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spaces of the aortic root surrounding the aortic leaflets that promote and regulate their
opening and closing movements during the cardiac cycle. The role played by the sinuses of
Valsalva in regulating movements of the aortic valve leaflets is well known. The anatomic
features partially explain the complexity of valve hemodynamics: several studies shed light
on the refined interactions between the aortic valve and its structures (VAJ, VBR, leaflets
attachments, commissures and inter-leaflets triangles), the sinuses of Valsalva, and the ST
junction (“from shape to function”) [8-12].
The functional geometry of the normal trileaflet aortic valve, where the total length of the
free margins equals the circumference and exceeds that of the inter-commissural distances, is
an arrangement that allows wrinkle-free coaptation of the three cusps during diastole, as well
as full opening during systole. In this way the aortic valve averts the systolic pressure load
completely, and on the other hand, when diastole occurs, it is “ready” to receive the diastolic
pressure load with its cusps smooth, fully extended, and in a linear approximation [13].
During the systole, the aortic root is more cylindrical due to annular contraction and
commissures expansion (via the transmission of ventricular pressure through the inter-leaflet
triangle); during the diastole, a “recoil” occurs to restore a static balance. However, the aortic
root deformation during the cardiac cycle is also characterized by an overall systolic increase
in its diameter in order to maintain the leaflets flat through the whole sequence of leaflet
opening. The total area of the leaflets when compared to the aortic root is approximately 40%
greater, with the largest area measured in the non-coronary leaflet and the smallest to the left
coronary leaflet in most cases. This observation is fundamental in understanding the
importance of aortic valve coaptation and the importance of the right proportion between
overall root area and cusp surface. During diastole, cusp coaptation is indeed guaranteed by a
long contact between the bellies of the three leaflets explaining the importance of a good
proportion between cusp area and root dimension. An increase in root dimension will
invariably lead to a reduction of cusp tissue available for coaptation [6].
Finally, the anatomic relationships of the external side of aortic root with the contiguous
cardiac structures have fundamental relevance for surgical dissection of the root needed to
reach and expose the aortic annulus. On the external surface of aortic root the limit of the
surgical dissection corresponds to the roof of left atrium on the side of the non - and left
coronary sinus, while it corresponds to myocardium coming from the interventricular septum
and continuing laterally to the right ventricular outflow tract on the side of right coronary
sinus. It is important to point out the presence of a cleavage plane between the muscular
component of the left ventricle and the infundibulum of the right ventricle. This is the
anatomical plane that permits externally to reach the level of the virtual basal ring despite the
presence of muscular fibers as part of the VAJ [6, 7].
With these more or less virtual lines in mind El Khoury and colleagues introduced the
concept of the functional aortic annulus (FAA) followed by a description of a functional
classification of aortic regurgitation (AR). The FAA is comprised of (I) the ST junction, (II)
the semilunar attachments of the aortic leaflets and, (III) the VBR. All the structures
intersected by these lines are crucial for the anatomic and functional integrity of the aortic
valve; in this way the FAA could be considered the real “skeleton” of the aortic root. The type
I classification of AR represents the “pure” AR secondary to abnormalities of the aortic wall
then largely due to lesions of the FAA; in this case the AR can be due to dilatation of ST
junction and ascending aorta (type Ia) or dilatation of Valsalva’s sinuses, ST junction and
ascending aorta (type Ib) or dilatation of aortic annulus, (type Ic) that practically corresponds
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to the “annulo-aortic ectasia.” Substantially, in these alterations the aortic valve presents
various degrees of AR with relatively undamaged leaflets (highly depending on the duration
of the disease). Type II AR is due to intrinsic leaflet disease like leaflet prolapse as a result of
excessive cusp tissue or commissural disruption. Finally, type III AR is due to leaflet
restriction as the result of calcification, thickening, and fibrosis of the aortic valve leaflets
[14].
