Venous Thromboembolism (VTE): Causes and Risk Factors
Overview
VTE ประกอบด้วย:
- Deep
vein thrombosis (DVT)
- Pulmonary
embolism (PE)
สาเหตุของ VTE มักเป็น:
- multifactorial
- acquired
+ inherited risk factors ร่วมกัน
พบ risk factor ได้
>80% ของผู้ป่วย
Virchow Triad
Pathophysiology หลักของ thrombosis:
Virchow triad = stasis + endothelial injury + hypercoagulability
1. Venous stasis
เช่น:
- immobilization
- hospitalization
- HF
- prolonged
travel
- paralysis
2. Endothelial injury
เช่น:
- surgery
- trauma
- central
venous catheter
- vascular
injury
3. Hypercoagulability
เช่น:
- cancer
- pregnancy
- APS
- inherited
thrombophilia
- estrogen
therapy
Major acquired risk factors
Previous VTE
Major risk factor for recurrence
Pattern:
- previous
PE → recurrent PE more
likely
- previous
DVT → recurrent DVT
more likely
Active malignancy
หนึ่งใน strongest acquired risk factors
VTE พบประมาณ:
Cancer-associated VTE approx 15%
High-risk cancers:
- pancreatic
- metastatic
disease
- MPNs
(myeloproliferative neoplasms)
Additional risks:
- chemotherapy
- surgery
- hospitalization
- central
lines/PICC
Surgery
High-risk surgery:
- orthopedic
- vascular
- pelvic
- neurosurgery
- cancer
surgery
Trauma
Especially:
- spinal
cord injury
- major
trauma
- prolonged
immobilization
Immobilization / hospitalization
Examples:
- ICU
admission
- stroke
- MI
- HF
- leg
injury
Long travel ("economy class syndrome")
Risk increase:
- prolonged
immobility
- dehydration
- venous
stasis
Older age
Risk increases markedly after age 65
Incidence rises exponentially with age
Pregnancy
Risk approximately:
Pregnancy VTE risk approx 4 times
เพิ่มมากขึ้นหากมี inherited
thrombophilia
Cardiovascular conditions
Heart failure
Particularly:
- right
HF
- hospitalized
HF
Mechanisms:
- stasis
- inflammation
- hypercoagulability
Atherosclerotic disease
MI/stroke เพิ่ม risk VTE โดยเฉพาะช่วงแรก
Obesity
Risk increase:
Obesity-associated VTE risk approx 2-3 times
เพิ่มมากขึ้นหากร่วมกับ:
- factor
V Leiden
- estrogen
- prolonged
travel
Smoking
Relative risk:
~1.3–3.3×
Dose-dependent relationship
Hormonal therapy
Estrogen-containing contraceptives
Riskสูงสุด:
- first
6–12 months
Hormone replacement therapy
Oral estrogen:
- increases
VTE risk
Transdermal estrogen:
- lower
risk
Tamoxifen
เพิ่ม VTE risk โดยเฉพาะเมื่อ:
- cancer
- surgery
- fracture
Antiphospholipid syndrome (APS)
ทำให้:
- venous
thrombosis
- arterial
thrombosis
- recurrent
pregnancy loss
Kidney disease
High-risk conditions:
- nephrotic
syndrome
- ESRD
- CKD
- kidney
transplant
Hematologic disorders
HIT
Major cause of venous + arterial thrombosis
Myeloproliferative neoplasms (MPNs)
Examples:
- polycythemia
vera
- essential
thrombocythemia
Associated thrombosis:
- DVT
- PE
- Budd-Chiari
syndrome
- arterial
thrombosis
Hyperviscosity syndromes
Examples:
- Waldenström
macroglobulinemia
- multiple
myeloma
PNH
Thrombosis often:
- intraabdominal
veins
- cerebral
veins
Other associated conditions
- inflammatory
bowel disease
- chronic
liver disease
- COVID-19
- rheumatoid
arthritis
- tuberculosis
- sepsis
- obstructive
sleep apnea
- psoriasis
- asthma
- IV
drug use
- VEXAS
syndrome
Inherited thrombophilia
Most common
Factor V Leiden
Risk:
Factor V Leiden risk approx 4-5 times
Prothrombin G20210A mutation
Risk:
Prothrombin mutation risk approx 3-4 times
High-risk inherited defects
Antithrombin deficiency
Risk:
Antithrombin deficiency risk approx 16 times
Protein C deficiency
~7×
Protein S deficiency
~5×
Important principle
Inherited thrombophilia มักต้องมี acquired
trigger ร่วมด้วย
Anatomic risk factors
May-Thurner syndrome
Compression:
- left
common iliac vein
โดย - right
common iliac artery
สัมพันธ์กับ:
- left
iliofemoral DVT
Inferior vena cava abnormalities
Examples:
- IVC
agenesis
- hypoplasia
- malformations
Clues:
- young
patient
- bilateral/recurrent
iliofemoral DVT
Varicose veins
สัมพันธ์กับ:
- increased
DVT risk
- increased
PE risk
Upper extremity thrombosis
Major risk:
- central
venous catheter/PICC
Spontaneous cases:
- thoracic
outlet compression
(Paget-Schroetter syndrome)
Laboratory-associated thrombotic factors
Associated with increased VTE risk:
- elevated
factor VIII
- elevated
factor IX/XI
- elevated
fibrinogen
- elevated
VWF
- reduced
fibrinolysis
Non-O blood group
Blood group:
- A/B/AB
Higher VTE risk than O blood group
Clinical pearls
- VTE มักเกิดจากหลาย risk factors ร่วมกัน
- Virchow
triad เป็น core mechanism
- malignancy
เป็น acquired risk factor สำคัญ
- previous
VTE = strongest predictor of recurrence
- immobilization
+ illness dramatically increase risk
- obesity
+ smoking + estrogen synergistically increase risk
- inherited
thrombophilia alone มักไม่พอ ต้องมี trigger ร่วม
- left
iliofemoral DVT →
think May-Thurner syndrome
- young
recurrent bilateral DVT →
think IVC anomaly/thrombophilia
- APS และ cancer มี recurrence risk สูง
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