Computed tomographic pulmonary angiography vs ventilation-perfusion lung scanning in patients with suspected pulmonary embolism: a randomized controlled trial.

CONTEXT: Ventilation-perfusion (V(dot)Q(dot) lung scanning and computed tomographic pulmonary angiography (CTPA) are widely used imaging procedures for the evaluation of patients with suspected pulmonary embolism. Ventilation-perfusion scanning has been largely replaced by CTPA in many centers despite limited comparative formal evaluations and concerns about CTPA's low sensitivity (ie, chance of missing clinically important pulmonary embuli). OBJECTIVES: To determine whether CTPA may be relied upon as a safe alternative to V(dot)Q(dot scanning as the initial pulmonary imaging procedure for excluding the diagnosis of pulmonary embolism in acutely symptomatic patients. DESIGN, SETTING, AND PARTICIPANTS: Randomized, single-blinded noninferiority clinical trial performed at 4 Canadian and 1 US tertiary care centers between May 2001 and April 2005 and involving 1417 patients considered likely to have acute pulmonary embolism based on a Wells clinical model score of 4.5 or greater or a positive D-dimer assay result. INTERVENTION: Patients were randomized to undergo either V(dot)Q(dot scanning or CTPA. Patients in whom pulmonary embolism was considered excluded did not receive antithrombotic therapy and were followed up for a 3-month period. MAIN OUTCOME MEASURE: The primary outcome was the subsequent development of symptomatic pulmonary embolism or proximal deep vein thrombosis in patients in whom pulmonary embolism had initially been excluded. RESULTS: Seven hundred one patients were randomized to CTPA and 716 to V(dot)Q(dot scanning. Of these, 133 patients (19.2%) in the CTPA group vs 101 (14.2%) in the V(dot)Q(dot scan group were diagnosed as having pulmonary embolism in the initial evaluation period (difference, 5.0%; 95% confidence interval [CI], 1.1% to 8.9%) and were treated with anticoagulant therapy. Of those in whom pulmonary embolism was considered excluded, 2 of 561 patients (0.4%) randomized to CTPA vs 6 of 611 patients (1.0%) undergoing V(dot)Q(dot scanning developed venous thromboembolism in follow-up (difference, -0.6%; 95% CI, -1.6% to 0.3%) including one patient with fatal pulmonary embolism in the V(dot)Q(dot group. CONCLUSIONS: In this study, CTPA was not inferior to V(dot)Q(dot scanning in ruling out pulmonary embolism. However, significantly more patients were diagnosed with pulmonary embolism using the CTPA approach. Further research is required to determine whether all pulmonary emboli detected by CTPA should be managed with anticoagulant therapy. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN65486961.

Use of spiral computed tomography contrast angiography and ultrasonography to exclude the diagnosis of pulmonary embolism in the emergency department.

Spiral computed tomography (CT) contrast angiography is a promising imaging modality for the diagnosis of pulmonary embolism but the negative predictive value of this test remains controversial. We performed a multi-center prospective cohort study to determine the safety of relying on a negative spiral CT contrast angiography scan to exclude pulmonary embolism. Patients presenting to the Emergency Departments of three tertiary care institutions with clinically suspected pulmonary embolism were potentially eligible for the study. Patients underwent a clinical evaluation to categorize pretest probability into low, moderate, and high categories, and had D-dimer testing performed. Patients at low pretest probability with normal D-dimer were considered to have pulmonary embolism excluded. The remaining patients underwent spiral CT contrast angiography scan of the pulmonary arterial circulation and bilateral venous ultrasound of the proximal leg veins. Patients who were confirmed to have pulmonary embolism or deep vein thrombosis were treated with anticoagulant therapy. Patients in whom the diagnosis of pulmonary embolism was excluded did not receive anticoagulant therapy and were followed for a 3-month period for the development of venous thromboembolic complications. Eight hundred fifty-eight (858) patients were enrolled in this study. Three-hundred sixty-nine (369) patients had low pretest probability and negative D-dimer results and no further diagnostic tests were performed. None of these patients subsequently developed venous thromboembolic complications (0%, 95% confidence interval [CI] 0% to 1.0%). The remaining 489 were referred for spiral CT contrast angiography scan and ultrasound. Sixty-seven patients were confirmed to have pulmonary embolism and an additional 15 patients with negative CT scans had proximal deep vein thrombosis (DVT) on ultrasound for a total prevalence of venous thromboembolism of 82/489 (16.8%). Two of 409 patients who had pulmonary embolism excluded in the initial evaluation phase developed proximal venous thromboembolism (0.5%; 95% CI 0% to 1.8%) in the 3-month follow-up period. These findings suggest that the combination of a negative spiral CT contrast angiography scan and normal venous ultrasound imaging safely excludes the diagnosis of pulmonary embolism in the Emergency Department setting.