CXR pearls

Normal cardiac silhouette

• in a newborn, the typical normal cardiac silhouette is rarely seen due to a large thymus, which is a finely reticulated structure
• PA view:
  • RV is not on a border (unless there is RV dominance, then the RV can compose the Left border)
  • Right border (top to bottom) SVC, RA
  • Left border (top to bottom) aortic knob, MPA, L atrial appendage (not prominent in nl heart), LV
• Lateral view
  • anterior border: aortic knob, PA knob, RV
  • posterior border (top to bottom): LA, LV

Cardiomegaly

• cardiothoracic ratio: take the largest heart size over the largest chest dimension. + If > 0.5  - unreliable in infants/kids with poor insp effort
• isolated right ventricular enlargement best seen on lateral film
• volume overload can lead to enlarged heart on CXR
• pressure overload is best seen on ECG

LA enlargement

• lateral: posterior protrusion
• PA: double density, LAA (left atrial appendage) prominent on L cardiac border with great enlargement, L mainstem bronchus elevation, barium filled esophagus is indented, pushed to the right

LV enlargement

• PA: apex is displaced Leftward and Downward
• Lateral: posterior cardiac border pushed more posterior and meets IVC below diaphragm level (normally meets IVC above diaphragm)

Right Atrial Enlargement

• PA: increased prominence of R lower silhouette (false + and negs)

R ventricular enlargement

• RV does not make the silhouette in the PA view - may be nl CT ratio
• in lateral view, it fills the retrosternal space

Congenital heart lesions

• boot shaped heart and decreased pulm blood flow (concave main pulmonary artery segment): consider TOF, tricuspid atresia.
• egg on a string, increased PBF, cyanosis: TGA (narrow waist due to absence of large thymus and abnormal relationship of great arteries
• snowman sign, increased PBF: supracardiac TAPVR (head of snowman = L vertical vein, L innominate vein and dilated SVC)

Other

• normally, the trachea will deviate to the right in children due to pressure from aorta; if trachea is midline, consider interrupted arch
• umbilical artery line to T7; umbilical vein line, to just above diaphragm
• superior rib notch: hyperparathyroid, polio, collagen vasc dz (RA, SLE), OI, marfan