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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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and posterior targets can be visualized. The flexible joint at the hinge point of the apex device allows the heart to
freely twist about its long axis.
FIG. 9.68 Strategic placement of deep pericardial sutures.
FIG. 9.69 An apical suction device for exposing lateral and posterior vessels.
Mechanical stabilization
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There are several devices that can locally immobilize the target coronary artery during off-pump surgery. The
Acrobat System (Maquet Cardiovascular, Wayne, NJ) utilizes both suction and compression (Fig. 9.70) to
stabilize the target vessel. The Octopus System (Medtronic, Inc. Minneapolis, MN) obtains stabilization by
applying high-pressure suction to the surrounding tissue through multiple suction cups (Fig. 9.71).
Stabilizer Myocardial Injury
It is important that the stabilizer is used for local immobilization of the myocardium only. It should not be used as a
retraction device, which may cause hemodynamic compromise.
Anterior Vessels
Left Anterior Descending and Diagonal Branch
Generally, the anterior vessels are grafted first. Revascularization of the LAD artery with the internal thoracic
artery allows immediate perfusion of a sizable portion of the myocardium.
Sometimes the diagonal artery may need to be grafted before the LAD artery because the internal thoracic
pedicle
can make placement of the stabilizer for immobilization of the diagonal branch difficult.
FIG. 9.70 Target stabilization using compressive forces.
FIG. 9.71 Target stabilization using high-pressure suction.
FIG. 9.72 Exposure and stabilization of the left anterior descending artery.
These anterior branches are exposed by gentle traction on the deep pericardial sutures to rotate the apex of the
heart into the surgical field. The stabilizer is placed on the target site with the tips toward the base of the heart
(Fig. 9.72).
The LAD artery is usually grafted at the distal one-third to one-half where the vessel normally emerges from
its intramyocardial location. Occasionally, grafting of the artery is required more proximally. Proximal occlusion
with a soft silastic tape (see subsequent text) is performed before arteriotomy as significant coronary bleeding
may occur. Many surgeons routinely use intraluminal shunts to minimize distal bed ischemia.
Ramus Intermedius and High Obtuse Marginal Branches
These are often intramyocardial and require grafting near the base of the heart that cannot be mobilized into the
field. However, displacement of the heart into a vertical position allows easier access for arteriotomy and
suturing. The stabilizer is placed with the tips toward the base of the heart (Fig. 9.73). Placing the patient in
Trendelenburg position and rotating the table toward the surgeon may facilitate exposure.
Injury to the Left Atrial Appendage
Although the stabilizer can be positioned with the heel toward the base of the heart, bleeding from the left atrial
appendage can occur if it is allowed to rub against the stabilizer arm (Fig. 9.74).
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FIG. 9.73 Exposure and stabilization of the ramus intermedius and high obtuse marginal branches.
FIG. 9.74 Injury to the left atrial appendage from inappropriate placement of a stabilizer.
Posterior Vessels: Obtuse Marginal Branches
Other lower obtuse marginal branches can be best accessed with the heart in the vertical position and slightly
rotated to the right. The stabilizer is attached on either the crossbar or the right side of the retractor and placed
with the tips toward the base of the heart (Fig. 9.75).
Exposure of the circumflex coronary artery and some of the obtuse marginal branches may be difficult at
times, particularly when the left ventricle is dilated. Opening of the right pleura will provide better access.
Obstruction of Venous Return
The heart should not be rotated excessively in an attempt to provide better target exposure because this may
cause obstruction of venous return.
FIG. 9.75 Exposure and stabilization of obtuse marginal branches.
FIG. 9.76 Exposure and stabilization of the posterior vessels.
Posterior Vessels
Posterior Descending Artery
Exposure of this vessel is usually very well tolerated without hemodynamic instability. The heart is displaced
vertically without any rotation. The stabilizer is attached to the left side of the retractor and placed toward the
base of the heart (Fig. 9.76).
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FIG. 9.77 Exposure and stabilization of the distal right coronary artery.
Distal Right Coronary Artery
Adequate exposure can usually be accomplished without lifting the heart out of the chest. The stabilizer is
attached to the right side of the retractor with the tip directed downward along the course of the artery (Fig.
9.77).
It is preferable to graft the right posterior descending artery rather than the distal main right coronary artery.
Occlusion of posterior descending artery rarely causes hemodynamic problems. If the right coronary artery itself
must be grafted, a shunt may be required to avoid ischemia and hemodynamic instability.
