If the ECG shows a right axis deviation which is abnormal or a right bundle-branch block (this would mean there was no signal going through the atrium to instruct the ventricle to contract or squeeze blood out of the ventricle). Chest radiogram
A chest radiogram can be given to a patient to determine:
Pulmonary plethora: the test will help to determine if there is a left-to-right shunt meaning the blood is flowing from the left atrium to the right through a hole between the two atria. Mild left atrial enlargement: the test will help to determine if the left atrium is enlarged due to alternate blood flows
Right ventricular enlargement: the test will help to determine if the ventricle is enlarged due to a surge of blood above normal or if the ventricle is having to work harder than normal to pump blood out of the ventricle. Pulmonary artery enlargement: the test will help to determine if there is a large volume of blood in the pulmonary veins and arteries than normal
Mitral Valve calcification late in life: the test will help to determine if the mitral valve or flaps are becoming hardened and losing their floppiness. pulmonary vascular congestion, marked left atrial enlargement: the test will help to determine if there is a sign of MS and small ASD and how severe both are. Transthoracic or Transesophageal echocardiography
Transthoracic or Transesophageal echocardiography two dimensional images that can be made of the heart. They can be used to determine the stages of Lutembachers syndrome.
External links

Life or Limb: What happens when your leg gets trapped under a building?