CASE CONFERENCEMark A. Chaney, MDVictor C. Baum, MD

Section Editors

CASE

3—2014Cor Triatriatum Sinister Presenting in Adulthood

Michelle Capdeville, MD,* Nicolas Brozzi, MD,† Gosta Pettersson, MD,† A. Marc Gillinov, MD,†

and Julie Niezgoda, MD‡

COR TRIATRIATUM is an uncommon congenital cardiacanomaly that is characterized by division of the left atrium

into two separate chambers by a fenestrated membrane. Thiscondition typically presents in infancy or early childhood, andcan be associated with other cardiac anomalies. A smallernumber of adult cases have been reported in the literature. Wepresent the case of a patient with cor triatriatum sinister and anassociated atrial septal defect who presented in adulthood,along with a comprehensive review of the literature with afocus on adult patients.

From the *Department of Cardiothoracic Anesthesia, †Departmentof Thoracic and Cardiovascular Surgery, and ‡Department of PediatricAnesthesiology, Cleveland Clinic, Cleveland, Ohio.

Address reprint requests to Michelle Capdeville, MD, Department ofCardiothoracic Anesthesia, Cleveland Clinic, 9500 Euclid Avenue/J4-331, Cleveland, OH 44195. E-mail: capdevm@ccf.org

CASE REPORT*

A 43-year-old man was transferred to this institution for furtherevaluation and management of recurrent atrial tachycardia in the settingof newly diagnosed cor triatriatum and patent foramen ovale bytransesophageal echocardiography. His presenting symptoms includedpalpitations, followed by chest pain and right jaw pain. He underwentHolter monitoring with no captured arrhythmias, followed by a nuclearstress test, which showed no electrocardiographic changes and nosignificant arrhythmia. Perfusion images showed no abnormality. Hesubsequently developed some prolonged episodes of atrial tachycardiathat were captured on telemetry and treated with diltiazem. He had nohistory of arrhythmias before this presentation; his past medical historywas significant only for hyperlipidemia, and there was no prior historyof surgery or general anesthesia. Home medications included metopro-lol, 50 mg daily. He had received coumadin at the transferring hospital,but was not anticoagulated at the time of presentation.

As part of his preoperative workup for surgical repair, he underwentcardiac MRI, which confirmed the diagnosis of cor triatriatum sinister(Fig 1). An extensive fenestrated left atrial membrane with attachmentpoints at the fossa ovalis and at the junction of the left upper pulmonaryvein and left atrial appendage was identified, with evidence of flowacceleration across the membrane. Left-heart catheterization wassignificant for two low-grade lesions (30% and 40%) in the left anteriordescending coronary artery and a left-to-right interatrial shunt. The leftventricular end-diastolic pressure (LVEDP) was 16 mmHg. Simulta-neous pulmonary capillary wedge pressure (PCWP) and LVEDPshowed a PCWP – LVEDP gradient of approximately 3 mmHg,suggesting a mean gradient across the LA membrane of 3 mmHg. Aright-heart catheterization showed the following oxygen saturations:superior vena cava, 70%; inferior vena cava, 70%; right atrium, 77%;

*M. Capdeville, N. Brozzi, and G. Pettersson

408 Journal of Cardiotho

right ventricle, 75%; and pulmonary artery, 77%. The shunt fraction(Qp:Qs) was calculated to be 1.4:1. The arterial saturation was 95%.

A transthoracic echocardiogram showed the left atrial membrane, amildly dilated left ventricle (LVEF 50%), a dilated right ventricle withpreserved systolic function, mild tricuspid regurgitation, 2þ mitralregurgitation, biatrial enlargement, and a right-to-left interatrial shunt(in contrast to the shunt direction noted at catheterization) consistentwith a patent foramen ovale versus an atrial septal defect. The estimatedright ventricular systolic pressure was 31 mmHg.

All preoperative laboratory values, including complete blood count,electrolytes, renal panel, and coagulation panel were within normal limits.

The patient underwent uneventful anesthetic induction with etomi-date, midazolam, fentanyl, and intubation with rocuronium. His main-tenance anesthetic included fentanyl, rocuronium, and inhaled isoflurane.Monitoring included standard ASA monitors, a left brachial arterialcatheter, a right internal jugular introducer sheath with pulmonary arterycatheter, and transesophageal echocardiography.

