Download Tunnel Subaortic Stenosis

Tunnel Subaortic Stenosis
Left Ventricular Outflow Tract Obstruction Produced by
Fibromuscular Tubular Narrowing
BARRY J. MARON, M.D., DAVID R. REDWOOD, M.D., WILLIAM C. ROBERTS, M.D.,
WALTER L. HENRY, M.D., ANDREW G. MORROW, M.D., AND STEPHEN E. EPSTEIN, M.D.
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SUMMARY The clinical and morphologic features of tunnel subaortic stenosis, an unusual form of obstruction to left ventricular
outflow, are described in 11 patients. Although patients with tunnel
subaortic stenosis demonstrate a variety of cardiovascular malformations, the most characteristic anatomic feature is fibromuscular
tubular narrowing of the outflow tract that remains relatively unchanged during the cardiac cycle. The aortic anulus was abnormally
small in six of the 11 patients, including one who also had a hypoplastic ascending aorta. Evidence of a small mitral orifice was present
in two patients, and two other patients had asymmetric septal hypertrophy. Although operation was successful in significantly reducing
the outflow gradient in two of the seven operated patients, all seven
patients had gradients of 50 mm Hg or more at the most recent postoperative evaluation. Three patients (two with previous operation)
died suddenly; each of these patients had mild or no symptoms.
Because of the apparent ineffectiveness of current operative methods
in patients with tunnel subaortic stenosis, it is important to differentiate this condition from obstructions to left ventricular outflow.
THE CLINICAL AND PATHOLOGIC FEATURES of
conditions producing fixed obstruction to left ventricular
outflow are well known.`8 In particular, fixed subaortic
stenosis produced by a discrete fibrous membrane located
just under the aortic valve has been the subject of numerous
reports.'0 Subvalvular membranes of this type can be excised readily at operation, usually with relief of outflow
obstruction.4' 6,8-10 However, another type of fixed subaortic stenosis has been recognized in which there is considerably more diffuse fibromuscular narrowing;2' 4, 6 8, 10-12
in our experience, this entity has very different clinical implications. In an attempt to better define this type of left ventricular outflow obstruction, which has been referred to as
"tunnel aortic stenosis,"'4 we have reviewed and analyzed
the clinical, pathologic, and operative findings of 11 patients
with this condition.
Materials and Methods
Selection of Patients
The operative and necropsy records of the National Heart
and Lung Institute (NHLI) from 1958 to 1975 were
reviewed. Eleven patients in whom the hemodynamic, angiographic, echocardiographic, operative or necropsy findings
suggested the presence of diffuse obstruction to left ventricular outflow were selected for analysis. In these patients the
diagnosis of tunnel subaortic stenosis was made initially by
cardiac catheterization and angiography (seven patients), at
operation (three patients), or at necropsy (one patient). Certain clinical findings in five of the 11 patients in this investigation have been described briefly in other reports from
this institute.2' 4, 6i 1'
patients (L.W. and A.G.) had only a single evaluation. At
the initial cardiac evaluation (the first admission either to
the NHLI or another institution) the patients ranged in age
from 5 to 22 years (mean 9); at the latest cardiac evaluation
or at the time of death patients ranged in age from 7 to 34
years (mean 17). The period of follow-up ranged from one to
18 years (mean 8). Seven patients were female; four were
male. History and physical examination, electrocardiogram
and chest radiograph were obtained at both the initial and
most recent cardiac evaluations; phonocardiograms and indirect carotid pulse tracings were obtained only at the initial
evaluation. Left and right heart hemodynamic studies and
left ventricular angiography were performed at the initial
evaluation in each of the 11 patients. In eight of the 11
patients repeat cardiac catheterization and angiographic
studies were performed, including postoperative studies in
seven patients.
Analysis of Patients
Clinical data from the initial and most recent cardiac
evaluations were analyzed for nine patients. Two other
From the Cardiology Branch, the Section of Pathology and the Clinic of
Surgery, National Heart and Lung Institute, National Institutes of Health,
Bethesda, Maryland.
Address for reprints: Barry J. Maron, M.D., National Heart and Lung
Institute, Cardiology Branch, Bldg. 10, Room 7B-15, Bethesda, Maryland
20014.
Received April 1, 1976; revision accepted April 27, 1976.
404
Echocardiographic Studies
One-dimensional echocardiographic studies were obtained at the most recent cardiac evaluation in six patients
(postoperatively in three of these patients) utilizing techniques previously described;'2 two-dimensional echocardiographic studies'4 were performed in four of the six patients.
In addition, one-dimensional echocardiograms were obtained in first degree relatives (the parents and three siblings)
of patient R. D., who had disproportionate ventricular septal
thickening in association with tunnel subaortic stenosis.
Operative Procedures
Ten of the 11 patients in this study underwent operation in
an attempt to reduce left ventricular outflow obstruction;
four of the ten patients had two operative procedures. In
nine of the ten patients subaortic muscle, fibrous tissue, or
both were removed at each operation. One other patient (T.
Cap.) had ligation of a patent ductus arteriosus and resection of a coarctation of the aorta six years prior to attempted
correction of tunnel subaortic stenosis by a left ventricular
apex to descending thoracic aorta anastomosis. Two of the
ten patients died at operation, K.W. at the time of her second operation and T. Cap. at the time of her apical-aortic
405
TUNNEL SUBAORTIC STENOSIS/Maron et al.
anastomosis. An operation
G.G.
was
not
performed in patient
Necropsy Studies
Necropsy studies were performed in five patients, aged 7
23 years (average 14). Measurements were made of the
maximum thicknesses of the ventricular septum, and
posterior left ventricular free wall, the posterobasal left ventricular free wall (directly behind the posterior mitral
leaflet), and the right ventricular wall. Blocks of myocardium were taken from the ventricular septum and left
and right ventricular free walls in each heart. The tissue
specimens were fixed in 10% formaldehyde, processed,
embedded in paraffin, sectioned at 6g thickness and stained
with hematoxylin and eosin. The severity and extent of disorganization of cardiac muscle cells was assessed by light
microscopy in each tissue block."15
to
Results
tional class I), seven patients were in functional class II, and
one patient was in functional class III (table 1). The most
common symptoms were dyspnea or fatigue with exertion
(six patients), chest pain that was not typical of angina pectoris (four patients), typical angina pectoris (one patient)
and syncope (three patients). One patient (T. Cap.) had
evidence of left and right ventricular failure and one patient
(G.G.) had a history of documented paroxysmal atrial
fibrillation. The age at onset of symptoms ranged from one
to 29 years (median seven).
