A 32-year-old female patient presented with complaints of palpitations and exercise intolerance for the past 6 months. Palpitations were intermittent and irregular and lasted for hours. She has had New York Heart Association class 1 dyspnea on exertion for the past 6 months. She had been very active and was previously able to run a marathon. There was no history of syncope or chest pain. She had no other chronic medical problems and had no prior cardiac history. She did not smoke or use illicit drugs, and there was no family history of sudden cardiac death. Her vitals were normal. There was no jugular venous distension or pedal edema. Cardiac examination revealed a nondisplaced apical impulse, normal S1 and S2, and no murmurs. The remainder of the physical examination was unremarkable. Complete blood count and basic metabolic profile were within normal reference range. An electrocardiogram revealed normal sinus rhythm without ST-T changes. A transthoracic echocardiogram (Figure 1) was performed, followed by transesophageal echocardiogram (Figure 2).
What is the diagnosis?
The correct answer is: A. Cor triatriatum sinistrum
The patient should have been diagnosed with cor triatriatum sinistrum. Echocardiography demonstrated the presence of a membrane traversing the left atrium, dividing it into superior and inferior chambers. The left atrial appendage and fossa ovalis were present distal to the membrane, which is consistent with cor triatriatum. There were two fenestrations in the membrane with mild restriction of blood flow. The mean gradient across the membrane was 10 mm Hg. All four pulmonary veins drained into the superior chamber. There was no evidence of patent foramen ovale or atrial septal defect or left sided superior vena cava. No other valvular abnormalities were present. Answer B (Lutembacher syndrome) is defined as a combination of mitral stenosis and shunt at the atrial level, which makes it the incorrect diagnosis. The patient underwent an uncomplicated surgical resection of the membrane.
Cor triatriatum sinistrum is a rare congenital malformation that occurs in about 0.4% of patients with congenital heart disease.1 Cor triatriatum sinistrum is characterized by three atrial "cavities," namely a normal right atrium and proximal and distal left atrial chambers. Cor triatriatum dexter is operant when the right atrium is divided. Embryological basis of this anomaly is abnormal growth of septum primum or incorporation of the embryonic common pulmonary vein into the left atrium.2 Presentation can range from infancy to late adulthood and is dictated by the degree of obstruction to flow by the membrane. Mild degrees of obstruction may present in adulthood with dyspnea on exertion. In patients with severe obstruction, presentation can mimic mitral stenosis.3 Patients are at risk for cardioembolic events and atrial arrhythmias. Associated anomalies of the atrial septum and pulmonary veins, as well as left sided superior vena cava, need to be excluded.4 Echocardiography is diagnostic. In symptomatic patients, surgery is the definitive treatment.4
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