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Aortic Root Involvement in Congenital Heart Defects
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point of classification while highlighting the importance of describing the borders to facilitate
better understanding [39].
Central perimembranous defects are usually adjacent to the area of fibrous continuity
between the septal leaflet of the tricuspid valve and the aortic valve, and they are located
below and behind the postero-inferior limb of the septal band.
Inlet defects open into the right ventricle (RV) inlet below the postero-inferior limb of the
septal band and the medial papillary muscle, whereas outlet defects open into the RV outlet
between the 2 limbs of the septal band. Inlet defects can be associated with malalignment of
the atrial septum and ventricular septum, typically with a straddling tricuspid valve.
In contrast, outlet defects are often associated with malalignment of the muscular or
fibrous outlet septum relative to the limbs of the septal band. The conduction pathway is
located along the postero-inferior border of all perimembranous defects and juxta-arterial
defects with a fibrous postero-inferior rim.
Trabecular muscular defects are embedded within the apical muscular ventricular septum
and can occupy any of its geographic components.
All VSDs can occur in isolation, as confluent combinations of two or more types, or as
integral components of other CHDs. Early diagnosis for such defect using echocardiography
is routine, even in early fetal life. With exact fetal diagnosis, it will almost certainly prove
possible to identify those defects that are the most likely to close, as opposed to those which
will require interventional or surgical treatment. For those requiring treatment, use of
anatomic information permits an accurate assessment of any individual defect relative to the
atrioventricular conduction axis without fear of inducing atrioventricular block. Thus, proper
diagnosis, particularly of the doubly committed defect, should now be the prelude to timely
successful management, and hopefully a normal post-interventional or postoperative outcome
[40].
A subset of patients with VSDs will develop aortic insufficiency (AI). These VSDs may
be located in the subarterial (also referred to as supracristal, subpulmonary, doubly committed
subarterial, conal septal, or infundibular position), perimembranous (also referred to as
subcristal, conotruncal, or paramembranous position), or outlet muscular positions [41].
AI complicates doubly committed subarterial VSDs about five times more often than
perimembranous VSDs [42]. Several mechanisms may be responsible for the development of
AI: lack of structural support and forces for leaflets adjacent to the VSD, abnormal
commissural suspension, loss of continuity between the aortic media and aortic annulus but
the Venturi effect is the predominant pathogenetic factor in the development of AI associated
with a VSD. Surgical management of this VSDs should be based on knowledge of its
anatomic features, natural history and the incidence of aortic valvar prolapse (AVP) and AI.
Epidemiology
Outlet type VSDs include doubly committed juxta-arterial, perimembranous outlet type,
and muscular outlet type. Doubly committed juxta-arterial VSDs account for approximately
5-7% of VSDs in the Western Hemisphere. In the Eastern Hemisphere, although the overall
incidence of VSDs is no greater in Asians than in other groups, doubly committed VSDs
account for approximately 30% of VSDs in Asians. This type is paramount importance
because accounts for approximately one-quarter of all VSDs cases requiring surgical closure.
Higher occurrence of the condition in this population has not been adequately explained,
but one may assume that it is genetically determined [43].
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The association of juxta-arterial type VSD with aortic valve prolapse, mainly right
coronary cusp prolapse, and aortic regurgitation (AR) has been defined. According to
previous reports, the incidence of AVP in juxta-arterial VSD was 36% to 79% [44]. The peak
age for AVP was around 7 years, and that for AR was between 5 and 10 years [45]. In
contrast, study about AVP and AR in perimembranous outlet and muscular outlet VSDs is
limited.
Methods
Etiology, Pathophysiology and Clinical Description
In 1921, Laubry and Pezzi were the first to report the valvular complications of the aortic
valve and aortic regurgitation in VSDs.
Van Praagh and McNamara’s report [46], based on morphological findings of autopsied
heart specimens, and additional data resulting from the study of a ruptured aneurysm of the
sinus of Valsalva allowed to describe the major factors that contribute to AVP and AI into the
VSDs.
Two major, conceptually distinct but functionally interdependent factors contribute to the
AVP and AI into the VSD: anatomical factor and hemodynamic factor.
Anatomical Factor
Aortic valve regurgitation complicates the course of patients with subarterial VSDs five
times as often as it does patients with perimembranous VSDs. The fundamental
hemodynamic forces at work seem to be similar between the two types of VSDs, and
therefore other anatomic factors must be modifying the development of AI.
