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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. 22.2 A: Normal mitral valve annular configuration. B: Mitral valve annular configuration in an atrioventricular
septal defect.
Incision
This form of atrial septal defect is usually approached through a median sternotomy. A right submammary
thoracotomy incision can also be used (see Chapter 1).
Cannulation
The ascending aorta is cannulated in the usual manner (see Chapter 2). The superior and inferior vena cavae
are cannulated directly; tapes are then passed around both cavae. A vent is placed through the right superior
pulmonary vein and positioned in the left atrium proximal to the mitral valve. (The correct position can be
obtained after the heart is opened.)
Myocardial Preservation
Cold cardioplegic arrest of the heart is achieved and maintained by intermittent infusion of cold blood
cardioplegic solution into the aortic root (see Chapter 3).
Technique
A generous atriotomy is made from the base of the right atrial appendage to near the site of the inferior vena
cava cannulation, parallel with the atrioventricular groove. The
atriotomy edges are retracted with fine sutures that are sometimes pledgeted. The presence and severity of
mitral regurgitation must be carefully assessed. This may be carried out by simply injecting saline forcefully
through the mitral valve. The cleft on the anterior leaflet of the mitral valve should be closed even if there is no
valve incompetence at the time of surgery because these valves often become insufficient over time. This can be
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accomplished by approximating the “kissing” edges of the cleft starting at the annulus with three or four
interrupted 6-0 Prolene sutures (Fig. 22.4).
FIG. 22.3 Rastelli classification of atrioventricular septal defects. A: Type A. B: Type B. C: Type C.
FIG. 22.4 A: Regurgitation through the cleft. B: Repair of the cleft. C: “Kissing” edges of the cleft. D: Free
edges of the cleft.
Closure of the Cleft
Care must be taken to approximate only the kissing edges of the leaflet tissue, which are not the same as the
free edges of the cleft (Fig. 22.4C, D). Incorporation of an additional extent of the leaflet to secure a better repair
usually results in valvular insufficiency. The edges of the cleft are strong and quite fibrotic in older patients and
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consequently hold sutures well. In infants, the valve tissue may be somewhat friable. In these cases, horizontal
mattress sutures reinforced with pericardial pledgets can be used to close the cleft.
It is unusual to have significant valvular incompetence in the ostium primum type of defect. When it does occur,
aggressive reconstruction should be undertaken (see Mitral Valve Reconstruction section in Chapter 6). If the
ostium primum defect is small and does not allow full visualization of the mitral valve, the atrial septal defect
should be enlarged toward or into the fossa ovalis.
When the mitral valve repair has been satisfactorily completed, the atrial septal defect is closed with a patch of
autologous pericardium. A double-armed 5-0 or 6-0 Prolene suture is started midway on the common annulus
between the mitral and tricuspid valves, taking small bites of tricuspid leaflet tissue where it meets the mitral
valve (Fig. 22.5B). The suturing is continued in both directions until the superior and inferior annuli are reached.
The suture line along the septal aspect of the patch can be interrupted, which is particularly helpful if there is a
small ventricular component, which then can be closed simultaneously with this suture line.
FIG. 22.5 A: Exposure of an ostium primum atrial septal defect. B: Suturing technique for repair.
Incorporation of the Mitral Leaflet
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To prevent the possibility of creating or increasing mitral incompetence, the suturing should not incorporate the
mitral leaflet. The bites should include tricuspid tissue just where it is adherent to the underlying ventricular
septum.
After completing the suture line along the septal crest, the height of the pericardial patch is carefully measured.
Too short a patch will create upward traction on the annulus and can cause mitral insufficiency. The patch is
trimmed to the appropriate size and shape, and both needles are used to complete the suture line. The atriotomy
is then closed with a continuous suture of 5-0 or 6-0 Prolene. Deairing is carried out, and the aortic clamp is
removed. The aortic root vent is allowed to bleed into the operative field or connected to suction until good
ventricular ejections are achieved.
Risk to the Conduction Tissue
Deep suturing in the area between the tricuspid annulus and the coronary sinus may injure the conduction
tissue and produce heart block. Every precaution should be taken to avoid such a event by taking
superficial bites of endocardium only (the needle should be visible through the tissue) in this region. The
first several bites are near the mitral valve annulus (Fig. 22.5B). Alternatively, the right-hand side of the
patch should be left a little longer and sutured around the orifice of the coronary sinus so that it drains
under the patch into the left atrium to prevent heart block (Fig. 22.6). This technique is not to be used if
there is a left superior vena cava that drains directly to the coronary sinus, as it would result in significant
desaturation from mixing within the left atrium.
FIG. 22.6 Alternative suture technique for repair of an ostium primum atrial septal defect.
Preventing Hemolysis
A patch of autologous pericardium fixed in glutaraldehyde should be used. The use of Dacron or GORE-TEX
may result in hemolysis if even a small mitral regurgitant jet hits the patch.
