U.S. patent application number 10/949422 was filed with the patent office on 2005-05-26 for left atrial access apparatus and methods.
Invention is credited to Saadat, Vahid.
Application Number | 20050113719 10/949422 |
Document ID | / |
Family ID | 34393159 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050113719 |
Kind Code |
A1 |
Saadat, Vahid |
May 26, 2005 |
Left atrial access apparatus and methods
Abstract
Left atrial access apparatus and methods are described herein.
Different parameters, such as oxygen saturation difference, between
the left and right atrial chambers is utilized to guide a needle or
catheter into a desired position within the heart. Various sensing
elements can be utilized to detect the physiological parameter
difference, such as oxygen levels, in the left atrium. The sensor
can be carried by the needle, at its tip or along its body, and can
measure the physiological parameter levels contained in the blood,
fluid, or tissue.
Inventors: |
Saadat, Vahid; (Saratoga,
CA) |
Correspondence
Address: |
MORRISON & FOERSTER LLP
755 PAGE MILL RD
PALO ALTO
CA
94304-1018
US
|
Family ID: |
34393159 |
Appl. No.: |
10/949422 |
Filed: |
September 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60506465 |
Sep 26, 2003 |
|
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Current U.S.
Class: |
600/585 ;
600/309; 600/339; 600/342; 600/486; 600/549 |
Current CPC
Class: |
A61B 5/14542 20130101;
A61B 5/6848 20130101; A61B 5/1459 20130101 |
Class at
Publication: |
600/585 ;
600/339; 600/342; 600/309; 600/549; 600/486 |
International
Class: |
A61M 025/09; A61B
005/00 |
Claims
I claim:
1. An apparatus for detecting a physiological parameter,
comprising: a probe configured to pierce a tissue region of
interest; a sensor disposed near or at the distal end of the probe,
the sensor being adapted to detect the physiological parameter; and
a guidewire connected to the probe and adapted to advance the
sensor towards the tissue region of interest.
2. The apparatus of claim 1 further comprising a handle removably
positioned on a proximal end of the guidewire for manipulating the
guidewire.
3. The apparatus of claim 1 further comprising a detector in
electrical communication with the sensor for detecting the
physiological parameter.
4. The apparatus of claim 3 further comprising a user interface in
electrical communication with the detector for indicating the
physiological parameter to a user.
5. The apparatus of claim 1 further comprising a catheter
advanceable over the guidewire towards the tissue region of
interest.
6. The apparatus of claim 5 wherein the catheter comprises an end
effector.
7. The apparatus of claim 1 wherein the probe comprises a needle
body.
8. The apparatus of claim 7 wherein the needle body is at least
partially hollow.
9. The apparatus of claim 7 wherein the needle body comprises a
tapered distal end for piercing into or through the tissue region
of interest.
10. The apparatus of claim 7 wherein the needle body comprises a
20-27 gauge needle.
11. The apparatus of claim 1 wherein the sensor is adapted to
detect the physiological parameter selected from the group
consisting of oxygen saturation, temperature, carbon dioxide
concentration, blood pressure, blood velocity, pH, and combinations
thereof.
12. The apparatus of claim 1 wherein the sensor comprises at least
one optical fiber adapted to detect light reflections indicative of
the physiological parameter from fluids or tissue within or
adjacent to the tissue region of interest.
13. The apparatus of claim 1 wherein the sensor comprises at least
one optical fiber adapted to detect a pressure change via a
flexible membrane indicative of the physiological parameter from
fluids or tissue within or adjacent to the tissue region of
interest.
14. The apparatus of claim 1 wherein the sensor comprises at least
one optical fiber adapted to detect fluorescence from a polymeric
material indicative of the physiological parameter from fluids or
tissue within or adjacent to the tissue region of interest.
15. A method of locating a tissue region of interest for passage of
an apparatus therethrough, comprising: probing an area of tissue
with a probe; sensing a physiological parameter of the tissue while
probing the area; and piercing the tissue at least partially with
the probe upon detecting a change in the sensed physiological
parameter.
16. The method of claim 15 further comprising advancing the probe
to the tissue region of interest within a mammalian heart prior to
probing an area.
17. The method of claim 15 further comprising advancing the probe
into a right atrial chamber of a heart prior to probing an
area.
18. The method of claim 15 further comprising advancing a catheter
over a guidewire towards the tissue region of interest, the
guidewire being attached to a proximal end of the probe.
