Pulmonary Embolism

Question 1

37 yr old female

Sudden onset right sided chest pain, pleuritic

Dyspnea associated with pain

Previously well

No symptoms of DVT or pneumonia

What is the differential diagnosis?

Answer 1

Doesn’t tell us the diagnosis, tells us the location

Air-space disease

Rounded area

RLL peripheral pulmonary infiltrate

DDx:

• Acute PE
• Pneumonia

Question 2

What is pulmonary embolism?

Why is it important to know?

Answer 2

Blood clot in the lungs

Important because:

• Common
• Life threatening
• Challenging to diagnose
• Treatable

Question 3

Why do PEs have so many different clinical presentations?

Answer 3

Because PEs most often come from DVTs, and can end up in many different areas of the lungs, leading to different clinical presentations.

Question 4

Where do PEs originate from?

Answer 4

90% from DVT

10% from other large veins

NOT from superficial veins

Question 5

What is VTED?

Answer 5

Venous thrombo-embolic disease

VTED = DVT + PE

Question 6

Pathophysiological response to PE?

Answer 6

• Usually bilateral perfusion defects
• Infarct (large clots, other impairment, not common)
• Abnormal gas exchange
• Cardiovascular compromise (mechanical occlusion)

Question 7

What does this path specimen show?

Answer 7

This image shows pulmonary infarct, from some compromise of the pulmonary blood flow.

Can occur with large PE, or with atherosclerosis of the pulmonary arteries

Question 8

How do we diagnose PE?

Answer 8

• History (HPI, PMHx, risk factors)
• Physical exam
• CXR, EKG
• D-dimer
• V/Q scans
• Doppler US of legs
• Chest CT scans via ‘PE protocol’

Question 9

Signs and symptoms of PE?

Answer 9

Dyspnea, pleuritic chest pain, hemoptysis (small volume)

Tachypnea, tachycardia, R-sided S4, loud P2, pleural rub, fever

Question 10

Risk factors that increase PE?

Answer 10

• Immobilization
• Surgery (within the last 3 months)
• Malignancy (esp. pancreatic, prostate)  Stroke
• Previous DVT/PE
• Heavy Smoking
• Obesity
• Hypertension
• Coagulation abnormalities ie..Factor V Leiden mutation

Question 11

What initial tests do we order if we suspect PE?

Answer 11

Arterial blood gas

EKG - non-specific

Clinical pearl: if EKG signs of RV hypertrophy, think of chronic pulmonary vascular process, not just acute PE going on

CXR - non-specific

Question 12

Radiographic features of PE?

Answer 12

Hampton’s Hump - wedge-shaped opacity in the lung, peripheral

Pleural effusion

Westermark sign - oligemia (dont see vessels) of one lung, from large burden of emboli

ADD PICTURES

Question 13

What is the D-dimer test?

Answer 13

Non-specific test for PE; most common cause of false positive is pneumonia

High sensitivity (98%)

Poor overall specificity (30-50%)

Question 14

How do we image for DVT?

Answer 14

Doppler US of the Leg

Look for non-compressible deep venous segments

If negative, useful in increasing negative predictive value of a chest imaging modality for acute PE

On it’s own, not useful. Clot may have embolized already.

Question 15

What do we use the Wells Score for?

Answer 15

Wells score is used to determine the clinical (pre-test) probability that a patient has a PE

Low risk: 0-1

Int risk: 2-6

High risk: > 6 (high pre-test suspicion)

Modified Wells Score

PE unlikely: 0-4

PE likely: >4

Question 16

What is this scan?

Answer 16

Ventilation perfusion scan

Patient breathes in radio-labelled particles

Rotated images at 360 degrees

Also inject venously with labelled particles and look at lung

Looking for an area where there is ventilation, but a defect in perfusion

Posteriorly there is a large defect

Question 17

What did the PIOPED study find about Wells Score and V/Q test?

Answer 17

If you have high prob of PE from V/Q scan, and high clinical probability based on Wells, 96% actually have PE.

V/Q is only useful in some scenarios:

When Well’s is high and V/Q suspicion is high

When V/Q suspicion is NORMAL, predicts NO PE despite Well’s score being high

If the patient has a LOW Well’s pre-test score, we DON’T order teh V/Q scan because it leads to false-positives

Question 18

When is the V/Q scan useful?

Answer 18

• High probability Result: IF High pretest probability → Post test probability of PE is very high (96%) and can use to diagnose PE
• Intermediate probability Result: Non-diagnostic
• Low probability Result: Non-diagnostic in most cases
• Normal/near normal Result —> High sensitivity → can use to exclude PE

Question 19

What is this image?

Answer 19

Coronal image of a CT Pulmonary Angiogram

Left is normal

Right has positive filling defect in the RLL, consistent with PE

Question 20

When is the CTPA useful as a diagnostic tool?

Answer 20

 High pretest probability with positive CTA : Post test probability of PE is very high (96%); can be used to diagnose PE

 Low pretest probability with positive CTA : Only 58% have PE; thus false positives exist when test ordered in this situation

 High pretest probability with negative CTA : 60% still have underlying PE. Further testing required.

 Low pretest probability with negative CTA : Useful to rule out PE

The same is true for when it is useful to image the legs to rule in or out a PE.

Question 21

What algorithm do we go through to determine how to investigate a potential PE?

Answer 21

Determine if PE is likely or unlikely using Modified Wells Score, and go from there using this flow chart

D-dimer done first in some cases because it is cheap, easy, and has a good negative predictive value.

(if patient has likely PE, and then a negative CTPA, consider doing extra testing to confirm - leg doppler, other imaging)

Question 22

What occurs to the pulonary arterial pressure (PAP) when a patient has a massive PE?

What can result from these changes in PAP?

Answer 22

If a patient has more than 50% obstruction, there is often an increase in PAP. With 75% obstruction, the meanPAP can increase close to 40 mmHg, which results in RV failure.

This hemodynamic compromise leads to hypoxemia –> vasoconstriction –> further increase in meanPAP –> RV “death spiral”

(Underlying heart disease is associated with worse outcomes with acute PE for this reason)

Question 23

What are the signs, symptoms, and findings of a massive PE, with obstruction of the artery?

Answer 23

Symptoms: severe dyspnea, syncope

Signs: tachycardia, tachypnea, hypotension, increased JVP, R-sided S3, increased P2, RV lift

CXR: nonspecific, westermark sign

EKG: S1Q3T3, new R bundle branch block, inverted T waves (precordial)

Echo: dilated RV, septal deviation

Question 24

What is the main treatment for PE?

Answer 24

Anticoagulation: initial and chronic

IVC filter: for those who cannot be anti-coagulated; increased risk for distal DVT

Massive PE: standard anti-coagulation + thrombolysis

Question 25

What is used for inital anticoagulation?

Chronic anticoagulation?

Answer 25

Initial: LMWH (sometimes Fondaparinux)

Chronic: warfarin, oral FXa inhibitor (rivaroxaban, apixaban

Question 26

What is CTEPH?

Answer 26

Chronic thromboembolic pulmonary hypertension

Incomplete PE resolution in approximately 4% of all PEs

Treated surgically

Question 27

How do we monitor patients with PE?

Answer 27

• Monitor anticoagulation
• Watch for complications (infarct, unstable)
• CTEPH
• Complications of therapy itself (bleeding, HIT)
• Risk of VTE recurrence and bleeding