Five patients have died during the period of observation.
Of these, two died at operation (K.W. and T. Cap.) and
three (D.A., G.G., and R.D.) died suddenly and unexpectedly. Patients D.A. and R.D. died during vigorous activity seven and 13 years after operation, respectively;
patient G.G. (who did not have an operation) died during
mild exertion. Patients D.A. and R.D. were asymptomatic
and G.G. was in functional class II at the time of death.
Physical and Phonocardiographic Findings
Clinical Status
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At the time of initial cardiac evaluation three patients
asymptomatic (New York Heart Association func-
were
11
Physical and auscultatory findings were similar among the
patients. Each patient had a prominent, sustained left
TABLE 1. Clinical and Hemodynamic Data in 11 Patients with Tunnel Subaortic Stenosis
Age
(yrs)
Patient
5
I (Cath-1)
K.W.
5
Operation-1
9
Cath-2
9
Operation-2
9
Death
I (Cath-1)
5
D.A.
5
Operation-1
6
Cath-2
6
Operation-2
9
II (Cath-3)
13
Death
6
T. Cap. I (Cath-1)
7
Operation
7
Death
I (Cath-1)
6
M.G.
6
Operation
9
II (Cath-2)
I (Cath-1)
6
G.G.
16
Cath-2
20
Death
7
I (Cath-1)
T.C.
7
Operation
9
Cath-2
II (Cath-3)
18
I (Cath-1)
9
R.D.
10
Operation
10
Cath-2
23
Death
9
I (Cath-1)
L.W.
10
Operation
10
I (Cath-1)
A.G.
10
Operation
I (Cath-1)
16
M.S.
Operation-1 16
17
Cath-2
31
Cath-3
Operation-2 31
32
Cath-4
34
II
I (Cath-1)
22
A.D.
23
Operation
23
Cath-2
F
FC*
1
M
3
2
Sex
Age onset
symptoms
(yrs)
CI
(L/min/m2)
RV
S/D
9
2.8
20/1
4.1
-
-
-
-
5.8
28/3
28/12
6.0
24/4
24/8
4
PA-RV
PSG
1
19/12
PA
S/D
Mean
LAP
LVSP LVEDP
LV-SA
PSG
Circumstances
ECG
(11)
220
-
120t
LVH
-
-
190
11
95
LVH
-
19
160
19
60
LVI
-
240
9
130
(12)
180
9
(28)
240
30
65
140$
LBBB
F
1
3
1
3.6
75/10
75/52
0
0
M
3
2
2
5.4
26/6
24/14
2
(14)
200
14
110§
M
1
1
19
-
35/4
60/4
33/11
25/12
2
35
(13)
14
240
200
20
10
140
110
60/3
30/10
30
(10)
245
32
107
LVIH
RAE
LVH
RAE
2
F
M
2
2
2
2
RBBB,
LVH
_
27/3
26/9
1
5
250
18
160¶
LVH
-
-
24/6
2
-
-
(11)
10
135
185
210
10
14
10
30
60
120
LBBB
LVH
-
-
-
-
-
320
10
200
2
5.1
30/3
30/15
0
(15)
245
20
150
LVH
LVH
7
-
-
22/10
1
2
F
2
9
4.3
40/11
37/18
3
(20)
220
20
110
LVH
F
1
29
-
-
-
-
16
275
18
155
LVH
-
13
165
230
23
65
93
-
155
260
18
50
16
150**
F
2
2
14
1.7
2.0
24/9
-
3.6
22/7
22/12
-
0
(10)
Suddenly while
swimming
At operation
Suddenly while
walking
upstairs
Suddenly while
F
-
At operation
LVHI
4.1
2.8
1
of death
IVCD
LVH
LVH
playing
basketball
150
14
260
4.8
24
1
II
*Functional class at time of death signifies patient's symptomatic status during period of time just prior to death.
mm Hg subaortic pressure gradients.
t55 mm Hg peak systolic pressuire gradient across aortic valve; also, 25 mm Hg and 40 mm
Hg subaortic pressure gradients.
50 mm Hg peak systolic pressure gradient across aortic valve; also, 40 mm Hg and 50
§40 mm Hg peak systolic pressure gradient across aortic valve; also, 35 mm Hg and 35 mm Hg subaortic pressure gradients.
¶10 mm Hg peak systolic pressure gradient across aortic valve; also, 150 mm Hg subaortic pressure gradient.
**45 mm Hg peak systolic pressure gradient across aortic valve; also, 105 mm Hg subaortic pressure gradient.
I = initial cardiac evaluation; Cath-1 = first cardiac catheterization; Cath-2 = second cardiac catetherization; II = latest cardiac evaluation; ( )
pulmonary arterial wedge pressure; - = data not available.
Abbreviations: CI = cardiac index; ECG = electrocardiogram; FC = functional class (New York Heart Association); IVCD = intraventricular conduction
= left ventricular hypertrophy;
defect; LAP = left atrial pressure; LBBB = left bundle branch block; LVEDP = left ventricular end-diastolic pressure; LVH
LVS left ventricular systolic pressure; PA = pulmonary artery; PSG = peak systolic gradient; RBBB = right bundle branch block; RV = right ventricle;
SA = systemic artery; S/D = systolic/diastolic pressure; RAE = right atrial enlargement.
406
CI RCULATION
VOL 54, No 3, SEPTEMBER 1976
E
E
0.
