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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3683_Библиотеки_им_академика_М_И_Перельмана
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FIG. 8.4 Cannulation of the right axillary artery.
Technique
On cardiopulmonary bypass with the heart decompressed, preliminary evaluation is made. The need for any
concomitant additional procedures, such as coronary artery bypass grafting, must be noted. The conduct of the
surgery should be choreographed precisely at this time.
When the nasopharyngeal temperature reaches 18°C to 24°C, the patient is placed in the Trendelenburg
position. The heart-lung machine is halted, and retrograde cerebral perfusion or selective antegrade axillary
perfusion is started. A transverse or longitudinal aortotomy is made on the anterior aspect of the aortic wall (Fig.
8.5). When
dissection is present, the false lumen may be entered first. This necessitates opening of the true lumen.
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FIG. 8.5 The aortic aneurysm is opened transversely.
Clamping of the Aorta
The aorta should be clamped only if there is a localized aneurysm of the ascending aorta with a generous normal
distal segment. Only under this very precise condition should the aorta be cross-clamped. Deep circulatory arrest
with retrograde cerebral perfusion is used when the ascending aortic aneurysm fades away into the arch or
involves the arch as well, as in all patients with aortic dissection.
Aortic Cross-Clamp Injury
Application of a clamp to the aorta in the presence of acute aortic dissection further traumatizes the aortic wall. In
addition, it may pressurize the false lumen and result in progression of the dissection and possible obstruction of
some aortic branches or even aortic rupture.
Blood Clots in the Aortic Wall
Blood clots are often evident within the aortic wall. In patients with aneurysms, the clots may be old and
organized. They must be carefully removed along with atherosclerotic debris to prevent possible subsequent
embolization.
Myocardial Protection
Cold blood cardioplegic solution may be administered antegrade into each coronary artery if deemed necessary.
This is especially important if the dissection has involved one of the coronary ostia because the myocardium fed
by this vessel may not have cooled sufficiently owing to obstructed flow. Retrograde infusion of cardioplegia into
the coronary sinus should also be performed.
If the cardioplegic line is used for the retrograde cerebral perfusion with cold blood, this will have to be
delayed until the cardioplegic infusion is completed and the line purged of cardioplegic solution.
The entry site of the aortic dissection is identified. The dissection may have extended into the aortic arch and the
aortic root involving a coronary ostium, most commonly that of the right coronary artery. The aorta is resected
from just above the sinotubular ridge to the level of the innominate artery.
The divided aortic wall may at times be left in situ to be reapproximated loosely over the tube graft at the
completion of the procedure. This technique may provide added protection from possible mediastinal infection.
Typically, the lesser curvature of the aortic arch is resected to remove as much diseased aorta as possible. A 1-
cm cuff of relatively normal aorta is dissected with as much adventitial tissue as possible left intact for the distal
anastomosis.
Reinforcement of the Aortic Wall
If the distal aortic wall is dissected, BioGlue Surgical Adhesive (CryoLife, Inc., Kennesaw, GA) is injected into the
false lumen to bond and strengthen the aortic wall (Fig. 8.6). A sponge is placed in the true lumen to prevent
spillage.
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FIG. 8.6 Injection of glue into the false lumen to bond and strengthen the aortic wall.
The sponge within the lumen of the aorta is gently pressed against the aortic wall in close proximity to the
coronary ostia to prevent the glue material from occluding the coronary arteries.
Glue Embolization
Glue material is not introduced within the dissected distal wall of the aorta if there appears to be reentry sites
within the aortic arch. The possibility of glue material becoming detached and embolized through the distal
reentry site is a grave complication of this procedure.
Further reinforcement can be obtained with Teflon felt strips attached to both the inside and/or outside of the
aortic wall first with 6 to 10 interrupted mattress sutures or a continuous mattress suture of 3-0 Prolene (Fig. 8.7).
Teflon felt strips may not be required if the integrity of the aortic wall appears to be satisfactory with the glue.