The use of a standardized functional classification is important because it will assist in
the interpretation of trans-esophageal echocardiography (TEE) studies with specific reference
to anatomical lesions and description of the pathology, but also in identifying optimal
candidates for surgical repair. Important lessons in this regard may be learned from a parallel
with the development of mitral valve repair. The Carpentier classification of mitral valve
regurgitation has been instrumental in the diffusion and evolution of techniques for the mitral
valve repair. Recently for bicuspid aortic valve (BAV) a new classification of phenotypes
based on the commissural orientation further codified some anatomical characteristics
suggesting specific surgical approaches [15]. This classification needs further validation with
regards to surgical techniques and long-term outcomes but, once again, underline the
importance of classification in a proper standardization of surgical techniques.
The Role of Imaging
Currently available imaging provides detailed information of the abnormalities in each
component of the aortic root and these informations includes the size and shape of the
annulus and ST junction as well as cusp anatomy and function. For adult male the mean
diameter of aortic annulus with normal aortic valve was 23.1 ± 2.0 mm (approximately 10%
smaller in women) and is closely related to body size (from 20.7 mm for 1.51 m2 to 25.2 mm
for 2.61 m2 of body surface area); however regurgitant aortic valves present on average larger
annulus especially in case of BAV (mean diameter 27 mm for tricuspid and 31 mm for BAV)
[16].
Echocardiography has historically been used as the main form of aortic root imaging.
However, computed tomographic (CT) scan has become an integral part of preoperative
workup of patients undergoing AVS operations. CT imaging can be valuable in evaluating
aortic diameters at the standard levels (annulus, sinuses, ST junction, tubular aorta); the
precise diameters should be obtained from parasagittal multi-planar reconstruction along the
centerline. Accurate measurements of aortic annulus are particularly important for managing
patients with aortic root aneurysms; the ability to generate arbitrary oriented (orthonormal)
images to augment the axial images is critical in assessing the size of the aortic annulus and
root since they are typically located oblique to standard axial slices. Despite it having been
considered a circular area, in vivo CT scan studies have accurately described the annulus
elliptical shape with a minor and major diameter [17]. In a recent CT scan study we showed
an elliptic annular shape in tricuspid aortic valve (TAV), a circular shape in type 0 BAV and
an intermediate behavior in type 1 BAV, suggesting a possible gradual spectrum of ellipticity.
In the postoperative phase after a reimplantation procedure these differences were eliminated,
suggesting an active role of the annuloplasty on the geometry of the aortic annulus [18]. The
continuation of this research, according to the classification for BAV as proposed by de
Kerchove et al. [15], showed a linear correlation between the commissural orientation and the
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shape of the aortic annulus. As the commissural orientation decreases towards an asymmetric
phenotype, the aortic annulus approaches a more elliptical shape [19]. Valve configuration
determines long-term results after BAV repair: orientation of the commissures (>160°) as a
naturally symmetrical BAV has superior results than an orientation of the commissures close
to 120° [20]. Bisecting and off-center cuts represent well identifiable lines, mainly used for
accurate CT measurements of the sinuses of Valsalva; measuring the annulus diameters using
the bisecting cut has been proven to be more accurate while off-center cuts result in diameters
significantly larger than those measured with the bisecting cut [21].
For many surgeons the direct measurement of the aortic annulus during surgery using an
Hegar probe is probably the most reliable, accurate and valid method compared to the various
diagnostic methods. However, sometimes, subtle dilatations are more difficult to recognize.
In such cases it is always important to consider the relationship with cusp size.
The TEE and the modern 3-D TEE allow for accurate morphologic and functional
evaluation of the aortic valve and aortic root complex with a good prediction of valve
reparability [22, 23]. The echocardiography assessment should focus on the geometry and/or
size of the components of the aortic root that influence the mechanism of opening and closing
of aortic valve. Key aspects to consider include measurements of the annulus, ST junction and
sinuses of Valsalva, evaluation for leaflet prolapse as well as visualization of jet origin and
direction. Schematically the jet of AR is central in type I AR (mainly due to dilatation of
various components of the skeleton of the root), is eccentric with a direction away from the
prolapsing cusp in type II AR, while in type III is eccentric but with a jet direction towards
the more restricted cusp. The number of cusps, their thickness, the appearance of the free
margins must be examined in multiple views. However, the final decision is mainly based on
intraoperatively evaluation of tissue quantity and quality and the presence of leaflet
calcifications. Generally, smooth and large leaflets with redundant tissue are considered as
more repairable than small, fibrous or thickened leaflets. In an echocardiographic
representation (mid-esophageal 120° view) of the aortic root the diameter of the ST junction,
in a normal healthy heart, is approximately 75% of the maximal sinus diameter, and is larger
than aortic annulus at the level of the VBR with a ratio of 1.3 [24]. A mismatch in this ratio
between the ST junction and the VBR (mostly 1.6 or more) is a frequent cause of secondary
AR with normal aortic cusps. Cusp geometry can also be evaluated by means of
echocardiography. Each cusp has a typical height between the central free margins and the
aortic insertion lines. This distance is called “effective height” and is an important
quantitative parameter of cusp configuration (Figure 3). The normal value of the effective
height is 9 to 10 mm and it can be determined by echocardiography as well as intraoperatively
with a caliper. Another important parameter to be evaluated is the “coaptation length” that is
the amount of leaflet tissue that is actually in contact during systole (Figure 3).