LV
BODY
1
LV OUTFLOW
a
1-
AORTA
FIGURE 1. Pressure tracing recorded in patient (T. Cap.) with tunnel subaortic stenosis during withdrawal of an endhole catheter from the left ventricle to the aorta. Systolic pressure in the body ofthe left ventricle was 240 mm Hg. Three
distinct pressure gradients were present; two within the left ventricle (40 mm Hg and 50 mm Hg) and one across the aortic
valve (50 mm Hg). Simultaneously recorded electrocardiogram is shown at the top.
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ventricular impulse and a harsh, grade 3-4/6 systolic ejection murmur that was loudest at the second to fourth left intercostal space; in nine patients a grade 1-3/6 early diastolic,
decrescendo, blowing murmur was also present. The second
heart sound split normally with the respiratory cycle in two
patients, split paradoxically in three patients, and was single
in six patients. A third heart sound was present in five
patients and a fourth heart sound was present in two
patients. A systolic ejection click was recorded by phonocardiography in one patient.
The left ventricular ejection time (corrected for heart rate)
was prolonged compared to normal standards"7 18 in seven
of the eight patients studied (range 350 to 440 msec; normal
280-340 msec) and was normal in one. The left ventricular
upstroke time (corrected for heart rate) ranged between 50
and 180 msec (normal 60-110 msec) and was abnormally
short"9 in one patient. The contour of the peripheral arterial
pulse (evaluated by either indirect carotid pulse tracing or
direct intra-arterial pressure recording in the aorta or
brachial artery) was, however, normal in each patient with
tunnel subaortic stenosis.
gradient measurements ranged from 50
Hg (median 96). The outflow gradient did not
change appreciably (<25 mm Hg) in three patients, increased in two by 30 and 80 mm Hg, and decreased in two by
100 and 105 mm Hg. However, in no patient was the outflow
gradient less than 50 mm Hg at the time of the latest postoperative cardiac evaluation.
operative
pressure
to 200 mm
200r
180F
160h
14C
E
E
z
12C _
w
CE
Hemodynamic Findings
The hemodynamic data for the 11 patients with tunnel
subaortic stenosis are summarized in table 1. At the initial
(preoperative) evaluation, each patient had a marked peak
systolic pressure gradient between the left ventricle and aorta (60 to 160 mm Hg; median 120). In four of these patients,
a single pressure gradient was present in the subaortic area.
Two other patients showed, in addition to the subaortic
gradient, a second gradient across the aortic valve (10 mm
Hg in patient T.C. and 45 mm Hg in patient A.D.). In each
of three other patients (T. Cap., K.W. and M.G.), gradients
were recorded at three levels of the left ventricular outflow
tract; one gradient across the aortic valve and two separate
gradients in the subaortic area (table 1, fig. 1). Left ventricular end-diastolic pressure (recorded in ten patients at the
initial evaluation) was elevated (> 12 mm Hg) in eight
patients and normal in two patients.
Changes in left ventricular outflow gradient produced by
operation in seven patients (for whom both preoperative and
postoperative hemodynamic data are available) are summarized in table 1 and figure 2. The most recent post-
3r.
0
-J
LL.
soII_
HS8C
0
:
:
I-J
bUf __
40F
20C
I
II
PREOPERATIVE
POSTOPERATIVE
FIGURE 2. Preoperative and postoperative left ventricular outflow
gradients in seven patients with tunnel subaortic stenosis. *Patients
who survived two operations. In these patients with two operations
the initial preoperative measurement and the most recent postoperative measurements are given. t = died. R.D. died suddenly 13
years after operation; K. W. died at her second operation, four years
after the initial operation; T. Cap. died at operation, seven years of
age.
TUNNEL SUBAORTIC STENOSIS/Maron et al.
Angiographic Findings
The angiographic appearance of the left ventricular outflow tract was similar in each patient (fig. 3). The
characteristic angiographic feature (that was usually
visualized best in the posteroanterior projection) was a long
tubular narrowing of the left ventricular outflow tract extending proximally from the aortic anulus. This narrowing
was relatively fixed (i.e., did not change appreciably in
diameter during the cardiac cycle) in each patient. In six
patients (M.G., K.W., D.A., A.D., A.G., and M.S.) the left
ventricular cavity was greatly reduced in size during endsystole with obliteration of the apex (fig. 3B and 3D), an
angiographic feature similar to that frequently observed in
patients with ASH.'9 22
In each patient the aortic valve leaflets appeared
thickened. Moderate aortic regurgitation was documented
by aortography in two patients (A.G. and L.W.). The ascen-
407
ding aorta was normal-sized or slightly dilated in ten
patients and markedly reduced in size in one (T. Cap.; figs.
3E, F). In addition, a mild coarctation of the aorta (the
residua of a coarctation resection performed six years
previously) was present (fig. 3E). One patient (M.S.) showed
moderate mitral regurgitation.
Electrocardiograms
Electrocardiograms obtained at the initial evaluation were
similar in each patient and showed marked left ventricular
hypertrophy with T wave inversion in the left precordial
leads as well as diffuse ST segment and T wave abnormalities. At the latest evaluation, electrocardiograms were
essentially unchanged in six patients; however, three other
patients developed conduction defects following operation
(left bundle branch block in two and intraventricular conduction defect in the other).
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FIGURE 3. Left ventricular angiocardiograms demonstrating the anatomic abnormalities in tunnel subaortic stenosis.
A, B and C from patient M.G. D from patient A.G.; E and F from patient T Cap. A) Angiocardiogram in diastole
(posteroanterior view) showing long tubular narrowing of the left ventricular outflow tract (arrowv) and markedly
thickened left ventricular free wall. B) A ngiocardiogram in end-systole (posteroanterior view) showing long tubular
narrowing of the left ventricular outflow tract that is relatively unchanged from that seen in diastole (compare with 3A)
and obliteration of the left ventricular apex. C) Angiocardiogram in systole (lateral view) showing narrowing of the left
ventricular outflow tract (arrows). D) Angiocardiogram in systole (posteroanterior view) showing long narrowing of left
ventricular outflow tract that appears eccentrically located and obliteration of the apex. E) Angiocardiogram in diastole
(posteroanterior view) showing dilated, irregularly shaped left ventricular cavity, narrowed outflow tract, hypoplasia of
the ascending aorta, mild coarctation of the aorta (arrow) and dilatation of the coronary arteries. F) Angiocardiogram in
systole (posteroanterior view) showing narrowing of the left ventricular outflow tract that is unchangedfrom that seen in
diastole (compare with 3E).
