Tetralogy of Fallot with subarterial ventricular septal defect: Diagnosis and Surgical Considerations by Florentino J Vargas et al.

J
THORAC CARDIOVASC SURG
92:908-912, 1986
Tetralogy of Fallot with subarterial ventricular
septal defect
Diagnostic and surgical considerations
Since 1964, 77 patients underwent repair for tetralogy of FaUot with subarterial ventricular septal defect.
Median age at operation was 5 years. Cyanosis was commonly mild, and hypoxic episodes were
infrequent Accordingly, only 12 patients (15.58%) needed either palliative or corrective operations before
the age of 2 years. Characteristic angiographic and echocardiographic features were observed, which
aUowed this entity to be differentiated from either classic tetralogy or other types of double-outlet right
ventricle. The earliest series of operations (in which no right ventricular outflow patch was used) was
foUowed by a prohibitive mortality (50%). Residual subpulmonary obstruction was the cause of aU of
these deaths. In a second series of patients, a transannular patch was frequently used (79.59 %~ with the
rationale that closure of the ventricular septal defect would make restrictive the deficient infundibulum of
these patients. In a later series, we observed that most of the patients had a nonrestrictive pulmonary
anulus (80 %); the patch therefore was limited to the ventriculotomy. In the absence of pulmonary annular
hypoplasia, the need for patching of the right ventricular outflow tract in this entity has to be confined to
preventing the subpulmonary obstruction induced by closure of the ventricular septal defect. A
considerable improvement in the results foUowed our first series (4.3% mortality). FoUow-up of the
survivors (mean 7 years) has been satisfactory.
Florentino J. Vargas, M.D.,* Guillermo O. Kreutzer, M.D., Miguel Pedrini, M.D.,
Horacio Capelli, M.D., and Alberto Rodriguez Coronel, M.D., Buenos Aires, Argentina
A
variable degree of anterior deviation of the conal
septum, with narrowing of the right ventricular outflow
tract (RVOT) and a subaortic ventricular septal defect
(VSD), constitute distinguishing features in the anatomy of tetralogy of Fallot.!" However, if the conal
septum is absent or rudimentary, the result is a subarterially located VSD that is doubly committed to both
the aortic and pulmonary valve rings." This report
describes a 20 year experience in the surgical management of tetralogy of Fallot with subarterial VSD at
Children's Hospital of Buenos Aires. The characteristic
From the Unit of Cardiovascular Surgery and the Department of
Cardiology, Hospital de Ninos de Buenos Aires, Argentina.
Received for publication Nov. II, 1985.
Accepted for publication Dec. 12, 1985.
Address for reprints: Florentino J. Vargas, M.D., San Martin 1353,
1828 Banfield, Provincia ve Buenos Aires, Argentina.
*Recipient of the Evarts A. Graham Memorial Traveling Fellowship
(The American Association for Thoracic Surgery), Department of
Cardiovascular Surgery, Children's Hospital of Boston, Harvard
Medical School, Boston, Mass.
908
anatomic, echocardiographic, angiographic, and surgical features presented suggest the need for this entity to
be individualized within the spectrum of tetralogy, this
being of practical importance for the proper management of these patients.
Patients
Since 1964, 77 patients have undergone repair for
tetralogy of Fallot with subarterial VSD. This figure
represents 6.6% of the total number of tetralogies
(1,150) repaired during the same period at this institution. The definition of tetralogy of Fallot with subarterial VSD was based on the following criteria: (1) a large,
(nonrestrictive) subarterial VSD resulting in equalization of pressures between the right and left ventricles;
(2) the presence of both pulmonary and aortic valve
rings either in direct continuity (absent conal septum) or
separated by a thin band of fibrous tissue (hypoplastic
conal septum); (3) RVOT obstruction (infundibular)
with pulmonary arterial peak systolic pressure no greater than 35 mm Hg; and (4) presence of aortic-mitral
Volume 92
Number 5
November 1986
Tetralogy of Fallot
909
Fig. 1. Right ventriculogram. The contrast agent has been directed through a subarterial VSD toward the apex of
the left ventricle (arrow), filling out the left ventricular chamber before going into the aorta. The right ventricle (rv)
and the pulmonary artery (pa) have already been stained. The conal septum is absent.
continuity demonstrated either before or during the
operation. Excluded from the study were patients who
had pulmonary valve stenosis only or subvalvular stenosis of nontetralogy type. Ages ranged from 10 months to
12 years. Half of the patients were below the age of 5
years (median). Only seven patients (9.09%) were less
than 24 months of age at the time of repair. Five
patients (6.48%) had a systemic-pulmonary artery
shunt performed early in life because of severe hypoxemia. Associated lesions included absent pulmonary
valve (one patient), absent left main pulmonary artery
(one patient), anomalous origin of the left anterior
descending coronary artery from the right coronary
artery (one patient), and aortic regurgitation because of
a prolapsed coronary cusp (one patient).