This length should be measured between the two cusps in BAV and between each of the
three cusps in TAV (Figure 4). Both effective height and coaptation length are two important
parameters in the postoperative evaluation of the results. After surgery the effective height of
all the leaflets should be should be 9 mm or more and the coaptation length at least 4 mm or
more. A shorter effective height and/or coaptation length have been proven a risk factor for
early and late residual aortic regurgitation [25, 26].
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Figure 3. Schematic representation of an aortic valve reimplantation with Valsalva graft showing the
eH, (the height difference between the central free margin and the aortic insertion lines), and the cL (the
amount of leaflet tissue used for coaptation) (eH: effective Height; cL: coaptation Length).
Figure 4. Use of caliper in TAV (A) and BAV (B) in order to measure the effective height (eH) of each
cusp. When eH is <9 mm leaflet plication is needed. (TAV: Tricuspid Aortic Valve; BAV: Bicuspid
Aortic Valve).
The History of Remodeling
The original remodeling technique was first reported in an abstract in 1983 but fully
reported with the first results in 1993 [2]. Briefly, the aneurysmal tissue of the sinuses of
Valsalva along with the ascending aortic wall is excised right at the annular attachment of the
cusps; the end-portion of a straight Dacron graft is tailored in the form of three tongues (by
excising three “triangles” to match the inter-leaflet triangles) and trimmed to match the shape
of the sinuses. Then, each Dacron “tongue” is properly fixed to the aortic annulus starting at
the nadir (deepest point) and suturing upwards until each commissure is fixed at the top of the
triangular part of the excised Dacron. In this way the remodeling technique reshape the ST
junction and at the same time creates 3 pseudo-sinuses of Valsalva with a very anatomical
reconstruction of the root [10, 11]. The intrinsic characteristics of the remodeling technique
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have made it appealing because it is quick, require only a single suture line, and it does not
need an extensive dissection and accurate mobilization of the aortic root. However, the long
external sutures between the Dacron tongues and the valve remnants have always been a
concern for the increased risk of bleeding and for the possibility of altering the proper
geometry of the aortic valve by tissue distortion. The technical key to success in the method
of remodeling is the careful prevention of bleeding by an accurate and precise suture line; to
prevent postoperative bleeding small variations of the original technique have been proposed.
In one of these techniques, a scalloped Dacron tube is placed inside the aortic root (“inclusion
technique) without the resection of the Valsalva sinuses [27]. Other subsequent modifications
were focused on creating custom made individualized reconstruction of three Dacron
“patches” for the sinuses of Valsalva (Robicsek-Thubrikar graft) [28, 29]; however these
techniques haven’t had a worldwide diffusion.
As we have seen, the importance of a root reconstruction relies on the re-establishment of
the right proportion between all root components. Unfortunately, the remodeling technique
failed to address the aortic annulus. A properly reduced and supported aortic annulus is
important in obtaining and maintaining a normal effective height, ensuring large leaflet
coaptation and preventing cusp stress Postoperative echocardiography years after the
operation have indeed shown that the lack of annular stabilization facilitates, in some patients,
the development of AR over the time with an incidence of reoperation varying between 10%
and 20% at 10 years [30-32]. For this reason, in the subsequent years the most important
modification of the remodeling technique was aimed to adding a annuloplasty or annular
stabilization to the classical remodeling technique [33-36].
