Chest X-ray Abnormalities Cardiac contour and pulmonary oedema
Key points
If the heart is enlarged – look for signs of heart failure (upper zone vessel prominence, pulmonary oedema and pleural effusions)
Pulmonary oedema manifests in two forms – interstitial oedema (septal lines), and alveolar oedema (airspace shadowing/consolidation)
When the heart is enlarged it is sometimes possible to determine if a specific heart chamber is enlarged
The heart contour may be abnormal due to cardiac or pericardial disease
The heart contour may be obscured by adjacent lung disease
Cardiomegaly and heart failure
If the heart is enlarged – Cardio-Thoracic Ratio (CTR) >50% – then look for other features of heart failure. Check specifically for upper zone vessel enlargement, signs of pulmonary oedema, and pleural effusions.
Upper zone vessel enlargement
The upper zone vessels are normally smaller than the lower zone vessels. Prominence of the upper zone vessels such that they are the same size or larger than the lower zone vessels is a sign of increased pulmonary venous pressure.
Upper zone vessel enlargement (1) – a sign of pulmonary venous hypertension
Septal (Kerley B) lines (2) – a sign of interstitial oedema – see next picture
Airspace shadowing (3) – due to alveolar oedema – acutely in a peri-hilar (bat's wing) distribution
Blunt costophrenic angles (4) – due to pleural effusions
Clinical information
Worsening exercise tolerance
Chronic uncontrolled hypertension
Rapid onset of shortness of breath
Atrial fibrillation
Diagnosis
Left ventricular failure with pulmonary oedema
Pulmonary oedema
Pulmonary oedema manifests in two forms – interstitial oedema and alveolar oedema.
Interstitial oedema - septal lines (Kerley B lines)
Septal lines (also known as Kerley B lines) are caused by thickening of the interlobular septa which separate the secondary lobules at the periphery of the lungs. They may be very subtle, but if seen in the context of clinical suspicion of heart failure, then septal lines are a strong indicator of interstitial oedema.
Septal lines are a specific sign of interstitial oedema in the context of suspected heart failure
Differential diagnosis
If there is no clinical suspicion of heart failure, then conditions that cause lymphatic obstruction – such as sarcoidosis or lymphangitis carcinomatosa – should be considered a possible cause of septal lines
Alveolar oedema
As interstitial oedema progresses, fluid leaks from the interstitial tissue into the alveoli and small airways. In the setting of acute pulmonary oedema, this alveolar shadowing radiates out from the hilar areas – where there is relatively more interstitial tissue – in a 'bat's wing' pattern. As pulmonary oedema progresses this shadowing becomes more generalised.
Fluid also leaks into the pleural spaces, causing pleural effusions.
Dense airspace shadowing is due to alveolar oedema caused by fluid filling the alveoli and small airways
In the acute setting this airspace shadowing radiates from the hilar regions in a 'bat's wing' distribution and then becomes more generalised
Heart chamber enlargement
If the heart is enlarged it is sometimes possible to determine which chamber is enlarged. For example, signs of left atrial enlargement include a double right heart border, bulging of the left heart border, and splaying of the carina to greater than 90 degrees.
The left and right heart borders are marked (arrows)
Extra right heart border – formed by the edge of the enlarged left atrium (highlighted area)
Slight bulge in the left heart border (asterisk) due to enlargement of the left atrial appendage
Splaying of the carina to greater than 90 degrees – the carina lies directly above the left atrium
Clinical information
History of rheumatic heart disease and cardiac surgery – note the metallic aortic and mitral heart valve replacements (arrowhead)
Diagnosis
Cardiomegaly with left atrial enlargement due to chronic mixed mitral valve disease
Abnormal heart contours
The heart contours may be abnormal due to cardiac abnormalities, such as a left ventricular aneurysm, or pericardial abnormalities such as a pericardial effusion.
Left ventricular aneurysm - an uncommon complication of myocardial infarction
Obscured heart contours
The heart contours may be obscured due to disease of the adjacent lung. Just as right middle lobe consolidation can obscure the right heart border (right atrial edge), so consolidation of the lingula (an anterior segment of the left upper lobe) can obscure the left heart border (left ventricular edge).