408
CIRCULATION
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Uit
;
VOL 54, No 3, SEPTEMBER 1976
0tii00000t2
FIGcURE 4. Echocardiographic tracing shown at three levels of the heart, representing selections from a continuous scan
from mitral valve to aorta. This record is from patient T C. with tunnel subaortic stenosis, II years after operation, an
outflow gradient of 60 mm Hg was demonstrated shortly after the echo was obtained. A) at the level of the tips of the
mitral leaflets- B) cephalad to the mitral valve in the subaortic area (i.e., the left ventricular outflow tract), C) at the level
of the aortic valve. In A the distance between the ventricular septum and mitral valve at onset of systole is normal and the
mitral valve appears to be normally positioned in the left ventricular cavity. The ventricular septal thickness is only
slightly increased over normal; this may be due to the fact that the echocardiogram was taken aJter operation (during
which large amo unts of m uscle were resected from the left ventricular outftlow tract). A t the level sho wn in C, the ao rtic
anulus is normal-sized. At the level shown in B, however, the left ventricular outflow tract is markedly narrowed.
Ao V =aortic valve leaflet; A WOT an terior wall of left ventricular outflow tract; (i.e., the cephalad portion of the ventricular septum); A WA = anterior wall of aorta; EKG electrocardiogram; LA = left atrial cavity, L VOT - left ventricular outflow tract; MV = mitral valve; PW = posterior left ventricular free wall; PWA posterior wall of aorta;
PWOT = posterior wall of left ventricula r outflow tract (i.e., the cephalad p ortio n of the mitral valve), R V right vientricular cavity; RVO right ventricular outflow tract; VS ventricular septum. Calibration mark equals 10 mm.
=
=
=
=
Chest Radiographs
At initial cardiac evaluation, the heart size as determined
by chest radiograph was normal (cardiothoracic
ratio 0.55) in seven patients and enlarged in four patients.
Pulmonary venous markings were increased in two patients.
At the most recent evaluation, the heart size had increased in
one patient (M.S.) and decreased in another (G.G.).
=
Echocardiographic Findings
In the three patients studied preoperatively (T. Cap., A.G.
and L.W.) and the one patient who did not undergo operation (G.G.), one or two-dimensional echocardiograms
showed the left ventricular outflow tract to be markedly
narrowed. The aortic anulus* was abnormally small" in T.
*We have used the term aortic anulus to refer to that portion of the aorta at
the level of the cephalad extension of the commissures, This area of the aorta
is also known as the sinotubular junction.
Cap. and L.W. and normal-sized in G.G. and A.G. In addition, two other patients (A.D. and T.C.) were studied by one
and two-dimensional echocardiography eight and 11 years
after operation, respectively. Both of these patients also
showed a markedly narrowed left ventricular outflow tract
(fig. 4); the aortic anulus was abnormally small in A.D. and
normal-sized in T.C.
In five of the six patients studied echocardiographically
the ventricular walls were concentrically thickened. One
patient (G.G.) had echocardiographically documented
asymmetric septal hypertrophy (ASH) (ventricular septal
thickness of 28 mm, posterobasal left ventricular wall
thickness of 20 mm and septal-free wall ratio of 1.4). In addition, the mitral leaflets were anteriorly displaced in the left
ventricular cavity at the onset of systole (fig. 5), a finding
previously reported in patients with obstructive ASH24 as
well as in patients with other conditions."' 26 Abnormal
systolic anterior motion of the mitral valve occurred in
TUNNEL SUBAORTIC STENOSIS/Maron
et
409
al.
leaflet showed a reduced E-F slope. In addition, the presence
of an abnormally decreased and relatively fixed distance
between the anterior and posterior mitral leaflets during
suggested
diastole
the presence of
a
reduced mitral valve
orifice in two patients (T. Cap. and A.D.). Although cardiac
catheterization data in both these patients suggested that
hemodynamically significant mitral stenosis was not present, direct operative examination of the mitral valve in T.
Cap. revealed the mitral orifice to be abnormally small. The
transverse left atrial dimension was normal23 in three of the
six
studied. The left atrium
patients
mm) in
one
patient (T. Cap.)
was
decreased in size (20
and increased in
patient
G.G.
(49 mm) and patient A.G. (35 mm). The echocardiographic
assessment
echocardiograms
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FIGURE 5. Echocardiogram from patient G. G. with tunnel subaortic stenosis showing disproportionate thickening of the ventricular septum (VS) with respect to the posterobasal left ventricular
wall (PW). The mitral valve is displaced forward in the ventricular
cavity at the onset of systole. Calibration mark equals 10 mm.
patient
R.D.
was con-
not
have
had normal-sized left atria at necropsy.
One-dimensional
of
Cap. and 6.6.
patients who did
of left atrial size in T.
firmed at necropsy. Three other
echocardiogram obtained
in the father
(who had disproportionate ventricular septal
thickening in addition to tunnel subaortic stenosis) showed
asymmetric septal hypertrophy with a septal thickness of 23
mm, posterobasal left ventricular wall thickness of 12 mm
and septal-free wall ratio of 1.9. Echocardiograms performed on the mother and two siblings of patient R.D. were
normal. Studies on the family members of patient G.G.
could
not
be performed.
