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Tetralogy of Fallot and pulmonary stenosis with intact interventricular septum
The American Volume
Journal
21
JUNE
Symposium
with
Heart
of Fallot Intact
Anatomic SIMON Mu~~oz-ARMAS,
1968
M.D.,?
6
TORO,
M.D., DEMETRIO
V. DE LA CRUZ, City,
DIFFERENTIAL electrocardiographic diagnosis between pulmonary stenosis with intact interventricular septum plus patent foramen ovale or atria1 septal defect (trilogy of Fallot) and pulmonary stenosis with associated interventricular septal defect and dextroposition of the aorta (tetralogy of Fallot) is sometimes This fact has prompted us to establish difficult. the electrocardiographic similarities and differences between these two malformations in the light of the ventricular activation process and the anatomic findings. This study includes the anatomic analysis of 50 autopsy specimens; in 39 of these cases electrocardiographic tracings were available.
II
Stenosis
Septum
and Electrocardiographic ANGEL DEL
Part
and Pulmonary
Mexico
Study*
SODI-PALLARES,
M.D., F.A.c’.c.
and
M.D.
Mexico
Mexico were studied. Of these, 39 cases were diagnosed as tetralogy of Fallot in view of the following features: (1) pulmonary stenosis of various degrees or atresia of the pulmonary artery; (2) middle basal interventricular septal defect,’ i.e., a defect lying in the membranous portion of the interventricular septum; (3) dextroposition of the aorta; and (4) right ventricular hypertrophy.2-4 Embryologically this malformation results from an unequal partition of the truncoconus at the expense of the pulmonary artery, with or without dextroposition of the truncoconus.2J Of the 39 cases of true tetralogy of Fallot, 34 were of the common type, with valvular and infundibular stenosis of the pulmonary artery; in 5 there was atresia of the pulmonary artery, that is. they belonged to the group which some authors designate pseudotruncus arteriosus. In the 2 remaining specimens, the malformation was more complex: the pulmonary valvular ring was quite narrow and there was agenesis of the pulmonary sigmoid valve cusps which caused pulmonary regurgitation. There was also a middle basal ventricular septal defect.’
HE
MATERIAL
Disease.
Interventricular
MARIA
T
Number
on Electrocardiography
in Congenital Tetralogy
of Cardiology
AND METHOD
Forty-one specimens of pulmonary stenosis plus ventricular septal defect from the Museum of Embryology of the Instituto National de Cardiologia de
* From the Departments of Electrocardiography and Embryology, Instituto National de Cardiologia de Mtxico, Mexico City, Mexico. Simbn Mufioz-Armas, M.D., Hospital Universitario de Caracas, Det Present address and address for reprints: partamento de Cardiologia, Ciudad Universitaria, Caracas, Venezuela. 773
Mufioz-Armas
774
Nine specimens with pulmonary valvular stenosis! intact interventricular septum and an atria1 septal defect or a patent foramen ovale were also studied. This malformation is termed trilogy of Fallot by some workers.3 This report will emphasize those anatomic details that may be of importance in the genesis of the electrical forces of the heart, such as the thicknessof the ventricular walls, the site of predominant hypertrophy, the position of the heart and the degree of rotation along its different axes. Special attention is given to the position of the interventricular septum and its spatial relations on the frontal plane. ANATOMIC I.
TRUE
TETRALOGY
et al. Its upper third of the right border of the heart. diameter varied according to the size of the heart and measured an average of approximately In all cases the upper limit of the hyper3 cm. trophic area was close to the right atrioventricuThis was the region lar groove (Fig. 1 and 2). of greatest thickness of the right ventricle, since the mean thickness of the free ventricular wall which corresponded to the center of the hypertrophic hemisphere was 15.3 mm.
FINDINGS
OF FALLOT
This group consisted of 39 specimens which were divided into two subgroups based on the presence or absence of pulmonary atresia. A.
Typical Tetralogy of Fallot (34 Cases)
This subgroup was characterized by the presence of both infundibular and valvular pulmonary stenosis. In the majority of cases, infundibular stenosis was more marked than valvular stenosis. The infundibulum was typically narrow and distorted, and it varied in length The from a few millimeters to normal length. crista supraventricularis was either normal in thickness or thin ; it was never hypertrophic. As a rule it exhibited some fibrosis, and in 1 case was represented by a very thin fibrous band, 1 mm. thick, and had no muscular component. In every case, the ventricular septal defect was of the middle basal type, that is, it was located at the level of the membranous portion of the septum behind the crista supraventricularis.l,G Aortic dextroposition was of various degrees. In most cases there was a 50 per cent or greater There was no correlaoverriding of the vessel. tion between the degree of aortic dextroposition and the degree of pulmonary stenosis. Right Ventricle: The right ventricle occupied externally the greater part of the anterior aspect of the heart, or between two thirds and the entire extent of this aspect. In the majority of the cases (53 per cent), the right ventricle comprised three fourths of the anterior aspect of the heart. In tetralogy of Fallot Predominant hypertrophy. one does not find a homogeneous and generalized hypertrophy. In our specimens hypertrophy was limited to one area of the free wall of the right ventricle. This area was hemispheric in shape, and its center was located approximately at the union of the middle third with the
Figure
1. i&gram showing the location of the area of maximal h.vpertrophy,which is a hemispheric area lying in the upper third of the right border of the heart in
cases of tetralogy spheric zone; RV Ao = overriding artery.
of Fallot. C = hypertrophic hemi= right ventricle; LV = left ventricle; aorta; PA = hypoplastic pulmonary
Thickness of the walls (Table I). The area of greatest thickness outside the hypertrophic hemisphere was seen in the basal portions of the posterior border of the right ventricle.* In this By conarea the mean thickness was 9 mm. trast, the average thickness of the thin anterior wall of the infundibulum (Fig. 2), was 4.86 mm., a value quite similar to the average thickness of the apical portion of the same anterior wall In other areas of the right ventricle (4.88 mm.) * The posterior border of the right ventricle is that section which is parallel and adjacent to the posterior intwventricular coronary artery, to the right of the interventricular septum. THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Tetralogy
vs. Trilogy
the values obtained were halfway between those mentioned. Crista supraventricularis. The parietal bundle of the crista supraventricularis was normal or In some inthin in the majority of the cases. stances it was fibrous; the mean thickness was 5.5 mm., which is within the average normal value for similar age groups.’ Left Ventricle: The left ventricle was always normal or hypotrophic. The average thickness
775
of Fallot
the angle formed by the interventricular septum and the frontal plane tended to diminish owing to the forward displacement of the right ventricle and the backward and leftward displacement of In only 2 cases was the interthe left ventricle. ventricular septum nearly parallel to the frontal plane. B. Tetralogy of Fallot with Pulmonary Atresia (5 Cases) This group was characterized by atresia of the pulmonary valve with or without aplasia of the infundibulum. The trunk of the pulmonary artery was extremely hypoplastic and exhibited branches of variable size. The parietal branch of the crista supraventricularis was displaced considerably forward and to the left; it fused with the anterior infundibular wall and occluded the infundibular channel, thus constituting a muscular mass placed anteriorly. Its mean thickness was 13.5 mm. The remaining anatomic characteristics were not different from those of the average case of tetralogy of Fallot (Fig. 3). The predominant hypertrophy was located at the same region as in the previous group, in a hemisphere-like area with a mean thickness of 14.5 mm. II.
2. Anatomic spe&nen of (I tare of tetralogy of Fallot. The right ventricle is open. Observe that hypertrophy predominates in the posterobasal portion (pb) in an area the shape of a hemisphere whose thickness (15 mm.) is three times greater than that of the anterior infundibular wall (ai) (5 mm.). c = crista supraventricularis, of normal thickness; Ao = aorta, showing marked dextroposition, arising almost entirely from the right ventricle. The stylus is crossing the very narrow pulmonary valvular orifice. To the left and behind the crista supraventricularis can be seen the ventricular septal defect, over which lies the overriding aorta.
Figure
of the ventricular wall was equal for the anterior and posterior borders,* with a mean value of 8 mm. Relation of the Interventricular Septum to the Frontal Plane: The interventricular septum tended to be parallel to the frontal plane, that is, * The anterior border of the left ventricle is that given by a section which is parallel and adjacent to the anterior descending artery, to the left of the interventricular septum. The posterior border is that determined by a section parallel and adjacent to the posterior interventricular coronary artery, to the left of the septum. VOLUME 21, JUNE 1968
STENOSIS
INTACT SEPTAL (TRILOGY
OF THE PULMONARY
INTERVENTRICULAR DEFECT
OR
OF FALLOT)
PATENT
(9
ARTERY
SEPTUM
WITH
AND
ATRIAL
FORAMEN
OVALE
CASES)
This group was characterized by the presence of pulmonary valvular stenosis. The pulmonary sigmoid valve cusps were thickened and fused at their commissures; in the majority of instances they formed a funnel-shaped structure, the vertex of which protruded into the lumen of the pulmonary artery. The hypertrophy of the infundibular walls reduced the cavity of the infundibulum by variable degrees. In 6 cases the foramen ovale was patent, and in 3 there was a true atria1 septal defect in the region of the fossa ovalis. Right Ventricle: In the majority of instances (7 cases) the right ventricle occupied the anterior two thirds of the heart. In 2 cases it formed the entire anterior aspect of the heart. Predominant hypertrophy. In contrast to the findings in tetralogy of Fallot, hypertrophy of the right ventricular walls was diffuse and generalized, involving both the posterior and basal portions as well as the anterior wall of the right ventricle (Fig. 4).
Muiioz-Armas
776
et al.
TABLE I Mean
Value
(mm.)
-~~~~~~ No. of .\natomic Specimens Fallot’s tetralogy Fallot’s trilogy
of the Thickness ~~~~
Hypertrophic Hemisphere
35
15.30
9
14.30
of the Free ~~Right
Posterobasal Border ‘1 00 10.40
Ventricular
Ventricle .\nteroapical Border
Walls
~_~~~_._ Anterior Infundibular Border
4.88
4.68
9.00
9.00
(44 ._-.
Cases) ~~ ~_
Crista Supraventricularis 5.5 10
Left Ventricle Posterior Anterior Border Border 8
3
8.7
8 11
Figure
3. Anatomic specimen of a case of trtralogy of F&lot with atresia of the pulmonary artery (pseudotruncus arteriosus). The right ventricle is open revealing its various structures. Hypertrophy is predominant in the posterior basal (pb) area (12 mm. in thickness). The anterior infundibular wall (ai) is of normal thickness Observe that the pulmonary artery valve is (4 mm.). atretic. Ao = aorta, with a considerable degree of dextroposition, overriding a ventricular septal defect through which a stylet has been passed; PA = pulmonary artery trunk of nrarkedly reduced caliber.