The History of Reimplantation
In the classic reimplantation technique David proposed the “sparing” of the aortic valve
within a cylindrical Dacron graft placed over the entire aortic root structure, reducing both the
annulus and the ST junction diameters [3].
The Valsalva sinuses are resected a few millimeters above the aortic annulus and a series
of sutures are placed under the annulus at the same horizontal level passing for the nadirs of
each cusp without modifying the valve geometry (Figure 5). These sutures are passed through
the base of a straight Dacron prosthesis and tied to secure annulus inclusion and reduction.
Finally, the valve are reimplanted working from above, inside the conduit by polypropylene
running suture in the same manner as the sub-coronary method used to implant a stentless
bioprosthesis; in this way it is possible to obtain a complete support of the aortic wall with a
very much reduced risk of bleeding due to the internal sutures. A straight Dacron reestablishes a proper proportion between the annulus and the ST junction and therefore a good
geometrical condition for the aortic valve. These features are the starting point on the way to
obtaining a satisfactory and effective leaflet coaptation. The drawback of the classic
procedure is the elimination of the Valsalva sinuses that are important in regulating leaflets
motion [10, 11].
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Figure 5. A series of pledgeted U-stitches are passed inside out the left ventricular outflow tract along
the line of the virtual basal ring. Normally in tricuspid aortic valve 6 stitches are sufficient to complete
annular stabilization and to secure the proximal part of the graft (3 at the nadirs of the cusps and 3 at the
base on inter-leaflets triangles).
Although the valve can function well in the absence of sinuses, the presence of
recirculating vortices inside the sinuses is a guarantee for a smooth opening and closing of the
aortic valve during the cardiac cycle. The reduced leaflet stress is thought to be an important
issue for the aortic valve longevity. Since the appearance of the classical reimplantation,
many surgeons, including dr. David, proposed a series of technical variations in order to
overcome the absence of sinuses of Valsalva. The “David II” and “David III” were already
known as variations of the Yacoub’s remodeling procedure (II is exactly similar to
remodeling and the III is a remodeling with the addition of an external strip in the fibrous
portion of basal ring), and therefore variation of the reimplantation technique were labeled as
“David IV” (2001) and “David V” (2003). Both of them were progressive attempts to create
pseudo-sinuses by the use of a larger straight graft opportunely plicated. The “David IV” is
reimplantation with a graft size 4-mm bigger than usual with hand-made plications at the ST
junction; the “David V” uses an even larger graft size (6-8 mm bigger), which is “necked
down” both at the bottom and at the top ends to create graft pseudo-sinuses [37, 38].
Beginning in 2002, the Stanford group further simplified the David V procedure by using 2
separate grafts: a very large graft is used proximally to create large pseudo-sinuses of
Valsalva and facilitate suturing inside the graft and a smaller graft is used to reduce the ST
junction and replace the ascending portion of the aorta [39]. Other authors have described
innumerable individual modifications of the reimplantation. All these modifications focused
in the proximal part of Dacron conduit and tried to create a larger space” into which the
leaflets could open without contact of the cylindrical conduit. In 1995 Cochran by scalloping
the base of a cylindrical conduit increased the circumference of the cylinder. When this new
increased circumference was sewn to the “fixed” anatomic anulus, the cylindrical shape of the
conduit was somehow modified and the conduit would bulge outward at three locations
creating pseudosinuses. [40]. In the following years there was a general trend to use a larger
graft size than previously recommended [41]. Similarly, Takamoto et al. used a larger graft,
and narrowed the distal part of the graft by three longitudinal running sutures at three sites
reducing the original diameter and creating a neo-ST junction [42]. Other more complex and
less convincing techniques have also been described [43]. The Florida Sleeve technique was
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introduced to simplify the procedural complexity; this technique involves protecting the aortic
root with a Dacron “sleeve” while leaving native tissue in place and does not require coronary
artery reimplantation decreasing the risk of surgical bleeding [44].
For all types of reimplantation an adequate mobilization of the base of the aortic root to
place the bottom row of sutures in the sub-annular plane is mandatory and may require
skeletonization of the aortic annulus and the central fibrous body of the heart. This aspect
once again highlights the importance of a deep knowledge of the aortic root, the base of the
heart and the surrounding structures.
