Treatment of pulmonary embolism

01Purpose and principlesWhat the treatment does and how it fits into care.

Anticoagulants prevent extension and recurrence; they do not instantly dissolve the embolus. Clinical recovery depends on endogenous fibrinolysis, cardiopulmonary reserve and supportive care.

Drug choice is inseparable from dosing sequence. Omitting the apixaban 7-day or rivaroxaban 21-day loading phase under-treats acute VTE; continuing it too long increases bleeding.

The three-month review is a new treatment decision, not an automatic stop date. Provoked versus unprovoked disease and bleeding risk guide the balance.

Inferior vena caval filters are not routine adjuncts. NICE reserves them mainly for a proximal DVT/PE when anticoagulation is contraindicated, or selected treatment failure after specialist review; establish removal plans early.

Key points

For confirmed proximal DVT or PE, NICE recommends therapeutic anticoagulation for at least 3 months.
For most haemodynamically stable adults, offer apixaban or rivaroxaban if suitable; each has a mandatory higher-dose initial phase.
Apixaban: 10 mg twice daily for 7 days, then 5 mg twice daily. Rivaroxaban: 15 mg twice daily for 21 days, then 20 mg once daily with food.
If apixaban and rivaroxaban are unsuitable, options include LMWH for at least 5 days followed by dabigatran or edoxaban, or LMWH/UFH overlapped with a vitamin K antagonist until the INR is therapeutic.
Before selection, check active bleeding, FBC/platelets, renal and liver function, pregnancy possibility, body weight, cancer site, antiphospholipid syndrome, interacting medicines and ability to adhere.
Use a validated low-risk tool plus clinical judgement when considering outpatient treatment; social support, bleeding risk, comorbidity, oxygen need and reliable follow-up also matter.
At 3 months review whether the PE was provoked, whether the provoking factor has resolved, recurrence risk, bleeding risk and patient preference.
Consider stopping after 3 months for a provoked PE with a resolved provoking factor and an uncomplicated course; consider continuing beyond 3 months after unprovoked PE when recurrence risk outweighs bleeding risk.
Active cancer usually requires 3–6 months of treatment followed by reassessment; tumour site, drug interactions and bleeding risk determine whether a DOAC or LMWH is preferred.
Triple-positive antiphospholipid syndrome is a vitamin K antagonist pathway, not routine DOAC treatment.

02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.

Stable PE suitable for anticoagulation

Normal perfusion, no shock or persistent hypotension, manageable oxygen requirement and no immediate reperfusion indication. Severity and outpatient suitability still require assessment.

Bleeding or anticoagulant contraindicationRed flag

Active major bleeding, recent high-risk surgery, severe thrombocytopenia, intracranial pathology or another major haemorrhage risk requires senior haematology/specialty discussion and sometimes a temporary IVC filter.

Cancer-associated thrombosis

Active cancer raises recurrence and bleeding risks; gastrointestinal/genitourinary lesions and anticancer-drug interactions can shift choice away from a DOAC.

Antiphospholipid syndrome

Known triple-positive APS or arterial thrombosis changes the long-term strategy toward LMWH bridging and a vitamin K antagonist rather than a DOAC.

Deterioration on treatmentRed flag

New hypotension, syncope, rising lactate, increasing oxygen need or chest pain demands immediate reassessment for high-risk PE, bleeding, recurrent embolism or an alternative diagnosis.

