By Dr Ananya Mandal, MD
What is deep vein thrombosis?
Deep vein thrombosis (DVT) and pulmonary embolism (PE) is one of the most important public health problems to watch out for. These conditions are usually under-diagnosed but serious, preventable medical conditions.
The conditions occur when a blood clot forms in a deep vein. These clots usually develop in the leg, thigh, or pelvis or even in the arm. In more than one-third of people affected by DVT, these clots can travel to the lungs and cause PE. Pulmonary embolism is a life threatening condition.
How many people are affected by DVT?
Annually nearly 300,000 to 600,000 patients are affected with DVT in the United States. Of these nearly a third will have a recurrence within 10 years and one-third of people die within one month of diagnosis. Another third will have long-term complications including pain, swelling, discoloration and changes in the affected limb that may even lead to disability.
Risk factors for DVT
The risk of death and disability due to DVT and PE may be reduced by vigilance in at risk individuals, early and accurate diagnosis and management. DVT/PE affects people of all races and ages.
Some of the risk factors for DVT include:-
prolonged immobility after a surgery or major illness
long hours of immobility in air travel
Obesity and DVT/PE
Obesity is an important risk factor for DVT/PE in both men and women. According to the reports from the 2008 National Health and Nutrition Examination Survey (NHANES) 33.8% of US adults are obese (BMI ≥30 kg/m2) and 5.7% are morbidly obese (BMI ≥40 kg/m2).
Studies have shown that obese individuals have nearly twice the risk of both PE and DVT and obese patients less than 40 years have nearly a fivefold risk than those who are not obese. The risk of development of PE is nearly six fold high among women with a BMI of 35 kg/m2 or more.
DVT, oral contraceptive (OCP) use and obesity
Similarly, the combination of oral contraceptive (OCP) use and obesity together also raises the risk of DVT from 5.2 to 7.8 compared with obese women not taking OCPs and by 3.1 over non-obese users of OCPs.
Obesity and risk factors for DVT
Obesity also raises the other known risk factors for developing DVT. For example, obesity is connected to genetic mutations F5 G1691A (Factor V Leiden) and F2 G20210A (prothrombin). These are blood coagulation factors that are imbalanced in DVT and PE. Obesity doubles the risk of such imbalances.
Obesity and recurrence of DVT
Obese patients also have a risk of recurrent DVT episodes compared to non-obese individuals. Obesity leads to stasis or stagnation of blood in the veins. This also raises the risk of thrombosis and clot formation.
Obesity and blood clotting
Obesity raises and alters the levels of factors that affect coagulation and blood clotting. Obese individuals may be producing more adipokines such as leptin and adiponectin, develop insulin resistance and a chronic inflammatory state. These also increase platelet activity.
Platelets are blood cells responsible for beginning blood coagulation and clot formation.
Obesity also leads to overproduction of plasminogen activator inhibitor-1 that comes from adipocytes or fat cells and hepatocytes or liver cells. These cells are driven by increased blood levels of free fatty acids, cytokines, adipokines and relative hypoxia or lack of oxygen in adipose tissue in obesity. The plasminogen activator inhibitor-1 leads to inhibiton of clot break down or fibrinolysis promoting clot formation and raising the risk of DVT and PE.
Treatment and prevention of DVT in obese individuals
Treatment and prevention of DVT and PE in obese individuals is same as that of non obese individuals. However, early recognition and preventive strategies are important.
Heparin or its new congeners (low molecular weight heparins like Enoxaparin, Dalteparin etc.) are being used.
There are several non-pharmacological strategies for management of DVT as well. These include mechanical devices such as graduated compression stockings, venous foot pumps and intermittent pneumatic compression devices.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)
Last Updated: Apr 8, 2013