Lecture 20 - Diagnosis And Management Of PE Flashcards Preview

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Pulmonary embolism

- DVT and PE are manifestations of the same condition: VTE
- may be lethal acutely, or lead to chronic disability
- incidence 100-200 per 100.000/yr
- symptoms are not specific, some patients detected without symptoms
- PE is the cause of death in 5.2% of autopsy series of 6822 patients who died in a single hospital



- thrombus developing in veins of lower limbs or pelvis -> embolism to pulmonary arteries
- within the veins: Thrombus development - Virchow's triad. Local effects in calf/legs. Organisation of venous thrombus and risk of recurrent events
- Cardiopulmonary effects: acute effects of embolization: RV, shock. Chronic effects on pulmonary arterial tree


Virchow's triad

- Hypercoagulability (blood): cancers, inflammation (including surgery), thrombophilias, contraceptive pill, pregnancy
- Heamodynamics (Flow): immobility, orthopedic injury/surgery, pregnancy
- endothelial injury/dysfunction (Vessel): trauma, chronic venous disease


Acute effects with larger, central emboli

- increased pulmonary vascular resistance
- thin-walled RV has limited ability to acutely adapt: RV dilatation, reduced contractibility, tricuspid regurgitation
- reduced LV filling, reduced CO
- reduced RV coronary perfusion, RV ischaemia
- hypoxaemia from reduced CO, VQ mismatch, right to left shunting through foramen ovale


Acute effects: smaller, peripheral emboli

- pulmonary infarction: fever
- hemorrhage: haemoptysis
- pleural irritation/inflammation: pleuritic pain, pleural effusions


Chronic effects

- recurrent embolization
-> organisation and incomplete recenalization in pulmonary arterial tree
-> PHT
-> RV failure, cor pulmonale
-> Systemic embolization if there is a right to left shunt (paradoxical embolization)



- confirm diagnosis or exclude PE
- assess severity: shock or hypotension



- Resp: Dyspnea, pleuritic pain, haemoptysis
- DVT: limb swelling, pain
- Systemic: fever, syncope
- Risk factors: immobilisation, pregnancy, oral contraception, HRT, prior DVT/PE, chronic venous disease, cancer, family history



- vitals
- resp rub
- cardiac: PHT, RV failure
- CXR: effusion, atelectasis, other diagnosis
- blood gases: assessment, not to diagnose
- Other blood tests: creatinine, Hb


Assessing pre-test probability

- clinical features insufficient to diagnose PE, but are important to assess pre-test probability
- Clinical prediction rules: Well's or Geneva score, in combination with d-diner or other imaging


If low suspicion of PE: PE Rule Out criteria (PERC)

- no further testing required if all conditions are met
- pretest probability is


Simplified Well's criteria

- one point each for: Previous PE or DVT, HR>100bpm, surgery or immobilisation within the past 4 weeks, haemoptysis, active cancer, clinical signs of DVT, alternative diagnosis less likely than PE
- PE probability low: 0-1
- PE probability intermediate: 2-4
- PE probability high: >5



- a product of fibrinolysis (indicates clot formation)
- used if pre-test probability is low-intermediate
- only useful if d-diner test is negtive
- not specific, can be elevated with inflammation, cancer, pregnancy


Ruling out PE with D-diner

- a low/intermediate pretest pronbability + negative d diner EXCLUDES PE


CT pulmonary angiography

- sensitivity 83%, specificity 96%
- always use in context with pre-test probability: be cautious if discordance


- advantages
- disadvantages

- advantages: rapid, provide information relevant to alternative diagnosis

- disadvantages: risk of contrast-induced renal toxicity (higher with existing renal disease), risk of allergic reaction, radiation exposure


VQ scan

- ventilation scan: technetium-99m labelled aerosols or microparticles
- perfusion scan: iv injection of Tc-99m labelled macro-aggregated albumin
- VQ mismatch: no perfusion in areas of normal ventilation



- useful if CT contraindicated
- needs normal CXR
- results may be inconclusive
- exercise caution if result is discordant with pre-test probability


