Journal of Pediatric Cardiology and Cardiac Surgery 3(1): 28‒34 (2019)

Case Report

Cor Triatriatum Dexter in a Infant witha Hypoplastic Right Ventricle
Masayuki Abiko, MD1), Tesshu Otagiri, MD, PhD1), Tatsunori Takahashi, MD1),
Makoto Sato, MD1), and Seigo Gomi, MD, PhD2)
1) Department of Pediatrics, Yamagata University Faculty of Medicine, Yamagata, Japan

2) Second Department of Surgery, Yamagata University Faculty of Medicine, Yamagata, JapanCor triatriatum dexter (CTD) is a very rare cardiac anomaly in which a membrane divides the right atrium (RA)into two chambers. Clinical presentation of CTD is slightly variable. Most patients are asymptomatic, and a lesion
is discovered during echocardiography or surgery for other cardiac lesions. When accompanied with interatrial
defects, patients with CTD exhibit cyanosis because of the right-to-left shunt via interatrial communication.
Moreover, CTD and cyanotic congenital heart diseases require diﬀerentiation. To our knowledge, there are noreports of infants with a hypoplastic RV who were diagnosed with CTD, and there is no consistent opinion about
the best treatment strategy for CTD. Here, we describe a male neonate with CTD and a hypoplastic RV having
symptoms of central cyanosis soon after birth. A large membranous structure was identified in the RA and flowfrom the inferior vena cava was partially redirected into the left atrium (LA) via the patent foramen ovale (FO).
We surgically resected a large membranous structure from the RA and partially closed the FO when the patientwas 4 months old. We performed cardiac catheterization 12 months after surgery and confirmed that the RV waswell-developed and had good function. We speculate that for CTD with hypoplastic RV and inter-atrial communication, resection of the Eustachian valve and partial closure of the FO may be eﬀective treatment strategies aslong as the size of the RV is considered. Further studies on RV size and intervention for the FO in such cases of
CTD are needed.

Keywords: Cor triatriatum dexter, embryonic right sinus venous valve persistence, cyanosis, neonate,hypoplastic right ventricle

Introduction
Cor triatriatum dexter (CTD) is an extremely rarecongenital cardiac malformation in which a persistentembryonic right sinus venosus valve subdivides the rightatrium (RA).
Septation of the RA can interfere with normal bloodflow into the RA and tricuspid valve, leading to a broad
range of clinical symptoms. Depending on the degree ofRA obstruction, a clinical sign of these anatomic variations may be neonatal cyanosis necessitating urgent surgical intervention while some patients are asymptomaticand reach adulthood without therapy.1)

To our knowledge, there have not been any reports ofinfants with a hypoplastic RV who were diagnosed with
CTD, and there is no consistent opinion about the besttreatment strategy for this condition. In this case report,
we describe a male neonate with CTD and a hypoplastic
RV who had symptoms of central cyanosis soon after
birth. In this patient, a large membranous structure was
identified in the RA and flow from the IVC was partiallyredirected into the LA via the patent foramen ovale(PFO).

Case Presentation
The guardians of the patient, whose details appear in

Received: July 31, 2018; Accepted: November 6, 2018
Corresponding author: Masayuki Abiko, MD, Department of Pediatrics, Yamagata Faculty of medicine University, 2‒2 Iida-Nishi
2-Chome, Yamagata-shi, Yamagata 990‒9585, Japan
E-mail: masayuki.abiko@gmail.com
doi: 10.24509/jpccs.190105© 2019 Japanese Society of Pediatric Cardiology and Cardiac Surgery

