Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3740_Библиотеки_им_академика_М_И_Перельмана
.pdf
26
coronar
y
https://t.me/medicina_free
I. Vokshi and S. Tsui
valve regurgitation, one option would be to insert a balloon
tipped cannula into the coronary sinus via the right atrium
before applying the aortic cross-clamp so that retrograde cardioplegia could be commenced as soon as the aortic crossclamp is applied.
Aortic Valve Anatomy
The coronary ostia can vary in height and position relative to
the aortic annulus and the valve commissures. The normal
aortic valve is tricuspid with two of its leaets being referred
to by the associated coronary ostia, namely the left and the
right coronary leaets, and the third being the non-coronary
leaet. Above the aortic valve annulus, the aorta expands
into the sinuses of Valsalva. During systole, the aortic sinuses
allow full opening of the valve leaets to provide the maximal orice area. During early diastole, transient retrograde
Fig. 6.1 Key anatomical
relationships around the aortic
valve
ow of blood towards the aortic valve leaets creates vortices in the aortic sinuses and facilitates early leaet closure.
During aortic valve replacement, there are important
anatomical considerations (Fig.6.1). The left and non-coronary leaets of the aortic valve are contiguous with the
anterior mitral valve leaet and its brous skeleton forming
the aorto- mitral curtain. The membranous part of the interventricular septum lies in the sub-commissural triangle
between the right and the non-coronary leaets. The atrioventricular node is located in the interatrial septum just
behind the non- coronary sinus. This gives rise to the bundle
of His which runs towards the ridge of the muscular interventricular septum as it borders with the membranous septum. The bundle of His then splits into its three bundle
branches, with the left anterior and posterior bundle
branches coursing into the left side of the muscular septum
whilst the right bundle branch continuing down the right
side of the muscular septum.
Right
y artery
Membranous
septum
Right
bundle branch
Left bundle
branch
Left main
coronary arter
Anterior mitral
valve leaflet
v
6 Surgery forAortic Valve Replacement
https://t.me/medicina_free
27
Aortotomy fortheAortic Valve andExposure
When choosing the site, orientation and length of the aortotomy incision, it is important to consider the exposure that
it can afford and its ease of closure. The authors favour a
transverse aortotomy incision for its versatility and safety.
The pericardium overlying the groove between the aortic
root and the pulmonary trunk is incised longitudinally to sep-
Aortic cannula
Cardioplegia
cannulation
Aortic cross
clamp
Transverse
aortotomy
Two stage
enous cannula
arate these two structures. A transverse aortotomy incision is
made at a level 1cm distal to the fat pad as it reects off the
anterior surface of the aortic root. The incision should span
the anterior two-thirds of the aortic circumference from a
point 1cm distal to the inter-coronary commissure to a point
1cm distal to the left and non-coronary commissure (Fig.6.2).
This transverse aortotomy incision provides excellent exposure to the aortic valve and easy access to the coronary ostia
Stay
sutures
Fig. 6.2 The transverse aortotomy incision and the aortotomy incision with stay sutures inserted
28
enbaum scissors
https://t.me/medicina_free
I. Vokshi and S. Tsui
for direct cardioplegia administration. It avoids any aortic
root distortion and is also a safe distance away from the right
coronary ostium, giving plenty of margin for suture closure of
the aortotomy incision at the end of the operation. In the event
that exposure remains challenging, or if an ascending aortic
or root replacement is required, the transverse aortotomy can
easily be extended circumferentially. The other advantage of
a transverse aortotomy is that this incision avoids having one
end of the incision being deep in the non-coronary sinus
which can be difcult to access for haemostasis.
A stay suture is placed in the centre of the cranial edge of
the aortotomy to retract the hood of the ascending aorta. Stay
sutures are then placed at each end of the transverse aortotomy incision, and a further stay suture is placed in the centre
of the caudal edge. Retraction of the latter three stay sutures
elevates and swivels the aortic root towards the operator for
optimal exposure (Fig.6.2). If required, the operating table
can be tilted head up and towards the left to improve the line
of sight.
Fig. 6.3 Cross section of a
diseased aortic valve
demonstrating extension of
calcium beyond the leaet
hinge. Cutting directly onto
the edge of this calcium can
risk injury to the aortic valve
annulus (red dotted line).