For example in the doubly committed subarterial VSDs, the crucial phenotypic feature of
this defect is the altered morphology of the arterial trunks with respect to the normally
structured heart. This defect can only exist in absence of the “septal” component of the freestanding infundibular sleeve which normally supports the pulmonary trunk, a trait seen in
hearts with common arterial trunk. It is no coincidence, therefore, that both these lesions are
found in the setting of 22q11 deletion, pointing to their similar genetic background which
itself is more prevalent in far Eastern populations [47].
In the normal heart, the pulmonary root is lifted away from the base of the heart by the
free-standing infundibulum. In consequence of the deficient infundibulum, there is a fibrous
continuity between the leaflets of the aortic and pulmonary valves, with the defect not only
committed to the aorta, but also to the pulmonary trunk, hence its doubly committed
phenotype (Figure 15). Owing to the lack of anatomical muscular support provided by the
subpulmonary infundibulum, the right coronary leaflet, and occasionally the non-coronary
leaflet of the aortic valve tend to prolapse through the defect.
Aortic Root Involvement in Congenital Heart Defects
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Figure 15. Reprinted from Devlin et al. Ann Thorac Surg 2014; 97:2134–41 [52].
Aortic insufficiency can be partially explained by a lack of infundibular conal septal
support from below.
Most large perimembranous defects are closely related to the aortic valve and very few
are associated with aortic valve prolapse with or without incompetence. There is probably an
intrinsic structural abnormality of the aortic valve that, in addition to the VSD, predisposes
one or more cusps to progressively prolapse. Yacoub and associates postulated that this basic
structural abnormality is a progressive discontinuity between the aortic valve annulus and the
aortic media [48]. There is no pathologic data to support this theory and it's difficult to
determine if this was the result of progressive cusp deformity or the cause of cusp prolapse.
Two additional factors, drag forces and the differences in anatomy between subarterial and
perimembranous VSDs, may play a role in the development of AI. The superior border of the
subarterial VSD is adjacent to the hinge point of right coronary cusp and the VSD has a
shallow, half-moon shape. As a result, the jet of blood through the defect is maximally
exposed to the right coronary cusp. In contrast, perimembranous VSDs have a more circular
shape and appear to need additional anatomic conditions such as override of the non-coronary
cusp for the development of AI [49].
Abnormal commissural structures have been observed in some cases of AI associated
with a VSD. The partial fusion of the commissures, resulting in a bicuspid aortic valve,
contributes to the development of AI when present, but is not a satisfactory explanation for
most cases. A lack of special forces has been implicated as a cause of AI in this group of
patients. With the progressive deformity of the cusp, a point is reached where the appropriate
surfaces of the opposite cusps cannot meet. This is the beginning of AI [50].
Hemodynamic Factor
Proposed mechanisms leading to AI in patients with a VSDs include several mechanisms
but a review of literature [51, 52] suggest that hemodynamic factors also probably aggravate
the tendencies toward the development of AI. These effects are present throughout the entire
cardiac cycle and depend on the Venturi effect.
The Venturi effect explains the pathogenesis of aortic valve prolapse and AI in a subset
of patients with a VSD. Giovanni Venturi, a professor of physics, expanded on Bernoulli’s
observation that as the velocity of a fluid increases a low-pressure zone is created. As a fluid
passes through conduits of varying diameter, changes in velocity and pressure will occur, so
that as the caliber of the conduit decreases, the fluid velocity will increase and the pressure
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will decrease. This low-pressure zone within a restrictive VSD can impact the adjacent cusp
of the aortic valve.
One way to gauge the size of a VSD is by the velocity of blood flow through it and this is
in part a function of the size of the VSD relative to the aortic root. If there is restriction to
flow through the VSD and an aortic valve cusp is adjacent to the defect then the increase in
velocity of blood through the defect could adversely affect the adjacent cusp.
A Venturi effect is created by the left-to-right shunting through the VSD during early
systole. This turbulent flow tends to displace the aortic cusp, especially unsupported right
coronary leaflet, into the right ventricle (Figure 16A). Later in systole the aortic cusp
prolapses into the VSD and is acted on by direct pressure from the cavity of the left ventricle
(Figure 16C), which tends to displace both the cusp and the anulus further into the right
ventricle (Figure 16E). During diastole the high pressure in the aortic root distends the dilated
sinus with further displacement of the aortic anulus toward the right ventricle (Figure 16B).