Diagnostic considerations
The clinical profile in the natural history of these
patients was different from that observed in classic
tetralogy. These patients were only mildly cyanotic as a
group (mean hematocrit value was 39%, being 58% for
the whole group of tetralogy). Consequently, only 12
patients (15.58%) needed either a palliative or corrective
operation below the age of 2 years. Hypoxic spells were
recognized in only two patients. The absence of the
posterior wall of the RVOT would minimize annular
contraction of the infundibulum and could be a hypothetical rationale for this finding.
A characteristic angiographic pattern was displayed
in all cases by the absence of the typical subpulmonary
bulk usually afforded by the conal septum in classic
tetralogy. Although this can be demonstrated from
anteroposterior (either standard or hepatoclavicular)
projections," it is best displayed from the lateral views
(Fig. 1). The initial phase of the right ventriculogram
usually shows the contrast agent directed through the
subarterial VSD toward the apex of the left ventricle,
filling out the left ventricular chamber before going into
the aorta.' This finding was strikingly constant for the
patients in whom the conal septum was found to be
absent at operation (Fig. 1). In recent years, twodimensional echocardiography has become a helpful
adjunct in confirming the angiographic impression of
either absent or hypoplastic conal septum (short-axis
view at the cardiac base from the parasternal' and
subxiphoid" positions). Besidesdisplaying the narrowing
of the RVOT, it clearly demonstrates the doubly
committed position of the subarterial VSD to both the
aortic and pulmonary valve rings, with no conal tissue
interposed between them, unlike classic tetralogy. The
standard parasternal long-axisview demonstrates aorticmitral continuity.
Anatomic considerations (Figs. 2 and 3)
The morphology of the conal septum ranged from its
complete absence to a hypoplastic fibrous remnant
The Journal of
9 10 Vargas et al.
Fig. 2. Anatomic differences between classic tetralogy and
tetralogy of Fallot with subarterial YSD. A, Classic tetralogy
of Fallot: The conal septum (eS) is interposed between the
pulmonary valve (P) and the aorta. The tricuspid valve (TV) is
in close relationship with the posterior border of the defect.
Aortic-mitral continuity is present (white arrow). B. Tetralogy
of Fallot with subarterial YSD. The pulmonary (P) and aortic
valve rings are in continuity (black arrow) because of the
absence of the conal septum. The ventricular septal defect is
underneath both great arteries. Its posterior border is separated from the tricuspid anulus (TV) by septal muscle. This
should allow sutures to be placed in the border of the YSD (the
bundle of His being situated posterior and inferior to the crest
of the defect) Aortic-mitral continuity (white arrow).is also
present. SB. Septal band.
clearly different from the well-defined muscular structure found in classic tetralogy. The RVOT obstruction
was subvalvular (infundibular) in 34 cases (44.28%) and
combined subvalvular and valvular in the remaining.
The hypertrophied infundibulum was incomplete in its
posterior aspect because of the lack of a conal septum.
The septal band and the distal part of the parietal band
of the so-called crista supraventricularis were therefore
preserved and hypertrophic. The subarterial VSD was
always nonrestrictive, with its posterior border separated
from the tricuspid valve by interposed septal muscle.
The aortic cusps were easily seen through the defect,
regardless of the degree of aortic overriding. They were
separated from the pulmonary cusps either by the
fibrous junction of both valve rings or by a thin fibrous
remnant of the conal septum. The main pulmonary
artery and its branches were well developed and nonrestrictive in all but three (3.89%) cases.
Surgical considerations and results
All patients were operated on through a right ventriculotomy. In the first eight patients no RVOT patch was
Thoracic and Cardiovascular
Surgery
Fig. 3. Tetralogy of Fallot with subarterial YSD (intraoperative photograph). The pulmonary (P) and aortic (Aj valves
are in continuity, separated only by the fibrous junction of
both valve rings (arrow). The YSD is doubly committed to
them. VS. Yentricular septum.
considered necessary, because the infundibulum and
pulmonary artery anatomy were suitable (Table 1,series
1). The operation was followed by a surprisingly high
mortality (four deaths attributed to low cardiac output).
Necropsy revealed an obstructive RVOT in all of these
patients. As Neirotti and associates" reported at that
time, closure of the subarterial VSD in these patients
would make restrictive an otherwise apparently good
sized infundibular chamber. Subsequently, for the following 49 patients (Table I, series 2), a transannular
patch of the RVOT was employed almost routinely.The
need for avoiding the aforementioned mechanism of
residual RVOT obstruction had certainly exaggerated
the indication for transannular patching in this group.
We found later that a transannular patch was frequently
unnecessary, the need for patch enlargement being
confined to the ventriculotomy alone as it was performed in most of the patients of our last series (Table I,
series 3). In this third series, the incidence of nonrestrictive pulmonary anulus was 80%.
Because the aortic and pulmonary valve rings are in
continuity (Figs. 2 and 3), surgically induced aortic
regurgitation (resulting from distortion of the aortic
cusps by the suture of the subarterial VSD patch) is far
Volume 92
Number 5
November 1986
Tetralogy of Fallot
91 1
Table I. Evolution in the criteria for management of RVOT obstruction in tetralogy of Fallot with VSD (77
consecutive patients)
TAP
Series No.