The area that in cases of tetralogy of Fallot corresponded to the center of the hypertrophic hemisphere located at the upper right cardiac border had a mean thickness of 14.3 mm. in cases of trilogy. Although a similarly shaped area was not present in these specimens, this portion was the thickest of the entire heart. Thickness of the wal1.s (Table I). The posterior border of the right ventricle at its basal portions showed a mean thickness similar to that found At the level in tetralogy of Fallot (10.4 mm.). of the anterior wall (apical region) the average a value similar to that thickness was 4.9 mm., found in tetralogy. By contrast, the thickness of the anterior wall at the level of the infundibulum was almost double that found in tetralogy (9 mm.). Crista supraventricularis. This structure was
Figure 4. Anatomic @ximen of a cue of pulmonary ualvular sttxosis with intact interwntricular septum and patent foranwn ouale (trilogy of Fallot). The right ventricle is open, and its internal structure is revealed. The aorta (Ao), placed posteriorly, arises entirely from the left ventricle. Note that the thickening of the pulmonary sigmoid valve cusps has caused a very marked valvular stenosis. The pulmonary artery (PA) exhibits a poststenotic dilatation. Hypertrophy of the right ventricular walls is homogeneous. The thickness of the posterobasal (pb) wall is equal to that of the anterior infundibular (ai) wall (9 mm.). The crista supraventricularis (c) is a thick muscle measuring 15 mm. in thickness. Behind the crista supraventricularis there is no interventricular septal defect. THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Tetralogy also hypertrophic,
with
mm., i.e., almost
Left
a mean
twice
Ventricle:
The
case.
In
no
trophic,
as it
was
in
The
ular wall
specimen many
mean
between frontal
the plane,
In
general,
septum
in cases of tetral-
was found
was nearly
VALVULAR
valvular septal
was
Fallot,
and quite
(Fig.
that is, it was directed with
a single
-110”. in
the
zontal, and
frontal
downward
exception
In trilogy
in the frontal
and to the right
in whichAthe
of Fallot
plane
tended
and the positions
was
plane,
axis was
the AQRS to
ranged
be
vector
more
between
hori+ 120”
-150”.
SPATIAL AXIS OF QRS (S&QRS) In the majority
of cases of tetralogy,
SAQRS
the
plane. INTER-
interventricular in tetralogy
of the pulmonary
thickened
was
artery
not
in the
malformed.
was
(mean
of
of Fallot,
of muscular
thickness
10 mm.)
5).
The
hemispheric
of the basal heart
had
that
of the
ventricle
an
average 8.5
wa:l
was twice
valvular
The
thickness
By con-
with
tetralogy in cases of
intact
that
inter-
of Fallot).
of the left ventricular
from
the
infundibular
in ordinary
(trilogy
right of
at the apex
to that found stenosis
septum
mm.;
of the
ventricle
that found
thickness
border
of the
17.5
seen in tetralogy.
pulmonary
not different
of
of the anterior
and similar
ventricular The
basal
of the right to that
border
thickness
mm.
the thickness
(9.5 mm.)
area at the level
of the right
posterior
was similar trast,
hypertrophic
portion
was
anterior
wall
+180”
a narrow
in trilogy
supraventricularis
and
by
and
of this group
crista
aspect
and
6) of Fallot
of the sigmoid
the findings
like those
the infundibulum The
the
cases,
STENOSIS,
agenesis
cusps
Unlike
2 specimens
+90
(FIG.
in tetralogy
DEFECT AND AGENESIS OF
ring,
valve
defect.
latter
characterized
pulmonary
pulmonary
between
PLANE
vector
SIGMOID VALVE CUSPS (2 CASES)
THE PULMONARY group
AQRS
in cases
to the frontal
PULMONARY
IN THE FRONTAL
interventricular
of the
parallel
SEPTAL
and
more frequently
in all
&RS
angle
interventricular
stenosis with intact
This
small
which
Indeed,
VENTRICULAR
border
Septum and
the
of pulmonary
III.
of the ventric-
the Interventricular
was found
septum
Fallot’s
border.
ogy of Fallot, septum.
it hyperof
for the posterior
and 11 mm. for the anterior
Relation Between the Frontal Plane:
was
777
of Fallot
The
was normal
cases
thickness
was 8.7 mm.
of 10.3
in tetralogy.
left ventricle
in every tetralogy.
thickness
that found
vs. Trilogy
walls was
seen in common
tetral-
ogy. ELECTROCARDIOGRAPHIC Electrocardiograms
were available
in 26 cases of tetralogy monary tum. helpful of right
data which
in the evaluation ventricular
and an attempt trocardiogram VOLUME
of Fallot
stenosis and intact Those
21,
JUNE
1968
for analysis
and in 9 of pul-
interventricular
might
prove
of the degree
hypertrophy
was made with
FINDINGS
were
to correlate
the anatomic
sep-
especially and type studied, the elec-
findings.
Figure 5. Specimen of a ease of stenosis of the pulmonary valvular ring, agenesis of the pulmonary valve cusps and interventricular septal defect. The right ventricle is open and it exhibits its internal structure. Observe that the pulmonary valvular ring (av) is narrow but there are no sigmoid valve cusps; instead, there is only a small fibrous Behind the ring measuring some 2 mm. in thickness. thickened (11 mm.) crista supraventricularis (c) there is However, the aorta is not a ventricular septal defect. dextroposed and it arises entirely from the left ventricle. Note that the type of hypertrophy is similar to that found in cases of pulmonary stenosis with intact interhypertrophy is homogeneous and ventricular septum; the thickness of the wall is similar in the posterobasal and in the anterior infundibular wall. PA = pulmonary artery, slightly dilated; pb = posterobasal wall, of great thickness (9 mm.); ai = anterior infundibular wall, also thickened (6.5 mm.).
Muiioz-Armas
778 FALLOT’S
et al.
FALLOT’S TRILOGY
TETRALOGY
-110
+90 . Figure 6. Distribution of the jrontai AQRS in cases of tetralogy sis with intact interventricular septum (trilogy of Fallot).
pointed to the right, to the front and downward ; cases in which it pointed forward and to the right were less numerous. In only 1 case did it point In other words, in the predominantly forward. majority of the cases the vector was predominantly directed to the right. In trilogy of Fallot the findings wereAquite different. In only 2 of 9 cases was the SAQRS similar to that found in tetralogy, i.?., pointing forward, to the right and downward. The usual finding (7 of 9 cases) was a spatial vector pointing mainly forward, with slight variations, to the right in some, downward in others and to Two pointed the right and downward in a frw. upward.
UNIPOLAR IN
THE
of Fallot and pulmonary
CONFIGURATIONS PRECORDIAL
Vl
THE
QRS TO
COMPLEX
9)
was seen when SAQRS pointed forward, right and downward, as was expected.
to the When
SAQRS pointed especially forward, these negative areas were not observed. Rs, R, or qR Complexes in the Right Precordial Leads: In tetralogy of Fallot the larger group (10 cases) had predominant R in VI exclusively;
Figure
7. Diagrammatic representatron of th &ctrocardiographic jndzngs III C~SCSof t&a&v of F&lot and pulmonary stenosis with intact inttwentricular septum (trilogy of
r
F&d).
In tetralogy there is usually a predominant R wave only in V,, and from V, on there appear rS type complexes. The T wave is usually positive from V2 on, or in all the precordial When it is negative in the leads. right precordial leads it is not peaked. In trilogy of Fallot there are usually tall predominant R waves in several precordial leads, and the Twave is negative and of the ischemic type in the right, or in all, precordial leads.
TRILOGY
L
OF
(FIG. 7
rS Complexes: The predominantly negative configurations of the rS type were registered from leads Vz to Vs in 5 cases of tetralogy of This preFallot and in only 1 case of trilogy. dominance of negative areas in cases of tetralogy
TETRALOGY A_,
LEADS
steno-
L
JQf
k
v2
V3
v4 THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Tetralogy
vs. Trilogy
i.e., the unipolar configuration of the free hypertrophic wall of the right ventricle was registered In lead Vz, the only in the first precordial lead. R wave decreased in height and the complexes became of the rS type, corresponding to the trabecular portion of the same free wall of the right ventricle (Fig. 8). In 8 cases, however, the predominant R wave persisted as far as Vg or even V5 and Vg. In the majority of the tracings of patients with trilogy (6 of 9), a tall R wave was registered beyond VI (Fig. 9). With a few exceptions, when the R wave, which corresponds to the electromotive forces
of Fallot
779
of the free hypertrophic wall of the right ventricle, is registered only in Vi, tetralogy rather If a tall R than trilogy should be considered. wave is seen in several precordial leads, it may be compatible with tetralogy but would be more suggestive of trilogy. RS Complexes: These transitional complexes were found in similar proportions and distribution in both diseases. BEHAVIOR
OF
THE
T
WAVE
In 7 cases of tetralogy of Fallot, the T wave was positive in all the precordial leads; this finding was observed in only 1 case of trilogy.
Figure 9. Electrocardiogram in a case of pulmonary rtenosis with intact interventricular septum and probe patent foramen ooale in a 20 year old woman. ,&QRS in the frontal Figure 8. Electrocardiogram in a C(ISE of tetralogy of the usual type in a 2 year old child. AQRS is at +130°.
The configuration of the ventricular complexes shows hypertrophy of the right ventricle with systolic overloading with Rs type complexes in Vr. In Vz there appear rS complexes which remain unchanged as far as Vs. The T wave is diphasic, of the minus plus type, in Vi and positive from Vs to V8. The P wave is peaked and of the “congenitale” type. VOLUME
21,
JUNE
I968
plane is at +125’. The configuration of the ventricular complexes shows right ventricular hypertrophy with systolic overloading. The most important differential features from tetralogy of Fallot are ventricular complexes with predominant R wave from Vi to V, (R in In V, there Vi, Rs in Vr, RS with tall R in Vs and V,). are RS complexes with equal R and S, and in Vg, rS complexes. The T wave is negative and peaked from vi to v,.