The Similarity of the Two Procedures after All Modifications… from
Remodeling to Reimplantation (the “Ring”)
When the aortic root disease is treated by an AVS procedure, achieving a precise
relationship among all the components of the aortic root and to restore near normal anatomy
and function is imperative and the materials used could contribute greatly. To overcome the
drawback of the remodeling technique, and to address the issue of annular dilatation several
types of annuloplasty have been devised. It was demonstrated that sub-commissural
annuloplasty (SCA) also known as Cabrol stitches are not appropriate in a large annulus
(>28-30 mm) because the annuloplasty effect disappears with time and is associated with a
high risk of AR recurrence both for BAVs and TAVs [45]. Furthermore, altering the shape of
the interleaflet triangle with the SCA alter the physiologic function of this important
component of the root. Ideal aortic annuloplasty should ensure good valve function, stability
of annular diameter reduction and ease to implant without interference with coronary arteries,
conduction system and leaflets mobility. The imperfect coincidence between the VAJ and
external limit of aortic root dissection is particularly relevant when considering an internal or
external annular fixation. The “internal” approach includes the use of strip of Dacron [33] or a
rigid Dacron-covered titanium ring [34]. Although the subvalvular plane (particularly in the
right coronary sinus) is easier to reach with internal rings, sub-aortic placement may interfere
with cusps mobility and increase potential risks of hemolytic or thromboembolic events. For
the “external” approach Lansac and coll. [35] has proposed a flexible ring positioned around
the annulus fixed by a series of subvalvular sutures (in a manner similar to that used for
reimplantation technique). Since 2009 Schäfers added, whenever the basal ring exceeds 26-27
mm a simple circular suture by braided polyester or PTFE [36]. This annulopasty consists of
a suture placed from outside the aortic wall, under the coronaries, at the level of the VBR in a
circumferential fashion and tighten around a Hegar dilator of an appropriate size (frequently
23 to 25 mm). This type of annuloplasty requires limited root dissection, shorter time to be
performed and is associated with equal outcomes in term of stability of the results and
freedom from reoperation. At this time, there is no evidence of the superiority of one
technique of implant over another; moreover, the optimal material for an annuloplasty ring is
still uncertain. In a recent porcine model study on the external approach for annuloplasty,
Dacron ring was similar to native aortic annulus than suture annuloplasty, offering a more a
physiological support [46]. Choice of material and future improvements of dedicated material
for the annuloplasty procedures remain a challenge for future studies.
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The Similarity of the Two Procedures after All Modifications…
from Reimplantation to Remodeling (the “Space”)
Traditionally the reimplantation procedures have been executed using a standard
cylindrical straight tubular grafts, and, as previously described, numerous technical
modifications have been added to reconstruct the anatomy of Valsalva’s sinuses. At the end
of the 90s, I imagined to modify a standard Dacron graft in order to create the shape of
Valsalva sinuses without major modifications in the original technique as described by T.
David in 1991. On February 14, 2000 our group have introduced into the clinical practice a
new pre-formed Dacron conduit designed specifically for aortic root replacement. This graft
is called the “Valsalva” graft (manufactured by Terumo Aortic, Renfrewshire, Scotland, UK)
for its ability, when pressurized, to create the pseudo-sinuses of Valsalva. The main
characteristic of the graft is a portion, called the skirt, with longitudinally directed pleats (at
90 degree with respect to the rest of the graft) that expand horizontally and, after aortic valve
reimplantation, reproduce the sinuses of Valsalva. The peculiar design of the graft allows for
proper root reconstruction by re-establishing the main FAA characteristics: two fixed rings
(annulus and ST junction) joined by three pillars (the commissures) dividing three
independent bulging sinuses [47]. The role of the Valsalva graft in AVS procedures is to
combine the peculiar advantages of remodeling and reimplantation simplifying and
standardizing the various steps of the operations. The theoretic arguments favoring polyester
fabric pseudosinuses include slower aortic cusp closing velocities, which reduce the diastolic
stresses on the cusps and thus potentially enhance valve durability [12]. The presence of
pseudo-sinuses in the Valsalva graft guarantees proper and physiological aortic leaflet motion
both during the opening and closing phase [8, 9, 48]. However, it is well known that the
dynamics of aortic leaflet is altered not only in the absence of sinuses but also when the aortic
