Hematology

Anticoagulation & Venous Thromboembolism (VTE)

Clinical Overview and Exam Mastery Guide for DVT, PE, DOACs, heparins, warfarin, HIT, thrombolysis, and therapy duration decisions.

VTE Core
DVT + PE
First-Line
DOACs in most patients
High-Risk PE
Thrombolysis if massive
Min Duration
3 months

Virchow Triad and VTE Risk Frame

Venous Stasis Endothelial Injury Hyper- coagulability Typical Risk Inputs Surgery Cancer Immobility Pregnancy / Estrogen

VTE risk rises when stasis, endothelial injury, and hypercoagulability overlap.

1. What Is VTE?

Venous thromboembolism (VTE) includes deep vein thrombosis (DVT) and pulmonary embolism (PE). It results from clot formation in the venous circulation and may progress from local thrombosis to life-threatening embolic obstruction.

DVT PE Recurrence risk Mortality prevention priority

2. Pathophysiology (Virchow's Triad)

1. Venous Stasis

  • Immobility
  • Post-operative state
  • Hospitalization

2. Endothelial Injury

  • Trauma
  • Surgery
  • Vascular inflammation

3. Hypercoagulability

  • Cancer
  • Pregnancy
  • Estrogen therapy

3. Clinical Presentation

DVT Pattern

  • Unilateral leg swelling
  • Pain/tenderness
  • Warmth

PE Pattern

  • Sudden dyspnea
  • Pleuritic chest pain
  • Tachycardia, hypoxia

4. Management Overview

Prevent clot extension Prevent recurrence Reduce mortality
Initial anticoagulation choice is driven by clinical stability, renal function, pregnancy/mechanical valve status, and bleeding risk.

5. First-Line: DOACs (Preferred in Most Patients)

Core agents: apixaban, rivaroxaban, edoxaban, and dabigatran.

Drug MOA Major Side Effects Contraindications
Apixaban Direct factor Xa inhibitor Bleeding, GI bleeding Active bleeding, severe renal impairment (agent specific)
Rivaroxaban Direct factor Xa inhibitor Bleeding, GI bleeding Active bleeding, severe renal impairment (agent specific)
Edoxaban Direct factor Xa inhibitor Bleeding Active bleeding, severe renal impairment (agent specific)
Dabigatran Direct thrombin (factor IIa) inhibitor Bleeding, GI symptoms Active bleeding, severe renal impairment, mechanical heart valve
Benefits: fixed dosing, no routine INR monitoring, and lower intracranial bleeding risk versus warfarin in many populations.

6. Heparins

A. Unfractionated Heparin (UFH)

  • MOA: activates antithrombin, inhibiting thrombin and factor Xa
  • Monitoring: aPTT
  • Major side effects: bleeding, heparin-induced thrombocytopenia (HIT)
  • Reversal: protamine sulfate

B. Low Molecular Weight Heparin (LMWH, e.g., Enoxaparin)

  • MOA: antithrombin-mediated factor Xa inhibition (less thrombin effect)
  • Benefits: predictable dosing, no routine monitoring
  • Side effects: bleeding
  • Contra/caution: severe renal impairment (dose adjustment needed)

7. Warfarin

Still important in mechanical heart valves, severe kidney disease, and antiphospholipid syndrome.

Mechanism and Monitoring

  • MOA: inhibits vitamin K epoxide reductase
  • Effect: reduced synthesis of factors II, VII, IX, X
  • Monitoring: INR target 2 to 3 in most indications

Safety and Reversal

  • Major side effects: bleeding, rare skin necrosis
  • Contraindications: pregnancy (teratogenic), active bleeding
  • Reversal options: vitamin K, PCC, FFP

8. Duration of Therapy

Provoked VTE

Typically 3 months.

Unprovoked VTE

Consider extended therapy based on recurrence and bleeding risk.

Cancer-Associated Thrombosis

DOAC or LMWH strategy depending on context.

9. Pulmonary Embolism Severity and Thrombolysis

Massive PE (hypotension/shock) requires urgent reperfusion consideration, including thrombolysis.

Alteplase (Thrombolytic)

  • MOA: converts plasminogen to plasmin, dissolving fibrin clot
  • Major side effects: major bleeding, intracranial hemorrhage
  • Contraindications: active bleeding, recent major surgery, history of hemorrhagic stroke

10. Special Situations

Pregnancy

LMWH is preferred.

Mechanical Valve

Warfarin preferred; DOACs contraindicated.

HIT

Stop all heparin and use argatroban or bivalirudin.

Management Recap Drill

DVT/PE 1: Confirm diagnosis.
DVT/PE 2: Start DOAC in most patients.
DVT/PE 3: Use heparin bridge if initiating warfarin.
DVT/PE 4: Treat at least 3 months.
DVT/PE 5: Reassess recurrence risk for extension decisions.
Massive PE: Consider thrombolysis.
HIT: Stop heparin immediately.

Visual Algorithm Placeholder

[Insert VTE Treatment and Anticoagulation Flowchart Here During UI Integration]

Guideline References (Management)

CHEST Guideline: Antithrombotic Therapy for VTE Disease

https://journal.chestnet.org

ACC Expert Consensus on Anticoagulation

https://www.acc.org/guidelines
These references guide DOAC preference, duration decisions, cancer-associated thrombosis strategies, and thrombolysis indications.

11. Common Exam Traps

DOACs are preferred over warfarin in most VTE scenarios.
Warfarin requires heparin bridge at initiation.
Mechanical valves: DOACs are contraindicated.
Pregnancy: LMWH is preferred.
HIT management starts with stopping all heparin.

12. Quick Revision Summary

Must Remember

  • VTE = DVT + PE
  • DOACs are first-line in most patients
  • Warfarin remains useful in selected special groups
  • Massive PE may require thrombolysis
  • Minimum treatment is usually 3 months

Practice Questions Placeholder

  • Topic: VTE and Anticoagulation
  • Subtopics: DOACs, warfarin, heparins, HIT, thrombolysis, therapy duration