No. of
patients
1
2
49
3
20
4
77
43
Total
No.
I
Vent. patch
%
No.
8
39
6
I
%
20
15
12.24
75
55.82
21
27.27
79.59
No RVOT patch
No.
8
4
1
13
I
Deaths
%
No.
100
8.16
4
2
50
4.08*
5
1
5t
16.88
7
9.09
%
r
Legend: TAP, transannular patch. Vent. patch, Patch limited to the ventriculotomy. No RVOT patch, No patch (infundibulectomy)
'Both deaths were associated with residual branch pulmonary obstruction (absent and hypoplastic left pulmonary artery, respectively, were present).
tUnknown cause of death.
more likely to occur than in classic tetralogy." The
injection of cardioplegic solution into the aortic root at
this point affords a proper distention of the aortic cusps
and individualizesthem from the line of fibrous tissue to
which the patch has to be attached.
After we realized the frequent need for patch enlargement of the RVOT (Table I, series 2 and 3) in these
patients, there were three deaths (4.3%), two of them
related to severe anatomic restriction of the pulmonary
artery and its branches (Table I). This result compares
favorably with the initial mortality (Table I, series I),
the overall mortality for the whole experience being
9.09%. When evaluating these results, one must consider
that most of these patients (96.11%) had a normal sized
pulmonary artery and branches, this feature being
characteristic for this entity' and responsible for an
excellent surgical prognosis. Age-related differences in
mortality were not observed. The follow-up of the
patients ranged from 7 months to 20 years (mean 7.5
years). All the survivors but three are in Functional
Class I of the New York Heart Association and are
enjoying a normal life. The exceptions are patients in
whom a residual VSD was detected; they are receiving
digitalis and diuretic therapy. One patient required
reoperation for an aneurysmal dilatation of a transannular patch.
Discussion
The peculiar profile of these patients with tetralogy,
characterized by a benign natural course, mild cyanosis,
and large pulmonary arteries, all associated with a
subarterial VSD, has been noted in the past. 3. 5, 7, 9, 11. 13
Anatomically, it would be difficult to classify this
subarterial VSD as of malaligned conal septum type in
its strict sense, because the septum is absent. The
question whether some of these cases could also be
referred to as doubly committed VSD type of doubleoulet right ventricle with pulmonary stenosis would be
academic. A differentiating diagnostic guideline in this
regard would be the presence of aortic-mitral continuity
as assessed by two-dimensional echocardiographic evaluation rather than the percentage of aortic commitment
with the right ventricle. However, the differential diagnosis of double-oulet right ventricle with subaortic VSD
and pulmonary stenosis has practical importance,
because it implies a different anatomy (a subaortic
conus being interposed between the aortic and pulmonary valve rings) with the technical implications thereof.
Although the angiographic pattern for tetralogy of
Fallot with subarterial VSD is usually characteristic,
this differential diagnosis can occasionally be difficult.7,9
The aforementioned early filling of the left ventricular
chamber from the right ventriculogram' should alert one
to the possibility of tetralogy of Fallot with subarterial
VSD. Again, two-dimensional echocardiography should
allow the two entities to be individualized by assessing
the morphology of the conal septum and aortic-mitral
continuity.?"
Although the aortic relationship of the subarterial
VSD could be comparable to the one that has been
described in association with aortic insufficiency in
patients without tetralogy," aortic regurgitation has
been a rare finding in this experience. In the patient in
whom it was observed, no additional aortic valve procedures were considered necessary; the aortic regurgitation
was assessed by injecting cardioplegic solution through
the subarterial VSD into the aortic root, and it was
found to be mild. This unexpectedly low incidence of
aortic regurgitation in tetralogy of Fallot with subarterial VSD has been reported previously." It is paradoxical,
because the aortic valve seems to be less supported from
below in the presence of aortic overriding," which would
favor a cusp-prolapsing mechanism. An attractive rationale for this has been proposed by Matsuda and
colleagues." Unlike tetralogy of Fallot with subarterial
VSD, in the isolated VSD described either as subarteri-
The Journal of
Thoracic and Cardiovascular
Surgery
9 I 2 Vargas et al.
al" or bulboventricular" by others, the blood flows from
the left ventricle to the right side of the heart, causing
distortion and herniation of the related aortic cusp.
When associated with tetralogy of Fallot, the degree of
regurgitation can be evaluated through the subarterial
VSD with ease, as mentioned earlier.
Although transannular patching was almost routinely
used after the surgical features of this entity were
initially recognized,7,9,11,12 we later found that these
patients had a nonrestrictive pulmonary ring more often
than was originally considered. Accordingly, we
observed that the incidence of transannular patching
decreased strikingly in our late experience, the patch
being limited only to the ventriculotomy in most
instances. In the presence of a normal pulmonary
anulus, an RVOT patch in this anomaly has to be
specificallydesigned to avoid the development of subpulmonary obstruction after closure of the subarterial
VSD.
6
7
8
9
10
II
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