USMLE Prep - Medical Reference Library

Deep Vein Thrombosis — ED Diagnosis and Initial Therapy

System: Cardiology • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Use Wells score and D dimer to guide ultrasound; start anticoagulation when DVT is confirmed or highly suspected without major contraindications.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

DVT should be considered in unilateral limb swelling, pain, and erythema, particularly with recent surgery, immobility, cancer, or prior VTE. Use Wells score to categorize probability and apply D‑dimer in low/intermediate risk; duplex ultrasonography confirms diagnosis. Evaluate for PE symptoms and bleeding risk to plan therapy.


Treatment Strategy & Disposition

Anticoagulate with DOACs for most patients, LMWH for cancer, and heparin/warfarin when DOACs are unsuitable. Consider catheter‑directed therapy for limb‑threatening iliofemoral DVT (phlegmasia). Plan duration based on provoking factors; provide compression for symptom control and counsel on recurrence risks. Outpatient management is appropriate for reliable, low‑risk patients; admit if extensive clot burden, high bleeding risk, or comorbidity.


Epidemiology / Risk Factors

  • Atherosclerotic risk (HTN, DM, HLD, smoking)
  • Age/family history of premature CAD

Investigations

TestRole / RationaleTypical FindingsNotes
EKGRhythm/ischemiaST-T changes/arrhythmiaSerial
TroponinMyocardial injuryDynamic rise/fallTrend
CXRPulmonary edema/sizeCardiomegaly/edema
BMP/Mg2+Electrolytes/renalDerangements
CBC/CoagsBleeding riskAbnormal/INR

When to Image

ScenarioPlan
Low probability and negative D dimerNo imaging
Intermediate probability or positive D dimerCompression ultrasound
High probabilityUltrasound and consider empiric anticoagulation

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
Enoxaparin (LMWH)Xa>IIa inhibitionHoursInitial ACAvoid severe renal failure; ED use
Apixaban/RivaroxabanFactor Xa inhibitionHoursOutpatient/inpatient therapyBleeding; interactions; ED use
Warfarin (selected)Vitamin K antagonistDaysMechanical valves/antiphospholipidINR monitoring; ED use

Prognosis / Complications

  • Prognosis by ischemic burden/LV function
  • Arrhythmias and HF are complications

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Consider iliac or IVC thrombosis in extensive swelling with negative leg ultrasound. Adjust strategy for pregnancy or cancer.


References

  1. ASH VTE Guidelines — DVT — Link
  2. ACEP Clinical Policy — VTE — Link