Intraoperative echocardiography showed a fenestrated membrane inthe left atrium, extending from the interatrial septum to the junction ofthe left upper pulmonary vein and left atrial appendage (Fig 2, Videoclips 1 and 2). A 1-cm secundum-type atrial septal defect was identifiedby color flow inferior to the atrial membrane (Video clip 3), with right-to-left shunting. There was 1-to-2þ mitral regurgitation, mitral annulardilatation, mild tricuspid regurgitation, normal left ventricular size andfunction, and a dilated right ventricle with normal systolic function.

The patient underwent resection of the atrial membrane, mitral valveannuloplasty, atrial septal defect (ASD) closure, and a MAZE procedure.The operation was performed through a median sternotomy with aorticand bicaval cannulation, delivery of antegrade and retrograde cardiople-gia, and normothermia. A right atrial incision was made, with explorationof the left atrium through the interatrial septum. The left atrial membranewas visualized clearly and excised (Fig 3), and the left atrial appendageamputated. The mitral valve also was approached through the interatrialseptum and repaired with a #36 Cosgrove annuloplasty band. The ASDwas closed, and the patient was weaned from cardiopulmonary bypass

© 2014 Elsevier Inc. All rights reserved.1053-0770/2602-0033$36.00/0http://dx.doi.org/10.1053/j.jvca.2013.08.018Key words: Cor triatriatum sinister, adult population, review

racic and Vascular Anesthesia, Vol 28, No 2 (April), 2014: pp 408–416

Fig 1. Cardiac magnetic resonance imaging showing left atrial

membrane (arrow) separating the proximal accessory chamber and distal

main left atrial chamber. (Color version of figure is available online.)

CASE 3—2014 409

without need for pharmacologic support. The post-pump TEE showed noresidual mitral regurgitation and normal biventricular function. Hispostoperative recovery was uneventful.

DISCUSSION

Cor triatriatum, also known as cor triatriatum sinister, ortriatrial heart, is an uncommon congenital cardiac condition

Fig 2. Midesophageal 4-chamber still frame showing “triatrial” heart w

LV, left ventricle; P, proximal accessory left atrial chamber receiving pulm

version of figure is available online.)

that is characterized by separation of the left atrium into aproximal (superior, posterior) accessory chamber that receivesinflow from all four pulmonary veins, and the distal (inferior,anterior) main left atrial chamber (including the left atrialappendage and mitral orifice) by a fenestrated fibromuscularseptum. The insertion point of the membrane is at the margin ofthe fossa ovalis medially, and at the junction of the left upperpulmonary vein and left atrial appendage laterally.1,2 Theproximal chamber has been described as a common pulmonaryvein, or third atrium, where the 2 right and left pulmonary veinsjoin together. The earliest description of cor triatriatum was byChurch in 1868.3 The reported incidence is 0.1% to 0.4%,4

with a slight male preponderance (1.5:1).5 Developmentally, itis believed to result from incomplete incorporation of thecommon pulmonary vein into the left atrium, leading to apotential inflow obstruction with incomplete reabsorption of thecommon pulmonary vein.6–8 Other earlier proposed develop-mental mechanisms included abnormal growth of the septumprimum,9 entrapment of the common pulmonary vein by theleft horn of the sinus venosus, preventing incorporation into theleft atrium,10 and development of a left atrial membrane byimpingement of a persistent left superior vena cava on thedeveloping left atrium.11 In 1949, a classification scheme wasproposed by Loeffler,8 based on the number and size ofopenings in the left atrial membrane: Group I, no opening(ie, drainage is into the right heart by way of interatrialcommunication or abnormal pulmonary venous connection);Group II, Z1 small opening (a relatively obstructive condi-tion); and Group III, a single wide opening (generally little-to-no obstruction). The shape of the pulmonary venous chamberalso has been used to classify this anomaly.12 The morecommon “diaphragmatic” type consists of a diaphragm of

ith 2 left atrial chambers. Abbreviations: D, distal left atrial chamber;

onary venous drainage; RA, right atrium; RV, right ventricle. (Color

Fig 3. Surgical specimen from resected left atrial membrane.

