Chest
Volume 111, Issue 5, May 1997, Pages 1246-1248
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Clinical Investigations: Pulmonary Embolism
Prevalence of Acute Pulmonary Embolism in Central and Subsegmental Pulmonary Arteries and Relation to Probability Interpretation of Ventilation/Perfusion Lung Scans

https://doi.org/10.1378/chest.111.5.1246Get rights and content

Purpose

The purpose of this investigation is to determine the prevalence of acute pulmonary embolism (PE) limited to subsegmental pulmonary arteries.

Background

Contrast-enhanced helical (spiral) and electron-beam CT, in the hands of experienced radiologists who are skillful with this modality, are sensitive for the detection of acute PE in central pulmonary arteries, but have a low sensitivity for the detection of PE limited to subsegmental pulmonary arteries. The potential for CT to diagnose PE, therefore, is partially dependent on the prevalence of PE limited to subsegmental pulmonary arteries.

Methods

Data are from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). The largest pulmonary arteries that showed PE, as interpreted by the PIOPED angiographic readers, were identified in 375 patients in PIOPED with angiographically diagnosed PE.

Results

Among all patients with PE, 6% (95% confidence interval [CI], 4 to 9%) had PE limited to subsegmental branches of the pulmonary artery. Patients with high-probability ventilation/perfusion ( V˙/Q˙) scans had PE limited to subsegmental branches in only 1% (95% CI, 0 to 4%). Among patients with low-probability V˙/Q˙ lung scans, 17% (95% CI, 8 to 29%) had PE limited to the subsegmental branches. Patients with low-probability V˙/Q˙ scans and no prior cardiopulmonary disease had PE limited to the subsegmental pulmonary arteries in 30% (95% CI, 13 to 53%), whereas patients with low-probability V˙/Q˙ scans who had prior cardiopulmonary disease had PE limited to subsegmental pulmonary arteries in 8% (95% CI, 2 to 22%) (p<0.05).

Conclusion

Based on data from all patients with PE in PIOPED, the prevalence of PE limited to subsegmental pulmonary arteries is low, 6%. PE limited to subsegmental pulmonary arteries was most prevalent among patients with low-probability V˙/Q˙ scans, particularly if they had no prior cardiopulmonary disease.

Section snippets

MATERIALS AND METHODS

Patients in this investigation participated in either of two arms of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED): (1) the arm of patients who consented to obligatory angiography if their ventilation/perfusion ( V˙/Q˙) lung scan was abnormal as described in the original PIOPED report6 and (2) the arm of patients who were referred for pulmonary angiography. In the obligatory angiography arm of PIOPED, 251 patients showed PE by pulmonary7 angiography.6 In the

RESULTS

The prevalence of PE according to the largest pulmonary artery involved is shown for patients with high-, intermediate-, and low-probability interpretations of the V˙/Q˙ scans (Table 1). These data are further analyzed in patients according to the presence or absence of prior cardiopulmonary disease (Table 2).

Among all patients with PE, 6% (95% CI, 4 to 9%) had PE limited to subsegmental branches of the pulmonary artery (Table 1). Patients with a low-probability interpretation of the V

DISCUSSION

Angiography showed PE limited to subsegmental pulmonary arteries in 6% of patients with PE in PIOPED. Only 1% of patients with high-probability interpretations of the V˙/Q˙ scans had PE limited to subsegmental pulmonary arteries, whereas 17% of patients with low-probability interpretations of the V˙/Q˙ scans had PE limited to subsegmental pulmonary arteries. Among patients with low-probability interpretations of the V˙/Q˙ scans who had no prior cardiopulmonary disease, 30% had PE

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    The increased usage of CT pulmonary angiography has led to a 5.4% increase in the diagnosis for subsegmental PE (SSPE).48 The investigators showed the increase from the single-detector CT was 4.7%, 7.1% with the 4 detectors, 6.9% with 16 detectors, and 15.0% with the MDCT 64 detector,49 in contrast to a high probability from a V/Q scan; 1% are SSPEs.50 The investigators of PIOPED I showed that 6% of patients had SSPEs with pulmonary angiography,50,51 whereas a low-probability read on the V/Q scan had 17% of patients with PEs in the subsegmental arteries.

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