U.S. patent number 3,893,461 [Application Number 05/309,996] was granted by the patent office on 1975-07-08 for pacing apparatus and method utilizing improved catheter.
Invention is credited to Thomas A. Preston.
United States Patent |
3,893,461 |
Preston |
July 8, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Pacing apparatus and method utilizing improved catheter
Abstract
Improved apparatus and method for temporary pacing, comprising a
catheter having a first electrode positioned for placement in the
patient's heart and a second electrode positioned to be within the
patient's body but sufficiently proximal that it is outside the
patient's heart, the second electrode having a surface area about
an order of magnitude greater than the first, the electrodes being
connected through respective leads within the catheter to a
pacemaker (registered trademark, U.S. Patent Office), with the
first electrode connected as the cathode.
Inventors: |
Preston; Thomas A. (Seattle,
WA) |
Family
ID: |
23200551 |
Appl.
No.: |
05/309,996 |
Filed: |
November 28, 1972 |
Current U.S.
Class: |
607/17;
607/10 |
Current CPC
Class: |
A61N
1/056 (20130101) |
Current International
Class: |
A61N
1/05 (20060101); A61n 001/36 () |
Field of
Search: |
;128/404,418,419P,421,422 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Rogel et al., "Journal of Thoracic & Cardiovascular Surgery,"
Vol. 61, No. 3, March, 1971, pp. 466-471. .
USCI Catalog, No. 5070021, 9/72. .
Schwedel et al., "Annals-New York Academy of Sciences," Vol. III,
Art. 3, pp. 972-980, June 11, 1964..
|
Primary Examiner: Kamm; William E.
Attorney, Agent or Firm: Bowie, Benasutti and Preston
Claims
I claim:
1. Catheter apparatus adapted to be positioned in a patient for use
in cardiac pacing of the patient, with a predetermined end
extending into the patient's heart, comprising:
a. an elongated flexible catheter tube having two conducting leads
extending through respective lengths thereof;
b. a distal electrode of predetermined surface size positioned near
said predetermined end of said catheter tube, and connected
electrically to a first of said leads; and
c. proximal electrode positioned on said catheter at a distance at
least about 23 cm from said distal electrode, and connected
electrically to the second of said leads.
2. The apparatus as described in claim 1, wherein said proximal
electrode has a surface area at least 10 times as great as said
distal electrode.
3. The apparatus as described in claim 2, wherein said proximal
electrode is positioned a distance within a range of 23-29 cm
proximal from said distal electrode.
4. The apparatus as described in claim 1, wherein said proximal
electrode extends less than 6 centimeters along said catheter
tube.
5. The apparatus as described in claim 1, wherein said proximal
electrode is of greater surface area than said distal
electrode.
6. Pacing apparatus adapted for generating electrical pacing
signals outside of a patient, communicating said signals inside of
the patient, said delivering said signals between a position within
the heart of the patient and a position external to said heart,
comprising:
a. a catheter adapted for insertion into a patient, having a distal
electrode positioned near a first end thereof, a proximal electrode
on said catheter and positioned a distance at least 23 cm from said
distal electrode, a first lead connecting said distal electrode
with the opposite end of said catheter, and a second lead
connecting the proximal electrode with said opposite catheter
end;
b. signal generating means, for generating electrical pacing
signals, said signal generating means having first and second
terminals across which said electrical signals appear;
c. connecting means for connecting, at said opposite end of said
catheter, said first lead to the first terminal of said signal
generating means and said second lead to the second terminal of
said signal generating means.
7. The apparatus as described in claim 6, wherein said proximal
electrode is positioned at a distance within a range of about 23-29
cm from said distal electrode.
8. The apparatus as described in claim 6, wherein said signal
generating means is further characterized in that said signals are
negative at said first terminal with respect to said second
terminal, such that said distal electrode is the cathode and said
proximal electrode is the anode, whereby cathodal pacing of the
heart is achieved when said catheter is positioned such that said
distal electrode is within the patient's heart and said proximal
electrode is within the patient and outside of the patient's
heart.
9. The apparatus as described in claim 6, wherein said signal
generating means is a demand type pacing generator.
10. A method of artificially pacing a human patient comprising
periodically generating outside of said patient electrical pacing
signals, positioning a first electrode at a first position within
said patient's heart and a second electrode at a second position
within said patient's vascular system but outside of said patient's
heart, transmitting said signals into said patient and connecting
them to said electrodes with said signals being negative at said
first position with respect to said second position.