(Color version of figure is available online.)

Fig 4. (A) Type A defect; (B) Type A1 defect; (C) Type A2 defect; (D) T

online.)

CAPDEVILLE ET AL410

thickened endocardial tissue dividing the left atrium into anaccessory chamber and the true left atrium, and cannot beappreciated externally. The “hourglass” type demonstrates aconstriction that can be seen externally at the junction of theaccessory chamber and true left atrium. Lastly, the “tubular”type, which is visible on external inspection, lacks a membrane;however, a tubular channel receives all 4 of the pulmonaryveins and is considered a common pulmonary vein, with itslower end joining the “true” left atrium. A second classificationscheme was proposed by Lam et al in 1962 (Fig 4A-E): TypeA, in which all pulmonary veins enter the proximal chamber,the distal chamber contains the left atrial appendage and mitralvalve, and there is no ASD; Subtype A1, in which an ASDcommunicates with the proximal chamber; Subtype A2, inwhich an ASD communicates with the distal chamber, as inthis patient; Type B, in which all pulmonary veins drain intothe coronary sinus (a variant of total anomalous pulmonaryvenous connection); and Type C, in which the pulmonary veins

ype B defect; (E) Type C defect. (Color version of figure is available

Table 1. Proposed Classification Schemes for Cor Triatriatum

Loeffler Classification[8]

Group I No opening (drainage into right heart)

Group II Z1 small opening (relatively obstructive condition)

Group III Single wide opening (generally little-to-no

obstruction)

Lam et al Classification[13]

Type A All pulmonary veins enter proximal chamber; distal

chamber contains left atrial appendage and mitral

valve; no ASD

Subtype A1 ASD communicates with proximal chamber

Subtype A2 ASD communicates with distal chamber

Type B All pulmonary veins drain into coronary sinus (variant

of total anomalous pulmonary venous connection)

Type C Pulmonary veins do not communicate with proximal

chamber (rarest type)

Thilenius et al Classification[14]

Type A “Classic” cor triatriatum with variations of partial

anomalous venous return (most common form)

Type A,a Fossa ovalis related to proximal left atrial chamber

Type A,b Fossa ovalis related to distal left atrial chamber

Type B Related to total anomalous pulmonary venous

drainage into coronary sinus; coronary sinus

opening atretic; defects connect proximal left atrial

chamber with right atrium only, and rarely also with

distal left atrial chamber

Type C Superiorly and medially located proximal chamber,

between right and distal left atrium which does not

receive pulmonary vein flow; coronary sinus

normal

Lupinski et al Classification[15]

Type I Intact interatrial septum

Type II ASD communicates with proximal chamber

Type III ASD communicates with lower chamber (80% cases)

Type IV ASD communicates with both chambers

Abbreviation: ASD, atrial septal defect.

CASE 3—2014 411

do not communicate with the proximal chamber (rarest type).13

Other classification schemes also have been proposed and aredescribed in Table 1.14,15

In “partial” or subtotal cor triatriatum sinister, a rarer entity,the left atrium is only partly divided, and one or more of thepulmonary veins may enter the true left atrial cavity. Unilateralpulmonary venous hypertension may result.

Cor triatriatum dexter, also a rarer entity, occurs when theright atrium is separated into 2 chambers by a membrane as aresult of persistence of the right sinus venosus valve.16,17 Theproximal upstream chamber receives blood flow from thesuperior and inferior vena cavae, and the distal chamberincludes the right atrial appendage. This anomaly frequentlyis associated with other right-sided cardiac abnormalities,though isolated cases also have been reported.18 Patients alsohave presented in adulthood.19 Surgical correction is indicatedin symptomatic patients with significant obstruction.20

