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A case series of outcomes in isolated subsegmental pulmonary embolism on ventilation–perfusion imaging

Mallorie, Amyb; Chan, Kennethc; Ioannidis, Stefanosa,c; Stubbs, Matthewa,c; Navalkissoor, Shaunaka,c; Wagner, Thomasa,c

Nuclear Medicine Communications: July 2018 - Volume 39 - Issue 7 - p 618–620
doi: 10.1097/MNM.0000000000000866

Objectives The risk of recurrent venous thromboembolic disease and the management of patients with isolated subsegmental pulmonary embolism (SSPE) remain unclear. We sought to assess the long-term clinical outcome of patients with isolated SSPE demonstrated by isolated subsegmental mismatch found on ventilation/perfusion (V/Q) scans.

Patients and methods We performed a retrospective observational study of 1300 consecutive patients with suspected pulmonary embolism who underwent index V/Q single-photon emission computed tomography between 2012 and 2013. Forty (3%) patients were found to have isolated SSPE identified on V/Q scan. Of the 40 patients with isolated SSPE on V/Q scan, 19 underwent further investigation with computed tomography pulmonary angiogram (CTPA) within 48 h.

Results Among 19 patients who had corroborating CTPA performed concurrently, 94.7% of the SSPEs identified on V/Q were not detectable on CTPA. Of the 40 patients, 10 (25%) were anticoagulated. In a median follow-up of 3.28±0.55 years, all-cause mortality occurred in two patients, recurrence of suspected venous thromboembolism (VTE) occurred in 12 (30%) of 40 patients, but none had confirmed recurrent thromboembolism on further imaging. In the 40 patients with SSPE on V/Q, there was no difference in the risk of recurrence of suspected VTE or mortality between patients treated with anticoagulation and not treated (hazard ratio: 2.04, 95% confidence interval: 0.75–7.28).

Conclusion In this case series, a large proportion of patients with isolated SSPE on V/Q imaging were not identified on corroborating CTPA performed within 48 h. In patients with isolated SSPE (identified by isolated subsegmental mismatch on V/Q single-photon emission computed tomography), we found no difference in risk of recurrent suspected VTE or all-cause mortality in those treated with anticoagulation and those not treated.

aRoyal Free NHS Foundation Trust

bDepartment of Radiology, St George’s University of London, London

cRadcliffe Department of Medicine, Division of Cardiovascular Medicine, University of Oxford, Oxford, UK

Correspondence to Amy Mallorie, MBBS, Royal Free London NHS Foundation Trust, London NW3 2QG, UK Tel: +44 207 830 2470; fax: +44 207 830 2469; e-mail:

Received February 6, 2018

Received in revised form March 29, 2018

Accepted May 2, 2018

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