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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. 5.49 Excision of the coronary artery ostia and excess noncoronary prosthetic wall.
FIG. 5.50 Suspension of the prosthetic commissures above the native aortic commissures.
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The scalloped portion of the device is sutured to the native aortic wall parallel with the native annulus. This
technique ensures a precise, waterproof suture line well away from the coronary ostia. The suture line starts at
the nadir beneath each coronary artery ostium and progresses upward to the top of the commissure on each
side (Fig. 5.52). The sutures are tied together at the top of the commissure between the left and right coronary
sinus outside the aorta. If commissural sutures have been used, they are now tied outside the aorta and may be
buttressed with a pledget.
FIG. 5.51 Distal suture line beneath the left coronary ostium with frequent assessment of commissure placement.
FIG. 5.52 Completed distal suture line beneath both coronary artery ostia.
Low-Lying Right Coronary Ostium
The right coronary sinus portion of the stentless porcine bioprosthesis has a muscle bar that is covered by an
extension of the Dacron skirt. This should not be cut. Therefore, the distal suture line along the right coronary
sinus must be performed several millimeters above the annulus so as not to buckle the muscle bar of the
prosthetic valve. If the patient's right coronary ostium is particularly low, the prosthetic valve should be rotated
120 degrees to place the muscle bar in the patient's noncoronary sinus. All three prosthetic sinuses are then
scalloped.
Distortion of Commissures with Closure of an Oblique Aortotomy
If closure of the native aortic wall over the retained noncoronary sinus portion of the prosthetic valve brings the
commissure between the left and noncoronary sinus and the commissure between the right and noncoronary
sinus too close together (Fig. 5.53), the noncoronary sinus of the prosthesis is used to enlarge the aortic root.
The aortotomy incision is extended into the midportion of the native noncoronary sinus. The edge of the V-
shaped incision is sutured to the retained coronary sinus of the bioprosthesis using a 4-0 Prolene suture (Fig.
5.54A). The distal aspect of the aortotomy is then sewn to the top of the retained sinus and continued onto the
proximal portion of the aortotomy incision (Fig. 5.54B). To correct for the resulting length discrepancy, a
perpendicular cut equal to one-half the width of the retained sinus is made in the distal aspect of the aortotomy
incision (Fig. 5.54C). Alternatively, a small, triangle-shaped piece of Hemashield Dacron patch can be used to
complete the aortic closure (Fig. 5.54D).
Bulging of the Retained Noncoronary Sinus Wall into the Lumen of the Aorta
If closure of the aortotomy results in protrusion of the prosthetic noncoronary sinus into the aorta and the
commissures are appropriately located, the noncoronary sinus should be scalloped and reattached to the aortic
wall as was done for the right and left coronary sinuses. Alternatively, the bulge, if not excessive, can be
approximated to the native aortic wall with separate sutures.
FIG. 5.53 Primary closure of an oblique aortotomy may distort commissural alignment.
Closure of a Transverse Aortotomy
When a transverse aortotomy has been made, the rightward aspect of the closure will often include the top of the
retained noncoronary sinus of the prosthetic valve. Taking two to three bites behind (posterior to) the rightward
extent of the aortic opening results in a nearly circumferential aortic suture line. This reinforces the sinotubular
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junction, which may help prevent later dilation and resultant valvular incompetence.
The noncoronary sinus segment of the bioprosthesis is secured to the native aortic wall with another 4-0 Prolene
suture. The intervening dead space can be obliterated with one or two 4-0 Prolene sutures placed inside to
outside and tied over a felt pledget. The aortotomy is then closed with continuous 4-0 Prolene sutures. If an
oblique aortotomy has been used, the proximal portion of the opening must be closed before suturing the
retained prosthetic noncoronary sinus to the native aortic wall.
AORTIC VALVE REPAIR
Aortic valve repair has been used successfully in congenital patients with subaortic membranes and/or
ventricular septal defects with cusp prolapse (Fig. 5.55). Only select adult patients are candidates for aortic valve
repair. Stenotic
aortic valves are not amenable to repair. Aortic valve repair may be possible in patients with aortic insufficiency
secondary to dilation of one or more components of the aortic root or cusp prolapse only if the cusps are not
thickened, have good mobility, and are not calcified
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FIG. 5.54 A: Using a portion of the noncoronary sinus of a stentless valve to enlarge an aortotomy in such a way
as to correctly align commissures. B and C: Completing aortic closure with native aortic wall. D: Aortic closure
completed with a patch of Hemashield.