In most instances, cor triatriatum is an isolated malforma-tion, although it can be associated with a number of othercongenital defects, the most common of which is atrial septaldefect (ASD) or patent foramen ovale. A secundum ASD cancommunicate with either or both chambers. A patent foramenovale almost always communicates with the true left atrium.Mitral regurgitation also has been reported in association with

cor triatriatum, although no true mechanism has beendefined.21,22 Other less common associations include anom-alous pulmonary venous return,23 coarctation with bicuspidaortic valve,24,25 isolated left superior vena cava,26 left superiorvena cava with unroofed coronary sinus,27 subpulmonarystenosis, subaortic stenosis, transposition of the great vessels,mitral atresia, interrupted aortic arch, hypoplastic left ventricle,ventricular septal defect, patent ductus arteriosus,28 tetralogy ofFallot,29 and Ebstein’s anomaly.30 If an ASD that communi-cates with the pulmonary venous chamber is present, partialdecompression can occur, thereby potentially delaying presen-tation (until the ASD becomes symptomatic). Clinical symp-toms can mimic those of anomalous pulmonary venous return.

Cor triatriatum generally is diagnosed in infancy and child-hood, with age at presentation being dependent on the size ofthe membrane fenestration(s), the presence of an atrial septaldefect, atrial fibrillation, and mitral regurgitation. Physiologi-cally, this condition closely can mimic mitral stenosis, depend-ing on the extent of obstruction to inflow.31,32 Thedistinguishing element is diastolic flow in mitral stenosis asopposed to flow throughout the cardiac cycle in cor triatriatum.Pressures in the common pulmonary vein typically are ele-vated, while pressures in the true left atrium are normal.Symptoms are highly dependent on the size of the septalopening(s), which generally are restrictive. Calcification andfibrosis of the openings later in life can precipitate symptoms.Because of a lack of well-defined features on clinical exami-nation, in the absence of symptoms, the condition can goundetected for decades and into adulthood. In fact, theappropriate diagnosis has been mistaken for pulmonary diseasein the absence of appropriate diagnostic studies. In one report, apatient with coexisting COPD, cor pulmonale, and only slightlyelevated PCWP despite severe pulmonary hypertension, pul-monary venous obstruction was masked, and the diagnosis ofcor triatriatum was not made until echocardiography ultimatelywas performed.33 Auscultative findings may include a heartmurmur. Other associated symptoms have included dyspnea,34

orthopnea, and even hemoptysis.35 Atrial fibrillation36 and evencerebral embolism35,37,38 also have been presenting symptoms.It has been suggested that the abnormal septum may be aprecipitating factor for the development of atrial fibrillation,rather than the associated hemodynamic disturbances. In onepatient who underwent surgical correction of cor triatriatum,the presenting symptom of atrial fibrillation completelyresolved postoperatively.39 Another patient with symptomaticdrug-refractory atrial fibrillation incidentally was found to havecor triatriatum during routine TEE examination to rule outthrombus before planned catheter ablation. Intracardiac echo-cardiography facilitated catheter ablation by providing visual-ization of the membrane and passage of the catheter into theappropriate pulmonary vein chamber.40

The natural history depends on the size of the membranefenestrations and whether or not an ASD is present, as well asits location. When the fenestrations are small and in theabsence of an ASD (or the presence of a small ASD),presentation is typically in infancy. Presentation will bedelayed if the membrane fenestrations are less restrictive andif an ASD communicates with the proximal atrial chamber,thereby allowing decompression. In this latter situation, right-

†A.M. Gillinov

CAPDEVILLE ET AL412

sided volume overload eventually manifests. Decompression ofthe lower chamber by an ASD would be unlikely to affectpotentially high pressures in the proximal chamber.

Congenital supravalvar mitral ring, an uncommon subtype ofcongenital mitral stenosis that typically presents early in infancy,also can have a similar presentation to cor triatriatum.41,42 It canoccur in isolation, but in most cases (approximately 90%), it isassociated with other congenital cardiac defects. With thisanomaly, a thick fibrous connective tissue ridge partially orcompletely surrounds the mitral orifice and usually is associatedwith a normal mitral valve apparatus (although the ring mayadhere to the mitral valve and cause leaflet restriction). The ridgeoriginates at the base of the atrial surface of the mitral valve andprotrudes into the mitral valve inlet. Echocardiography easilydistinguishes this entity from cor triatriatum.

In a review of 43 adult cases of cor triatriatum (age range 16to 76 years) presenting as mitral stenosis between 1966 and2004, Slight et al found that pulmonary capillary wedgepressure and mean pressure gradients were significantly greaterin younger adults and that the incidence of atrial fibrillation andmitral regurgitation increased with age.32 Dyspnea was themost common presenting symptom (68%), with palpitationsoccurring next in frequency (27%).

