What are the key clinical features and risk factors to consider when assessing a patient for pulmonary embolism?

When assessing a patient for pulmonary embolism (PE), key clinical features to consider include symptoms such as chest pain, shortness of breath, and haemoptysis (coughing up blood). Signs may include tachycardia (heart rate greater than 100 beats per minute) and clinical features of deep vein thrombosis (DVT), such as leg swelling and pain on palpation of deep veins. Additionally, haemodynamic instability signs such as cardiac arrest, obstructive shock (systolic blood pressure <90 mmHg despite adequate filling), or persistent hypotension are critical indicators requiring immediate admission.

Risk factors to consider include recent immobilization for more than 3 days or surgery within the previous 4 weeks, previous history of DVT or PE, active cancer (receiving treatment, treated in the last 6 months, or palliative), and pregnancy or recent childbirth within the past 6 weeks. An alternative diagnosis being less likely than PE also increases the clinical suspicion.

These features are incorporated into the two-level PE Wells score, where a score above 4 points indicates PE is likely, and 4 or less suggests PE is unlikely. The Wells score assigns points for clinical signs of DVT (3 points), alternative diagnosis less likely than PE (3 points), heart rate >100 bpm (1.5 points), immobilization or surgery (1.5 points), previous DVT/PE (1.5 points), haemoptysis (1 point), and cancer (1 point).