Aortic Valve-Sparing Operations
Keywords: Aortic Valve-Sparing Operations, Operations for Valvular
Heart Disease, aortic root aneurysm, aortic insufficiency
Abstract
Aortic valve-sparing operations have become part of the
surgical armamentarium to treat aortic root aneurysm and ascending aorta
aneurysm with aortic insufficiency. Both types of procedures, remodeling of the
aortic root and reimplantation of the aortic valve have provided excellent long
term results when the procedure is correctly matched to the aortic root
pathology.
· The aortic root is the anatomic
segment between the left ventricle and ascending aorta. From the surgical
viewpoint, it consists of the aortic annulus (AA), aortic cusps, aortic
sinuses, and sinotubular junction (STJ). Although the term aortic annulus may
be anatomically incorrect, it is often used in surgical anatomy and pathology
to describe the aortoventricular junction. Approximately 45% of the
circumference of the AA is attached to muscular interventricular septum, and
55% is attached to fibrous tissue, as shown in Fig. 13.1. This fibrous tissue
is the membranous interventricular septum and the fibrous body that connects
the anterior leaflet of the mitral valve to the aortic root.
· The AA is scalloped and attaches
the aortic cusps to the aortic root and left ventricle. The portion of the AA
corresponding to the noncoronary cusp is attached entirely to fibrous tissue,
whereas the portions corresponding to the left and right coronary cusps are
partially attached to fibrous tissue and partially to cardiac muscle. The
highest point of the AA, where two cusps meet, is the commissure. The anatomic
arrangement of the AA creates a triangular space beneath the cusps, termed the subcommissural
triangle. There are three commissures and three subcommissural triangles.
The STJ lies immediately above the commissures and separates the aortic root
from the ascending aorta. The arterial wall contained between the AA and STJ
creates the aortic sinuses, or sinuses of Valsalva. The three aortic cusps have
a crescent shape and often are of different sizes, but the length of the base
of a cusp is always 1.5 times longer than the length of its free margin (FM),
as illustrated in Fig. 13.2. Thus, a large cusp will have a proportionally
longer base (AA), longer FM, longer intercommissural distance along the STJ,
and larger aortic sinus. The noncoronary and right cusps and sinuses are often
larger than the left cusp and left aortic sinus.
· The AA is a three-dimensional
structure that evolves along three separate planes, as illustrated in Fig.
13.3A–C. Each aortic cusp is inserted in the annulus along a horizontal plane
(see Fig. 13.3D). For practical purposes, we usually refer to its diameter as
the maximal distance at the level of its nadir.
· The relationship of the diameters
of the AA at this level and at higher levels until reaching the commissures
(STJ) varies with age. In children and young adults, the diameter of the AA is
15% to 20% larger than its diameter at the level of the commissures (STJ). As
the elastic fibers of the arterial wall decrease with age, the STJ dilates and
tends to become equal to the diameter of the lower AA in adults. However, the
AA of each cusp evolves along a single horizontal plane (see Fig. 13.3).
· Ascending aortic aneurysms can
cause aortic dissection or rupture when their transverse diameter exceeds 55
mm. Aneurysms of the ascending aorta can also cause dilation of the STJ, with
consequent aortic insufficiency due to lack of coaptation of the cusps, as
illustrated in Fig. 13.4. One or more aortic sinuses may also become
secondarily dilated, but the AA often remains normal. Patients with ascending
aortic aneurysms and aortic insufficiency are usually in their sixth or seventh
decade of life. If the aortic cusps are normal or minimally elongated along
their FMs, it is possible to replace the ascending aorta with correction of the
diameter of the STJ, replace one or more sinuses if necessary, repair the cusps
if there is prolapse, and reestablish aortic valve competence.
· Aortic root aneurysms usually
start with dilation of the aortic sinuses and, with time, the dilation extends
proximally into the AA and distally into the STJ. Patients with an aortic root
aneurysm are usually in the second to fourth decade of life when they need
surgery, and the aneurysm is often associated with genetic syndromes, such as
Marfan syndrome, Loeys-Dietz syndrome, and others. The two subcommissural
triangles of the noncoronary cusp flatten as the AA dilates, which decreases
the coaptation area of the cusps and may cause aortic insufficiency (Fig.
13.5). The indication for surgery is usually based on the diameter of the
aortic sinuses and family history of aortic dissection. In most cases, surgery
is recommended when the diameter reaches 50 mm and less if there is a family
history of aortic dissection.