780
Muiioz-Armas
By contrast, the T wave was negative in the right or all of the precordial leads in 6 of the 9 cases of trilogy and in only 4 of the 26 cases of tetralogy. The configuration of the T wave showed different characteristics in these two conditions. T waves of the ischemic type, pointed, with a negative RS-T displacement of upward convexity were more common in trilogy (6 of 9 cases). In tetralogy, even in cases in which the T wave was negati1.e in the right precordial leads, it appeared asylnmetric and not pointed. ELECTROCARDIOGRAPHIC OF FALLOT
WITH
FINDINGS
PULMONARY
IN TETRALOGY
ATRESIA
Tracings in the:e cases did not differ from those seen in classic tetralogy. The spatial vector of ventricular depolarization (SAQRS) pointed downward, to the right and forward. In the 2 cases analyzed, configurations of the rS type from Vz to Va and a predominant R wave in VI were recorded. The T wave was positive from VI to VS in one tracing and from Vs to Vg in the other. In summary, the two tracings of this group were quite characteristic of the common type of tetralogy of Fallot. ELECTROCARDIOGRAPHIC TRICULAR
SEPTAL
VALVULAR
RING
AND AGENESIS
FINDINGS
DEFECT. OF
THE
IN
STENOSIS PULMONARY
OF THE PULMONARY
INTERVENOF
THE
ARTERY
SIGMOID VALVE
CUSPS
The tracings in this group were very similar to those described in trilogy of Fallot. In the 2 cases studied the R wave was tall from lead VI to \16 in 1 case and from lead VI to Vg in the other. The rS coluplexes, found quite frequently in tetralogy, were unusual in this Inalformation since they were seen only in lead Vg in 1 case. The T wave was not as characteristic in the precordial leads as the QRS complex ; the behavior of the T wave was intermediate between that observed in tetralogy and trilogy. Indeed, in 1 case the T wave was positive from Vz to Vs, as in tetralogy, and in the other it was negative from ‘1’1 to \-:$, pointed and of the ischemic type, as was usually seen in trilogy. In general, the tracings were more like those of trilogy, as was to be expected in view of the anatomic findings. 1>1sc:uss10n RIGHT VENTRICULAR HYPERTROPHY The electroanatornic comprehended without
correlation can not be taking into account the
et al. sequence of the ventricular activation process in right ventricular hypertrophy. In right ventricular hypertrophy the sequence and the sense of the erectors of normal ventricular activation are modified as follows : S’t$daI lector: As in norlnal instances, this vector originates in the middle of the left septal surface and points toward the base of the anterior papillary mrlscle in the right septal surface. However, in cases of Inarked right ventricular hypertrophy in which the interventricular septum tends to be parallel to the frontal plane, this first septal vector is not directed downward, forward and to the right as normally but rather downward, forward and somewhat to the left.Y For this reason in these cases one does not find a Q wave in the left precordial leads, and there may even be an initial negativity in the right precordial leads. In cases in which right ventricular hypertrophy is not marked and in which the parallelism of the interventricular septum with the frontal plane is less pronounced, the first septal vector may be directed as normally, downward, forward and to the right, in which case the left precordial leads will exhibit a slight initial negativity. Finally, in intermediate cases, the septal vector will point forward and no Q wave will be recorded in any precordial lead. After septal activation, the vectors of the free \rcntricIllar walls are inscribed. lectors of the Free Ventricular Walls: n’ormally the free ventricular walls, right and left, are activated simultaneously. However, in view of thr powerful activation forces of the left ventricular wall, which dominate the insignificant acti\ration forces of the thin free right ventricular wall, only one vector is considered (vector II) which corresponds to the activation forces of the free left ventricular wall and is directed downward, to the left and backward.8z1n-” In the presence of marked right ventricular hypertrophy the electrical forces due to the activation of the free right ventricular wall become more powerful than those originated by the activation of the free left ventricular wall. Two vectors should therefore be consideredg: that of the free left ventricular wall (vector III), which appears normal or of reduced magnitude, and that of the free wall of the right ventricle (\.ector nr), which is powerful and predominating. The orientation of vector m depends on the type of hypertrophy. Thus, in tetralogy of Fallot, as has been mentioned, the hypertrophy of the posterior and basal portions of the right ventricle predominates and vector ur is therefore THE AMERICAN JOURNALOF CARDIOLOGY
Tetralogy
vs. Trilogy
oriented predominantly downward, to the right In trilogy, hypertrophy affects and backward. the posterobasal portions as well as the anterior wall of the right ventricle at the level of the infundibulum and the parietal bundle of the crista supraventricularis. Vector nr is therefore oriented predominantly forward and somewhat downward and to the right. Basal Vector (III): In right ventricular hypertrophy this vector represents the basal electromotive forces of the septal mass and of the free wall of the right ventricle.sJ-13 It is directed, as normally, upward, backward and to the right. Because it is smaller in magnitude than vector In-, it is not recorded in the right precordial leads or, at most, is recorded as a small terminal negativity. Vector of the Low Right Septal Mass (Vector ZZs): The activation of the hypertrophic low right septal mass gives rise to a vector (vector IIS) that points mostly downward and occasionally somewhat to the left8J1J4; such a vector is responsible for the tall R waves in the transitional precordial leads, Vs and VA. This analysis accounts for the genesis of the ventricular activation complex (QRS) in tetralogy and in trilogy of Fallot. TETRALOGY OF FALLOT (FIG. 10) Septal Vector: As mentioned, in tetralogy of Fallot the angle normally formed by the interventricular septum with the frontal plane tends to become smaller, but a perfect parallel position is never reached. Since this position of the ventricular septum causes the septal vector to be directed predominantly forward,9 Q waves are generally not registered either in the right pre-
781
of Fallot
cordial leads (Vi and V,) or in the left precordial leads (V, and V,). Vectors of the Free Ventricular Walls: Vector nr is powerful and predominant. It is oriented downward, to the right and somewhat backward9 as a consequence of the predominant right ventricular hypertrophy, which is especially located in the posterobasal portions of the free right ventricular wall. Because of this orientation vector nr gives rise to tall R waves in lead Vi, since it projects almost entirely on the positive side of that lead. In the precordial leads placed to the left of VI, vector nr causes either a slight positivity or the beginning of a deep negativity. The orientation of vector nr accounts for the behavior of the QRS complex in the majority of instances of tetralogy of Fallot, which is characterized by the presence of predominant tall R waves (R or Rs complexes) only in Vi, with predominant S waves (rS or RS with larger S than R) in other precordial leads.‘5 Vector 111 is smaller than vector nr and is either not manifested in the right precordial leads or contributes to the inscription of the S wave from Vz on. In the left precordial leads, due to the proximity effect, vector 111is responsible for the inscription of a small positivity (R wave). Basal Vector: This vector is small; it is directed as normally, upward, to the right and backward,g and is manifested in the left precordial leads, thus contributing to the inscription of the terminal negativity (S wave). In the right precordial leads it is either not recorded or it contributes to the inscription of a terminal negativity.
10. Orientation of the vectors of ventricular activation in tetrology of F&lot and in pulmonary stenosis with intact interventricular septum (trilogy of Fallot). Note Figure
that in tetralogy vector I is directed fundamentally forward; on the contrary, in trilogy, vector I is usually directed forward and to the left as a result of the different position of the interventricular septum with respect to the frontal plane. The vector of the free wall of the right ventricle (nd) has a different orientation in relation to the areas of predominant hypertrophy in the two diseases. In tetralogy it is directed downward, backward and to the right; in trilogy, forward, to the right and downward.
VOLUME21, JUNE 1968
FALLOT’S TETRALOGY
FALLOT’S TRILOGY
782
Mufioz-Armas
Vector of the Right Sepal Mass (I Ector IZs): This vector is large in some cases of tetralogy. It is predominantly directed downward and forward ~v~J*J~ and it is expressed by tall R waves in thi transitional leads (V, and V4). In cases of tetralogy in which vector IIS is considerably increased there are tall R waves in several precordial leads, thus making it difficult to distinguish these cases electrocardiographically from those of pulmonary stenosis with intact interventricular septum. PULMOKARY TRICULAR
STENOSIS SEPTUM
WITH
(TRILOGY
INTACT OF
INTERVEN-
FALLOT)
Septal Vector: In every case of trilogy of Fallot, the inter\,entricular septum is parallel or almost parallel to the frontal plane. The left septal surface, where the activation of the interventricular septum begins, occupies a posterior position and the right septal surface a predominantly anterior position. The septal vector, therefore, will be oriented either forward,s in which case there will be no Q wave in any of the precordial leads, or forward and to the left, in which case there will be Q waves in the right precordial leads (VI or VI and VJ. Vectors of the I’entricular Free Walls: Homogeneous right ventricular hypertrophy is characteristic of pulmonary stenosis with intact interventricular septum ; it may involve the posterobasal regions as well as the anterior wall of the right ventricle at the infundibular level and the parietal branch of the crista supraventricularis. This causes the nr vector to be oriented predominantly forward.9!‘5 Because of this orientation, this vector is responsible for the inscription of tall R waves in several or all the precordial leads. In some cases, vector m is directed forward and somewhat to the right and contributes to the inscription of the beginning of a negative terminal deflection (S wave). In lead Vg vector III, as in tetralogy of Fallot, is responsible for the inscription of a small positivity in the left precordial leads (V, or Vh and V,). The magnitude and direction of Basal Vector: this vector is similar to that described in tetralIt contributes to the inscription of the S ogY.g wave in the left precordial leads (V, or Vs and V,) ; it does not manifest itself in the right precordial leads (VI or V1 and V2) or else it shows a terminal negativity (S wave). Right Septal Mass Vector: This vector points predominantly downward and forward and sometimes slightly to the left,s,g.12J4 contributing to the inscription of tall R waves in the transitional precordial leads: V3 and V+
et al.
