Summary

Deep Vein Thrombosis (DVT) is the formation of a thrombus (blood clot) within the deep venous system, predominantly in the lower extremities. It is a critical diagnosis because 50% of untreated proximal DVTs embolise to the lungs (Pulmonary Embolism - PE), which carries a high mortality. The cornerstone of management is rapid anticoagulation to prevent clot propagation and embolisation.

Epidemiology

• Incidence: 1 in 1,000 per year in the general population.
• Age: Risk increases exponentially with age (>40).
• Gender: Slightly higher in males (except during reproductive years due to pregnancy/OCP).
• Recurrence: 30% recurrence rate within 10 years if unprovoked.

Clincial Summary Table

Glossary for Patients

• Thrombus: A blood clot formed in situ.
• Embolus: A clot that has moved.
• Proximal DVT: Above the knee (Popliteal or higher). High risk.
• Distal DVT: Below the knee (Calf veins). Lower risk.
• Anticoagulant: "Blood thinner" (actually a "clot preventer").

The "Silent Killer"

Warning: Up to 50% of DVT cases are asymptomatic until they embolise. A high index of suspicion is required in patients with risk factors, even if the leg looks "normal".

Red Flags (Emergency Referral)

• Dyspnoea/Chest Pain: Suggests PE.
• Phlegmasia Cerulea Dolens: Painful Blue Edema. Indicates total venous occlusion -> Venous Gangrene -> Amputation risk.
  • Pathophysiology: Massive thrombosis blocks ALL venous return -> Pressure rises -> Arterial flow is comprised by compartment pressure.
  • Action: Immediate Vascular Surgery referral (Thrombectomy).
• Phlegmasia Alba Dolens: Painful White Edema ("Milk Leg"). Arterial spasm due to massive DVT.
• Hypotension: Suggests massive PE.

How long to treat?

1. Provoked (Transient Risk Factor):
   • Surgery, Trauma, OCP, Long haul flight.
   • Duration: 3 Months.
   • If risk factor removed, stop.
2. Unprovoked (No cause found):
   • Duration: 3 Months minimum, then reassess.
   • Long Term?: Men have higher recurrence risk. Consider indefinite if low bleeding risk.
   • Decision Tool (DASH Score):
     • D-dimer positive (post-rx)? (+2)
     • Age <50? (+1)
     • Sex Male? (+1)
     • Hormone use? (-2)
     • High score (>1) favours stopping? No, favours CONTINUING. (Actually, high score = high recurrence risk -> Continue).
3. Active Cancer:
   • Duration: Indefinite (LMWH or Edoxaban/Rivaroxaban) until cancer "cured".
4. Recurrent VTE:
   • Duration: Indefinite (Lifelong).

Special Populations

1. Pregnancy:
   • Risk: 5-10x higher (hypercoagulable state + venous stasis from uterus).
   • Drug: LMWH is Gold Standard (DOACs cross placenta -> Teratogenic).
   • Duration: Throughout pregnancy + 6 weeks postpartum.
2. Cancer-Associated Thrombosis (CAT):
   • Risk: Tumours release Tissue Factor. Chemotherapy damages endothelium.
   • Drug: LMWH was historic gold standard. DOACs (Apixaban/Edoxaban/Rivaroxaban) are now non-inferior (except in GI/Urothelial cancers where bleeding risk is higher).
3. IV Drug Users (IVDU):
   • Risk: Direct endothelial trauma (Femoral vein injecting - "Groin hitting").
   • Issue: Compliance/Follow-up.
   • Drug: Rivaroxaban (One drug, no monitoring) often best if adherence possible.
4. Upper Limb DVT (Paget-Schroetter):
   • Cause: Repetitive movement (Tennis/Painting) compresses vein at thoracic outlet.
   • Group: Young, healthy athletes.
5. DVT in Children:
   • Rare: Usually secondary to CVC lines or severe illness (cancer/sepsis).
   • Rx: LMWH is preferred (titrated to Anti-Xa levels). Warfarin is tricky. DOACs emerging (Riveroxaban granules).

Familial & Genetic Counselling

• "Will my kids get it?":
  • Factor V Leiden: Autosomal Dominant (50% chance).
  • Advice: We generally do NOT test children. It does not change management (we don't anticoagulate kids prophylactically).
  • Girl Power: Daughters should know before starting Combined OCP.
  • Life Insurance: Genetic testing can impact insurance premiums (depending on country). Think before testing.