· This chapter reviews the operative
techniques used to preserve the aortic valve in patients with ascending aortic
aneurysm and aortic insufficiency, as well as patients with aortic root
aneurysm, with or without aortic insufficiency. The term aortic
valve-sparing operation was introduced to describe these procedures.
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Figure 13.1 Photograph of an aortic root.
Figure 13.3 Geometric relationship among various components of the aortic root.
Figure 13.2 The aortic annulu evolves along
a cylinder.
Step 2. Preoperative Considerations
· Patients with an ascending aortic
aneurysm are usually asymptomatic, even if they have aortic insufficiency.
Although echocardiography often establishes the diagnosis of an ascending
aortic aneurysm and provides information regarding aortic valve function,
computed tomography (CT) or magnetic resonance imaging (MRI) of the aorta is
necessary to determine the extent of the aneurysm. The transverse arch is often
involved in older patients with aneurysm of the ascending aorta and aortic
insufficiency.
· Most patients with aortic root
aneurysm are asymptomatic and have only mild or no aortic insufficiency. Some
patients complain of vague chest pain. Severe chest pain is suggestive of rapid
expansion or an intimal tear with dissection. Echocardiography establishes the
diagnosis and gives information regarding aortic valve function. CT or MRI of
the aorta is also diagnostic and provides useful information on the remaining
thoracic aorta, although the transverse arch is seldom involved.
·
Transesophageal echocardiography
(TEE) is the best diagnostic tool to study the aortic valve and the mechanism
of aortic insufficiency in patients with ascending aortic or aortic root
aneurysm, as well as to measure the diameters of the AA, STJ, and cusp height.
Each component of the aortic root must be carefully interrogated, particularly
the aortic cusps. The number of cusps, their thickness, appearance of their
FMs, and excursion of each cusp during the cardiac cycle must be examined in
multiple views. The coaptation lines of the aortic cusps should be interrogated
by color Doppler imaging. The direction and size of the regurgitant jets should
be recorded in many views. Information regarding the morphologic features of
the AA, aortic sinuses, STJ, and ascending aorta should be obtained. Obviously,
the aortic cusps are the most important determinant of aortic valve repair. If
the cusps are thin and mobile and have smooth FMs, the feasibility of aortic
valve repair is very high, including patients with bicuspid aortic valves.
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Figure 13.5 Dilation of the sinotubular junction prevents the cusps from coapting
and causes aortic insufficiency.
Figure 13.4 Dilation of the aortic annulus
flattens the subcommissural triangles of the noncoronary cusp and pulls the
belly of the cusps apart.
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Step 3. Operative Steps
·
Aortic valve-sparing operations
are usually performed through a median sternotomy, but the procedure can also
be done through a limited skin incision (8–10 cm) and a partial or full median
sternotomy.
· Cardiopulmonary bypass is
established by inserting an arterial cannula into the proximal aortic arch if
only the aortic root and proximal ascending aorta are involved or into the
right axillary or innominate artery if the aortic arch needs replacement.
Venous drainage for car- diopulmonary bypass is usually done with a single
double-stage cannula placed in the right atrium or with bicaval cannulation
when the mitral valve also needs repair. The heart is protected during aortic
clamping by giving cold blood cardioplegia directly into the coronary arteries
intermittently. I maintain the systemic temperature at around 34°C (93°F). If
the aortic arch needs replacement, it is done first under moderate systemic
hypothermia (22°–25°C; 72°–77°F) and continuous antegrade cerebral perfusion
through the right axillary or innominate artery. A cannula is also inserted
into the left carotid artery if the pressure in this artery is less than 50% of
that in the innominate artery. If the mitral valve needs repair, it is done
before the aortic root pathology is addressed.
· Intraoperative TEE is indispensable
in aortic valve-sparing operations for assessment of aortic valve function
before and after repair of the valve.
· The ascending aorta is transected
5 to 6 mm above the STJ and the aortic cusps are inspected. Although this
inspection is largely to confirm what a preoperative transesophageal
echocardiogram has already shown, stress fenestration close to the commissural
areas and minor degrees of elongation of the FMs are not easily detected
preoperatively.
· The aortic insufficiency is
usually due to dilation of the STJ. Correction of the valve dysfunction is
accomplished by reducing the diameter of the STJ by suturing a graft of
appropriate diameter to it. The simplest method to determine the diameter of
the graft is to approximate the three commissures until the cusps coapt
centrally. Valve sizers such as the Medtronic Freestyle (Medtronic,
Minneapolis) are metric and handy for this purpose. When in doubt between two
sizes, it is safer to take the larger one because the STJ can be further
reduced under echocardiographic guidance after completion of the operation by
plication of the spaces between two commissures. In adult patients,
small-caliber grafts may increase left ventricular afterload. Thus, if the
estimated diameter of the STJ is 22 mm in a patient with a body surface area of
2 m2, a larger graft (26 or 28 mm) should be used and reduced to 22 mm at the
end where the graft is going to be used to correct the diameter of the STJ.
