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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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Measuring the Annulus
Because the sizers are exact replicas of the respective prostheses, the annulus must be measured with the sizer
that corresponds to the specific prosthesis. This is particularly relevant when using a prosthesis designed for
supraannular implantation.
It is important to consider the left ventricular outflow tract, aortic annulus, and sinotubular junction when sizing for
an appropriate prosthesis. This may not be of much significance in patients with pure aortic insufficiency.
However, in patients with severe aortic stenosis, there may be left ventricular outflow tract narrowing owing to
septal hypertrophy. The poststenotic dilation may sometimes obscure or distort the sinotubular junction.
Therefore, the diameter at each level may be different, making sizing for an appropriate prosthesis somewhat
demanding. It is prudent to attempt to size the left ventricular outflow tract, aortic annulus, and sinotubular
junction separately so that an appropriate type of prosthesis can be selected.
Calcified Aortic Root
When the aortic root is heavily calcified or there are calcific ridges in the wall of the aorta, it may be difficult to
introduce the sizer into the aortic root. The surgeon must then visually judge the size of the prosthesis.
Decalcification of the Aortic Root
Often there is calcification in the aortic root involving the sinuses and extending into the coronary artery ostia.
With experience, it is possible to decalcify the aortic root wall in specific locations to facilitate implantation of an
appropriately sized prosthesis. The technique consists of gently crushing segments of calcified intima with a
rongeur and then removing them from the aortic wall to facilitate the surgery. Implantation of a stentless aortic
bioprosthesis or a homograft using a modified subcoronary technique will reinforce a weakened segment of the
aortic wall.
Aortic Wall Tear
It is important not to pull away calcified segments from the wall of the aortic root in order to prevent a buttonhole
injury. The connection of the calcified segment with the intima must be sharply divided with scissors.
Technique for Suture Insertion
The prosthesis is sewn into position with interrupted sutures such as 2-0 Tevdek or Ticron, double-armed with
tapered needles. A deep bite of the annulus is taken. The suture ends are then either held taut by an assistant or
inserted in the correct order into a circular ring (Fig. 5.11). When all the annular sutures have been placed, they
are passed through the sewing ring of the prosthesis in an orderly manner, either singly or in a vertical mattress
technique. Alternatively, each suture can be passed through the annulus and the valve-sewing ring in one step
(Fig. 5.12). Sometimes certain segments of the annulus are not in full view. Pulling on a previously placed suture
will improve the exposure (Fig. 5.13). This suture can be held taut, either by the surgeon's hand or by placing it
in the circular ring.
Removal of Embedded Calcium Particles
The tip of the suture needle can be used to dislodge calcium particles deeply embedded in the myocardium (Fig.
5.14).
Suture Security
The sutures must be individually tested to make certain that they include a good, secure bite of the annulus; they
may tear through if they include only degenerative leaflet tissue or a narrow rim of the annulus. If the suture
appears to be insecure, it is either removed or converted to a figure-of-eight stitch (Fig. 5.15) and then passed
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through the sewing ring of the prosthesis in a horizontal mattress fashion.
Pledgeted Sutures
When the annulus is calcified or too friable to hold sutures securely, pledgeted sutures (2-0 Ethibond or Ticron)
are satisfactory alternatives. It is technically easier to insert the sutures in an everted manner, with the pledgets
lying above the annulus in the aorta (Fig. 5.16A). The alternative technique of placing sutures from below, which
allows the pledgets to remain subannular, provides a secure and satisfactory buttressing effect (Fig. 5.16C). This
technique is used for supraannular insertion of a prosthetic valve. If utilized with a disc valve, the surgeon must
ensure that no pledgets interfere with the normal movement of the disc. Also, if a suture breaks while being tied,
the loose pledget must be retrieved. The prosthesis often must be removed in
order to locate and remove the loose pledget from the left ventricle. Whether the pledgeted sutures are placed
from below or above the annulus, they are inserted into the sewing ring of the prothesis in a horizontal mattress
fashion (Fig. 5.17). The routine use of pledgets has markedly reduced the occurrence of paravalvular leaks.
FIG. 5.11 Ring for placement of sutures in sequence.
FIG. 5.12 A: Passing sutures directly from the annulus to the prosthetic sewing ring. B: Proper placement of
sutures in the sewing ring to place the knot away from the valve itself.
FIG. 5.13 Exposure for placement of sutures in the aortic annulus.
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FIG. 5.14 Using the tip of the needle to dislodge calcium embedded in the myocardium.
FIG. 5.15 Converting an insecure suture (A) to a figure-of-eight suture (B).
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FIG. 5.16 A: Inserting the sutures in an everted manner, with the pledgets lying above the annulus in the aorta.
B: Simple sutures. C: Inserting the sutures from below allows the pledgets to remain subannular. D: Figure-of-
eight sutures.
Heart Block
Deeply placed sutures near the noncoronary and right coronary annuli can injure the conduction tissues and give
rise to various forms of heart block (Fig. 5.18). When there is massive calcification extending onto the ventricular
septum or when the tissues are friable because of endocarditis or abscess formation, this complication may be
inevitable. Temporary ventricular wires are recommended for all patients undergoing aortic valve surgery. If the
patient is still in complete heart block at the completion of the procedure,
temporary atrial wires should be placed to allow for atrioventricular sequential pacing. A permanent pacemaker
may need to be implanted before the patient's discharge if atrioventricular conduction has not been
reestablished.
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FIG. 5.17 Horizontal mattress sutures, with pledgets below the annuli, placed in a horizontal mattress fashion in
the prosthetic ring.
FIG. 5.18 Injury to the conduction tissues caused by deeply placed sutures.
FIG. 5.19 Left main coronary artery punctured by a deep suture near the left coronary annulus.
