Some time early on, while on the path of emergency medicine training, pulmonary embolism (PE) becomes chiseled into the mind as one of those immediately deadly, can't-miss diagnoses that we must become expert not only at recognizing and managing but also at ruling out. To an emergency physician, the words “missed PE” rank up there with “missed MI” and “Remember that patient you saw?” as spoken phrases most likely to ruin the rest of your week.
To the rescue comes a freshly updated, must-read clinical policy by the American College of Emergency Physicians. Last updated in 2003, the policy seeks to answer six clinical questions on evaluating and managing acute PE in the emergency department. As with other ACEP clinical policies, an expert panel performed an exhaustive review of the pertinent literature, then provided summary clinical recommendations along with accompanying strength of evidence grades (A, B, or C) reflecting the quality of data available to support them.
Level A recommendations are backed by overwhelming evidence, and should be considered accepted principles of practice. Level B recommendations are management strategies provided with a moderate degree of clinical certainty. Level C recommendations have only limited evidence to support them, or alternatively are recommendations made by expert panel consensus.
Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department with Suspected Pulmonary Embolism
Fesmire FM, et al
Ann Emerg Med
Each clinical question and accompanying recommendation is summarized in the table, but a few points deserve discussion. According to the first question and its recommendation, a definitive PE clinical decision rule, risk stratification tool, or algorithmic approach still does not exist, despite numerous attempts over the years by many capable parties. No sufficient evidence supports that any one of these objective criteria strategies is superior to overall clinical gestalt. Emergency physicians can rest assured that even in 2011 there is little danger of being replaced by a computer, at least for the evaluation of acute, pleuritic chest pain.
If ever there were a simple decision rule potentially worth incorporating into your practice, it may be the Pulmonary Embolism Rule-out Criteria (PERC). (J Thromb Haemost 2004;2:1247.) Patients who are initially risk stratified by clinical gestalt into a low risk group and meet all eight PERC criteria have such a low incidence of PE (<1.4%) that they can safely be sent home without further testing.
The highly sensitive D-dimer assay, when used appropriately, can be useful. As its name implies, it is highly sensitive, and has a very low false-negative rate. When pretest probability is low and the highly sensitive D-dimer is negative, one can be confident that the patient does not have a PE. In clinical scenarios where pretest concern for PE is moderate or high, further testing may be required even after a negative D-dimer.
The most important takeaway, though, is to avoid the trap of using the highly sensitive D-dimer to replace your clinical judgment. This can happen easily when the test is ordered indiscriminately. Always remember this assay has an alternate name — the horribly specific D-dimer. When the likelihood of PE based on your clinical gestalt is extremely low risk, the best decision for your patient is not to perform any testing at all.
Patients at extremely low risk for PE are frequently and unnecessarily subjected to the hazards of subsequent CT contrast and radiation after D-dimer testing because false positive D-dimer results far outnumber true positive results in this subset of patients. In one study, after introducing the highly sensitive D-dimer assay to an academic center, without any protocol or restraint, CT angiography increased by 34 percent without any concurrent increase in the diagnosis of PE. (Acad Emerg Med 2006; 13:519.)
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Pulmonary Embolism Rule-out Criteria (PERC)
- Under 50 years old
- Heart rate less than 100 bpm
- SaO2 greater than 94%
- No unilateral leg swelling
- No hemoptysis
- No prior DVT/PE
- No recent trauma or surgery
- No hormone use
Source: J Thromb Haemost 2004; 2:1247.
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