Septum Primum Malposition: An Uncommon Cause of Right Ventricular Volume Overload

A 24-year-old woman was hospitalised for a systolic murmur with exertional fatigue. Transthoracic echocardiography found an enlarged right heart, mild pulmonary hypertension (39 mmHg systolic pressure), and an interatrial septum exhibiting a leftward deviation of its dorsocranial insertion (Figure 1A; Supplementary Video 1). On Doppler examination, partial anomalous pulmonary venous drainage (PAPVD) to the right atrium (RA) was suspected (Figure 1B; Supplementary Video 2). Transoesophageal echocardiography demonstrated an interatrial septum aneurysm and a patent foramen ovale with a right-to-left shunt (Figure 1C; Supplementary Video 3).