Tutorial #24: Pulmonary Embolism

Question 1

What three major risk factors for thrombosis? (Virchows Triad)

Answer 1

1. Disruption in blood flow (stasis)
2. Hypercoagulability
3. Endothelial cell damage

Question 2

What is the most common symptom of a pulmonary embolism?

Answer 2

Dyspnea (breathlessness)

Question 3

For a patient with a low clinical likelihood of DVT and PE (through Wells and YEARS respectively), what test should be ordered?

Answer 3

D-dimer

Question 4

For a patient with a high clinical likelihood of DVT and PE (through Wells and YEARS respectively), what test should be ordered?

Answer 4

imaging test (ex. CT chest angiogram)

Question 5

What is the most common symptom of DVT?

Answer 5

Swelling (present 97% of the time) and pain (present 86% of the time).

Question 6

Is the d-dimer test for PE a rule-in, or rule-out test, and why?

Answer 6

Rule out test.

This is because the d-dimer lacks specificity. A positive d-dimer can be due to a variety of reasons (MI, pneumonia, sepsis, malignancy, etc) (remember SpIn - SPECIFICITY for RULE IN), and has a high chance of false positive. It’s sensitivity (SnOUT - SENsitivity for RULE OUT) is 90% regardless of risk, but its sensitvity drops significantly the higher risk the patient. Remember, we use d-dimer in patients that have low pre-test probability of having PE.

Question 7

What is the most common abnormalities found on EKG for a pt. with a Pulmonary Embolism?

Answer 7

sinus tachycardia + T wave inversion in leads V1-V4

Note: The clasically taught “S1Q3T3 sign” is neither sensitive nor specific.

Question 8

What is Wells Criteria for Pulmonary Embolism? (x7 criteria)

Answer 8

1. Clinical signs and symptoms of DVT = 3
2. PE is #1 diagnosis OR equally likely = 3
3. Heart rate > 100 = 1.5
4. Immobilization at least 3 days OR surgery in the previous 4 weeks = 1.5
5. Previous, objectivey diagnosied PE or DVT = 1.5
6. Hemoptysis = 1
7. Malignancy w/ treatment within 6 months or palliative = 1

Question 9

Pt. has a WELLs score of ≤ 4 , in the two tier model of Wells what is the best investigation at this point in time?

Answer 9

consider D-dimer. If negative, stop work-up for PE, if positive -> CTA

PE unlikely (0-4 points). Remember we use the d-dimer only in patients where the pre-test probability is low.

Question 10

Pt. has a WELLs score of > 4 , in the two tier model of Wellswhat is the best investigation at this point in time?

Answer 10

Consider CT angiogram

Pt. has a high pre-test probabilty of PE, so d-dimer is not useful at this time.

Question 11

What is the PERC rule for Pulmonary embolism (definition not criteria)

Answer 11

It is a clinical decision tool that is used to rule out PE.

PE is ruled out if NO criteria are present, and the pre-test probabilily is < 15%

Question 12

What are the criteria for the PERC rule for PE?

Answer 12

1. Age > 50 = 1
2. HR > 100 = 1
3. SaO2 on room air < 95% = 1
4. Unilateral leg swelling = 1
5. Hemoptysis = 1
6. Recent surgery or trauma = 1
7. Prior PE or DVT = 1
8. Hormone use = 1

If any of these features are present, you cannot rule out PE.

Question 13

What are the limitations to clinical decision tools such as Wells, and PERC? (x4)

Answer 13

1. Validity (does it actually measure what it says it does)
2. Reliability (i.e does it produce consistent results)
3. Practicality (it is easy to use)
4. Applicability/generalizability (can it be used on your patient population)

Question 14

What are the top 4 most common symptoms of PE?

Answer 14

1. Dyspnea
2. Chest pain (pleuritic)
3. Calf or thigh pain and/or swelling
4. Tachypnea

Tip from A and C - we’ve had a lot of questions where hemoptysis was also a presenting complaint, and although low prevalence in the list above, think about PE if it comes up in a question!

Question 15

What are the positive predictors of Cardiac chest pain/ACS? (x3)

Answer 15

1. Exertional chest pain
2. Pain improved with resting
3. Pain that radiates to arms or neck.

Question 16

What are the two MOST IMPORTANT test you would order when suspecting ACS? (x2)

Answer 16

EKG
Troponin

Question 17

What are positive predictors of Pericarditis on history?

Answer 17

Pleuritic chest pain, that improves with leaning forward, worse when laying flat.

Question 18

What is a positive predictor for pericarditis on physical exam?

Answer 18

Pericardial friction rub during chest auscultation.

Question 19

What are the typical findings of pericarditis on ECG?

Answer 19

Diffuse ST elevation and PR depression.

