CASE REPORT

Complete Atrioventricular Canal With Guarded Primum SeptalDefect

Susheel Kumar • Mary Donofrio • Lowell Frank •

Dingchao He • Richard Jonas

Received: 20 September 2010 / Accepted: 7 December 2010 / Published online: 25 December 2010

� Springer Science+Business Media, LLC 2010

Abstract Common atrioventricular canal (CAVC) is a

common congenital heart lesion resulting from a defect in

development of the endocardial cushions during early

embryogenesis. Depending on the type of defect, CAVC

can encompass a spectrum of lesions ranging from partial

atrioventricular (AV) canal to complete AV canal. We

describe a case of CAVC with unique anatomy in a

4-month-old male infant with Down syndrome.

Keywords Congenital heart disease � Anatomy � Valve

J. G. was a 4-month-old male infant with Down syndrome

who was referred for a diagnosis of CAVC. He had symp-

toms of mild congestive heart failure and was receiving

diuretic therapy. He also had hypothyroidism, which was

being treated with thyroxine. Chest X-ray showed cardio-

megaly with plethoric lung fields. Electrocardiogram

showed biventricular hypertrophy with a counterclockwise

electrical axis. Echocardiogram (echo) suggested two nor-

mal-sized ventricles and an unusual AV valve development

with adhesion of an accessory valve to the margins of the

primum atrial septal defect (ASD) (Fig. 1). There was

thought to be a small left-to-right shunt across the primum

ASD. The ventricular septal defect (VSD) was large with a

significant left-to-right shunt. Trivial left AV valve regur-

gitation was noted. There was also a small patent ductus

arteriosus. Cardiac catheterization confirmed the diagnosis

and showed a Qp:Qs ratio of 2 to 1 and normal pulmonary

vascular resistance.

At surgery, the thymus was normal in size, and the great

vessels were normally related. The heart was considerably

dilated. A patch of pericardium was harvested and treated

with 0.6% glutaraldehyde. After institution of cardiopul-

monary bypass, aortic cross-clamping, and infusion of car-

dioplegia, the right atrium (RA) was opened. Thorough

examination of the anatomy showed unusual CAVC mor-

phology. In addition to the usual common AV valve, there

was a perfectly formed accessory valve adhering circum-

ferentially to the margins of the primum ASD. This acces-

sory valve was in continuity with the common AV valve at

the junction of the mitral and tricuspid components. Thus,

the right-sided AV valve was effectively split into two

components, one guarding the LV and one encircling the

primum ASD. The superior common leaflet was free floating

and undivided, as seen in Rastelli type C, although the

inferior common leaflet was divided over the crest of the

septum. The canal appeared to be balanced with a large VSD

component. There were two LV papillary muscles, and the

fossa ovalis was intact.

To allow visualization of the left AV valve component

guarding the LV, a vertical incision was made in the fossa

ovalis. A single pericardial patch repair was performed, in

which multiple interrupted pledgetted horizontal mattress

5/0 Prolene sutures were placed through the crest of the

septum. The sutures were passed through the superior

common leaflet as well as the left-sided component of the

inferior common leaflet before being passed through a

single pericardial patch. Tying down these sutures oblit-

erated the VSD component. The new mitral valve (MV)

was tested by injection of cardioplegia solution by way of

the incision in the atrial septum. The cleft in the MV was

S. Kumar � M. Donofrio � L. Frank � D. He

Department of Cardiology, Children’s National Medical Center,

Washington, DC, USA

R. Jonas (&)

Children’s National Heart Institute, Children’s National Medical

Center, Washington, DC, USA

e-mail: rjonas@cnmc.org

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Pediatr Cardiol (2011) 32:503–505

DOI 10.1007/s00246-010-9869-4

not closed because the regurgitation was mild, and it was

difficult to identify the nature of regurgitation because of

the complex interplay between the valve guarding the

primum ASD and the valve guarding the LV. The same

pericardial patch was sutured to the right atrial margin of

the primum ASD using continuous 5.0 Prolene suture, thus

leaving the accessory valve to the left of the patch. The

suture line was placed inside the ostium of the coronary

sinus, which continues to drain to the RA. The incision in

the atrial septum was closed. The child was weaned off

cardiopulmonary bypass with dopamine support of 5 mcg/

kg/min. Trans-esophageal echocardiography showed mild

to moderate mitral regurgitation, and there was no obvious

v wave on the left atrial (LA) trace. The LA pressure was

\10 mm Hg at a systemic pressure of 80 mm Hg. The

patient did well and was extubated on the first postopera-

tive day. He was discharged home 1 week later. Follow-up

up echo at the time of discharge showed mild mitral

regurgitation with no residual shunt.

Discussion

The atrioventricular endocardial cushions are two masses of

embryonic mesenchyme that normally execute the division

of the atrioventricular canal into right and left atrioventric-

ular orifices [1]. They also contribute to formation of the

atrioventricular septum, the membranous interventricular

septum, and the atrioventricular valves. It is thus easy to

understand how variedly defects in endocardial cushion

tissue growth may manifest. The basic prerequisite for the

diagnosis of CAVC is the presence of a common AV valve

[2]. If the VSD component is pressure restrictive, it is called

a transitional AV canal [3]. Complete AV canal defect is

further classified into Rastelli types A, B, and C depending

on the anatomy of the superior bridging leaflet.

