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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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If severe tricuspid insufficiency persists after all reparative attempts, the addition of an edge-to-edge repair may
be considered. This technique may be particularly useful in patients with significant pulmonary hypertension.
Technique
The midpoints of the facing edges of the anterior, posterior, and septal leaflets, just at the point of insertion of
primary chords, are approximated with multiple U stitches of 4-0 Prolene buttressed with autologous pericardial
pledgets. A tri-orifice tricuspid valve is therefore created. The valve is tested with saline for residual leakage or
leaflet distorsion. Direct edge-to-edge suturing of adjacent leaflets at the commissures may be added to deal with
minor residual insufficiency. The orifices are all measured with Hegar dilators to assure a satisfactory total valve
orifice area.
Pacemaker Lead-Induced Tricuspid Regurgitation
The endocardial ventricular lead of a pacemaker may distort and eventually become incorporated into one of the
tricuspid leaflets, causing valvular insufficiency. It may be possible to resect the involved portion of the leaflet
and reconstruct the valve. The lead is removed and an epicardial ventricular lead is placed. However, if the
leaflet involvement is extensive, valve replacement may be required. In this case, the pacemaker lead can be
positioned between the sewing ring of the valve and the patient's annulus.
TRICUSPID VALVE REPLACEMENT
Because it is usually possible to repair the tricuspid valve, its replacement is rarely necessary. Nevertheless,
when the severity of the valvular distortion prevents a satisfactory reconstructive procedure, valve replacement
becomes mandatory. This is occasionally the case with rheumatic involvement of the tricuspid valve. Valve
replacement is indicated when patients with carcinoid- or radiation-induced tricuspid disease require surgery. If
possible, the subvalvular apparatus is retained and the leaflet tissues are incorporated in suturing the prosthesis
to the annulus (see discussion on mitral valve replacement with retaining the subvalvular apparatus in Chapter
6). Often, however, when tricuspid valve replacement becomes necessary, the subvalvular structures and
leaflets are diseased to a degree that precludes their use. In these cases, resection of the tricuspid valve is
started by incising the anterior and posterior leaflets and dividing the chordal attachments deep in the right
ventricle. The mobilized valve may now be inverted up into the right atrium, and with visual control from both the
atrial and ventricular sides, the septal leaflet is dissected. A broad zone of the attached margin of the septal
leaflet and its chordal attachments is left in place, if possible. Preferably, the septal leaflet or all the leaflets are
left intact and used to anchor the appropriate prosthesis. The normal tubular and triangular configuration of the
right ventricle is often lost in patients with chronic tricuspid valve disease. The dilated right ventricle can easily
accommodate the struts of a tissue prosthesis.
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FIG. 7.9 Technique for tricuspid valve replacement.
Size 3-0 Teflon pledgeted sutures are passed through the annulus, except in the region of the septal leaflet. In
this area, sutures are placed only through the leaflet tissue and its attached structures to avoid producing heart
block. The sutures are then passed through the sewing ring of the prosthesis (Fig. 7.9). The prosthesis is
slipped down into its bed, and the sutures are tied and cut. Care is taken to avoid injury to the right ventricular
endocardium while introducing the prosthesis into the decompressed ventricle. As in mitral valve replacement,
size selection is based not only on the diameter of the atrioventricular ring but also on the size of the ventricular
cavity. No problems have been encountered reducing the annulus by placing sutures close together on the
sewing ring of the prosthesis. Serious injury to the interventricular septum may occur, however, if too large a
prosthesis is placed into the right ventricle.
Disc Valve Dysfunction Caused by Leaflet Tissue
When the leaflets with their subvalvular attachments are left intact to preserve right ventricular function,
bileaflet mechanical and bioprostheses are the valves of choice.
Injury to the Atrioventricular Node and Conduction Tissue
The anchoring of sutures for the prosthesis must be well away from the conduction tissue to avoid
producing heart block.
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Septal Injury
A bioprosthesis protruding into a small right ventricular cavity can produce septal injury. Under these
circumstances, an appropriately sized bileaflet mechanical prosthesis or a low-profile bioprosthesis should be
used.
Valve Choice in Carcinoid
With the improved medical management for carcinoid disease available, the formation of carcinoid plaques on
bioprosthetic valves can be prevented. The use of bioprosthetic valves avoids the need for anticoagulation in
these patients who have hepatic dysfunction and coagulopathy.
Consideration should be given to placing permanent epicardial ventricular pacing leads in patients
undergoing tricuspid valve replacement. These leads can be buried in a pocket anterior to the posterior rectus
sheath in the left upper quadrant for later permanent pacemaker implantation if required.
