Pulmonary Embolism

Question 1

What is a pulmonary embolism?

Answer 1

When a blood clot in the pulmonary arterial vasculature develops, usually from an underlying deep vein thrombosis (DVT) of the lower limbs.

Question 2

How is a pulmonary embolism formed?

Answer 2

(DVT) that developed in the legs and travelled (embolised) through the venous system and the right side of the heart to the pulmonary arteries in the lungs.

Once they are in the pulmonary arteries they block the blood flow to the lung tissue and create strain on the right side of the heart.

Question 3

What are DVTs and PEs collectively known as?

Answer 3

DVTs and PEs are collectively known as venous thromboembolism (VTE).

Question 4

Risk factors

Answer 4

Immobility
Recent surgery
Long haul flights
Pregnancy
Hormone therapy with oestrogen
Malignancy
Polycythaemia
Systemic lupus erythematosus
Thrombophilia

Question 5

Signs and symptoms

Answer 5

Shortness of breath
Cough with or without blood (haemoptysis)
Pleuritic chest pain
Hypoxia
Tachycardia
Raised respiratory rate
Low grade fever
Haemodynamic instability causing hypotension

A massive pulmonary embolism may present with the above and syncope/shock.

A massive pulmonary embolism may present with hypotension, cyanosis, and signs of right heart strain (such as a raised JVP, parasternal heave, and loud P2).

It is important to look for signs of a concomitant deep vein thrombosis (a unilaterally swollen, tender calf).

Question 6

ECG changes

Answer 6

Normal or sinus tachycardia.

In a massive PE there may be evidence of right-heart strain (with P pulmonale, right axis deviation, right bundle branch block, and non-specific ST/T wave changes).

The classic S1Q3T3 (deep S waves in lead I, pathological Q waves in lead III, and inverted T waves in lead III) is relatively uncommon (<20% of patients).

Question 7

Prophylaxis

Answer 7

Every patient admitted to hospital should be assessed for their risk of venous thromboembolism (VTE).

If they at increased risk of VTE they should receive prophylaxis with a low molecular weight heparin such as enoxaparin unless contraindicated.

Contraindications include active bleeding or existing anticoagulation with warfarin or a NOAC.

Anti-embolic compression stockings are also used unless contraindicated.

The main contraindication for compression stockings is significant peripheral arterial disease.

Question 8

ABG in PE

Answer 8

Normal or show a type 1 respiratory failure (hypoxia without hypercapnia) and/or a respiratory alkalosis (due to hyperventilation secondary to hypoxia).

Remember the baseline tests such as FBC (the patient may be anaemic if the PE has caused haemoptysis), CRP may be raised, U&E (to assess renal function before CTPA), clotting function (important if the patient is to be started on LMWH/Warfarin).

Question 9

Base line bloods in PE

Answer 9

FBC (the patient may be anaemic if the PE has caused haemoptysis)

CRP may be raised

U&E (to assess renal function before CTPA)

Clotting function (important if the patient is to be started on LMWH/Warfarin).

Question 10

D-dimer bloods in PE

Answer 10

Highly non-specific but has a 95% negative predictive value i.e. it is useful in ruling out a PE if negative).

Question 11

What is the Well’s score used for?

Answer 11

Risk of a patient presenting with symptoms actually having a DVT or pulmonary embolism.

Question 12

Why would 3 points be appointed in Well’s score?

Answer 12

Clinical signs and symptoms of a deep vein thrombosis (DVT)
If no alternative diagnosis is more likely than a PE

Question 13

Why would 1.5 points be appointed in Well’s score?

Answer 13

Tachycardia (heart rate >100 beats/minute)

If the patient has been immobile for more than 3 days or has had major surgery within the last month

If the patient has had a previous PE or DVT

Question 14

Why would 1 point be appointed in Well’s score?

Answer 14

If the patient presents with haemoptysis

If there is an active malignancy

Question 15

What should be done if the Well’s score is 4 or less?

Answer 15

If the Well’s score is 4 or less the D-dimer should be measured.

A low D-dimer excludes a PE. A raised D-dimer is an indication for diagnostic imaging (by CTPA or V/Q scan).

