 2B shows the embodiment of an engagement catheter shown
in FIG. 2A;
[0049] FIG. 2C shows another view of the distal end of the
engagement catheter embodiment shown in FIGS. 2A and 2B;
[0050] FIG. 3A shows removal of an embodiment of a catheter as
disclosed herein;
[0051] FIG. 3B shows the resealing of a puncture according to an
embodiment as disclosed herein;
[0052] FIGS. 4A, 4B, and 4C show a closure of a hole in the atrial
wall using an embodiment as disclosed herein;
[0053] FIG. 5A shows an embodiment of an engagement catheter as
disclosed herein;
[0054] FIG. 5B shows a cross-sectional view of the proximal end of
the engagement catheter shown in FIG. 5A;
[0055] FIG. 5C shows a cross-sectional view of the distal end of
the engagement catheter shown in FIG. 5A;
[0056] FIG. 5D shows the engagement catheter shown in FIG. 5A
approaching a heart wall from inside of the heart;
[0057] FIG. 6A shows an embodiment of a delivery catheter as
disclosed herein;
[0058] FIG. 6B shows a close-up view of the needle shown in FIG.
6A;
[0059] FIG. 6C shows a cross-sectional view of the needle shown in
FIGS. 6A and 6B;
[0060] FIG. 7 shows an impedance catheter according to at least one
embodiment of the present disclosure placed on the surface of the
heart; and
[0061] FIG. 8 shows an impedance catheter with multiple sets of
detection leads according to at least one embodiment of the present
disclosure placed on the surface of the heart; and
[0062] FIG. 9 shows a data acquisition and processing system
according to at least one embodiment of the present disclosure.
DETAILED DESCRIPTION
[0063] The disclosure of the present application measures an index
of vessel and heart function to evaluate the efficiency of the
cardiovascular system and risk of disease. For the purposes of
promoting an understanding of the principles of the present
disclosure, reference will now be made to the embodiments
illustrated in the drawings, and specific language will be used to
describe the same. It will nevertheless be understood that no
limitation of the scope of the present disclosure is thereby
intended.
[0064] Vessel Contractility
[0065] Regarding vessel contractility, an assumption is made that
an artery as a thick-walled cylindrical shell consisting of
incompressible, homogeneous, isotropic, elastic material. The inner
and outer radii of the shell are denoted by r.sub.i and r.sub.e,
respectively. The outer surface is considered load-free white the
inner surface is subjected to blood pressure P(t), where t is time.
The circumferential wall stress (as) can be expressed at any
transmural radial position in the wall, r, as Lame's formula:
.sigma. .theta. = P .function. [ ( r e 2 / r i 2 ) + 1 ( r e 2 / r
i 2 ) - 1 ] [ Equation .times. .times. #1 ] ##EQU00001##
[0066] The maximum wall stress occurs at the intima, and is given
by:
.sigma. .theta. .function. ( r .times. i ) = P .function. [ ( r e 2
/ r i 2 ) + 1 ( r e 2 / r i 2 ) - 1 ] [ Equation .times. .times. #2
] ##EQU00002##
[0067] The geometric relation between vessel wall volume (V.sub.w),
vessel cavity volume (V), r.sub.i and r.sub.e can be expressed
as:
V.sub.w=.pi.(r.sub.e.sup.2-r.sub.i.sup.2)L and V=.pi.r.sub.i.sup.2L
[Equation #3]
where L is the length of the vessel. If we combine Equation #2 and
Equation #3, the following desired result is obtained:
.sigma. .theta. = P .function. [ 2 .times. V V w + 1 ] [ Equation
.times. .times. #4 ] ##EQU00003##
[0068] By normalizing wall stress to blood pressure (P), an index
of LV contractile function may result as:
.sigma. .theta. / P = 2 .times. V V w + 1 [ Equation .times.