Defects in endocardial cushion proliferation also result in

defects other than CAVC and isolated inlet VSD. Rarely, the

ostium primum (OP) component of CAVC can be absent or

diminutive. In the largest series ever reported, Kaur et al. [2]

described the echocardiographic and intraoperative features

in 14 such patients. In these rare cases, the AV valves appear

divided when viewed from the atrium but common when

viewed from the ventricular aspect. One of the patients

underwent pulmonary artery banding when the diagnosis

was missed and was mistaken for a ‘‘straddling tricuspid

valve’’ at surgery. These investigators stressed the impor-

tance of accurate preoperative diagnosis because long-term

outcomes for surgical repair of CAVC defects depend on

successful repair of the mitral component.

Isolated MV cleft is an uncommon congenital anomaly

that usually affects the anterior MV leaflet. There is con-

troversy regarding the embryological basis of isolated MV

cleft. Although some consider it a ‘‘forme fruste’’ of CAVC

and therefore an endocardial cushion defect, others con-

sider it to be a distinct morphological entity [4].

Double-outlet atrium, also considered an endocardial

cushion defect, as described by Van Mierop et al. [1], is a

condition in which either the right or left atrium empties into

both ventricles. Double-outlet right atrium (DORA), which

is the more common of the two, is either associated with

CAVC or a straddling AV valve. DORA associated with

CAVC is characterized by the triad of leftward deviation of

the true atrial septum, presence of a cephalic and posterior

LA chamber receiving all the four pulmonary veins, and

CAVC in the form of a partial (more common) or complete

defect (Fig. 2b) [5]. The LA empties into the RA through an

ASD. Embryologically, the condition is thought to arise as a

result of leftward lateral direction of the ingrowing septum

primum, which allows it to fuse with the left lateral endo-

cardial cushion of the AV canal rather than the superior and

inferior cushions as would happen normally [5]. Surgical

repair is straightforward and includes excision of the mal-

aligned atrial septum and replacement, with a patch con-

nected to the partition between the right and left AV valves,

combined with repair of the CAVC defect.

Fig. 1 Preoperative

transthoracic ECHO images.

a Arrow points toward the lower

part of a seemingly intact atrial

septum. b Anatomy of CAVC.

The large VSD component is

well noted. Arrow shows an

intact atrial septum

504 Pediatr Cardiol (2011) 32:503–505

123

In our case, the anatomy of the AV canal defect was

indeed unique and did not fit into any of the above-men-

tioned varieties of AV canal defect. To the best of our

knowledge, this unusual anatomy has not been described

before. Morphologically, it seemed to lie between a com-

plete CAVC and CAVC with absent OPASD within the

spectrum of endocardial cushion defects. At surgery, it

mimicked a DORA with CAVC because the valve guarding

the primum defect resembled the left component of the AV

valve (Fig. 2c). After a thorough examination, it was real-

ized that the valve guarding the septal defect led to the LA

(and not to the LV as in DORA with CAVC). Excision of the

accessory valve was not advisable in view of the fusion

between the accessory valve and the true common AV valve

as well as the common subvalvar apparatus. A surgical

incision in the floor of the fossa ovalis facilitated inspection

of the mitral component. Our technique of repairing the

CAVC (Australian technique) [3], i.e., without disturbing

the valves guarding the OPASD, was effective. Embryo-

logically this lesion supports the theory that the OP defect in

utero closes by proliferation of tissue from mesenchymal

extensions arising from both the superior and inferior

endocardial cushions along the lower border of the septum

primum and fusion of these later in the midline [1].

References

1. Van Mierop LH, Alley RD, Kausel HW, Stranahan A (1962) The

anatomy and embryology of endocardial cushion defects. J Thorac

Cardiovasc Surg 43:71–83

2. Kaur A, Srivastava S, Lytrivi ID, Nguyen K, Lai WW, Parness IA

(2008) Echocardiographic evaluation and surgical implications of

common atrioventricular canal defects with absent or diminutive

ostium primum defect. Am J Cardiol 101(11):1648–1651

3. Jonas RA (2004) Complete atrioventricular canal. In: Jonas RA

(ed) Comprehensive surgical management of congenital heart

disease, 1st edn. Arnold Publishing, London, England, pp 386–401

4. Abadir S, Fouilloux V, Metras D, Ghez O, Kreitmann B, Fraisse A

(2009) Isolated cleft of the mitral valve: distinctive features and

surgical management. Ann Thorac Surg 88(3):839–843

5. Brancaccio G, Amodeo A, Rinelli G, Filippelli S, Sanders SP, Di

Donato RM (2007) Double-outlet right atrium: anatomic and

clinical considerations. Ann Thorac Surg 83(2):619–621

Fig. 2 Anatomy of a complete CAVC, b DORA, and c our reported case

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