BEHAVIOR
OF THE
TWAVE
We have seen that in tetralogy of Fallot the T wave may be positive in every precordial lead or negative in the right precordial leads (VI or VI and V,) and positive in the remaining chest leads. When it is negative in the right precordial leads, the T wave is asymmetric without significant RS-T segment displacement. Pulmonary stenosis with intact interventricular septum, on the other hand, generally causes negative T waves in the right, or in all, precordial leads, with a configuration of primary T waves of the ischemic type, peaked and with an RS-T segment displacement of upper convexity. 15,17,18 The behavior of the T wave in both diseases seems to be closely related to the degree of right ventricular pressure, which in tetralogy never rises above systemic pressure, whereas in pulmonary stenosis with intact interventricular septum it often rises beyond systemic pressure. In other words, the behavior of the T wave is related to the greater or lesser systolic overloading of the right ventricle. SPATIAL
AXIS OF QRS
(s;IQR~)
The behavior of SAQRS in tetralogy and in trilogy of Fallot is of special interest. We have se,en that in most cases of tetralogy of Fallot, SAQRS was directed to the right, forward and downward, whereas in trilogy it was directed predominantly forward, with slight deviations to the right in some cases, downward in others, to the right and downward in others and upward in 1 case. The direction of SffQRS in both diseases is explained by the anatomic characteristics, especially by the type of right ventricular hypertrophy, which is different for tetralogy and trilogy. In tetralogy of Fallot the mean thickness of the anterior wall of the right ventricle in the areas near the interventricular septum was 4.88 mm. for the apical region and 4.86 mm. for the infundibular region. In trilogy, the values were similar for the apical region (mean thickness 4.99 mm.) but in the infundibular region the mean parietal thickness of the anterior wall of the right ventricle was practically twice (9 mm.) the mean value found for the same region in tetralogy of Fallot (5.5 mm.). It can be stated that these areas with a greater thickness give rise to greater electromotive forces which predominate during ventricular depolarization and that they displace the mean spatial axis of QRS shifting its direction especially forward. THE
AMERICANJOURNALOFCARDIOLOGY
Tetralogy EMBRYOLOGIC
vs. Trilogy
DIFFERENCES
The different behavior of the anterior wall of the infundibulum of the right ventricle in tetralogy and trilogy of Fallot can be accounted for by the embryology of these conditions. In tetralogy there is an unequal partition of the truncoconus at the expense of the pulmonary artery, which has a very narrow caliber, a pulmonary valvular ring also of reduced diameter and a narrow infundibulum. The crista supraventricularis, which is an outgrowth of the displaced truncoconal septum, is also displaced forward and to the left, thereby narrowing the infundibulum. The result is a narrow infundibulum, often irregular and malformed and commonly exhibiting fibrosis of the crista and thin walls. The barrier formed by the infundibulovalvular stenosis is overcome by the hypertrophy only of the free walls of the inflow chamber of the right ventricle, whereas the walls of the malformed infundibulum are incapable of such a marked hypertrophic reaction. By contrast, in trilogy of Fallot the embryologic alteration affects only the primordia of the sigmoid pulmonary valve cusps, thus giving rise to thick valves with fusion of their commissures and with a very narrow valvular orifice. The infundibulum, on the other hand, is normally formed. The barrier constituted by the pulmonary valvular stenosis is overcome by the hypertrophy of both the infundibular walls and the crista supraventricularis and the free walls of the inflow chamber of the right ventricle. HEMODYNAMIC
DIFFERENCES
AND
THE
ELECTRO-
CARDIOGRAM
From a hemodynamic standpoint, in tetralogy there are three anatomic possibilities for an outlet for the blood under pressure within the right ventricle during systole: the narrow pulmonary orifice, the interventricular septal defect and the overriding aorta. Actually, blood does not flow from the right ventricle to the left through the ventricular septal defect. Rather, both chambers behave hemodynamically as a common chamber with equal intraventricular right and left ventricular ejection is pressures; simultaneous into the aorta. The flow contributed by each ventricle depends on the severity of the infundibulovalvular pulmonary stenosis and on the lesser or greater degree of dextroposition of the aorta. Because in tetralogy both ventricles function as a single chamber that empties fundamentally into the aorta the right intraventricular pressure is equal to left VOLUME
21,
JUNE
1968
of Fallot
783
intraventricular pressure and to systemic arterial pressure. In trilogy of Fallot blood is under great systolic right ventricular pressure and has only one outlet, i.e., the narrow pulmonary valve. The right intraventricular pressure increases proportionately to the degree of valvular obstruction and is often higher than systemic pressure. This extreme right intraventricular pressure in trilogy of Fallot is expressed electrocardiographically by alterations of the ventricular repolarization waves, characterized by T waves of the ischemic type that are deep, symmetric and peaked. There is a small group of cases (8 in our series of 26) in which tetralogy behaves electrocardiographically as does trilogy, exhibiting tall R w:ves in several precordial leads and with an SAQRS pointing predominantly forward. This is probably due to variations in the anatomic patterns. Indeed, when a small interventricular septal defect, a slight overriding of the aorta and a marked pulmonary stenosis coexist, tetralogy becomes similar to trilogy, both anatomically and hemodynamically. In cases of tetralogy with atresia of the pulmonary artery, the type of right ventricular hypertrophy differs very little from that found in classic tetralogy. The electrocardiographic pattern is also similar in both groups. In cases of interventricular septal defect, stenosis of the pulmonary valvular ring and agenesis of the pulmonary sigmoid valve cusps the hypertrophic pattern is similar to that seen in trilogy. But in this group the ventricular septal defect is an outlet of the blood from the hypertensive right ventricle, and the pressure is not as high as in cases of pulmonary stenosis with intact interventricular septum. This finding is expressed in the electrocardiogram by the lower incidence and severity of primary changes of the T wave. SUMMARY 1. An electrocardiographic-anatomic correlation of cases of tetralogy of Fallot and pulmonary stenosis with intact interventricular septum (trilogy of Fallot) was made, in an attempt to explain the electrocardiographic similarities and differences between these two malformations on the basis of the anatomic findings. 2. Fifty autopsy specimens were studied: 39 were cases of tetralogy, 9 were cases of pulmonary stenosis with intact interventricular septum and 2, stenosis of the pulmonary valvular ring
Mufioz-Armas et al.
784
with interventricular septal defect and agenesis of the pulmonary sigmoid valve cusps. An electrocardiogram was available for 39 cases. 3. The anatomic findings showed that hypertrophy of the right ventricle was homogeneous and generalized in pulmonary stenosis with intact interventricular septum; in tetralogy it was limited to a hemispheric area located at the union of the upper and the middle third of the The left ventricle in right border of the heart. tetralogy was generally hypotrophic; it was normal in pulmonary stenosis with intact interventricular septum. 4. In tetralogy of Fallot, .kQRS in the frontal plane pointed downward and to the right; in SAQRS trilogy it tended to be more horizontal. in the majority of instances of tetralogy pointed to the right, forward and downward ; in pulmonary stenosis with intact interventricular septurll it generally pointed predominantly forward. In the precordial leads the greater number of cases of tetralogy showed a predominant R wave only in Vi; in the majority of cases of trilogy, the predominant R wave was recorded beyond Vi. The T wave tended to be positive in the precordial leads in tetralogy of Fallot and negative in the right precordial leads or in all of the precordial leads in trilogy. 5. The sequence of the activation process of the ventricular walls in both malformations is discussed in relation to the different hypertrophic patterns and to the position of the interventricular septum with respect to the frontal plane.
REFERENCES V., NAVARRO, F., PEREIRA, D. and REINIIOLD, M. Communicaciones interventriculares en las cardiopatias congtnitas. Cardiologia., p. 1. SODI-PALLARES, D., editor. Mexico City, 1961. Interamericana, S.A. DE LA CRUZ, M. V. and DA ROCHA, J. P. Analisis embriol6gico de la tetralogia de Fallot, de complejo de Eisenmenger y de la transposicibn de 10s grandes vasos. Arch. Inst. cardiol. MLxico, 25: 699, 1955. ESPINO VELA, J. Elementes de diagnostico diferencial entre tetralogia y trilogia de Fallot. Principia cardiolbgica, 2: 52, 1955. ESPINOVELA, J. Malformaciones Cardiovasculares Congtnitas, p. 163. Mexico City, 1959. Edici6n de1 Instituto National de Cardiologia. DE LA CRUZ, M. V. Revisi6n de una teoria ontogenCtica sobre malformaciones cong6nitas troncoconales. Arch. Inst. cardiol. ML&o, 31: 509, 1961.
1. DE
2.
3.
4.
5.
LA
CRLJZ, M.
6. DE LA CRUZ, M. V. and DA ROCHA, J. P. An ontogenic theory for the explanation of congenital malformations involving the truncus and the corms. Am. Heart J., 51: 782, 1956. 7. DE LA CRUZ, M. V., ANSELMI, G., ROMERO, A. and MONROY, G. A qualitative and quantitative study of the ventricles and great vessels of normal children. Am. Heart J., 60: 675, 1960. 8. SODI-PALLARES, D. New Bases of Electrocardiography, p. 382. St. Louis, MO., 1956. C. V. Mosby. 9. SODI-PALLARES,D., BISTENI,A. and MEDRANO, G. .4. Electrocardiograffa y Vectocardiograffa Deductivas. Mexico City, 1964. La Prensa Mtdica Mexicana. 10. MEDRANO, G. A., SOTOMAYOR, A. and SODI-PALLARES, D. Nuevas investigaciones sobre la activacidn de1 tabique interventricular en condiciones normales y con bloqueo de rama. III. Estudio de1 tercio medio de1 tabique. Porciones anterior y media. Arch. Inst. cardiol. M&ico, 27: 609,1957. 11. PEISALOZA,D. and TRANCHESI,J. The three main vectors of the ventricular activation process in the normal human heart. I. Its significance. Am. Heart J., 49: 51, 1955. 12. BISTENI, A., TESTELLI, M., DE MICHELI, A., and MEDRANO, G. A. La activation ventricular y las morfologias unipolares en condiciones normales y en 10s bloqueos de rama. In Ref. 1, p. 131. 13. MEDRANO, G. A., BISTENI, ‘4, BRANCA.CO,R. W., PILEGGI,F. and SODI-PALLARES,D. The activation of the interventricular septum in the dog’s heart under normal conditions and in bundle branch block. Bull. New York Acad. SC., 65: 804, 1957. 14. MEDRANO, G. A., PILEGGI, F., BISTENI, A., DE MICHELLI, A. and SODI-PALLARES, D. Nuevas investigaciones sobre la activacibn de1 tabique interventricular en condiciones normales y con bloqueo de rama. V. Estudio de1 tercio inferior de1 tabique. To be published, 15. SODI-PALLARES, D., PIL~GGI, F., CISNEROS, F., GINEFRA, P., PORTILLO, B., MEDRANO, G. A. and BISTENI, A. The mean manifest electrical axis of the ventricuar activation process (AQRS) in congenital heart disease: A new approach in electrocardiographic diagnosis. Am. Heart J., 55: 681, 1958. 16. MEDRANO, G. A., DE MICHELLI, A., HERTAULT, J. and SODI-PALLARES, D. La activaci6n de la cresta supraventricular en el corazon de1 perro. Arch. Inst. cardiol. M&co, 30: 432, 1960. 17. SODI-PALLARES, D., PORTILLO, B. CISNEROS, F., DE LA CRUZ, M. V. and ACOSTA, A. R. Electrocardiography in infants and children. Pediat. Clin. North America, 14, 871, 1958. 18. PORTILLO, B. and SODI-PALLARES, D. Semiologia electrocardiogrifica de la hipertrofia ventricular y sobrecarga sist6lica de1 ventriculo derecho en 10s padecimientos congenitos de1 corazbn. Principia cardinlbgica, 6: 231, 1959.