.times. #5 ] ##EQU00004##
[0069] Analogous to dP/dt.sub.max, we propose a vessel
contractility index as the maximal rate of change of
pressure-normalized wall stress; i.e., namely:
d .times. .sigma. * / dt max = d .function. ( .sigma. .theta. / P )
dt max .times. = 2 V w .times. d .times. V d .times. t max [
Equation .times. .times. #6 ] ##EQU00005##
[0070] Since the length of the vessel remains constant, Equation #6
can be written in terms of lumen area, CSA, as:
d .times. .times. .sigma. * / d .times. t max = 2 V w .times. L
.times. d .times. C .times. S .times. A d .times. t max [ Equation
.times. .times. #7 ] ##EQU00006##
[0071] As such, the maximum rate of change of the vessel lumen
cross-sectional area is an important index of contractility, and
hence, vascular function.
[0072] Conventional clinical imaging (magnetic resonance imaging
(MRI), computed tomography (CT), ultrasound (US), etc.) can be used
in conjunction with Equation #7 to yield an index of vessel
function of a patient. This index can be determined under resting
conditions during the cardiac cycle, after a cuff occlusion to
specifically examine endothelial function, or after a
pharmacological challenge to evaluate the vasoactive tone of
vessel.
[0073] Cardiac Contractility
[0074] The formulation as described above may also be used to
evaluate heart function. The disclosure of the present application
reveals that a similar equation (Equation #6) results if a cylinder
or a spherical geometry is assumed but with a different
proportionality constant. Hence, a similar strategy of combining
current non-invasive imaging (CT, MRI, US, etc.) with Equation #6
to yield a patient specific contractility index.
[0075] Contractility Index Based on Electrical Impedance
[0076] Vessel
[0077] As referenced by prior studies, the conductance of current
flow through the organ lumen and organ wall and surrounding tissue
is parallel. For example,
G .function. ( z , t ) = C .times. SA .function. ( z , t ) .times.
.cndot. .times. C b L + G p .function. ( z , t ) [ Equation .times.
.times. #8 ] ##EQU00007##
where G.sub.p(z,t) is the effective conductance of the structure
outside the bodily fluid (organ wall and surrounding tissue),
C.sub.b is the specific electrical conductivity of the bodily
fluid, CSA is the lumen cross-sectional area of the organ and L is
the distance between the detection electrodes. This concept was
previously used to determine luminal area. However, the disclosure
of the present application identifies that the same concept can be
applied here for blood vessels with the use of Equation #7 to
determine the function of blood vessels during percutaneous
catheterization. Since only the change of CSA is required, Equation
#8 can be reduced to:
d .times. C .times. S .times. A dt max = d .times. G dt ma .times.
x [ Equation .times. .times. #9 ] ##EQU00008##
[0078] As such, the change of conductance is desired which does not
require injections as referenced by earlier studies, and can be
directly determined from the change of conductance.
[0079] Heart
[0080] Intra-Ventricle Approach
[0081] In previous studies, the catheter was placed inside of the
lumen to determine the dimensional changes. This procedure can
still be done for the heart with multiple leads (two outer
excitation electrodes (E) but multiple sets of inner detection
electrodes (D)) to add up the cross-sectional areas to provide the
volume, and hence, Equation #6. Again, only the change in
conductance is required which does not necessitate any saline
injections.
[0082] Epicardial Approach
[0083] Previous studies introduced the ability to introduce a
catheter in the pericardial space on the surface of the heart. Such
techniques include devices, systems, and methods useful for
accessing various tissues of the heart from inside the heart. For
example, various embodiments provide for percutaneous,
intravascular access into the pericardial space through an atrial
wall or the wall of an atrial appendage. In at least some
embodiments, the heart wall is aspirated and retracted from the
pericardial sac to increase the pericardial space between the heart
and the sac and thereby facilitate access into the space.