Wedging the scissors blade
under the calcium plague can
separate the plaques off the
underlying aortic annulus.
Lifting and pushing these
plagues towards the valve
leaet will enable the scissor
blades to engage and cut
along the leaet hinge without
injuring the aortic annulus
(red dotted line)
Aortic Valve Excision andDebridement
Excision of the aortic valve leaets can be commenced at
any of the valve commissures. The key to success is having
an effective assistant surgeon to perform suction clearance of
blood and debride.
Once a chosen valve commissure is tangentially detached
from the aortic root with a pair of Metzenbaum scissors, the
commissure is split to separate the two adjoining leaet. The
surgeon retracts each leaet with forceps to put the intended
line of cut between the valve leaet and its annular attachment
under tension. It is important to note that the rim of calcium on
the valve leaet often extends beyond the line of attachment
between the leaet and the annulus (Fig.6.3). Therefore, cutting directly down onto the edge of the calcium would almost
certainly injure the underlying annular tissue. In order to avoid
this injury, a half-opened Metzenbaum scissors should be
placed along the edge of the calcium rim with one blade above
and one blade below the valve leaet. Even in the most heavily
Metz
places across the
calcium and used to
lever the calcium off
the annulus
Metzenbaum
scissors places
across the
calcium and
used to lever
the calcium off
the annulus
Forceps are
used to
retract the
leaflet
perpendicular
to the annulus
6 Surgery forAortic Valve Replacement
https://t.me/medicina_free
29
calcied valve, there is usually a plane between the rigid calcium plaques and the underlying annular tissue. The edge of
each scissors blade is used to nd this plane by carefully
wedging it between the calcium and the underlying annular
tissue and simultaneously pulling the scissor blade towards the
centre of the aortic annulus (Fig.6.3). Sometimes, applying a
twisting action to the scissors back and forth whilst gently
squeezing the handles to close the blades can help lever the
calcium plagues away from the underlying annular tissue.
With experience, it should be possible to prise most of the
calcium off the ventricular and aortic surfaces of the leaet to
reveal the true attachment line between the leaet and the
annulus. The leaet attachment can then be divided along this
line with the scissors blade. Sometimes, once the correct plane
has been developed, the rest of the leaet can be cleanly
avulsed with a combination of traction on the leaet and blunt
dissection with the back of the scissors blade.
Residual debris along the annulus must be meticulously
removed with a large rongeur and suction. Adherent plagues
are trapped within the scoop of the rongeur and lifted off the
annulus by a pulling or twisting action. A common misconception is to use the rongeur to crush or to cut. Another misconception is that a wash out at the end would provide a
more thorough removal of debris. Careful valve excision and
targeted suction during debridement prevent scattering of
loose debris. Pouring gallons of saline into the ventricle
thereafter is a ritual that offers no added benet.
Small breaches in the aortic annulus can often be excluded
with the valve sutures. However, a deeper breach may need
to be formally repaired before placing the valve sutures.
Further Myocardial Protection
After giving the rst dose of cardioplegia at initial aortic
cross-clamp, it is advisable to administer further 500mL of
cold blood cardioplegia every 20min thereafter. This can be
done either by direct coronary artery cannulation or by the
retrograde route if a coronary sinus cannula is already in situ.
It is also the preference of the author to use an epicardial cold
saline irrigation circuit at 4°C to provide additional myocardial protection. However, this cold circuit is only commenced
after the completion of annular debridement in order to avoid
ooding the operating eld and inadvertently washing loose
debris into the ventricular cavity.
Aortic Valve Sizing
Accurate sizing of the aortic annulus is a vital step in aortic
valve replacement. Undersizing results in a prosthetic valve
with a limited orice area and may increase the risk of para-
valvular leak due to excessive tension on the valve sutures.
Oversizing could lead to difculties with seating the valve
prosthesis resulting in paravalvular leak or obstruction of the
coronary ostia.
Prosthetic valve manufacturers provide dedicated sets of
valve sizer for each valve model. Most sizers come in the
form of a cylinder with or without an additional rim on its
surface to simulate the sewing cuff of the valve prosthesis. In
general, the appropriate sized prosthetic valve corresponds
to the largest sizer in which the cylindrical part could be
inserted across the aortic annulus but not the rim that simulates the sewing cuff if present.
