Chapter 90: Venous Thromboembolism

INTRODUCTION

Venous thromboembolism (deep venous thrombosis and/or pulmonary embolism) is a common disorder, which is estimated to affect 900,000 patients each year in the United States.
Pulmonary embolism may cause sudden or abrupt death, underscoring the importance of prevention as the critical strategy for reducing death from pulmonary embolism.
Of the estimated 600,000 cases of nonfatal venous thromboembolism in the United States each year, approximately 60 percent present clinically as deep venous thrombosis and 40 percent present as pulmonary embolism.
Most clinically important pulmonary emboli arise from proximal deep venous thrombosis (thrombosis involving the popliteal, femoral, or iliac veins). Upper extremity deep venous thrombosis also may lead to clinically important pulmonary embolism. Other less common sources of pulmonary embolism include the deep pelvic veins, renal veins, inferior vena cava, right side of the heart, and axillary veins.
Acquired and inherited risk factors for venous thromboembolism have been identified (for inherited thrombophilia see Chap. 89). The risk of thromboembolism increases when more than one predisposing factor is present.

The clinical features of deep venous thrombosis and pulmonary embolism are nonspecific.

The clinical features of venous thrombosis include leg pain, tenderness, and asymmetrical swelling, a palpable cord representing a thrombosed vessel, discoloration, venous distention, prominence of the superficial veins, and cyanosis.
In exceptional cases, patients may present with phlegmasia cerulea dolens (occlusion of the whole venous circulation, extreme swelling of the leg, and compromised arterial flow).
In 50 to 85 percent of patients, the clinical suspicion of deep venous thrombosis is not confirmed by objective testing. Conversely, patients with florid pain and swelling, suggesting extensive deep venous thrombosis, may have negative results by objective testing. Patients with minor symptoms and signs may have extensive deep venous thrombi.
Although the clinical diagnosis is nonspecific, prospective studies have established that patients can be categorized as low, moderate, or high probability for deep venous thrombosis using clinical prediction rules that incorporates signs, symptoms, and risk factors.

The clinical features of acute pulmonary embolism include the following symptoms and signs that may overlap:

— Transient dyspnea and tachypnea in the absence of other clinical features.

— Pleuritic chest pain, cough, hemoptysis, pleural effusion, and pulmonary infiltrates noted on chest radiogram caused by pulmonary infarction or congestive atelectasis (also known as ischemic pneumonitis or incomplete infarction).

— Severe dyspnea and tachypnea and right-side heart failure.

— Cardiovascular collapse with hypotension, syncope, and coma (usually associated with massive pulmonary embolism).

— Several less common and nonspecific clinical presentations, including unexplained tachycardia or arrhythmia, resistant cardiac failure, wheezing, cough, fever, anxiety/apprehension, and confusion.
All of these clinical features are nonspecific and can be caused by a variety of cardiorespiratory disorders.
Patients can be assigned to categories of pretest probability using implicit clinical judgment, or clinical decision rules.