11. The method as described in claim 10 wherein said first
electrode has a first surface of a predetermined area, and said
second electrode has a surface area greater than said first
surface, and comprising distributing the electric field generated
at said second electrode along said second electrode.
12. The method as described in claim 10, comprising periodically
generating pacing signals with a demand pacer, and also sensing
biopotentials at said first and second positions and developing
therefrom biopotential signals, coupling said biopotential signals
to said demand pacer, and generating with said demand pacer said
electrical pacing signals as a function of said sensed biopotential
signals.
13. The method as described in claim 7 wherein said first position
is in the right ventricle of the patient's heart.
14. The method as described in claim 10 wherein said positioning
step comprises positioning a bipolar catheter having said first and
second electrodes thereon in said patient such that said first
electrode is within said patient's heart and said second electrode
is at least 4 cm outside of said patient's heart, said method
further including coupling said electrical pacing signals to said
electrodes, whereby said patient is cathodally paced.
15. The method as described in claim 10, wherein said positioning
step comprises positioning a catheter having first and second
electrodes thereon in said patient such that said first electrode
is positioned within the patient's right ventricle.
16. A method of artificially pacing a human patient through a
catheter, said catheter having first and second electrodes, with
said first electrode being near one end of said catheter,
comprising:
a. positioning within said patient a portion of said catheter, said
positioning step including positioning said first electrode within
said patient's heart and said second electrode within said patient
and outside of said patient's heart;
b. maintaining the opposite end of said catheter outside of said
patient;
c. periodically generating outside of said patient bipolar pacing
signals;
d. connecting said pacing signals to said catheter and transmitting
said signals through said catheter to said electrodes so that said
signals appear across said electrodes, whereby said patient is
paced.
17. The method as described in claim 16, wherein said pacing
signals are connected so that said pacing signals have a negative
polarity at said first electrode with respect to said second
electrode, whereby said patient is cathodally paced.
18. The method as described in claim 17, wherein said positioning
step comprises positioning said second electrode at least 4 cm
outside of the patient's heart.
19. The method as described in claim 17, wherein said positioning
step comprises positioning said second electrode within about 10 cm
from the patient's heart.
20. A method of artificially pacing a human patient comprising
positioning a bipolar catheter having first and second electrodes
in said patient such that said first electrode is positioned within
said patient's heart and said second electrode is positioned at
least 4 cm outside of said patient's heart, periodically generating
outside of said patient electrical pacing signals, connecting said
electrical pacing signals between said first electrode and said
second electrode with said signals being negative at said electrode
within said patient's heart with respect to said second electrode
outside of said patient's heart, whereby said patient is cathodally
paced.
21. The method as described in claim 20, comprising positioning
said first electrode in the right ventricle of said patient's
heart.
22. Catheter apparatus adapted to be positioned in a patient for
use in cardiac pacing of the patient, with a predetermined end
extending into the patient's heart, comprising:
a. an elongated flexible catheter tube having two conducting leads
extending through respective lengths thereof;
b. a distal electrode of predetermined surface size positioned near
said predetermined end of said catheter tube, and connected
electrically to a first of said leads; and
c. a proximal electrode positioned on said catheter, said proximal
electrode being at its distal end a distance of at least about 23
cm from said distal electrode, and connected electrically to the
second of said leads.
23. The apparatus as described in claim 22, further comprising:
a. signal generating means, for generating electrical pacing
signals, said signal generating means having first and second
terminals across which said electrical signals appear;
b. connecting means for connecting, at the end of said catheter
opposite said predetermined end, said first lead to said first
terminal and said second lead to said second terminal; and
c. said signal generating means producing signals which are
negative at said second terminal with respect to said first
terminal, so as to provide apparatus for cathodal pacing.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention lies in the area of heart pacing apparatus and, more
particularly, in the area of catheters used with external and
implanted Pacemaker for temporary and permanent pacing in a
clinical environment. The apparatus and method of this invention
are particularly adapted for "demand" pacing.
2. Description of the Prior Art
Temporary pacing of a patient in the post-operative period
following cardiac surgery is an established and effective means of
treating arrhythmias or increasing cardiac output. Additionally,
temporary pacing is particularly important and widely used with
respect to complete heart block, especially in patients undergoing
acute myocardial infarction. Such temporary pacing has been a
widely used clinical procedure in this country for many years, and
the technique of inserting the catheter into the patient and pacing
from an external source is a common technique of cardiology. A
number of instrument manufacturers produce clinically acceptable
catheters, and there are several models of Pacemakers well known to
cardiologists and suitable for carrying out this technique.
