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Claims  |
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What is claimed:
1. A method for performing coronary artery bypass graft surgery on a
patient's beating heart, wherein a fluid communicating graft is made
between an arterial blood supply and the coronary artery distal from a
stenosis, comprising the steps of:
locating a position on the patient's vagus nerve that, when electrically
stimulated, will cause a momentary stoppage or substantial reduction in
the beating of the patient's heart; and
applying an electrical stimulation to the position on the patient's vagus
nerve at least once during the construction of the fluid communicating
graft to cause the momentary stoppage or substantial reduction in the
beating to facilitate construction of the graft.
2. The method of claim 1 wherein the construction of a fluid communicating
graft comprises the step of forming an anastomosis between the arterial
blood supply and the coronary artery.
3. The method of claim 2 wherein the step of forming comprises a series of
suturing steps wherein the vagus nerve is stimulated before each of the
suturing steps.
4. The method of claim 2 wherein the step of forming comprises a series of
suturing steps wherein the vagus nerve is stimulated before at least one
of the suturing steps.
5. The method of claim 1 wherein each step of applying lasts for a period
of about 10 or less seconds.
6. The method of claim 1 wherein the stimulations are intermittently
applied with at least several seconds between stimulations.
7. The method of claim 6 wherein the stimulation is applied to the
patient's vagus nerve in the form of a pulse train of selected frequency
and electrical energy.
8. The method of claim 1 further comprising the step of:
applying a heart pacing electrical signal to the patient's heart during the
step of applying an electrical stimulation to revive the heart in the
event that it is slow to resume beating after the momentary stoppage or
substantial reduction in beating.
9. A method for performing coronary artery bypass graft surgery on a
patient's beating heart, wherein a selected surgical procedure is
performed to provide a fluid communicating graft, comprising the step of:
momentarily arresting or substantially slowing the beating of the patient's
heart for a precisely controlled period of time without the need for
cardiopulmonary bypass support to provide access to the stopped or slowed
heart to facilitate performing the selected surgical procedure.
10. The method of claim 9 further comprising the steps of:
supplying an electrical stimulating signal during the selected surgical
procedure; and
selectively applying the electrical stimulating signal to a selected
position on the patient's vagus nerve during the selected surgical
procedure to stimulate the vagus nerve to induce said momentarily arrested
or substantially slowed beating of the patient's heart.
11. The method of claim 10 wherein said electrical stimulating signal is
applied on the left vagus nerve as it crosses the transverse aorta, just
proximal to the left recurrent nerve branch.
12. The method of claim 10 wherein said electrical stimulating signal is
applied on the deep cardiac plexus of the vagus nerve.
13. The method of claim 10 wherein said electrical stimulating signal is
applied on the cervical portion of the left or right vagus nerve just
proximal to the left or right superior cervical cardiac nerve,
respectively.
14. The method of claim 9 wherein said selected surgical procedure
comprises:
performing an anastomosis between an arterial blood supply and a coronary
artery to effect the selected surgical procedure; and
performing a series of suturing steps in which the patient's heart is
momentarily arrested or substantially slowed before at least one suturing
step of the anastomosis.
15. The method of claim 14 further comprising the step of:
applying an electrical stimulus to the patient's vagus nerve for a period
of from one to a plurality of seconds to purposely effect the momentary
arrest or substantial slowing of the heart before said at least one
suturing step of the anastomosis.
16. The method of claim 9 wherein said selected surgical procedure
comprises:
forming an arteriotomy in a coronary artery to be bypassed; and
applying an electrical stimulus to the patient's vagus nerve for a period
of from one to a plurality of seconds to purposely effect the momentary
arrest or substantially slowing of the heart during said step of forming
an arteriotomy.
17. The method of claim 9 wherein said selected surgical procedure
comprises:
placing ligatures around a coronary artery to be bypassed; and
applying an electrical stimulus to the patient's vagus nerve for a period
of from one to a plurality of seconds to purposely effect the momentary
arrest or substantially slowing of the heart during said step of placing
ligatures.
