Pulmonary Embolism (PE) Flashcards
what is a pulmonary embolism (PE)?
the luminal obstruction of one or more pulmonary arteries by an embolised venous thrombus, but can also be due to an embolised solid, liquid, or gas
what is the difference between a thrombus and an embolism?
- a thrombus refers to a blood clot that is formed within a blood vessel and remains in its place of origin
- embolism describes the process where the bloodstream carries a detached intravascular solid, liquid, or gaseous mass from its origin to a distant site
what is the aetiology of a PE?
- DVT (e.g. calf)
- fat embolism
- air embolism
- amniotic fluid embolism
- septic emboli
- de novo thrombosis
what are the pathological consequences of a PE?
- ventilation/perfusion mismatch → impaired gaseous exchange → hypoxaemia (type 1 respiratory failure) and tachypnoea
- pulmonary arterial hypertension (e.g. due to increased pulmonary vasculature resistance) → right ventricular overload +/- dysfunction
- pleural and lung inflammation and infarction → pleuritic chest pain +/- haemoptysis
what is the virchow’s triad for VTE?
- venous stasis: prolonged immobilisation (e.g. bed rest >5 days, major surgery within the last 2 months, recent trauma or fracture, paralysis of the lower limb, long-haul flights), venous insufficiency of the lower limb
- hypercoagulable state: active malignancy, pregnancy and postnatal period, thrombophilia (e.g. antiphospholipid syndrome), use of combined hormonal contraception and oral hormone replacement therapy
- endothelial injury: trauma, surgery, venous harvest, cigarette smoking, obesity
what are the symptoms of a PE?
- dyspnoea
- tachypnoea
- pleuritic chest pain
- features of concurrent DVT (e.g. unilateral red, painful swollen leg)
- haemoptysis
what are the findings on examination of a PE?
- tachycardia
- tachypnoea
- hypoxia
- low-grade fever
- pleural rub
- gallop rhythm (e.g. a wide split-second heart sound and tricuspid regurgitant murmur)
what are the features of a massive PE?
- haemodynamic instability (e.g. hypotension, cardiogenic shock)
- presyncope/syncope
- elevated JVP
what are the investigations for a PE?
- respiratory examination
- cardiovascular examination
- 12-lead ECG
- D-dimer
- FBC
- U&Es
- LFTs
- cardiac biomarkers (e.g. troponin, BNP)
- coagulation
- CXR
- CTPA
- ? V/Q planar scan/SPECT
- ? echocardiogram
what may an ECG show in a PE?
- sinus tachycardia
- right ventricular strain pattern (e.g. T wave inversion in anterior leads (V1-V4) +/- inferior leads (II, III, aVF))
- RBBB
- RAD
- the classic ‘S1Q3T3’ ECG change is only seen in <20% patients (e.g. large S wave in lead I, large Q wave in lead III, and inverted T wave in lead III)
D-dimer test has a high sensitivity but low specificity for VTE. which conditions can result in an elevated D-dimer in the absence of VTE?
- pregnancy
- malignancy
- liver disease
- severe infection/inflammatory disease
- DIC
- recent trauma/surgery/hospitalised patients
what are the possible findings of a CXR in a PE?
- most patients with PE have a normal CXR
- wedge-shaped pulmonary infarction
- atelectasis
- pleural effusion
- raised hemidiaphragm
what is the alternative to CTPA in the diagnosis of PE?
ventilation-perfusion (V/Q) planar scan or SPECT
- severe renal impairment (eGFR < 30 mL/min/1.73m2)
- allergic to contrast media
- at high risk from irradiation (e.g. pregnancy)
which investigation is recommended to aid the diagnosis of a PE in hemodynamically unstable patients?
echocardiography may show signs of right ventricular dysfunction that is suggestive of PE, including:
- abnormal right ventricular ejection pattern (e.g. 60/60 sign)
- mcconnel sign (e.g. reduced right ventricular free wall contractility compared with the apex)
- right ventricular dilation and hypokinesis
what is the management of a PE (e.g. wells ≤4)?
- D-dimer
- if the D-dimer test result cannot be obtained within 4 hours, start interim therapeutic anticoagulation
- if the D-dimer test is positive: offer immediate CTPA and give interim therapeutic anticoagulation if there is a delay
- if the D-dimer test is negative: stop any interim therapeutic anticoagulation
what is the management of a confirmed PE with haemodynamic instability?
offer continuous UFH infusion, and consider thrombolytic therapy:
- IV tissue plasminogen activator (tPA) (e.g. alteplase)
- catheter-directed thrombolysis
- open pulmonary embolectomy
when can outpatient treatment be considered for low-risk PE according to NICE?
- outpatient treatment for low-risk PE can be considered if a validated risk stratification tool determines suitability (e.g. PESI)
- haemodynamic stability is a requirement
what is the management of a confirmed PE without haemodynamic instability?
- 1st-line: apixaban/rivaroxaban
- 2nd-line: LMWH + dabigatran/edoxaban OR LMWH + warfarin
how does the choice of anticoagulants vary in specific patient populations?
- pregnant: LMWH only
- active cancer: DOAC preferred over LMWH
- severe renal impairment (eGFR < 15 mL/min/1.73m2): UFH or dose-adjusted LMWH
- APS: initial LMWH and warfarin followed by warfarin monotherapy
- all forms of anticoagulation contraindicated: inferior vena cava (IVC) filter
what are NICE recommendations for anticoagulation duration in VTE patients?
- minimum of 3 months of anticoagulation for all patients
- further anticoagulation depends on the risk of: VTE recurrence + bleeding (e.g. ORBIT score)
what is the rule of thumb for anticoagulation duration based on VTE type?
- provoked: 3 months
- unprovoked: 6 months
- active cancer: 3-6 months
what is the difference between a provoked and unprovoked PE?
- provoked: associated with a recent (e.g. within 3 months) transient major risk factor
- unprovoked: no recent (e.g. within 3 months) transient major risk factor + not using hormonal therapy
what are the short-term complications of a PE?
- sudden cardiac arrest/death (e.g. due to ventricular collapse due to massive embolism and occlusion of the pulmonary vasculature)
- pulmonary infarction
- right ventricular infarction (e.g. due to pulmonary hypertension and haemodynamic overload)
- atelectasis
- exudative pleural effusion
what are the long-term complications of a PE?
- increased risk of recurrence
- chronic thromboembolic pulmonary hypertension (CTEPH)
what is chronic thromboembolic pulmonary hypertension (CTEPH)?
occurs where fibrotic tissue replaces residual emboli causing chronic obstruction of the pulmonary vasculature, and hence pulmonary hypertension
