Cardiovascular evaluation is a prerequisite before planning surgical separation of thoraco-omphalagus twins, as the degree of cardiac involvement is one of the limiting factors for success.

A set of 10 day old female thoraco-omphalagus twins presented with a protomesosystolic murmur suggesting a ventricular septal defect. Because of restrictive windows, cardiac ultrasound could not differentiate between a ventricular septal defect and a shunt between the left ventricle of one twin with the right ventricle of the other. Magnetic resonance imaging was not helpful but showed two separated hearts with a common pericardial sac. Cardiac catheterisation was performed through a retrograde approach—right femoral artery for the left twin and left femoral artery for the right twin. It showed that there was no communication between the hearts but a muscular septal defect in the right twin allowing filling of the pulmonary artery (arrow). Each heart has its own normal coronary artery supply. The apex of each heart enters the opposite chest. The anatomy was confirmed at surgery and the twins underwent successful separation.

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