18. Apparatus for performing coronary artery bypass graft surgery on a
patient's beating heart, wherein a selected surgical procedure is
performed on the patient, comprising:
means for supplying an electrical stimulating signal during the selected
surgical procedure; and
means responsive to the supplying means for momentarily arresting or
substantially slowing the patient's heart for a controllable period of
time during the selected surgical procedure without the need for
cardiopulmonary bypass support.
19. The apparatus of claim 18 wherein:
said means for supplying generates an electrical stimulating signal capable
of stimulating the patient's vagus nerve; and
said means for momentarily arresting or substantially slowing the heart
comprises means for applying the electrical stimulating signal to a
selected position on the patient's vagus nerve during the selected
surgical procedure.
20. The apparatus of claim 19 wherein the applying means comprises
attachment means electrically coupled to said means for supplying for
establishing electrical contact with the patient's vagus nerve to insure
the application thereto of the electrical stimulating signal.
21. The apparatus of claim 20 wherein:
the selected surgical procedure comprises forming an anastomosis between an
arterial blood supply and the coronary artery; and
said applying means further comprises control means for selectively
enabling the application of the electrical stimulating signal to the
patient's vagus nerve via the attachment means at selected times during
the anastomosis.
22. The apparatus of claim 21 wherein the anastomosis comprises a series of
suturing steps in which the vagus nerve is stimulated via the applying
means for about 10 or less seconds prior to at least one suturing step.
23. The apparatus of claim 20 wherein the attachment means comprises
electrically non-conductive clip means embodying an electrically
conductive nerve contacting electrode.
24. The apparatus of claim 20 wherein the attachment means comprises an
electronically insulated surgical instrument embodying an electrically
conductive nerve contacting probe means.
25. The apparatus of claim 20 wherein said attachment means comprises:
a pair of electrically non-conducting members each terminating at one end
in an enlarged handle and at the opposite end in confronting jaws, the
members being secured together in pivotable relation;
electrodes electrically coupled to the supplying means embedded within the
confronting jaws and adapted to make firm electrical contact only with the
vagus nerve; and
spring means for maintaining the confronting jaws and electrodes normally
closed firmly on the vagus nerve.
26. The apparatus of claim 25 further comprising:
applicator means having clip applying jaws for attaching the attachment
means to the vagus nerve; and
wherein said enlarged handles each include, in combination with respective
ends of the clip applying jaws, a spherical ball/depression structure
which enables swiveling the attachment means relative to the applicator
means while still firmly holding the attachment means within the
applicator's jaws.
27. The apparatus of claim 25 wherein:
one of the members comprises a pair of parallel spaced apart jaws each with
its respective electrode embedded in confronting relation therein; and
wherein the confronting jaw and electrode of the opposite member is
laterally disposed between the confronting spaced apart jaws and provides
a gentle shearing force when urged by the spring means towards the
confronting spaced apart jaws to confine therebetween the vagus.
28. The apparatus of claim 25 wherein the electrodes have a circular or
arcuate cross section.
29. The apparatus of claim 25 wherein the electrodes have a square or
rectangular cross section.
30. The apparatus of claim 25 wherein the electrodes comprise selectively
roughened confronting surfaces to enhance their electrical contact with
the vagus nerve.
31. The apparatus of claim 20 wherein the attachment means comprises:
clip means incorporating at least one electrode adapted for electrical
contact with the vagus nerve; and
means for supporting the clip means in selected orientation to allow the
attachment thereof at a predetermined position on the vagus nerve.
32. The apparatus of claim 31 wherein:
said clip means comprises a pair of confronting jaws, with respective nerve
contacting electrodes embedded in the jaws and energized by said supplying
means; and
said supporting means comprises a pair of handles integral with the pair of
confronting jaws, said handles being adapted to open the jaws upon
application of force on the handles to allow said attachment to the vagus
nerve.
33. The apparatus of claim 32 wherein the clip means comprises a jaw with
an embedded electrode generally confronting two laterally spaced jaws with
embedded electrodes which, when attached to the vagus nerve, provide a
slight shearing affect to enhance the attachment.
34. The apparatus of claim 32 wherein the clip means further comprises two
pair of confronting jaws with respective embedded electrodes in the jaws,
wherein one pair of electrodes confronts a second pair of electrodes at a
selected laterally spaced distance.