Tricuspid Valve Endocarditis
When tricuspid valve endocarditis does not respond to antibiotic or antifungal therapy, valve excision and
replacement may be required. However, attempts should be made to preserve the native valve. Vegetations are
usually found to be large and adherent to the leaflet tissue. Often, the infection destroys the leaflet and its
attachments. If the posterior leaflet is involved, the necrotic area with a good margin of healthy tissue is removed.
Bicuspidization is performed, excluding the posterior annulus, using 2-0 Ticron horizontal mattress sutures with
or without autologous pericardial pledgets (Fig. 7.10). When the septal or anterior leaflets are involved, the
affected portion is excised in a trapezoidal manner. A limited annuloplasty with horizontal mattress sutures of 2-0
Ticron is then performed, using pericardial pledgets depending on the tissue quality. The resected leaflet edges
are reapproximated with interrupted 6-0 or 7-0 Prolene sutures (Fig. 7.11). Because septal leaflet resection and
repair may result in complete heart block,
permanent epicardial pacemaker leads should be placed in these patients.
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FIG. 7.10 Technique for posterior leaflet resection and bicuspidization of the tricuspid valve.
FIG. 7.11 Technique for resection of a portion of tricuspid septal valve leaflet with subsequent annuloplasty and
leaflet reapproximation.
FIG. 7.12 Technique for patch closure of a ventricular septal defect combined with partial septal leaflet resection
and reconstruction.
In patients with ventricular septal defects associated with bacterial endocarditis affecting the tricuspid valve, the
septal defect is repaired through the tricuspid valve using a pericardial patch (Fig. 7.12). The edges of the
ventricular septal defect are first debrided, and the necrotic tissue and vegetations are removed meticulously. A
patch of autologous pericardium fixed in glutaraldehyde is then cut to match the size and shape of the resultant
defect. This is secured to the edges of the septal defect with running 4-0 Prolene or interrupted horizontal
mattress sutures of 4-0 Ticron. At the superior aspect of the ventricular septal defect located under the septal
leaflet of the tricuspid valve, the patch is secured to leaflet tissue adjacent to the annulus. If possible, sutures
should not be passed through the annulus in this area because the atrioventricular node is likely to be injured. If
this portion of the septal leaflet is involved with vegetation and requires excision, an attempt is made to preserve
a rim of leaflet tissue next to the annulus. After the ventricular septal defect patch is secured in place, the septal
annulus is reapproximated with horizontal mattress sutures of 2-0 Ticron with or without pericardial pledgets, and
the leaflet tissue is brought together with interrupted 6-0 Prolene sutures (Fig. 7.12). Results of tricuspid valve
repair in patients with endocarditis have been gratifying.
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8
Surgery of the Aorta
ACUTE AORTIC DISSECTION
Acute aortic dissection has a sudden onset and is a true surgical emergency. It is usually initiated by a
transverse tear in the intima or the intima and media. This disruptive injury gives rise to a hematoma within the
media. The pulsatile force of ejection of the left ventricle causes a longitudinal separation of the aortic wall,
mainly along and within the media. This dissection can progress both distally and proximally. Distal progression
beyond the aortic arch can continue along the course of the descending thoracic and abdominal aorta to a
variable extent and can involve its branches. Proximal extension of the dissecting hematoma may infiltrate the
aortic root, distorting the aortic valve leaflets or compressing the ostia of the coronary arteries. This can produce
aortic valve insufficiency and acute myocardial ischemia, respectively, both of which can cause death. In
addition, acute dissection can cause rupture of the aorta into the pericardium, causing tamponade. Therefore,
the symptomatology of aortic dissection can be highly variable depending on its effect on the aortic valve, aortic
wall, or aortic branches.
The development of acute aortic dissection is thought to involve many factors. Of great significance is medial
degeneration or cystic medial necrosis of the aortic wall. Marfan syndrome, an autosomal dominant disorder of
vascular collagen, is commonly associated with acute aortic dissection. However, annulo-aortic ectasia can
occur in patients without Marfan syndrome and result in acute aortic dissection. Clinically, most cases dissection
are associated with hypertension, a bicuspid aortic valve, and coarctation of the aorta.
The current classification (Stanford) distinguishes two types of aortic dissection based on the involvement of the
ascending aorta. Type A, or anterior, dissection commonly starts in the ascending aorta, usually 1 to 2 cm above
the sinotubular junction, and may progress along the course of the aorta for a variable distance. Type B, or
posterior, dissection typically starts in the descending aorta distal to the origin of the subclavian artery. The
dissection can progress distally to a variable distance; less commonly, it may extend proximally, thereby resulting
in a retrograde type A dissection.