There have been two basic types of catheters available and in use
for such external, or temporary pacing. A first type is what is
referred to as a unipolar catheter, having one lead extending
substantially the length of the catheter and being electrically
connected to an electrode which is positioned inside the patient's
heart for transmitting the desired electrical signal thereto. This
cardiac electrode is connected through the catheter lead to a first
terminal of a Pacemaker device which, in temporary pacing, is
external to the patient, and which is designed to produce a desired
periodic pacing signal. The second terminal of the external
Pacemaker is connected to an electrode which is generally clamped
to the patient's skin around or near the point of entry of the
catheter, which may be approximately at the large vein opposite the
patient's right elbow. Another suitable site, such as in the
femoral vein, may also be used for catheter insertion. Such
electrode must be maintained in firm electrical contact with the
patient, usually requiring some sort of electrically conductive
paste be applied to the patient's skin, as well as the use of
additional means (such as suturing an electrode beneath the skin at
the site of incision) for maintaining the electrode in firm
position. The time required to attach the second electrode to the
patient's skin is considered, by most physicians, to be at best a
considerable annoyance, and external electrodes attached to the
skin are unreliable and require constant attention. When both the
external electrode and the electrode which is placed in the
patient's heart are connected to the Pacemaker, the periodic output
signals from the Pacemaker terminals produce biopotentials in the
patient's heart of a character so as to induce stimulation of the
heart, i.e., so as to pace the heart.
The second type of standard catheter in common use, and clearly the
preferred type, is what is referred to as a bipolar catheter,
having both electrodes positioned near the distal end of the
catheter, such that when the catheter is fully inserted into the
patient's heart, both electrodes are inside the heart and in proper
position to transmit the desired signal from the Pacemaker directly
to the patient's heart. The advantage of the bipolar catheter over
the unipolar form is the obvious one of eliminating the requirement
of making an external attachment of one electrode to the patient's
skin. Using the bipolar catheter, the two leads of the catheter are
simply connected directly to the external Pacemaker, or to whatever
device is in clinical use.
There are two basic reasons which lead to the conclusion that the
new and novel catheter design of this invention is not only
advantageous but should be required for safe clinical use. The
first of these concerns the phenomenon of induced ventricular
arrhythmias associated with the use of artifical Pacemaker. The
possibility of Pacemaker induced ventricular arrhythmias has been
recognized for some time, but the extent of the clinical risk of
such arrhythmias has not been known. In fact, research has shown
that an electronic Pacemaker stimulus can cause a dangerous
arrhythmia by falling during the vulnerable period of a preceding
ventricular beat. This possibility exists most commonly when an
asynchronous artifical Pacemaker is in competition with normal
sinus rhythm or ectopic beats from any source. The problem is
particularly important in patients requiring pacing during acute
myocardial infarction, as these patients are most susceptible to
life-threatening ventricular arrhythmias.
I have found evidence that ventricular arrhythmias are evoked by
anodal stimulation, which evidence suggests that in the majority of
instances an anode on or within the heart, of size and
configuration to permit anodal stimulation, is necessary to produce
ventricular tachycardia or ventricular fibrillation in humans with
permanent or temporary pacing systems. All the available evidence
points to the anode as the most common site or origin of Pacemaker
induced ventricular fibrillation. Although commercially available
Pacemakers have outputs which are probably too small to produce
arrhythmias in normal human hearts, such units must be designed to
produce stimuli exceeding the excitation thresholds of 90 percent
or more of all patients encountered. With time the excitation
threshold for an implanted electrode system can rise to 10 times
the initial implantation threshold, and therefore Pacemakers are
designed to deliver 10-30 times as great a stimulus as is required
for effective pacing at the time of electrode implantation. Thus,
under adverse conditions, such as acute myocardial infarction,
etc., Pacemaker induced ventricular arrhythmias are possible,
especially if the anode is positioned on or inside the
ventricle.
As a result of the above conclusions, it is clear that only
unipolar cathodal pacing should be used. As most pacing in a
clinical situation is through temporary catheter electrodes, either
a remote indifferent electrode (anode), or catheter with a distal
pacing cathode and a large proximal anode, i.e., an anode at least
ten times the surface area of the cathode, and positioned outside
of the right ventricle, should be used. Since, as was discussed
hereinabove, there is an overwhelming preference for a bipolar type
of cathode which eliminates the requirement of attaching an
electrode externally to the patient's skin, there is a need for a
catheter construction having a first (cardiac) electrode which is
adapted to be positioned within the heart, and a second electrode
positioned such that it will be within the patient's body, but
outside of and proximal to the heart and preferably of greater
surface size than the cardiac electrode. Furthermore, the cardiac
electrode should be used as the cathode, and the proximal electrode
as the anode.
