Evolutionary changes in thrombus features on computed tomography: An effective approach for identifying subacute pulmonary embolism

Objective: Thrombus features on computed tomography (CT) play a key role in distinguishing between acute and chronic pulmonary embolisms (PEs). However, the thrombus features of subacute PE are largely unknown. Methods: This retrospective study included 358 patients (age, 65 ± 16 years; percentage of men, 38%) diagnosed with PE from 2008 to 2019. The patients were divided into a study group and a verification group. Thrombus features that changed over time were determined in the study group according to the time of PE occurrence. Next, we determined the thrombus features of subacute PE and verified them in the verification group. Finally, we compared clinical deterioration and the 1-month mortality rate between the patients with acute and subacute PEs. Results: The main feature of eccentric thrombi that changed over time was the angle with the arterial wall, whereas those of centric thrombi were recanalization and heterogeneity. Taken together, the features of subacute PE were determined to be an obtuse angle with the arterial wall, recanalization, and heterogeneity. The accuracy of these features in identifying subacute PE was 94% during verification. Between the patients with acute and subacute PEs, there was no significant difference in clinical deterioration (19% vs 14%; P = .32) or the 1-month mortality rate (15% vs 8%; P = .11). With multivariate analysis, subacute events were also not associated with clinical deterioration (P = .8) or the 1-month mortality rate (P = .11). Conclusions: We determined the time trend of thrombus features on CT in patients with PE and found that these features can improve the identification of subacute events. Patients with acute and subacute PEs do not have different risks of clinical deterioration and 1-month mortality.