TOF accounts for most of the cyanotic congenital heart diseases and 12% of all congenital heart disease.
Four features of TOF are
1) High, large VSD
2) Overriding of aorta
3) Pulmonary stenosis
4) Right ventricular hypertrophy
Clinical picture will depend upon VSD and severity of pulmonary stenosis.
Radiology
The heart is not usually enlarged at birth.
The classic coeur en sabot silhouette is due to combination of deeply concave pulmonary bay and elevation of cardiac apex.
The peripheral pulmonary vasculature will show oligaemia proportionate to degree of cyanosis.
The ascending aorta is always enlarged and proportionate to the degree of cyanosis.
In about 25% of the cases the aortic arch is on right side (with mirror image branching), the descending aorta usually crossing to the left of the spine.
In case of sever right ventricular obstruction MAPCAs (major aorta pulmonary collateral arteries) will be seen on Angiocardiography.
Echocardiography
It is the reliable method of diagnosing the TOF.