Variable diagnostic approach to suspected pulmonary embolism in the ED of a major academic tertiary care center

Pulmonary embolism

Pulmonary embolism (PE) remains one of the most challenging medical diseases in the emergency department. PE is a potentially life threatening diagnosis that is seen in patients with chest pain and/or dyspnea but can span the clinical spectrum of medical presentations. In addition, it does not have any particular clinical feature, laboratory test, or diagnostic modality that can independently and confidently exclude its possibility. This article offers a review of PE in the emergency department. It emphasizes the appropriate determination of pretest probability, the approach to diagnosis and management, and special considerations related to pregnancy and radiation exposure.

Clinical conditions and patient factors significantly influence diagnostic utility of D-dimer in venous thromboembolism

Determining D-dimer levels remains important in the diagnostic algorithms for venous thromboembolism (VTE). The present study aimed to identify factors influencing D-dimer utility in diagnosing VTE. Consecutive symptomatic medical patients, who attended our emergency department from 1 November 2006 to 31 December 2006, had D-dimer levels measured as fibrinogen equivalent units (FEU), following clinical risk assessment. Diagnosis of VTE was established by venous compression ultrasonography and computed tomographic pulmonary angiography. VTE-negative patients were followed for 2 months to detect future occurrence of thromboembolism. Impact of various factors on D-dimer levels was analyzed. Four thousand and twenty-six patients attended our emergency department, and 525 patients (median age 52 years) had D-dimer assessed. Final diagnosis of VTE was established in 25 (4.7%) patients on radiological investigations. Median D-dimer levels for VTE-negative patients less than 60 years old, with normal renal function and chest radiology were 0.38 microgFEU/ml (range 0.19-2.3), 0.39 microgFEU/ml (range 0.17-3.5) and 0.39 microgFEU/ml (range 0.1-4.3), respectively. Similar figures for those at least 60 years, with renal impairment and abnormal chest radiology, were 0.75 microgFEU/ml (range 0.22-4.3), 0.52 microgFEU/ml (range 0.17-4.4) and 0.92 microgFEU/ml (range 0.26-5.6), respectively. Factors including patient age, renal function and chest radiology had significant influence on D-dimer levels (P < 0.01). A triad of patient age at least 60 years, renal impairment (modification of diet in renal disease stage 2-5) and abnormal chest radiology had a false positive D-dimer in 96% of patients (n = 72). Use of D-dimer in patients with a triad of advanced age, renal impairment and abnormal chest radiology has no practical diagnostic value in VTE.

Utilization patterns and diagnostic yield of 3421 consecutive multidetector row computed tomography pulmonary angiograms in a busy emergency department

OBJECTIVE

To compare examination volume and diagnostic yield of computed tomography (CT) pulmonary angiography (CTPA) and ventilation-perfusion (V/Q) scintigraphy for detection of suspected pulmonary embolism (PE) in emergency department patients.

METHODS

Every CTPA and V/Q scan result for emergency department patients between October 2001 and September 2005 were reviewed. Patients with prior PE and follow-up examinations were excluded.

RESULTS

A total of 3421 CTPA examinations and 198 V/Q scans met inclusion criteria. Average CTPA examinations completed per month increased 227%, from 33.4 to 109.2 for the first and last 24-month periods, respectively. Ventilation-perfusion scintigraphy volume decreased 80% (from 6.9 to 1.4 per month). Total diagnoses of PE per month increased 89% from 4.0 to 7.5, whereas the percentage of positive CTPA examinations dropped from 9.8% to 6.8%.

CONCLUSIONS

Availability of CT in the emergency department and lower physician thresholds for test utilization have increased the use of CT pulmonary angiography and increased detection of PE.

Is e-mail communication effective in changing ordering patterns in the emergency department? A case study of computed tomography for pulmonary embolus

RATIONALE AND OBJECTIVES

We sought to evaluate the effectiveness of e-mail communication to reduce the utilization of computed tomography for pulmonary thromboembolism (PE) in young patients (aged 40 and under) in our institution.

