Venous Thromboembolism



Venous Thromboembolism


Stephanie M. Madonis

J. Stephen Jenkins



INTRODUCTION

Venous thromboembolic (VTE) disease is a condition in which a thrombus forms in the venous circulation and includes both deep vein thrombosis (DVT) and pulmonary embolism (PE). Although the true incidence of VTE is unknown, according to the U.S. Centers for Disease Control and Prevention, it is estimated at 900,000 individuals in the United States each year.1 This disease burden accrues substantial health care costs and leads to significant morbidity and mortality. The purpose of this chapter is to describe the various clinical features and presentations of VTE with a particular focus on DVT. An overview regarding the different treatment options in addition to the evaluation and management of long-term sequelae from DVT is also provided.




NOMENCLATURE

Oftentimes, DVT is categorized as having been (1) provoked by an identifiable patient-related or environmental risk factor or (2) unprovoked with no identifiable provoking event evident. This distinction is made because of important prognostic and management implications. Current guidelines advocate for at least 3 months of anticoagulation for provoked DVTs, whereas long-term anticoagulation is recommended for patients with unprovoked events because of a high risk of recurrence.

Provoking risk factors can be further subdivided into transient or persistent. Transient risk factors are those that resolve after they have “provoked” a DVT, and include events such as recent surgery, trauma, confinement to bed or prolonged immobilization, use of oral contraceptives or hormone replacement therapy, and pregnancy. Potential permanent or persistent risk factors include malignancy, hereditary thrombophilia, inflammatory bowel disease, collagen vascular disease, chronic renal disease, congestive heart failure, obesity, and tobacco use disorder.

It is approximated that 25% to 50% of DVT cases have no identifiable predisposing risk factor or trigger, and are therefore, classified as being unprovoked.3


ANATOMIC CONSIDERATIONS

Most DVTs arise in the deep venous system of the lower extremities or pelvis, but they can also affect other venous parts of the body, including the upper extremities, brain, liver, intestines, or kidney(s). Although upper extremity DVTs are far less common than are lower extremity DVTs, they still account for approximately 4% to 10% of all DVT cases.4 Upper extremity DVTs may arise in the internal jugular, subclavian, axillary, or brachial veins, and are often associated with, or related to, indwelling central venous catheters, pacemaker or defibrillator leads, and thoracic outlet syndrome.

Lower extremity DVTs have traditionally been categorized by the anatomic location of thrombus as either proximal or distal (Figure 84.1). Proximal DVT is routinely used to describe thrombus that is located in the inferior vena cava (IVC) and iliac, femoral, or popliteal veins. Distal DVT is used to describe thrombus confined to the calf veins, which includes the peroneal, posterior, and anterior tibial veins, and muscular calf veins (ie, the soleal or gastrocnemius). Compared to proximal DVTs, distal DVTs are not as common and oftentimes do not require treatment or intervention.5

Although this anatomic subdivision is appropriate for clinical purposes, a new anatomic division at the level of the iliofemoral veins is being widely adopted, and is particularly useful when it comes to risk stratification of patients
with lower extremity DVTs that may benefit from early invasive catheter-based treatment. Studies have demonstrated that proximal DVTs involving the common femoral vein and/or iliac veins portend worse prognosis and carry higher risk for adverse outcomes when compared to proximal DVTs that do not involve the common femoral vein or iliac veins.6,7 Consequently, these patients with iliofemoral thrombosis are likely to benefit from invasive strategies such as catheter-directed thrombolysis (CDT) and/or mechanical or aspiration thrombectomy.8,9






The 2012 guidelines of the Society for Vascular Surgery and the American Venous Forum recognize the need for this important distinction in the diagnosis of lower extremity DVTs, with guideline 1.1 stating: “We recommend use of precise terminology to characterize the most proximal extent of venous thrombosis as involving the iliofemoral veins, with or without extension into the IVC; the femoropopliteal veins; or isolated to the calf veins in preference to simple characterization of a thrombus as proximal or distal.”10




MANAGEMENT

Algorithm 84.1 provides basic treatment for the management of patients with a new diagnosis of DVT.


Medical Approach

Systemic anticoagulation is the mainstay of therapy for patients with acute DVT. If clinical suspicion for DVT is intermediate or high, anticoagulation should be initiated while further testing is performed to confirm the diagnosis, particularly if no contraindication(s) to anticoagulation exist.

Several anticoagulation options are available (Table 84.2), and agent selection largely depends on patient characteristics as well as on patient and physician preference.

Warfarin, which disrupts vitamin K metabolism, thereby inhibiting clotting factors II, VII, IX, and X, was the most
widely used oral anticoagulant of choice for well over 50 years. The international normalized ratio (INR) is used to monitor warfarin concentrations. An INR value between 2.0 and 3.0 is considered to be “therapeutic range” for most clinical situations, including treatment of acute DVT. When warfarin is chosen as the oral agent, treatment must be initiated and overlapped with a parenteral drug until the INR is therapeutic (ie, >2) for two consecutive INR values.







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May 8, 2022 | Posted by in CARDIOLOGY | Comments Off on Venous Thromboembolism
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