282.3 🏥 內科專科考前版

282.3.1 Mechanistic Deep Dive

282.3.1.1 Factor V Leiden

  • G1691A mutation (R506Q)
  • Activated protein C cannot cleave factor Va → prolonged active Va
  • Heterozygous: 5x risk
  • Homozygous: 50x risk
  • More common in Caucasians

282.3.1.2 APS Mechanism

  • Antibodies against phospholipid-binding proteins (β2-GPI, prothrombin)
  • Disrupt anticoagulant pathways (protein C, antithrombin)
  • Activate platelets, endothelium, complement
  • Catastrophic APS: multiple organ thrombosis in days

282.3.1.3 HIT Pathophysiology

  • IgG antibody against PF4-heparin complex
  • Binds platelets → activation → microthrombi
  • Platelet count ↓ (50% from baseline) by day 5-10 of heparin
  • Stop heparin immediately, use argatroban/bivalirudin/fondaparinux

282.3.2 Recent Trials & Updates

282.3.2.1 EXTRACT-PE (2021) and FLAME (2023)

  • Mechanical thrombectomy (Indigo, FlowTriever) for intermediate-high and high-risk PE
  • ↓ major bleeding vs lysis
  • ↑ procedural success and RV recovery
  • 2024 ESC PE Guideline: Class IIa for catheter therapies

282.3.2.2 HI-PEITHO (2024)

  • Ultrasound-assisted CDT vs anticoagulation in intermediate-high PE
  • ↓ death, hemodynamic deterioration, recurrent PE
  • Strong support for CDT in submassive

282.3.2.3 ATTRACT (2017)

  • CDT for proximal DVT
  • No reduction in overall PTS
  • Reduced moderate-severe PTS in iliofemoral DVT
  • Practice: CDT in young iliofemoral with severe symptoms

282.3.2.4 CLOT-DVT (2024) Iliofemoral

  • Pharmacomechanical CDT for iliofemoral DVT
  • Improved patency and reduced PTS

282.3.2.5 Caravaggio (2020)

  • Apixaban vs dalteparin in cancer-VTE
  • Non-inferior, less bleeding (especially with apixaban)
  • DOAC first-line in cancer-VTE

282.3.2.6 TRAPS (2018)

  • Rivaroxaban vs warfarin in triple-positive APS
  • ↑ recurrence with DOAC
  • Warfarin preferred in triple-positive APS

282.3.2.7 PEITHO + Long-Term (2017)

  • Submassive PE: full-dose tPA
  • ↓ death/hemodynamic deterioration but ↑ major bleeding (especially ICH in elderly)
  • Use half-dose or CDT in selected

282.3.3 High-Yield Specialist Points

282.3.3.1 CTPH (Chronic Thromboembolic Pulmonary Hypertension)

  • Persistent dyspnea + PH after PE (3-5% of survivors)
  • V/Q scan most sensitive screening
  • Right heart cath + pulmonary angiography for diagnosis
  • Pulmonary endarterectomy (PEA): curative for proximal disease
  • Riociguat (sGC stimulator) for inoperable or persistent
  • Balloon pulmonary angioplasty (BPA): for distal disease

282.3.3.2 Distal DVT

  • Calf DVT controversial
  • Surveillance vs anticoagulation
  • 3 mo AC if symptomatic, risk factors, or extending
  • Otherwise serial US for 2 weeks

282.3.3.3 Upper Extremity DVT

  • 5-10% of DVT
  • Catheter-related (~ 70%)
  • Effort thrombosis (Paget-Schroetter) — young athletes
  • Anticoagulate; catheter removal if not needed; CDT for severe

282.3.3.4 IVC Filters

  • Indication: contraindication to AC, recurrent VTE despite therapeutic AC
  • Not adjunctive to AC routinely
  • Retrievable preferred
  • High retrieval rate failure → tracking system

282.3.3.5 PERT (Pulmonary Embolism Response Team)

  • Class I for severe PE
  • Cardio + pulmonology + vascular IR + ICU + surgery
  • Faster, more appropriate therapy

282.3.3.6 Pregnancy + VTE Workup

  • D-dimer often elevated in pregnancy (less reliable)
  • Compression US first
  • V/Q < CTPA fetal radiation, less breast dose
  • LMWH preferred treatment

282.3.3.7 Thrombophilia Testing

  • Don’t test routinely (Choosing Wisely)
  • Indications:
    • Unprovoked VTE in young
    • Recurrent VTE
    • Family hx
    • Pregnancy loss recurrent
  • Tests should be done OFF anticoagulation + after acute phase

282.3.3.8 COVID-19 + VTE

  • Increased risk during acute infection
  • Prophylactic AC in hospitalized
  • Therapeutic AC in select severe (REMAP-CAP, ATTACC, ACTIV-4)

282.3.3.9 Andexanet Alfa (Reversal)

  • For Xa inhibitor reversal (apixaban, rivaroxaban)
  • Approved for life-threatening bleeding
  • ANNEXA-4 study

282.3.3.10 Idarucizumab (Reversal)

  • For dabigatran reversal
  • Monoclonal antibody, monolayer

282.3.4 Pearls

  • Wells + D-dimer → US (DVT) or CTPA (PE)
  • Massive PE: thrombolysis (alteplase 100 mg) OR CDT/FlowTriever; PERT
  • DOAC first-line for most VTE; warfarin for APS triple-positive + mechanical valve
  • Cancer-VTE: DOAC (Caravaggio) or LMWH (GI/GU)
  • Pregnancy: LMWH; never DOAC
  • CTEPH: post-PE PH; PEA curative; riociguat / BPA
  • PERT for high/intermediate-high PE
  • EXTRACT-PE + HI-PEITHO: CDT and mechanical thrombectomy gaining ground vs systemic lysis