[0084] Unlike the relatively stiff pericardial sac, the atrial wall
and atrial appendage are rather soft and deformable. Hence, suction
of the atrial wall or atrial appendage can provide significantly
more clearance of the cardiac structure from the pericardium as
compared to suction of the pericardium. Furthermore, navigation
from the intravascular region (inside of the heart) provides more
certainty of position of vital cardiac structures than does
intrathoracic access (outside of the heart).
[0085] Access to the pericardial space may be used for
identification of diagnostic markers in the pericardial fluid; for
pericardiocentesis; and for administration of therapeutic factors
with angiogenic, myogenic, and antiarrhythmic potential. In
addition, epicardial pacing leads may be delivered via the
pericardial space, and an ablation catheter may be used on the
epicardial tissue from the pericardial space.
[0086] In the embodiment of the catheter system shown in FIG. 1A,
catheter system 10 includes an engagement catheter 20, a delivery
catheter 30, and a needle 40. Although each of engagement catheter
20, delivery catheter 30, and needle 40 has a proximal end and a
distal end, FIG. 1A shows only the distal end. Engagement catheter
20 has a lumen through which delivery catheter 30 has been
inserted, and delivery catheter 30 has a lumen through which needle
40 has been inserted. Delivery catheter 30 also has a number of
openings 50 that can be used to transmit fluid from the lumen of
the catheter to the heart tissue in close proximity to the distal
end of the catheter. It can be appreciated that catheter system 10,
engagement catheter 20, and delivery catheter 30 may be generally
referred to as a "catheter."
[0087] As shown in more detail in FIGS. 2A, 2B, and 2C, engagement
catheter 20 includes a vacuum channel 60 used for suction of a
targeted tissue 65 in the heart and an injection channel 70 used
for infusion of substances to targeted tissue 65, including, for
example, a biological or non-biological degradable adhesive. As is
shown in FIGS. 2B and 2C, injection channel 70 is ring-shaped,
which tends to provide relatively even dispersal of the infused
substance over the targeted tissue, but other shapes of injection
channels may be suitable. A syringe 80 is attached to injection
channel 70 for delivery of the appropriate substances to injection
channel 70, and a syringe 90 is attached to vacuum channel 60
through a vacuum port (not shown) at the proximal end of engagement
catheter 20 to provide appropriate suction through vacuum channel
60. At the distal end of engagement catheter 20, a suction port 95
is attached to vacuum channel 60 for contacting targeted tissue 65,
such that suction port 95 surrounds targeted tissue 65, which is
thereby encompassed within the circumference of suction port 95.
Although syringe 90 is shown in FIG. 2B as the vacuum source
providing suction for engagement catheter 20, other types of vacuum
sources may be used, such as a controlled vacuum system providing
specific suction pressures. Similarly, syringe 80 serves as the
external fluid source in the embodiment shown in FIG. 2B, but other
external fluid sources may be used.
[0088] A route of entry for use of various embodiments disclosed
herein is through the jugular or femoral vein to the superior or
inferior vena cavae, respectively, to the right atrial wall or
atrial appendage (percutaneously) to the pericardial sac (through
puncture).
[0089] Referring now to FIG. 1B, an engagement catheter 100 is
placed via standard approach into the jugular or femoral vein. The
catheter, which may be 4 or 5 Fr., is positioned under fluoroscopic
or echocardiographic guidance into the right atrial appendage 110.
Suction is initiated to aspirate a portion of atrial appendage 110
away from the pericardial sac 120 that surrounds the heart. As
explained herein, aspiration of the heart tissue is evidenced when
no blood can be pulled back through engagement catheter 100 and, if
suction pressure is being measured, when the suction pressure
gradually increases. A delivery catheter 130 is then inserted
through a lumen of engagement catheter 100. A small perforation can
be made in the aspirated atrial appendage 110 with a needle such as
needle 40, as shown in FIGS. 1A and 2A. A guide wire (not shown)
can then be advanced through delivery catheter 130 into the
pericardial space to secure the point of entry 125 through the
atrial appendage and guide further insertion of delivery catheter
130 or another catheter. Flouroscopy or echocardiogram can be used
to confirm the position of the catheter in the pericardial space.