19. The method of claim 15 wherein probing an area of tissue
comprises advancing the probe against, into, or through the area of
tissue.
20. The method of claim 15 wherein probing an area of tissue
comprises probing the tissue in a predetermined pattern.
21. The method of claim 15 wherein probing an area of tissue
comprises probing an atrial septum.
22. The method of claim 15 wherein sensing a physiological
parameter comprises sensing the parameter selected from the group
consisting of oxygen saturation, temperature, carbon dioxide
concentration, blood pressure, blood velocity, pH, and combinations
thereof.
23. The method of claim 15 wherein sensing a physiological
parameter comprises transmitting a light and measuring its
reflectance as being indicative of the physiological parameter.
24. The method of claim 15 wherein sensing a physiological
parameter comprises comparing a measurement from the probed area to
a measurement from an area proximal of the probed area.
25. The method of claim 15 wherein sensing a physiological
parameter comprises comparing a measurement from a left atrial
chamber to a measurement from a right atrial chamber.
26. The method of claim 15 wherein piercing the tissue comprises
advancing the probe at least partially into a left atrial chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Provisional Pat. App. Ser. No. 60/506,465 filed Sep. 26, 2003,
which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to medical devices
used for detecting parameters within the body. More particularly,
the present invention relates to apparatus and methods for
facilitating or enabling access across the atrial septum, e.g., for
septostomy procedures within the heart.
BACKGROUND OF THE INVENTION
[0003] The mammalian heart is divided into four chambers. The
superior or upper two chambers include the left and right atria.
The right atrium is fluidly in communication with the venous system
and carries deoxygenated blood. The left atrium receives oxygenated
blood from the lungs and facilitates the movement of this blood
into the left ventricle for pumping throughout the body.
[0004] The inferior vena cava (IVC) and the superior vena cava
(SVC) generally lie, more or less, on a straight line from the
diaphragm to the jugular vein. The right atrium forms a chamber
that connects the two. Also draining into the right atrium is the
coronary sinus. The right atrium lies anteriorly (in front of) and
to the right side of the left atrium. The intra-atrial septum is a
small area where the two atria are opposed to each other. The
diameter of this structure is approximately 30-35 mm in the adult
human. The intra-atrial septum is embryologically formed by the
fusion of the septum secundum and the septum primum. In
approximately 20% of adults, the septum is not fused and a
potential passed therebetween exists known as a patent foramen
ovale (PFO). Surrounding the intra-atrial septum, outside of the
atrial walls, is the pericardial space. Anterior to the right
atrium lies the aorta. Posterior to the left atrium lies the
pulmonary veins.
[0005] For many procedures, e.g., mitral valvuloplasty, left atrial
appendage closure, and left-sided arrhythmia ablation, it is
desirable to enter or access the left atrium to effect the desired
procedure while minimizing trauma to the patient. To
non-operatively effect such access, one conventional approach
involves puncturing the intra-atrial septum from the right atrial
chamber to the left atrial chamber. For emerging procedures such as
percutaneous valve repair and replacement, transeptal access to the
left atrial chamber of the heart may allow for larger devices to be
introduced into the venous system than can generally be introduced
percutaneously into the arterial system.
[0006] The process of traversing from the right atrium and into the
left atrium is called septostomy as the atrial septum is typically
penetrated. Septostomy involves direct targeting of a small area of
the atrial septum. If the targeted area is missed by the
penetrating device, structures such as the aorta or the free wall
of the atrium may be in danger of being penetrated. If such a
penetration were to occur, serious injury or death to the patient
could result. In fact, the most common serious complication of
transeptal puncture is cardiac tamponade, a life-threatening
condition resulting from misplacement of the transeptal puncture
leading to bleeding into the pericardial space.
[0007] Interventional cardiologists typically gain access to the
left atrium by performing a transeptal puncture using a special
needle. The needle, which is hollow, is typically guided by
utilizing fluoroscopy. However, fluoroscopy provides only
two-dimensional imaging and does not preclude the possibility of
the clinician inadvertently puncturing the septum in the wrong
location. Some reports have shown that trans-esophageal
echocardiography and intracardiac echocardiography can improve the
safety of transeptal puncture; however these additional procedures
are expensive, inconvenient, and add further risk to the
procedure.
[0008] Perfecting the technique of transeptal puncture is very
challenging for the clinician. Very few interventional
cardiologists and electrophysiologists are currently skilled at
this procedure. As difficult as it is to perform, it is more
difficult to teach and relies upon both visual and tactile senses.