MATERIALS AND METHODS

An e-mail was sent to all of our institution's emergency department (ED) physicians in response to a series of negative PE studies in young females. The periods 90 days before and 90 days after were evaluated to assess the total number of PE studies performed in patients aged 40 and younger, the rate of positivity, and the utilization of D-dimer and ventilation/perfusion scans during each period.

RESULTS

Over the 180-day period, a total of 65 PE studies were ordered in patients aged 40 and younger in the ED. Studies were positive for PE in 1 of 33 (3%) before the e-mail and 4 of 32 (12.5%) after (P = .343). There was no difference in the number of D-dimer studies ordered during each period for patients studied with computed tomography. Ventilation/perfusion scanning was not performed on any ED patients younger than 40 during the 180-day period.

CONCLUSIONS

One-time e-mail communication was not effective in changing ED ordering habits of PE studies. Scant information exists in regard to effective clinician-to-clinician communication. Further evaluation for successful mechanisms to promote health practice reform and quality improvement is necessary.

Internal Barium Shielding to Minimize Fetal Irradiation in Spiral Chest CT: A Phantom Simulation Experiment

PURPOSE

To use a phantom to prospectively examine the attenuating effect of barium sulfate as an internal shield to protect the fetus.

MATERIALS AND METHODS

In an adult-size phantom, 1- and 2-cm-thick acrylic slabs containing 315 or 630 mL of water, 2% or 40% barium sulfate suspension, and a 1-mm lead sheet were placed under the diaphragm. In 17 experiments, fetal dose was measured by using thermoluminescent dosimeters that were placed immediately under (near field) and 10 cm below (far field) the water slab (eight experiments), barium sulfate slab (eight experiments), and lead sheet (one experiment). In a pulmonary embolism protocol, the phantom was scanned with single-detector spiral computed tomography (CT) at 130 kVp and 230 mAs.

RESULTS

The control radiation dose was 3.60 mSv+/-0.54 (standard deviation) with the water slab at near field, where the uterus dome is at near term, and 0.507 mSv+/-0.07 with the water slab at far field, the uterus position during early gestation. Scattered radiation was attenuated 13% and 21% with 2% barium sulfate and 87% and 96% with 40% barium sulfate, as calculated in the near and far fields, respectively, and 99% with the 1-mm lead sheet. The extrapolated attenuations for 5%-40% barium sulfate suspensions indicated that beyond a 30% suspension, attenuation increased further only slightly.

CONCLUSION

Study results in the phantom experiment suggest that fetal irradiation during maternal chest CT can be reduced substantially with barium shielding.

Computed Tomography and Pulmonary Embolus: A Review

Pulmonary embolus (PE) is a common clinical condition with significant morbidity and mortality that remains a diagnostic challenge for clinicians. Although many tests exist, multi-detector computed tomography (MDCT) pulmonary angiography has recently emerged as the test of choice. MDCT technique, diagnostic criteria, prognosis assessment and common causes of misdiagnosis are reviewed with a look toward future trends.

CT pulmonary angiography: a comparative analysis of the utilization patterns in emergency department and hospitalized patients between 1998 and 2003

OBJECTIVE

The purpose of our study was to objectively examine the temporal utilization patterns of CT pulmonary angiography in emergency department and hospitalized patients in an academic tertiary care center.

SUBJECTS AND METHODS

Patients who underwent CT examination for suspected pulmonary embolism either through our emergency department or as inpatients during a recent 9-month interval were identified. The absolute number of studies and incidence of positive results and ancillary findings were compared with similar data published from our institution during the corresponding 9-month interval in 1997-1998.

RESULTS

The overall number of patients imaged for pulmonary embolism was significantly greater in the 2002-2003 period than in the 1997-1998 period (homogeneity of rates = 88.45, p < 0.0001). The absolute number of scans obtained was significantly greater in both the emergency department (chi(2) = 167.03, p < 0.0001) and inpatient (chi(2) = 210.62, p < 0.0001) groups in the more recent population. Significantly fewer ancillary findings were reported in both the emergency department (chi(2) = 5.93, p = 0.019) and inpatient (chi(2) = 6.03, p = 0.015) groups in the more recent population. The incidence of CT-detected pulmonary embolism was significantly less in both the emergency department (chi(2) = 34.26, p < 0.0001) and inpatient (chi(2) = 8.52, p < 0.01) groups in the more recent population. This decrease in the incidence of scans with positive findings for pulmonary embolism over time was significantly greater in the emergency department group than the inpatient group (homogeneity of odds = 0.003, p < 0.007).