Alternatively, a pressure tip needle can sense the pressure and
measure the pressure change from the atrium (about 10 mmHg) to the
pericardial space (about 2 mmHg). This is particularly helpful for
transeptal access where puncture of arterial structures (e.g., the
aorta) can be diagnosed and sealed with an adhesive, as described
in more detail below.
[0090] Although aspiration of the atrial wall or the atrial
appendage retracts the wall or appendage from the pericardial sac
to create additional pericardial space, CO2 gas can be delivered
through a catheter, such as delivery catheter 130, into the
pericardial space to create additional space between the
pericardial sac and the heart surface.
[0091] Referring now to FIG. 3A, the catheter system shown in FIG.
1B is retrieved by pull back through the route of entry. However,
the puncture of the targeted tissue in the heart (e.g., the right
atrial appendage as shown in FIG. 3A) may be sealed upon withdrawal
of the catheter, which prevents bleeding into the pericardial
space. The retrieval of the catheter may be combined with a sealing
of the tissue in one of several ways: (1) release of a tissue
adhesive or polymer 75 via injection channel 70 to seal off the
puncture hole, as shown in FIG. 3B; (2) release of an inner clip or
mechanical stitch to close off the hole from the inside of the
cavity; or (3) mechanical closure of the heart with a sandwich type
mechanical device that approaches the hole from both sides of the
wall (see FIGS. 4A, 4B, and 4C). In other words, closure may be
accomplished by using, for example, a biodegradable adhesive
material (e.g., fibrin glue or cyanomethacrylate), a magnetic
system, or an umbrella-shaped nitinol stent. An example of the
closure of a hole in the atrium is shown in FIG. 3B. Engagement
catheter 20 is attached to targeted tissue 95 using suction through
suction port 60. Tissue adhesive 75 is injected through injection
channel 70 to coat and seal the puncture wound in targeted tissue
95. Engagement catheter 20 is then withdrawn, leaving a plug of
tissue adhesive 75 attached to the atrial wall or atrial
appendage.
[0092] Another example for sealing the puncture wound in the atrial
wall or appendage is shown in FIGS. 4A, 4B, and 4C. A sandwich-type
closure, having an external cover 610 and an internal cover 620, is
inserted through the lumen of engagement catheter 600, which is
attached to the targeted tissue of an atrial wall 630. Each of
external and internal covers 610 and 620 is similar to an umbrella
in that it can be inserted through a catheter in its folded
configuration and expanded once it is outside of the catheter. As
shown in FIG. 4A, external cover 610 is deployed (in its expanded
configuration) on the outside of the atrial wall to seal a puncture
wound in the targeted tissue. Internal cover 620 is delivered
through engagement catheter 600 (in its folded configuration), as
shown in FIGS. 4A and 4B. Once internal cover 620 is in position on
the inside of atrial wall 630 at the targeted tissue, internal
cover 620 is deployed to help seal the puncture wound in the
targeted tissue (see FIG. 4C). Engagement catheter 600 then
releases its grip on the targeted tissue and is withdrawn, leaving
the sandwich-type closure to seal the puncture wound, as shown in
FIG. 4C. External cover 610 and internal cover 620 may be held in
place using adhesion or magnetic forces.
[0093] FIGS. 5A, 5B, 5C, and 5D show another embodiment of an
engagement catheter as disclosed herein. Engagement catheter 700 is
an elongated tube having a proximal end 710 and a distal end 720,
as well as two lumens 730, 740 extending between proximal end 710
and distal end 720. Lumens 730, 740 are formed by concentric inner
wall 750 and outer wall 760, as particularly shown in FIGS. 5B and
5C. At proximal end 710, engagement catheter 700 includes a vacuum
port 770, which is attached to lumen 730 so that a vacuum source
can be attached to vacuum port 770 to create suction in lumen 730,
thereby forming a suction channel. At distal end 720 of catheter
700, a suction port 780 is attached to lumen 730 so that suction
port 780 can be placed in contact with heart tissue 775 (see FIG.