Injury to the Left Coronary Artery
The precise site of suture placement in the aortic annulus is often obscured by pathologic changes,
calcifications, and deformities. Deep sutures placed near the left coronary annulus may puncture the left main
coronary artery as it passes behind the aortic root (Fig. 5.19). This is indeed a very grave error, and the surgeon
must always be sensitive to this possibility and take every precaution to avoid its occurrence. To prevent
myocardial ischemia and injury, the suture needs to be immediately removed. If the structural or functional
integrity of the left main coronary artery is in any way jeopardized, bypass grafting of all its major branches must
be performed.
Drying of the Tissue Prosthesis
Tissue prostheses tend to lose moisture when in a dry field, a process accelerated by heat generated from the
operating room overhead lights. The valvular tissue will be permanently damaged, which may result in premature
prosthetic failure. As a precaution, the prosthesis must be kept moist by intermittently rinsing it with normal saline
solution at room temperature.
Suture Placement in Prosthetic Sewing Ring
Suture needles are passed through the prosthetic sewing ring from below upward, with the needle exiting at the
junction of the outside half with the inside half of the sewing ring (Fig. 5.12B). Sutures placed in such a manner
in the sewing ring of a bioprosthesis are well away from the tissue-sewing ring interface and avoid traumatizing
or perforating the tissue leaflets. Similarly, the suture knots will face away from the orifice of a mechanical valve,
preventing contact with the disc or leaflets.
Bioprosthetic Struts Position
Before placing sutures in the prosthesis, every precaution should be taken to ensure that the tissue prosthesis is
oriented so that the struts do not obstruct the coronary artery ostia. In patients with bicuspid aortic valves, the left
and right coronary artery's ostia are usually displaced farther from each other. In such situations, one strut of the
bioprosthesis should be placed midway between the ostia. This strategy will likely ensure that the other two
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struts will not occlude the left or right coronary ostia.
Seating the Prosthesis
When all sutures have been accurately placed in the sewing ring, the prosthesis is gently lowered and fitted
snugly in the annulus. Many surgeons rinse the sutures with saline solution for its lubricating effect, allowing the
sutures to be pulled through the sewing ring more smoothly.
Narrow Sinotubular Junction
When the sinotubular junction of the ascending aorta is narrower than the aortic annulus, the appropriate size
prosthesis will be too large to pass through it. In such situations, the holder is removed and the prosthetic low-
profile valve is turned on end, then lowered and seated safely in the aortic annulus (Fig. 5.20).
Chemical or Thermal Injury to a Bioprosthesis
Antibiotics or other chemical solutions may react with glutaraldehyde and produce irreversible damage to the
tissue prosthesis. Therefore, these valves should be rinsed only with room temperature physiologic saline
solution.
Prosthetic Distortion
Some tissue prostheses have flexible rings. The surgeon should not attempt to manipulate and force a large
prosthesis into a relatively small aortic annulus because this may distort the flexible ring and the valve leaflets,
causing incompetence.
Obstructive Elements
No redundant tissue fragment, calcium, or subannular pledgets should protrude into the left ventricular outflow
tract in such a way as to prevent satisfactory opening and closing of the valve (Fig. 5.21). Normal valve function
must be ensured and any obstructing element removed before final anchoring of the prosthesis.
After the prosthesis has been satisfactorily seated, the sutures are tied down securely and cut short.
FIG. 5.20 Technique for implantation of the optimal size prosthesis through a narrow ascending aorta. A:
Sinotubular diameter. B: Annular diameter.
Direction of Tying
The direction of tying the sutures should always be parallel to the curve of the sewing ring (Fig. 5.22). Any
deviation from this principle may traumatize the leaflet tissue or the prosthetic valve through contact with the
suture material or the surgeon's fingertip.
Long Suture Ends
Sutures, when tied, must be cut short, and the direction of the knot must be leaning toward the periphery of the
sewing ring of the prosthesis. A long suture end will scratch the leaflet tissue, resulting in chronic irritation, injury,
and, finally, perforation of the tissue leaflets. A long suture end can also protrude into the prosthetic orifice and
interfere with the normal closure of the occluding mechanism of a mechanical valve.
Abnormal Location of the Coronary Artery Ostium
Occasionally, the orifice of the left main coronary artery is located next to the commissure of the aortic annulus. It
is important to orient a bioprosthesis so that the struts do not face the coronary ostium (Fig. 5.23).
Unobstructed Prosthesis Function
Before closure of the aortotomy, it is imperative that normal, unobstructed opening and closing of a mechanical
prosthesis be visually verified.
Septal Hypertrophy
Patients with long-standing aortic stenosis and/or hypertensive heart disease may have marked septal as well as
concentric hypertrophy of the left ventricle. The surgeon must be cognizant of any discrepancy in size between
the left ventricular outflow tract and the aortic annulus. Special technical details should be considered when
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implanting prostheses of different design.
The single-disc group of prostheses, exemplified by the Medtronic-Hall mechanical valve, can be rotated after
implantation to ensure free movement of the disc. The smaller part of the disc that descends into the left ventricle
must be positioned away from the septum. Most of the bileaflet prostheses can also be rotated and are subject to
the same principle of free movement of the leaflets. The leaflets are often positioned parallel to the septum. In
cases of extreme septal hypertrophy, there may be relatively decreased flow across the leaflet
close to and parallel with the septum. This possible theoretical disadvantage probably has no hemodynamic
consequence.
FIG. 5.21 Subannular projection of a bit of calcium or a pledget, which may limit motion of the valve.
When the left ventricular outflow is markedly limited by septal hypertrophy, some septal muscle mass can be
excised (Fig. 5.24). Alternatively, multiple vertical myotomies may allow the left ventricular outflow tract to open
up.
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