Practice Guidelines

ACEP Releases Clinical Policy on Evaluation and Management of Pulmonary Embolism

Am Fam Physician. 2003 Aug 15;68(4):759-760.

The Clinical Policies Committee and the Clinical Policies Subcommittee on Suspected Pulmonary Embolism of the American College of Emergency Physicians (ACEP) recently released a clinical policy focusing on critical issues in the evaluation and management of patients with signs and symptoms of pulmonary embolism (PE). The clinical policy was published in the February 2003 issue of Annals of Emergency Medicine. This policy is a revision of the 1995 ACEP chest pain policy as related to the initial approach to patients with signs and symptoms of PE that was published in the February 1995 issue of Annals of Emergency Medicine.

Strength of Recommendations

The authors of these guidelines provide recommendations for management of PE based on strength of evidence. Level A recommendations are generally accepted management principles that reflect a high degree of clinical certainty. Level B recommendations are management strategies that reflect a moderate clinical certainty. Level C recommendations are management strategies based on preliminary, inconclusive, or conflicting evidence or, in the absence of any published literature, based on panel consensus.

Diagnostic Usefulness of d-dimer

As a result of fibrinolysis, d-dimers are released and are an indicator of the presence of endovascular thrombus. The five major types of d-dimer assays are enzyme-linked immunosorbent assay (ELISA), latex agglutination assay, whole blood assay, turbidimetric assay, and immunofiltration assay. According to the ACEP policy, the sensitivity of the ELISA d-dimer for the diagnosis of PE is 97 percent and the specificity is 44 percent. However, ELISA assays require two to four hours to complete. Latex assays are more rapid, but produce inadequate sensitivity to eliminate PE. A whole blood assay has a pooled sensitivity of 89 percent and specificity of 59 percent for the detection of PE. It only requires five minutes to perform and reliably excludes PE when used with the Wells' scoring system for estimating pretest probability of PE (see table). The rapid ELISA and turbidimetric assays provide at least a 95 percent sensitivity for the detection of PE.

Level A recommendations: None specified.

Level B recommendations: In patients with a low pretest probability of PE, use the following tests to exclude PE:

  1. A negative quantitative d-dimer assay (turbidimetric or ELISA).

  2. A negative whole blood cell qualitative d-dimer assay in conjunction with a Wells' score of 2 or less.

Level C recommendations: In patients with a low pretest probability of PE, negative findings on a whole blood d-dimer assay (when not used with Wells' scoring system) or immunofiltration d-dimer assay can be used to exclude PE.

Diagnostic Usefulness of Ventilation/Perfusion Scan

The radioisotopic ventilation/perfusion (V/Q) scan has been the most widely accepted screening test for PE in the emergency department for two decades. According to the ACEP policy, if the pretest probability is less than 20 percent and the patient has a “near normal/normal” V/Q scan, PE can be excluded with reasonable certainty. In patients with a pretest probability of 20 percent or higher, a “high probability” V/Q scan can be used to diagnose PE with reasonable certainty.

Wells' Criteria for Assessment of Pretest Probability for Pulmonary Embolism

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A common practice in patients with nondiagnostic V/Q scans is to obtain duplex ultrasonography of the lower extremities, because deep venous thrombosis is present in a significant number of patients with confirmed PE. Also, a negative ultrasonographic scan significantly lowers the probability of PE in these patients. However, this negative finding should not be used to exclude PE in patients with a non-low pretest probability and a nondiagnostic V/Q scan.

Level A recommendations: In patients with a low-to-moderate pretest probability of PE, a normal perfusion scan reliably excludes clinically significant PE.

Level B recommendations: In patients with a low-to-moderate pretest probability of PE and a nondiagnostic V/Q scan, use one of the following tests instead of pulmonary arteriography to exclude clinically significant PE:

  1. A negative quantitative d-dimer assay (turbidimetric or ELISA).

  2. A negative whole blood cell qualitative d-dimer assay in conjunction with a Wells' score of 4 or less.

  3. A negative single bilateral venous ultrasonographic scan for low-probability patients.

  4. A negative serial bilateral venous ultrasonographic scan for moderate-probability patients.

Level C recommendations: In patients with a low-to-moderate pretest probability of PE and a nondiagnostic V/Q scan, use a negative whole blood d-dimer assay (when not used with Wells' scoring system) or immunofiltration d-dimer assay to exclude PE.

Diagnostic Usefulness of Spiral Computed Tomography

The spiral computed tomographic (CT) angiogram is useful for evaluating patients for PE who have conditions that result in nondiagnostic V/Q scans. According to the ACEP policy, the diagnostic sensitivity of spiral CT is at least 95 percent for segmental or larger PEs, and approximately 75 percent for subsegmental PE. A negative finding on a CT scan reliably excludes clinically significant PE.

Level A recommendations: None specified.

Level B recommendations: Thin collimation spiral CT scan of the thorax with 1- to 2-mm image reconstruction may be used as an alternative to V/Q scan during the diagnostic evaluation of patients with suspected PE.

Level C recommendations: Spiral CT scan of the thorax with delayed CT venography may be used for increased detection of patients with significant thromboembolic disease.

Indications for Fibrinolytic Therapy

The ACEP policy recommends making a risk-benefit decision when considering fibrinolytic therapy in patients with PE. Clinical trials and consensus reports of fibrinolytic agents to treat PE demonstrate that the only indication for this treatment is in patients who are hemodynamically unstable, especially in the presence of persistent systemic hypotension.

A controversial issue is whether or not right ventricular dysfunction as shown on echocardiography should be considered a criterion for fibrinolytic therapy. The ACEP policy notes that it has been established that patients with right ventricular dysfunction observed on echocardiography who are treated with fibrinolytic therapy have more rapid return of right ventricular function and restoration of pulmonary perfusion, but these improvements have not translated to improved mortality in the absence of shock.

The U.S. Food and Drug Administration has approved three regimens for treating pulmonary embolism: (1) streptokinase (250,000 U bolus, followed by 100,000 U per hour for 24 hours); (2) urokinase (1,000 U per kg for 10 minutes, followed by 1,000 U per kg per hour for 24 hours; currently unavailable in the United States); and (3) recombinant tissue plasminogen activator (100 mg infused over two hours).

Level A recommendations: None specified.

Level B recommendations: Consider fibrinolytic therapy in hemodynamically unstable patients with confirmed PE.

Level C recommendations: Consider fibrinolytic therapy in:

  1. Hemodynamically stable patients with confirmed PE and right ventricular dysfunction on echocardiography.

  2. Unstable patients with high clinical index of suspicion (especially if right ventricular dysfunction can be demonstrated on bedside echocardiography).


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