Obtaining safe access to the left atrium remains a major obstacle
to the growth of the technologies relating to the left atrium,
e.g., left-sided arrhythmia mapping and ablation, atrial appendage
closure in atrial fibrillation, percutaneous repair and replacement
of heart valves, etc.
BRIEF SUMMARY OF THE INVENTION
[0009] To gain access to the left atrium within the heart, a
transeptal puncture may be performed by a clinician utilizing a
sounding procedure. Such a procedure may take advantage of
physiological parameter differences between the left and right
atrial chambers to detect a direct pathway therebetween. For
example, one method may be to utilize the oxygen saturation
difference between the atrial chambers in guiding a needle or
catheter into the appropriate position.
[0010] Generally, an apparatus for detecting a physiological
parameter may comprise a probe configured to pierce a tissue region
of interest, a sensor disposed near or at the distal end of the
probe, the sensor being adapted to detect the physiological
parameter, and a guidewire connected to the probe and adapted to
advance the sensor towards the tissue region of interest.
[0011] A method of locating the tissue region of interest for
passage of an apparatus therethrough may also be utilized with any
variation of the apparatus where the method generally comprises
probing an area of tissue with a probe, sensing a physiological
parameter of the tissue while probing the area, and piercing the
tissue at least partially with the probe upon detecting a change in
the sensed physiological parameter.
[0012] The left and right atria carry blood that varies in several
parameters. For instance, the left atrium's blood oxygen saturation
may reach 99% whereas the right atrium may have an oxygen
saturation of only 80% or lower. Moreover, the pressure in the left
atrium, except in certain disease states, is typically higher than
the pressure in the right atrium. The resulting pressure wave forms
have different amplitudes and differ in the atria and other
neighboring cardiac structure.
[0013] One way to use the oxygen saturation difference between the
two chambers in order to guide a needle or catheter into the right
position is by using a sensing element to detect the oxygen levels
in the left atrium. The sensor may be carried by the needle at its
tip or along its body and can be used to measure the level of,
e.g., oxygen, carbon dioxide, etc., contained in the blood.
[0014] Other variations of the sensor assembly may utilize light
reflectance and absorbance differences, as well as various
polymeric materials for sensing concentrations of various gases
within the blood.
[0015] In locating the desired pathway from the right atrium to the
left atrium, a needle may be guided to an initial location on the
tissue between the atrial chambers. The needle may be penetrated
into the tissue to take a measurement of the desired physiological
parameter. If an unsuccessful measurement is detected, the needle
may be moved to a second location where another measurement may be
taken. This process may be repeated any number of times over the
tissue region of interest while following a predetermined pattern
until a physiological parameter change is detected which is
indicative of entry into the left atrium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1A shows an illustrative diagram of the heart and the
atrial septum separating the left atrium and the right atrium with
one variation of the sensing apparatus probing the septum.
[0017] FIG. 1B shows a detailed view of the probed area of the
atrial septum and one example of a pattern that may be implemented
by the sensing apparatus for detecting the septum for accessing the
left atrium.
[0018] FIGS. 2A to 2C respectively illustrate one example of how a
sensing apparatus may be utilized to probe the atrial septum, and
once a favorable location is detected, how the sensing apparatus
may be advanced through the septum so that another therapeutic
device, such as a catheter, may be advanced over the sensing
apparatus and into the newly created opening for effecting
treatment within the left atrium.
[0019] FIGS. 3A and 3B show top and side views, respectively, of
one variation of the sensing apparatus in a hollow needle
incorporating an integrated sensor at its tip.
[0020] FIG. 4 shows a detailed side view of another variation of
the sensing apparatus utilizing reflective fiberoptic transducers
for detecting physiologic parameters in probing the atrial
septum.
[0021] FIG. 5 shows a top view of another variation utilizing
reflection of light in the form of scattered back-reflection from
surrounding blood or fluids.
[0022] FIG. 6 shows a partial cross-sectional side view of yet
another variation utilizing a movable reflective membrane or
diaphragm to detect pressure changes.
[0023] FIG. 7 shows a partial cross-sectional side view of yet
another variation utilizing a polymeric material sensitive to
oxygen or carbon dioxide concentrations.