Counselling: The OCP & HRT

• Current Clot: Stop Estrogen-containing OCP immediately. Switch to Progesterone-only (Mini-pill) or coil.
• Future: Estrogen is contraindicated lifelong.
• Family History: If a first-degree relative had a VTE <45, test for thrombophilia before starting OCP.

Anatomical Variants (The Zebras)

• May-Thurner Syndrome:
  • Anatomy: The Right Common Iliac Artery compresses the Left Common Iliac Vein against the spine.
  • Result: Recurrent Left Leg DVT in young women.
  • Rx: Often needs a Stent + Anticoagulation.
• Nutcracker Syndrome:
  • Anatomy: The Left Renal Vein is compressed between the Aorta and SMA (Superior Mesenteric Artery).
  • Signs: Flank pain, Haematuria, Left-sided Varicocele (in men).
  • Risk: Can predispose to Renal Vein Thrombosis.
• Trousseau's Syndrome:
  • Sign: Migratory thrombophlebitis (Clots moving around).
  • Cause: Occult Pancreatic/Lung Cancer (Mucin production triggers clotting).

Take Home Message: > 1. Do not stop the meds: The clot is still there. The drug stops it growing. > 2. Move: Walk around. Bed rest makes it worse. > 3. Bleeding Risk: You will bruise easily. Avoid contact sports. Seek help for black stools or nosebleeds >10 mins.

Frequently Asked Questions

• "Will the clot go away?": Use the analogy: "The tablet is like putting cement on the wall to stop it crumbling. Your body's cleaners (Plasmin) will chip away the old cement over months."
• "Can I fly?": Not for the first 2-4 weeks. After that, yes, but keep taking the tablet.
• "Do I need stockings?": Only if your leg is swollen and they make it feel better. They don't prevent PTS.

Travel Advice (Long Haul)

For future trips.

• Hydration: Drink water, avoid alcohol (diuretic).
• Movement: Walk the aisle every 2-3 hours.
• Exercise: Calf pumps while seated (toe taps).
• Compression: Flight socks (Class 1) if high risk.
• Meds: No evidence for aspirin. If history of DVT, LMWH shot before flight is sometimes used (Seek advice).
• Emergency: Call 999/911 if you get sudden shortness of breath or chest pain.

Support Groups

• Thrombosis UK: Patient support and information.
• Anticoagulation Europe: Advice on warfarin/DOACs.
• NBCA (National Blood Clot Alliance): US-based resources.

Patient Guide: How to Inject LMWH (Clexane)

If you need injections.

1. Wash Hands: Clean area (stomach, away from belly button).
2. Pinch: Grab a fold of fat (keep pinching!).
3. Dart: Inject needle straight in (90 degrees).
4. Push: Plunger down fully.
5. Wait: Count to 10.
6. Out: Remove needle. Release pinch.
7. Don't Rub: Rubbing causes bruising.

Key Learning Points (The Pearls)

• Treat the Patient: If clinical suspicion is high but Ultrasound is negative -> Repeat the scan in 1 week. It might be a small calf DVT growing into the popliteal.
• D-dimer Trap: Do NOT do a D-dimer in high-risk patients (likely positive anyway) or post-op patients (always positive). It is only useful to exclude DVT in low risk.
• The "Cancer Search": Unprovoked DVT warrants an age-appropriate malignancy screen (CXR, Breast Check, PSA, Stowool, Urinalysis). Do not do a "blind CT Pan-scan".
• Isolated Calf DVT: To treat or not? If symptomatic/severe, treat. If minor, serial ultrasound surveillance to check for propagation.

Reviewer's Note

Dr. Sarah Miller, Consultant Haematologist: "The biggest mistake I see is stopping anticoagulation too early in unprovoked DVT. The risk of recurrence is highest in the first year. If in doubt, continue."

Alternative Therapies (Evidence Check)

• Aspirin:
  • Verdict: Weak. Reduced recurrence by only 30% in INSPIRE trial compared to placebo. DOACs reduce it by 80-90%. Not a substitute for DVT treatment.
• Herbal Remedies:
  • Gingko/Garlic: Mild blood thinning effect. Dangerous if combined with Warfarin.
• Leeches (Hirudotherapy):
  • History: Hirudin is an anticoagulant saliva.
  • Modern Use: Only used in plastic surgery flap salvage (venous congestion), not for DVT.

History of the Procedure (Warfarin)

• 1920s: Cows in Wisconsin died after eating mouldy sweet clover (Haemorrhagic disease).
• 1939: Karl Link isolated "Dicoumarol".
• 1948: Licensed as "Warfarin" (Wisconsin Alumni Research Foundation).
• 1954: Approved for humans (famously treated Eisenhower).