17th January 2024

Differential diagnoses

Pulmonary embolism is a life-threatening diagnosis which is important not to miss. There is a broad differential for both chest pain and shortness of breath, and symptoms and signs can be shared with a multitude of other conditions. We will focus mainly on other diagnoses; it would be important to differentiate from PE due to comparable clinical urgency.

Acute coronary syndrome

Acute coronary syndrome is a term that encompasses patients presenting with unstable angina, non-ST-elevation and ST-elevation myocardial infarction. Classical symptoms include chest pain or tightness, shortness of breath, diaphoresis, nausea, vomiting and dizziness. PE shares a lot of similar features, although generally has a greater association with hypoxia and tachycardia, and the nature of the chest pain is classically described as more pleuritic. ECG would be a mainstay of differentiating between the two diagnoses – if this raised significant clinical suspicion of a myocardial infarction, the patient would need to be taken for urgent cardiac catheterisation. Blood tests can help guide diagnosis, but caution should be used when relying on biochemical markers alone, as troponin and d-dimer can be deceptively raised in both conditions.

Pneumothorax

Primary, secondary and tension pneumothoraces can all present with sudden onset pleuritic chest pain and shortness of breath. A past medical history of pre-existing airways disease may point towards a diagnosis of secondary pneumothorax, but overall, few features in the history alone can differentiate between pneumothorax and pulmonary embolism. On examination, the most notable feature would be reduced breath sounds and hyperresonance to percussion on the side of a pneumothorax, as well as tracheal deviation in the case of a tension pneumothorax. Comparably, air entry should sound normal in a PE. In many cases, definitive treatment will involve chest drain insertion, so early access to chest radiograph imaging for diagnosis is essential.

Pericarditis

Pericarditis classically presents with chest pain relieved on leaning forwards, shortness of breath and sometimes dizziness. Similarly to a PE, it can present in a young population in the absence of a clear trigger. Features that raise suspicion of pericarditis would include a clear history of recent viral infection, co-existing inflammatory disorders such as rheumatoid arthritis or a fever at presentation itself. ECG features also include widespread saddle-shaped ST-elevation. It is important to keep in the differential as the life-threatening complication of pericardial effusion can occur.

Aortic dissection

Aortic dissection is a medical emergency that causes sudden onset, severe, tearing chest pain that often radiates to the back. Classical features on examination include a wide pulse pressure and radial-radial or radial-femoral delay. Definitive diagnosis can only be made by CT aortogram imaging, so a high index of suspicion must be maintained when reviewing any patient presenting with chest pain, particularly patients with a past medical history of aortic aneurysm or hypertension.

Other disorders

As shortness of breath, pleuritic chest pain, cough and haemoptysis are common presentations associated with a range of clinical conditions, the differential must be kept broad and guided by findings on history and examination. Any respiratory disorder such as pneumonia, lung cancer or pleural effusion could potentially be a mimic of a PE. Equally, musculoskeletal causes of chest pain, such as costochondritis or Tietze’s syndrome, can commonly produce pain of a similar nature, but these must remain a diagnosis of exclusion (4).