29this report, provided verbal informed consent, and thestudyʼs design was approved by the appropriate ethics
review board.
A male neonate was spontaneously born at 40 weeks
of gestation after an uncomplicated pregnancy, and hisbirth weight was 3,310 g. His Apgar score was 9 and 10 at
1 and 5 min, respectively. At 3 hours after birth, his physical examination revealed the presence of central cyanosis with a room air oxygen saturation value between
85% and 93%. The patient was unresponsive to oxygen
administration, and the room air oxygen saturation level
decreased to below low 70% with crying. The patient wasotherwise well, with no signs of respiratory distress.
Transthoracic echocardiography was performed at
an outside hospital and showed tricuspid valve stenosis and closing ductus arteriosus. A prostaglandin E1
infusion was started and the neonate was transferred toour institution. Upon admission, his saturation values
remained around 85%‒90%, although he had patency
and an adequate ductal size. His vital signs, except foroxygen desaturation, were within normal range. His
cardiovascular examination showed a quiet precordium,normal heart sounds, and no murmur. The results of all
investigations including complete blood count, septic
work-up, and liver and renal function tests were normal,
but only the plasma brain natriuretic peptide level waselevated to 131 pg/mL. The venous blood gas pH was
7.45 and the PaCO2 was 35.8 mmHg, and the base excess
was +1.7 mmol/l. The findings of chest radiography andelectrocardiography were also unremarkable.
Using two-dimensional transthoracic echocardiography, we diagnosed the neonate with congenital tricuspid
valve stenosis with a hypoplastic RV at first (Fig. 1A‒C)
and continued administering prostaglandin E1 infusion.
The tricuspid valve was hypoplastic and dysplastic withtrivial tricuspid regurgitation (the annulus measured
6.0 mm; the normal range is 9.3‒17.5 mm; z-value,−3.9). The inflow of the tricuspid valve appeared tobe substantially narrowed with an eccentric jet crossing from the RA to the hypoplastic RV. A pulse-wave
Doppler ultrasound examination of the tricuspid valveʼs
inflow revealed it had a monophasic pattern with maximal velocities of 1.4 m/s. The pulmonary valveʼs annulus
was smaller (6.6 mm; the normal range is 5.9‒9.8 mm;
Z-value −0.93), but there was no evidence of abnormal
valve thickening or flow acceleration and valve regurgitation on color or pulsed Doppler ultrasound examina-

tions.
A few days later, we noticed there was a prominentand elongated membranous structure extending fromthe junction of the IVC to the RA (Fig. 1D). Color Doppler ultrasound with a right sternal border sagittal view
showed that the large membranous structure hemodynamically divided the RA into two chambers; that is,both blood flow from the IVC and superior vena cava
(SVC) were partially redirected by this membrane to theLA via the PFO, leading us to diagnose the patient with
CTD (Fig. 1E). After stopping prostaglandin E1 infusion, we confirmed that the ductus arteriosus was closed,
and the patientʼs saturation values remained at approximately 85%‒93% with oxygen inhalation (1 L/min nasal
cannula).
Upon serial evaluation with transthoracic echocardiography, we found that the tricuspid and pulmonary
valve diameters gradually grew in the postnatal period(Table 1). We judged that elective surgery was possible,
and the patient was sent home with standby oxygen anda pulse oximeter at 33 days after birth.
Since desaturation progressed, we performed cardiac
catheterization when the patient was 3 months old.
Angiography of the SVC showed that contrast media
mainly flowed toward the tricuspid valve into the RV(Fig. 2A). Similar to the echocardiographic findings, thetricuspid valveʼs diameter and RV volume were small(Fig. 2B, C). We performed a balloon occlusion test of
the foramen ovale (FO) and compared the hemodynamic parameters and angiographic findings before andafter the balloon occlusion test (Table 2). Considering
the end-diastolic volume of the RV (RVEDV) and tricuspid valveʼs diameter, we judged that partial closure of theFO was more preferable than total closure.
We performed surgery (resection of the large persistent right sinus venosus valve and partial closure of
the PFO) when the patient was 4 months old and had abody weight of 9.1 kg. We performed cardiopulmonary
bypass with cardioplegic arrest. The large membranethat originated from the crista terminalis and Eustachianvalve covered half of the caudalis of the FO, and we completely resected it by separating its attachment (Fig. 3).
The tricuspid valveʼs diameter was 11 mm (61% of thenormal diameter) and had a dysplastic appearance, and
the PFO was approximately 6 mm. We finally decided toclose the FO partially, and we sewed only the right border of the FO and reefed it to 4 mm.