35. The apparatus of claim 32 wherein the clip means further comprises a
pair of laterally spaced apart jaws with embedded electrodes of selected
positive and negative polarities, and including a confronting paddle
shaped jaw.
36. The apparatus of claim 35 wherein the paddle shaped jaw comprises
electrodes of selected positive and negative polarities embedded therein
which confront the electrodes of the spaced apart jaws.
37. The apparatus of claim 32 wherein the clip means further comprises a
pair of confronting paddle shaped jaws with respective embedded paddle
shaped electrodes of selected polarities.
38. The apparatus of claim 32 wherein said supporting means further
comprises:
applicator means having at a distal end thereof a pair of jaws adapted to
firmly engage said pair of handles to maintain the clip means at said
selected orientation, whereupon application of force by the applicator
means jaws opens the clip means jaws to allow the attachment of the clip
means to the vagus nerve.
39. The apparatus of claim 20 wherein the attachment means comprises:
endoscopic means comprising a lumen therein and having an elongate member
adapted for controllable translation in the lumen; and
wherein a distal end of the endoscopic means comprises nerve contacting
means comprising confronting jaws and electrodes selectively manipulated
by the translation of the elongate member to close upon, and establish the
electrical contact of the electrodes with, the patient's vagus nerve.
40. The apparatus of claim 39 wherein the nerve contacting means comprises:
a cone-shaped cap fixed to a distal end of the elongate member;
a first electrode disposed in the distal end of the endoscopic means and
confronting the cap; and
a second electrode disposed in the cap and confronting the first electrode,
such that translation of the elongate member into the lumen brings the
electrodes together to allow capturing the vagus nerve therebetween.
41. The apparatus of claim 39 wherein the nerve contacting means comprises:
a pair of confronting jaws pivotably secured to a distal end of the
elongate member, said jaws having confronting electrodes of selected
polarities embedded therein; and
said jaws being adapted to close upon translation of the elongate member
and jaws into the lumen, to thus establish the electrical contact between
the electrodes and the patient's vagus nerve.
42. The apparatus of claim 39 comprising an endoscope disposed within the
endoscopic means for providing a view of the jaws and the vagus nerve to
facilitate establishing the electrical contact.
43. The apparatus of claim 20 wherein the attachment means comprises:
endoscopic means comprising a lumen therein and having an elongate member
adapted for controllable translation in the lumen;
said elongate member comprising a pair of spring-like jaws of respective
electrical polarities formed at the distal end of the member, wherein the
spring-like jaws diverge upon their translation from within the distal end
of the endoscopic means; and
said spring-like jaws having notches formed in their ends for capturing the
patient's vagus nerve upon selected rotation of the endoscopic means.
44. The apparatus of claim 20 wherein the attachment means comprises:
a pair of electrically insulated members, said members terminating in
respective sharpened probes adapted to penetrate the patient's vagus nerve
to establish the electrical contact therewith.
45. The apparatus of claim 20 wherein the attachment means further
comprises:
endoscopic means comprising a lumen therein, and having an elongate member
adapted for controllable translation in the lumen;
said elongate member terminating at its distal end in at least one
sharpened probe adapted to penetrate the patient's vagus nerve to
establish the electrical contact therewith.
46. The apparatus of claim 20 wherein the attachment means comprises:
clip means for establishing the electrical contact, said clip means
comprising;
a sleeve member having a laterally protruding jaw and an embedded
electrode;
a second member slidably disposed within the sleeve member and having a
laterally protruding jaw and embedded electrode confronting the sleeve
member's jaw and electrode;
spring means disposed to urge the jaws into a closed condition; and
said second member being translated relative to the sleeve member upon
application of force thereto to allow the attachment of the confronting
electrodes to the vagus nerve.
47. The apparatus of claim 19 further comprising:
means electrically coupled to the patient's heart for supplying a heart
pacing electrical signal to revive the heart during the selected surgical
procedure in the event that the heart is slow to resume beating upon
removal of the momentarily arresting stimulating signal.