Operative Findings and Procedures
patient G.G. (fig. 5), as well as in patient A.G. who did not
have disproportionate septal thickening. In each of the six
patients with echocardiographic studies, the anterior mitral
The findings at operation and the operative procedures
performed in ten of the 11 patients with tunnel subaortic
stenosis are summarized in table 2. In each of nine patients
TABLE 2. Operative Data in Ten Patients with Tunnel Subaortic Stenosis
Patient
Thickened
aortic
valve
leaflets
Age
(yrs)
K.W.t
D.A.t
9
6
T. Cap§
7
Operative findings
Thickened
mitral
Small
aortic
valve
anulus
+
+
0
0
leaflets
+
+
Operative Procedures
Diffuse
narrowing
of LVOT*
+
+
-
-
Resection of fibrous
tissue from LVOT
Resection of
ventricular muscle
from LVOT
Aortotomy
+
+
+
+
(small amount)
+
0
0
0
Other
Left ventriculotomy
0
Anastomosis between
LV apex and
descending thoracic aorta
utilizing a dacron
prosthesis incorporating a porcine
xenograft
M.G.
6
+
0
T.C.
R.D.
7
10
0
+
+
M.S.¶
A.G.
31
23
10
+
0
+
L.W.
10
+
A.D.
+
+
+
+
+
-
0
+
0
0
+
+
+
+
+
+
+
+
+
+
+
(small amount)
+
+
+
0
0
0
+
0
+
Excised large amt. LV myotomyof thickened
ectomy as
performed in
endocardium
ASH27
overlying LV
+
0
Left ventriculotomy
Incision inito fibrous
tissue
+
+
+
+
thicik fibrous and muscular tissue forming a ring around LVOT, involving the anterior mitral leaflet and extendling about 2 cm proximal to
tA previous operation was performed at another institution at age 5 years; subaortic fibrous tissue was resected and left ventrictular myotomy performed.
fib)rous tissue was resected.
tA previous operation was performed at another i nstitution a t age1 5 years; a small amouint of subaortic
§A previous operation wvas performed at another institution at age year; a patent Iuictus arteriosus wias ligatedl and coarctation of aorta repaired.
¶A previous operation 'was performed at NIHLI at age 16 years; subaortic fibrous tissue was resected alnd an aortic valvotomy performed.
- = Not described.
+ = Performed or present.
0 = Not performed or not present.
Abbreviations: LV left ventricular; LVOT = left ventricular outflow tract; VS ventricular septum; amt amount.
*A long area of
the aortic anulus.
=
=
=
410
CI RCU LATION
VOL 54, No 3, SEPTEMBER 1976
TABLE 3. Necropsy Findings in Five Patients with Tunnel Subaortic Stenosis
Age
Heart wt
(NL limit)28
Max
VS
Max
LVFW
Wall thickness (mm)
VS-LVPB
ratio
LVPB*
Pulmonic
(NL range)29,
4.0
(4.1-6.5)
6.5
Patient
(yrs)
Sex
K.W.
(A67-14)
D.A.
(A72-115)
T. Cap.
(A74-125)
10
F
325g
17
17
17
1.0
4
13
M
(200)
690g
(300)
23
23
23
1.0
6
7
F
240g
(150)
16
16
16
1.0
10
G.G.
20
M
830g
(350)
35
35
30
1.2t
10
720g
30
(A73-109)
R.D.
M
23
(5.8X6.6)
5.0
(3.0-6.2)
7.5
(7.0-9.0)
20
20
1.5
(350)
(A74-331)
Valve circuLmference (cm)
Aortic
U
(NL range)29, s
Max
RV
6
3.2
(3.6 6.0)
4.5
(4.8 6.4)
2.3
(3.2-5.6)
6.0
Size
LA
NL
NL
1
(6.0-7.5)
7.0
4.3
(7.0-9.0)
(6.0-7.5)
NL
modG rading system: 0 = normal cellular arrangement or absence of myocar(dial scarring; 1+
mild cellular disorganization or mild myocardial scarring; 2+
erate cellular disorganization or moderate myocardial scarring; 3+ = severe cellular disorganization or severe myocardial scarring.
*Measured behind the posterior leaflet of the mitral valve.
[Although the septal-free wnall ratio obtained at necrospy in this patient (i.e., 1.2) 'was not indicative of disproportionate septal thickening, tle septal-free wnall
ratio obtained by echocardiography (in diastole) wnas 1.4. In patients wnithi disproportionate septal thickening, the posterobasal left ventricuilar xvall thickens considerably more than the ventricular septum in systole and postmortem hearts are often fixed in the systolic phase of the cardiac cycle. Suich considerations probably
explain the disparity between the septal-free wall ratios obtained in this patient (luring life as compared to those obtained at necropsy.
=
- decreased.
- increased;
left ventricular papillary muscles;
left ventricular outflow tract; LV pap
left ventricular; LVFW - left ventricular free wall; LVOT
Abbreviations: LV
w
ventricular septal; W t
LVPB - left ventricular posterobasal wall; max maximum; NL normal; RV rig ht ventricular; SE su bendocardiial; VS
weight.
=
=
=
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undergoing an operation in which the left ventricular outflow
tract was visualized and subaortic tissue was removed,
diffuse narrowing of the outflow tract extending for an estimated 2 cm proximal to the aortic valve was present. The
ventricular muscle in the outflow tract was greatly hypertrophied and was covered by a thick layer of fibrous tissue
that usually extended over the anterior mitral leaflet. In five
patients (K.W., D.A., M.G., A.G. and T.C.) both fibrous
tissue and underlying ventricular muscle was resected from
the left ventricular outflow tract. In three patients (M.S.,
L.W., and A.D.) only fibrous tissue was removed and in one
patient (R.D.) an incision was made into the fibrous tissue of
the outflow tract but no tissue was removed. The left ventricular outflow gradient increased after operation in R.D.
Necropsy Findings
The necropsy findings in five hearts with tunnel subaortic
stenosis are summarized in table 3 and illustrated by
representative examples in figs. 6-10. Heart weights uniformly were markedly increased compared to normal standards.28 The gross anatomic features of the left ventricular
outflow tract were similar in each of the five hearts. The out-
=
flow tract was markedly narrowed in an area extending
about I to 3 cm proximal to the aortic anulus (fig. 6B, 7C, 8,
9A-B, and 10). This relatively long area of narrowing was
associated with marked thickening of the ventricular muscle
(figs. 6B, 7C, 8, and 9A). The muscle in the left ventricular
outflow tract was covered by a thick layer of fibrous tissue
that invariably extended onto the anterior leaflet of the
mitral valve (figs. 9B and 10). In four patients (K.W., D.A.,
T. Cap., and R.D.) the aortic anulus was abnormally small
(figs. 6A, B, 7C, 8, 9A-B and 10) compared to normal standards;28" 2 the aortic valve leaflets showed fibrous thickening
in each patient (figs. 6A, 9B, and 10). In one patient (T.