Although cor triatriatum remains a rare condition, notably inadults, it appears to be diagnosed with increasing frequency withthe greater use of imaging techniques. In 2005, fewer than 250cases had been reported.28 Although cardiac catheterization hasbeen used to establish the diagnosis of cor triatriatum,27 echocar-diography is the simplest diagnostic tool and can identify thelocation of the fibromuscular septum, as well as measure gradientsbetween the proximal and distal chambers (velocities less than 1.2m/s are considered nonobstructive) and estimate pulmonary arterypressures using Doppler.43,44 With a highly obstructive septum,pulmonary hypertension can develop. Anatomically, the membranegenerally begins at the superior aspect of the left lateral atrial wall,with variable insertion into the interatrial septum.

Three-dimensional transthoracic45 and transesophagealechocardiography46–48 have been used to better describe theanatomy of this condition, including the size and location ofmembrane fenestrations and membrane dimensions.

The diagnosis also has been made incidentally with computedtomography.49 Three-dimensional multidetector row-computedtomography has been used as an adjunct to echocardiographyto provide reconstruction images that further delineate theanatomy of this condition and accurately identify drainage ofthe pulmonary veins.5 Magnetic resonance imaging also has beenuseful in diagnosing this condition.50

Treatment of cor triatriatum is generally surgical, either viamedian sternotomy or right thoracotomy, and consists ofresection of the membrane separating the common pulmonaryvein chamber from the distal left atrium.51,52 The obstructingmembrane can be approached through either the right or leftatrium. The right atrial trans-septal approach provides excellentexposure, especially in the presence of a small left atrium. Theleft atrial approach opens the proximal common pulmonaryvenous chamber, and provides direct exposure of the mem-brane. The first reports of surgical repair of this defect were in1956.53,54 In earlier times, dilatation of the membrane orificeswas performed using the surgeon’s finger to fracture the

membrane through the left atrial appendage53 or using avalvulotome.54 Percutaneous balloon dilatation of the mem-brane fenestrations also has been performed successfully whenthe membrane anatomy/thickness was favorable.55–58 Recently,the robotic approach to repair of isolated cor triatriatum alsohas been described.59 Modern surgical results are generallyexcellent.28,60 In a review of 28 consecutive patients (predom-inant pediatric population) over a 22-year span, postsurgicalrepair survival was 96% and 88% at 5 and 15 years,respectively, for both isolated defects and those associatedwith other congenital cardiac anomalies.28 Overall life expect-ancy postrepair is expected to be at or near that of the generalpopulation.61 The importance of intraoperative transesophagealechocardiography cannot be overemphasized, and particularattention should be paid to mitral valve function postresection,because of the proximity of the membrane to the valve.62

Timing of surgery can be based on the results of stressechocardiography to assess postexercise gradients and esti-mated pulmonary artery pressures,47 although there is littleinformation about the relationship among clinical symptoms,measured gradients, and long-term prognosis.32 In the case of a70-year-old patient being evaluated for worsening angina anddyspnea, a nonobstructive cor triatriatum was discovered attransthoracic echocardiography, with no specific treatmentrecommended for this abnormal finding.63

Using the classification scheme developed by Lam et al, thispatient had subtype A2 cor triatriatum, with the interatrialcommunication occurring between the right atrium and distalleft atrial chamber. His late presentation was related to the sizeof the fenestrations in the left atrial membrane, and possibly todecompression of the inferior left atrial chamber (in thepresence of mitral regurgitation) by an atrial septal defect.The presence of arrhythmias at the time of evaluation also mayhave been related to the diagnosis of cor triatriatum. Althoughthis pathology has been described, this case adds to the existingreports of this uncommon entity, and highlights the need foradult cardiothoracic anesthesiologists to be familiar withcongenital cardiac anomalies that can present in adulthood.