Alternatively, the outer adventitial layer of the dissected aorta can be cut longer than the inner intimal layer. This
layer is then folded into the true lumen and sewn in place with interrupted mattress sutures (Fig. 8.8).
An appropriately sized Hemashield tube graft is cut and tailored obliquely to be attached to the undersurface
of the arch or cut straight to be attached to the aorta at the level of the innominate artery. The tube graft is then
anastomosed to the reinforced aortic cuff with a continuous 3-0 Prolene suture.
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FIG. 8.7 Reinforcement of the distal aorta with double layers of Teflon felt.
Tension on the Suture Line
It is important for the assistant surgeon to follow the suture meticulously to provide appropriate tension on the
suture line. Otherwise, multiple reinforcing interrupted sutures may be required to ensure a watertight
anastomosis.
With the patient in the Trendelenburg position, the perfusion of retrograde cerebral blood is allowed to
accumulate and fill the aortic arch. All air and debris are allowed to flow out through the graft. At this time,
another arterial cannula is introduced through the tube graft, and the perfusionist is asked to initiate arterial
perfusion through this cannula in an antegrade manner with extremely low flow. A clamp is now applied to the
tube graft well away from the anastomosis and proximal to the cannula, and the retrograde cerebral perfusion is
gradually discontinued and venous drainage is reinstituted (Fig. 8.9). Normal perfusion flow and pressure are
gradually restored, and the patient is rewarmed. The posterior distal suture line is now examined, and additional
stitches are placed for control of hemostasis if required.
In patients with aortic aneurysm, the femoral arterial cannula may be used to reinstate cardiopulmonary
bypass. This retrograde arterial perfusion is gradually increased to normal flow, and rewarming is started. While
not essential, antegrade perfusion with a separate cannula through the tube graft allows earlier removal of the
femoral arterial cannula and repair of the femoral artery, reducing the risk of limb ischemia.
Retrograde Arterial Perfusion and Aortic Dissection
In patients with aortic dissection, blood gains access through the entry site into the aortic wall. This dissection
may result in a reentry site by tearing the intima distally along the course of the aorta. When cardiopulmonary
bypass is reinitiated, the retrograde flow may enter the false lumen through this distal intimal tear and reenter the
lumen at the entry site. However, when the aorta has been repaired and the entry site is excluded by tube graft
interposition, the retrograde flow of blood cannot escape and may cause further dissection of the aorta.
Therefore, it is important to establish antegrade flow within the true lumen when resuming cardiopulmonary
bypass.
If right axillary artery cannulation has been used, the tube graft can be filled by removing the clamp on the
innominate artery. The graft is then cross-clamped, and full flow is resumed.
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After cardiopulmonary bypass is reestablished, additional doses of blood cardioplegic solution are
administered by the retrograde technique and antegrade into the
coronary ostia at 10- to 20-minute intervals (see Chapters 3 and 5).
FIG. 8.8 Reinforcing aortic wall with adventitial layer.
FIG. 8.9 Completion of proximal anastomosis. Inset: Resuspension of an aortic valve commissure.
When the aorta is otherwise normal and there is no aortic valve insufficiency, the proximal aorta that has been
transected at approximately 1 cm above the level of aortic commissures is reinforced with glue and a single or
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double layer of Teflon felt, as described for the distal anastomosis. The tube graft is tailored to an appropriate
length and anastomosed to the proximal aorta with 4-0 Prolene continuous suture (Fig. 8.9).
Often, however, there may be associated aortic insufficiency due to aortic root dissection or dilation. When the
valve leaflets are not diseased and the remainder of the aortic root is normal, every attempt is made to retain the
aortic valve. Any incompetent commissure is resuspended by curing the dissected root with BioGlue and
reinforced with an external felt strip. Usually, a single pledgeted Prolene suture is placed immediately above
each of the commissures and tied down in order to resuspend the commissural posts further. This tailored
proximal anastomosis reestablishes a new sinotubular junction, incorporating the resuspended commissures to
ensure a competent aortic valve (Fig. 8.9).