THE AMERICANJOURNALOF
CARDIOLOGY
Journal
21
JUNE
Symposium
with
Heart
of Fallot Intact
Anatomic SIMON Mu~~oz-ARMAS,
1968
M.D.,?
6
TORO,
M.D., DEMETRIO
V. DE LA CRUZ, City,
DIFFERENTIAL electrocardiographic diagnosis between pulmonary stenosis with intact interventricular septum plus patent foramen ovale or atria1 septal defect (trilogy of Fallot) and pulmonary stenosis with associated interventricular septal defect and dextroposition of the aorta (tetralogy of Fallot) is sometimes This fact has prompted us to establish difficult. the electrocardiographic similarities and differences between these two malformations in the light of the ventricular activation process and the anatomic findings. This study includes the anatomic analysis of 50 autopsy specimens; in 39 of these cases electrocardiographic tracings were available.
II
Stenosis
Septum
and Electrocardiographic ANGEL DEL
Part
and Pulmonary
Mexico
Study*
SODI-PALLARES,
M.D., F.A.c’.c.
and
M.D.
Mexico
Mexico were studied. Of these, 39 cases were diagnosed as tetralogy of Fallot in view of the following features: (1) pulmonary stenosis of various degrees or atresia of the pulmonary artery; (2) middle basal interventricular septal defect,’ i.e., a defect lying in the membranous portion of the interventricular septum; (3) dextroposition of the aorta; and (4) right ventricular hypertrophy.2-4 Embryologically this malformation results from an unequal partition of the truncoconus at the expense of the pulmonary artery, with or without dextroposition of the truncoconus.2J Of the 39 cases of true tetralogy of Fallot, 34 were of the common type, with valvular and infundibular stenosis of the pulmonary artery; in 5 there was atresia of the pulmonary artery, that is. they belonged to the group which some authors designate pseudotruncus arteriosus. In the 2 remaining specimens, the malformation was more complex: the pulmonary valvular ring was quite narrow and there was agenesis of the pulmonary sigmoid valve cusps which caused pulmonary regurgitation. There was also a middle basal ventricular septal defect.’
HE
MATERIAL
Disease.
Interventricular
MARIA
T
Number
on Electrocardiography
in Congenital Tetralogy
of Cardiology
AND METHOD
Forty-one specimens of pulmonary stenosis plus ventricular septal defect from the Museum of Embryology of the Instituto National de Cardiologia de
* From the Departments of Electrocardiography and Embryology, Instituto National de Cardiologia de Mtxico, Mexico City, Mexico. Simbn Mufioz-Armas, M.D., Hospital Universitario de Caracas, Det Present address and address for reprints: partamento de Cardiologia, Ciudad Universitaria, Caracas, Venezuela. 773
Mufioz-Armas
774
Nine specimens with pulmonary valvular stenosis! intact interventricular septum and an atria1 septal defect or a patent foramen ovale were also studied. This malformation is termed trilogy of Fallot by some workers.3 This report will emphasize those anatomic details that may be of importance in the genesis of the electrical forces of the heart, such as the thicknessof the ventricular walls, the site of predominant hypertrophy, the position of the heart and the degree of rotation along its different axes. Special attention is given to the position of the interventricular septum and its spatial relations on the frontal plane. ANATOMIC I.
TRUE
TETRALOGY
et al. Its upper third of the right border of the heart. diameter varied according to the size of the heart and measured an average of approximately In all cases the upper limit of the hyper3 cm. trophic area was close to the right atrioventricuThis was the region lar groove (Fig. 1 and 2). of greatest thickness of the right ventricle, since the mean thickness of the free ventricular wall which corresponded to the center of the hypertrophic hemisphere was 15.3 mm.
FINDINGS
OF FALLOT
This group consisted of 39 specimens which were divided into two subgroups based on the presence or absence of pulmonary atresia. A.
Typical Tetralogy of Fallot (34 Cases)
This subgroup was characterized by the presence of both infundibular and valvular pulmonary stenosis. In the majority of cases, infundibular stenosis was more marked than valvular stenosis. The infundibulum was typically narrow and distorted, and it varied in length The from a few millimeters to normal length. crista supraventricularis was either normal in thickness or thin ; it was never hypertrophic. As a rule it exhibited some fibrosis, and in 1 case was represented by a very thin fibrous band, 1 mm. thick, and had no muscular component. In every case, the ventricular septal defect was of the middle basal type, that is, it was located at the level of the membranous portion of the septum behind the crista supraventricularis.l,G Aortic dextroposition was of various degrees. In most cases there was a 50 per cent or greater There was no correlaoverriding of the vessel. tion between the degree of aortic dextroposition and the degree of pulmonary stenosis. Right Ventricle: The right ventricle occupied externally the greater part of the anterior aspect of the heart, or between two thirds and the entire extent of this aspect. In the majority of the cases (53 per cent), the right ventricle comprised three fourths of the anterior aspect of the heart. In tetralogy of Fallot Predominant hypertrophy. one does not find a homogeneous and generalized hypertrophy. In our specimens hypertrophy was limited to one area of the free wall of the right ventricle. This area was hemispheric in shape, and its center was located approximately at the union of the middle third with the
Figure
1. i&gram showing the location of the area of maximal h.vpertrophy,which is a hemispheric area lying in the upper third of the right border of the heart in
cases of tetralogy spheric zone; RV Ao = overriding artery.
of Fallot. C = hypertrophic hemi= right ventricle; LV = left ventricle; aorta; PA = hypoplastic pulmonary
Thickness of the walls (Table I). The area of greatest thickness outside the hypertrophic hemisphere was seen in the basal portions of the posterior border of the right ventricle.* In this By conarea the mean thickness was 9 mm. trast, the average thickness of the thin anterior wall of the infundibulum (Fig. 2), was 4.86 mm., a value quite similar to the average thickness of the apical portion of the same anterior wall In other areas of the right ventricle (4.88 mm.) * The posterior border of the right ventricle is that section which is parallel and adjacent to the posterior intwventricular coronary artery, to the right of the interventricular septum. THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Tetralogy
vs. Trilogy
the values obtained were halfway between those mentioned. Crista supraventricularis. The parietal bundle of the crista supraventricularis was normal or In some inthin in the majority of the cases. stances it was fibrous; the mean thickness was 5.5 mm., which is within the average normal value for similar age groups.’ Left Ventricle: The left ventricle was always normal or hypotrophic. The average thickness
775
of Fallot
the angle formed by the interventricular septum and the frontal plane tended to diminish owing to the forward displacement of the right ventricle and the backward and leftward displacement of In only 2 cases was the interthe left ventricle. ventricular septum nearly parallel to the frontal plane. B. Tetralogy of Fallot with Pulmonary Atresia (5 Cases) This group was characterized by atresia of the pulmonary valve with or without aplasia of the infundibulum. The trunk of the pulmonary artery was extremely hypoplastic and exhibited branches of variable size. The parietal branch of the crista supraventricularis was displaced considerably forward and to the left; it fused with the anterior infundibular wall and occluded the infundibular channel, thus constituting a muscular mass placed anteriorly. Its mean thickness was 13.5 mm. The remaining anatomic characteristics were not different from those of the average case of tetralogy of Fallot (Fig. 3). The predominant hypertrophy was located at the same region as in the previous group, in a hemisphere-like area with a mean thickness of 14.5 mm. II.
2. Anatomic spe&nen of (I tare of tetralogy of Fallot. The right ventricle is open. Observe that hypertrophy predominates in the posterobasal portion (pb) in an area the shape of a hemisphere whose thickness (15 mm.) is three times greater than that of the anterior infundibular wall (ai) (5 mm.). c = crista supraventricularis, of normal thickness; Ao = aorta, showing marked dextroposition, arising almost entirely from the right ventricle. The stylus is crossing the very narrow pulmonary valvular orifice. To the left and behind the crista supraventricularis can be seen the ventricular septal defect, over which lies the overriding aorta.
Figure
of the ventricular wall was equal for the anterior and posterior borders,* with a mean value of 8 mm. Relation of the Interventricular Septum to the Frontal Plane: The interventricular septum tended to be parallel to the frontal plane, that is, * The anterior border of the left ventricle is that given by a section which is parallel and adjacent to the anterior descending artery, to the left of the interventricular septum. The posterior border is that determined by a section parallel and adjacent to the posterior interventricular coronary artery, to the left of the septum. VOLUME 21, JUNE 1968
STENOSIS
INTACT SEPTAL (TRILOGY
OF THE PULMONARY
INTERVENTRICULAR DEFECT
OR
OF FALLOT)
PATENT
(9
ARTERY
SEPTUM
WITH
AND
ATRIAL
FORAMEN
OVALE
CASES)
This group was characterized by the presence of pulmonary valvular stenosis. The pulmonary sigmoid valve cusps were thickened and fused at their commissures; in the majority of instances they formed a funnel-shaped structure, the vertex of which protruded into the lumen of the pulmonary artery. The hypertrophy of the infundibular walls reduced the cavity of the infundibulum by variable degrees. In 6 cases the foramen ovale was patent, and in 3 there was a true atria1 septal defect in the region of the fossa ovalis. Right Ventricle: In the majority of instances (7 cases) the right ventricle occupied the anterior two thirds of the heart. In 2 cases it formed the entire anterior aspect of the heart. Predominant hypertrophy. In contrast to the findings in tetralogy of Fallot, hypertrophy of the right ventricular walls was diffuse and generalized, involving both the posterior and basal portions as well as the anterior wall of the right ventricle (Fig. 4).
Muiioz-Armas
776
et al.
TABLE I Mean
Value
(mm.)
-~~~~~~ No. of .\natomic Specimens Fallot’s tetralogy Fallot’s trilogy
of the Thickness ~~~~
Hypertrophic Hemisphere
35
15.30
9
14.30
of the Free ~~Right
Posterobasal Border ‘1 00 10.40
Ventricular
Ventricle .\nteroapical Border
Walls
~_~~~_._ Anterior Infundibular Border
4.88
4.68
9.00
9.00
(44 ._-.
Cases) ~~ ~_
Crista Supraventricularis 5.5 10
Left Ventricle Posterior Anterior Border Border 8
3
8.7
8 11
Figure
3. Anatomic specimen of a case of trtralogy of F&lot with atresia of the pulmonary artery (pseudotruncus arteriosus). The right ventricle is open revealing its various structures. Hypertrophy is predominant in the posterior basal (pb) area (12 mm. in thickness). The anterior infundibular wall (ai) is of normal thickness Observe that the pulmonary artery valve is (4 mm.). atretic. Ao = aorta, with a considerable degree of dextroposition, overriding a ventricular septal defect through which a stylet has been passed; PA = pulmonary artery trunk of nrarkedly reduced caliber.