Fig. 13.6 illustrates this operative procedure. Before the graft is sutured to
the STJ, the graft should be divided into thirds to correspond to each
commissure. If one cusp is larger than the others, the intercommissural
distance should be proportionally larger.
 |
Figure 13.6
Replacement of the
ascending aorta with an appropriately sized graft restores valve competency by
reducing the sinotubular junction.
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· If the noncoronary aortic sinus is
excessively dilated or dissected (in cases of aortic dissection), it should be
replaced. The graft is divided into thirds according to the spaces between commissures, and a neoaortic sinus is fashioned, as illustrated in Fig. 13.7. The
height of the tailored neoaortic sinus should be approximately the same as the
diameter of the graft. Next, the commissures of the noncoronary cusp are
secured to the graft, and the neoaortic sinus is sutured to the remnant of the
arterial wall and AA with continuous 4-0 polypropylene sutures. The remaining
part of the graft is sutured to the STJ along the left and right aortic
sinuses. If the noncoronary and right aortic sinuses are dilated or dissected,
they should be replaced as described previously and illustrated in Fig. 13.8.
In this case, the right coronary artery should be reimplanted into its
neoaortic sinus.
 |
Figure 13.7 The noncoronary aortic sinus may be dilated and can be replaced at the
same time as replacement of the ascending aorta with an appropriately tailored tubular Dacron graft.
Figure 13.8 The noncoronary and right aortic sinuses may have to be replaced.
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· Finally, if all three aortic
sinuses are dilated, the sinuses are excised, leaving 5 mm of arterial wall
attached to the AA. The coronary arteries are detached from their sinuses along
with 5 mm of arterial wall around their orifices (Fig. 13.9A). The three
commissures are suspended at the same level and positioned in such way as to
allow the three cusps to coapt centrally (see Fig. 13.9B). The diameter of the
circle that includes all three commissures can be estimated with metric aortic
valve sizers. As before, when in doubt between two sizes, it is safer to choose
the larger one. Three neoaortic sinuses are tailored in one of the ends of the
graft (see Fig. 13.9C). The width of the neoaortic sinuses is proportional to
the size of the cusps and intercommissural distances. The arterial wall
immediately above the commissures is secured to the graft, and the neoaortic
sinuses are sutured to the remnants of the native aortic sinuses and AA with
continuous 4-0 polypropylene sutures (see Fig. 13.9D). The coronary arteries
are reimplanted into their respective sinuses (see Fig. 13.9E). To avoid late
aneurysm formation in the arterial buttons, the diameter of the openings in the
neoaortic sinuses should not exceed twice the diameter of the coronary
arteries.
· The foregoing operative techniques
are known as remodeling of the aortic root. After correction of the dilated STJ
and replacement of one or more aortic sinuses, as described previously, the
cusps should coapt well above the level of the nadir of the AA. If one or more
cusps coapt at a lower level than the others, the FM is elongated and should be
shortened by plication along the nodule of Arantius, as illustrated in Fig.
13.10. This is done with 6-0 or 5-0 polypropylene sutures, depending on the
thickness of the cusp.
·
A cusp with stress fenestration
along its commissural edge can be reinforced by weaving a double layer of fine
(6-0 or 7-0) polytetrafluoroethylene sutures along its FM, as illustrated in
Fig. 13.11. After completion of the aortic root remodeling, valve competence is
assessed by injecting cardioplegia into the graft under pressure. If the
ventricle does not distend, there is no aortic insufficiency or only a trace
because mild aortic insufficiency causes distention of the ventricle.
 |
Figure 13.9 All three aortic sinuses can be replaced with a
tailored tubular Dacron graft.
·
Although the previously described
aortic root remodeling procedure, with replacement of all three aortic sinuses,
has been used to treat patients with aortic root aneurysm, I believe that the
AA dilates in some patients late after surgery, particularly in those with an
associated genetic syndrome, limiting the durability of the valve repair. Thus,
in young adults with an aortic root aneurysm, the technique of reimplantation
of the aortic valve has been shown to provide more durable results. This
operation is more complicated than remodeling the aortic root because greater
knowledge of the functional anatomy of the aortic valve is needed to
reconstruct the AA, STJ, aortic sinuses, and sometimes the aortic cusps as
well.