COMMENTARY 1: COR TRIATRIATUM SINISTER

PRESENTING IN ADULTHOOD†

This report describes a 43-year-old man who underwentopen surgical repair of cor triatriatum, closure of a secundumASD and a MAZE procedure to manage atrial fibrillation.Cardiac surgery certainly was indicated in this situation. Thepatient had a standard approach—median sternotomy—whichprovides excellent surgical visualization and enables manage-ment of all three conditions. But could the same result beachieved less invasively using a surgical robot? There arelimited reports of the robotic approach for cor triatriatum,largely because of the rarity of this condition in the adultpopulation.

Today, patients often seek a less invasive approach forcorrection of structural heart disease. Familiar with stenting toopen coronary arteries and the rapid evolution of percutaneous

CASE 3—2014 413

aortic valve replacement, patients desire minimally invasivesolutions to their heart problems. From a surgeon’s perspective,although the authors have not encountered a report describing aminimally invasive approach for this combination of lesions, itis likely that a robotic approach would have been effective forthis patient.

Robotically assisted heart surgery enables the surgeon toperform exactly the same operation on the heart with smallerincisions and less tissue trauma. This means less blood loss,faster recovery, and a superior cosmetic result. It is important tounderstand that use of the robot entails no compromises in theoperative procedure.

For this case, peripheral perfusion would be used forcardiopulmonary bypass. The femoral artery and the femoralvein would be cannulated under direct vision, and a rightinternal jugular central venous catheter placed by the anes-thesiologist would be exchanged over a guidewire for a secondvenous cannula. Using an intravascular balloon to occlude theaorta, antegrade cardioplegia would be used for myocardialprotection.

After robotic resection of the left atrial membrane, mitralvalve exposure would be standard. A running suture techniqueis used to place an annuloplasty band or ring. A long, flexiblecryoprobe is employed to create the lesions of the MAZEprocedure. The orifice of the left atrial appendage is oversewnfrom the endocardial aspect in the left atrium. The secundumatrial septal defect is closed from the left atrium if primarysuture closure is feasible. If the defect is large, an autologouspericardial patch is used; this is placed from the right atrial sideof the defect.

After robotically-assisted surgery, patients typically spend 1night in the intensive care unit and generally 2 to 4 additionaldays in the hospital. Because there is no sternotomy, return tofull activity is generally possible in 2 to 4 weeks.

COMMENTARY 2: COR TRIATRIATUM SINISTER

PRESENTING IN ADULTHOOD‡

Capdeville et al present a case of a rare congenital cardiacdefect, cor triatriatum sinister (CTS), in a 43-year-old gentle-man who presented with palpitations, chest pain, right jaw pain,and recurrent atrial tachycardia. As previously described, CTSis defined as a membrane within the left atrium that might leadto restricted pulmonary venous return. Asymptomatic caseshave been described in patients without a pressure dropbetween the proximal and distal left atrial chambers49,64 withreports of incidental diagnosis in the elderly.65–67 Although thiscase report details an adult presentation of cor triatriatumsinister, this anomaly often presents during infancy withsymptoms and signs that are different from adults.

Humpl et al investigated the largest group of patients withCTS over the longest period of time (50 years).68 The mostcommon symptoms or clinical findings of the 82 cases werecongestive heart failure (CHF), respiratory complications, fail-ure to thrive, and pulmonary hypertension. Congestive heartfailure also was the most common presentation in 12 patients

‡J. Niezgoda

aged 1 month to 7 years as reported by Gheissari et al.69 Withsignificant pulmonary venous obstruction, the lungs becomestiffer because of venous distention and increased interstitialfluid due to elevated capillary pressure. The decreased lungcompliance causes increased oxygen consumption, alreadydouble that of the adult, and increased cardiac work wheninfants exert themselves when crying or feeding. The dyspneaand feeding difficulty result in poor weight gain and failure tothrive. In a review of 10 cases of CTS, Krasemann et al foundthe most common presentation in children o1 year of age to befailure to thrive.70 The association of recurrent lower respira-tory tract infection, wheezing, and congenital heart diseasepreviously has been described.71,72 In some cases of congenitalheart disease, the only presenting symptom may be in the lung.In CTS, symptoms of wheezing and rhonchi can be caused bythe raised bronchial venous pressure causing edema of thebronchial mucosa and increased bronchial secretions.2,4

