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Fast Five Quiz: Venous Thromboembolism
Zab Mosenifar, MD
December 13, 2018
Venous thromboembolism (VTE) encompasses two interrelated conditions that are part of the same spectrum: deep vein thrombosis (DVT) and pulmonary embolism (PE). PE and DVT can occur in the setting of disease processes, after hospitalization for serious illness, or after major surgery.
Thromboembolic disease is the third most common acute cardiovascular disease, after cardiac ischemic syndromes and stroke. The spectrum of disease ranges from clinically unsuspected to clinically unimportant to massive embolism causing death, and indeed DVT and PE frequently remain undiagnosed because they may not be suspected clinically. Untreated acute proximal DVT causes clinical PE in 33%-50% of patients. Untreated PE is often recurrent over days to weeks and can either improve spontaneously or cause death.
Are you familiar with key aspects of VTE, including best practices for diagnosis and treatment? Refresh and test your knowledge with this short quiz.
Q1. Which of the following is accurate regarding the etiology and epidemiology of VTE? 有关VTE的病因和流行病学，以下哪种说法是正确的？
A1: The incidence of DVT is higher among patients who have undergone knee surgery 接受膝关节手术的患者DVT的发生率较高
Surgical factors are related to procedure type and procedure duration. Among patients who have undergone hip surgery, 50% have a proximal DVT on the same side as the hip surgery. This is thought to be due to a twisting of the femoral vein during total hip replacement. The incidence of DVT is higher in patients who have undergone knee surgery.
Patient-related risk factors for VTE include age older than 40 years (risk doubles with each decade in persons older than 40 years), obesity, varicose veins, the use of estrogen in pharmacologic doses (ie, oral contraceptives or hormone replacement therapy), and immobility.
According to the Centers for Disease Control and Prevention (CDC), the estimated average annual number of hospitalizations in which VTE was diagnosed in 2007-2009 was 250,973 in men and 296,623 in women.
For more on VTE, read here
Q2: Which of the following is accurate regarding clinical signs of PE? 有关PE临床体征的哪个说法是正确的？
A2: The second heart sound may be accentuated 第二心音可能增强
Some patients have signs of DVT, lower-extremity swelling, and tenderness and warmth to touch. Clinical signs of PE also include the following:
- Tachypnea (respiratory rate > 18 breaths/min) is the most common sign of PE
- Tachycardia often is present
- The second heart sound can be accentuated
- Fever may be present
- Lung examination findings frequently are normal
- Cyanosis may be present
In the appropriate clinical setting, when shortness of breath, hypoxemia, and tachycardia are present, there should be a high clinical suspicion of PE until it is ruled out.
For more information on the presentation of VTE, read here.
Q3: Which of the following is accurate regarding D-dimer testing in patients with suspected VTE? 有关疑似VTE患者的D-二聚体监测，以下哪种说法是正确的？
A3：The value of D-dimer measurement in suspected VTE is more in its negative predictive value 对于疑似VTE患者，测定D-二聚体的意义在于其阴性预期值
Enzyme-linked immunosorbent assay can be used to quantify the presence of D-dimer, which is a specific degradation product of cross-linked fibrin. This is an important marker of the activation of fibrinolysis. It can be elevated in pneumonia, cancer, sepsis, and surgery.
A plasma D-dimer level > 500 ng/mL has been shown to have a sensitivity of 97% and a specificity of 45% for VTE. The value of D-dimer is in its negative predictive value. A plasma D-dimer level < 500 ng/mL in those with low pretest probability essentially excludes PE.
This study is less helpful in older patients, in that the D-dimer level tends to increase with age. In a study by Righini and colleagues, an age-adjusted D-dimer cutoff combined with a probability assessment was shown to rule out the diagnosis of PE in emergency department patients with suspected PE and was associated with a low likelihood of subsequent symptomatic VTE, thus increasing the proportion of patients in whom the diagnosis could be excluded.
For more on laboratory studies in VTE, read here.
Q4: Which of the following is accurate regarding imaging studies in patients with suspected VTE? 有关疑似VTE患者的影像学检查，以下哪种说法是正确的？
A4: CT pulmonary angiography is most commonly the preferred imaging method for the diagnosis of acute PE CT肺血管造影是诊断急性PE最常采用的影像学检查
CT pulmonary angiography is generally the preferred imaging method for the diagnosis of acute PE in patients with a high clinical probability or low/intermediate probability and elevated D-dimer levels.
Chest radiographic findings most often are normal. Radiographs may, however, reveal an enlarged right descending pulmonary artery, decreased pulmonary vascularity (Westermark sign), a wedge-shaped infiltrate, or elevation of the hemidiaphragm (Hampton hump). If infarction occurs, a pleural effusion may be present.
Impedance plethysmography is a noninvasive method of assessment. Sensitivity and specificity have been reported to be between 92% and 95%. However, it is of limited value when DVT is asymptomatic or distal or when findings are inconclusive.
Ventilation-perfusion scanning is a common screening technique. This modality provides a probability estimate for PE by evaluation of the size and number of defects in the perfusion of the lung compared with the areas of ventilation. The diagnosis of PE is easily made with this modality when the probability estimate is high for PE. With a normal scan finding, the possibility of PE is excluded. However, the test results are nondiagnostic in about 66% of cases.
For more on the use of imaging studies in VTE, read here.
Q5: Which of the following is accurate regarding the use of heparin in patients with VTE? 有关VTE患者使用肝素的以下哪种说法是正确的？
A5: Adequacy of therapy with heparin is determined by an activated partial thromboplastin time (aPTT) of 1.5-2 times baseline 肝素充分抗凝即将aPTT维持在基线值的1.5-2倍
Heparin is the first line of therapy. It is administered by bolus dosing, followed by a continuous infusion. Adequacy of therapy is determined by an aPTT of 1.5-2 times baseline. Progression or recurrence of thromboembolism is 15 times more likely when a therapeutic aPTT is not achieved within the first 48 hours.
Several studies have shown that LMWH, which is a fractionated heparin, is as effective as UFH in treating DVT.
In pregnancy, establishing a clear guideline for the treatment of thromboembolic disease is difficult from an evidence-based perspective. Heparin is the anticoagulant of choice, given its relative safety for the fetus.
The goal of oral anticoagulant therapy (warfarin sodium) is to achieve an international normalized ratio of 2.0-3.0. The optimum duration of treatment depends on several factors (eg, first episode or recurrent event, other underlying risk factors). A minimum of 3 months of oral therapy has been suggested after a first episode of DVT or PE.
For more on the treatment of VTE, read here.
