What is Stag Antler sign?
On a chest radiograph, dilated and branching upper zone pulmonary veins resemble the antlers of a stag. Pulmonary venous hypertension results in redirection of blood in the pulmonary veins to the upper zones. The most common causes are left heart failure and fluid overload
What is normal Cardiothoracic ratio?
The cardiothoracic ratio is measured on a PA chest x-ray, and is the ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter (inner edge of ribs/edge of pleura). A normal measurement is 0.42-0.50. A measurement <0.42 is usually deemed to be pathologic. A measurement >0.50 is usually taken to be abnormal although some radiologists feel that measurements up to 0.55 are "borderline".
Dilated and branching upper zone pulmonary veins resemble the antlers of a stag