Pulmonary embolism

Question 1

what is a pulmonary embolism

Answer 1

thrombus forms in deep vein (typically in legs) then it embolises to pulmonary artery + blocks blood flow

lungs are still ventilated but not perfused

Question 2

how does PE present

Answer 2

classic triad (rarely get all 3):
pleuritic chest pain
dyspnoea
haemoptysis

tachypneoa
tachycardia
hypoxia

signs of concomitant DVT:
unilaterally swollen, tender + inflamed calf

Question 3

what are the risk factors for a PE

Answer 3

factors which increase venous thrombosis (blood clot) risk

Virchows triad:

venous stasis - prolonged immobility e.g. bedbound, long hospital stay, long-haul flights, atrial fibrillation
hypercoagulability - combined oral contraceptive, HRT, pregnancy, malignancy, thrombophilias (e.g. antithrombin, protein C deficiency)
intravascular wall damage - hypertension, smoking, atherosclerosis

any past history or family history of venous thrombosis

Question 4

how are patients with suspected PE assessed

Answer 4

Well’s score:
if 4 or below - PE is unlikely –> D-dimer to exclude PE
If >4 - PE is likely –> CTPA

delay in getting CTPA –> give anticoagulation in the meantime

Question 5

what are the investigations in suspected PE

Answer 5

ECG - generally normal or just sinus tachycardia
“classic changes” - rarely seen —> S1Q3T3 –> large S wave in lead 1, large Q wave + inverted T wave in lead III
if PE is very large –> evidence of right heart strain –> right bundle branch block + right axis deviation
atrial fibrillation which could have caused PE

CXR - done to rule out other chest pain causes e.g. pneumonia, pneumothorax but is normal in PE

Bloods:
FBC - thrombocytopenia or anaemia –> more risk of complications after anticoagulation
thrombocytathemia or polycythaemia –> increased risk of VTE
U&Es - important to see if can do CTPA + affects dose of anticoagulation
Coagulation studies - influence choice of anticoagulation

Wells score >4–> CTPA or V/Q scan if patient has renal impairment, pregnant or contrast allergy
Wells score 4 or below —> d dimer (high sensitivity but low specificity, if -ve rules out PE but if elevated does not mean there is a PE)

Question 6

how does PE presentation vary based on size

Answer 6

massive embolus –> obstructive shock –> presents with signs of haemodynamic instability
e.g. hypotension, cyanosis (poor perfusion of extremities), tachycardia, tachypneoa
right heart strain evidence –> raised JVP, parasternal heave
patient needs immediate thrombolysis

small embolus can have completely normal presentation

Question 7

what is the gold standard for PE diagnosis

Answer 7

CTPA - CT pulmonary angiogram

if patient is pregnant, renal impairment or contrast allergy –> do V/Q scan

Question 8

what is the management for PE

Answer 8

haemodynamically stable:
DOACs - rivaroxaban or apixaban
for at least 3 months
if PE was provoked e.g. immobile due to prolonged hospital stay –> stop DOAC after 3 months
if PE was unprovoked –> continue for another 3 months (6 months total)
balance bleeding risk with risk of recurrent VTE

haemodynamically unstable e.g. hypotension:
thrombolysis
if thrombolysis is contraindicated due to bleeding risk –> embolectomy