Which of the following show splaying of carina in retro cardiac shadow
ANSWER: (A) Left atrium enlargementREF: Sutton s textbook of radiology, 7th edition, volume 1 page 284Left atrial enlargement in 5 directions:(out of all 6 directions, inferior enlargement is not seen)It is believed left atrial appendage enlargement occur early. Left atrial Appendage enlargement is seen as fullness beneath the pulmonary artery shadow. It may be the earliest finding of Left atrial enlargement in X-ray. (This may appear as straight left heart border, as in classical mitral stenosis). The Left atrial appendage enlargementis not necessarily in proportion with left atrial enlargement.Left atrium could also enlarge posteriorly by pushing the esophagus towards the spine. This is visible only in barium swallow.Then LA can enlarge either to left or right (Usually towards right) and reach the right heart border or over shoot it and form the right heart border by itself. This occurs very late in the course.The other direction LA goes on to enlarge is superiorly. When LA enlarges superiorly it hits on the left main bronchus and lifts it. This is measured by the widened subcarinal angle which is normally less than 75 degrees.LA can enlarge anteriorly sometimes, but it is resisted by right ventricle but rarely right ventricle yields to the LA push and produces a left parasternal lift which could be mistaken for RV enlargement.Inferior enlargement cannot happen in a significant way as it is limited by the AV groove and strong fibrous skeleton. The upper limit of normal LA size is around 4.5cm.
Left atrium enlargement
Left ventricle enlargement
Right atrium enlargement
Right ventricle enlargement
Cardiac and Pericardiac Imaging