The intra-aortic pressure forces the aortic valvar leaflet to close, but the unsupported
prolapsed leaflet is pushed down into the VSD, away from the opposed coronary leaflet,
resulting eventually in AI (Figure 16D-F). The increasing aortic regurgitation and the existing
left-to-right shunt cause left ventricular volume overload, which could cause potentially
irreversible changes in the left ventricular wall structure and function.
This mechanism was proposed by Tatsuno et al. [53] in 1973 and hypothesizing that the
Venturi effect is the mechanism that results in AI, the VSD must be restrictive: smaller the
defect is, higher will be the gradient across it and it will cause the blood to shunt across more
vigorously thus drawing the nearby cusp in it and causing it to prolapse and then the AI.
Figure 16. Reprinted from Tweddell et al. [51].
Aortic Root Involvement in Congenital Heart Defects
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VSD is commonly diagnosed in the neonatal period, but neither AVP nor AI are present
at birth. The physiological triggering factors act after birth due to the decrease in pulmonary
vascular resistance which therefore results in a high-velocity jet across the VSD and AVP
precedes the development of AI [54].
The observations supporting these points are that VSDs associated with AI are restrictive
is the older age of the patients undergoing surgery for VSD/AI, between 5 and 10 years of age
[55]. Chiu et al. from the National Taiwan University, reported a series of 677 patients with
subarterial, perimembranous, and outlet muscular VSDs with AVP. There was no difference
in the Qp/Qs associated with AVP among the three types and the average Qp/Qs among 373
patients who developed AVP was about 1.62 and pulmonary artery pressures are at most only
mildly elevated. A review of the literature indicates that for patients with VSD and AI the
VSD is restrictive with a Qp/Qs 2 and an absence of pulmonary artery hypertension depends
on the Venturi effect as the predominate mechanism for the development of AI associated
with a VSD [51].
Diagnosis
Congestive heart failure does not occur in patients with an isolated, small VSD. General
examination findings consist of a long harsh systolic murmur and no signs of respiratory
distress or growth failure. Second heart sound findings depend on volume of shunt flow as
well as pulmonary artery pressure and resistance.
Physical examination should focus on whether AI is present. Blood pressure must be
carefully evaluated for pulse pressure (ie, the difference between systolic and diastolic blood
pressures) and pulse amplitude, as these increase with increasing AI unless heart failure also
occurs. Significant AI may cause a late diastolic murmur at the apex resulting from atrial
contraction augmenting late ventricular filling. This is the Austin Flint murmur.
Chest radiography is normal in infancy if the left-to-right shunt is small. Radiography in
the older child or adult with progressive AI may reveal left heart enlargement and prominence
of the ascending aorta. Shunt volume is generally smaller, thus pulmonary arterial vascularity
is generally normal.
Although the diagnosis is usually made by the presence of a diastolic murmur in a patient
known to have a VSD, recent refinement in echocardiographic techniques allows accurate
recognition and quantification of the various components of the AVP and AI.
The position, presence and size of the defects were determined by echocardiography,
with careful attention to distinguish the truly doubly committed VSDs from perimembranous
defects with outlet extension, using meticulous echocardiographic observation of the shortaxis view of the right ventricular outflow tract at the level of the aortic root. The size of the
defect was graded as being small, moderate or large in relation to the dimensions of the aortic
valvar orifice, using values of less than 25%, between 25 and 50% or greater than 50%,
respectively. When measuring the size of the defect, no account was taken of any portion
occluded by a prolapsing leaflet of the aortic valve.
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Figure 17. Reprinted from Evdokia Petropoulou, Stergios Theodoropoulos, and Magdi H. Yacoub [57].
The diagnosis of AVP and AI was made according to the echocardiographic findings that
were confirmed by angiographic or surgical findings. AI was diagnosed by two-dimensional
and color doppler echo in parasternal long-axis view and was graded as absent, mild (AR jet
reaching just beneath the aortic valve), moderate (AR jet reaching beyond the anterior cusp of
the mitral valve but not reaching the left ventricular apex), or severe (AR jet reaching the left
ventricular apex) [56].
Three-dimensional (17D) echocardiographic imaging of VSDs closely correlates with
surgical findings.
Figure 3A shows the discontinuity between the aortic media and the crest of the septum,
the dilatation of the sinus of Valsalva and the prolapse of the cusp. This was associated with
moderate AI with a jet towards the anterior mitral leaflet (Figure 17C). During systole the
VSD shunt was visible (Figure 17E), while in diastole the prolapsing cusp obstructed the
VSD (Figure 3C). After surgical correction (Figure 3B) AI was trivial (Figure 17D) and there
were no shunts during systole (Figure 17F) or diastole (Figure 17D) [57].