The second discovery which has led to my novel catheter apparatus
design, and method for use of same, relates to the use of demand,
or non-competitive Pacemakers. In the demand Pacemaker, the pacing
signal is generated only upon demand, i.e., when the natural pacing
signal of the patient is not sensed. For ventricular pacing, such
demand Pacemakers are commonly used to avoid competition with sinus
or ectopic beats. Competition between artificial and natural
Pacemakers can result in an unacceptable increase in heart rate and
may precipitate serious ventricular arrhythmias. I have recently
encountered samples of failure of proper demand function in the
post-operative period resulting in either of these complications,
and at each case the failure was due to a low voltage signal coming
from the bipolar electrodes of the catheter in use, and normal
demand function was restored by conversion to a unipolar
system.
Although epicardial voltages in a bipolar system are usually well
in excess of those required for demand function, in any heart
bipolar electrodes can be positioned so as to detect a signal too
small for demand sensing. A bipolar system adequate to detect sinus
beats may not detect beats from a different origin such as ectopic
ventricular beats. However, in every case that I have observed,
regardless of the amplitude of the bipolar electrogram, a unipolar
electrogram could be obtained which was greater in magnitude and
sufficient for proper demand function. Conversion of a bipolar
electrode system to a unipolar system, with only one electrode in
the heart, results in a simple and effective means of increasing
the signal detected by the Pacemaker.
SUMMARY OF THE INVENTION
It is the primary object of this invention to provide catheter
apparatus and a method for artificial pacing of a patient's heart,
which has the advantages of a bipolar electrode system in terms of
ease of clinical use but which avoids the disadvantages of a
bipolar electrode, and particularly which provides that the anode
be outside of the patient's heart, and which provides efficient
pickup for demand pacing.
In accordance with the above object, there is provided catheter
apparatus for pacing of a patient's heart comprising a catheter
having a first electrode, utilized as a cathode, positioned on the
catheter such that it is within the patient's heart when the
catheter is fully positioned, and having a second electrode,
utilized as an anode, and positioned proximal to the first
electrode, having a surface area much larger than that of the
cardiac electrode, and positioned so that it is external to the
patient's heart during the pacing operation. Pacing is achieved by
periodically delivering the pacing signal between a cathode
positioned within the heart and an anode positioned outside of the
heart.
It is another object of this invention to provide an improved
apparatus and method for temporary pacing of a patient by which
pacing signals are generated outside of the heart, transmitted
within the patient through a catheter of improved design, and
connected between a first electrode positioned within the patient's
heart and a second electrode positioned within the patient and
outside of the patient's heart.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic sketch showing the placement of a catheter
within a human body, and which indicates the critical areas of
electrode placement according to this invention.
FIG. 2 is a sketch showing the catheter apparatus of this invention
in combination with an artificial Pacemaker.
FIG. 2a is a detail sketch showing the connection of the anode of
the catheter of this invention to one of the catheter electrical
leads.
FIG. 2b is a detail sketch showing the connection of the cathode of
the catheter of this invention to the other of the catheter
leads.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, there is shown a diagrammatic sketch of a
catheter 20 inserted into a human. Most commonly, the catheter is
inserted at about position 21, into the right basilic vein. The tip
of the catheter is manipulated through the superior vena cava, the
right atrium, and into the right ventricle. The catheter may also
be introduced through the external (or internal) jugular veins,
subclavian veins, or femoral veins. At the end portion of a bipolar
catheter external to the body a pair of electrical leads (or one
lead for a unipolar) are connected to the Pacemaker for pacing.
There are a number of commercially available Pacemakers which may
be used in the practice of this invention. Such Pacemakers, and
their manner of use, are well known to cardiologists.
In a commonly used prior art bipolar catheter, the two electrodes
are both caused to reside in the right ventricle, as shown at 24,
25. When a prior art unipolar catheter is utilized, there is only
one heart electrode, such as 24, and a second electrode is placed
upon the patient's skin near the point of entry at 21. The same
catheter apparatus is utilized for demand pacing.
