Dynamic Features of Cor Triatriatum Sinister

Graphical abstract

Highlights

• •CTS is a left atrial growth that can cause forward flow obstruction.
• •Echocardiography is an important tool in identifying the hemodynamic impact of CTS.
• •PLSVC is a common congenital malformation seen in CTS.
• •HL exacerbates forward flow obstruction CTS.

Introduction

Cor triatriatum sinister (CTS) is a rare congenital cardiac condition in which a fibromuscular membrane divides the left atrium into two distinct chambers: an accessory posterior chamber that drains the pulmonary veins and the anterior true left atrium, which provides outflow through the mitral valve.^1,2 Communication between these chambers occurs through one or more perforations in the anomalous membrane.³ The condition is functionally analogous to mitral stenosis, although the degree of obstruction is highly variable in its anatomy. A parallel anomaly can occur in the right atrium (cor triatriatum dexter), although this does not share similar clinical implications and is not discussed in this report.

Given its rarity and immense variation in anatomy and resultant clinical presentation, the existing literature on CTS is limited primarily to case reports. The etiology remains largely unknown, although several theories have been proposed to explain the embryologic pathogenesis of CTS. The “malincorporation” theory argues that the common pulmonary vein fails to completely incorporate into the posterior left atrium, leading to the formation of an accessory chamber.⁴ The “entrapment” theory acknowledges the high prevalence of persistent left superior vena cava (PLSVC) in patients with CTS and explores possible interference in cardiac development due to impingement of developing structures by an aberrant PLSVC.⁵ The “malseptation” theory attributes membrane formation to the overgrowth of the septum primum.⁶

We present a unique case in which severe leukocytosis secondary to leukemia produced a dynamic obstruction in a pediatric patient with previously undiagnosed CTS.

Case Presentation

We describe a previously healthy 13-year-old patient presenting with fever, cough, acute dyspnea, and orthopnea. Before the onset of symptoms, the patient was reportedly physically active without limitations, although they endorsed recent mild decline in athletic performance. The patient was tachypneic and tachycardic with acute hypoxic respiratory failure requiring noninvasive oxygen supplementation to maintain normal saturations.

Initial examination revealed a pale, ill-appearing patient with audible rales and crackles in the left lower lung field, delayed capillary refill, and cool extremities with appropriate pulses, without audible murmur or gallops. Pertinent laboratory results included marked leukocytosis to 192,700/μL, 89% blasts, thrombocytopenia with a platelet count of 65,000 μL, elevated inflammatory markers (ferritin 1,065 ng/mL, fibrinogen 1,015 mg/dL), elevated D-dimer (1.70 μg/mL), B-type natriuretic peptide 2,816 pg/mL, and lactate dehydrogenase 1,436 U/L. Peripheral flow cytometry revealed high-risk B-lymphoblastic leukemia.

Chest radiography demonstrated diffuse hazy opacities bilaterally concerning for pulmonary edema. Transthoracic echocardiography (TTE) and transesophageal echocardiography revealed a membranous structure separating the left atrium into two cavities consistent with CTS (Figures 1 and 2, Videos 1 and 2). Doppler-derived pressure gradient across the membrane was an estimated peak 40 mm Hg and mean 20 mm Hg (Figure 3), during which time the heart rate of the patient was at 158 beats/min. Evidence of right ventricular (RV) and pulmonary arterial (PA) hypertension was demonstrated. RV systolic pressures were >40 mm Hg (compared with the recorded systemic blood pressure of 111/85 beats/min); no pericardial effusion was noted. Biventricular systolic function was normal. Electrocardiography demonstrated normal sinus rhythm with a prolonged corrected QT interval (493 ms by Bazett’s criteria).

Figure 1.

Two-dimensional TTE, apical four-chamber (pediatric, apex down) systolic view, demonstrates a large echo-bright membrane (arrow) within the left atrium, consistent with the CTS. LV, Left ventricle; RA, right atrium.

Figure 2.

Three-dimensional transesophageal echocardiography, volume-rendered reconstruction short-axis view from the perspective of the left atrium, demonstrates the left-sided cor triatriatum (arrow), with a minimally obstructive membrane.

