If there is cardiomegaly then look for other signs of heart failure
It may be possible to determine which chamber is enlarged
An obscured heart border may indicate disease of the adjacent lung
Cardiomegaly and heart failure
The heart size should be assessed on every chest radiograph. The heart is enlarged if the cardiothoracic ratio (CTR) is greater than 50% on a PA view. If the heart is enlarged, check for other signs of heart failure such as pulmonary oedema, septal lines (or Kerley B lines), and pleural effusions.
Upper zone vessel enlargement (1) – a sign of pulmonary venous hypertension
Pulmonary oedema (2) – bilateral increased lung markings (classically peri-hilar and shaped like bats wings – more widespread in this case)
Septal (Kerley B) lines (3) – See next picture
Pleural effusions (4)
Worsening exercise tolerance
Chronic uncontrolled hypertension
Rapid onset of shortness of breath
Left ventricular failure with pulmonary oedema
Septal (Kerley B) lines
Septal lines – also known as Kerley B lines – are due to 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.
Conditions which limit lymphatic flow within the lungs – such as lymphangitis carcinomatosa or sarcoidosis – may also cause septal lines.
Septal lines are a specific sign of interstitial oedema in the context of suspected heart failure
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
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.