X-ray chest PA view gives a good assessment of the cardiac size. It is taken with the film in front of the chest and the X-ray tube behind, from a distance of 6 feet. This view avoids magnification of the heart as the film is close to the anterior chest wall. PA view is identified by the presence of the fundal gas bubble and the absence of the scapulae in the lung fields. Side of the liver shadow gives a hint to the situs, being solitus if it is on the right side. The left cardiac border is formed by the aortic knuckle, pulmonary bay, left atrial appendage and left ventricle from above downwards. Right border is formed mostly by the right atrium, while a small portion of the inferior vena cava and superior vena cava may be seen. Ascending aorta may form the right upper border, especially if it is dilated. Indendation of the tracheal air shadow on the left side by the aortic arch indicates a left sided arch and vice versa.