© 2019 Japanese Society of Pediatric Cardiology and Cardiac Surgery

30

Fig. 1 LV short axis (A), LV long axis (B), and apical four chamber (C) two-dimensional echocardiography views
showing a hypoplastic RV and the tricuspid valve diameter (6.0 mm, Z value −3.9) after birth (D) Subxiphoidcoronal and sagittal two-dimensional echocardiography views showing a linear membranous structure
projecting into the RA arising from the junction of the IVC. (E)Right sternal border sagittal two-dimensional
echocardiography view showing a linear membranous structure projecting into the RA and PFO, and anterior deviation of the atrial secondum septum. Color Doppler image showing a linear membranous structurethat hemodynamically divided the RA into two chambers. The ﬂow from the IVC was partially redirected into
the LA via the PFO and ﬂow from the SVC mainly drained into the RA.
IVC, inferior vena cava; LA, left atrium; LV, left ventricle; PFO, patent foramen ovale; RA,right atrium; RV, right ventricle;
SVC, superior vena cava. white arrow: membranous structure. * PFOTable 1 Serial measurements of echocardiographic parameters and SpO2
Measurement parameters

Day0

Day12

Day20

Day27

Day48

2months old

3months old

Tricuspid valve diameter (mm)Z-value
Pulmonary valve diameter (mm)Main pulmonary artery diameter (mm)TVd/MVd
TVd: tricuspid valve diameter
MVd: mitral valve diameter
est Qp (L/min/m2) by VTI
est Qp/Qs by VTI
SpO2 (%) room air
SpO2 (%) O2 inhalation
Body weight (g)

6.0
−3.9
6.6
7.0

6.3

6.1

7.0

9.3

5.7

6.3
5.8
0.51

7.4
6.9
0.54

7.3
−3.8
7.0
7.0

9.8
−2.8
7.2
7.4
0.61

2.4

2.3
0.61

2.6
0.60

2.3

84‒91

85‒93

87‒93
4,600

88‒92
5,988

0.49

87‒93%
3,310

0.61

77‒88%
87‒92

2.4
0.85
75‒86%
85‒90
8,695

Qp, pulmonary blood ﬂow; Qs, systemic blood ﬂow; RV, right ventricle; VTI, velocity time integral

The neonateʼs postoperative course was uneventful.
An echocardiogram showed that he had normal cardiac
function, the large membranous structure in the RA
J Pediatr Cardiol Card Surg Vol. 3, No. 1 (2019)

had disappeared, and flow from the IVC was mainly
directed into the tricuspid valve with a small right-to-leftshunt through the partially closed FO. The patient was

31

Fig. 2 Preoperative angiography of the SVC (A, B: frontal view, C: lateral view) showing that contrast media mainly
ﬂowed into the RV through the tricuspid valve. The tricuspid valveʼs diameter and RV volume were small.
(RVEDV 9.2 mL, 50% of normal, EF 54%,PA index 127) Postoperative angiography of the RV (D: frontal view,
E: lateral view) showing that the RV volume had developed.
EF, ejection fraction; LPA, left pulmonary artery; PA, pulmonary artery; PVd, pulmonary valve diameter; RPA, right pulmonary artery; RV, right ventricle; RVEDV, right ventricular end diastolic volume; SVC, superior vena cava; TVd, tricuspid valve
diametertransferred to the general ward of our hospital on thesecond day postoperatively and was discharged on the
12th postoperative day. After surgery, his room air saturation level remained around 90%, and it increased to95%‒97% with the administration of oxygen, so he wassent home with standby oxygen.
The patientʼs room air saturation values increased andremained around 94% beginning 3 months after surgery
and remained at around 95%‒96% beginning 6 months
after surgery; therefore, we administered home oxygentherapy 7 months after surgery (Table 3). We performed
cardiac catheterization 12 months after surgery andconfirmed that the RV was well-developed and had goodfunction (Fig. 2D, E). We expected that the PFO would
close spontaneously during the follow-up period.