5D) for aspirating the tissue, thereby forming a vacuum seal
between suction port 780 and tissue 775 when the vacuum source is
attached and engaged. The vacuum seal enables suction port 780 to
grip, stabilize, and retract tissue 775. For example, attaching a
suction port to an interior atrial wall using a vacuum source
enables the suction port to retract the atrial wall from the
pericardial sac surrounding the heart, which enlarges the
pericardial space between the atrial wall and the pericardial
sac.
[0094] As shown in FIG. 5C, two internal lumen supports 810, 820
are located within lumen 730 and are attached to inner wall 750 and
outer wall 760 to provide support to the walls. These lumen
supports divide lumen 730 into two suction channels. Although
internal lumen supports 810, 820 extend from distal end 720 of
catheter 700 along a substantial portion of the length of catheter
700, internal lumen supports 810, 820 may or may not span the
entire length of catheter 700. Indeed, as shown in FIGS. 5A, 5B,
and 5C, internal lumen supports 810, 820 do not extend to proximal
end 710 to ensure that the suction from the external vacuum source
is distributed relatively evenly around the circumference of
catheter 700. Although the embodiment shown in FIG. 5C includes two
internal lumen supports, other embodiments may have just one
internal support or even three or more such supports.
[0095] FIG. 5D shows engagement catheter 700 approaching heart
tissue 775 for attachment thereto. It is important for the
clinician performing the procedure to know when the suction port
has engaged the tissue of the atrial wall or the atrial appendage.
For example, in reference to FIG. 5D, it is clear that suction port
780 has not fully engaged tissue 775 such that a seal is formed.
However, because suction port 780 is not usually seen during the
procedure, the clinician may determine when the proper vacuum seal
between the atrial tissue and the suction port has been made by
monitoring the amount of blood that is aspirated, by monitoring the
suction pressure with a pressure sensor/regulator, or both. For
example, as engagement catheter 700 approaches the atrial wall
tissue (such as tissue 775) and is approximately in position, the
suction can be activated through lumen 730. A certain level of
suction (e.g., 10 mmHg) can be imposed and measured with a pressure
sensor/regulator. As long as catheter 700 does not engage the wall,
some blood will be aspirated into the catheter and the suction
pressure will remain the same. However, when catheter 700 engages
or attaches to the wall of the heart (depicted as tissue 775 in
FIG. 5D), minimal blood is aspirated and the suction pressure will
start to gradually increase. Each of these signs can alert the
clinician (through alarm or other means) as an indication of
engagement. The pressure regulator is then able to maintain the
suction pressure at a preset value to prevent over-suction of the
tissue.
[0096] An engagement catheter, such as engagement catheter 700, may
be configured to deliver a fluid or other substance to tissue on
the inside of a wall of the heart, including an atrial wall or a
ventricle wall. For example, lumen 740 shown in FIGS. 5A and 5C
includes an injection channel 790 at distal end 720. Injection
channel 790 dispenses to the targeted tissue a substance flowing
through lumen 740. As shown in FIG. 5D, injection channel 790 is
the distal end of lumen 740. However, in other embodiments, the
injection channel may be ring-shaped (see FIG. 2C) or have some
other suitable configuration.
[0097] Substances that can be locally administered with an
engagement catheter include preparations for gene or cell therapy,
drugs, and adhesives that are safe for use in the heart. The
proximal end of lumen 740 has a fluid port 800, which is capable of
attachment to an external fluid source for supply of the fluid to
be delivered to the targeted tissue. Indeed, after withdrawal of a
needle from the targeted tissue, as discussed herein, an adhesive
may be administered to the targeted tissue by the engagement
catheter for sealing the puncture wound left by the needle
withdrawn from the targeted tissue.