Ultrasonographic Decalcification
Ultrasonographic decalcification of stenotic aortic valves has been abandoned because of the resultant scarring
and retraction of the leaflets.
Prolapse of one cusp in an adult patient with a trileaflet aortic valve is rare. Repair can be achieved with the
technique described in Chapter 21.
Techniques
A successful and durable aortic valve repair requires a thorough understanding of the mechanism of the aortic
valve dysfunction. Transesophageal echocardiography demonstrates the quality, height, and coaptation level of
the leaflets, as well as the respective diameters of the annulus, sinuses, sinotubular junction, and ascending
aorta (see Surgical Anatomy of the Aortic Valve discussed earlier). Patients with a dilated sinotubular junction or
aneurysm of the aortic root with aortic valve insufficiency and normal cusps are candidates for a valve sparing
procedure (see Chapter 8).
Perforation of a cusp due to healed endocarditis or iatrogenic injury may be patched with a piece of
glutaraldehyde-treated autologous pericardium (Fig. 5.56). This is accomplished by attaching the patch, cut
slightly larger than the defect, to the aortic aspect of the leaflet with a running 5-0 or 6-0 Prolene suture.
FIG. 5.55 Aortic comissuroplasty.
The most common indication for aortic valve repair in adults is bicuspid aortic valve with prolapse of one of the
cusps. Generally, it is the anterior cusp, which has a raphe where the commissure between the right and left
cusps normally would be, which elongates and prolapses. If the posterior cusp is normal, the anterior cusp can
be repaired. Stay sutures are placed through the aortic wall just above the two commissures. By pulling up on
these sutures, the length of the free edges of the leaflets is noted. The raphe of the anterior leaflet is excised
and reapproximated with interrupted sutures of 6-0 Prolene, thereby shortening its free edge to match the
posterior leaflet (Fig. 5.57). Because most of these patients have associated annuloaortic ectasia, the two
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subcommissural triangles should be narrowed. This is accomplished by placing horizontal mattress sutures of 4-
0 Prolene with felt pledgets outside the aorta. The suture passes from outside to inside the aortic root 2 to 3 mm
below each commissure, through the annulus of both cusps, then through the aortic wall again 2 to 3 mm below
the commissure.
Resection of Raphe
Only a small triangle of leaflet should be resected, avoiding the belly of the cusp, to ensure adequate coaptation
with the posterior leaflet. Alternatively, if the median raphe is pliable, it can be plicated with a running Prolene
suture.
FIG. 5.56 Patch repair of cusp perforation.
FIG. 5.57 Repair of bicuspid aortic valve: resection of raphe and shortening of free edge of leaflet.
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Patients with bicuspid valves and aortic roots measuring greater than 45 mm in diameter should undergo
aortic root replacement.
The shortened elongated leaflet edge may be reinforced with a double running suture of 6-0 Gore-Tex tied
on the outside of the aorta, taking care to not shorten the free margin too much.
Aortic Stenosis
Overplication of the commissures can lead to functional aortic stenosis. The surgeon may use a valve sizer to
ensure the adequacy of the aortic opening.
PROBLEMATIC CASES
Patients with unclampable aortas, small aortic roots, and aortic valve endocarditis present special challenges for
the cardiac surgeon. Alternate surgical approaches and techniques are often required.
Management of Unclampable Aorta
Because people are living longer, cardiac surgeons are encountering an increasing number of patients with
atherosclerotic disease of the ascending aorta who require surgical intervention for valvular or coronary disease.
The degree of involvement of the aorta ranges from a few isolated atherosclerotic plaques to total calcification of
the aorta, often referred to as porcelain aorta. Cannulation and clamping of such diseased aortas can be
hazardous, resulting in stroke or even death. The presence of atherosclerosis and/or calcification of the aorta
may be detected on preoperative chest x-ray or computed tomography scan. Intraoperative transesophageal
echocardiography may demonstrate atherosclerotic changes in the ascending and descending aorta. However,
epiaortic ultrasonographic scanning is the most specific diagnostic tool available, allowing the surgeon to map
the aorta and locate possible cannulation and clamping sites. The severity and extent of atherosclerosis affecting
the aorta will guide the surgeon as to the optimum approach. If both proximal and distal segments of the aorta
are heavily calcified, the entire length of the ascending aorta may be replaced with a tube graft (see Chapter 8).
