The order of operations
The single most examined idea: assign a pretest probability before ordering anything.
- Wells score (or Geneva) to stratify
- Low probability → apply PERC. If all eight criteria are negative, the probability is low enough that no testing is needed
- Low or moderate probability → D-dimer. Negative ends the work-up; positive proceeds to imaging
- High probability → go straight to CT pulmonary angiography. A negative D-dimer does not exclude PE in a high-probability patient
D-dimer is a rule-out test only. It rises in infection, malignancy, pregnancy, surgery, trauma and old age, so a positive result in an elderly inpatient tells you almost nothing. Age-adjusted thresholds (age × 10 µg/L above 50) reduce unnecessary imaging.
Wells criteria in brief
Clinical signs of DVT (3), PE the most likely diagnosis (3), heart rate > 100 (1.5), immobilisation or surgery in 4 weeks (1.5), previous DVT/PE (1.5), haemoptysis (1), malignancy (1).
Imaging
- CTPA is the test of choice
- V/Q scan where CT is contraindicated: renal impairment, contrast allergy, or pregnancy — where it delivers less breast radiation, though more to the fetus
- Bedside echocardiography in the unstable patient, looking for right ventricular strain when there is no time to move the patient
Risk stratification drives treatment
| Category | Features | Treatment |
|---|---|---|
| Massive (high risk) | Sustained hypotension, shock, arrest | Thrombolysis, or embolectomy if lysis is contraindicated |
| Submassive (intermediate) | Normotensive with RV strain on imaging or raised troponin/BNP | Anticoagulation with close monitoring; consider lysis if deteriorating |
| Low risk | Normotensive, no RV strain | Anticoagulation; consider outpatient management using the PESI score |
Anticoagulation
- DOACs are first-line for most: apixaban or rivaroxaban can be started without parenteral lead-in; dabigatran and edoxaban need 5 days of heparin first
- LMWH in pregnancy and in active cancer (though DOACs are increasingly used in cancer, with caution in gastrointestinal and genitourinary tumours)
- Warfarin for antiphospholipid syndrome, severe renal impairment and mechanical valves
- Duration: 3 months for a provoked event with a transient risk factor; indefinite for unprovoked events with low bleeding risk, recurrent events, or ongoing cancer
Thrombophilia testing
Rarely changes management and is best avoided in the acute setting — anticoagulation and acute thrombosis both distort the results. Consider it for unprovoked events in the young, unusual sites, recurrent pregnancy loss, or a strong family history.