The area that in cases of tetralogy of Fallot corresponded to the center of the hypertrophic hemisphere located at the upper right cardiac border had a mean thickness of 14.3 mm. in cases of trilogy. Although a similarly shaped area was not present in these specimens, this portion was the thickest of the entire heart. Thickness of the wal1.s (Table I). The posterior border of the right ventricle at its basal portions showed a mean thickness similar to that found At the level in tetralogy of Fallot (10.4 mm.). of the anterior wall (apical region) the average a value similar to that thickness was 4.9 mm., found in tetralogy. By contrast, the thickness of the anterior wall at the level of the infundibulum was almost double that found in tetralogy (9 mm.). Crista supraventricularis. This structure was
Figure 4. Anatomic @ximen of a cue of pulmonary ualvular sttxosis with intact interwntricular septum and patent foranwn ouale (trilogy of Fallot). The right ventricle is open, and its internal structure is revealed. The aorta (Ao), placed posteriorly, arises entirely from the left ventricle. Note that the thickening of the pulmonary sigmoid valve cusps has caused a very marked valvular stenosis. The pulmonary artery (PA) exhibits a poststenotic dilatation. Hypertrophy of the right ventricular walls is homogeneous. The thickness of the posterobasal (pb) wall is equal to that of the anterior infundibular (ai) wall (9 mm.). The crista supraventricularis (c) is a thick muscle measuring 15 mm. in thickness. Behind the crista supraventricularis there is no interventricular septal defect. THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Tetralogy also hypertrophic,
with
mm., i.e., almost
Left
a mean
twice
Ventricle:
The
case.
In
no
trophic,
as it
was
in
The
ular wall
specimen many
mean
between frontal
the plane,
In
general,
septum
in cases of tetral-
was found
was nearly
VALVULAR
valvular septal
was
Fallot,
and quite
(Fig.
that is, it was directed with
a single
-110”. in
the
zontal, and
frontal
downward
exception
In trilogy
in the frontal
and to the right
in whichAthe
of Fallot
plane
tended
and the positions
was
plane,
axis was
the AQRS to
ranged
be
vector
more
between
hori+ 120”
-150”.
SPATIAL AXIS OF QRS (S&QRS) In the majority
of cases of tetralogy,
SAQRS
the
plane. INTER-
interventricular in tetralogy
of the pulmonary
thickened
was
artery
not
in the
malformed.
was
(mean
of
of Fallot,
of muscular
thickness
10 mm.)
5).
The
hemispheric
of the basal heart
had
that
of the
ventricle
an
average 8.5
wa:l
was twice
valvular
The
thickness
By con-
with
tetralogy in cases of
intact
that
inter-
of Fallot).
of the left ventricular
from
the
infundibular
in ordinary
(trilogy
right of
at the apex
to that found stenosis
septum
mm.;
of the
ventricle
that found
thickness
border
of the
17.5
seen in tetralogy.
pulmonary
not different
of
of the anterior
and similar
ventricular The
basal
of the right to that
border
thickness
mm.
the thickness
(9.5 mm.)
area at the level
of the right
posterior
was similar trast,
hypertrophic
portion
was
anterior
wall
+180”
a narrow
in trilogy
supraventricularis
and
by
and
of this group
crista
aspect
and
6) of Fallot
of the sigmoid
the findings
like those
the infundibulum The
the
cases,
STENOSIS,
agenesis
cusps
Unlike
2 specimens
+90
(FIG.
in tetralogy
DEFECT AND AGENESIS OF
ring,
valve
defect.
latter
characterized
pulmonary
pulmonary
between
PLANE
vector
SIGMOID VALVE CUSPS (2 CASES)
THE PULMONARY group
AQRS
in cases
to the frontal
PULMONARY
IN THE FRONTAL
interventricular
of the
parallel
SEPTAL
and
more frequently
in all
&RS
angle
interventricular
stenosis with intact
This
small
which
Indeed,
VENTRICULAR
border
Septum and
the
of pulmonary
III.
of the ventric-
the Interventricular
was found
septum
Fallot’s
border.
ogy of Fallot, septum.
it hyperof
for the posterior
and 11 mm. for the anterior
Relation Between the Frontal Plane:
was
777
of Fallot
The
was normal
cases
thickness
was 8.7 mm.
of 10.3
in tetralogy.
left ventricle
in every tetralogy.
thickness
that found
vs. Trilogy
walls was
seen in common
tetral-
ogy. ELECTROCARDIOGRAPHIC Electrocardiograms
were available
in 26 cases of tetralogy monary tum. helpful of right
data which
in the evaluation ventricular
and an attempt trocardiogram VOLUME
of Fallot
stenosis and intact Those
21,
JUNE
1968
for analysis
and in 9 of pul-
interventricular
might
prove
of the degree
hypertrophy
was made with
FINDINGS
were
to correlate
the anatomic
sep-
especially and type studied, the elec-
findings.
Figure 5. Specimen of a ease of stenosis of the pulmonary valvular ring, agenesis of the pulmonary valve cusps and interventricular septal defect. The right ventricle is open and it exhibits its internal structure. Observe that the pulmonary valvular ring (av) is narrow but there are no sigmoid valve cusps; instead, there is only a small fibrous Behind the ring measuring some 2 mm. in thickness. thickened (11 mm.) crista supraventricularis (c) there is However, the aorta is not a ventricular septal defect. dextroposed and it arises entirely from the left ventricle. Note that the type of hypertrophy is similar to that found in cases of pulmonary stenosis with intact interhypertrophy is homogeneous and ventricular septum; the thickness of the wall is similar in the posterobasal and in the anterior infundibular wall. PA = pulmonary artery, slightly dilated; pb = posterobasal wall, of great thickness (9 mm.); ai = anterior infundibular wall, also thickened (6.5 mm.).
Muiioz-Armas
778 FALLOT’S
et al.
FALLOT’S TRILOGY
TETRALOGY
-110
+90 . Figure 6. Distribution of the jrontai AQRS in cases of tetralogy sis with intact interventricular septum (trilogy of Fallot).
pointed to the right, to the front and downward ; cases in which it pointed forward and to the right were less numerous. In only 1 case did it point In other words, in the predominantly forward. majority of the cases the vector was predominantly directed to the right. In trilogy of Fallot the findings wereAquite different. In only 2 of 9 cases was the SAQRS similar to that found in tetralogy, i.?., pointing forward, to the right and downward. The usual finding (7 of 9 cases) was a spatial vector pointing mainly forward, with slight variations, to the right in some, downward in others and to Two pointed the right and downward in a frw. upward.
UNIPOLAR IN
THE
of Fallot and pulmonary
CONFIGURATIONS PRECORDIAL
Vl
THE
QRS TO
COMPLEX
9)
was seen when SAQRS pointed forward, right and downward, as was expected.
to the When
SAQRS pointed especially forward, these negative areas were not observed. Rs, R, or qR Complexes in the Right Precordial Leads: In tetralogy of Fallot the larger group (10 cases) had predominant R in VI exclusively;
Figure
7. Diagrammatic representatron of th &ctrocardiographic jndzngs III C~SCSof t&a&v of F&lot and pulmonary stenosis with intact inttwentricular septum (trilogy of
r
F&d).
In tetralogy there is usually a predominant R wave only in V,, and from V, on there appear rS type complexes. The T wave is usually positive from V2 on, or in all the precordial When it is negative in the leads. right precordial leads it is not peaked. In trilogy of Fallot there are usually tall predominant R waves in several precordial leads, and the Twave is negative and of the ischemic type in the right, or in all, precordial leads.
TRILOGY
L
OF
(FIG. 7
rS Complexes: The predominantly negative configurations of the rS type were registered from leads Vz to Vs in 5 cases of tetralogy of This preFallot and in only 1 case of trilogy. dominance of negative areas in cases of tetralogy
TETRALOGY A_,
LEADS
steno-
L
JQf
k
v2
V3
v4 THE
AMERICAN
JOURNAL
OF
CARDIOLOGY
Tetralogy
vs. Trilogy
i.e., the unipolar configuration of the free hypertrophic wall of the right ventricle was registered In lead Vz, the only in the first precordial lead. R wave decreased in height and the complexes became of the rS type, corresponding to the trabecular portion of the same free wall of the right ventricle (Fig. 8). In 8 cases, however, the predominant R wave persisted as far as Vg or even V5 and Vg. In the majority of the tracings of patients with trilogy (6 of 9), a tall R wave was registered beyond VI (Fig. 9). With a few exceptions, when the R wave, which corresponds to the electromotive forces
of Fallot
779
of the free hypertrophic wall of the right ventricle, is registered only in Vi, tetralogy rather If a tall R than trilogy should be considered. wave is seen in several precordial leads, it may be compatible with tetralogy but would be more suggestive of trilogy. RS Complexes: These transitional complexes were found in similar proportions and distribution in both diseases. BEHAVIOR
OF
THE
T
WAVE
In 7 cases of tetralogy of Fallot, the T wave was positive in all the precordial leads; this finding was observed in only 1 case of trilogy.
Figure 9. Electrocardiogram in a case of pulmonary rtenosis with intact interventricular septum and probe patent foramen ooale in a 20 year old woman. ,&QRS in the frontal Figure 8. Electrocardiogram in a C(ISE of tetralogy of the usual type in a 2 year old child. AQRS is at +130°.
The configuration of the ventricular complexes shows hypertrophy of the right ventricle with systolic overloading with Rs type complexes in Vr. In Vz there appear rS complexes which remain unchanged as far as Vs. The T wave is diphasic, of the minus plus type, in Vi and positive from Vs to V8. The P wave is peaked and of the “congenitale” type. VOLUME
21,
JUNE
I968
plane is at +125’. The configuration of the ventricular complexes shows right ventricular hypertrophy with systolic overloading. The most important differential features from tetralogy of Fallot are ventricular complexes with predominant R wave from Vi to V, (R in In V, there Vi, Rs in Vr, RS with tall R in Vs and V,). are RS complexes with equal R and S, and in Vg, rS complexes. The T wave is negative and peaked from vi to v,.
