Venous thromboembolism

Venous thromboembolism Microchapters
Patient Information Deep vein thrombosis Pulmonary embolism
Overview
Classification
Epidemiology
Risk Factors
Diagnosis
Treatment Deep Vein Thrombosis Pulmonary Embolism
Prevention

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]:Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [2]

Classification

Venous thromboembolism (VTE) may be classified into:

• Deep vein thrombosis (DVT)
• Pulmonary embolism (PE)

The following table further classifies DVT and PE:

Classification of Venous thromboembolism
Clinical diagnosis		Sub-classification	Comments
Deep vein thrombosis		Upper extremity	Uncommon and accounts for 1-5 % of all DVT Most likely due to: Central venous catheter Cardiac pacemaker Implantable cardioverter defibrillator Effort thrombosis (Paget–Schroetter disease) Cancer
		Lower extremity	Proximal: Popliteal veins Femoral veins Iliac veins Isolated distal: Calf veins (Peroneal, soleal, posterior tibial, gastrocnemial, soleal, gastrocnemial, peroneal, posterior tibial)
Pulmonary embolism (PE)		Massive PE (High risk)	Sustained hypotension (systolic blood pressure <90 mm Hg), not due to arrhythmia, hypovolemia, sepsis, or left ventricular dysfunction, and either lasting for at least 15 minutes or necessitating the administration of inotropes OR Pulselessness OR Persistent profound bradycardia (heart rate < 40 bpm) plus findings of shock
		Sub-massive PE (Intermediate risk PE)	Right ventricular dysfunction OR myocardial necrosis AND Absence of systemic hypotension (systolic blood pressure >90 mm Hg)
Low risk PE	>10 mm diameter

Risk Factors

Shown below is a list of predisposing factors for VTE. The risk factors are classified as moderate or weak depending on how strongly they predispose for a VTE.

Moderate risk factors	Weak risk factors
❑ Chemotherapy ❑ Chronic heart failure ❑ Respiratory failure ❑ Hormone replacement therapy ❑ Cancer ❑ Oral contraceptive pills ❑ Stroke ❑ Pregnancy ❑ Postpartum ❑ Prior history of VTE ❑ Thrombophilia	❑ Advanced age ❑ Laparoscopic surgery ❑ Prepartum ❑ Obesity ❑ Varicose veins

The risk factors of VTE can be further classified into modifiable, non-modifiable and temporary.

Modifiable Risk Factors

Modifiable risk factors are reversible based upon lifestyle/behavior modification.

• Obesity: Obesity is defined as a body-mass index (BMI) above 30 kg/m2.

• Smoking: Smoking significantly increases the risk of DVT, particularly among women who are taking oral contraceptive pills as well as among obese people.

• Use of oral contraceptives

• Hyperhomocysteinemia: Hyperhomocysteinemia can be reduced with vitamin B supplementation.

Non-Modifiable Risk Factors

• Advanced age
• Heart failure
• Thrombophilia or hypercoagulable state
  • Factor V Leiden
  • Prothrombin G20210A mutation
  • Protein C deficiency
  • Protein S deficiency
  • Antithrombin deficiency
  • Activated protein C resistance
  • Antithrombin III deficiency
  • Factor VIII mutation
  • Antiphospholipid syndrome
  • Heparin induced thrombocytopenia
  • Nephrotic syndrome
  • Paroxysmal nocturnal hemoglobinuria
• Polycythemia vera

Temporary Risk Factors

• Pregnancy and the peri-partum period
• Active cancer
• Central venous catheter

Other Possible Risk Factors

Other possible factors associated with VTE include:

• Nutrition low in fish, fruits, and vegetables
• Psychological stress
• Cardiovascular risk factors such as diabetes and hypercholesterolemia
• Acute medical illness
• Drug abuse (intravenous drugs)
• Sickle cell disease
• Inflammatory bowel disease
• Antipsychotic drugs
• Thrombocytosis
• Varicose veins