Pericarditis is classically associated with ECG changes that evolve through four stages.
Stage 1 – widespread STE and PR depression with reciprocal changes in aVR (occurs during the first two weeks)
Stage 2 – normalisation of ST changes; generalised T wave flattening (1 to 3 weeks)
Stage 3 – flattened T waves become inverted (3 to several weeks)
Stage 4 – ECG returns to normal (several weeks onwards)

Question 20

What are the positive predictors of a Spontaneous Pneumothorax? (x4)

Answer 20

1. Sudden onset dyspnea
2. Pleuritic chest pain on the side of collapse
3. Hyper-resonance on percussion on side of collapse
4. decreased breath sounds.

Question 21

What test would you organize when suspecting pneumothorax on a stable patient?

Answer 21

Chest x-ray as initial test - it has reasonable sensitivity and give you measurements for “small vs large”.

Ultra-sound is even more sensitive, but it does not reliably tell you size.

Question 22

What are the positive predictors of Pneumonia?

Answer 22

1. Pleuritic chest pain
2. Fever
3. productive cough

Question 23

What are the positive predictors of CHF/pulmonary edema? (x3)

Answer 23

1. SOB, orthopnea, PND
2. Peripheral edema and elevated JVP (may be present)
3. usually not painful.

Question 24

What are the positive predictors of COPD exacerbation (x3)

Answer 24

1. Positive COPD history
2. Wheezing and dyspnea (either development of or worsening)
3. change in sputum volume or color

Question 25

What would spirometry or PFT show in a COPD exacerbation?

Answer 25

PFT showing an obstructive pattern, that has lack of response to bronchodilators.

Question 26

What are the positive predictors of Asthma? (x3)

Answer 26

1. Has other atopy (allergies, chronic rhinitis) 2. Response to irritants (smoking, smoke, exercise) 3. Wheezing on auscultation

Question 27

What would you see on PFT for a patient that has Asthma?

Answer 27

PFT showing obstructive pattern that is responsive to brhonchodilators.

Question 28

What are Hampton’s Hump and Westermark’s Sign on chest X-ray?

Answer 28

Hampton’s Hump is a wedge-shaped opacity representing infarction; Westermark’s Sign is focal oligemia distal to a PE.

Question 29

When is a V/Q scan preferred over CTPA in suspected PE?

Answer 29

In pregnancy or renal impairment where contrast or radiation exposure is a concern.

Question 30

What are the key differences between massive, submassive, and low-risk PE?

Answer 30

Massive: Sustained hypotension or shock Submassive: RV strain without hypotension Low-risk: Hemodynamically stable, no RV strain

Question 31

Why can't the YEARS score be used in unstable patients?

Answer 31

YEARS is only validated in hemodynamically stable patients without hypoxia or shock.

Question 32

What ECG findings may suggest RV strain in PE?

Answer 32

T-wave inversion in V1–V4, incomplete RBBB, S1Q3T3 (not specific).

Question 33

What echocardiographic finding is associated with PE-induced RV strain?

Answer 33

RV dilation, septal flattening, McConnell’s sign (akinesia of mid-RV wall with preserved apex motion)

Question 34

What is the pathophysiology behind hypoxia in PE?

Answer 34

Ventilation-perfusion mismatch due to impaired blood flow to ventilated alveoli.

Question 35

Define 'provoked' vs 'unprovoked' PE.

Answer 35

Provoked: Triggered by a transient risk factor (e.g. surgery, trauma) Unprovoked: No clear provoking factor identified

Question 36

Why is pregnancy a risk factor for PE?

Answer 36

It increases clotting (hypercoagulability) and venous stasis from uterine pressure on veins.

Question 37

How long should anticoagulation be continued after a first provoked PE?

Answer 37

Typically for 3 months.

Question 38

What is the indication for thrombolysis in PE?

Answer 38

Massive PE with hemodynamic instability; consider in some submassive PE with RV dysfunction

Question 39

What blood gas abnormality is commonly seen in PE?

Answer 39

Respiratory alkalosis due to hyperventilation, possibly with hypoxemia.

Question 40

What is the clinical significance of McConnell’s sign on echo?

Answer 40

Suggests acute right ventricular strain, often due to PE.

Question 41

When can age-adjusted D-dimer be used and what is the formula?

Answer 41

Use in patients over 50. Formula: age × 10 µg/L (or × 5 µg/L in WRHA labs)

Question 42

What is a practical limitation of the Wells score in PE evaluation?

Answer 42

Subjectivity of the “PE most likely” criterion may reduce consistency across clinicians.

Question 43

What clinical signs may mimic DVT but are due to other diagnoses?

Answer 43

Cellulitis, ruptured Baker’s cyst, and postphlebitic syndrome.

Question 44

When might a D-dimer give a false-positive?

Answer 44

In older patients, malignancy, infection, inflammation, pregnancy, or recent surgery.

Question 45

Why is PE called “The Great Masquerader”?

Answer 45

Because its symptoms are vague and mimic many other conditions, requires a high index of suspicion.

Question 46

What is the most common presentation of submassive PE?

Answer 46

Dyspnea with RV strain on imaging or biomarkers (e.g. troponin), without hypotension.