raised JVP. Which of the following inv will be most helpful in leading to a dx?
a. CXR
b. CTPA
c. V/Q scan
d. D-Dimer
e. Doppler US of legs
answer: B
Pulmonary Embolism
• lodging of a blood clot in the pulmonary arterial tree
with subsequent increase in pulmonary vascular resistance, impaired V/Q
matching, and possibly reduced pulmonary blood flow
Etiology and
Pathophysiology
• one of the most common causes of preventable death in
the hospital
• proximal leg thrombi (popliteal, femoral, or iliac
veins) are the source of most clinically recognized pulmonary emboli
• thrombi often start in calf, but must propagate into
proximal veins to create a sufficiently large thrombus for a clinically
significant PE
• fewer than 30% of patients have clinical evidence of
DVT (e.g. leg swelling, pain, or tenderness)
• always suspect PE if patient develops fever, sudden
dyspnea, chest pain, or collapse 1-2 wk after surgery
Pulmonary
Angiogram (Gold Standard)
Filling defect indicative of embolus; negative angiogram
excludes clinically relevant PE
More invasive, and harder to perform than CT, therefore
done infrequently
D-Dimer
Highly sensitive D-dimer result can exclude DVT/PE if pretest
probability is already low, little value if pretest probability is high
If D-dimer positive, will need further evaluation with
compression U/S
CT Angiogram
Both sensitive and specific for PE
Diagnosis and management uncertain for small filling defects
CT may identify an alternative diagnosis if PE is not
present
CT scanning of the proximal leg and pelvic veins can be
done at the same time and may be helpful
Venous Duplex U/S
or Doppler
With leg symptoms
Positive test rules in proximal DVT
Negative test rules out proximal DVT
Positive test rules in proximal DVT
Negative test does not rule out a DVT: patient may have
non-occlusive or calf DVT
Findings not sensitive or specific
Sinus tachycardia most common; may see non-specific ST
segment and T wave changes
RV strain, RAD, RBBB, S1-Q3-T3 with massive embolization
Frequently normal; no specific features
Atelectasis (subsegmental), elevation of a hemidiaphragm
Pleural effusion: usually small
Hampton’s hump: cone-shaped area of peripheral
opacification representing infarction
Westermark’s sign: dilated proximal pulmonary artery with
distal oligemia/decreased vascular markings (difficult to assess without prior
films)
Dilatation of proximal PA: rare
V/Q Scan Very
sensitive but low specificity
Order scan if
CXR normal, no COPD
Contraindication to CT (contrast allergy, renal
dysfunction, pregnancy)
Avoid V/Q scan if
CXR abnormal or COPD
Inpatient
Suspect massive PE
Results
Normal: excludes the diagnosis of PE
High probability: most likely means PE present, unless
pre-test probability is low
60% of V/Q scans are nondiagnostic
Useful to assess massive or chronic PE
Not routinely done
No diagnostic use in PE (insensitive and nonspecific)
May show respiratory alkalosis (due to hyperventilation)
PE Rule Out
Criteria (PERC)
• Age <50 yr
• Heart rate less than 100 bpm
• Oxyhemoglobin saturation ≥95 percent
• No hemoptysis
• No estrogen use
• No prior DVT or PE
• No unilateral leg swelling
• No surgery or trauma requiring hospitalization within
the past 4 wk
Acute PE can probably be excluded without further diagnostic
testing if the patient meets all PERC
criteria AND there is a low clinical suspicion for PE
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