COMPLETE ATRIOVENTRICULAR SEPTAL DEFECT
The most crucial factor to consider when performing surgery for atrioventricular septal defect is competence of
the mitral valve. A two-patch or single-patch technique can be used.
Cannulation
In small infants weighing less than 2 kg, hypothermic circulatory arrest allows optimal exposure. In most patients,
however, direct cannulation of the superior vena cava and the inferior vena cava is carried out. Placement of the
venous cannulas must not cause undue tension on the valvular apparatus. Aortic cannulation is performed as
usual. When hypothermic arrest is used, a single venous cannula is placed through the right atrial appendage for
cooling and rewarming and removed during the period of circulatory arrest. When continuous flow
cardiopulmonary bypass is used, a vent is placed through the right superior pulmonary vein and positioned
proximal to the mitral valve after the heart is opened.
Two-Patch Technique
A generous atriotomy is performed from just below the right atrial appendage down toward the inferior vena cava
parallel with the atrioventricular groove. The edges of the atriotomy are retracted with fine sutures, sometimes
buttressed with pledgets. Small leaflet retractors are used to provide additional exposure. The precise functional
and pathologic anatomy is assessed. Saline is injected into the ventricles to assess the coaptation relationships
between the inferior and superior leaflets. A 6-0 Prolene stay suture is used to approximate the left superior and
left inferior leaflets at their coaptation point in the plane of the ventricular septum. This forms the landmark for the
establishment of the future common annulus (Fig. 22.7). It is sometimes necessary to incise the left superior
and/or left inferior leaflets up to the annulus for better exposure and a more secure closure of the ventricular
septal defect. Any secondary chordal attachments to the ventricular septum that may interfere with closure of the
defect are divided, although usually these attachments can be preserved and the patch secured on the right
ventricular side of the crest below them. An appropriately sized, semicircular GORTEX patch is sutured with a
double-armed 5-0 Prolene to the right ventricular aspect of the ventricular septum (usually starting in the middle).
The first bite may be buttressed with a pledget (Fig. 22.7).
FIG. 22.7 Repair of a ventricular septal defect in a complete atrioventricular defect. Dotted line shows proposed
division of the inferior and superior leaflets.
Division of Bridging Leaflets
When deciding where to incise the superior and inferior leaflets, the chordal attachments may help define the line
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of separation between left- and right-sided components. However, it is of paramount importance to have
adequate left-sided leaflet tissue, so that often the leaflets are divided somewhat on the right ventricular side.
Prevention of Heart Block
The atrioventricular node lies in the atrial septum just anterior to the coronary sinus. The bundle of His extends
from the atrioventricular node through the central fibrous body into the ventricles under the membranous part of
the interventricular septum. Suturing of the patch to the ventricular septum should be well beyond the rim of the
ventricular septal defect so as not to produce any conduction injury.
Gentle traction on the suture facilitates suturing in both directions until the superior and inferior annuli are
reached. The needles are then brought out through the leaflets superiorly and inferiorly, and both ends of the
suture tagged.
Height of the Interventricular Septal Patch
Resuspension of the valve leaflets at the appropriate level is important. Therefore, the height of the ventricular
septal defect patch should correspond to the plane of the atrioventricular valve leaflets during the saline injection
into the ventricles (Fig. 22.8).
FIG. 22.8 Diagrammatic view of a complete atrioventricular septal defect from the right. The tricuspid or right half
of the common valve and the remainder of the right side of the heart have been removed to show the dimensions
for sizing the interventricular patch. The upper edge of the patch suspends the leaflets at the level of their annuli,
and the lower edge extends below the muscular crest on the right side of the interventricular defect so that
suturing will not injure the conducting bundle. LS, left superior; LL, left lateral; LI, left inferior.
A large patch of pericardium is then appropriately tailored to cover the atrial septal defect. The suture line that
crosses the common atrioventricular valve incorporates leaflet tissue as well as the GORTEX patch used to
close the ventricular septal defect. A continuous over-and-over suture is used if the leaflets have not been
incised. If the leaflet tissue has been divided, particular care must be taken to incorporate both sides of the
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leaflet tissue, that is, left and right atrioventricular valve tissue, as well as the interventricular gortex patch and
the interatrial pericardial patch. This is best accomplished with several horizontal mattress sutures of 6-0 Prolene
passed first through the tricuspid leaflet component, then through the upper edge of the GORTEX patch, then
through the mitral leaflet tissue, and finally through the inferior edge of the pericardial patch. All the sutures are
placed and tagged separately, then the pericardial patch is lowered into place and the sutures tied.
Deformation of the Leaflet Anatomy
Overzealous incorporation of the atrioventricular leaflet tissue in suturing may shorten the height of the leaflet
and produce valvular incompetence.
