Pulmonary embolism

Question 1

PE: definition

Answer 1

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

Question 2

PE: epidemiology

Answer 2

2300 people died as a result of a pulmonary embolism in the UK in 2012, representing 2% of all deaths from lung diseases.

Question 3

PE: symptoms

Answer 3

Sudden-onset shortness of breath
pleuritic chest pain
haemoptysis

+/- syncope/shock (if massive PE)

A small PE may be asymptomatic.

Question 4

PE: signs

Answer 4

tachypnoea
tachycardia (may be only present)
hypoxia
+/- low fever
If massive PE –> shock (low BP, cyanosis, RH strain e.g. raised JVP, parasternal heave, loud P2)

Look for red and swollen calf

Question 5

What is the relative relative frequency of symptoms in PE

Answer 5

Tachypnea (respiratory rate >16/min) - 96%
Crackles - 58%
Tachycardia (heart rate >100/min) - 44%
Fever (temperature >37.8°C) - 43%

Question 6

PE: ECG

Answer 6

ECG - sinus tachy
S1Q3T3 (large S wave in lead I, a large Q wave in lead III and an inverted T wave in lead III) - only 20% of patients
right heart strain (RBBB, RAD, p pulmonale)

Question 7

PE: blood tests

Answer 7

FBC (anaemia)
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)

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

D-dimer (this is highly non-specific but has a 95% negative predictive value i.e. it is useful in ruling out a PE if negative).

Question 8

PE: imaging

Answer 8

Chest x-ray: Typically normal, helpful in ruling out other pathology

• May see Fleischner sign (an enlarged pulmonary artery), Hampton’s hump (a peripheral wedge shaped opacity), and Westermark’s sign (regional oligaemia).

GOLD STANDARD: CT pulmonary angiogram (CTPA): shows filling defect in the pulmonary vasculature.

• V/Q scan is preferred if the patient has renal impairment, contrast allergy or is pregnant -

Lower limb Duplex: helpful if a DVT is thought to be the cause of the PE (note this investigation is first-line - before a CTPA - in pregnancy).

Bedside echo - massive PE, suitability for thrombolysis

Question 9

Scoring system for PE

Answer 9

Well’s score
- 4 or less –> D-dimer. If high –> diagnostic imaging (by CTPA or V/Q scan)
* if low, PE excluded

• More than 4 - diagnostic imaging + LMWH

Question 10

why does a low D-dimer exclude a PE

Answer 10

The D-dimer has a high negative predictive value but a low specificity so is only useful if the clinical suspicion of a PE is low.

Question 11

PE: management

Answer 11

Acute
-ABCDE
-IV alteplase (haemodynamic instability)

Medical management
- DOAC (apixaban or rivaroxaban) once PE suspected

*In the inpatient/emergency setting, low molecular weight heparin is usually started instead as it is shorter acting.

Question 12

PE score for inpatient vs outpatient

Answer 12

PESI

Question 13

Alternatives to DOAC

Answer 13

If DOAC unsuitable:
*LMWH (5 days) followed by dabigatran or edoxaban OR LMWH followed by warfarin

Renal impairment <15/min - LMWH

Antiphospholipid syndrome - LMWH

Question 14

Length of anticoagulation

Answer 14

Provoked VTE - 3 months (up to 6 if cancer)
Unprovoked VTE - 6 months (ORBIT score for risk of bleeding)
If thrombophilia - lifelong

Question 15

When to consider IVC filter

Answer 15

Recurrent PE despite appropriate anticoagulation

Question 16

Target INR for VTE

Answer 16

2-3
(If recurrent PE, increase warfarin to so that INR 3-4)