780
Muiioz-Armas
By contrast, the T wave was negative in the right or all of the precordial leads in 6 of the 9 cases of trilogy and in only 4 of the 26 cases of tetralogy. The configuration of the T wave showed different characteristics in these two conditions. T waves of the ischemic type, pointed, with a negative RS-T displacement of upward convexity were more common in trilogy (6 of 9 cases). In tetralogy, even in cases in which the T wave was negati1.e in the right precordial leads, it appeared asylnmetric and not pointed. ELECTROCARDIOGRAPHIC OF FALLOT
WITH
FINDINGS
PULMONARY
IN TETRALOGY
ATRESIA
Tracings in the:e cases did not differ from those seen in classic tetralogy. The spatial vector of ventricular depolarization (SAQRS) pointed downward, to the right and forward. In the 2 cases analyzed, configurations of the rS type from Vz to Va and a predominant R wave in VI were recorded. The T wave was positive from VI to VS in one tracing and from Vs to Vg in the other. In summary, the two tracings of this group were quite characteristic of the common type of tetralogy of Fallot. ELECTROCARDIOGRAPHIC TRICULAR
SEPTAL
VALVULAR
RING
AND AGENESIS
FINDINGS
DEFECT. OF
THE
IN
STENOSIS PULMONARY
OF THE PULMONARY
INTERVENOF
THE
ARTERY
SIGMOID VALVE
CUSPS
The tracings in this group were very similar to those described in trilogy of Fallot. In the 2 cases studied the R wave was tall from lead VI to \16 in 1 case and from lead VI to Vg in the other. The rS coluplexes, found quite frequently in tetralogy, were unusual in this Inalformation since they were seen only in lead Vg in 1 case. The T wave was not as characteristic in the precordial leads as the QRS complex ; the behavior of the T wave was intermediate between that observed in tetralogy and trilogy. Indeed, in 1 case the T wave was positive from Vz to Vs, as in tetralogy, and in the other it was negative from ‘1’1 to \-:$, pointed and of the ischemic type, as was usually seen in trilogy. In general, the tracings were more like those of trilogy, as was to be expected in view of the anatomic findings. 1>1sc:uss10n RIGHT VENTRICULAR HYPERTROPHY The electroanatornic comprehended without
correlation can not be taking into account the
et al. sequence of the ventricular activation process in right ventricular hypertrophy. In right ventricular hypertrophy the sequence and the sense of the erectors of normal ventricular activation are modified as follows : S’t$daI lector: As in norlnal instances, this vector originates in the middle of the left septal surface and points toward the base of the anterior papillary mrlscle in the right septal surface. However, in cases of Inarked right ventricular hypertrophy in which the interventricular septum tends to be parallel to the frontal plane, this first septal vector is not directed downward, forward and to the right as normally but rather downward, forward and somewhat to the left.Y For this reason in these cases one does not find a Q wave in the left precordial leads, and there may even be an initial negativity in the right precordial leads. In cases in which right ventricular hypertrophy is not marked and in which the parallelism of the interventricular septum with the frontal plane is less pronounced, the first septal vector may be directed as normally, downward, forward and to the right, in which case the left precordial leads will exhibit a slight initial negativity. Finally, in intermediate cases, the septal vector will point forward and no Q wave will be recorded in any precordial lead. After septal activation, the vectors of the free \rcntricIllar walls are inscribed. lectors of the Free Ventricular Walls: n’ormally the free ventricular walls, right and left, are activated simultaneously. However, in view of thr powerful activation forces of the left ventricular wall, which dominate the insignificant acti\ration forces of the thin free right ventricular wall, only one vector is considered (vector II) which corresponds to the activation forces of the free left ventricular wall and is directed downward, to the left and backward.8z1n-” In the presence of marked right ventricular hypertrophy the electrical forces due to the activation of the free right ventricular wall become more powerful than those originated by the activation of the free left ventricular wall. Two vectors should therefore be consideredg: that of the free left ventricular wall (vector III), which appears normal or of reduced magnitude, and that of the free wall of the right ventricle (\.ector nr), which is powerful and predominating. The orientation of vector m depends on the type of hypertrophy. Thus, in tetralogy of Fallot, as has been mentioned, the hypertrophy of the posterior and basal portions of the right ventricle predominates and vector ur is therefore THE AMERICAN JOURNALOF CARDIOLOGY
Tetralogy
vs. Trilogy
oriented predominantly downward, to the right In trilogy, hypertrophy affects and backward. the posterobasal portions as well as the anterior wall of the right ventricle at the level of the infundibulum and the parietal bundle of the crista supraventricularis. Vector nr is therefore oriented predominantly forward and somewhat downward and to the right. Basal Vector (III): In right ventricular hypertrophy this vector represents the basal electromotive forces of the septal mass and of the free wall of the right ventricle.sJ-13 It is directed, as normally, upward, backward and to the right. Because it is smaller in magnitude than vector In-, it is not recorded in the right precordial leads or, at most, is recorded as a small terminal negativity. Vector of the Low Right Septal Mass (Vector ZZs): The activation of the hypertrophic low right septal mass gives rise to a vector (vector IIS) that points mostly downward and occasionally somewhat to the left8J1J4; such a vector is responsible for the tall R waves in the transitional precordial leads, Vs and VA. This analysis accounts for the genesis of the ventricular activation complex (QRS) in tetralogy and in trilogy of Fallot. TETRALOGY OF FALLOT (FIG. 10) Septal Vector: As mentioned, in tetralogy of Fallot the angle normally formed by the interventricular septum with the frontal plane tends to become smaller, but a perfect parallel position is never reached. Since this position of the ventricular septum causes the septal vector to be directed predominantly forward,9 Q waves are generally not registered either in the right pre-
781
of Fallot
cordial leads (Vi and V,) or in the left precordial leads (V, and V,). Vectors of the Free Ventricular Walls: Vector nr is powerful and predominant. It is oriented downward, to the right and somewhat backward9 as a consequence of the predominant right ventricular hypertrophy, which is especially located in the posterobasal portions of the free right ventricular wall. Because of this orientation vector nr gives rise to tall R waves in lead Vi, since it projects almost entirely on the positive side of that lead. In the precordial leads placed to the left of VI, vector nr causes either a slight positivity or the beginning of a deep negativity. The orientation of vector nr accounts for the behavior of the QRS complex in the majority of instances of tetralogy of Fallot, which is characterized by the presence of predominant tall R waves (R or Rs complexes) only in Vi, with predominant S waves (rS or RS with larger S than R) in other precordial leads.‘5 Vector 111 is smaller than vector nr and is either not manifested in the right precordial leads or contributes to the inscription of the S wave from Vz on. In the left precordial leads, due to the proximity effect, vector 111is responsible for the inscription of a small positivity (R wave). Basal Vector: This vector is small; it is directed as normally, upward, to the right and backward,g and is manifested in the left precordial leads, thus contributing to the inscription of the terminal negativity (S wave). In the right precordial leads it is either not recorded or it contributes to the inscription of a terminal negativity.
10. Orientation of the vectors of ventricular activation in tetrology of F&lot and in pulmonary stenosis with intact interventricular septum (trilogy of Fallot). Note Figure
that in tetralogy vector I is directed fundamentally forward; on the contrary, in trilogy, vector I is usually directed forward and to the left as a result of the different position of the interventricular septum with respect to the frontal plane. The vector of the free wall of the right ventricle (nd) has a different orientation in relation to the areas of predominant hypertrophy in the two diseases. In tetralogy it is directed downward, backward and to the right; in trilogy, forward, to the right and downward.
VOLUME21, JUNE 1968
FALLOT’S TETRALOGY
FALLOT’S TRILOGY
782
Mufioz-Armas
Vector of the Right Sepal Mass (I Ector IZs): This vector is large in some cases of tetralogy. It is predominantly directed downward and forward ~v~J*J~ and it is expressed by tall R waves in thi transitional leads (V, and V4). In cases of tetralogy in which vector IIS is considerably increased there are tall R waves in several precordial leads, thus making it difficult to distinguish these cases electrocardiographically from those of pulmonary stenosis with intact interventricular septum. PULMOKARY TRICULAR
STENOSIS SEPTUM
WITH
(TRILOGY
INTACT OF
INTERVEN-
FALLOT)
Septal Vector: In every case of trilogy of Fallot, the inter\,entricular septum is parallel or almost parallel to the frontal plane. The left septal surface, where the activation of the interventricular septum begins, occupies a posterior position and the right septal surface a predominantly anterior position. The septal vector, therefore, will be oriented either forward,s in which case there will be no Q wave in any of the precordial leads, or forward and to the left, in which case there will be Q waves in the right precordial leads (VI or VI and VJ. Vectors of the I’entricular Free Walls: Homogeneous right ventricular hypertrophy is characteristic of pulmonary stenosis with intact interventricular septum ; it may involve the posterobasal regions as well as the anterior wall of the right ventricle at the infundibular level and the parietal branch of the crista supraventricularis. This causes the nr vector to be oriented predominantly forward.9!‘5 Because of this orientation, this vector is responsible for the inscription of tall R waves in several or all the precordial leads. In some cases, vector m is directed forward and somewhat to the right and contributes to the inscription of the beginning of a negative terminal deflection (S wave). In lead Vg vector III, as in tetralogy of Fallot, is responsible for the inscription of a small positivity in the left precordial leads (V, or Vh and V,). The magnitude and direction of Basal Vector: this vector is similar to that described in tetralIt contributes to the inscription of the S ogY.g wave in the left precordial leads (V, or Vs and V,) ; it does not manifest itself in the right precordial leads (VI or V1 and V2) or else it shows a terminal negativity (S wave). Right Septal Mass Vector: This vector points predominantly downward and forward and sometimes slightly to the left,s,g.12J4 contributing to the inscription of tall R waves in the transitional precordial leads: V3 and V+
et al.
