Elsevier

Mayo Clinic Proceedings

Volume 77, Issue 2, February 2002, Pages 130-138
Mayo Clinic Proceedings

Original Article
Outcomes After Withholding Anticoagulation From Patients With Suspected Acute Pulmonary Embolism and Negative Computed Tomographic Findings: A Cohort Study

https://doi.org/10.4065/77.2.130Get rights and content

Objective

To determine the outcome of withholding anticoagulation from patients with suspected acute pulmonary embolism in whom computed tomographic (CT) findings are interpreted as negative for pulmonary embolism.

Patients and Methods

This retrospective cohort study included 1512 consecutive patients referred from August 7, 1997, to November 30, 1998, for CT because of clinically suspected acute pulmonary embolism. All patients were examined by electron beam CT, and scanning was performed in a cephalocaudad direction from the top of the aortic arch to the base of the heart with 3-mm collimation, 2-mm table incrementation, and an exposure time of 0.2 second (130 peak kV, 620 mA, and standard reconstruction algorithm). Contrast material was infused at a rate of 3 to 4 mL/s through an antecubital vein with an automated injector. Findings on CT were interpreted as either positive or negative. The main outcome measures were deep venous thrombosis, pulmonary embolism, and vital status within 3 months after the CT scan and the cause of death based on medical record review, mailed patient questionnaires, and telephone interviews.

Results

In 1010 patients (67%) CT scans were interpreted as negative for acute pulmonary embolism. Seventeen patients were excluded because they received anticoagulation. Of the remaining 993 patients, deep venous thrombosis or pulmonary embolism developed in 8; 118 patients died, 3 of pulmonary embolism. Nineteen patients were known to be alive, but additional clinical information could not be obtained. The 3-month cumulative incidence of overall deep venous thrombosis or pulmonary embolism was 0.5% (95% confidence interval, 0.1%-1.0%) and of fatal pulmonary embolism, 0.3% (95% confidence interval, 0.0%-0.7%).

Conclusions

The incidence of (1) overall deep venous thrombosis or pulmonary embolism or (2) fatal pulmonary embolism among patients with suspected acute pulmonary embolism, negative CT results, and no other evidence of venous thromboembolism is low. Withholding anticoagulation in these patients appears to be safe.

Section snippets

Study Setting and Design

Using the Mayo Clinic CT database, we identified all Mayo Clinic patients who were referred for electron beam CT because of clinical suspicion of acute pulmonary embolism over the 62-week period from August 7, 1997, to November 30, 1998. From dictated indications and diagnostic American College of Radiology codes, we identified all patients who underwent CT to “rule out acute pulmonary embolism.” We chose August 7, 1997, as our beginning date because at that time we consistently used 3-mm

RESULTS

A total of 1512 consecutive patients with clinically suspected acute pulmonary embolism were referred for CT between August 7, 1997, and November 30, 1998. In 1010 of these patients, the CT scan was interpreted as negative for acute pulmonary embolism. Seventeen patients were excluded because they received anticoagulation despite negative CT results; 8 received anticoagulation for acute deep venous thrombosis, and 9 received anticoagulation for other indications. Therefore, 993 patients were

DISCUSSION

Our results show that patients with suspected acute pulmonary embolism and negative CT results have an excellent outcome without anticoagulation. Symptomatic venous thromboembolism was rare within the 3 months after negative CT results, which exclude most clinically important pulmonary embolisms.

Our results confirm and extend the findings of other investigators. Among 109 patients with negative spiral CT results from whom anticoagulation was withheld, Ferretti et al40 found a 3-month cumulative

CONCLUSIONS

The 3-month incidence of (1) overall deep venous thrombosis or pulmonary embolism or (2) fatal pulmonary embolism is low among patients with suspected acute pulmonary embolism, negative CT results, and no other evidence of venous thromboembolism. Consequently, it is safe to withhold anticoagulation in such patients.

We believe that CT should replace the radionuclide lung scan as the initial diagnostic test of choice for suspected acute pulmonary embolism.48 Frequently, CT excludes pulmonary

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    Funded in part by grants from the National Institutes of Health (HL60279), US Public Health Service, and by Mayo Foundation.

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