AORTIC ROOT REPLACEMENT
When the aortic valve is diseased beyond repair or the dissection extends proximally into the sinuses, complete
aortic root replacement with an valved conduit and reimplantation of the coronary arteries become necessary.
Aortic root replacement as originally described by Bentall consisted of replacement of the aortic valve and the
ascending aorta including the aortic root, and reimplantation of the coronary arteries into the tube graft all within
the native aorta. The tube graft was then wrapped with the redundant aortic wall. There appears to be an
increased incidence of pseudoaneurysm formation, probably because of insecure hemostasis at the anastomotic
suture lines masked by the wrapping of the aorta. With the introduction of improved tube grafts and aortic root
conduits as well as better surgical techniques for anastomosis and hemostasis, simple interposition of a valve
conduit is now the method of choice.
The Interposition Technique
The aorta is divided approximately 15 mm above the commissures, followed by excision of all the diseased aortic
wall up to the lesser curvature of the aortic arch. Buttons of aortic wall, approximately 1.5- to 2-cm wide,
containing the coronary artery ostia are detached from the aortic root with an electrocautery. The aortic valve
leaflets are excised and an appropriately sized composite tube graft is selected. St. Jude Medical (Minneapolis,
MN) provides a collagen-impregnated tube graft (Hemashield) attached to a bileaflet valve with a tall sewing cuff.
Interrupted
pledgeted sutures of 2-0 Ticron are placed close together in the aortic annulus (Fig. 8.10). Subsequently, they
are passed through the lower portion of the sewing ring of the composite valve graft, leaving 2 to 3 mm of the
upper sewing cuff free. The prosthesis is lowered into position, and the sutures are tied, taking all the
precautions as in aortic valve replacement (see Chapter 5).
FIG. 8.10 Technique for aortic root replacement: Placement of annular sutures in valve conduit.
Six to eight millimeter of the aortic wall should be left attached to the annulus. This remaining aortic wall with
its adventitial tissue is now brought forward and sewn to the upper portion of the sewing ring of the prosthesis
with a continuous 3-0 Prolene suture (Fig. 8.11). The suture should go through in the order of adventitia,
annulus, sewing ring, and then back outside of the folded adventitia. In addition, a Teflon strip can be used to
buttress the proximal suture line (Fig. 8.12). This reduces the possibility of leaks at the aortic root.
FIG. 8.11 Technique (modified Copeland) for reinforcing the proximal suture line.
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FIG. 8.12 Copeland technique reinforced with a felt strip.
Circular holes are made in the tube graft with an ophthalmologic cautery device for reimplantation of the coronary
artery buttons. These openings should preferably be some distance above the sewing ring for ease of suturing.
The coronary artery buttons are now attached to these openings with continuous 5-0 Prolene sutures (Fig. 8.13).
FIG. 8.13 Technique for aortic root replacement: Reimplantation of coronary ostial buttons.
Often, this suture line is buttressed and reinforced with a strip of autologous pericardium or a narrow strip of
felt on the coronary button for a more secure anastomosis.
It is often advisable to delay reimplantation of the right coronary button until the distal aortic anastomosis is
completed. The cross-clamp is briefly removed, and the heart is allowed to fill so that the correct site for
reimplantation of the right coronary can be marked.
Bleeding from the Coronary Artery Suture Line
Implantation of the coronary artery buttons on the graft must be performed meticulously. The suture bites must
be very close together and preferably buttressed with a pericardial strip. Control of bleeding from these sites,
particularly the left coronary artery anastomosis, at a subsequent stage is challenging. Application of BioGlue to
the suture line may assist in hemostasis.
The tube graft is now cut appropriately and attached to the distal aorta as described earlier. If a tube graft is
already attached to the distal aorta, the proximal and distal tube grafts are now tailor cut and anastomosed to
each other with a continuous 3-0 or 4-0 Prolene suture.
Composite Valve vs. Tube Graft Interposition
Many of these patients have diffuse aortic wall disease. Use of the composite valvular conduit should be
preferred to isolated aortic valve replacement followed by tube graft replacement of the aorta above the
sinotubular junction. This latter technique may leave behind diseased sinuses of Valsalva and put the patient at
risk of later development of aortic sinus aneurysms.
