High Thrombotic Risk Patient Identification
Patients at high risk of thrombosis include those with immobility, cancer, previous thromboembolism, and specific genetic or acquired thrombophilias. 1
Stroke and Immobility-Related Risk Factors
- Patients unable to move one or both lower limbs 1
- Patients unable to mobilize independently 1
- Previous history of venous thromboembolism 1
- Dehydration 1
- Comorbidities such as cancer 1
Cancer-Related Risk Factors
- Patients with advanced disease of the brain, lung, uterus, bladder, pancreas, stomach, and kidney have the highest 1-year incidence rate of venous thromboembolism (VTE) 1
- Metastatic disease increases VTE risk 4-13 times compared to localized disease 1
- Patients receiving chemotherapy, particularly cisplatin, fluorouracil, and immunomodulatory drugs (thalidomide, lenalidomide) 1, 2
- Patients with multiple myeloma receiving immunomodulatory drugs combined with glucocorticoids (10-40% increased risk) 2
- Bevacizumab (anti-VEGF therapy) increases arterial thrombotic risk and possibly venous thrombotic risk 1, 2
Cancer Risk Assessment Models
Khorana score identifies high-risk ambulatory cancer patients based on:
- Cancer site (very high risk: stomach, pancreas; high risk: lung, lymphoma, gynecological, genitourinary; low risk: breast, colorectal, head and neck) 1
- Pre-chemotherapy platelet count ≥350 × 10^9/L 1
- Hemoglobin <10 g/dL or use of erythropoiesis-stimulating agents 1
- Leukocyte count >11 × 10^9/L 1
- BMI ≥35 kg/m^2 1
High-risk patients (score ≥3) have a 6.7% incidence of VTE 1
For multiple myeloma patients receiving immunomodulatory drugs, specific risk assessment models (SAVED or IMPEDE VTE) are recommended 1
Genetic and Acquired Thrombophilias
- Factor V Leiden mutation (most common genetic cause) 1
- Prothrombin G20210A mutation (second most common genetic cause) 1
- Antiphospholipid syndrome (most common acquired cause) 1
- Deficiencies of coagulation inhibitors (antithrombin III, protein C, or protein S) 1
- Homozygous factor V Leiden carriers have significantly higher risk than heterozygous carriers 1
Cardiovascular and Cerebrovascular Risk Factors
Patients with mechanical heart valves, especially:
Patients with non-valvular atrial fibrillation with high CHADS₂ scores (5-6) 1
Patients with suspected cardioembolic stroke mechanism 1
Patients with patent foramen ovale and cryptogenic stroke (increased paradoxical embolism risk) 1
Perioperative and Procedural Risk
- Major surgery and laparoscopic procedures with pneumoperitoneum and reverse Trendelenburg position 1
- Major cardiovascular surgery, orthopedic surgery, head and neck cancer surgery, urologic surgery 1
- Surgeries lasting ≥45 minutes 1
Special Populations
- Patients with myeloproliferative neoplasms, particularly polycythemia vera (28.6% prevalence of thrombosis) 1
- Patients with acute lymphoblastic leukemia receiving L-asparaginase (increased CNS thrombosis risk) 2
- Patients with thrombocytopenia from antiphospholipid antibodies (paradoxically higher thrombotic than bleeding risk) 3
Risk Stratification Approach
- For stroke patients: assess mobility status, previous VTE history, and comorbidities 1
- For cancer patients: use validated risk assessment models (Khorana score, SAVED, IMPEDE VTE) 1
- For surgical patients: consider procedure type, duration, and patient-specific factors 1
- For patients with atrial fibrillation: use CHADS₂ score 1
Important Caveats
- Mild to moderate thrombocytopenia (>50,000/μL) should not interfere with thrombosis risk assessment, while severe thrombocytopenia (<50,000/μL) requires individualized assessment 3
- Patients with liver cirrhosis may have bleeding abnormalities but paradoxically remain at high risk for portal and venous thromboses 3
- Aspirin treatment alone is not as effective as heparins for VTE prevention 3
- Genetic screening for thrombophilia is not recommended for primary prevention in asymptomatic individuals 1, 4