48. A system for performing a selected surgical procedure on a patient's
beating heart, comprising:
means for providing at least one opening in the patient's chest which
provides access to the heart and surrounding tissues and vessels,
comprising a coronary artery;
means for providing access to a vagus nerve of the patient;
means for supplying a vagus nerve stimulating electrical signal; and
means detachably attached to the vagus nerve and responsive to the
supplying means for temporarily applying the stimulating signal to the
vagus nerve to temporarily stop or substantially reduce the beating of the
heart during the selected surgical procedure without need for
cardiopulmonary bypass support.
49. The system of claim 48, further comprising an instrument to assist in
connecting via an anastomosis procedure an arterial blood supply to the
coronary artery distal from a stenosis therein.
50. The system of claim 48 wherein the selected surgical procedure
comprises supplying a free graft means having first and second ends,
forming a first anastomosis between the first end of the graft means and
an arterial blood supply and forming a second anastomosis between the
second end of the graft means and the coronary artery.
51. The system of claim 48 wherein the coronary artery is connected to an
arterial blood supply via a series of applied sutures in which the vagus
nerve is stimulated before at least one of the applied sutures.
52. The system of claim 51 wherein a stimulation signal is applied for a
period of about 10 or less seconds.
53. The system of claim 48 wherein the applying means comprises:
clip means electrically coupled to the supplying means for establishing a
detachable but firm electrical contact with the patient's vagus nerve
while being substantially insulated from the surrounding tissues and
vessels.
54. The system of claim 53 wherein the clip means is attachable to one or
more preselected positions on the vagus nerve, the clip means being
adapted to apply the vagus nerve stimulating electrical signal to the one
or more positions such that each position, when stimulated, affects a
respective region of the heart to cause the temporary stoppage or
substantial reduction in the heart beat.
55. The system of claim 53 wherein the clip means include:
a pair of generally confronting jaws of electrically insulating material;
a respective electrode embedded in the confronting jaws and adapted to make
the firm electrical contact with the patient's vagus nerve; and
wherein the supplying means supplies a positive electrical potential to one
electrode and a negative electrical potential to the other electrode.
56. The system of claim 53 further comprising:
spring means integral with the clip means for maintaining the clip means
normally closed; and
means demountably secured to the clip means for overcoming the clip means
normally closed condition to enable the application of the clip means to
the vagus nerve, said spring means maintaining the clip means in said firm
electrical contact.
57. The system of claim 48 further comprising:
means electrically coupled to the patient's heart for applying a heart
pacing electrical signal to the heart during the bypass graft surgery to
revive the heart if needed after the stimulating signal is removed.
58. The system of claim 48 wherein the applying means comprises:
a pair of electrically insulated leads, said leads terminating in
respective sharpened probes adapted to penetrate the patient's vagus nerve
to temporarily apply the stimulating signal thereto.
59. A method of performing coronary artery bypass graft surgery on a
patient's beating heart, wherein a fluid communicating graft is made
between an arterial blood supply and the coronary artery, comprising the
steps of:
providing at least one opening in the patient's chest which provides access
to the arterial blood supply and the coronary artery, and to the vagus
nerve;
forming an anastomosis between the arterial blood supply and the coronary
artery;
electrically stimulating the vagus nerve during the step of forming the
anastomosis to momentarily stop or substantially slow the beating of the
heart;
performing at least one suturing step of the anastomosis during the
momentary stop or substantially slow beating of the heart; and
repeating the steps of electrically stimulating and performing at least one
suturing step until the anastomosis is completed. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
Coronary artery bypass graft (CABG) surgery has become a well known and
conventional procedure, often referred to as "heart bypass" surgery. Such
surgery is performed to relieve a condition in which a partially or fully
blocked artery is no longer effective to transport blood to the heart and
involves removing a portion of a vein from another part of the body,
frequently the saphenous vein, to use as a graft and installing this graft
at points which bypass the obstruction to restore normal blood flow to the
heart. Common though this procedure has become, it is nevertheless
lengthy, traumatic and subject to patient risk. Among the risk factors
involved is the use of cardiopulmonary bypass equipment, i.e., the
so-called "heart-lung machine," to both pump blood and oxygenate the blood
so that the patient's heart may be stopped during the surgery, with its
function performed by the cardiopulmonary bypass equipment.