wall is stiff (age, hypertension, atherosclerosis). Any Dacron graft is intrinsically stiffer than
the natural living aortic wall and for this reason it appears even more important to guarantee a
natural size and shape of neo-sinuses in order to best compensate for the loss of wall elasticity
[49]. The Valsalva graft with its peculiar characteristics of longitudinally directed pleats of
the graft allows a proper anatomical reconstruction in the size and shape of the sinuses
(Figures 6-9). Although there is evidence that the Valsalva graft maintain certain
distensibility at the level of the sinuses both in the short-term [9] and at medium-term [50] it
is evident that the elastic component will remain markedly reduced when compared to natural
aortic wall. More recently the Cornell International Consortium for Aortic Surgery (CICAS)
evaluated the flow dynamics in the aortic root after AVS procedures with Valsalva graft or
straight graft, by exploiting the capability of 4D Flow imaging to measure in vivo blood
velocity fields and 3D geometric flow patterns. These studies clearly demonstrated that the
recreation of the sinuses of Valsalva is associated with significantly lower wall shear stress
and organized vortical flows at the level of the sinus that are not evident using the straight
tube graft. Various and still unexplored knowledge can be obtained from the qualitative and
quantitative analysis of these complex datasets, that could shed more light on the various
surgical techniques and grafts adopted in AVS surgery [51-53].
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Figure 6. Postoperative sagittal CT scan view: Valsalva graft used in reimplantation procedure restores
a near normal anatomy achieving a precise relationship among all the components of the aortic root.
(CT: computed tomography).
Figure 7. Postoperative sagittal cine MRI view (MRI: Magnetic Resonance Imaging).
Figure 8. Postoperative cross sectional CT scan of a patient after a reimplantation procedure using the
Valsalva graft shows the trilobate aspect of the root with 3 independent sinuses. (CT: computed
tomography).
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Figure 9. Postoperative short-axis TEE after a reimplantation procedure using the Valsalva graft in a
patient with a TAV (TEE: Transesophageal Echocardiography; TAV: Tricuspid Aortic Valve).
These findings need confirmation in larger studies but are expected to have important
implications in predicting the aortic valve durability.
Moreover, from a surgical point of view, the use of this designed graft with a sinus-like
root portion can facilitate the suture of the coronary buttons during ostia reimplantation
reducing the stress in the circumferential direction after the aorta has been pressurized [54].
The advantages are particularly evident in the redo cases and calcified and rigid coronary
ostia. The initial hypothesis that the reduction of the stress on the coronary anastomoses may
decrease the incidence of postoperative complications such as bleeding and late pseudoaneurysm formation has been confirmed in our experience in nearly two decades of aortic
root surgery including AVS and Bentall procedures [55-57].
As regarding the use of other types of preformed anatomical grafts, a new vascular graft
(Cardioroot; Intervascular SAS, La Ciotat, France) has been also used for AVS operations in
a prospective, multicenter study with excellent results at 1-year follow-up [58]. Considering
the possibility of leaflet contact with the walls of a straight tube graft and the experimental
data on suboptimal leaflet function, one would expect a much higher rate of failure following
the original David procedure. In fact, despite re-creation of neosinuses in the aortic root is
certainly superior from an anatomical and functional point of view, the clinical superiority of
a graft with sinuses versus a cylindrical graft remains unproven. The long-term results of
reimplantation using the Valsalva graft show freedom from reoperation of 90.1% ± 4.3% at
13 years [54]. In centers with longest experience, midterm and long-term outcomes with
straight grafts for AVS operations are also excellent with freedom from reoperation on the
aortic valve at 18 years higher than 90% [59, 60]. It is evident that no Dacron conduit can
compensate for a suboptimal surgical performance or for patients selection both in the
remodeling or reimplantation. The complexity of AVS procedures requires enough
experience and several technical points, other than the choice of a graft, can significantly
affect the final result. As an example, the technique used to reimplant the valve inside the
Dacron conduit and/or the way the valve is geometrically repositioned inside the conduit, are
far more important for the long-term success of the operation. The use of a straight graft or a
pre-formed graft with sinuses, such as the Valsalva graft, is only a single factor and certainly
not the most important.
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