03Assessment before treatmentTests and checks that guide safe selection.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
FBC and platelet countFirst step
Why
Identify anaemia, thrombocytopenia and a baseline for bleeding/HIT surveillance.
Interpretation and limitations
A falling haemoglobin suggests occult bleeding; a major platelet fall after heparin exposure requires urgent HIT assessment.
02
Creatinine and calculated creatinine clearance
Why
Select and dose anticoagulation safely.
Interpretation and limitations
Use Cockcroft–Gault creatinine clearance where the product information specifies it; eGFR and CrCl are not interchangeable at extremes.
03
Liver function and coagulation screen
Why
Identify hepatic disease/coagulopathy and establish a baseline.
Interpretation and limitations
Significant hepatic disease with coagulopathy may make DOAC treatment unsuitable; PT/APTT do not quantify routine DOAC intensity.
04
Weight, pregnancy status and medicines reconciliation
Why
Detect groups needing an alternative agent, dose or specialist advice.
Interpretation and limitations
Record actual weight; examine strong CYP3A4/P-gp interactions, antiplatelets, NSAIDs and hormonal therapy.
05
Clinical severity and validated outpatient-risk assessment
Why
Choose inpatient versus ambulatory care.
Interpretation and limitations
A low-risk score is necessary but not sufficient: oxygen requirement, bleeding, renal failure, pain, pregnancy, adherence and home support can still mandate admission.
06
Cancer and provoking-factor review
Why
Determine duration, recurrence risk and need for further investigation.
Interpretation and limitations
Use history, examination and routine age-appropriate assessment; do not perform indiscriminate extensive occult-cancer imaging without symptoms or signs.
07
Three-month treatment review
Why
Reassess benefit versus bleeding and confirm the ongoing dose.
Interpretation and limitations
Resolved major transient factor favours stopping; unprovoked, persistent risk or recurrence favours extended therapy if bleeding risk is acceptable.

04Treatment approachPreparation, options, escalation and aftercare.

01First lineStable confirmed PE in most adultsFirst stepFirst lineConfirmed PE, haemodynamically stable, no major contraindication and apixaban/rivaroxaban suitable.

1Document baseline FBC, renal/liver function, coagulation, weight, bleeding risk, interactions and pregnancy status where relevant.
2Start either apixaban 10 mg twice daily for 7 days then 5 mg twice daily, or rivaroxaban 15 mg twice daily for 21 days then 20 mg once daily with food; prescribe the transition date explicitly.
3Decide admission versus outpatient care using a validated risk tool plus clinical/social criteria and provide anticoagulant counselling, written bleeding advice and contact details.
4Arrange a three-month review before the prescription expires; do not leave duration implicit.

02AlternativeDOAC loading strategy unsuitableAlternativeApixaban/rivaroxaban contraindicated, unsuitable or declined.

1Give therapeutic LMWH for at least 5 days, then start dabigatran or edoxaban if suitable; alternatively overlap LMWH/UFH with a vitamin K antagonist.
2For a vitamin K antagonist, continue parenteral anticoagulation for at least 5 days and until INR is at least 2.0 on 2 consecutive readings, then maintain the agreed INR target.
3Seek specialist input for severe renal impairment, extreme body weight, pregnancy, breastfeeding, significant liver disease, thrombocytopenia, APS or complex interactions.

03DurationDecision at three monthsCompletion of the initial 3 months of therapeutic anticoagulation.

1Confirm adherence, bleeding events, residual symptoms and whether the event was provoked by a now-resolved major transient factor.
2Provoked and uncomplicated with factor resolved: consider stopping. Unprovoked or persistent risk: discuss continued anticoagulation, recurrence risk, bleeding risk and preference.
3If continuing, verify the licensed extended-treatment dose and review at least annually or sooner when renal function, weight, cancer treatment or bleeding risk changes.

04Cancer/APSHigh-complexity selectionActive cancer or known triple-positive antiphospholipid syndrome.

1Cancer: consider tumour site, bleeding risk, renal function and anticancer-drug interactions; agree DOAC versus LMWH with oncology/haematology and review at 3–6 months.
2Triple-positive APS: use LMWH initially and transition to a vitamin K antagonist under specialist guidance; avoid routine DOAC substitution.
3Recurrent VTE despite apparently therapeutic treatment: confirm adherence/dosing, investigate interactions and recurrence, and seek specialist advice rather than simply adding antiplatelet therapy.

05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.

NICE first-line oral option for most stable confirmed PE when suitable.

Apixaban

10 mg orally twice daily for 7 days, then 5 mg twice daily; if extended prevention is chosen after 6 months, the licensed prevention dose is 2.5 mg twice daily.