· Reimplantation of the aortic valve
starts by freeing the aortic root from surrounding structures and excising the
three aortic sinuses, as described earlier for the remodeling procedure (see
Fig. 13.9A and B). Five to 6 mm of aortic sinus wall is left attached to the AA
all around. Stay sutures are placed immediately above each commissure for
traction.
 |
Figure 13.10 Cusp prolapse can be corrected by plication along the
nodule of Arantius.
Figure 13.11 Cusps with large fenestration can be reinforced with a
double layer of fine expanded polytetrafluorethylene suture above and below the defect.
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·
The aortic root is then dissected
free from the pulmonary artery and right ventricle, down to a level immediately
below the AA. On the right side of the aortic root, it may be difficult, if not
impossible, to separate the subcommissural triangles of the noncoronary cusp
from the right and left atria because their insertion in the root may be at a
higher level than the base of those triangles. The dissection is extended down
to the level of the insertion of the atria in the aortic root. Next, multiple
horizontal mattress sutures of 2-0 or 3-0 polyester are passed from the inside
to the outside of the left ventricular outflow tract, immediately below the
nadir of the AA, through a single horizontal plane along the fibrous portion of
the outflow tract, and along its scalloped shape in the interventricular
septum, as illustrated in Fig. 13.12A. These sutures are passed through the
base of the subcommissural triangles of the noncoronary cusp, along a
horizontal plane that corresponds to a level immediately below the nadir of the
AA. Depending on the height of the membranous septum, the sutures may have to
be a bit higher than the nadir of the AA to avoid the bundle of His. These
sutures may incorporate part of the right and left atria if their insertion is
higher than that horizontal plane. If the membranous septum and anterior leaflet
of the mitral valve is often thin and soft, Teflon pledgets should be used in
these sutures.
· The heights of the cusps are
averaged, and a tubular Dacron graft with a diameter equal to double of that
average is selected for reconstruction of the root. Conversely, the diameter of
the graft can be estimated as described for the remodeling technique or by
using the height of the commissure between the left and noncoronary cusps.
·
Three equidistant marks are placed
in one end of the graft to correspond to each commissure. A triangular segment
of 5 mm is cut off along the mark that corresponds to the subcommissural
triangle of the left and right cusps (see Fig. 13.12A). The sutures previously
placed in the left ventricular outflow tract are now passed through the graft.
The sutures should be spaced symmetrically if the AA is not dilated (see Fig.
13.12B). If there is obvious dilation of the AA, the sutures should be spaced
symmetrically along the muscular component of the outflow tract and closer
together beneath the subcommissural triangles of the noncoronary cusp because
that is where dilation occurs in patients with connective tissue disorders. The
level at which these sutures are passed through the graft is also important and
should reproduce what was done when they were passed through the left
ventricular outflow tract.
·
The sutures are tied on the
outside of the graft. Care must be exercised not to purse-string this suture
line. The graft is then cut in a length of approximately 5 cm and pulled up
gently, and the three commissures are also pulled vertically and temporarily
secured to the graft with transfixing 4-0 polypropylene sutures, but they are
not tied (see Fig. 13.12C). Once the three commissures are suspended inside the
graft, the commissures and cusps are inspected to make sure that they are all
correctly aligned. Next, the sutures are tied on the outside of the graft and
used to secure the AA into the graft. This is accomplished by passing the
suture sequentially from the inside to the outside right at the level of the
annulus and from the outside to the inside at the level of the remnants of the
arterial wall. I start at the level of the commissure and stop at the nadir of
the AA, where the sutures are tied together on the outside of the graft. The coronary
arteries are reimplanted into their respective sinuses.
·
The coaptation level of the aortic
cusps is inspected; it should be well above the level of the nadir of the
annulus. If one or two cusps coapt at a lower level, the FM can be shortened,
as illustrated in Figs. 13.10 and 13.12D. If fenestrations are present, the FM
can be reinforced with a double layer of 6-0 or 7-0 polytetrafluoroethylene
sutures (see Fig. 13.11). The graft can be clamped distally, and cardioplegia
given into the aortic root to test for valve competence, as described for
remodeling of the aortic root.
· Finally, the graft is sutured to
the distal ascending aorta, as illustrated in Fig. 13.12E. I believe that the
most durable reimplantation procedure is when a straight tubular Dacron graft
is used. If neoaortic sinuses are desirable, a graft 2 or 4 mm larger than what
is needed is selected and plicated to reduce its diameter in the area
corresponding to the nadir of the AA and in between commissures (see Fig.
