Ans. b (Left atrial enlargement) (Ref: Grainger's Diagnostic Rad., 4th/pg. 787)In ASD, Chest x-ray shows an enlarged right atrium and right ventricle, and pulmonary artery and its branches; increased pulmonary vascular markings of left-to-right shunt vascularity will diminish if pulmonary vascular disease develops.ATRIAL SEPTAL DEFECT (ASD)# The three types of ASD include ostium secundum or fossa ovalis defect, sinus venosus defect, and endocardial cushion defects (ECD).# If the left to right shunt (ASD) produces a shunt ratio greater than 2:1, the heart is obviously enlarged, involving RA and RV.# There is no enlargement of the LA, except in few cases of ECD or Lutembacher syndrome.# CXR:- The heart in ASD is sometimes displaced to left.- The ascending aorta and its arch tend to appear smaller than normal, probably due to the rotation of ascending aorta by enlarged RA and RV, causing sagittal alignment of the aortic arch (Small aortic knuckle).- The central pulmonary arteries are enlarged and there is a variable degree of pulmonary plethora, depending on the size of shunt.- Septal lines (Kerley B lines) in a patient of ASD should always suggest an associated mitral valve abnormality (ECD or Lutembacher syndrome).# More features:# The "great hilar dance" sign characterizes ASD on fluoroscopy.# The "Goose-neck" deformity is seen in ASD on cardioangiography.# Rx: Operative repair, usually with a patch of pericardium or of prosthetic material or percutaneous transcatheter device closure, if the ASD is of an appropriate size and shape, should be advised for all patients with uncomplicated secundum ASD with significant left-to-right shunting, i.e., pulmonary-to-systemic flow ratios 2:1. Excellent results may be anticipated, at low risk, even in patients >40 years, in the absence of severe pulmonary hypertension. Patients with sinus venosus or ostium secundum ASDs rarely die before the fifth decade.