Often, the aortic root can be retained and endarterectomized to allow aortic valve replacement to be performed
and the proximal aorta to be attached to the tube graft. More often, the disease affects the aorta in a patchy
manner. These patients can be managed less aggressively.
Technique
The aorta is cannulated if a safe area is identified by epiaortic ultrasonographic scanning. The axillary artery is
usually soft and the preferred site for arterial cannulation (see Chapter 2 for axillary artery cannulation).
Alternatively, femoral artery may be used for arterial cannulation (see Chapter 2). A single dual-staged atriocaval
cannula is placed through the right atrial appendage. Cardiopulmonary bypass is initiated, and the patient is
slowly cooled to 18°C to 24°C. The heart is decompressed with a vent through the right superior pulmonary vein
or the pulmonary artery.
When cooling has been completed, the patient is placed in Trendelenberg position and the pump is stopped.
The aorta is opened and transected. A hemashield tube graft is anastamosed to the distal aorta. This suture line
may need
to be reinforced with a strip of felt. Topical hemostatic supplies are used to ensure hemostasis. Decalcification of
distal nature aortic wall may be necessary to facilitate placement of sutures. Once this suture line is completed,
the tube graft filled with blood and with the patient in Trendelenberg position, the graft is clamped and antigrade
pump flow (via axillary artery cannulae) is begun. The suture line is repaired to ensure optimal hemostaisis.
During rewarming, the aortic valve is replaced using the previously described techniques and the proximal tube
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graft anastomosis to the native aorta is completed.,
Rarely aortic valve replacement is performed under hypothermic circulatory arrest to avoid clamping the aorta.
Hypothermic Circulatory Arrest
It is important to bear in mind that hypothermic circulatory arrest itself may result in neurologic complications,
especially with longer periods of arrest. Therefore, it is usually preferable to limit the arrest time to that required
to perform the distal anastomosis of a replacement tube graft or to complete an endarterectomy.
A safe option in some elderly patients with unclampable aortas or with internal thoracic arterial conduits located
under the sternum is the apico-descending aortic conduit.
Apicoaortic Valve Conduit
Apicoaortic valve conduit is not a new concept. The procedure has been performed in select groups of adult and
pediatric patients for many decades. A conduit containing a bioprosthetic valve is interposed between the apex of
the left ventricle and the descending thoracic aorta either with or without cardiopulmonary support.
Technique
The use of a double lumen endotracheal tube allows the left lung to be deflated, and facilitates exposure. A left
thoracotomy through the fifth or sixth intercostal space provides good access to both the descending aorta and
the left ventricle. The inferior pulmonary ligament is ligated and divided to free up the left lung and improve
access to the descending aorta. The parietal pleura overlying the lower descending thoracic aorta is incised and
retracted. A disease-free segment of the aorta is identified and excluded with a large Satinsky partial occluding
clamp. The distal end of the valve conduit is sewn to the aortic opening with 3-0 or 4-0 Prolene. The partial
occluding clamp is removed after clamping the conduit.
The patient must be heparinized before clamping the aorta.
Calcification of Descending Aorta
If this procedure is contemplated, the presence of severe atherosclerotic disease and/or calcification of the
descending aorta should be ruled out. This is usually done with a computed tomography scan preoperatively.
The pericardium is opened anterior and parallel to the left phrenic nerve and suspended with traction sutures. A
segment of the anterior wall of the left ventricle near the apex is selected for placement of the valve conduit.
Multiple U-shaped 2-0 Ticron sutures, buttressed with soft Teflon felt, are passed deeply through the thickened
muscle and then through the sewing collar of the connector. Through a stab wound, a muscle coring device is
introduced to create the outflow tract through which the rigid angled apical connector is quickly placed into the
left ventricle. All sutures are securely tied, and the suture line may be reinforced with an additional continuous
suture of 3-0 Prolene.