Pulmonary angiography

- used as the gold standard for many trials
- percutaneous catherization of pulmonary arterial tree, usually via femoral vein
- also requires radiological contrast
- consider if other tests are not conclusive
- not commonly used to diagnose PE, used to evaluate chronic thromboembolic disease


Venous ultrasound

- loot for proximal thrombi: 40-50% progress to PE, sufficient to warrant therapy for VTE
- does not detect pelvic thrombosis
- lack sensitivity
- use if: other testing inconclusive, contraindications to other tests: renal failure, pregnancy



- can be done at the bedside if patient is unstable
- look for RV dilatation/dysfunction, pHT
- not specific
- uses: assess severity, support presence of PE, look for other causes of shock: tamponade


Testing vs empiric treatment

- many tests can be done quickly
- if delays are anticipated with confirmatory testing, and suspicion for PE is high, consider empiric anticoagulant therapy



- supportive: O2, fluid resuscitation, inotropes, analgesia, monitoring ICU/HDU if unstable
- anticoagulant: heparin, warfarin, new oral anticoagulant
- with shock: thrombolysis


General considerations regarding anticoagulation

- facilitate usual mechanism for thrombus resolution (fibrinolysis) and recanalisation
- VTE can be fatal: anticoagulation prevents early death and recurrent symptomatic or fatal VTE
- risk of bleeding: can cause mortality or major morbidity


Prognosis from acute PE

- crude mortality 17% at 3 months
- risk factor: age, cancer, CCF, COPD, hypotension, low RR, RV hypokinesis


Unfractionated heparin

- given IV
- short half life: can be stopped quickly if needed, or reversed with protamine
- need anticoagulant monitoring: APTT
- risk of heparin induced thrombocytopenia
- preferred if massive or submassive PE



- given subcutaneously
- longer half life
- predictable dosing: dose based on weight
- caution with renal failure or marked obesity
- anti-coagulant monitoring available, but not needed routinely



- oral vit K antagonist
- longer OofA: start with heparin or LMWH
- require blood monitoring: INR, target 2-3
- can be reversed: FFP or vit K
- Diet, liver impairment or other drugs may affect with dosing
- teratogenicity: contraindicated in pregnancy



- rivaroxaban or apixaban approved for PE in australia:
- can be used as initial treatment or following heparin/ LMWH
- oral, long half life
- fixed dose. Causation with renal impairment
- no practical means to reverse effects, but phase 3 trials suggest lower risk of major bleeding



- tissue plasminogen activator
- consider thrombolysis in setting of shock or hypotension: these patients have a high risk of in-hospital deaths (massive PE)
- submassive PE: RV dysfunction on echo/CT but without shock or hypotension
- thrombolysis reduced risk of early haemodynamic compromise but with increased risk of major bleeding and no overall effect on mortality


Other therapies

- IVC filter placement if anticoagulation is contraindicated
- if hemodynamic compromise develops: surgical embolectomy, percutaneous catheter treatment, fragment or remove thrombus
- VA-ECMO: early experience -> providing cardio-respiratory support while awaiting effect of anticoagulation



- PE + shock: IV heparin, consider thrombolysis
- otherwise: LMWH/heparin -> warfarin
- LMWH/heparin -> NOAC
- start with NOAC


Duration of anticoagulant therapy

- provoked PE: generally 3-6 months anticoagulation
- unprovoked PE: first event: 6 months, consider continuing indefinitely. If second or recurrent event: recommend indefinite anticoagulant
- VTE recurrence risk is low while on anticoagulation
- recurrence rate is higher if PE was unprovoked
- consider bleeding risk vs risks of VTE


Aspirin in unprovoked PE

- after ceasing standard anticoagulant, aspirin reduces risk of recurrence
- bleeding risk lower


Late complication of PE

- recurrent VTE
- Chronic thromboembolic pulmonary hypertension (CTEPH)
- 0.1-9% incidence within 2 years
- dyspnea, progression to RV dysfunction
- thrombi -> pulmonary vascular
- diagnosed by VQ, CT, confirmed by pulmonary angiography


CTEPH management

- anticoagulant
- Surgery: pulmonary endarterectomy
- riociguat: oral stimulator of guanylate cyclase. Improves exercise capacity and pulmonary haemodynamics