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	Absence of hypotension, shock, right ventricular dysfunctionand myocardial necrosis

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

Risk factors of VTE may be categorized in to modifiable, non-modifiable, temporary and other risk factors.

Modifiable Risk Factors	Non-Modifiable Risk Factors	Temporary Risk Factors	Other Risk Factors
❑ Modifiable risk factors are reversible based upon lifestyle/behavior modification. ❑ 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.	❑ Advanced age ❑ Heart failure ❑ Thrombophilia or hypercoagulable state ❑ Polycythemia vera ❑ Factor V Leiden ❑ Prothrombin G20210A mutation ❑ Protein C deficiency ❑ Protein S deficiency ❑ Activated protein C resistance ❑ Antithrombin III deficiency ❑ Factor VIII mutation ❑ Antiphospholipid syndrome ❑ Heparin induced thrombocytopenia ❑ Nephrotic syndrome ❑ Paroxysmal nocturnal hemoglobinuria	❑ Advanced age ❑ Pregnancy and the peri-partum period ❑ Active cancer ❑ Central venous catheter	❑ Advanced age ❑ Other possible factors associated with VTE include: ❑ Nutrition low in fish ❑ Psychological stress ❑ Cardiovascular risk factors such as diabetes and hypercholesterolemia

Prevention

Risk Assessment

The following scoring systems can be used to assess the risk of VTE, based on risk factors:

Padua Prediction Score for VTE

Shown below is a table depicting Padua predictive score for VTE among hospitalized medical patients. The interpretation of the score is as follows:

• Score≥ 4: High risk for VTE
• Score< 4: Low risk for VTE

Variable	Score
Active cancer	3
Previous VTE	3
Decreased mobility	3
Thrombophilia	3
Previous trauma or surgery within that last month	2
Age≥ 70	1
Heart and/or respiratory failure	1
Ischemic stroke or acute myocardial infarction	1
Acute rheumatologic disorder and/or acute infection	1
Obesity	1
Hormonal therapy	1

IMPROVE Predictive Score for VTE

Calculation of the IMPROVE Predictive Score

Variable	Score
Prior episode of VTE	3
Thrombophilia	3
Malignancy	1
Age more than 60 years	1

Interpretation of the IMPROVE Predictive Score

Score	Predicted VTE risk through 3 months
0	0.5%
1	1.0%
2	1.7%
3	3.1%
4	5.4%
5-8	11%