CONCLUSION

The evolution of CT pulmonary angiography utilization has led to a significant increase in the number of patients being imaged for pulmonary embolism with a coincident significant decrease in the rates of CT-detected pulmonary embolism and ancillary findings both in emergency department and hospitalized patients.

Spiral computed tomography for acute pulmonary embolism

There is still considerable debate about the optimal diagnostic imaging modality for acute pulmonary embolism. If imaging is deemed necessary from an initial clinical evaluation such as d-dimer testing, options include nuclear medicine scanning, catheter pulmonary angiography, and spiral CT. In many institutions, spiral CT is becoming established as the first-line imaging test in daily clinical practice. With spiral CT, thrombus is directly visualized, and both mediastinal and parenchymal structures are evaluated, which may provide important alternative or additional diagnoses. However, limitations for the accurate diagnosis of small peripheral emboli, with a reported miss rate of up to 30% with single-slice spiral CT so far, have prevented the unanimous embrace of spiral CT as the new standard of reference for imaging pulmonary embolism. The clinical significance of the detection and treatment of isolated peripheral pulmonary emboli is uncertain. Evidence is accumulating that it is safe practice to withhold anticoagulation in patients with suspected pulmonary embolism on the basis of a negative spiral CT study. Remaining concerns about the accuracy of spiral CT for pulmonary embolism detection may be overcome by the introduction of multidetector-row spiral CT. This widely available technology has improved visualization of peripheral pulmonary arteries and detection of small emboli. The most recent generation of multidetector-row spiral CT scanners appears to outperform competing imaging modalities for the accurate detection of central and peripheral pulmonary embolism. In this review, we assess the current role and future potential of CT in the diagnostic algorithm of acute pulmonary embolism.

Non-invasive diagnostic work-up of patients with clinically suspected pulmonary embolism; results of a management study

BACKGROUND

Clinicians often deviate from the recommended algorithm for the diagnosis of pulmonary embolism consisting of ventilation-perfusion scintigraphy and pulmonary angiography.

OBJECTIVES

To assess the safety and feasibility of a diagnostic algorithm which reduces the need for lung scintigraphy and avoids the use of angiography.

PATIENTS AND METHODS

Consecutive patients with a clinical suspicion of pulmonary embolism were prospectively investigated according to an algorithm in which the diagnosis of pulmonary embolism was excluded after a low clinical probability estimate and a normal d-dimer test result, a normal perfusion scintigraphy result, or a non-high probability scintigraphy result in combination with normal serial ultrasonography of the legs. In these patients anticoagulant treatment was withheld and they were followed up for 3 months to record possible thromboembolic events. During the study period, 923 consecutive patients were seen, of whom 292 were excluded because of predefined criteria.

RESULTS

Of the 631 included patients, the diagnosis was refuted on the basis of a low clinical probability estimate and a normal d-dimer test result (95 patients), normal perfusion scintigraphy (161 patients) and non-high probability lung scintigraphy followed by normal serial ultrasonography (210 patients). Of these 466 patients, venous thromboembolic complications during follow-up occurred in six (complication rate 1.3%, 95% confidence interval 0.5, 2.8). The diagnostic protocol was completed in 92% of all included patients.

CONCLUSION

The diagnosis of pulmonary embolism can be safely ruled out by a non-invasive algorithm consisting of d-dimer testing combined with a clinical probability estimate, lung scintigraphy, or serial ultrasonography of the legs (in case of non-diagnostic lung scintigraphy).

