Pulmonary embolus

Question 1

Definition of PE

Answer 1

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

Question 2

Causes of PE

Answer 2

• 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
• always suspect PE if patient develops fever, sudden dyspnea, chest pain, or collapse 1-2 wk after surgery

Question 3

Risk factors of PE

Answer 3

Virchow’s triad:
• stasis
- immobilization: paralysis, stroke, bed rest, prolonged sitting during travel, immobilization of an extremity after fracture
- obesity, CHF
- chronic venous insufficiency
• endothelial cell damage
- post-operative injury, trauma
• hypercoagulable states
- underlying malignancy (particularly adenocarcinoma)
- cancer treatment (chemotherapy, hormonal)
- exogenous estrogen administration (OCP, HRT)
- pregnancy, post-partum
- prior history of DVT/PE, family history
- nephrotic syndrome
- coagulopathies: Factor V Leiden, Prothrombin 20210A variant, inherited deficiencies of antithrombin/protein C/protein S, antiphospholipid antibody, hyperhomocysteinemia, increased Factor VIII levels, and myeloproliferative disease
• increasing age

Question 4

Px of PE

Answer 4

• fewer than 30% of patients have clinical evidence of DVT (e.g. leg swelling, pain or tenderness)

Question 5

What is in Wells criteria

Answer 5

Clinical signs of DVT - 3.0
No more likely alternative Dx - 3.0
Immobilisation or surgery in previous 4 weeks - 1.5
Previous PE/DVT - 1.5
HR >100bpm - 1.5
Hemoptysis - 1.0
Malignancy - 1.0

Clinical Pr
0-2: low 3%
3-6: intermediate 28%
>6: high 78%

Question 6

When do you use D-Dimers?

Answer 6

only if low clinical probability, otherwise go straight to spiral CT

If D-dimer is -ve, PE is ruled out.

If D-dimer is +ve, order CT scan.

Question 7

What is the classic ECG findings of PE?

Answer 7

S1-Q3-T3 (inverted T3).

but commonly see only sinus tachycardia

Question 8

When is D-dimer elevated?

Answer 8

• recent surgery
• cancer
• inflammation
• infection
• severe renal dysfunction

Question 9

Ix of PE

Answer 9

• CTPA (commonly used)
• venous duplex U/S or Doppler
• CXR ( frequently normal; no specific features)
• ECG (Not sensitive/specific. RV strain, RAD, RBBB, S1-Q3-T3 with massive embolization)
• D-dimer (to exclude DVT/PE if pretest probability is already low)
• Pulmonary Angiogram (Gold Standard but rarely used)

Question 10

Rx of PE

Answer 10

• admit for observation (patients with DVT only are often sent home on LMWH)
• oxygen: supplemental O2 if hypoxemic or short of breath
• pain relief: analgesics if chest pain – narcotics or acetominophen

1. acute anticoagulation: therapeutic-dose SC LMWH or IV heparin – start ASAP
   
   • for SC LMWH: dalteparin 200 U/kg once daily or enoxaparin 1 mg/kg bid – no lab monitoring – avoid or reduce dose in renal dysfunction
   • for IV heparin: bolus of 75 U/kg (usually 5,000 U) followed by infusion starting at 20 U/kg/h – aim for aPTT 2-3x control
2. interventional thrombolytic therapy
   
   • massive PE is preferentially treated with catheter-directed thrombolysis by an interventional radiologist
   • works better than IV thrombolytic therapy and fewer contraindications
3. IVC filter: only if recent proximal DVT + absolute contraindication to anticoagulation (e.g. recent stroke)

Question 11

How do you anticoagulate previous PE patients long term?

Answer 11

• warfarin: start the same day as LMWH/heparin – overlap warfarin with LMWH/heparin for at least 5 d and until INR in target range of 2-3 for at least 2 d
  
  • LMWH (e.g. clexane) instead of warfarin for pregnancy, active cancer, or high bleeding risk patients
  • dabigatran has been shown to have lower bleeding risk than warfarin