Venous Thromboembolism

Defined

Venous thromboembolism (VTE) refers to all forms of pathologic thrombosis occurring on the venous side of the circulation, the most common of which is deep venous thrombosis (DVT) of the lower extremities. The most life-threatening manifestation of VTE is embolization of venous thrombi to the pulmonary circulation, pulmonary embolism (PE). The occurrence of VTE is generally triggered by a confluence of environmental and constitutional risk factors.



VTE and its complications are a common cause of morbidity and mortality in the United States.

It is estimated that there is an Average US Annual Incidence Rate of:
450,000 cases of DVT
350,000 cases of Non-Fatal PE
200,000 cases of Fatal PE

Risk Factors

Immobility -> venous stasis -> DVT
Surgery within last month
Hospitalization presently or last month
Immobilization >48 hours or during long flights, “Economy Class” Syndrome
Age > 40
Smoking
Obesity
Malignancy
1st Degree Relative History
Drugs - OCPs/HRTs or Erythropoietin
Thrombophilias
Women have an increased risk during pregnancy & 6 Mos postnatal period.

Multiple Risk Factors

Many patients with an episode of VTE have more than one acquired risk factor for thrombosis. This was shown in a population-based study of the incidence of VTE in residents of Worcester, MA during 1999. The six most prevalent preexisting medical characteristics of patients in this study are graphed below.

The Estrogen Risk

100,000 women divided by age with risk factors of Smoking and HTN while Simultaneously Using OCPs. It was found that those in each age group with HTN had nearly twice the incidence of MI's and Ischemic CVA's than those who had combination risk of using OCP's and were smokers compared to control groups.

100,000 women divided by age, use of High Estrogen (estrogen only) vs. Low Dose and compared to Pregnancy at the same age. It was found that pregnancy is still the higher risk factor for VTE after the age of 35 and that Unopposed Estrogen doubles the risk of VTE compared to Low Estrogen in all age groups.
High Dose Brand Names: Desogen, Kariva, Ortho-Cept, Mircette

Cancer Risk for VTE

Cancer alone is associated with a 4-fold risk of thrombosis, whereas chemotherapy increased the risk 6.5-fold.

Combining these estimates yields an approximate annual incidence of VTE of 1 in 200 in a population of cancer patients (15).

In a retrospective study of over 63,000 patients admitted to hospitals from 1977 through 1992 for a diagnosis of VTE, 18% had received a diagnosis of cancer (other than non-melanoma skin cancer) prior to the thromboembolic event.

The five most common sites for cancer diagnosed at the time of VTE included:

Surgery Risk of VTE or PE

*Thromboprophylaxis significantly reduces the incidence of symptomatic DVT or pulmonary embolism in the immediate postoperative period. However, there is a continued risk of DVT following hospital discharge in those who have had total knee or hip arthroplasty and the usual 7 to 10 days of thromboprophylaxis.

The Family History Risk

In a study from Leiden University Medical Center, Netherlands, researchers looked at records and family histories of 3,764 people, 1,605 who had had DVT and 2,159 who had not.

Results showed that in people with no RF, having a 1st-degree relative with DVT increased the odds of having a first episode of DVT by 2.5 times.

This was about the same as the increase in odds (2.3 times) caused by genetic risk factors in people with no family history or environmental risk factors.

Wells Criteria for Clinical Diagnosis

Treatment of VTE

Unfractionated Heparin with Loading dose 80U/kg, followed by maintenance dose of 18U/kg/hr, (monitor with APTT)

Low Molecular Weight Heparin: Lovenox at 1mg/kg q12hrs. or Fragmin 200U/kg daily, no loading doses necessary.

For long term Anticoagulation, pts. should start Warfarin approx. 5mg QHS, generally within the 1st 24hrs and bridge with UFH or LMWH. Titrate warfarin until therapeutic (INR 2-3). Long-term anticoagulation is generally continued for 6 months.

How Well Are We Treating & Diagnosing DVTs & PEs?

A Meta-Analysis conducted by The Johns Hopkins University Evidence-based Practice Center identified 64 original studies and 29 systematic reviews that addressed this question.