Discussion
In this case report, we described a male neonate with
CTD with a hypoplastic RV who had symptoms ofcentral cyanosis soon after birth. A large membranous
structure was identified in the RA and flow from the

IVC was partially redirected into the LA via the PFO. We
surgically resected the large membranous structure andpartially closed the FO when the patient was 4 months
old and the patient had a good clinical course.
During the embryonic development of the heart, theright horn of the sinus venosus is incorporated into theRA, giving rise to the orifices of the SVC and IVC. At
one point, the right valve of the sinus venosus nearly
divided the RA. It is considered to be a functional valve
in the fetus that helps direct oxygenated blood fromthe IVC toward the FO, thereby bypassing pulmonary
circulation.2) With the growth of the heart, early inthe fetal (between 9 and 15 weeks of gestation), thevalve regresses and moves caudally, leaving the crista
terminalis as its cephalic remnant in a mature heart
and the valves of the IVC (Eustachian valve) and coronary sinus (Thebesian valve) as its caudal remnants.
A minor degree of RA septation is well tolerated, anda prominent Eustachian valve is a common finding on
two-dimensional echocardiography. However, a large,
sail-like membrane that fails to regress may obstruct the© 2019 Japanese Society of Pediatric Cardiology and Cardiac Surgery

32

tricuspid valve, RV outflow tract, or IVC and aﬀect thepatientʼs hemodynamics. It has been hypothesized thatfailed regression of the venous valve may lead to fetal
Table 2 Cardiac catheterization data(A) ‹Preoperative data› room air

RAP
RVP
MPAP
SaO2(DAO)
Qs (Fick)
Qp/Qs
Rp(U・m2)
RVEDV(mL)
RVEF(%)
PA index

Pre balloon
occlusion

Post balloon
occlusion

8/6/(6)20/EDP 5
19/10/(14)
90
4.2
0.74
1.2
9.2 (50%N)
54
179

8/7/(7)
14/EDP 7
19/10/(14)
95
4.1
̶

1.3
9.7 (53%N)
49̶(B) ‹Postoperative data› room air
RAP
RVP
MPAP
SaO2(DAO)
Qp/Qs
Rp(U・m2)
RVEDV(mL)
RVEF(%)
PA index

6/6/(4)19/EDP 5
17/3/(9)97
0.9
0.5
21.4 (78%N)
54
258

DAO, discending aorta; EDP, end diastolic pressure; MPAP,
main pulmonary arterial pressure; PA index, pulmonary
arterial index; Qp, pulmonary blood ﬂow; Qs, systemic blood
ﬂow; RAP, right atrial pressure; Rp, pulmonary resistance;
RVEDV, right ventricular end-diastolic volume; RVEF, rightventricular ejection fraction; RVP, right ventricular pressure;
SaO2, arterial oxygen saturation O2

circulatory abnormalities and subsequent underdevelopment of the right heartʼs structures in utero.3)
The clinical presentation of patients with CTD isslightly variable. Most patients are asymptomatic, and alesion is discovered during echocardiography or surgery
to correct other cardiac lesions. Cyanosis may occur inthose with associated interatrial communication due
to a large right-to-left shunt when flow from the IVC isredirected into the LA via interatrial communication.
Our patient had cyanosis soon after birth. We believethat the membranous structure in the RA was large
enough, and anterior deviation of the atrial secundum
septum permitted blood flow to be redirected from the
IVC into LA. This right-to-left shunt across the PFO
explains why basal desaturation was unresponsive tooxygen. The left valve of the sinus venosus retrogressed
and was absorbed into the limbus region of the septum
secundum. It is thought that abnormal development
and absorption of the left valve of the sinus venous are
related to anterior deviation of the septum secundum.
When accompanied with interatrial communication,
a right-to-left shunt may be observed, and the patient
may be misdiagnosed with a tricuspid valve anomaly.
In our case, we misdiagnosed the patient as having
congenital tricuspid stenosis at first. Congenital tricuspid stenosis is usually associated with other anomalies,
especially RV tract obstruction or atresia with secondary
hypoplasia of the RV.