Referring now to FIG. 2, there is shown a diagrammatic sketch of
the catheter 30 utilized in the practice of this invention,
connected to a Pacemaker 32. Pacemaker 32 may be either a
conventional Pacemaker type device or a demand type Pacemaker
device. The catheter is an elongated and flexible instrument,
constructed preferably of a plastic material such as nylon or
Teflon, and of generally tubular form with substantially constant
outer diameter fron end to end. The catheter of this invention has
two electrical leads 34, 35, constructed of electrically conductive
material, and embedded in the non-conductive plastic material. The
larger of the two electrodes, 38, suitably a cylindrical ring, of
conductive material, is positioned so that when the catheter is in
place within the patient, it is outside of the patient's heart. It
is connected to a first of the catheter leads, 34, as shown in FIG.
2a, which in turn is connected to the positive terminal of
Pacemaker 32, such that it is the anodal electrode. At the far
distal end of the catheter, near the tip thereof, is an electrode
40, which also is suitably a ring of conductive material around the
outside of the catheter, and in electrical contact with the other
of the two conducting leads, 35, as shown in FIG. 2b. Lead 35 in
turn is connected to the negative terminal of Pacemaker 32, such
that electrode 40 is the cathodal electrode. This electrode is of
relatively small surface area, and typically has a width of about
1-3 millimeters. For a catheter with outside circumference of
approximately 6-10 millimeters, the total surface area would be
approximately 6-24 square millimeters.
In accordance with the discussion hereinabove, and in order to
achieve the purpose of avoiding anodal stimulation of the heart, it
has been found that the second electrode, which is used as the
anode, should be placed preferably at least 4 centimeters proximal
to the heart (to the right atrium). This point is indicated in FIG.
1 by the dashed line indicated at 50. In addition, to accommodate
the occurrences where the catheter may be introduced through the
subclavian vein, the anode should not extend beyond the region
indicated approximately by the dashed line 52. For a typical human,
the distance from the distal electrode (cathode) to dashed line 50
is about 23 centimeters, and the distance from dashed line 50 to
dashed line 52 is about an additional 6 centimeters. Accordingly,
the proximal electrode (anode) is suitably placed within this 6
centimeter distance (but need not be that long). For a catheter
having an outside diameter of 2-3 millimeters, the surface of the
anode should be about 100-300 square millimeters.
It is highly desirable that the proximal anode be much larger in
surface area than the cathode, in order to distribute the
anodal-induced, or positive-induced electric field intensity, so as
not to stimulate surrounding structures. By making the anode at
least about 10 times as large as the cathode in surface area, this
is achieved.
In practice, the distal electrode of the catheter is made the
cathode by connecting it to the negative terminal of the Pacemaker
32, and the proximal electrode is made the anode by connecting it,
through lead 35, to the positive terminal of Pacemaker 32. It is
seen that, in clinical use, the apparatus of this invention
provides that the anode is positioned safely outside of the
patient's heart, and preferably at least 4 centimeters away from
the patient's heart, while the cathode is positioned within the
patient's right ventricle. By thus placing the anode outside of the
heart, and in addition providing the anode with a surface area much
larger than that of the cathode (so as to reduce electric field
concentration around the anode) the possibility of anodal
stimulation of the heart is effectively eliminated, and cathodal
pacing is ensured. At the same time, however, the apparatus of this
invention provides the advantages of the bipolar catheter, in that
both electrodes are permanently affixed to the catheter, and there
is no need for external placement of an electrode upon the
patient's skin. At the same time, the positioning of the electrodes
in accordance with this invention provides an effective unipolar
type of pickup from the heart, so that when the catheter apparatus
of this invention is used with a demand Pacemaker, the danger of
detection of less than threshold signals is substantially
reduced.
It is to be understood that in order to ensure against anodal
stimulation, it is desirable both to remove the anode from the
vicinity of the heart and to make the surface area of the anode
large. Although the design as shown in FIG. 2 is considered to be
the best and safest design, it is to be understood that improvement
over prior art forms of catheters may be achieved with various
compromise designs. For example, if the anode were to extend into
the heart, but had a large and extended surface area such as would
be obtained if the anode were continuous almost to the point of
entry, the distribution of the large anode surface would mitigate
against anode stimulation. Similarly, simply positioning the anode
outside of the heart, but making it of the same order of magnitude
and surface size as the cathode, would achieve some improvement
over the prior art. While the design criterion of positioning the
anode at least 4 centimeters external to the heart is a critical
limitation necessary to ensure a factor of safety against anodal
stimulation, placement of the anode within less than 4 centimeters
of the heart would still be an improvement over the prior art in
accordance with the principles of this invention. Similarly, the
design criterion of making the anode at least 10 times as great as
the cathode is also a critical limitation necessary to ensure
against anodal stimulation, but use of an anode of lesser size
would still be within the broad scope of this invention.
* * * * *