Injury to Left Anterior Descending Artery
The conduit outflow tract should be well away from the coronary artery and the thinned portion of the left
ventricular apex.
Clot in Left Ventricle
Detailed echocardiography should be done to detect the presence of blood clot in the left ventricular apex and
along the septum. Dislodgement of clot will result in systemic embolization and a potential cerebral vascular
accident.
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Location of Papillary Muscle
Intraoperative transesophageal echocardiography can locate the papillary muscles and ensure that the conduit is
placed away from their insertion sites.
The grafts of the valve conduit and connector are appropriately trimmed and anastomosed with a continuous
suture of 3-0 Prolene. Following careful deairing, clamps on the grafts are removed.
Biological glue and/or hemostatic products applied on all suture lines help to reduce bleeding.
The procedure may be more safely accomplished with femoral-femoral bypass support (see Chapter 2). The
heart can be lifted and fibrillation induced to facilitate the introduction of the muscle coring device and rigid
connector into the left ventricle.
Although stented porcine valve conduits are most commonly used in these patients, the Freestyle aortic root
bioprosthesis (Medtronic, Minneapolis, MN) has been used as an intervening device between the apical
prosthesis and tube graft from the descending aorta.
Management of the Small Aortic Root
It is clear that no prosthetic valve is hemodynamically equal to the patient's own heart valve. Therefore,
whenever valve replacement is done, the patient receives a less
optimal valve substitute. Fibrosis, calcification, or simply a very small aortic root can limit the maximal orifice of
the aortic annulus. Therefore, a prosthesis that fits in the annulus comfortably may be unacceptable
hemodynamically. This is particularly significant in larger patients with small aortic roots. Patient-prosthesis
mismatch occurs when the effective orifice area of the implanted prosthetic valve is too small in relation to the
patient's body size. This mismatch results in a higher transvalvular gradient and less regression of left ventricular
hypertrophy, which may lead to increased cardiac morbidity and mortality. Many techniques have been
developed to overcome this mismatch between the patient and prosthesis.
Tilted Prosthesis Technique
Depending on the type of prosthesis, by tilting the plane of implantation by 5 to 10 degrees, it is often possible to
implant a larger valve into the aortic root. Simple interrupted sutures are used to attach the prosthesis to the left
and right coronary annuli. Starting from either end of the noncoronary annulus and arching upward to a central
point 5 to 8 mm above its nadir, sutures, double-armed with needles (2-0 Ticron), are passed first through the
sewing ring in a horizontal manner downward from above and then through the aortic wall. The needles are
finally passed through small pledgets or strips of Teflon felt outside the aorta (Fig. 5.58). The prosthesis is then
lowered in this tilted position, and the sutures are tied. The sutures on the noncoronary side are tied outside the
aorta over the Teflon felt pledgets.
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FIG. 5.58 Technique of securing a disc prosthesis (Medtronic-Hall) in the tilted position.
Location of the Aortotomy
The right margin of the aortotomy should be at a higher level than usual, 1.5 to 2 cm above the noncoronary
annulus, to facilitate sewing the prosthesis in a tilted manner and, at the same time, to allow satisfactory closure
of the aortotomy.
Buttressing of the Sutures
All sutures anchoring the prosthesis onto the aortic wall above the annulus must be buttressed with Teflon
pledgets or a strip of Teflon felt or pericardium. The aortic wall requires reinforcement to be strong enough to
hold the prosthetic valve in position.
Opening Angles of Disc Prostheses
The opening angles of discs differ by manufacturer. The Medtronic-Hall disc opens maximally to a 75-degree
angle. This is an important point of concern. The combined tilting angle and disc opening angle should not be
more than 80 to 85 degrees. Otherwise, there is the risk that when the disc opens, it may not close!
The concept of the tilting technique allows the implantation of a larger prosthesis in the supraannular position
along the noncoronary annulus.
Use of Bileaflet Prostheses
Bileaflet prostheses have excellent hemodynamics and are preferred by many surgeons for use in patients with
small aortic roots. When used in the tilted position, the
leaflets may impact the aortic wall and not open or close completely (Fig. 5-59A). Free mobility of the leaflets
must be ensured by proper orientation of the prosthesis (Fig. 5.59B).
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