Cap.) the ascending aorta was markedly reduced in size (fig.
7A). In addition, patient G.G. (who had a 35 mm Hg
systolic pressure gradient between the right ventricle and the
pulmonary artery) showed hypertrophy of the crista supraventricularis.
The left ventricular walls were markedly increased in
thickness in each patient. In four of the five patients the
thickening was concentric, i.e., the ventricular septal to
posterobasal left ventricular wall thickness ratio was < 1.3
(figs. 6B and 7C). In one patient (R.D.) disproportionate
FIGURE 6. Heart of patient K.W. (A67-14). A)
Bicuspid aortic valve viewed from above showing
considerable fibrous thickening of the leaflets. B)
Longitudinal cut showing the left atrium (LA),
thickened anterior (A) and posterior (P) mitral
leaflets, left ventricular (L V) free wall, right ventricular (RV) wall, ventricular septum (IVS) and
aorta. The left ventricular outflow tract and cavity
are markedly narrowed and the ventricular septal
thickness is equal to that of the left ventricular
free wall.
TUNNEL SUBAORTIC STENOSIS/Maron et al.
Thickened
aortic
valve
leaflets
TSmall
aortic
anulus
Thickn
mitral
valve
leaflets
Narrowed
Narred
scarred
411
Disorganization
Ventricular scarring
of cardiac
LVOT
VS
LVFXV
LVpap
RV
Vs
muscle cells
LVFW
EV
+
+
+
+
2+
2+
3+
0
0
0
0
+
+
+
+
1+
1+
1+
0
0
0
0
+
+
+
+
3+
1+
2+
3+
0
0
0
+t
0
+
+
2+
2+
3+
0
3+
0
0
+
+
+
+
3+
3+
2+
0
1+
0
0
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
thickening'3 of the ventricular septum was present (with a
ventricular septal to posterobasal left ventricular wall
thickness ratio of 1.5) (fig. 8).
Histologic examination of myocardium from the ventricular septum and ventricular free walls showed virtually all
cardiac muscle cells to be hypertrophied and normally
arranged with respect to each other in three of the five
patients. G.G. showed disorganization of hypertrophied cardiac muscle cells in the ventricular septum; disorganization
of cardiac muscle cells was not present in the left ventricular free wall of this patient. R.D., who had disproportionate ventricular septal thickening, showed only minimal
disorganization of cardiac muscle cells in the ventricular
septum.
Scarring of ventricular myocardium (including both
replacement and interstitial fibrosis) was present in all five
patients but was particularly marked in two (T. Cap. and
R. D.; fig. 7C). The scarring usually involved the ventricular septum and left ventricular free wall, always included
the papillary muscles, and was usually located in the subendocardial region.
Abnormalities of the intramural coronary arteries30 were
present in each patient. These abnormalities were focal and
usually consisted of both intimal proliferation and medial
hypertrophy; some involved arteries had narrowed lumens.
Abnormal intramural coronary arteries were present in
areas of scarring as well as in areas without scarring, were
generally more numerous in the ventricular septum than in
the left ventricular free wall, and were absent or rare in the
right ventricle or atria. The extramural coronary arteries in
each patient had wide-open lumens. The anatomic abnormalities in patients with tunnel subaortic stenosis (as determined by angiographic, echocardiographic, operative and
necropsy observations) are summarized in table 4.
FIGURE 7. Heart of patient T. Cap. (A 74-125).
A) Exterior view showing the ascending aorta to
be hypoplastic compared to the pulmonary trunk
(PT). R. A. right atrium. B) Exterior view of
=
heart showing the dacron prosthesis that was inserted into the apex of the left ventricle (L V) at
operation. RV right ventricle. C) Longitudinal
section of heart showing small left and right ventricular cavities, narrow left ventricular outflow
tract, ventricular septal (VS) thickness that is
equal to that oJ the left ventricular (L V)free wall
and markedly thickened right ventricular wall.
Note that in this figure (as in figs. 8-10) the left
ventricular free wall appears to curve toward, and
is in a position close to the cephalad aspect of the
ventricular septum. This relation of ventricular
septum to left ventricular free wall was observed
in several patients with tunnel subaortic stenosis
when the heart was sectioned through the anterolateral papillary muscle but not when the heart
was sectioned between the papillary muscles as
shown diagrammatically in figs. 11 and 12. There
is marked fibro us scarring of the ventricular septum and right ventricular free wall (R V). Scarring
in the left ventricle is limited to the papillary
muscles. Both mitral and aortic valves are also
thickened by fibrous tissue. Area of left ventricular apex used for anastomosis is shown by dotted
line. D) View from above the left atrium (LA) and
right atrium (RA). The left atrium is small and
the right atrium and coronary sinus are dilated.
The walls of both atria are thickened.
CI RCULATION
412
VOL 54, No 3, SEPTEMBER 1976
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sent diverse manifestations of a single disease, we cannot exclude the possibility that tunnel subaortic stenosis is a
morphologic abnormality common to several etiologically
distinct diseases. Nonetheless, the characteristic tubular
narrowing of the outflow tract present in our patients clearly
distinguishes tunnel subaortic stenosis from aortic valvular
stenosis and supravalvular aortic stenosis.
Discrete (membranous) subaortic stenosis, the form of left
ventricular outflow obstruction most likely to be confused
with tunnel subaortic stenosis, is characterized by a
relatively thin (1-2 mm in thickness), crescent-shaped
fibrous membrane that extends across the anterior portion
of the left ventricular outflow tract (with each end inserting
onto the anterior mitral leaflet) about I cm below the aortic
anulus. It should be pointed out, however, that it may be
possible for discrete (membranous) subaortic stenosis and
tunnel subaortic stenosis to occur in the same patient. We
have observed several patients (not included in this study)
with a typical discrete subaortic fibrous membrane, who also
had evidence of diffuse narrowing of the left ventricular outflow tract. Indeed, we believe it is likely that patients with
discrete subaortic stenosis may demonstrate a spectrum of
abnormalities of the left ventricular outflow tract ranging
from mild deformity to the severe narrowing of typical
tunnel subaortic stenosis.