[0098] Referring now to FIGS. 6A, 6B, and 6C, there is shown a
delivery catheter 850 comprising an elongated hollow tube 880
having a proximal end 860, a distal end 870, and a lumen 885 along
the length of the catheter. Extending from distal end 870 is a
hollow needle 890 in communication with lumen 885. Needle 890 is
attached to distal end 870 in the embodiment of FIGS. 6A, 6B, and
6C, but, in other embodiments, the needle may be removably attached
to, or otherwise located at, the distal end of the catheter (see
FIG. 1A). In the embodiment shown in FIGS. 6A, 6B, and 6C, as in
certain other embodiments having an attached needle, the junction
(i.e., site of attachment) between hollow tube 880 and needle 890
forms a security notch 910 circumferentially around needle 890 to
prevent needle 890 from over-perforation. Thus, when a clinician
inserts needle 890 through an atrial wall to gain access to the
pericardial space, the clinician will not, under normal conditions,
unintentionally perforate the pericardial sac with needle 890
because the larger diameter of hollow tube 880 (as compared to that
of needle 890) at security notch 910 hinders further needle
insertion. Although security notch 910 is formed by the junction of
hollow tube 880 and needle 890 in the embodiment shown in FIGS. 6A,
6B, and 6C, other embodiments may have a security notch that is
configured differently. For example, a security notch may include a
band, ring, or similar device that is attached to the needle a
suitable distance from the tip of the needle. Like security notch
910, other security notch embodiments hinder insertion of the
needle past the notch itself by presenting a larger profile than
the profile of the needle such that the notch does not easily enter
the hole in the tissue caused by entry of the needle.
[0099] It is useful for the clinician performing the procedure to
know when the needle has punctured the atrial tissue. This can be
done in several ways. For example, the delivery catheter can be
connected to a pressure transducer to measure pressure at the tip
of the needle. Because the pressure is lower and much less
pulsatile in the pericardial space than in the atrium, the
clinician can recognize immediately when the needle passes through
the atrial tissue into the pericardial space.
[0100] Alternatively, as shown in FIG. 6B, needle 890 may be
connected to a strain gauge 915 as part of the catheter assembly.
When needle 890 contacts tissue (not shown), needle 890 will be
deformed. The deformation will be transmitted to strain gauge 915
and an electrical signal will reflect the deformation (through a
classical wheatstone bridge), thereby alerting the clinician. Such
confirmation of the puncture of the wall can prevent over-puncture
and can provide additional control of the procedure.
[0101] In some embodiments, a delivery catheter, such as catheter
850 shown in FIGS. 6A, 6B, and 6C, is used with an engagement
catheter, such as catheter 700 shown in FIGS. 5A, 5B, 5C, and 5D,
to gain access to the pericardial space between the heart wall and
the pericardial sac. For example, engagement catheter 700 may be
inserted into the vascular system and advanced such that the distal
end of the engagement catheter is within the atrium. The engagement
catheter may be attached to the targeted tissue on the interior of
a wall of the atrium using a suction port as disclosed herein. A
standard guide wire may be inserted through the lumen of the
delivery catheter as the delivery catheter is inserted through the
inner lumen of the engagement catheter, such as lumen 740 shown in
FIGS. 5B and 5C. Use of the guide wire enables more effective
navigation of the delivery catheter 850 and prevents the needle 890
from damaging the inner wall 750 of the engagement catheter 700.
When the tip of the delivery catheter with the protruding guide
wire reaches the atrium, the wire is pulled back, and the needle is
pushed forward to perforate the targeted tissue. The guide wire is
then advanced through the perforation into the pericardial space,
providing access to the pericardial space through the atrial
wall.