BEHAVIOR
OF THE
TWAVE
We have seen that in tetralogy of Fallot the T wave may be positive in every precordial lead or negative in the right precordial leads (VI or VI and V,) and positive in the remaining chest leads. When it is negative in the right precordial leads, the T wave is asymmetric without significant RS-T segment displacement. Pulmonary stenosis with intact interventricular septum, on the other hand, generally causes negative T waves in the right, or in all, precordial leads, with a configuration of primary T waves of the ischemic type, peaked and with an RS-T segment displacement of upper convexity. 15,17,18 The behavior of the T wave in both diseases seems to be closely related to the degree of right ventricular pressure, which in tetralogy never rises above systemic pressure, whereas in pulmonary stenosis with intact interventricular septum it often rises beyond systemic pressure. In other words, the behavior of the T wave is related to the greater or lesser systolic overloading of the right ventricle. SPATIAL
AXIS OF QRS
(s;IQR~)
The behavior of SAQRS in tetralogy and in trilogy of Fallot is of special interest. We have se,en that in most cases of tetralogy of Fallot, SAQRS was directed to the right, forward and downward, whereas in trilogy it was directed predominantly forward, with slight deviations to the right in some cases, downward in others, to the right and downward in others and upward in 1 case. The direction of SffQRS in both diseases is explained by the anatomic characteristics, especially by the type of right ventricular hypertrophy, which is different for tetralogy and trilogy. In tetralogy of Fallot the mean thickness of the anterior wall of the right ventricle in the areas near the interventricular septum was 4.88 mm. for the apical region and 4.86 mm. for the infundibular region. In trilogy, the values were similar for the apical region (mean thickness 4.99 mm.) but in the infundibular region the mean parietal thickness of the anterior wall of the right ventricle was practically twice (9 mm.) the mean value found for the same region in tetralogy of Fallot (5.5 mm.). It can be stated that these areas with a greater thickness give rise to greater electromotive forces which predominate during ventricular depolarization and that they displace the mean spatial axis of QRS shifting its direction especially forward. THE
AMERICANJOURNALOFCARDIOLOGY
Tetralogy EMBRYOLOGIC
vs. Trilogy
DIFFERENCES
The different behavior of the anterior wall of the infundibulum of the right ventricle in tetralogy and trilogy of Fallot can be accounted for by the embryology of these conditions. In tetralogy there is an unequal partition of the truncoconus at the expense of the pulmonary artery, which has a very narrow caliber, a pulmonary valvular ring also of reduced diameter and a narrow infundibulum. The crista supraventricularis, which is an outgrowth of the displaced truncoconal septum, is also displaced forward and to the left, thereby narrowing the infundibulum. The result is a narrow infundibulum, often irregular and malformed and commonly exhibiting fibrosis of the crista and thin walls. The barrier formed by the infundibulovalvular stenosis is overcome by the hypertrophy only of the free walls of the inflow chamber of the right ventricle, whereas the walls of the malformed infundibulum are incapable of such a marked hypertrophic reaction. By contrast, in trilogy of Fallot the embryologic alteration affects only the primordia of the sigmoid pulmonary valve cusps, thus giving rise to thick valves with fusion of their commissures and with a very narrow valvular orifice. The infundibulum, on the other hand, is normally formed. The barrier constituted by the pulmonary valvular stenosis is overcome by the hypertrophy of both the infundibular walls and the crista supraventricularis and the free walls of the inflow chamber of the right ventricle. HEMODYNAMIC
DIFFERENCES
AND
THE
ELECTRO-
CARDIOGRAM
From a hemodynamic standpoint, in tetralogy there are three anatomic possibilities for an outlet for the blood under pressure within the right ventricle during systole: the narrow pulmonary orifice, the interventricular septal defect and the overriding aorta. Actually, blood does not flow from the right ventricle to the left through the ventricular septal defect. Rather, both chambers behave hemodynamically as a common chamber with equal intraventricular right and left ventricular ejection is pressures; simultaneous into the aorta. The flow contributed by each ventricle depends on the severity of the infundibulovalvular pulmonary stenosis and on the lesser or greater degree of dextroposition of the aorta. Because in tetralogy both ventricles function as a single chamber that empties fundamentally into the aorta the right intraventricular pressure is equal to left VOLUME
21,
JUNE
1968
of Fallot
783
intraventricular pressure and to systemic arterial pressure. In trilogy of Fallot blood is under great systolic right ventricular pressure and has only one outlet, i.e., the narrow pulmonary valve. The right intraventricular pressure increases proportionately to the degree of valvular obstruction and is often higher than systemic pressure. This extreme right intraventricular pressure in trilogy of Fallot is expressed electrocardiographically by alterations of the ventricular repolarization waves, characterized by T waves of the ischemic type that are deep, symmetric and peaked. There is a small group of cases (8 in our series of 26) in which tetralogy behaves electrocardiographically as does trilogy, exhibiting tall R w:ves in several precordial leads and with an SAQRS pointing predominantly forward. This is probably due to variations in the anatomic patterns. Indeed, when a small interventricular septal defect, a slight overriding of the aorta and a marked pulmonary stenosis coexist, tetralogy becomes similar to trilogy, both anatomically and hemodynamically. In cases of tetralogy with atresia of the pulmonary artery, the type of right ventricular hypertrophy differs very little from that found in classic tetralogy. The electrocardiographic pattern is also similar in both groups. In cases of interventricular septal defect, stenosis of the pulmonary valvular ring and agenesis of the pulmonary sigmoid valve cusps the hypertrophic pattern is similar to that seen in trilogy. But in this group the ventricular septal defect is an outlet of the blood from the hypertensive right ventricle, and the pressure is not as high as in cases of pulmonary stenosis with intact interventricular septum. This finding is expressed in the electrocardiogram by the lower incidence and severity of primary changes of the T wave. SUMMARY 1. An electrocardiographic-anatomic correlation of cases of tetralogy of Fallot and pulmonary stenosis with intact interventricular septum (trilogy of Fallot) was made, in an attempt to explain the electrocardiographic similarities and differences between these two malformations on the basis of the anatomic findings. 2. Fifty autopsy specimens were studied: 39 were cases of tetralogy, 9 were cases of pulmonary stenosis with intact interventricular septum and 2, stenosis of the pulmonary valvular ring
Mufioz-Armas et al.
784
with interventricular septal defect and agenesis of the pulmonary sigmoid valve cusps. An electrocardiogram was available for 39 cases. 3. The anatomic findings showed that hypertrophy of the right ventricle was homogeneous and generalized in pulmonary stenosis with intact interventricular septum; in tetralogy it was limited to a hemispheric area located at the union of the upper and the middle third of the The left ventricle in right border of the heart. tetralogy was generally hypotrophic; it was normal in pulmonary stenosis with intact interventricular septum. 4. In tetralogy of Fallot, .kQRS in the frontal plane pointed downward and to the right; in SAQRS trilogy it tended to be more horizontal. in the majority of instances of tetralogy pointed to the right, forward and downward ; in pulmonary stenosis with intact interventricular septurll it generally pointed predominantly forward. In the precordial leads the greater number of cases of tetralogy showed a predominant R wave only in Vi; in the majority of cases of trilogy, the predominant R wave was recorded beyond Vi. The T wave tended to be positive in the precordial leads in tetralogy of Fallot and negative in the right precordial leads or in all of the precordial leads in trilogy. 5. The sequence of the activation process of the ventricular walls in both malformations is discussed in relation to the different hypertrophic patterns and to the position of the interventricular septum with respect to the frontal plane.
REFERENCES V., NAVARRO, F., PEREIRA, D. and REINIIOLD, M. Communicaciones interventriculares en las cardiopatias congtnitas. Cardiologia., p. 1. SODI-PALLARES, D., editor. Mexico City, 1961. Interamericana, S.A. DE LA CRUZ, M. V. and DA ROCHA, J. P. Analisis embriol6gico de la tetralogia de Fallot, de complejo de Eisenmenger y de la transposicibn de 10s grandes vasos. Arch. Inst. cardiol. MLxico, 25: 699, 1955. ESPINO VELA, J. Elementes de diagnostico diferencial entre tetralogia y trilogia de Fallot. Principia cardiolbgica, 2: 52, 1955. ESPINOVELA, J. Malformaciones Cardiovasculares Congtnitas, p. 163. Mexico City, 1959. Edici6n de1 Instituto National de Cardiologia. DE LA CRUZ, M. V. Revisi6n de una teoria ontogenCtica sobre malformaciones cong6nitas troncoconales. Arch. Inst. cardiol. ML&o, 31: 509, 1961.
1. DE
2.
3.
4.
5.
LA
CRLJZ, M.
6. DE LA CRUZ, M. V. and DA ROCHA, J. P. An ontogenic theory for the explanation of congenital malformations involving the truncus and the corms. Am. Heart J., 51: 782, 1956. 7. DE LA CRUZ, M. V., ANSELMI, G., ROMERO, A. and MONROY, G. A qualitative and quantitative study of the ventricles and great vessels of normal children. Am. Heart J., 60: 675, 1960. 8. SODI-PALLARES, D. New Bases of Electrocardiography, p. 382. St. Louis, MO., 1956. C. V. Mosby. 9. SODI-PALLARES,D., BISTENI,A. and MEDRANO, G. .4. Electrocardiograffa y Vectocardiograffa Deductivas. Mexico City, 1964. La Prensa Mtdica Mexicana. 10. MEDRANO, G. A., SOTOMAYOR, A. and SODI-PALLARES, D. Nuevas investigaciones sobre la activacidn de1 tabique interventricular en condiciones normales y con bloqueo de rama. III. Estudio de1 tercio medio de1 tabique. Porciones anterior y media. Arch. Inst. cardiol. M&ico, 27: 609,1957. 11. PEISALOZA,D. and TRANCHESI,J. The three main vectors of the ventricular activation process in the normal human heart. I. Its significance. Am. Heart J., 49: 51, 1955. 12. BISTENI, A., TESTELLI, M., DE MICHELI, A., and MEDRANO, G. A. La activation ventricular y las morfologias unipolares en condiciones normales y en 10s bloqueos de rama. In Ref. 1, p. 131. 13. MEDRANO, G. A., BISTENI, ‘4, BRANCA.CO,R. W., PILEGGI,F. and SODI-PALLARES,D. The activation of the interventricular septum in the dog’s heart under normal conditions and in bundle branch block. Bull. New York Acad. SC., 65: 804, 1957. 14. MEDRANO, G. A., PILEGGI, F., BISTENI, A., DE MICHELLI, A. and SODI-PALLARES, D. Nuevas investigaciones sobre la activacibn de1 tabique interventricular en condiciones normales y con bloqueo de rama. V. Estudio de1 tercio inferior de1 tabique. To be published, 15. SODI-PALLARES, D., PIL~GGI, F., CISNEROS, F., GINEFRA, P., PORTILLO, B., MEDRANO, G. A. and BISTENI, A. The mean manifest electrical axis of the ventricuar activation process (AQRS) in congenital heart disease: A new approach in electrocardiographic diagnosis. Am. Heart J., 55: 681, 1958. 16. MEDRANO, G. A., DE MICHELLI, A., HERTAULT, J. and SODI-PALLARES, D. La activaci6n de la cresta supraventricular en el corazon de1 perro. Arch. Inst. cardiol. M&co, 30: 432, 1960. 17. SODI-PALLARES, D., PORTILLO, B. CISNEROS, F., DE LA CRUZ, M. V. and ACOSTA, A. R. Electrocardiography in infants and children. Pediat. Clin. North America, 14, 871, 1958. 18. PORTILLO, B. and SODI-PALLARES, D. Semiologia electrocardiogrifica de la hipertrofia ventricular y sobrecarga sist6lica de1 ventriculo derecho en 10s padecimientos congenitos de1 corazbn. Principia cardinlbgica, 6: 231, 1959.
THE AMERICANJOURNALOF
CARDIOLOGY