A rapid quantitative turbimetric d-dimer assay has high sensitivity for detection of pulmonary embolism in the ED

Many rapid d-dimer assays are commercially available with wide ranges of reported sensitivities, often based on small sample sizes. This has limited their intended use as rapid and inexpensive tests to evaluate pulmonary embolism in the low-risk patient. We sought to determine the sensitivity of the STA-Liatest D-Di d-dimer assay in our ED. We performed a retrospective analysis of 103 patients seen in our ED with the admitting diagnosis of known or suspected pulmonary embolism. These charts were assessed to establish if a d-dimer assay was performed within 24 hours. These charts were then reviewed to determine what diagnostic studies were performed and what final diagnosis was reached. Of the 103 charts identified, 55 had d-dimer assays performed within 24 hours. Of those, 38 were diagnosed with pulmonary embolism; none had negative d-dimer assays (<400 ng/mL). Using the exact method, the sensitivity of this assay was calculated to be 100% with a 95% confidence interval (CI) of 91.4% to 100%. Our results suggest that the STA-Liatest D-Di d-dimer assay could have an adequate sensitivity to be used to rule out pulmonary embolism in low-risk patients. Further prospective studies with larger sample sizes are required to validate this observation.

CT angiography for diagnosis of pulmonary embolism: state of the art

In daily clinical routine, computed tomography (CT) has practically become the first-line modality for imaging of pulmonary circulation in patients suspected of having pulmonary embolism (PE). However, limitations regarding accurate diagnosis of small peripheral emboli have so far prevented unanimous acceptance of CT as the reference standard for imaging of PE. The development of multi-detector row CT has led to improved visualization of peripheral pulmonary arteries and detection of small emboli. The finding of a small isolated clot at pulmonary CT angiography, however, may be increasingly difficult to correlate with results of other imaging modalities, and the clinical importance of such findings is uncertain. Therefore, the most realistic scenario to measure efficacy of pulmonary CT angiography when PE is suspected may be assessment of patient outcome. Meanwhile, the high negative predictive value of a normal pulmonary CT angiographic study and its association with beneficial patient outcome has been demonstrated. While the introduction of multi-detector row technology has improved CT diagnosis of PE, it has also challenged its users to develop strategies for optimized contrast material delivery, reduction of radiation dose, and management of large-volume data sets created at those examinations.

CT venography in suspected pulmonary thromboembolism

Pulmonary embolism (PE) and deep venous thrombosis (DVT) are a continuum and are difficult to diagnose clinically. Combined CT venography and pulmonary angiography (CTVPA) is a single examination that combines multidetector CT pulmonary angiography (CTPA) and CT venography (CTV) of the abdomen, pelvis, and lower extremities, providing "one-stop shopping" for venous thromboembolism without additional venipuncture or i.v. contrast, and it adds only a few additional minutes to scanning time. CTVPA rapidly and accurately examines the deep veins, reveals the presence, absence, and extent of deep venous thrombosis, serves as a baseline, and helps guide patient management. Multiple investigators have reported a high degree of accuracy when CTV is compared with venous ultrasound. There are some pitfalls in image interpretation, especially with regard to mixing artifacts, and there are continuing controversies as to exactly which parts of the abdomen, pelvis, and legs should be scanned routinely, the ideal timing of CTV acquisition relative to contrast injection, and the slice thickness and gap, if any, that should be used.

Spiral CT for pulmonary embolism: the paradigm has shifted

Computed tomography (CT) is rapidly becoming the first-line modality for imaging pulmonary embolism (PE). However, limitations for the accurate diagnosis of small peripheral emboli have prevented the unanimous embrace of CT as the new standard of reference for imaging PE, although the actual significance of isolated peripheral emboli is uncertain. At the same time, the high negative predictive value of CT pulmonary angiography for excluding clinically significant PE has been established. The introduction of multidetector-row spiral CT has greatly improved visualization of peripheral pulmonary arteries and detection of small emboli. Previous concerns regarding the use of spiral CT for the accurate diagnosis of peripheral pulmonary emboli should thus be overcome. Multidetector-row spiral CT has become a widely available and cost-effective technology and appears to have surpassed other imaging modalities for the accurate detection of central and peripheral PE. In this review, the authors assess the current role of spiral CT in the diagnostic algorithm of PE.