Right Ventricular Distention and Bradycardia
It is not uncommon for bradycardia and right ventricular distension to occur with proximal occlusion of the right
coronary artery. Therefore, alligator clips should be applied to the epicardium and attached to a pacemaker
before coronary occlusion. Alternatively, an intraluminal shunt can be used.
Conduct of the Surgery
As in on-pump coronary artery surgery, the heart is exposed through a median sternotomy and all conduits are
harvested in the usual manner. The operative technique for grafting vessels during an off-pump case is similar to
that used with on-pump surgery. After an arteriotomy is made, an intravascular shunt is inserted and the proximal
silastic tape is released. In vessels too small for shunting, the silastic tape is placed under traction to control
bleeding.
FIG. 9.78 Avoid the use of distal occlusion.
Injury to the Artery Distal to the Anastomosis
Distal vessel occlusion should be avoided because it may cause intimal injury and subsequent stenosis (Fig.
9.78).
A bloodless field is obtained with a CO2 mist blower.
Lifting an Intimal Plaque
Vigorous spraying with the CO2 blower can either lift an intimal plaque or separate the intimal layer to cause a
localized dissection (Fig. 9.79). Use of the CO2 blower should be limited to the time that the needle passes
through the target vessel and only when sufficient blood is present to obscure the field. Focus should be on the
site of each needle passage with attention to the back wall and edges. A completely bloodless field is not
necessary.
After each distal anastomosis, the graft is deaired by gently flushing with warm blood (or removing the
internal thoracic artery occluder) before tightening and securely tying the suture.
With a relatively disease-free aorta, proximal vein graft anastomoses are performed using a partial occlusion
clamp. The systemic arterial blood pressure is lowered to a systolic level of approximately 100 mm Hg before the
clamp is applied. The clamp should be tightened just enough for hemostasis but securely enough to not slip off.
Aortic Dissection
Applying the clamp too tightly or during hypertension can cause aortic dissection, especially in the elderly with a
fragile aorta.
In patients with atherosclerotic or calcific aortic disease in whom the side-biting clamp cannot be placed
safely, alternative sites for proximal anastomoses such as the innominate artery may be considered. Another
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strategy in this clinical situation is the use of the Heartstring System if a soft spot on the ascending aorta can be
identified. The Heartstring III Proximal Seal System (Maquet Cardiovascular, Wayne, NJ) allows creation of a
proximal handsewn anastomosis without clamping the ascending aorta (Fig. 9.80).
Transmyocardial Revascularization
Transmyocardial revascularization (TMR) is an adjunct to the surgical management of coronary artery disease.
Carbon dioxide laser, holmium:YAG laser, and xenon chloride eximer laser have all been used to create channels
into the left ventricular cavity. TMR with laser is used in patients with stable angina despite optimal medical
therapy and with a region of myocardium that cannot be directly vascularized. In this patient population, TMR has
been shown to improve anginal symptoms and is associated with improved left ventricula perfusion. Although the
mechanism of the beneficial effects of TMR is unknown, it is believed that local intramyocardial delivery of blood
and/or angiogenesis play a role in this process.
Patients with ejection fractions less than 30% or acute ischemia are generally not candidates for TMR.
Although TMR is usually applied only to areas of myocardium that cannot be directly revascularized,
patients with diffusely diseased coronary arteries may benefit from combined treatment.
Technique
TMR can be performed as an isolated procedure through an anterior thoracotomy or thorascopic approach.
However, it is typically performed after bypass grafting is completed, while the patient is still on cardiopulmonary
bypass. The viable ischemic area is exposed. The laser is fired to create between 15 and 20 channels 1 cm
apart, covering the ischemic but not directly the revascularized area. Bubbles are seen by transesophageal
echocardiography when the laser beam reaches the ventricular cavity, confirming a completed channel. The
carbon dioxide laser should be synchronized to the patient's electrocardiogram so that the pulse is delivered on
the R wave, to minimize the likelihood of arrhythmia. After cardiopulmonary bypass is discontinued and protamine
is administered, most channels readily seal at the epicardial surface with gentle digital pressure. Occasionally, a
figure-of-eight 6-0 Prolene suture may be required for hemostasis.
Many surgeons combine laser with therapeutic angiogenesis.
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FIG. 9.79 Separation of intimal plaque from vigorous spraying with a CO2 blower.