It is important to ensure that the size of the valve prosthesis as indicated by the sizing process is appropriate for the
body size of the patient. If the annulus is too small and there
is a considerable risk of severe patient prosthesis mismatch,
an aortic root enlargement should be considered.
Aortic Valve Suture Placement
There are multiple suturing techniques described for aortic
valve replacement, each with their protagonists. In general,
the authors advocate adopting the supra-annular technique
for aortic valve replacement using horizontal mattress
sutures. If the aortic annulus is excessively enlarged (e.g.
>29mm), the intra-annular technique with everting sutures
may be preferred. Since mitral valve prostheses come in
larger sizes, an alternative would be to use a mitral prosthesis
for aortic valve replacement in patients with aortic annulus
measuring >29mm. For this approach, the valve prosthesis
would need to be held upside down without the valve holder
handle before passing the valve sutures through the sewing
cuff. The valve holder should be removed before parachuting
the valve prosthesis into the aortic valve annulus.
For the supra-annular technique, the rst valve suture is a
single-armed 2-0 braided polyester suture spanning across
the membranous septum, entering and exiting on the aortic
aspect of the right and non-coronary commissure (Fig.6.4).
The rest of the valve sutures are double-armed Teon-felt
pledgeted 2-0 braided polyester sutures passed from the ventricular to the aortic aspect of the aortic annulus. The sutures
are placed in a horizontal mattress fashion in a clockwise
sequence with each suture spanning a distance of 7–8mm
along the aortic annulus (Fig.6.4). Traction on each newly
placed suture elevates the aortic annulus to facilitate placement of the next suture, and so on. Leaving a 1mm gap in
between adjacent valve sutures helps to avoid spiking of the
previous suture with the needle of the next suture. Usually,
11–15 horizontal mattress sutures are required for aortic
valve replacement, depending on the size of the native aortic
annulus (Fig.6.4).
30
https://t.me/medicina_free
I. Vokshi and S. Tsui
Fig. 6.4 Top left, Location of the rst valve suture across the right and
non-coronary commissure entering and exiting 1mm from the valve
excision line and 7–8 mm apart. Retracting this suture towards the
patient’s left hip helps exposure for placement of the next suture. Top
The sutures are placed with the needle entering the tissue
perpendicularly to ensure a good depth of 2–3mm is achieved
before the point of the needle is swiveled towards the aortic
right, Horizontal mattress Teon-felt pledgeted valve sutures being
inserted in turn with each suture spanning 7–8mm and leaving a 1mm
gap between adjacent sutures. Bottom middle, All sutures in place for
the supra-annular technique
surface. Bearing in mind the anatomical structures around
the aortic annulus, particular attention needs to be paid in the
following locations:
6 Surgery forAortic Valve Replacement
https://t.me/medicina_free
Along theNon-coronary Annulus
The AV node and the bundle of His are just behind and below
the line of attachment of the non-coronary leaet. It is advisable to insert the valve sutures immediately below the leaet
excision line and allow them to exit a fraction higher in the
non-coronary sinus in order to avoid injuring the conduction
apparatus.
Along theAorto-mitral Curtain
It is important not to plicate too much tissue with the valve
sutures along the aorto-mitral curtain, particularly in the subcommissural triangle between the left and non-coronary leaflet. Otherwise, this would compress the height of the anterior
mitral valve leaet and give rise to mitral valve
incompetence.
Below theLeft andRight Coronary Ostia
31
At the nadir of the left and right coronary sinuses, the valve
sutures should exit on the aortic side no more than 2mm
above the leaet excision line in order to prevent the prosthetic valve sewing ring riding too high and causing obstruction to the coronary ostia. It is quite safe to start by inserting
the needles lower in the ventricular aspect along these areas
to ensure that there is a sufcient bite of tissue.
For the intra-annular technique, all the horizontal mattress
sutures are placed in an everting manner with the needles
inserted on the aortic side rst and exiting on the ventricular
side of the excision line of the aortic valve leaets, with the
Teon-felt pledgets resting on the aortic side (Fig. 6.5).
