Ventricular septal defect and bidirectional shunting? Things are not what they seem.

This report describes the case of a 19-year-old woman with a diagnosis of muscular ventricular septal defect. Bidirectional shunting was observed during a transthorathic echocardiography evaluation which also suggested normal pulmonary arterial pressure. Moreover, anomalous and hypertrophic right ventricular muscular bands were observed. After having ruled out other possibilities, the plausible explanation is one, which is not described in the literature. The findings may be explained as a sequestrated portion of the cavity of the right ventricle that remains isolated from the rest of the right ventricle (RV) by anomalous and hypertrophic right ventricular muscular bands, with communication only between the left ventricle and the sequestrated part of the RV. This is an unusual variant of two-chambered RV simulating two-chambered left ventricle.