Figure 3.

Two-dimensional TTE, apical four-chamber view–guided continuous-wave spectral Doppler display, demonstrates a peak gradient of 40 mm Hg and a mean gradient of 20 mm Hg (arrow) across the obstructive CTS membrane.

Given the degree of leukocytosis and high risk for tumor lysis syndrome following the initiation of chemotherapy, hyperhydration therapy was initiated. Concurrent diuresis with furosemide was pursued to prevent worsening pulmonary edema. The patient was sedated and intubated in the operating room for a bone marrow biopsy and collection of a cerebrospinal fluid sample via lumbar puncture. The patient remained intubated postoperatively because of respiratory decline presumed secondary to pulmonary edema.

A peripherally inserted central catheter was placed via the left upper extremity and was found to course through the left chest (Figure 4), which raised concern for PLSVC. This finding was later confirmed during the surgical repair of the CTS. On TTE, the coronary sinus appeared dilated, a right superior vena cava draining to the right atrium was confirmed, and PLSVC was not visualized (Figure 5, Video 3). The atypical superior location of the coronary sinus limited our ability to make the diagnosis of PLSVC on TTE. The catheter was removed, and a right internal jugular central venous line was placed. Chemotherapy was promptly initiated, and with fluid management, serial echocardiography showed marked improvement in the mean gradient across the fibrous membrane to 3.5 mm Hg. The patient tolerated extubation and weaning of respiratory support. At the time of discharge, there was leukopenia to 400/μL and a B-type natriuretic peptide level of 219 pg/mL.

Figure 4.

Chest radiography, posteroanterior view, demonstrates the central venous line coursing through the left chest with catheter tip (arrow) seen in the left superior vena cava.

Figure 5.

Two-dimensional TTE, parasternal long-axis systolic view, demonstrates the dilated coronary sinus (arrow), suggesting a PLSVC. LA, Left atrium; LV, left ventricle.

In favor of progressing with the chemotherapy regimen, surgical repair of the CTS was deferred until completion to ensure adequate wound healing and recovery. Serial echocardiography was performed with each hospitalization during chemotherapy and after recovery (Figure 6). Following the high-volume prehydration required for the chemotherapy protocol, the mean gradient across the atrial membrane fluctuated between 3.5 and 6.7 mm Hg. The patient remained asymptomatic and completed the chemotherapy course. Surgical repair was pursued 3 years after initial presentation, with complete resection of the 2- to 3-mm-wide fibrous tissue band encircling the left atrium. The CTS orifice diameter was found to be 11 × 13 mm.

Figure 6.

Two-dimensional TTE, apical four-chamber (pediatric, apex down) systolic view obtained on postoperative day 2, demonstrates improved patency of the left atrium (LA) after surgical resection of the CTS membrane. LV, Left ventricle; RA, right atrium.

Discussion

Considering the extensive anatomic variations of CTS, the onset of symptoms and clinical presentation may be highly inconsistent, making this diagnosis challenging. In review of one institution’s database, CTS was found to be an asymptomatic, incidental finding in 24% of patients, while 65% of patients presented with cardiac symptoms.⁷ CTS is rare, constituting a mere 0.1% to 0.4% of all congenital cardiac defects, reflecting the importance of describing this pathology’s implications across broader patient contexts.^2,4,8 This case uniquely describes the hemodynamic implications of CTS, which in this case were exacerbated because of underlying hyperleukocytosis (HL) and thus a cause for both clinical vigilance and eventual surgical intervention.

The symptoms of CTS are secondary to transmembrane obstruction, causing a rise in pulmonary venous pressures, leading to upstream PA hypertension and elevated RV pressures.^2,9 The decreasing size of fenestration within the fibrous membrane of CTS bears a negative correlation with the obstruction of flow through the left atrium. Patients with restrictive fenestrations had increased pulmonary capillary wedge pressure, significant transmembrane mean pressure gradient, and overall symptomatic, early presentation.¹⁰ In this case, we describe a dynamic feature of CTS, as this patient’s membrane fenestration became restrictive only in extraordinary circumstances of the oncologic diagnosis. Furthermore, it is important to differentiate CTS (located superior to the left atrial appendage orifice) from the similar appearance of supravalvular mitral stenosis (located inferior to the left atrial appendage orifice).