FIG. 9.80 Heartstring II proximal seal system for proximal aortic anastomosis.
CONSIDERATIONS IN REOPERATIVE CORONARY ARTERY BYPASS
SURGERY
The operative strategy for performing redo coronary surgery is similar to the primary procedure. Some important
points need to be considered. General precautions for repeat sternotomy need to be followed (see Chapter 1). If
a patent in situ right internal thoracic graft is present and crossing the midline, or if a redundant left internal
thoracic pedicle lies directly beneath the sternum, great care must be exercised to prevent injury to these grafts.
If a patent in situ internal thoracic graft is present, the pedicle must be identified and mobilized if the redo
procedure is to be done on cardiopulmonary bypass with cardioplegic arrest of the heart. The pedicle must be
occluded with an atraumatic bulldog clamp during the crossclamp interval. The safest technique for identifying
the left internal thoracic pedicle is to begin the dissection from the diaphragm and proceed superiorly. The
anastomotic site is therefore encountered first, and the pedicle can then be gently encircled for later clamping.
If a thoracic pedicle is injured, it may be primarily repaired using surrounding adventitial tissue. If repair and
reestablishment of flow is not feasible, urgent initiation of cardiopulmonary bypass is advisable. Replacement of
injured graft is then undertaken. Alternatively, the injured graft may be cannulated with an olive-tipped catheter
and perfused with a line connected to an aortic or femoral artery catheter.
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There is always concern regarding having adequate conduits for a coronary reoperation. It is important to
evaluate the patient preoperatively for the availability and quality of remaining conduits. This may entail Doppler
studies to identify residual greater saphenous vein segments or usable lesser saphenous vein. At the time of
angiography, it is useful to inject any internal thoracic vessel not previously used to demonstrate its patency.
Occasionally, the internal thoracic vessels are injured or occluded during chest closure, and therefore would not
be available as conduits for the reoperation.
If conduits are limited, sequential anastomoses should be considered. This strategy also reduces the
number of proximal anastomotic sites on an already overcrowded and scarred ascending aorta.
The ascending aorta is often quite thickened and diseased in patients undergoing redo coronary artery
procedures. Therefore, it is generally safer to perform all distal and proximal anastomoses under a single aortic
cross-clamp period. The hood of the old vein graft is usually free of disease and provides a good location for a
proximal anastomosis.
The patent arterial grafts often provide satisfactory sites for the proximal anastomosis of short arterial grafts.
This can be performed without clamping the aorta.
Patent but diseased saphenous vein grafts should not be manipulated to prevent embolization of debris into the
distal coronary artery bed. Some controversy exists as to whether antegrade cardioplegia should be
administered down diseased vein grafts. Some surgeons divide all old, patent vein grafts once on
cardiopulmonary bypass and flush debris out of them with retrograde cardioplegia. The two ends are oversewn
after the distal anastomosis of the new graft is completed.
Inadequate Flow through Internal Thoracic Artery
An internal thoracic artery may not provide sufficient flow to a previously grafted coronary artery with a diseased
but patent vein graft. This is especially true if the surgeon elects to divide and oversew the old graft to prevent
embolization of debris. In this case, another vein graft is preferred.
How to deal with a patent or stenotic vein graft when an internal thoracic artery is to be used is somewhat
controversial. In our practice, we tend to leave the old vein graft intact and anastomose the internal thoracic
artery to the coronary just distal to the old graft. If the vein graft has been injured, then it is replaced with another
vein graft. If there is not an anastomotic stenosis, a 1-mm rim of the old vein graft is left at the distal anastomotic
site and the new vein graft is sewn to it. Alternatively, another vein graft and the internal thoracic artery may be
connected to this coronary artery, with the risk of competitive flow causing a string sign of the arterial conduit.
Often the coronary artery disease has progressed and given rise to new stenotic lesions distal to the
occluded graft. In such situations, the occluded graft must be replaced to provide perfusion to the proximal
coronary bed. In addition, a second graft is required to provide flow beyond the new stenotic lesion.
Injury to the Lung
The internal thoracic pedicle often lies between the lung and the heart. If dissection is carried out superiorly to
locate the pedicle, the lung tissue is frequently injured in multiple locations. This results in air leaks that may
persist for several days postoperatively.
If the internal thoracic pedicle cannot be safely found, the surgery may be performed as an off-pump
procedure or on cardiopulmonary bypass with deep hypothermic arrest.
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