The DeBakey classification is based on the anatomic location of the dissection. Therefore, Stanford type A
corresponds to DeBakey types I and II, whereas Stanford type B includes DeBakey types IIIA and IIIB (Fig. 8.1).
From the practical point of view, the Stanford classification is simple and provides guidance as to the initial
method of management (surgical versus medical) as well as surgical approaches (median sternotomy versus left
postero-lateral thoracotomy).
The immediate management of all acute aortic dissections is to reduce and maintain the patient's systolic blood
pressure at a level that still ensures satisfactory cerebral and renal perfusion. All patients suspected of acute
aortic dissection should immediately undergo computed tomography with contrast. Acute type A aortic dissection
is a surgical emergency because conservative therapy is not effective in most instances. On the other hand,
patients with acute type B dissection are initially treated medically with antihypertensive therapy. There are
occasions when the diagnosis of acute type A aortic dissection cannot be made with computed tomography. In
these cases, transesophageal echocardiography should be performed to rule out involvement of the ascending
aorta in the dissection process. This can be accomplished in the intensive care unit, the emergency department,
or the operating room.
AORTIC ANEURYSMS
Aortic aneurysms are defined as areas of localized aortic dilation and can involve any segment of the aorta. The
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prevalence of thoracic aortic aneurysms has tripled in the last 20 years. This increase in prevalence may be
partly due to the increasingly aging population, better imaging, or a true increase in the incidence. Thoracic
aortic aneurysms are now estimated to affect 10 of every 100,000 elderly adults. The ascending aorta is most
commonly affected (45%), followed by the descending aorta (35%). The aortic arch (10%) is involved either as
an isolated lesion or as an extension of the ascending or, less commonly, descending aortic aneurysms.
Progressive enlargement of the aneurysm is an indication for resection and replacement with a
tube graft because it will eventually rupture, culminating in the death of the patient.
FIG. 8.1 Classification of aortic dissection.
The techniques for excision and graft replacement for aneurysms of the ascending and descending thoracic
aorta are similar to those described for surgical management of types A and B aortic dissections. In addition,
patients with a porcelain or severely atherosclerotic aorta requiring an aortic valve procedure may need
replacement of the ascending aorta.
REPLACEMENT OF THE ASCENDING AORTA
The ascending aorta is approached via a median sternotomy. Both groins should be in the operative field and
the arterial return is accomplished by cannulating either femoral or external iliac arteries. In patients with
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ascending aneurysms, direct aortic cannulation in the proximal arch may be feasible. In many centers, the right
axillary artery is preferentially used.
The right femoral artery is less commonly involved in aortic dissection and therefore should be the second
site of choice after the right axillary artery.
Retrograde Perfusion through False Lumen
In patients with aortic dissection, the disease often extends distally, sometimes down to the femoral vessels;
therefore, care must be exercised not to cannulate and perfuse through the false lumen of the femoral artery in a
retrograde manner.
Occlusive Disease of the External Iliac and Femoral Vessels
In elderly patients with severe atherosclerosis, the femoral and iliac arteries are markedly diseased and
cannulation may be hazardous. A number of cannulas are available, which can be introduced into these vessels
percutaneously or under direct vision using the modified Seldinger technique (Fig. 8.2). The flow through a 20-
French cannula is
adequate for all but very large patients. Alternatively, the axillary artery may be used.
FIG. 8.2 Multiple side hole femoral cannula that can be introduced over a guidewire.
A dual-stage atriocaval cannula is usually used for venous drainage.
If the ascending aorta is large and obscures the right atrium for venous cannulation, femoral vein
cannulation is performed.
Repeat Sternotomy
If the procedure is a reoperation, it is advisable to have arterial and venous cannulation, and occasionally full
bypass, accomplished through the femoral artery and vein before opening the sternum (see Chapter 2).
Hemodynamic Instability
It is prudent to initiate cardiopulmonary bypass promptly by means of the femoral vessels before the
administration of general anesthesia in patients with unstable hemodynamics to prevent circulatory collapse.
This is especially important if pericardial tamponade is apparent or suspected.
Femoral vein cannulation can be achieved by introducing a long cannula with multiple side holes for excellent
venous return. The important characteristic of this device is that it comes with a guidewire and contains a
tapered, dilated sheath inside the cannula. The guidewire allows easy, comfortable, and safe passage of the
cannula over the pelvic brim. The cannula has multiple side holes and may be advanced into the right atrium,
providing superior drainage.
Iliac Vein Injury
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Venous cannulas that lack guidewires often hang up at the pelvic rim, resulting in inadequate venous return. If an
attempt is made to push the cannula further into the inferior vena cava, perforation of the iliac vein with
catastrophic consequences may ensue. It is usually easier to pass the cannula through the right femoral vein
because of its straighter course compared to the left side.
