Pulmonary embolism: Assessment of patients later in life

Pulmonary embolism: Assessment of patients later in life

Marc Rodger

How does patient age influence the diagnostic approach to pulmonary embolism (PE)?

PE is a common, treatable, but potentially fatal condition that demands accurate diagnosis and management. PE is the third leading cause of cardiovascular mortality in North America, with an age-and sex-adjusted estimated incidence of 21 to 69 per 100,000 persons per year in population-based studies.[1,3] It is estimated that PE causes 5% to 10% of all in-hospital deaths. [3-5] PE has a hospital mortality rate as high as 30%, but mortality falls to near 8% if the condition is diagnosed and treated appropriately.[5,7]

Patient age is consistently a staistically significant univariate predictor for PE across prospective cohort studies of patients with suspected PE. [8-11] This is consistent with population-based epidemiologic data demonstrating an increased incidence of PE with age. [1] This may be explained by a higher incidence of other risk factors for venous thromboembolism, including malignancy, surgical procedures, and immobilization, in older patients. Hence, patient age should influence the diagnostic approach to suspected PE in that older patients have a higher pretest probability of PE than do younger patients.

Recent publications have established the saPEty of a number of diagnostic approaches to patients with suspected PE. [12-14] All of these approaches involve combining clinical pretest probability assessment and noninvasive diagnostic imaging. Perhaps the most widely accepted approach is to assign pretest probability by clinical assessment–by using overall diagnostic impression or an explicit clinical model–followed by ventilation-perfusion scan.

A normal scan result saPEly excludes the diagnosis of PE. [13] If the lung scan indicates high probability, the diagnosis of PE can be made with over 90% certainty if the clinical suspicion for PE is moderate or high. [13] If the clinical likelihood of PE is low, patients with high-probability lung scan results should undergo confirmatory testing with either pulmonary angiography or spiral CT.

If the lung scan result is non- high-probability, additional testing is required to confirm or exclude the diagnosis of PE. Historically, it has been recommended that patients with non-high-probability lung scan results should undergo pulmonary angiography. [13] Although this is an effective way to confirm or exclude PE, it is not practical in many centers and has other limitations, such as the risk of morbidity and mortality associated with the procedure.

In recent years, much attention has focused on the use of noninvasive tests for deep venous thrombosis (DVT) in patients with suspected PE who have non-high-probability lung scan results. The rationale for this approach is that the current management of DVT and PE is similar. If noninvasive testing confirms DVT, appropriate antithrombotic therapy can be initiated without the need to conclusively demonstrate PE by angiography. If noninvasive testing for proximal DVT is negative, it is reasonable to withhold antithrombotic therapy because such patients are potentially at relatively low risk for additional emboli.

The safety of using serial ultrasound imaging was demonstrated in a Canadian study. [14] Patients with a low or moderate clinical pretest probability for PE who had non-high-probability lung scan results and initial negative ultrasonographic results were safely followed with serial ultrasonography without the need for anticoagulants or pulmonary angiography.

In conclusion, patient age should influence pretest probability assessment, but once a pretest probability is assigned, the approach to older patients should be no different than that for younger patients.

MARC RODGER, MD, FRCP(C), Msc Assistant professor of medicine, University of Ottawa Faculty of Medicine; associate scientist, clinical epidemiology unit, Ottawa Health Research Institute; and medical director, thrombosis assessment and treatment unit, Ottawa Hospital General campus, Ontario.

PHILIP S. WELLS, MD, MSc Associate professor of medicine, department of epidemiology and community medicine; chief, division of hematology, University of Ottawa Faculty of Medicine; and director, thrombosis assessment and treatment unit, Ottawa Hospital Civic campus, Ontario.

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