Active bleeding, significant hepatic coagulopathy, interacting strong CYP3A4/P-gp drugs and pregnancy. Check current SmPC for renal and peri-procedural advice; the AF dose-reduction rule must not be copied into acute VTE treatment.

NICE first-line oral option for most stable confirmed PE when suitable.

Rivaroxaban

15 mg orally twice daily with food for 21 days, then 20 mg once daily with food; after at least 6 months, 10 mg once daily is licensed for extended prevention, with 20 mg considered when recurrence risk is high.

Active bleeding, significant liver disease/coagulopathy, renal impairment and interacting drugs. The 15 mg and 20 mg doses must be taken with food; document the day-22 switch.

Initial/alternative therapy, including bridging or situations where an oral agent is unsuitable.

Enoxaparin

For symptomatic PE, 1 mg/kg subcutaneously every 12 hours is a commonly licensed treatment regimen; a once-daily regimen is reserved for selected uncomplicated lower-risk patients under the SmPC.

Renal impairment, HIT history, thrombocytopenia, extreme weight and neuraxial procedures. Use an agent-specific renal regimen and consider anti-Xa advice in complex patients.

Oral alternative when apixaban/rivaroxaban are unsuitable but a DOAC remains appropriate.

Dabigatran

150 mg orally twice daily only after at least 5 days of therapeutic parenteral anticoagulation; licensed reductions/avoidance depend on age, renal function and interacting medicines.

Do not start as a single-drug acute loading regimen. Check creatinine clearance, age, verapamil and bleeding risk against the current SmPC.

Option when DOACs are unsuitable and preferred for triple-positive APS.

Warfarin

Individualised loading with INR monitoring; overlap therapeutic LMWH/UFH for at least 5 days and until INR is at least 2.0 on 2 consecutive readings. Typical VTE target INR is 2.5 (range 2.0–3.0).

Major food/drug interactions, pregnancy teratogenicity and narrow therapeutic range. Never use a fixed maintenance dose without INR-led titration.

06Complications, monitoring and follow-upAdverse effects, response and longer-term review.

At initiation, document FBC, platelets, renal/liver function, weight, interactions, bleeding risk and exact high-dose-to-maintenance transition date.
Contact/review early to check adherence, bleeding, recurrent symptoms and that the dose transition occurred correctly.
Repeat FBC and renal/liver function according to clinical risk and at least during regular long-term review; monitor more often in frailty, renal change or intercurrent illness.
At 3 months, record the provoked/unprovoked classification, resolved or persistent risk factor, recurrence/bleeding balance and shared duration decision.
After PE, investigate persistent dyspnoea, exercise limitation, syncope or signs of pulmonary hypertension rather than attributing every symptom to deconditioning.
Provide written advice on missed doses, bleeding, procedures, pregnancy and when to seek urgent help; ensure all clinicians know the anticoagulant and last dose.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Acute VTE dosing is indication-specific

Apixaban dose reduction used in atrial fibrillation does not define acute PE dosing. Always select the product's VTE regimen.

Two DOACs are single-drug pathways

Apixaban and rivaroxaban include their own oral loading phase; dabigatran and edoxaban require preceding parenteral anticoagulation.

Outpatient does not mean low-governance

Ambulatory PE needs prompt drug supply, education, reliable contact, review and a route back if symptoms worsen.

The trigger matters more than residual clot

Duration decisions are usually based on recurrence and bleeding risk, not routine repeat CTPA to prove clot disappearance.

IVC filters solve a narrow problem

They do not treat the existing embolus and create thrombosis/retrieval risks; use only for a defined indication with an early removal strategy.

08Common pitfallsFrequent interpretation and management errors.

01
Prescribing the maintenance DOAC dose from day 1 and omitting the acute loading phase.
02
Using an atrial-fibrillation apixaban dose-reduction rule for acute VTE.
03
Calling a patient outpatient-suitable from a score without assessing oxygen, bleeding, renal function, adherence and support.
04
Stopping all provoked and continuing all unprovoked PE without an individual bleeding/recurrence discussion.
05
Using a DOAC routinely in triple-positive APS.
06
Ordering routine repeat CTPA to decide whether anticoagulation can stop.