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.

Signs of heart failure

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Signs of heart failure

  • Cardiomegaly CTR = 18/30 (>50%)
  • 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 (Kerley B lines)

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Septal lines (Kerley B lines)

  • Costophrenic angle (detail of above image)
  • Horizontal lines reaching the lung edge

Diagnosis

  • 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.

Alveolar oedema - airspace shadowing

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Alveolar oedema - airspace shadowing

  • 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.

Left atrial enlargement

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Left atrial enlargement

  • 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

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Left ventricular aneurysm

  • AP erect chest X-ray
  • Bulging of the left heart border
  • Circular rim of calcification (arrowheads)

Clinical information

  • Previous myocardial infarction

Diagnosis

  • 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).

Consolidation of the lingula

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Consolidation of the lingula

  • Poorly defined left heart border due to consolidation in the adjacent lingula

Clinical information

  • Productive cough
  • Raised white cell count

Diagnosis

  • Lobar pneumonia