Cor triatriatum sinister is a rare congenital cardiac malformation, usually diagnosed in childhood. Diagnosis and follow up of cor triatriatum sinister is entirely possible by minimally invasive methods such as transthoracic and transesophageal 2D and 3D echocardiography. These methods are the mainstay of the follow up of this rare cardiac anomaly, whose rarity can contribute to its misdiagnosis, but when correctly diagnosed and managed, it has an excellent outcome (1).

We describe a case of maternal cor triatriatum diagnosed in an adult age and its successful conservative management throughout pregnancy until postpartum.

A 30-year-old gravida with an asymptomatic, recently diagnosed, cor triatriatum sinister was referred to our institution for cardiac re-evaluation. She has had a history of heart murmur since childhood, but she has never been properly evaluated because she tolerated effort well.

On physical examination she had regular pulse and normal blood pressure. Cardiac auscultation revealed fixed splitting of the 2nd heart sound without accentuation of P2 and a pansystolic murmur at the apex. Blood test results as well as ECG recording were both unremarkable. Transthoracic and transesophageal 2D and 3D echocardiogram documented a fibromuscular membrane across the left atrium, dividing it into two compartments, with the proximal one receiving the pulmonary venous flow. The two chambers communicated via an orifice with an area of 1.41 cm2. The continuous wave Doppler across the membrane showed a diastolic intraatrial mean gradient of 6 mmHg. All other echocardiographic findings were also normal, without any indirect signs of elevated pulmonary pressures. There were no other associated cardiac anomalies (Figures 1-4).

Since there were no persisting symptoms or signs of heart failure, in cooperation with a gynecologist, we decided to continue the conservative approach. The patient was put on a low dosage of beta blocker, while prescribing bedrest and reduction of water intake. Close surveillance throughout the pregnancy was maintained, which was uneventful. Routine transthoracic echocardiography repeatedly showed normal findings without development of pulmonary hypertension and NT-proBNP levels remained normal. A healthy baby girl was successfully delivered by a normal vaginal birth at 38 weeks’ gestation, without any complications.

Cor triatriatum sinister is a rare congenital cardiac abnormality first described by Church in 1868 (2) with an estimated incidence of 0.1% of all congenital heart diseases with a ratio of men to women 1.5:1. (3) Cor triatriatum is most commonly diagnosed in infancy or childhood, but in some cases it is not diagnosed until later (4, 5) and then mostly incidentally (6). The clinical features mimic those of mitral stenosis. Pathophysiologically the obstructive nature of the membrane leads to the creation of a pressure gradient with an associated rise in pulmonary arterial and venous pressures and the most common symptoms present in adults are dyspnea, hemoptysis, and orthopnea. Like mitral stenosis, cor triatriatum may represent a great challenge in management of pregnancy and delivery (7).

During the course of pregnancy, hormonally mediated changes result in an increase in red blood cell mass and heart rate (8), and are thus associated with a 40% increase in blood volume and cardiac output (9).

In this case, due to hemodynamic similarities, we decided to treat the cor triatriatum sinister like a moderate asymptomatic functional mitral stenosis. The patient routinely underwent controls once a month, when an echocardiogram was performed with measurements of pulmonary pressures and the gradient across the membrane orifice. She remained asymtomatic all the time, without any signs of heart failure and with normal NT-proBNP levels.

In this setting the left ventricle has increased afterload and limited preload due to cor triatriatum — a combination that tends to worsen the cardiac output. Prevention of tachycardia and atrial dysrhythmias is vital to ensure adequate left ventricular preloading along with avoiding sudden decrease in systemic vascular resistance, while the pulmonary capillary bed is extremely prone to pulmonary edema, especially during delivery. It is also important to avoid any increase in the central blood volume by extraneous administration of fluids. We decided to introduce a beta-blocker in order to extend the diastolic filling, but due to a relatively low systemic blood pressure, we also decided to refrain from giving a diuretic; instead we focused on water intake control. Literature also prefers cesarean section to vaginal delivery in such circumstances, but the gynecologist in charge chose the latter approach in agreement with the gravida, which took a normal course.

Along with clinical controls, regular echocardigraphic controls have a central place in the follow up of gravida with congenital cardiac anomalies. To the best of our knowledge, this case is the first case of maternal cor triatriatum sinister in Croatia.