Prior to the present invention, it has been found possible to conduct CABG
surgery without stopping the heart, i.e., on a beating heart. In such a
beating heart procedure, the function of the heart is maintained and the
cardiopulmonary bypass equipment is not needed to replace that function.
However, since the heart is beating in such a procedure, the surgeon must
cope with the movement of the heart, whether the surgery is a bypass
procedure or any other type of coronary surgery. Thus, it would be highly
advantageous to perform coronary surgery on a stopped heart, but without
causing the patient to endure the lengthy, traumatic and risky procedure
involved in supporting the patient on cardio-pulmonary bypass equipment.
The present invention addresses this problem.
The performance of coronary surgery on the beating heart is described by
Benetti et al in "Coronary Revascularization With Arterial Conduits Via a
Small Thoracotomy and Assisted by Thoracoscopy, Although Without
Cardiopulmonary Bypass", Cor. Europatum, 4(1):22-24 (1995), which is
incorporated herein by reference and by Westaby, "Coronary Surgery Without
Cardiopulmonary Bypass" in the March, 1995 issue of the British Heart
Journal which is incorporated by reference herein. Additional discussion
of this subject matter can be found in Benetti et al, Chest, 100(2):312-16
(1991), Pfister et al, Ann. Thorac. Surg., 54:1085-92 (1992), and Fanning
et al, Ann. Thorac. Surg., 55:486-89 (1993). These articles discuss the
further details of grafting by anastomosis of a saphenous vein or mammary
artery to diseased coronary arteries including the left anterior
descending artery (LAD) or the right coronary artery (RCA), temporary
occlusion of the coronary artery to provide a bloodless anastomotic field,
use of a double suture placed above and below the point of anastomosis,
and use of a running suture for the anastomosis. These articles also
contrast the beating heart procedure to the more widely used CABG method
performed on the non-beating heart with cardiopulmonary bypass.
SUMMARY OF THE INVENTION
In heart surgery performed while the heart is beating, the surgeon is faced
with a moving organ which places increased demands on his skill in
performing the desired procedure, e.g., an anastomosis of the left
anterior descending artery (LAD) to the internal mammary artery (IMA), or
anastomosis of both ends of a free graft means to a target artery and a
coronary artery. If, without substantial harm to the patient, the heart
could be momentarily substantially stopped or slowed while the surgeon
performed the desired task, e.g., taking a stitch or stitches with a
suturing needle, such a task would be less difficult to accomplish.
The intentions of the present invention are to provide a surgical procedure
in which the heart is momentarily substantially stopped or slowed in a
predictable and reliable manner to facilitate the surgery, by electrically
stimulating the vagus nerve. This stimulation can be accomplished by first
gaining access to the vagus nerve in the chest preferably via the
thoracotomy used in the surgery, or in the neck through endoscopic
procedures or through a small incision. A suitable electrical stimulating
device is then used to briefly apply electric energy to the vagus nerve.
For example, separate continuous electrical pulse trains of 10 or less
seconds may be intermittently applied to the nerve with, for example, 30
second rest periods between each stimulation. A 50 millihertz current may
be used, but the present invention is not limited to any particular
quantitative amount of electrical energy. The present invention further
provides associated apparatus in the form of various clip or probe means
for efficiently electrically coupling the nerve stimulating device or
insulated pacing wires to a patient's vagus nerve.
The time of the stimulation and amount of current applied will vary
according to the type of surgery and the nature of the task for which the
substantial stopping or slowing of the heart is desired. In any event, the
normal sinus rhythm of the heart is rapidly restored by natural forces
once the stimulation is terminated. Thus, for repetitive tasks such as
stitching during suturing, the stimulation may be repeatedly applied for
brief intervals during which time the task can be performed under less
difficult conditions than would apply if the heart were beating in a
normal manner.
For reasons of safety, one or more heart pacing devices, such as a Pace
port-Swann pulmonary artery catheter, may be inserted in conventional
fashion to the patient's heart and used to restore the beating of the
heart during the surgery in the event the heart is slow to revive after a
nerve stimulating signal is turned off.