Advances in prenatal diagnosis could also now permit anticipation of the diagnosis and
allow for a better follow-up, with more appropriate timing for closure of the defect.
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Surgical Management
Heart failure, a large shunt, poor growth, or elevated pulmonary artery pressure would all
be indications for VSD closure regardless of presence of AI. Development of AI may occurs
even in the absence of congestive heart failure and the indications of surgery become more
complicated. The primary indications for closure of these defects, therefore, are AVP and AI.
Secondary indications include the degree of left-to-right shunting, and the known potential for
AVP.
Closure of the VSD, with or without aortic valve repair, is indicated for both
perimembranous and subarterial VSDs when more than trivial AI is identified because AI is
progressive [58].
For patients with a subarterial VSD and AVP, VSD closure is indicated because of the
high likelihood of progression of AVP and development of AI, furthermore spontaneous
closure is difficult. Lun et al. [59] suggested that all subarterial VSDs of 5 mm should be
closed regardless of the presence of AVP to prevent the development of AI.
For the patient with a hemodynamically insignificant perimembranous VSD with AVP
but without AI, indications for surgery are less clear. Progression of AI is variable but the
closure of the VSD reduces the risk for AVP even if the surgical closure for perimembranous
VSDs places the conduction system at risk. Therefore, in the absence of AI, prophylactic
closure of restrictive perimembranous VSDs with AVP is probably not justified [53].
Elgamal et al. recommend closure of VSDs, regardless of the type, the size, or the
apparent absence of AVP, when any degree of AI is identified [58]. Of the various repair
techniques existing they perform in a Trusler's aortic valve repair where the excess lenght of
the prolapsed aoric valve cusp is plicated against the aortic wall using a horizontal suture
reinforced with a Teflon or pericardial pledgets. The adequacy of the initial repair is the
determinant of long-term results: the excessive elongation and prolapse of the aortic valve
need more plication sutures and valvuloplasty failure may occur. Okita and colleagues
confirmed, in their multivariate analysis, that the number of plication sutures represent an
independent risk factor for valve repair [60].
Surgical closure, with or without simultaneous repair of the aortic valve, is still
considered the gold standard for the treatment of this congenital heart defect [53]. The
approach through a right atriotomy, does not always allow for adequate exposure of the upper
part of the doubly committed VSDs. This means that either a longitudinal right
ventriculotomy, or a longitudinal incision in the pulmonary trunk, or an oblique incision of
the ascending aorta, will likely be needed, with the last approach also allowing direct repair of
the aortic valve [61]. It is very important to repair the defect with a patch that realigns the
ventricular septum and provides support for the leaflets of the aortic valve, possibly avoiding
further surgery.
Figure 18A shows the typical operative view of the doubly committed VSD through the
opened pulmonary trunk. After cross-clamping the aorta, and delivering cold blood
cardioplegic solution, we placed interrupted pledgeted supported sutures around the defect. A
critical part of the process of closure involves placing sutures directly in the base of the
pulmonary valvar leaflets as an anchoring point where there is no muscular septum separating
the aortic and pulmonary valves, as shown in Figure 18B. All defects were closed with a
round polytetrafluoroethylene patch, which supports the leaflets of the aortic valve.
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Some studies have observed that once AI develops, it will progress even after closure of
VSD. It may end up in need of aortic valve replacement. Chauvaud [62] observed 16% need
of aortic valve replacement even after VSD closure. Other studies [63] found closure of VSD
or aortic valve repair will halt the process of further damage to aortic valve.
The optimal timing for surgical treatment remains controversial. The closure of the
defect, with or without repair of the aortic valve, should be performed at the first appearance
of, or if there is progression of previously observed trivial AI [64]. The seeming presence of a
‘functionally’ restrictive defect on echocardiography, with most of the area of the
morphologically large defect closed by the prolapsing aortic valve leaflet, can be misleading
and can cause a dangerous delay in referral for treatment. The relatively low risk of
cardiopulmonary bypass needs to overcome the benefits of preventing aortic valve
complications.
Figure 18A. Figure 18B. Reprinted from Devlin et al. [52].
