In PTA, there is a large VSD. PA arises from the truncus. In SV, one great vessel arises from the SV while the other arises from a rudimentary chamber which is connected to the SV by the bulboventricular foramen.

Both PTA and SV are similar. The pressures and oxygen saturation in both ventricles are the same. Clinical picture depends on whether there is PS or not. If there is PS, there will be cyanosis. If there is no PS, there will be heart failure.

ECG shows BVH. In SV, all precordial leads may show the same pattern.