Inability to Directly Connect the Coronary Arteries to the Tube Graft
Composite valvular tube graft replacement entails reimplantation of the coronary arteries into the graft. Use of
saphenous vein grafts to bypass the major branches of the coronary arteries can be an alternate technique and
is implemented whenever direct coronary artery to graft continuity cannot be safely accomplished. This entails
the oversewing of the coronary ostia. An alternative technique uses a short segment (less than 1 cm in length) of
an 8-mm Hemashield tube graft interposed between the coronary ostia and the aortic graft. This has been found
to be useful in some patients in whom the coronary buttons are difficult to mobilize.
Coronary Artery Implantation
A kink or twist of the coronary arteries at the implantation site interferes with normal coronary perfusion and can
give rise to myocardial ischemia. The surgeon must be aware of this possibility during anastomosis of the
coronary ostia to the graft to prevent misalignment.
Stenosis of the Coronary Artery Ostia
To minimize the possibility of ostial stenosis, the anastomosis should incorporate a wide margin of the aortic wall
around each coronary ostium. The window that is cut in the graft wall must be correspondingly generous (Fig.
8.13).
Saphenous Vein Bypass Grafts
When the patient has associated coronary artery disease, it may be necessary to use saphenous vein grafts or
appropriate arterial grafts to bypass the occluded branches of the coronary arteries concomitantly with the aortic
surgery.
As the patient is rewarmed and all suture lines are secured, deairing is carried out and the patient is gradually
weaned from cardiopulmonary bypass.
Aortic root venting is performed with an air vent needle through the graft before removing the clamp across
the tube graft. The clamp is then reapplied partially across the anterior portion of the graft distal to the needle
vent (see Venting and Deairing of the Heart section in Chapter 4).
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Air Removal
The vent needle for air removal should not be inserted in the aorta distal to the graft to avoid starting a new site
of dissection.
Techniques for Aortic Root Replacement with a Bioprosthesis
When a tissue valve is preferred during concomitant valve and root replacement, a stented porcine or bovine
pericardial valve is sewn inside a Hemashield tube graft. Generally, a tube graft 3 mm larger than the
bioprosthesis is chosen for a proper fit. The valve is placed inside the tube graft, which is sewn to the top of the
sewing ring using a running 4-0 Prolene suture. It is important to mark the tube graft at 0, 120, and 240 degrees,
where the struts of the bioprosthesis will be aligned. After tying down two knots, one arm of one suture is sewn
along one half of the sewing ring while the other arm secures the other side (Fig. 8.14A, B). This handmade
composite valve graft conduit is then implanted as described for the mechanical composite valve graft.
Alternatively, the aortic valve and root can be replaced with a stentless aortic root bioprosthesis. A series of
simple interrupted 4-0 Ticron sutures are placed closely in a planar manner at the level of the annulus and below
the commissures. The sutures are then passed through the Dacron skirt of the appropriately sized stentless
valve. The bioprothetic root is lowered and the sutures tied over a strip of Teflon felt. The coronary stumps of the
bioprosthesis are removed and the coronary buttons are reimplanted into their respective openings using 5-0
Prolene sutures. The bioprosthesis can be extended with a
Hemashield Dacron tube graft, if necessary, to replace the ascending aorta.
FIG. 8.14 Constructing a bioprosthetic valve conduit.
The Freestyle bioprosthesis can usually be oriented in its anatomic position without tension on the coronary
button anastomoses. In fact, the outpouching nature of bioprosthetic coronary stumps reduces the need for
extensive mobilization of the coronary artery buttons. However, when the native coronary buttons are more than
120 degrees apart as in a congenitally bicuspid valve, the stentless valve should be rotated 120 degrees. For
reattachment of the coronary artery buttons, only one of the coronary stumps is removed and a second opening
is made in the noncoronary sinus of the bioprosthesis using a 4-mm aortic punch. The remaining coronary stump
is reinforced with a 5-0 Prolene suture.
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