Again, this is started at the right and non-coronary commissure going around the annulus in a clockwise direction.
Once all the sutures are placed and counted, it is usually
time to start the process of re-warming of the patient. The
sutures are evenly spaced on the valve sewing ring starting
with the suture from the right and non-coronary commissure
and (Fig.6.6) working clockwise until all the sutures have
been passed (Fig.6.6).
For a stented bioprosthesis, the rst commissural suture
should be aligned with one of the valve posts. This will
ensure that the three valve posts are not positioned in front of
either of the coronary ostia. For bileaet mechanical valves,
the general consensus is to orientate the prosthesis so that the
hinge line lies transversely with one leaet facing anteriorly
and the other leaet facing posteriorly.
All the valve sutures are then gathered under tension to
take up any slack beneath the valve sewing ring before the
prosthetic valve is parachuted down onto the native annulus.
Fig. 6.5 All everting sutures in place for the intra-annular technique
The suture directly beneath the left coronary ostium is tied
rst followed by the one directly beneath the right coronary
ostium and then the nadir suture of the non-coronary sinus
(Fig. 6.7). This ensures that the valve prosthesis is seated
squarely in the supra-annular position and that the sewing
ring would not tilt and obstruct either of the coronary ostia.
All the remaining valve suture in between the three nadir
sutures are then tied in turn.
When tying each of the valve sutures, it is important that
sufcient downward pressure is applied to the valve sewing
ring with the nger on the knot to push the sewing cuff
against the annulus before the suture is tightened. This means
that the suture is simply tightened to hold the prosthesis in
that position, rather than leaving the prosthesis high initially
and then rely on tension on the suture to pull the sewing ring
down towards the annulus. Usually, it is sufcient to use ve
throws for the knot and locking the last three throws. When
all the sutures have been tied, the prosthetic valve leaets are
gently opened with a plastic probe to ensure that there are no
redundant suture loops beneath the valve. The sewing ring
should also be seen to be resting against the annulus with no
space in between. Each of the tied sutures can then be cut
ush with the knot (Fig. 6.7). Finally, clearance from the
coronary ostia is conrmed. A 4-0 polypropylene running
suture is used to close the aortotomy starting from each end
of the incision and tied in the centre (Fig.6.8).
32
https://t.me/medicina_free
I. Vokshi and S. Tsui
Fig. 6.6 To p , First valve suture placed through the prosthetic valve
sewing ring. Bottom, Valve suture being placed through the prosthetic
valve sewing ring in turn
Fig. 6.7 Top, Prosthetic valve parachuted down into the aortic annulus
and the three nadir sutures have been tied. Bottom, All valve sutures
have been tied and the sutures cut ush with the knots
6 Surgery forAortic Valve Replacement
https://t.me/medicina_free
Fig. 6.8 Closure of the transverse aortotomy incision from both ends
De-airing, Trans-oesophageal
Echocardiogram Assessment andWeaning
ofCardiopulmonary Bypass
For de-airing, the venous line of the bypass circuit is partially clamped to permit controlled lling of the heart. The
lungs are re-inated and ventilated. Suction on the pulmonary vein vent is temporarily suspended. The 8F cannula previously secured in the ascending aorta is connected to a
cardiotomy sucker, and the heart is massaged to direct blood
across the lungs and into the left heart. This is continued for
a minute or so until most of the air in the left heart chambers
has been expelled. Cardiopulmonary bypass ow is momentarily reduced to lower the aortic pressure for release of the
aortic cross- clamp. Thereafter, bypass ow is restored.
Cardiotomy suction on the pulmonary vein vent is resumed
to prevent left heart distension and to continue the de-airing
33
process. Ventricular and atrial epicardial pacing wires are
secured and connected to a temporary pacing box.
After a few minutes of reperfusion, cardiac activity usually
returns spontaneously. If required, the heart can be debrillated with DC cardioversion starting with 10 Joules. At this
stage, it is not uncommon to see bradycardia or heart block. If
so, sequential pacing at 80–90 beats per minute is commenced
with more lling of the heart to facilitate de- airing. When the
left atrium is sufciently full, the pulmonary vein vent can be
removed and the puncture site on the vein left opened for further passive de-airing of the left atrium.