Question 16

What should be done if the Well’s score is more than 4?

Answer 16

If the Well’s score is more than 4 further diagnostic imaging is required. Low-molecular weight heparin is typically administered in the interim if the clinical suspicion of a PE is high (and should certainly be administered if there is delay in performing the CTPA).

Question 17

Medical management

Answer 17

The initial recommended treatment is apixaban or rivaroxaban.

Low molecular weight heparin (LMWH) is an alternative where these are not suitable, or in antiphospholipid syndrome.

It should be started immediately before confirming the diagnosis in patients where DVT or PE is suspected and there is a delay in getting the scan.

Examples are enoxaparin and dalteparin.

Question 18

How long should patients be on anticoagulants?

Answer 18

3 months if there is an obvious reversible cause (then review)

Beyond 3 months if the cause is unclear, there is recurrent VTE or there is an irreversible underlying cause such as thrombophilia.

6 months in active cancer (then review)

Question 19

What is INR?

Answer 19

A diagnostic test relating to how long it takes for blood to clot

If INR is high, it means blood does not clot quickly enough putting patient at risk of bleeding

Question 20

What are options for long term anticoagulants?

Answer 20

The options for long term anticoagulation in VTE are warfarin, a DOAC or LMWH.

Question 21

What should be done when switching to warfarin?

Answer 21

The target INR for warfarin is 2-3. When switching to warfarin continue LMWH for 5 days or the INR is 2-3 for 24 hours on warfarin (whichever is longer).

Question 22

What is the recurrence of a VTE in a patient already on warfarin?

Answer 22

Recurrence of a VTE in a patient already on warfarin requires an increase in the target INR (to 3-4).

Question 23

What are DOAC’s?

Answer 23

Direct oral anti coagulants

directly inhibit specific proteins within the coagulation cascade

Question 24

How does Warfarin work?

Answer 24

Warfarin competitively inhibits the vitamin K epoxide reductase complex 1 (VKORC1), an essential enzyme for activating the vitamin K available in the body.

Vitamin K is an essential cofactor for the synthesis of all of these vitamin K-dependent clotting factors.

Question 25

What is Warfarin contraindicated in?

Question 26

Acute management of PE

Answer 26

In the emergency department the patient should be assessed using the DR ABCDE approach:

Airway: likely to be patent.
Breathing: the patient may be tachypnoeic and hypoxic. Oxygen should be administered.
Circulation: the patient may be tachycardic. Signs of right heart strain are suggestive of a sub-massive PE. Hypotension is suggestive of a massive PE. Consider intravenous fluids if the systolic blood pressure is <90 mmHg.
Disability: likely to be unremarkable.
Exposure: the patient may have a low grade pyrexia. It is important to check for signs of a deep vein thrombosis (DVT). Consider analgesia at this stage if required.
Thrombolysis (an intravenous bolus of Alteplase) is indicated in a massive PE (features of haemodynamic instability). There is debate over whether it should be administered in a sub-massive PE.

Question 27

Interventional PE management

Answer 27

Embolectomy may be considered in patients with a massive PE when thrombolysis is contraindicated.

An inferior vena cava filter may be considered in patients with recurrent DVTs on Warfarin or patients in which anticoagulation is contraindicated.

Question 28

What is thrombolysis and when is it used?

Answer 28

Thrombolysis involves injecting a fibrinolytic medication (they break down fibrin) that rapidly dissolves clots.

There is a significant risk of bleeding which can make it dangerous.

It is only used in patients with a massive PE where the benefits outweigh the risks.

Some examples of thrombolytic agents are streptokinase, alteplase and tenecteplase.

Question 29

What scans are used to diagnose a PE?

Answer 29

CT pulmonary angiogram (CTPA): this is the diagnostic test of choice for a PE and will show a filling defect in the pulmonary vasculature. Note that a V/Q scan is preferred if the patient has renal impairment, contrast allergy or is pregnant.

Question 30

What will a bedside echocadiogram show in PE?

Answer 30

Used if the patient is thought to have a massive PE (signs of right heart strain/hypotension), in order to assess suitability for thrombolysis.