Incidental pulmonary embolism in suspected stroke patients undergoing carotid CT angiography

The purpose of this study was to investigate the prevalence of incidental pulmonary embolism (IPE) in suspected stroke patients receiving carotid computed tomography angiography (CTA) and its characteristics.

A total of 4873 cases receiving carotid CTA between January 2013 and December 2016 were retrospectively reassessed by one radiologist. Patients with previous or suspected PE were excluded. The remaining prior contrast-enhanced carotid CTA studies were regarded as a "potentially incidental" IPE when a filling defect was found in one or more pulmonary arteries and subjected to the other two thoracic radiologists independently for reviewing and assessing for characteristics of the IPE and the image quality of the PE. The differences were noted between inpatients and outpatients in prevalence of IPE. Characteristics of the patients with IPE were also studied in terms of gender, age, as well as clinical indication.

The prevalence of IPE among these suspected stroke patients was 0.8% on carotid CT angiography, and 24 (96%) of all IPEs had not been previously diagnosed by the original reporting radiologists. Most of the IPEs were at the lobar or segmental levels, single and in right upper lobe of pulmonary arteries. In most of the cases, the reviewing radiologists judged the contrast bolus as good. The outpatient group had a lower percentage of patients with IPE when compared with the inpatient counterpart (p = 0.024). The prevalence of IPE in patients with suspected stroke was higher with the increasing of age (p = 0.013).

IPE can occur in suspected stroke patients on carotid CT angiography, and most of them have been previously neglected in clinical practice. Radiologists should check the higher pulmonary arterial vasculature carefully on the contrast-enhanced carotid CTA scans.