A chest X-ray (CXR) is a fundamental diagnostic tool for evaluating patients with suspected congestive heart failure (CHF).
Whilst clinical assessment is vital, the CXR provides objective evidence of pulmonary venous congestion and fluid overload.
This is an example of acute pulmonary oedema as a sign of heart failure.
ABCDE Mnemonic for Heart Failure
To systematically interpret a chest X-ray for signs of heart failure, doctors use the ABCDE mnemonic. This ensures no subtle signs of pulmonary oedema are missed.
| Letter | Finding | Clinical Description |
| A | Alveolar (Pulmonary) Oedema | Often seen as “bat-wing” or “butterfly” opacities spreading from the hilum. |
| B | Kerley B Lines | Short (1–2 cm) horizontal lines at the lung bases, indicating thickened interlobular septa. |
| C | Cardiomegaly | An enlarged heart where the Cardiothoracic Ratio (CTR) is >50% on a PA film. |
| D | Diversion | Also known as Cephalisation; the dilation of upper lobe pulmonary veins. |
| E | Effusions | Pleural effusions, typically bilateral or right-sided, seen as blunting of the costophrenic angles. |
1. Alveolar (Pulmonary) Oedema: Bat-Wing Opacities
This refers to bilateral perihilar opacification. It is a classic sign of acute alveolar edema, where fluid has leaked into the air sacs (alveoli) rather than just the interstitial space.
2. Kerley B Lines
These are thin, horizontal lines perpendicular to the pleural surface. They represent fluid accumulation in the interlobular septa and are most prominent in the lower posterior lung fields.
3. Cardiomegaly and the Cardiothoracic Ratio (CTR)
The heart is considered enlarged if its diameter is more than half the internal diameter of the rib cage.
Note: This measurement is only reliable on a PA (Posteroanterior) view. On an AP (Anteroposterior) view, the heart can appear artificially enlarged due to magnification.
4. Pulmonary Venous Congestion (Cephalisation)
In a healthy, upright patient, gravity ensures lower lobe vessels are larger than upper lobe vessels. In heart failure, increased left atrial pressure causes the upper lobe vessels to dilate, a phenomenon known as “cephalization” or “venous diversion.”
5. Effusions
These may be unilateral or bilateral. If drained they will be a transudate.
Surgical Clues: Always inspect the mediastinum for sternal wires or prosthetic valves. These indicate previous cardiac surgery, such as a Coronary Artery Bypass Graft (CABG) or valve replacement, pointing to a chronic underlying aetiology.
Acute vs. Chronic Presentation:
Acute Heart Failure: Often presents with rapid-onset pulmonary edema and “bat-wing” signs, sometimes with a normal heart size if the insult (like a massive MI) was sudden.
Chronic Heart Failure: More likely to demonstrate significant cardiomegaly and pleural effusions as the heart has had time to remodel and dilate.
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