After completion of a median sternotomy, an additional venous cannula is placed in the right atrium if required. A
left ventricular vent through the right superior pulmonary vein (see Chapter 4) decompresses the heart and
expedites the procedure. Venting is especially important if aortic valve insufficiency is present.
FIG. 8.3 Direct cannulation of the superior vena cava for retrograde cerebral perfusion.
Retrograde Cerebral Perfusion
In situations when deep circulatory arrest is contemplated, the patient is generally cooled down to bladder
temperature of 18°C to 24°C. Moderate hypothermia (bladder temperature of 26°C to 28°C) is safe if the
anticipated period of circulatory arrest is less than 15 to 20 minutes. Ice is packed around the patient's head. A
tape is passed around the superior vena cava (see Chapter 2). A purse-string suture of 4-0 Prolene is applied to
the adventitia of the superior vena cava at its junction with the pericardium. The adventitial tissue within the
purse-string suture is cleaned off the superior vena cava, and an incision is made on the vein. The opening is
enlarged with the tip of a clamp or scissors, and a long right-angled cannula is introduced into the superior vena
cava and guided upward past the innominate vein (Fig. 8.3). This cannula is then connected to the side arm of
the cardioplegia delivery system or to the arterial line to perfuse cold blood into the superior vena cava whenever
circulatory arrest is initiated. The tape around the superior vena cava is snugged down on the cannula to prevent
perfusate from flowing back into the right atrium.
Exclusion of the Azygos Vein
Tape is snugged down on the superior vena cava above the azygos vein to prevent runoff of cold blood into the
azygos system (Fig. 8.3).
Some thought has to be given to extending the concept of retrograde cerebral perfusion with cold blood to
retrograde perfusion of the gastrointestinal tract and even the rest of the body. Consequently, at times, perfusion
of cold blood through the azygos vein may be advantageous.
The central venous pressure should not exceed 30 to 40 mm Hg as measured by the side arm of the Swan-Ganz
introducer in the internal jugular or subclavian vein. The perfusion flow should be approximately 400 to 800 mL
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per minute. It is not quite evident if the retrograde cerebral perfusion provides any nutritive support to the brain.
However, it is clear that it does provide a uniform cooling of the brain. Its most important benefit is prevention of
air or debris from flowing upward into the arch vessels, which would cause cerebral embolization. This can be
appreciated when atherosclerotic debris is seen floating in the very dark desaturated blood flowing out of the
arch vessels into the operative field.
At the end of circulatory arrest, retrograde cerebral perfusion is discontinued and the cannula is removed. The
purse-string suture on the superior vena cava is tied down. If retrograde cerebral perfusion has been
accomplished using an arm of the cardioplegia system, retrograde flow is continued for the first 1 to 2 minutes
after resuming cardiopulmonary bypass to help prevent air embolism to the arch vessels. It is also important to
ensure that the aortic root is filled with blood and devoid of air, before resuming cardiopulmonary bypass.
Selective Antegrade Cerebral Perfusion
A more recent alternative to retrograde cerebral perfusion is selective antegrade cerebral perfusion through the
right axillary artery. In conjunction with innominate artery occlusion, this method can provide effective cerebral
protection during circulatory arrest by allowing antegrade right carotid artery perfusion. Right axillary perfusion is
also used for systemic perfusion during cardiopulmonary bypass.
Before sternotomy, the right axillary artery is exposed through an 5 to 8 cm incision below and parallel to the
lateral two-thirds of the clavicle. The pectoralis major muscle is divided in the direction of its fibers. The
clavipectoral fascia is incised and the pectoralis minor muscle is retracted laterally. The axillary artery is located
superior to the axillary vein. Using sharp dissection, the proximal part of the axillary artery is isolated. After
administration of intravenous heparin, a small side-biting vascular clamp is applied to the artery. A longitudinal
arteriotomy incision of approximately 1 cm is made and an 8-mm Hemashield Dacron tube graft (Medox Medical,
Oakland, NJ) is sewn to the axillary artery in an end-to-side manner using a continuous 5-0 Prolene suture (Fig.
8.4). A 24-French arterial cannula is inserted into the graft, de-aired and secured. Perfusion through a graft is
safer than direct cannulation of the axillary artery and allows more accurate cerebral perfusion by monitoring the
right radial artery pressure. During hypothermic circulatory arrest, axillary arterial blood flow is adjusted to
maintain a right radial artery pressure of 50 to 60 mm Hg.
It is important to monitor radial or brachial artery pressures on the side of arterial cannulation in order to
prevent hyper-perfusion of the arm, which can lead to adverse outcomes, including limb loss.
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