[0024] FIG. 8 shows a side view of another variation of the device
optionally utilizing a piezo-crystal transducer for detecting the
surrounding environment.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The left and right atria carry blood that varies in several
physiological parameters. For example, the left atrium's blood
oxygen saturation may reach 99% whereas the right atrium may only
reach an oxygen saturation of 80% or lower. Another parameter
includes pressure differences. The pressure in the left atrium is
normally higher than the pressure in the right atrium, except in
certain disease states. Also, the pressure wave forms have
different amplitudes. Moreover, the wave forms also differ between
the atria and other neighboring cardiac structures, such as the
aorta (which has high velocity blood flow), and the intra-atrial
septum or pericardium (which have no blood flow).
[0026] To gain access to the left atrium when performing a
transeptal puncture, a clinician can perform a sounding procedure
by utilizing any of the physiological parameter differences to
detect a direct pathway. One method may be to utilize the oxygen
saturation difference between the atrial chambers in guiding a
needle or catheter into the appropriate position. As shown in the
illustrative diagram of mammalian heart H in FIG. 1A, sensor
assembly 10 generally comprising a hollow or solid needle 12 and
sensing element 14 disposed near or at the distal end of assembly
10 may be passed initially into the right atrium RA, for example,
via the inferior vena cava or the superior vena cava. Needle 12 and
sensor 14 may be disposed on the distal end of guidewire 16 which
provides sufficient flexibility and strength for manipulating the
assembly 10 via the proximal end of guidewire 16 located externally
of the patient's body. Assembly 10 may be integrated with the
guidewire 16 to form a unitary structure. Alternatively, assembly
10 may be fabricated and connected separately to guidewire 16. The
guidewire 16 may be a conventional guidewire having a variety of
diameters, e.g., 0.35 mm (0.014 in.) or 0.5 mm (0.021 in.) or 0.9
mm (0.035 in.), etc. Right ventricle RV and left ventricle LV are
also shown for orientation.
[0027] Sensor 14 may be used to detect the physiological parameter,
in this example oxygen levels, in the right atrium RA. Needle 12
and sensor 14 may then be pressed against or passed into or through
the septum SP to take an additional measurement of the tissue or
fluid environment beyond septum SP. A number of measurements 20 may
be performed over an area of tissue 18 over septum SP likely to
lead directly to the left atrium LA. In this example, sensor 14 may
be carried by needle 12 at the tip or along the needle body, as
described below in further detail. Sensor 14 may be used to measure
the level of oxygen or carbon dioxide contained in the tissue or
blood within which sensor 14 is positioned. As needle 12 penetrates
the septum SP and enters into the left atrium LA, the sensed oxygen
saturation will change from venous blood to tissue and then to
arterial blood having a relatively higher degree of oxygen
saturation. This rise in the sensed oxygen level is an indication
that a path to the left atrium LA has been located.
[0028] The needle 12 used may be relatively small in thickness,
e.g., about 20-27 gauge, so that the clinician can repeatedly probe
the tissue area of interest 18 that is thought to be the true
septum SP separating the right atrium RA and the left atrium LA
without fear of causing permanent damage to the tissue. A beveled
needle 12 will normally leave a slit-like track through the tissue
that automatically seals after the needle 12 is retracted from the
tissue. In probing the tissue region of interest 18, needle 12 may
be guided to an initial location, point 1, where needle 12 may be
inserted into the tissue to penetrate the septum SP to take a
measurement 20 of the physiological parameter. If an unsuccessful
measurement is detected, needle 12 may be moved to a second
location, point 2, where another measurement may be taken. This
process may be repeated any number of times over the tissue region
of interest 18 while following a predetermined pattern, e.g.,
taking measurements from point 1 to point n, as shown in the detail
view of FIG. 1B, until a physiological parameter change is detected
which is indicative of entry into the left atrium LA.
[0029] FIG. 2A shows an illustrative assembly side view of needle
12 and sensor 14 disposed on the distal end of guidewire 16. In
this variation, the proximal end of guidewire 16 may have handle 22
optionally mounted thereto to facilitate handling and manipulation
of guidewire 16 and needle 12 within the body. Sensor 14 located
near or at the distal end of needle 12, may be electrically
connected, e.g., via conductive wire(s) 28, through guidewire 16 to
a detector unit 24 which can be used to receive and process the
sensed parameters from sensor 14. Detector 24 may be further in
electrical communication with user interface or display 26 which
may be used to present or indicate the sensed measurements to the
clinician.