A distinct relationship has been shown between the age of the patients and the
development of AVP [15]. In a series of 209 patients with doubly committed and juxtaarterial
VSD, 100% of patients had aortic valve prolapse by age 15 years, the mean age of onset of
aortic valve prolapse was 4.9 years [65]. In a series of 395 patients with doubly committed
juxtaarterial VSD, half had AI by the age of 8 and almost nine tenths by the age of 20 [66].
Aneurysm of the sinus of Valsalva was not found before the age of 10 years, but began to
develop during the second decade of life, and was diagnosed most frequently in the third
decade of life.
Discussion
Outcome and Perspectives
Early detection of these type of VSDs and early accurate assessment of anatomical
morphology of aortic valve are crucial to prevent further progression of the disease.
Optimal operation timing may be important to achieve better outcomes after repair and
prevent the development of aortic valve complications.
Patch closure remains the gold standard in managing these defects. The morbidity and
mortality associated with VSD closure even combined with aortic valvuloplasty is low. Okita
and colleagues reported a hospital mortality of 1.6% with no late deaths, resulting in a 15-
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year actuarial survival of 98.3% [23]. Trusler and associates experienced no hospital deaths
with two late deaths, yielding a 10-year actuarial survival of 96% [67]. Elgamal et al. reported
15-year actuarial freedom from repair failure of 81% compares favorably with other
published series, where estimates range from 85% at 10 years to 64% at 15 years [58].
Rhodes and colleagues reported an 18-year freedom from reoperation of 51% [68].
Jung et al. observed that AI progression occurred in only one of our patients after VSD
closure, which was unexpectedly low (0.98%). Moreover, 95.1% (98 patients) of the patients
had less than faint degree AI in preoperative echo, showing an unexpectedly low prevalence
of preoperative AI in subarterial VSD patients who underwent surgical closure. Only the
patients with aortic valve abnormalities or delayed operation had AI progression or persisting
more than mild degree AI [69].
In summary, patients with a doubly committed VSD and AVP should undergo surgery to
prevent the development of AI because this complicates about half of subarterial VSDs with
AVP and spontaneous closure is rare. Patients with perimembranous VSDs with AVP should
be followed with serial echocardiography and undergo VSD closure if more than trivial AI
develops [51].
AORTICO-LEFT VENTRICULAR TUNNEL (ALVT)
Duccio Federici
Introduction
Description and Anatomical Considerations
The aortico-left ventricular tunnel, firstly described by Levy et al. in 1963 [70], is a rare
congenital malformation characterized by a paravalvular communication between the
ascending aorta and the left ventricle. It’s incidence is estimated around 1 in 1000 infants
born with congenital heart disease [71]. Associated defects, usually involving the proximal
coronary arteries, or the aortic or pulmonary valves, are present in nearly half of the cases.
The aortic-left ventricular tunnel typically originates from an aortic orifice cephalad to
the right coronary artery, at the level or just above the sino-tubular junction. In rare cases the
tunnel may originate above the left coronary artery or may open into the right ventricle. The
tunnel follows a descending route along the aorto-pulmonary interspace entering just below
the left-right commissure of the aortic valve. A buldge is typically visible along the
anterolateral aspect of the ascending aorta and represents the anterior wall of the tunnel. The
posterior wall is constituted by the true aortic wall and the tunnel’s floor usually involves the
muscle of the right ventricular outflow tract [72].
ALVT is classified into four types (Figure 19) according to Hovaguimian
classification [73]:
Type I: Slit-like aortic orifice without valvular distorsion
Type II: Oval-shaped aortic orifice with aneurysmal extracardiac component
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Type III: Oval aortic orifice with aneurismal intracardiac component
Type IV: Combination of type II and III
Figure 19. For types of aortic-left ventricular tunnel. LV (left ventricle); RV (right ventricle); RVOT
(right ventricular outflow tract); RCA (right coronary artery); MV (mitral valve): LA (left atrium).
Reprinted from Kim RW et al. [74].
In addition to the aforementioned classification, Ho et al. [71] suggested that the tunnels
never cross the interventricular septum but travel downsward into the fibrofatty plane
between the aortic root and the subpulmonary infundibulum, entering in the left ventricular
outflow tract immediately above the aortic-ventricular junction in the subcomimsural triangle
of the left and right valvular cups [74] (Figure 20).
Figure 20. Schematic representation of the most common type of aorto-vetricular tunnel. Note its
course along the fibrofatty plane between aortic root and subpulmonary infundibulum. Reprinted from
Mckay R. [90].
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