Chest
Volume 100, Issue 3, September 1991, Pages 604-606
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Clinical Investigations
Diagnostic Utility of Ventilation/Perfusion Lung Scans in Acute Pulmonary Embolism Is Not Diminished by Pre-Existing Cardiac or Pulmonary Disease

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The purpose of this study was to assess the impact of prior cardiac or pulmonary disease upon the utility of ventilation/perfusion (V/Q) scans in the diagnosis of acute pulmonary embolism (PE). Ventilation/perfusion scans were evaluated among 365 patients with no prior cardiac or pulmonary disease and compared to V/Q scans in 526 patients with prior cardiac or pulmonary disease. Among patients with no prior cardiac or pulmonary disease, PE was present in 117 and PE was excluded in 248. Among patients with prior cardiac or pulmonary disease, PE was present in 140 and excluded in 386. The positive predictive value for PE of high probability V/Q scans among patients with prior cardiac or pulmonary disease, 55 of 66 (83 percent), was not significantly lower than among patients without prior cardiac or pulmonary disease, 50 of 54 (93 percent) (NS). The positive predictive value of low probability V/Q scans was similar with prior cardiac or pulmonary disease, 25 of 182 (14 percent), and without prior cardiac or pulmonary disease, 17 of 113 (15 percent) (NS), as was the predictive value of near normal/normal V/Q scans, 2 of 51 (4 percent), vs 3 of 79 (4 percent) (NS). The sensitivity of high probability V/Q scans, with pre-existing cardiac or pulmonary disease and without, 55 of 140 (39 percent) vs 50 of 117 (43 percent), did not differ significantly. The specificity of high probability V/Q scans with prior cardiac or pulmonary disease and without, 375 of 386 (97 percent) vs 244 of 248 (98 percent) was also similar (NS). In conclusion, the diagnostic utility of V/Q scans for acute PE was not impaired by the presence of pre-existing cardiac or pulmonary disease. Fewer patients, however, with no prior cardiac or pulmonary disease, had intermediate (indeterminate) V/Q scans.

(Chest 1991; 100:604-06)

Section snippets

Battent Enrollment

Patients reported in this investigation participated in the national collaborative study of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED).1 The eligible study population consisted of patients ≥18 years old, in whom acute PE was of diagnostic concern. Symptoms suggestive of PE were required within 24 hours of entry into the study.1 In the present investigation, we evaluated patients who had no history or evidence of preexisting cardiac or pulmonary disease. There were

Ventilation/Perfusion Scans

Among patients with no pre-existing cardiac or pulmonary disease, PE was present in 50 of 54 (93 percent) in whom the V/Q scan was interpreted as highly probable for PE (Table 1). Among patients in whom the V/Q scan was interpreted as low probability for PE, 17 of 113 (15 percent) had PE. Among those in whom the V/Q scan was nearly normal/normal, 3 of 79 (4 percent) had PE. No patient in whom two independent readers both read the V/Q scans as normal showed PE on angiography or had recurrent

DISCUSSION

A number of conditions such as pneumonia or local bronchospasm cause perfusion defects.2 Ventilation scans were added to perfusion scans with the thought that ventilation would be abnormal in areas of pneumonia or local hypoventilation, but would be normal in PE.3 In the present study, it was shown that the positive predictive value of high probability V/Q scans was not significantly greater among patients without pre-existing cardiac or pulmonary disease than among patients with pre-existing

ACKNOWLEDGMENT

We thank Drs. Abass Alavi, Jack E. Juni, Charles A. Hales, and James H. Thrall for their special efforts in relation to this study, as well as all of the PIOPED investigators.

REFERENCES (6)

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Cited by (0)

This study was supported by contracts NO1-HR-34007, NO1-HR-34008, NO1-HR-34010, NO1-HR-34011, NO1-HR-34012, and NO1-HR-34013 from the National Heart, Lung, and Blood Institute, Bethesda, Maryland.

Manuscript received February 21; revision accepted April 15.

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