The role of the vagus nerves in the control of cardiac rate and rhythm has
been recognized for more than three centuries. Furthermore, soon after
electrical stimulating devices became available, it was shown that vagal
stimulation caused a reduction in heart rate and, as earlier as 1897, Hunt
carried out a quantitative study of the effects of vagal stimulation on
heart rate; see, for example, Hunt, R., "Experiments on the Relation of
the Inhibitory to the Accelerator Nerves of the Heart", J. Exp. Med.
2:252-279 (1897). An excellent discussion of this phenomenon is found in
Chapter 4, Parasympathetic Control of the Heart, by Levy and Martin, in
Nervous Control of Cardiovascular Function, edited by Randall, Oxford
University Press (1984), which is incorporated by reference herein.
However, in spite of the fact that the effect of vagus nerve stimulation
on heart rate has long been known, it is believed that this knowledge has
not previously been applied to coronary surgery. Rather, vagus nerve
stimulation for other purposes has been employed, e.g., as disclosed in
the Schwartz U.S. Pat. No. 5,330,507 where vagus nerve stimulation is used
in connection with treating arrhythmias, and in the Kendall U.S. Pat. No.
5,458,625 which addresses the use of vagus nerve stimulation for the
alleviation of substance withdrawal symptoms or the provision of pain
relief, stress relief, and/or general muscle relaxation.
Thus, the present invention is believed to be the first use of vagus nerve
stimulation to facilitate coronary surgery, wherein heart motion purposely
is stopped or slowed for preselected momentary periods of time during the
coronary surgery without need for cardiopulmonary bypass support.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating, by way of example only, a vagus
nerve clip in accordance with the invention.
FIG. 2 is a side view of the clip of FIG. 1.
FIG. 3 is a top view of the clip of FIGS. 1 and 2.
FIG. 4 is a cross-sectional end view of the clip of FIGS. 1-3 taken along
section line 4--4 of FIG. 2.
FIGS. 5, 5A, 5B are a partial perspective and two cross-sectional views,
respectively, of the clip of FIGS. 1-4 depicting different electrode
cross-sections.
FIGS. 6, 6A, 6B are a partial perspective and two cross-sectional views,
respectively, of an alternate clip configuration of the invention.
FIGS. 7, 7A, 7B are a partial perspective and two cross-sectional views,
respectively, of another clip configuration of the invention.
FIGS. 8, 8A, 8B are a partial perspective and two cross-sectional views,
respectively, of still another clip configuration of the invention.
FIGS. 9, 9A, 9B are a partial perspective and two cross-sectional views,
respectively, of yet another clip configuration of the invention.
FIG. 10 is a side view illustrating an applicator means for attaching a
clip such as the clips of FIGS. 1-9 to the vagus nerve.
FIG. 11 is a side view illustrating another applicator means employed in
microsurgical procedures for attaching the clip to the vagus nerve.
FIGS. 12-14 are partial perspective views of embodiments and modifications
of clips and applicator means in accordance with the invention.
FIGS. 15-21 are partial perspective views of still further embodiments and
modifications of clips, probes and applicator means of the invention for
endoscopic surgery applications.
FIG. 22 is a simplified view of pertinent internal portions of a patient's
neck and chest, illustrating in particular positions along the vagus nerve
where the clip, or clips, may be attached to effect the intended function
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The vagus nerve stimulation technique and apparatus of the present
invention may be used in open chest coronary surgery where a sternotomy is
used to gain access to the heart, or in closed chest, beating heart
coronary surgery in which a thoracotomy or a stab wound (puncture) is used
to gain access. The following is an exemplary usage of the latter
procedure.
The patient is intubated with a double-lumen endobronchial tube which
allows selective ventilation or deflation of the right and left lungs. The
left lung is deflated to provide access to the heart and the left internal
mammary artery (LIMA). The preferred surgical position of the patient is
right lateral decubitus, 30.degree. from horizontal, with the left arm
above the head.