[0030] As mentioned above, sensor 14 positioned on needle 12 can
detect one of a number of parameters, e.g., oxygen saturation,
temperature, carbon dioxide concentration, blood pressure, blood
velocity, pH, etc. If the sensed parameter is of sufficient nature
indicating the left atrium LA has been penetrated through a newly
created opening 30, as shown in FIG. 2B, then the handle 22 (if
used) located on the proximal portion of guidewire 16 may be
removed. Once handle 22 has been removed, any number of catheter
devices 32, such as a dilator or a therapeutic catheter or any
number of catheters having a desired end effector 34, may be
advanced over guidewire 16 and into the left atrium LA through the
opening 30 created by needle 12, as shown in FIG. 2C.
[0031] In an alternative variation, robotically-controlled
catheters may be used to perform a raster scan to detect the proper
pathway to the left atrium LA. A robotically guided needle system
may offer an advantage of avoiding a previously tested area by
tracking the needle's current and previously probed areas within
the target region 18.
[0032] In an alternative variation, a tapered and curved dilator
and sheath about 68 cm, for instance, similar to a "Mullens" sheath
having a 0.8 mm lumen (0.032 in), may be placed into the superior
vena cava over a guidewire using fluoroscopic guidance. The
guidewire may be removed from the patient and a sensing needle 12
(which can be placed within a second hollow puncturing needle) may
then be advanced to a position just inside the tip of the dilator.
This needle 12 can be connected electrically to a detector 24
outside the patient and a physiological parameter of the
environment around the needle tip 12 can be measured. This
parameter measurement can be continuous or intermittent depending
upon the desired results. While this parameter is being measured,
the needle 12 may be withdrawn under fluoroscopic guidance and
positioned in the vicinity of the intra-atrial septum SP. The
needle 12 may then be advanced to penetrate into the septum SP with
the goal of finding the left atrium LA.
[0033] The milieu or parameter sensor 14 can be made in various
ways for measuring the local milieu of the environment it is placed
within. Described below are examples of variations of sensors 14
which may be utilized. However, these examples are intended to be
illustrative and are not intended to limit the scope of the types
of sensors and needles described herein. Furthermore, it is also
intended that any combination of these sensors can also be used to
acquire multiple parameters from the local area.
[0034] FIGS. 3A and 3B show illustrative top and side views,
respectively, of one variation of sensor assembly 10. As shown,
needle 12, which may be hollow or solid, may incorporate an
integrated sensor 14 near or at its tip 38. Sensor 14 is shown in
this example as being positioned within needle opening or port 36.
Sensor 14 may also be utilized as a transducer and convert the
sensed physiological parameter acquired from the environment into
an electric signal. The sensed parameters and/or electrical signals
may be transmitted via electrical connection 28 to detector 24,
which may be located externally of the patient. As described above,
sensor 14 may be configured to be a temperature sensor, a
light-emitting device in addition to a photodiode for detecting the
same, an ultrasound sensor, a pH sensor, an antenna, etc., or any
combination thereof.
[0035] Sensor 14, for instance, may be an ultrasound crystal which
changes its resonance as a function of the tissue or fluid the
crystal is placed within. Blood and cardiac tissue will generate a
different response each. By measuring the resonance of the sensor
or transducer 14, a clinician can assess whether the needle 12 and
sensor 14 is located within the tissue wall or within the flowing
blood environment.
[0036] FIG. 4 shows an illustrative side view of another sensor
variation 40. This particular sensor assembly 40 shows a reflective
type measurement device in which one or more light signals are
passed to the tip of the needle 42 via a transmitter optical fiber
46. The light signal may be generated by a light source 58 located
outside the body and passed through one or more lenses 54 prior to
entering transmitter fiber 46. This light signal may pass through a
medium, e.g., tissue, fluid, blood, etc., contained between the end
of the optical fiber 46 and the reflector 50 within an opening or
window defined along needle 42.
[0037] In case the tip of the needle 42 is inserted into a
blood-containing environment, the light 52 passes through the
blood. Once the light hits the reflector 50, it is reflected back
on to the receiving optical fiber 48 and transmitted proximally
back to detector circuitry 62 located outside the body. One or more
lenses 56 may be utilized to filter the reflected light signals, if
desired, prior to receiving the reflected light on detector 60. The
detector circuitry 62 will then detect the amplitude of the
reflected light. By varying the wavelength of the transmitted light
and measuring the amplitude of the reflected light, a spectroscopic
measurement can be performed and, e.g., the oxygen saturation,
carbon dioxide concentration, etc. can be measured and ultimately
displayed via display 64 to the clinician.