[0102] Referring again to FIGS. 6A, 6B, and 6C, lumen 885 of
delivery catheter 850 may be used for delivering fluid into the
pericardial space after needle 890 is inserted through the atrial
wall or the atrial appendage. After puncture of the wall or
appendage, a guide wire (not shown) may be inserted through needle
lumen 900 into the pericardial space to maintain access through the
atrial wall or appendage. Fluid may then be introduced to the
pericardial space in a number of ways. For example, after the
needle punctures the atrial wall or appendage, the needle is
generally withdrawn. If the needle is permanently attached to the
delivery catheter, as in the embodiment shown in FIGS. 6A and 6B,
then delivery catheter 850 would be withdrawn and another delivery
catheter (without an attached needle) would be introduced over the
guide wire into the pericardial space. Fluid may then be introduced
into the pericardial space through the lumen of the second delivery
catheter.
[0103] In some embodiments, however, only a single delivery
catheter is used. In such embodiments, the needle is not attached
to the delivery catheter, but instead may be a needle wire (see
FIG. 1A). In such embodiments, the needle is withdrawn through the
lumen of the delivery catheter, and the delivery catheter may be
inserted over the guide wire into the pericardial space. Fluid is
then introduced into the pericardial space through the lumen of the
delivery catheter.
[0104] The various embodiments disclosed herein may be used by
clinicians, for example: (1) to deliver genes, cells, drugs, etc.;
(2) to provide catheter access for epicardial stimulation; (3) to
evacuate fluids acutely (e.g., in cases of pericardial tampondae)
or chronically (e.g., to alleviate effusion caused by chronic renal
disease, cancer, etc.); (4) to perform transeptal puncture and
delivery of a catheter through the left atrial appendage for
electrophysiological therapy, biopsy, etc.; (5) to deliver a
magnetic glue or ring through the right atrial appendage to the
aortic root to hold a percutaneous aortic valve in place; (6) to
deliver a catheter for tissue ablation, e.g., to the pulmonary
veins, or right atrial and epicardial surface of the heart for
atrial and ventricular arrythmias; (7) to deliver and place
epicardial, right atrial, and right and left ventricle pacing
leads; (8) to occlude the left atrial appendage through
percutaneous approach; and (9) to visualize the pericardial space
with endo-camera or scope to navigate the epicardial surface of the
heart for therapeutic delivery, diagnosis, lead placement, mapping,
etc. Many other applications, not explicitly listed here, are also
possible and within the scope of the present disclosure.
[0105] If an impedance catheter is placed on the surface of the
heart as shown in FIG. 7, the parallel conductance (G.sub.p) will
change during the cardiac cycle. Since the first term in Equation
#8 will not change significantly, then:
d .times. G dt m .times. .alpha. .times. x = dG p d .times. t max [
Equation .times. .times. #10 ] ##EQU00009##
[0106] Since G.sub.p is proportional to the cross-sectional area,
Equation #10 will yield the change of cross-sectional area. If an
impedance catheter with multiple sets of detection leads is used as
shown in FIG. 8, the desired rate of change of volume evaluate at
the maximum point will be determined as an index of heart
function.
[0107] Referring now to FIG. 9, there is shown a diagrammatic view
of an embodiment of data acquisition and processing system 900 of
the present disclosure. In the embodiment shown in FIG. 9, data
acquisition and processing system 900 comprises user system 902. In
this exemplary embodiment, user system 902 comprises processor 904
and one or more storage media 906. Processor 904 operates upon data
obtained by or contained within user system 902. Storage medium 906
may contain database 908, whereby database 908 is capable of
storing and retrieving data. Storage media 906 may contain a
program (including, but not limited to, database 908), the program
operable by processor 904 to perform a series of steps regarding
conductance data as described in further detail herein. By way of
example, the program may be operable by processor 904 to analyze
conductance data, including analysis of such data in accordance
with Equations #1-10 as described herein.
[0108] Any number of storage media 906 may be used with data
acquisition and processing system 900 of the present disclosure,
including, but not limited to, one or more of random access memory,
read only memory, EPROMs, hard disk drives, floppy disk drives,
optical disk drives, cartridge media, and smart cards, for example.