HL, defined by a white blood count exceeding 100,000/μL, and the resultant leukostasis common in acute leukemia have been shown to have vascular complications, yielding cardiac dysfunction.¹¹ Multiple previous case reports have documented increased PA pressure in the setting of hyperviscosity, leading to PA hypertension and acute right heart failure in these patients with normal cardiac anatomy.¹² In this patient, the synergistic effects of leukostasis and restrictive CTS on RV pressures increased the risk for cardiopulmonary collapse. For this reason, fluid management focused on balancing hydration for HL with diuresis for pulmonary congestion plays an important role in ensuring hemodynamic stability. In this case, it was challenging to distinguish the contribution of HL from CTS to the echocardiographic findings of RV and PA hypertension. However, the peak pressure gradient of 40 mm Hg across the membrane demonstrated a hemodynamically significant restrictive lesion, which supported these echocardiographic findings. Although at the time of performing imaging, the patient was tachycardic, which could functionally increase the gradient across the membrane by decreasing diastolic flow time, a significantly high gradient due to the restrictive morphology of the membrane was likely present. In a previous study, patients with left atrial pressure gradients as low as 4 mm Hg were found to have symptomatic heart failure.¹³ Apart from the initial effects of leukostasis, the dynamic obstructive features of CTS in this case are redemonstrated with changes in peak membrane gradients before and after high-volume chemotherapy treatments without HL. For this reason, close cardiac monitoring throughout the completion of chemotherapy was a vital component of the presented case.

Consistent with the theory of “entrapment” and the role of the PLSVC in embryologic development of CTS, the presence of PLSVC in this patient is not unexpected.⁵ The impingement of PLSVC on the left atrial wall is thought to induce cellular proliferation and membrane formation.⁵ In a previous study, this association was determined to be more frequent than any other anatomical variant, found in 21% of patients.¹⁴

Surgical management was pursued in our patient in the setting of hemodynamically significant CTS. Even in cases of hemodynamically insignificant or asymptomatic CTS, surgical management should be considered in efforts to prevent long-term complications. Chronic calcification may ensue in adults without previously significant obstruction, causing a restrictive lesion with impaired left ventricular filling. In this case, perimembrane fibrosis, as well as structural left atrial changes, may lead to atrial fibrillation.¹⁵

Conclusion

Largely undiagnosed, CTS is a rare congenital abnormality. Although the hypothesis and anatomy that predispose to its development have no consensus in embryology, the presence of CTS may precipitate a restrictive physiology for PA forward circulation, contributing to increased pulmonary pressures. Among pediatric patients, conditions exacerbating these dynamics can produce severe consequences. In this case, hyperviscosity secondary to a new oncologic diagnosis was hypothesized to predispose to hemodynamic collapse. If a diagnosis of CTS is known, clinicians must be aware of its potential implications and remain vigilant in the prevention and treatment of these lesions.

Ethics Statement

The authors declare that the work described has been carried out in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki) for experiments involving humans.

Consent Statement

The authors declare that since this was a non-interventional, retrospective, observational study utilizing de-identified data, informed consent was not required from the patient under an IRB exemption status.

Funding Statement

The authors declare that this report did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Disclosure Statement

The authors report no conflict of interests.

Supplementary Data

Video 1

Two-dimensional TTE, apical four-chamber (pediatric, apex down) view, demonstrates normal left ventricular size and systolic function, and a large echo-bright mobile membrane within the left atrium, consistent with the CTS.

Video 2

Three-dimensional transesophageal echocardiography, volume-rendered reconstruction short-axis view from the perspective of the left atrium, demonstrates the left-sided cor triatriatum with a minimally obstructive membrane; the mitral valve can be seen moving in the far field.

Video 3

Two-dimensional TTE, parasternal long-axis view, demonstrates normal left ventricular size and systolic function and the dilated coronary sinus, suggesting a PLSVC.