Surgery begins with a left anterior thoracotomy over the fourth intercostal
space. Other sites are suitable depending on the patient's anatomy,
particularly the fifth intercostal space. A retractor is used to spread
the ribs to provide access to the beating heart. The size of the
thoracotomy varies depending on the patient, but generally is less than 12
cm. The parietal pleura is dissected and separated from the ribs, to
permit the introduction of a thoracoscope through a trocar at the fourth
intercostal space along the medial axillary line. The thoracoscope may be
introduced through other areas such as the fifth through seventh
intercostal spaces, again depending on the patient's anatomy. The
thoracoscope is positioned to provide visualization of the LIMA. The LIMA
is then dissected with suitable instruments introduced through the
thoracotomy. These instruments generally comprise scissors, clippers,
pliers, electrocauteries or other conventional devices useful for the
dissection. It is sometimes useful to make a graft with a radial artery
coming out from the LIMA in a T-form. This allows formation of anastomosis
with multiple coronary arteries such as sequential grafts to the diagonal
(Dx) and circumflex (Cx) arteries.
Following dissection of the LIMA, a small pericardial incision is made to
expose the LAD. Access to the LAD and Dx arteries is typically relatively
easy, requiring an incision of about 5 cm. Access to the Cx artery depends
on the patient's characteristics and location of the vessels. In some
cases, a graft to the Cx artery requires increased rotation of the patient
to the right lateral decubitus and some extension of the pericardial
incision. Heparin, or other suitable anticoagulant, may be administered to
the patient in an appropriate dose such as 1.5 mg/kg.
At this juncture, an arteriotomy is made in the LAD at a point distal to
the obstruction to be bypassed. To prevent excess bleeding and partially
stabilize the vessel, a segment of the LAD is occluded with ligating stay
sutures comprising 2.5 cm lengths of 5/0 polypropylene or other
appropriate ligature material. Vagus nerve stimulation, in accordance with
the present invention, may be performed while making the arteriotomy
and/or while placing the ligatures to facilitate the surgeon in forming a
more precise arteriotomy and/or more accurately placing the ligatures.
Applying tension to the ligatures helps stabilize the LAD even though the
heart is beating. Other conventional means for occluding and stabilizing
the artery may be suitable as well. Furthermore, forceps are also
introduced through the thoracotomy to further stabilize and retract the
LAD. A scalpel is then introduced to perform an arteriotomy in the LAD. An
anastomosis between the LIMA and the LAD is then performed by suturing
with 7/0 polypropylene using a needle manipulated by a forceps.
Here again, the vagus nerve stimulation in accordance with the invention is
used to temporarily stop or slow the heart to reduce motion in the
anastomotic field, such that one or more suturing stitch(es) is/are taken
immediately after stimulation when the heart's motion is temporarily
stopped or substantially reduced. The number of stitches required may
dictate the number of occasions on which electrical stimulation of the
vagus nerve will be desirable as well as dictate the duration of the
individual electrical stimulations. This in turn, generally requires
intermittent electrical stimulation of the nerve, with a selected
plurality of seconds, e.g., 30, of rest between stimulations. However,
only one electrical stimulation may be necessary throughout the placement
of the suturing stitches. It is to be understood that the vagus nerve
stimulation in accordance with the invention may be used during other
cardiac surgery procedures in which it is desirable to provide a stable
surgical site by arresting or substantially slowing the beating of the
heart. One such procedure is the procedure for performing the previously
mentioned arteriotomy in the LAD or the placement of ligatures around the
LAD. The technique and apparatus for applying the stimulating electrical
impulses to the vagus nerve in accordance with the invention are discussed
below with reference to the various figures.
Upon completion of the anastomosis, the anticoagulant is reversed, if
necessary, by suitable means such as the injection of protamine. The
hemostasis should be carefully controlled. The thoracotomy is closed by
conventional means. If the pleura has not been breached, a small tube for
drainage may be left in place and removed the same day as the surgery. If
the pleura is open, a larger tube should be left in place for 24 hours.
The drainage tube may be introduced through the small incision for the
thoracoscope.
