Pulmonary embolism

Question 1

What is pulmonary embolism?

Answer 1

Occlusion of pulmonary vessels, most commonly by a thrombus that has travelled from another site.

Question 2

What is the aetiology of PE? (x7)

Answer 2

• Over 95% originate from DVT of lower limbs • Rarely from right atrium in AF • Other agents that can embolise include amniotic fluid embolus, air embolus, fat emboli, tumour emboli and mycotic emboli (fungal)

Question 3

What are the risk factors for PE? (x8)

Answer 3

Surgical patients, immobility, obesity, OCP (oral contraceptive pill), heart failure, malignancy, pregnancy, and post partum.

Question 4

What is the pathophysiology of pulmonary thromboembolism?

Answer 4

Thrombus formation from venous stasis, vessel wall damage, and hypercoagulability (Virchow’s triad).

Question 5

What are the types of pulmonary embolism?

Answer 5

Massive (SBP less than 90), and submassive (not hypotensive, but usually evidence right heart dysfunction or myocardial injury signs such as elevated troponin)

Question 6

What is saddle pulmonary embolism?

Answer 6

Embolism becomes lodged in bifurcation of artery.

Question 7

What is the effect of PE on the heart?

Answer 7

Embolism increases pulmonary vascular resistance which leads to right ventricular distension and eventually decreased RV output. This leads to decreased LV preload leading to hypotension and shock.

Question 8

What is the epidemiology of PE: Proportion of DVT population?

Answer 8

Occur in 10-20% of those with confirmed proximal DVT.

Question 9

!!! What are the symptoms of PE: Small? Moderate? Large? Proximal? Multiple small recurrent?

Answer 9

• Depends on size and site • SMALL: may be asymptomatic • MODERATE: sudden onset dyspnoea, cough, haemoptysis, pleuritic chest pain • LARGE or PROXIMAL: all of the above plus central pleuritic chest pain, shock, collapse, right heart failure, or sudden death. • MULTIPLE SMALL RECURRENT: symptoms of pulmonary hypertension

Question 10

!!! What are the signs of PE: Small? Moderate? Large? Proximal? Multiple small recurrent?

Answer 10

• SMALL: earliest sign if tachycardia or tachypnoea
• MODERATE: tachypnoea, TACHYCARDIA, pleural rub, low oxygen saturation despite oxygen saturation
• LARGE or PROXIMAL: shock, cyanosis, signs of right heart strain such as raised JVP, left parasternal heave and accentuated S2 heart sound
• MULTIPLE SMALL RECURRENT: signs of pulmonary hypertension and right heart failure

Question 11

What clinical probability assessments can be used for PE? (x2)

Answer 11

Well’s score and Revised Geneva score

Question 12

What is Well’s score? Interpretation?

Answer 12

Based on signs and risk factors. Higher than 4 indicates high probability of PE, while 4 or less indicates that PE is unlikely.

Question 13

What is the Revised Geneva score?

Answer 13

Based on signs and risk factors. 11 or higher indicates high probability, 4-10 intermediate probability and 3 or lower low probability of PE.

Question 14

What are the investigations for PE when low probability?

Answer 14

D-dimer blood test (fibrin degradation products). If negative, then PE can be ruled out.

Question 15

!!! What are the investigations for PE when high probability? But first?

Answer 15

• Start anticoagulation, then… • Spiral CT pulmonary angiogram: sensitive to medium/large emboli

Question 16

What other imaging methods are there for PE? (x4)

Answer 16

• Ventilation-perfusion (VQ) scan: administration of IV 99mTc macro-aggregated albumin and inhalation of 81 krypton gas. This identifies areas of ventilation and perfusion mismatch that would indicate infected lung
• Pulmonary angiography: gold standard but invasive
• Doppler USS of the lower limb: for venous thrombosis (should be performed when Well’s score predicts high risk)
• Echocardiogram: may show right heart strain

Question 17

How do you investigate PE if CTPA is contraindicated?

Answer 17

For example, contraindicated in pregnant women because of radiation, or in someone allergic to the contrast.

Instead, you can do a V:Q - ventilation:perfusion lung imaging.

Question 18

What may ECG show in PE? (x4)

Answer 18

Tachycardia, right axis deviation or RBBB. Classical SI, QIII, TIII pattern is relatively uncommon but highly indicative of right heart strain in PE (large S wave in QRS complex in lead I, large Q wave in lead III and inverted T wave in lead III).

Question 19

How is PE managed if haemodynamically stable? (x3)

Answer 19

• Oxygen
• Anticoagulation with subcutaneous heparin or LMWH, and then warfarin loading (INR 2-3) for a minimum of 3 months
• Analgesics for pain

Question 20

How is PE managed if haemodynamically unstable? (x5)

Answer 20

• Give oxygen • IV fluid resuscitation – treat hypotension and shock • Anticoagulation with subcutaneous heparin • Thrombolysis with tPA if cardiac arrest is imminent • Vasotive drug such as noradrenaline is anticoagulation and thrombolysis contraindicated

Question 21

What are surgical interventions for PE and their indications? (x2)

Answer 21

• Embolectomy when thrombolysis contraindicated
• IVC filters (aka Greenfield filter) for recurrent pulmonary emboli despite adequate anticoagulation or when anticoagulation is contraindicated

Question 22

What is primary prevention for PE? (x4)

Answer 22

Graduated pressure stockings (TEDs) and heparin prophylaxis in those at risk (e.g., undergoing surgery). Early mobilisation and adequate hydration post-surgery.

Question 23

What are the complications of PE? (x3)

Answer 23

Pulmonary infarction, pulmonary hypertension, right heart failure.

Question 24

What is the prognosis of PE?

Answer 24

30% untreated mortality, 8% with treatment due to recurrent emboli or underlying disease.

Question 25

How is DVT investigated?

Answer 25

Well’s score for DVT is calculated, and low probability (less than 2) means D-dimer, and high probability (more than or equal to 2) means proceed to Doppler scan.

Question 26

What is meant by warfarin loading in PE management, and how long are patients on warfarin? When is LMWH stopped?

Answer 26

Once the INR has stabilized, usually between a therapeutic range of 2–3, the low molecular weight heparin may be stopped and the patient is to continue on warfarin for a minimum of three months. If this is a first presentation of pulmonary embolism, treatment usually ranges from three to SIX months. If there is a recurrent history of pulmonary embolism, the patient will usually stay on warfarin for life. Patients who have pulmonary emboli secondary to a malignant process (e.g. ovarian carcinoma, bronchogenic carcinoma) will usually be on life-long treatment dose low molecular weight heparin as studies have shown improved anti-coagulation when compared to warfarin.