What is indicated by a boot-shaped heart on x-ray?

A boot-shaped heart on an X-ray is indicative of Tetralogy of Fallot, a congenital heart defect characterized by four specific anatomical abnormalities: ventricular septal defect (VSD), pulmonary outflow tract obstruction (pulmonary stenosis), right ventricular hypertrophy, and an overriding aorta. This unique configuration gives the heart a characteristic "boot" appearance due to the right ventricular hypertrophy and the position of the aorta, which sits directly over the ventricular septal defect.

In the case of Tetralogy of Fallot, the right ventricle works harder to pump blood through the narrowed outflow track to the pulmonary arteries, leading to hypertrophy of the right ventricular muscle. The resultant shape is what contributes to the boot-like silhouette seen on chest X-ray. This appearance is not typically associated with conditions such as atrial septal defect, mitral valve prolapse, or congestive heart failure, as those conditions present differently on imaging and produce different physiologic and structural changes within the heart that do not result in the characteristic boot shape.