Fig. 3 (A) Surgical view of the membranous structure during right atriotomy. (B) After resection of the membranous structure. (C) Resected membranous structure
IVC, inferior vena cava; LA, left atrium; PFO, patent foramen ovale; RA, right atrium. * membranous structure

J Pediatr Cardiol Card Surg Vol. 3, No. 1 (2019)

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Table 3 Serial post-operative measurements of echocardiographic parameters and SpO2
Measurement parameters

Preoperation

Tricuspid valve diameter (mm)Z-value
Pulmonary valve diameter (mm)TVd/MVd
TVd: tricuspid valve diameter
MVd: mitral valve diameter
RV inﬂow (cm/s)
Qp (L/min/m2) by VTI
SpO2 (%) room air
SpO2 (%) O2 inhalation
O2 ﬂow rate (L/min)Postoperation
9 days1 month

2 months

9.8

10

8.5

10.6
Z=−2.37.3

10.3

3 months

6 months

12 months

10.3

13.1
Z=−2.0
12.0
0.66

E<A

E>A

E101>A93

94
94‒95
0.25

95‒96
96
0.25 oﬀ

99

0.58

2.4
88
93
1

E<A
2.7
91‒92
95
0.25

91‒92
96
0.25

E82<A105
3.0
90‒91
94‒97
0.25

Qp, pulmonary blood ﬂow; Qs, systemic blood ﬂow; RV, right ventricle; VTI, velocity time integral

Clinically, tricuspid valvular stenosis can be distinguished from hypoplasia of the tricuspid valve. In
patients with tricuspid valvar stenosis, the tricuspid
annulus may be relatively large, but its leaflets are thickened with commissural fusion and shortened chordae
tendineae. In those with hypoplasia of the tricuspid
valve, the tricuspid valveʼs annulus is small, and its leaflets and chordae may be diminutive but otherwise normal. Our patient had a small tricuspid valve diameter;
thus, we should have diagnosed him with hypoplasia of
the tricuspid valve rather than congenital tricuspid valve
stenosis, but the RV outflow tract was intact. In a patientwith a small tricuspid valve diameter and without RV
outflow tract obstruction or atresia, it is important todetect the RA by considering the possibility of a persistent right sinus venosus valve.
Intervention is indicated for patients who are symptomatic. Recently, disruption of the obstructing membrane with a percutaneous catheter has been reported,4)and this may be the therapy of choice in adult patients.
In pediatric patients, there are no similar reports, andsurgical correction is prevalent when intervention isnecessary. Surgical resection is warranted when thesymptoms of flow obstruction or persistent desaturation are observed.5) In previous reports, the timingof intervention was diﬀerent between newborns andadults.6, 7) Some previous reports showed that some neonates present with cyanosis during the newborn period,
but improved naturally afterwards; therefore, waiting fornatural growth is one of the treatment strategies.8)
In this case, we observed the neonate for 3 months
considering the following points: permissible range ofhypoxemia on oxygen supply; serial development of
tricuspid valve diameter; and the possibility of spon-taneous regression of Eustachian valve. We initiallywanted to observe the patientʼs natural improvement,
but natural improvement was not observed. Due to progressive desaturation, small RV volume by angiography,
and necessity for resection of the Eustachian valve andalso intervention for the PFO, we deemed surgical intervention to be necessary. In our case, whether we could
totally close the FO or not was an important clinicalpoint because of the small RV volume. As there are noreports similar to our case, we extrapolated the RV-TV(tricuspid valve) index used in the operative method
selection criteria for pulmonary atresia with intact ventricular septum.
The RV-TV index was 0.29 in our case (RVEDV
50%N, tricuspid valve diameter: 58% of normal), andwe believe that this indicated partial closure of the FO(4-mm fenestration). As a result, cyanosis remained
after the surgical operation, but it gradually improved as
the right ventricle grew.
If we had performed total closure of the FO, we believethat the patient would have been more likely to suﬀer
from right heart failure, although there was a possibilityof earlier right ventricular development.
We speculate that for CTD with hypoplastic RV andinter-atrial communication, resection of the Eustachianvalve, and partial closure of the FO may be eﬀective
treatment strategies as long as the size of the RV is taken
into consideration. Further studies on the RV size andintervention for the FO in such cases of CTD are needed.
Acknowledgment
We would like to thank Editage (www.editage.jp) for
English-language editing.

© 2019 Japanese Society of Pediatric Cardiology and Cardiac Surgery

34

Funding
This research received no specific grant from any funding
agency in the public, commercial, or not-for-profit sectors.
Conﬂicts of Interest
The authors have no conflicts of interest to disclose.

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