Mucosal swelling also may cause chronic cough and hemop-tysis.73 After the infancy period, clinical symptoms present asexertional dyspnea, exercise intolerance or easy fatigability,and cyanosis with strenuous exercise. Unusual presentations ofCTS in children include recurrent syncopal episodes,74 hemo-lytic anemia related to turbulence and shear stress produced byflow through stenosed orifices,75 and incidental finding of anabnormal P wave on an ECG secondary to pacemaker actionfrom specialized tissue in the abnormal septum.76

Most patients (77%) in the Humpl et al study presented withassociated cardiac lesions, of which atrial septal defect (53%),total or partial anomalous pulmonary venous drainage (27%),and patent ductus arteriosus (18%) were the most commondefects. More than one-third of patients (35%) also presentedwith associated noncardiac lesions, mainly chromosomalabnormalities (12%) and respiratory issues (11%).68

Congenital division of an atrial chamber as described in thiscase report is a very rare congenital malformation that morecommonly affects the left atrium. Cor triatriatum dexter (CTD),division of the right atrium, is even rarer. The CTD membranerepresents the right-sided valve of the embryonic sinusvenosus.77 Normally, this valve regresses early in fetal lifebetween 9 and 15 weeks gestational age; however, remnantsare not uncommon and are recognized as the normal eustachianand thebesian valves and the crista terminalis.78 The purpose ofthis valve in the fetus is to deflect preferentially more highlyoxygenated blood from the umbilical vein and inferior venacava through the foramen ovale to the left atrium. Therefore,organs of the highest oxygen consumption, the fetal brain andheart, are perfused with blood with the highest oxygen contentin utero. Persistence of the right sinus valve results in aseparation of the right atrium into two separate chambers: Thesuperior portion receives systemic venous return from theinferior and superior vena cava, whereas the inferior portioncontains the right atrial appendage and the orifice of thetricuspid valve.

Similar to CTS, the clinical manifestations of CTD aredependent on the degree of right atrial obstruction. However,moderate obstruction in neonates with CTD usually is diagnosedrapidly because of the severe cyanosis from right-to-left shuntingacross the atrial septum, triggering a neonatal cardiac work-up, asopposed to CTS, which presents with a myriad of symptoms,

CAPDEVILLE ET AL414

including failure to thrive, feeding intolerance and respiratorycomplications that might not indicate further work-up until thepatient has more cardiovascular symptoms. With minor degreesof obstruction, patients may remain clinically silent for sometime or detected incidentally by echocardiography at surgery orat autopsy.79 The obstructed right atrium also may present withsymptoms consistent with increased portal venous pressureresulting in ascites or weight loss. During fetal life evidenceof CTD may be picked up on routine obstetric scans. Markedfetal nuchal edema may be associated with significant obstruc-tion of the right ventricular inflow.80 Also, significant obstruc-tion may lead to the underdevelopment of the right heartstructures: Tricuspid valve abnormalities including Ebstein’sanomaly, hypoplastic right ventricle, and pulmonary stenosis oratresia. Diagnostically, the remnant valves appear as a ‘‘wind-sock’’ within the right atrium on transthoracic or fetal echo-cardiography.81 Surgical relief is recommended only in thesymptomatic patient.

In summary, both cor triatrium sinister and dexter are rarecongenital cardiac defects that could present anytime from the

neonatal period, adulthood or necroscopy. Cor triatriatumpresenting as pulmonary congestion, pulmonary edema, cardio-genic shock or severe cyanosis in infancy requires urgentsurgery. However, cardiac malformations involving low-pressure chambers (ie, either of the atria) in general are moredifficult to diagnose. For example, atrial septal defects or partialanomalous pulmonary vein connections are diagnosed morecommonly later in life than lesions that involve high-pressuresystems, such as ventricular septal defects. The diagnosis ofprimary cardiac disease requires a very high index of suspicionon the part of the physician when there are no significant cardiacfindings on physical examination. In cor triatriatum, asthma orwheezing or pulmonary hypertension of unknown etiology mayconstitute the only evidence of underlying heart disease.

APPENDIX A. SUPPLEMENTARY DATA

Supplementary data associated with this article can be foundin the online version at http://dx.doi.org/10.1053/j.jvca.2013.08.018.

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