Transesophageal echocardiography is invaluable in
assessing cardiac lling status, contractility, the presence of
regional wall motion abnormality and any occult pockets of
air. It is also used to inspect the newly inserted aortic valve
prosthetic for leaet opening and paraprosthetic leak. If the
ndings are satisfactory and the heart is fully de-aired, the
patient can be weaned off cardiopulmonary bypass.
However, no matter how thorough the de-airing process has
been up to this point, showers of air particles would invariably
appear when the patient is nally weaned off cardiopulmonary
bypass. Therefore, the authors would routinely continue with
cardiotomy suction on the 8F cannula in the ascending aorta at
a rate of 1L/min as well as leaving the vent site on the pulmonary vein open for 2–3min after weaning off bypass. During
this time, the patient is re-transfused from the bypass machine
at the same rate to maintain a steady lling pressure. When no
more air bubbles are observed on echocardiogram, the suture
on the pulmonary vein vent site can be tied and the cardiotomy
suction on the 8F cannula is discontinued. The heart is decannulated and residual heparin is reversed with an appropriate
dose of protamine sulphate. After haemosasis, anterior and
posterior pericardial drains are inserted and the sternotomy
incision is closed in a standard fashion.
References
1. Otto CM, Nishimura RA, Bonow RO, Carabello BA, Erwin JP, etal.
2020 ACC/AHA guideline for the management of patients with val-
vular heart disease. J Am Coll Cardiol. 2021;77(4):e25–197.
2. Vahanian A, Beyersdorf F, Praz F, Milojevic M, Baldus S,
Bauersachs J, et al. 2021 ESC/EACTS guidelines for the man-
agement of valvular heart disease: developed by the task force
for the management of valvular heart disease of the European
Society of Cardiology (ESC) and the European Association for
Cardio-Thoracic Surgery (EACTS). Rev Esp Cardiol Engl Ed.
2022;75(6):524.
Aortic Root Enlargement Techniques
https://t.me/medicina_free
RizwanQ.Attia, ShakilFarid, andStevenTsui
7
Aortic valve replacement can be challenging in the setting of
a small aortic annulus. If the native aortic annulus can only
accommodate a smaller-sized valve prosthesis, it would
result in a restricted effective orice area. When indexed to
the body surface area, this could result in patient prosthesis
mismatch in larger patients. This has been associated with
adverse outcomes such as increased left ventricular work,
inferior left ventricular mass regression and in some series,
increased early and late mortality. In active younger patients,
a high transvalvular gradient can lead to reduced exercise
capacity.
The body surface area of patients can be calculated preoperatively from their weight and height. According to published valve sizing charts and apps, the minimum size of
valve prosthesis required to avoid patient prosthesis mismatch can be prospectively determined. An intraoperative
transoesophageal echocardiogram can provide annular
dimensions for conrmation. Several techniques of aortic
root enlargement have been described to allow the insertion
of a larger prosthetic valve into a small aortic annulus. These
techniques are described in the following chapter.
The surgical set-up, access, and exposure are as described
in the chapter on aortic valve replacement. In addition, a
balloon-tipped coronary sinus cannula can be inserted for the
administration of retrograde cardioplegia. After the aorta is
cross-clamped and the heart is arrested, a transverse or an
oblique aortotomy is performed at the level of the sinotubular junction. The diseased aortic valve leaets are resected,
the valve annulus is thoroughly debrided and sized using
standard valve sizers.
The techniques described in this chapter will include the
Nicks procedure [1], the Manouguian-Nunez procedure [2,
3], the Konno-Rastan procedure [4], and the Y technique [5].
R. Q. Attia · S. Farid · S. Tsui (*)
Department of Cardiothoracic Surgery and Transplantation, Royal
Papworth Hospital, Cambridge, UK
e-mail: shakil.farid@nhs.net; steven.tsui@nhs.net
Geometric Consideration forAortic Root
Enlargement
In geometry, the circumference of a circle is equal to its diameter multiplied by the mathematical constant π (i.e.