13.12E). The average graft size used in reimplantation of the aortic valve is
28 to 30 mm when a straight graft is used and 30 to 32 mm when neoaortic
sinuses are created.
· Reimplantation of the aortic valve
is also extremely valuable for patients with an incompetent bicuspid aortic
valve, when the AA is frequently dilated. Patients with acute type A aortic
dissection who have a dilated aortic root are also good candidates for this
type of aortic valve-sparing procedure.
 |
Figure 13.12 Reimplantation of the aortic
valve.
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Step 4. Postoperative Care
·
The operative mortality rate for
aortic valve-sparing operations is low in elective cases (< 2%), even in
patients who require more extensive operations, including mitral valve repair,
replacement of the aortic arch, and myocardial revascularization. These
patients do not require any procedure-specific care in the intensive care unit
or ward. In my experience, patients with an ascending aortic aneurysm and
aortic insufficiency often have a transverse arch aneurysm and sometimes mega
aorta syndrome. These patients require more extensive vascular surgery than
those with aortic root aneurysm, with consequently higher rates of
postoperative complications such as stroke, myocardial infarction, renal
failure, and respiratory failure. However, more than 90% of all patients
experience no serious postoperative complications.
·
Postoperative bleeding is
relatively common and, in my experience, approximately 50% require blood
products. New heart block is rare (< 1%). Atrial fibrillation occurs in
approximately 20% of these patients and is managed pharmacologically. Patients
with an aortic root aneurysm associated with a genetic syndrome and those with
an aortic dissection should receive a beta blocker, if tolerated. No oral
anticoagulation is given unless atrial fibrillation persists for more than 24
hours or they have had a mitral annuloplasty ring or band, in which case they
receive heparin initially and warfarin for 3 months.
·
Echocardiographic studies to
assess aortic valve function should be performed annually in all patients. In
those with more extensive vascular disease or aortic dissection, periodic CT
scanning or MRI of the aorta is also important during follow-up.
Step 5. Pearls and Pitfalls
· Aortic valve-sparing operations
are complex procedures. A sound knowledge of the functional anatomy and
pathology of the aortic root and technical expertise are needed for their
performance. As with any other type of heart valve repair, it should not be
performed if the aortic cusps are grossly abnormal. From the preoperative
selection of patients by TEE to the intraoperative analysis of the aortic cusps
and root and what is needed to restore the functional anatomy of the aortic
valve, every step is crucial.
·
Sizing of the graft is difficult
for the surgeon who is learning to perform these operations. Sizing of the
graft is easier for remodeling of the aortic root than for reimplantation of
the aortic valve. The guidelines for sizing the graft for reimplantation of the
aortic valve given in this chapter are based more on clinical experience than
on scientific investigation of functional anatomy. The length of the FMs of the
cusps, degree of scalloping of the AA, and diameter of the STJ can all be
altered during reconstruction of the root, but the height of the cusps cannot.
For this reason, I use the average height of the cusps to estimate the
appropriate diameter of the AA at the level of its nadir. By using grafts with
a diameter equal to twice the average height of the cusps, the radius of the
reconstructed AA becomes equal to the height minus the thickness of the
aortoventricular junction because it is sutured inside the graft. This
reduction in diameter of the annulus has proven effective in allowing the cusps
to coapt well above the nadir of the annulus, and it provides a good seal of
the aortic orifice during diastole.
·
The level of coaptation of the
aortic cusps has been shown to be important for the durability of these
procedures. If the cusps coapt at the same level as the annulus, the
probability of prolapse of a cusp with consequent aortic insufficiency is
greatly increased, compared with cusps that coapt at least 8 mm above the nadir
of the AA. Thus, sizing of the graft and shortening the length of the cusps’
FMs are extremely important determinants of late valve function.
·
As illustrated in Fig. 13.3, the
AA evolves along single horizontal planes. The only geometric shape suitable to
stabilize a dilated AA is a cylinder. Thus, a straight tubular Dacron graft is
probably the best shape for reimplantation of the aortic valve. Newer grafts
with neoaortic sinuses are spherical and probably deform the AA once the valve
is secured inside them. Thus, I do not recommend these grafts for
reimplantation.
·
Aortic valve-sparing operations
are extensive, and hemostatic anastomoses between the various components are of
utmost importance. Coagulopathy at the end of a long cardiopulmonary bypass is
common, and every measure must be taken to avoid mechanical bleeding.
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