Once continuity of the ventricular and atrial patches has been established, the atrial patch is retracted into the
right atrial cavity, and the cleft between the left superior and inferior leaflets is approximated with interrupted
sutures bringing the kissing edges together. The left atrioventricular valve is tested for competence by injecting
saline into the left ventricle (Fig. 22.9A). Regurgitant flow noted at the inferolateral and/or superolateral
commissure may be controlled with pericardial pledgeted 5-0 or 6-0 Prolene horizontal mattress sutures placed
at the corresponding commissure (Fig. 22.9B). Trivial central regurgitant flow can be accepted, but every effort
should be made to achieve the most competent valve possible. Sometimes, a suture annuloplasty using a
double-armed 5-0 Prolene suture along the mitral annulus from commissure to commissure achieves the best
results. A pericardial pledget is placed at both ends of the double suture line, and the suture is tied over a Hegar
dilator that corresponds to the Z-zero mitral diameter for the patient's size (Fig. 22.9C).
The correct height of the pericardial patch is then carefully gauged, and the patch is trimmed accordingly. The
pericardial patch is sewn to the edges of the atrial septal defect, leaving the coronary sinus on either the left or
right side, as described for repair of an ostium primum defect (Figs. 22.5B and 22.6). This is achieved by a
continuous suture of 5-0 or 6-0 Prolene. Should the coronary sinus be left in the right atrium, care must be
exercised to take superficial bites near the conduction tissue.
High Left Atrial Pressure
After separation from cardiopulmonary bypass, the left atrial pressure may be elevated secondary to mitral valve
incompetence or left ventricular dysfunction. If the coronary sinus has been placed on the left atrial side of the
patch, this will result in high coronary venous pressure, which may impair coronary arterial perfusion.
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FIG. 22.9 A: Atrial patch with the completed suture line across the common atrioventricular valve. B: Mitral
annuloplasty with pledgeted sutures at the commissures. C: Suture annuloplasty tied over appropriately sized
Hegar dilator.
Valvular Competence
Residual moderate or severe valvular incompetence is not well tolerated. It is sometimes better to overcorrect
and produce mild stenosis than to accept even mild mitral valve insufficiency.
Incorrect Height of Patches
A perfect valvular repair can be distorted, leading to mitral valve incompetence if either the ventricular or atrial
septal patch is too tall or too short.
One-Patch Technique
Before cannulation, a large piece of pericardium is harvested, placed in glutaraldehyde, and rinsed in saline.
After the right atrium is opened, the leaflets are assessed by filling the ventricles with saline. Coaptation of the
superior and inferior leaflets overlying the ventricular septum is evaluated. A 6-0 Prolene suture is placed at the
leading edges of the inferior and superior leaflets to determine the point of partition of the common
atrioventricular valve into left- and right-sided valves.
The distance between the two points on opposite sides of the annulus where the ventricular septal crest meets
the atrioventricular groove is measured. This determines the width of the patch at the annular level. If the patch
is too wide, the left atrioventricular valve annulus will be increased, and this may lead to mitral regurgitation. If
the left atrioventricular valve tissue is believed to be insufficient, then the width of the patch should be less than
the measured distance between the two points on the annulus. This will reduce the size of the left atrioventricular
valve annulus and help create a competent valve.
Leaflet incisions are nearly always required in the superior and inferior leaflets to allow placement of the
pericardial patch. The leaflets should be incised in a line parallel with and overlying the ventricular septal crest,
with the incision extending to the level of the annulus (Fig. 22.10).
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FIG. 22.10 Division of leaflets overlying the ventricular septal crest.
FIG. 22.11 Attaching a pericardial patch to the right ventricular aspect of the defect.
Inadequate Left-Sided Valve Tissue
The superior and inferior leaflets should be divided somewhat on the right ventricular side to ensure
adequate left-sided leaflet tissue for a competent mitral valve.
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The pericardial patch is attached to the right ventricular aspect of the defect beginning in the midportion
with a running 5-0 Prolene suture. The suture line is continued, weaving in and out of the chordal
attachments, until the annulus of the atrioventricular valve is reached both superiorly and inferiorly (Fig.
22.11). With the two ends of this running suture tagged, the pericardial patch is held up within the atrium
and the leaflets are suspended from the patch at the correct level with the chordal structures under slight
tension. The left-(mitral) and right-(tricuspid) sided valve components are reattached to the pericardial patch
initially with a running 6-0 Prolene suture that is secured on both ends of the patch by tying it to the
previously placed 5-0 Prolene stitch. The leaflet attachment to the pericardium is then reinforced with
multiple pericardial pledgeted horizontal mattress sutures of 5-0 or 6-0 Prolene (Fig. 22.12A, B). Traction
sutures on the upper edges of the pericardial patch allow the surgeon to deflect the patch back and forth to
visualize the left and then the right side of the repair.
The cleft between the superior and inferior leaflet components of the left atrioventricular valve is
approximated with interrupted sutures as described in the preceding text. The left atrioventricular valve is
again tested with saline, and any areas of regurgitation are noted and repaired as discussed in the Two-
Patch Technique section. The remainder of the pericardial patch is then secured to the atrial septal defect
as described previously (Fig. 22.13).
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