[0038] FIG. 5 shows a variation of the sensor assembly 70 which is
similar to the assembly 40 shown above in FIG. 4. Sensor assembly
70 may utilize the same technique of measuring the light reflection
but without the use of a reflector in this instance. Transmitting
optical fiber 76 and receiving optical fiber 78 may simply be
disposed within an opening 74 defined in needle 72 and the
surrounding blood or tissue itself may be utilized to reflect the
transmitted light 80 back to receiving optical fiber 78 in the form
of scattered back-reflection 82. The backscatter can be measured
for amplitude and wavelength to assess, e.g., the oxygen saturation
or carbon dioxide concentration.
[0039] FIG. 6 shows yet another variation on sensor assembly 90 in
a partial cross-sectional side view. In this variation, a pressure
transducer may be utilized for detecting absolute or gauge pressure
within the atrium as a physiological parameter. Reflective membrane
104 may be disposed within needle body 92 proximally of needle
opening 102, which is open to the surrounding environment. As
needle 92 is positioned within the atrial chambers, reflective
membrane 104 may become displaced 104' in relation to the
surrounding pressure. Optical fiber 100 may be positioned
proximally of reflective membrane 104 such that the terminal end of
fiber 100 is positioned within sensing assembly 94 within needle
body 92. A compressed gas, which may have a pressure of about 1 atm
(760 mmHg), may fill sensing chamber 98 located between barrier 96
and reflective membrane 104.
[0040] Upon being placed in an environment with a higher pressure
than the compressed gas within chamber 98, reflective membrane 104'
may be displaced accordingly. Optical fiber 100 may emit, as well
as receive a reflected light which will re-enter the optical fiber
100. Depending upon the amount of displacement reflective membrane
104' undergoes, a lower amplitude of reflected light will be
detected which in turn can be correlated with the outside or
detected pressure. A high detected pressure, for example, greater
than 50 mmHg, will indicate aortic perforation, while a pressure in
the range of, e.g., 15-30 mmHg, is more indicative of the pressure
within the left atrium LA.
[0041] FIG. 7 shows yet another variation of sensing assembly 110.
In this variation, a polymeric material 112 which is sensitive to
oxygen or carbon dioxide concentration, may be positioned within
opening 102 within needle 92. As polymer 112 comes into contact
with the surrounding blood, polymer 112 may fluoresce according to
the gas concentration detected within the blood. Optical fiber 100
positioned proximally or adjacent to polymeric material 112 may be
used to measure the fluorescence quenching times which can be
utilized in turn to assess the degree of oxygen saturation or
carbon dioxide presence. Polymeric materials suitable for such
applications are typically found and commercialized by Luxtron
Corporation (Santa Clara, Calif.).
[0042] An additional parameter such as the resonance of the needle
tip can be utilized to ensure that the sensor assembly is not
positioned within solid tissue having high oxygen saturation. Such
tissue can be found in the walls of the aorta, atrium, and other
cardiac structures. For instance, blood velocity may also be
measured by an ultrasound crystal in conjunction with another
physiological parameter. FIG. 8 shows a side view of a piezo-type
crystal transducer 124 positioned within an opening 122 defined
within needle 120 and driven by driver 126, which may be located
outside the patient body. Such a transducer 124 may be found, e.g.,
in Doppler systems manufactured by Cardiometrics Inc. (Mountain
View, Calif.).
[0043] The transducer 124 can emit a pulse of sound energy at
ultrasonic frequencies. The reflected sound waves from the
immediate environment can indicate whether the area is static (such
as in the middle of flesh) or moving (such as in a pool of blood in
the left atrium LA). The velocity of blood can indicate a low
velocity environment such as the left atrial LA area or a high
velocity area such as the aorta, therefore warning against
subsequent penetration with a larger catheter. Once it is
positively established that the tip of needle 120 is in the left
atrium LA, further procedures as described above may be
accomplished.
[0044] The applications of the disclosed invention discussed above
are not limited to certain treatments or regions of the body, but
may include any number of other treatments and areas of the body.
Modification of the above-described methods for carrying out the
invention, and variations of aspects of the invention that are
obvious to those of skill in the arts are intended to be within the
scope of this disclosure. Moreover, various combinations of aspects
between examples is also contemplated and is considered to be
within the scope of this disclosure as well.
* * * * *