As related to user system 902, storage media 906 may operate by
storing conductance data for access by a user and/or for storing
computer instructions. Processor 904 may also operate upon data
stored within database 908.
[0109] Regardless of the embodiment of data acquisition and
processing system 900 referenced herein and/or contemplated to be
within the scope of the present disclosure, each user system 902
may be of various configurations well known in the art. By way of
example, user system 902, as shown in FIG. 9, comprises keyboard
910, monitor 912, and printer 914. Processor 904 may further
operate to manage input and output from keyboard 910, monitor 912,
and printer 914. Keyboard 910 is an exemplary input device,
operating as a means for a user to input information to user system
902. Monitor 912 operates as a visual display means to display the
conductance data and related information to a user using a user
system 902. Printer 914 operates as a means to display conductance
data and related information. Other input and output devices, such
as a keypad, a computer mouse, a fingerprint reader, a pointing
device, a microphone, and one or more loudspeakers are contemplated
to be within the scope of the present disclosure. It can be
appreciated that processor 904, keyboard 910, monitor 912, printer
914 and other input and output devices referenced herein may be
components of one or more user systems 902 of the present
disclosure.
[0110] It can be appreciated that data acquisition and processing
system 900 may further comprise one or more server systems 916 in
bidirectional communication with user system 902, either by direct
communication (shown by the single line connection on FIG. 9), or
through a network 918 (shown by the double line connections on FIG.
9) by one of several configurations known in the art. Such server
systems 916 may comprise one or more of the features of a user
system 902 as described herein, including, but not limited to,
processor 904, storage media 906, database 908, keyboard 910,
monitor 912, and printer 914, as shown in the embodiment of data
acquisition and processing system 900 shown in FIG. 9. Such server
systems 916 may allow bidirectional communication with one or more
user systems 902 to allow user system 902 to access conductance
data and related information from the server systems 916. It can be
appreciated that a user system 902 and/or a server system 916
referenced herein may be generally referred to as a "computer."
[0111] The catheter can be inserted into the pericardial space, as
outlined in previous studies, or directly placed on as during open
heart surgery. The patch containing the excitation electrodes (E)
and detection electrodes (D) can be made to adhere to the surface
through glue that is introduced through the lumen of the catheter
into pores of the patch if the percutaneous approach is used.
Alternatively, the patch may be glued on by hand with the open
surgery approach. The electrodes are then interfaced with an
impedance module to measure voltage differences as noted in prior
studies.
[0112] The foregoing disclosure of the exemplary embodiments of the
present application has been presented for purposes of illustration
and description and can be further modified within the scope and
spirit of this disclosure. It is not intended to be exhaustive or
to limit the present disclosure to the precise forms disclosed.
This application is therefore intended to cover any variations,
uses, or adaptations of a device, system and method of the present
application using its general principles. Further, this application
is intended to cover such departures from the present disclosure as
may come within known or customary practice in the art to which
this system of the present application pertains. Many variations
and modifications of the embodiments described herein will be
apparent to one of ordinary skill in the art in light of the above
disclosure. The scope of the present disclosure is to be defined
only by the claims appended hereto, and by their equivalents.
[0113] Further, in describing representative embodiments of the
present disclosure, the specification may have presented the method
and/or process of the present disclosure as a particular sequence
of steps. However, to the extent that the method or process does
not rely on the particular order of steps set forth herein, the
method or process should not be `limited` to the particular
sequence of steps described. As one of ordinary skill in the art
would appreciate, other sequences of steps may be possible.
Therefore, the particular order of the steps set forth in the
specification should not be construed as limitations on the claims.
In addition, the claims directed to the method and/or process of
the present disclosure should not be limited to the performance of
their steps in the order written, and one skilled in the art can
readily appreciate that the sequences may be varied and still
remain within the spirit and scope of the present disclosure.
* * * * *