The importance of clinically differentiating a patient with
tunnel subaortic stenosis from one with a discrete subaortic
membrane relates to the efficacy of operation in reducing the
gradient in these two conditions. In patients with a discrete
subaortic membrane (with or without severe obstruction of
the left ventricular outflow tract) marked operative relief of
outflow obstruction usually can be accomplished with low
risk.4'' I In contrast, of the patients reported in this paper
with tunnel subaortic stenosis, the smallest residual gradient
present at the most recent cardiac evaluation was 50 mm
Hg. In five of seven operated patients (in whom serial
measurements of the outflow gradient were made) the
magnitude of subaortic obstruction increased or did not
change appreciably following operation; outflow obstruction
decreased significantly after operation in only two patients.
There was no obvious factor that might explain why
operation reduced the outflow gradient in some patients with
tunnel subaortic stenosis and not in others. However, it may
be relevant that four of the five patients with poor operative
results had an abnormally small aortic anulus, while the
anulus was not small in either of the two patients with
relatively favorable operative results. The poor prognosis of
patients with tunnel subaortic stenosis is emphasized by the
fact that three patients died suddenly and unexpectedly (two
FIGURE 8. Heart ofpatient R.D. (A 74-331). Longitudinalsection
showing that the ventricular septum (VS) is disproportionately
thicker than the left ventricular (L V) free wall. The left ventricular
outflow tract is narrowed but the left ventricular cavity appears
relatively normal in size. A V aortic valve; Ao. = aorta,
LAA left atrial appendage; RV= right ventricle.
=
e,
Discussion
Each of the patients with tunnel subaortic stenosis
described in this study showed, by definition, severe tubular
narrowing of the left ventricular outflow tract which was
morphologically similar from patient to patient. In addition,
the aortic anulus was abnormally small in over one-half of
our patients, a finding which in one patient was associated
with hypoplasia of the ascending aorta and coarctation of
the aorta. Two patients had asymmetric septal hypertrophy. Systolic anterior motion of the mitral valve was
present in one of these patients, as well as in another patient
who did not show asymmetric septal hypertrophy. Two
other patients had evidence of a small mitral orifice.
Although this broad spectrum of abnormalities may repre-
TABLE, 4. Anatomic Abnormalities* in 11 Patients with Tunnel Subaortic Stenosis
Tubular LV outflow tract
Abnormally small aortic anulus
Hypoplastic ascending aorta
Small mitral orifice
Asymmetric septal hypertrophy
SAM
K.W.
D.A.
+
+
+
+
0
0
0
0
0
0
-
T. Cap.
+
+
+
+
0
0
M.Q.
+
0
0
0
-
G.G.
Patients
T.C.
R.D.
L.W.
M.S.
A.D.
A.G.
+
+
+
0
0
0
+
0
0
+
±
±
Ot
+
+
0
+
0
0
0
0
0
0
0
0
0
+
+
0
+
0
0
-
0
*Based on the synthesis of angiographic, echocardiographic, operative and pathologic data.
was judged to be slightly small at operation but appeared normal-sized on an echocardiogram recorded 11 years later.
+ - Abnormality bresent.
O -Abnormality absent.
- - No data available.
Abbreviations: LV = left ventricular; SAM - abnormal systolic anterior motion of the anterior mitral leaflet (demonstrated by echo).
tAortic anulus
0
+
0
0
0
±
413
TUNNEL SUBAORTIC STENOSIS/Maron et al.
K
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FIGURE 9. Heart ofpatient R.D. (A74-331). A)
Close-up view of left ventricular outflow tract. A
thick fibrous plaque is present in apposition to the
anterior mitral leaflet. B) View with the aorta
opened showing the aortic valve (A V) and subvalvular area. The anterior mitral leaflet (A ML),
in apposition to the mural endocardial plaque,
also is thickened. The aortic valve cusps are also
diffusely thickened by fibrous tissue. The area of
the aortic valve anulus, as well as the outflow
tract, appear abnormally narrowed. LAA left
atrial appendage; L V
left ventricle.
of whom died late postoperatively).
Another form of left ventricular outflow obstruction that
may be confused with tunnel subaortic stenosis is obstructive
ASH. Patients with obstructive ASH characteristically
demonstrate disproportionate thickening of the ventricular
septum. Also, the mitral valve is positioned anteriorly in the
left ventricular cavity and obstruction to outflow occurs
because of an abnormal systolic anterior motion of the tip of
the anterior mitral leaflet. While these features may also occur in some patients with tunnel subaortic stenosis (figs. 5
and 8), the left ventricular outflow tract (that area just below
the aortic valve) is not markedly deformed in patients with
FiGURE 10. Heart ofpatient D.A. (A 72-115). With aorta opened,
showing aortic valve and subvalvular area. Both the outflow tract
and the area of the aortic anulus are greatly reduced in size. In addition, both mitral and aortic valve cusps are thickened by fibrous
tissue that also covers the mural endocardium in the left ventricular
outflow tract. The chordae tendineae attached to the anterior mitral
leaflet are also thickened. A V aortic valve; A anterior mitral
leaflet, LYV left ventricle.