3.14159….). Since manufacturers of aortic valve prostheses
usually supply each valve model with 2mm increments in
diameter (19mm, 21mm, 23mm, 25mm, etc.), the difference
in circumference between any one valve prosthesis and the
one next size up would be 2mm multiplied by πwhich equals
to 6.28318 mm; the difference in circumference between a
valve prosthesis and the one that is two sizes up would be two
times 2mm multiplied by π which equates to 12.56636mm.
For valves that are three sizes different, the difference in their
circumference would be three times 2 mm multiplied by π
which equates to 18.84954mm. So, 6.3 mm, 12.6 mm, and
18.9mm are the increases in circumference required to accommodate a prosthetic valve that is one, two, or three sizes larger
than the native aortic annulus, respectively.
In commonly with all techniques described for aortic root
enlargement, the native aortic annulus is incised, and a patch
of prosthetic material is sutured into the gap created. Since
the suture line between the patch and the native tissues must
incorporate 2.5–3mm of patch material, and there is a suture
line on each side of the patch, an additional 5–6mm must be
added to the increase in circumference desired to determine
the appropriate width of patch material required.
Depending on the magnitude of aortic annular enlargement desired, the following approximate width of patch
material should be considered:
Increase by 1 valve size = 6.3 mm + 6 mm = 12.3 mm,
rounded up to 13mm
Increase by 2 valve size= 12.6 mm + 6 mm = 18.6 mm,
rounded up to 19mm
Increase by 3 valve size= 18.9 mm + 6 mm = 24.9 mm,
rounded up to 25mm
These approximate patch widths are irrespective of what
the native aortic annular diameter is before enlargement.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
F. C. Wells (ed.), Atlas of Cardiac Surgery, Springer Surgery Atlas Series, https://doi.org/10.1007/978-3-031-43195-1_7
35
36
ab
https://t.me/medicina_free
R. Q. Attia et al.
Nicks Technique
For this a vertical incision is made in the aortic root across
the aortic annulus in the mid portion of the non-coronary
sinus and into the brous subaortic curtain (Fig.7.1a and b).
Ideally, the apex of this incision reaches 1.5–2cm below the
aortic valve annulus but this can be limited by the depth
available in the anterior mitral leaet. A patch of bovine
pericardium is shaped elliptically. The key to success is to
ensure that the patch at the level of the aortic annulus is of
sufcient width (see above). A 5-0 polypropylene running
suture is used to anastomose the patch to the margins of the
incised aortic root starting at the apex of the incision and
extending up each side of the incision (Fig. 7.2a). Each
suture line is continued about 2 cm cranial to the native
annulus (Fig.7.2b). A valve sizer of the anticipated size of
prosthesis is used to conrm the t and the valve position.
Some surgeons would nd it helpful to use a sterile surgical
marker pen to outline the edge of the valve sizer on the pericardial patch to aid positioning of the valve sutures. It is also
important to locate the coronary ostia to ensure that they are
well clear of the edge of the valve sizer and the valve posts
in case of a stented bioprosthesis. Similar to a standard aortic valve replacement in a native annulus, we would advocate supra-annular placement of the prosthetic valve with a
non-everting horizontal mattress technique using 2-0 pledgeted or non-pledgeted Ethibond sutures (non-absorbable
braided nylon sutures) around the annulus. The valve sutures
along the pericardial patch are horizontal mattress sutures
placed from the outside of the patch into the aorta (Fig.7.2c).
The sutures are then passed through the sewing cuff of the
prosthesis, and the valve is seated on the annulus and tied.
After the valve is tied down, close inspection is carried out
to conrm that the valve is well seated. The coronary ostia
are visualised to conrm no obstruction. The pericardial
patch used to enlarge the aortic root is now trimmed into
shape to match the aortic closure. A 4-0 running polypropylene suture is used for aortotomy closure. The aortic closure
suture is tied to the 5-0 polypropylene sutures used earlier
for the patch to complete the closure of the aorta. The nal
result of the closure is seen in the schematic diagram
(Fig.7.2d).
KonnoRastan
Fig. 7.1 (a) Aortic root accessed after aortic cross-clamping and transverse aortotomy. Strategically placed stay sutures as shown can facilitate
exposure. (b) The locations of incisions for the most commonly performed aortic root enlargement are shown by the dash lines
Manouguian-
Nunez
Nicks
Соседние файлы в папке Библиотека им академика М.И. Перельмана