In the foregoing procedure, the electric stimulator, e.g., of the type
disclosed in the U.S. Pat. No. 5,458,625 may be attached to the patient's
ear, neck, or other points of access to the vagus nerve as further
disclosed below. The electrodes used to stimulate the vagus nerve may be
invasive, e.g., needles or non-invasive clips, examples of which are
described below with reference to the figures. The electrical energy
supplied to the vagus nerve will vary with the type of equipment used, the
point in the body at which access to the vagus nerve is obtained, etc. and
it is to be understood that the practice of the present invention is not
limited to any particular values. Rather, the appropriate amount of
electrical energy needed to achieve the desired result can be readily
determined empirically once the type of equipment, point of access, etc.
are known. By way of example only, the electrical stimulation applied to
the nerve may be derived by a continuous five second train of electrical
pulses at 25 Hertz (Hz), 20 volts, with a pulse width of 0.1 millisecond
(ms) delivered, for example, by a Grass Model SD9J Stimulator manufactured
by Grass, Inc., W. Warwick, R.I.
FIGS. 1-5 illustrate by way of example only, one embodiment of a vagus
nerve clip for detachably attaching the leads of a nerve stimulator
device, or similar electrical impulse generating device, to a patient's
vagus nerve to momentarily stop or slow the heart in accordance with the
present invention. The intent of the invention is to facilitate an
otherwise beating heart coronary surgery procedure, without the need for
cardiopulmonary bypass support usually required in CABG surgery where the
heart is arrested for the entire surgery. The clip is minimally invasive
while still providing precise and efficient electrical contact with the
vagus nerve. It is to be understood that although a detailed description
is made herein relative to the specific clip configuration of FIGS. 1-5,
the underlying features illustrated in the FIGS. 1-5 and the attendant
functions and advantages thereof, are equally applicable to the clips and
probes of other configurations illustrated in part in, and not limited to,
FIGS. 5A through 9B and 12-21.
As relates to cardiac function, the right vagus nerve primarily controls
the sinoatrial (SA) node, while the left vagus nerve controls the
atrioventricular (AV) node of the heart. The AV node seems to be the most
effective in arresting the heart in accordance with the invention. As an
example of the method of practicing the invention, the heart has been
stopped for about 40 seconds at a time by electrical stimulation at, for
example, clip position #1 (FIG. 22) allowing for two or three suture bites
to be taken. Stimulating the right vagus nerve shuts down the SA node, but
breakthrough regulation coming from the AV node at a rate of 50 to 60
beats per minute may make the right vagus nerve stimulation less effective
in arresting the heart. The heart can be stopped without stimulating all
of the parts of the vagus nerve complex that feed to the heart. It follows
therefore, that the use of a single clip at a selected clip position, as
further discussed with respect to FIG. 22 below, generally is satisfactory
to arrest the heart in accordance with the invention. However, more than
one clip may be employed at various locations along the vagus nerve.
In FIG. 1, an embodiment of a vagus nerve clip 12 is depicted in
perspective view properly attached in electrical contact to a preselected
portion of a vagus nerve 14. As mentioned supra, various sites or
positions for attachment of the clip, or clips, are available along the
lengths of the right and/or left vagus nerves, with preferred attachment
positions being those which are readily accessible and/or which, when
stimulated, sufficiently eliminate the stimulus from the brain to the
heart to achieve the desired function and results of the present
invention. The various preferred clip attachment positions for achieving
the required vagus nerve stimulation will be further discussed below
relative to FIG. 22.
Referring to FIGS. 1-4, the clip 12 includes a pair of co-acting members
16, 18 pivotable about a common pin 20. Member 16 includes a handle 22 at
one extremity thereof and a grasping jaw 24 at the opposite extremity
thereof. Likewise, member 18 includes a handle 26 and a grasping jaw 28 at
an opposite extremity thereof. The proximal ends of the handles 22, 26 are
provided with relatively large diameter grips 30, 32, respectively, which
include respective spherical depressions 34, 36. The large diameters and
the associated spherical depressions provide a gripping configuration for
receiving the complementary working ends of a suitable clip applicator,
such as those further described below in FIGS. 10, 11. In addition, the
relatively large diameter handles/depressions allow the clip 12 to be
manually grasped by a surgeon for manual placement of the clip o | | |
