From the Guidelines
A second deep vein thrombosis (DVT) can occur due to several factors, with the most significant being inadequate anticoagulation therapy after the first DVT, as patients with unprovoked VTE have the highest risk for recurrent VTE if anticoagulation is discontinued after the primary treatment phase, with a risk estimated to be as high as 10% by 1 year and up to 30% by 5 to 10 years 1.
Causes of Second DVT
The causes of a second DVT can be multifactorial, including:
- Inadequate anticoagulation therapy after the first DVT
- Underlying conditions that increase clotting risk, such as:
- Inherited thrombophilias (Factor V Leiden, Protein C or S deficiency)
- Active cancer
- Prolonged immobility
- Recent surgery
- Obesity
- Hormone therapy
- Presence of May-Thurner syndrome (compression of the left iliac vein)
- Antiphospholipid syndrome
Risk Factors for Recurrence
Patients who have experienced one episode of VTE are at increased risk for suffering a recurrent thrombotic event, with a recurrence rate of approximately 20% within 5 years and 30% within 10 years in the absence of continued anticoagulant medication 1.
Management of Second DVT
Proper management of a second DVT typically involves longer-duration or even indefinite anticoagulation therapy, with the specific medication and duration determined by the underlying cause and individual risk factors, as the damaged vein valves from the first DVT create areas of disturbed blood flow, making these sites prone to new clot formation even years after the initial event. The American Society of Hematology guideline panel recommends continuing antithrombotic therapy indefinitely after completion of primary treatment for patients with unprovoked VTE, based on moderate certainty in the evidence of effects 1.
From the Research
Causes of Second DVT
The causes of a second Deep Vein Thrombosis (DVT) can be multifactorial. Some of the key factors include:
- Vessel wall damage, stasis or low flow, and hypercoagulability, which favor clot formation by disrupting the balance of the opposing coagulative and fibrinolytic systems 2
- Acquired risk factors such as hip fracture, pregnancy, and immobility, which can trigger DVT when combined with hereditary risk factors like thrombophilias 3
- Alteration of venous blood flow, which produces endothelial activation, favoring the adhesion of platelets and leukocytes, and contributing to the activation of coagulation 3
- Inherited thrombophilia gene mutations, such as Factor V Leiden and Prothrombin Factor II G20210A, which can increase the risk of VTE in cancer patients 4
- Non-O blood types, which have been associated with a higher risk of VTE in cancer patients 4
Risk Factors for Recurrent VTE
Some of the key risk factors for recurrent VTE include:
- Inadequate anticoagulant response, which can lead to a higher frequency of recurrent VTE 2
- Active cancer, which can increase the risk of recurrent VTE 5
- History of previous VTE, which can increase the risk of recurrent VTE 2
- Presence of hereditary or acquired thrombophilias, which can increase the risk of recurrent VTE 3, 4