Editor's Note: This article was submitted and accepted for the recent special issue on venous disease but was inadvertently omitted from the issue.
ArticleVenous thromboembolism: An overview
Section snippets
What is venous thromboembolism?
DVT
The lower extremities are the most common site for a DVT, but other affected locations may include the upper extremities, the mesenteric and pelvic veins, as well as the cerebral veins. A proximal lower extremity DVT (defined as occurring in the popliteal vein and above) is linked to an estimated 50% risk of PE if not treated; approximately 20%-25% of calf vein thrombus propagate (in the absence of treatment) to involve the popliteal vein or above (Figure 1). Approximately 10% of all DVT cases
PE
PE resulting from lower extremity DVT have the potential to lead to a number of physiologic changes secondary to obstruction of the pulmonary arteries (Figure 2). These changes include increased respiratory rate and hyperventilation, impairment of gas exchange owing to impaired perfusion, intrapulmonary shunting leading to hypoxemia, atelectasis, and vasoconstriction resulting from the release of inflammatory mediators (serotonin and thromboxane). In hemodynamically challenged patients, acutely
Prevalence
VTE is the third most common cardiovascular illness after acute coronary syndrome and stroke.8 The exact incidence of VTE is unknown; it is believed that there are approximately 1 million cases in the United States each year, many of which represent recurrent disease.9 Nearly two-thirds of all VTE events result from hospitalization and approximately 300,000 of these patients die.10
PE is the third most common cause of hospital-related death and is also the most common preventable cause of
United States statistics
The incidence of PE in the United States is estimated to be 1 case per 1,000 people per year.15 Studies from 2008 suggest that the increasing use of CT for assessing patients with possible PE has led to an increase in the reported incidence of PE.16, 17
From 1979 to 1998, the age-adjusted death rate for PE in the United States decreased from 191 to 94 deaths per million population.15 Regional studies covering the years after 1998 found either a slight decrease in the incidence of mortality or no
Predisposing factors
The pathophysiology of DVT was described by Virchow in 1846 as coming from a triad of possible changes in the venous system (Figure 3). The triad includes changes in the constituency of blood (hypercoagulability), changes in the vessel wall (injury), and changes in the pattern of blood flow (venous stasis).21 These physiologic changes can occur as a result of pathology, therapies, and treatments. Injury to the vessel wall may occur from trauma, surgery, or invasive treatments. Patients on bed
Venous stasis
Venous stasis leads to accumulation of platelets and thrombin in veins. Increased viscosity may occur owing to polycythemia and dehydration, immobility, increased venous pressure in cardiac failure, or compression of a vein by a tumor.
Hypercoagulable states
The complex and delicate balance between coagulation and anticoagulation is altered by many diseases, by obesity, or by trauma. It can also occur after surgery. Concomitant hypercoagulability may be present in disease states where prolonged venous stasis or injury to veins occurs.
Hypercoagulable state
A hypercoagulable state may be acquired or congenital. Factor V Leiden mutation causing resistance to activated protein C is the most common risk factor. Factor V Leiden mutation is present in ≤5% of the normal population and is the most common cause of familial thromboembolism. Primary or acquired deficiencies in protein C, protein S, and antithrombin III are other risk factors. The deficiency of these natural anticoagulants is responsible for 10% of venous thrombosis in younger people.
Immobilization
Immobilization leads to local venous stasis by accumulation of clotting factors and fibrin, resulting in thrombus formation. The risk of PE increases with prolonged bed rest or immobilization of a limb in a cast. In the Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) study, immobilization (usually because of surgery) was the risk factor most commonly found in patients with PE.
Surgery and trauma
A prospective study by Geerts et al23 indicated that major trauma was associated with a 58% incidence of DVT in the lower extremities and an 18% incidence in proximal veins. Surgical and accidental traumas predispose patients to VTE by activating clotting factors and causing immobility. PE may account for 15% of all postoperative deaths. Leg amputations and hip, pelvic, and spinal surgery are associated with the highest risk.23 Fractures of the femur and tibia are associated with the highest
Pregnancy
The incidence of thromboembolic disease in pregnancy has been reported to range from 1 case in 200 deliveries to 1 case in 1,400 deliveries (see Epidemiology). Fatal events are rare, with 1-2 cases occurring per 100,000 pregnancies.
Oral contraceptives and estrogen replacement
Estrogen-containing birth control pills have increased the occurrence of VTE in healthy women. The risk is proportional to the estrogen content and is increased in postmenopausal women on hormonal replacement therapy. The relative risk is 3-fold, but the absolute risk is 20-30 cases per 100,000 persons per year.23
Malignancy
Malignancy has been identified in 17% of patients with VTE. Pulmonary emboli have been reported to occur in association with solid tumors, leukemias, and lymphomas. This is probably independent of the indwelling catheters often used in such patients.24 Neoplasms most commonly associated with PE, in descending order of frequency, are pancreatic carcinoma, bronchogenic carcinoma, and carcinomas of the genitourinary tract, colon, stomach, and breast.24
Conclusion
Although VTE is among the most common preventable causes of death among hospitalized patients in the United States, it unfortunately is often overlooked as a major public health problem and viewed more as a complication of hospitalization for another illness, rather than as a specific disease entity. As vascular nurses, we can continue to educate others so that we can continue to increase the awareness of this potentially life-threatening disease.
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2021, Journal of Interventional MedicineCitation Excerpt :VTE is a name given to a group of coagulation disorders, which comprise deep vein thrombosis and pulmonary embolism (PE). Deep vein thrombosis is a phenomenon of the formation of blood clots in the deep veins of the lower limbs, but may also occur in other parts of the body.21,22 Venous thrombosis consists of the so-called Virchow’s triad, which comprises irregular blood flow, blood coagulation disorders, and vessel wall abnormalities.
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