414
CIRCULATION
NORMA L
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DISCRETE SUBAORTIC
STEN OSIS
ASYMMETRIC SEPTAL
HYPERTROPHY - OBSTRUCTIVE
(IHSS)
VOL 54, No 3, SEPTEMBER 1976
FIGURE 11. Diagrammatic illustration of the
salient anatomic findings of patients with various
types of subaortic obstruction, including discrete
(membranous) subaortic stenosis, obstructive ASH
[typical idiopathic hypertrophic subaortic stenosis
(IHSS)I and tunnel subaortic stenosis. Although the
anatomic variation in tunnel subaortic stenosis is too
great to permit summation in a single illustration, the
heart at the bottom shows the most common features
of this condition - i.e., a markedly narrowed left
ventricular outflow tract, concentrically thickened
ventricular walls, an abnormally small aortic anulus,
normal-sized mitral orifice and left atrium and a
mitral valve positioned normally in the left ventricular cavity. Each heart is shown sectioned between
the papillary muscles and in the mid-point of the
posterior mitral leaflet; the hearts are depicted during
the mid-diastolic phase of the cardiac cycle. Anterolateral papillary muscles are shown by dotted lines for
purposes of orientation. Fibrous tissue is shown in
solid black. Ao = aorta; AML - anterior mitral
leaflet; LA = left atrium; LV left ventricle;
LVOT= left ventricular outflow tract; PM =
papillary muscle (anterolateral); PML = posterior
mitral leaflet; PW= posterior left ventricular wall;
VS = ventricular septum.
TUNNEL SUBAORTIC STENOSIS
ASH, as can be appreciated on angiographic study or at
necropsy.
Although most patients with genetically transmitted ASH
can be easily distinguished clinically from patients with
tunnel subaortic stenosis, our findings suggest that on occasion these disease entities may be related. For example,
patient R.D. with tunnel subaortic stenosis had disproportionate ventricular septal thickening at necropsy, and ASH
was documented echocardiographically in his father. Patient
G.G. had both unequivocal ASH on echocardiographic
study and severe disorganization of cardiac muscle cells in
the ventricular septum, a histologic finding that is characteristic of genetically transmitted ASH."5 16 Thus, two of
our 11 patients with tunnel subaortic stenosis had findings
suggestive of genetically transmitted ASH,',15, 116, 20, 31-34
raising the possibility that fibromuscular narrowing of the
left ventricular outflow tract may represent another manifestation of the disease spectrum of ASH.
The anatomic features of hearts with discrete subaortic
stenosis and obstructive ASH are compared to a representative heart with tunnel subaortic stenosis in diagrammatic
form in figure 11. However, the broad spectrum of anatomic
abnormalities present in patients with tunnel subaortic
stenosis cannot be satisfactorily summarized in a single
diagram. Therefore, in figure 12 three variations of
anatomic abnormalities seen in patients with tunnel subaortic stenosis (including the one shown in fig. 11) are illustrated during both the diastolic and systolic phases of the
cardiac cycle. This description is not intended to represent a
strict classification of abnormalities in tunnel subaortic
stenosis, but rather emphasizes the anatomic variability in
patients with this condition. By definition, all patients with
tunnel subaortic stenosis (i.e., diagrams A, B, and C in fig.
12) manifest diffuse narrowing of the left ventricular outflow
tract. Typically, these patients also have an abnormally
small aortic anulus, but normal-sized mitral orifice and left
atrium; concentric ventricular wall thickening is usually
present with a mitral valve that is normally positioned in the
left ventricular cavity (diagram B). In contrast, in some
patients (diagram A, representing patient T. Cap.) the aortic
anulus, mitral orifice and left atrium are each abnormally
small (in addition to the narrowed outflow tract). Finally,
patients may demonstrate disproportionate ventricular septal thickening, abnormal systolic anterior motion of the
mitral valve, and a mitral valve positioned anteriorly in the
left ventricular cavity. These patients also have an enlarged
left atrium, but normal-sized aortic anulus (diagram C,
representing patient G.G.).
The clinical features of our patients are similar to those of
the 12 patients described by Kelly et al.8 as having a form of
TUNNEL SUBAORTIC STENOSIS/Maron et al.
A.
415
g
B.
.
FIGURE 12. Diagrammatic illustrations showing the spectrum of anatomic abnormalities present in patients with tunnel subaortic stenosis.
Each heart is shown sectioned between the
papillary muscles and in the mid-point of the
posterior mitral leaflet; the hearts are depicted
during the mid-diastolic and mid-systolic phases
of the cardiac cycle. Anterolateral papillary
muscles are shown by dotted lines for purposes of
orientation. Appearance of the heart in the midsystolic phase corresponds generally to that
observed at necropsy. Fibrous tissue is shown in
solid black. Ao = aorta; AML = anterior mitral
leaflet; LA = left atrium; LV= left ventricle;
L VOT = left ventricular outflow tract; PM =
papillary muscle (anterolateral), PML =
posterior mitral leaflet; PW = posterior left ventricular wall; VS = ventricular septum.
B.
.......j
....~~~~
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.......
M I D - DIASTOLE
X....
MID- SYSTOLE
discrete subaortic stenosis (Type II in his report). However,
while these investigators used the term tunnel aortic stenosis
to describe only those patients with both fibromuscular
narrowing of the outflow tract and an abnormally small aortic anulus, we prefer to regard all patients with fibromuscular narrowing of the outflow tract (regardless of the
size of the aortic anulus) as part of the disease spectrum of
tunnel subaortic stenosis. Deutsch et al.7 also described the
angiographic features of one patient who had a "tunnel-like
stricture" of the left ventricular outflow tract. Two other
patients have been described35 who demonstrated fibromuscular narrowing of both the right and left ventricular
outflow tracts at necropsy. In addition, fibromuscular tunnel
deformity of the left ventricular outflow tract in patients
with complete transposition of the great vessels has been
described.36
current operative methods in patients with tunnel subaortic
stenosis, it is important to differentiate this condition from
other forms of obstruction to left ventricular outflow.
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1.
2.
3.
4.
5.
37
In conclusion, this report describes the clinical, hemodynamic and morphologic features of an unusual form of
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a variety of congenital cardiovascular malformations,
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unchanged during the cardiac cycle. This fibromuscular deformity of the outflow tract often is associated with a small
aortic anulus. Because of the apparent ineffectiveness of
6.
7.
8.
9.
10.
11.
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VOL 54, No 3, SEPTEMBER 1976
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Circulation. 1976;54:404-416
doi: 10.1161/01.CIR.54.3.404
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