Pulmonary embolism (PE) is a major cause of cardiovascular morbidity and mortality. Current risk stratification tools have limitations in predicting short-term outcomes. Radiological parameters such as thrombus density, measured in Hounsfield Units (HU) on computed tomography pulmonary angiography (CTPA), may provide additional prognostic information.

This study aims to assess the association between pulmonary artery thrombus density on CTPA and 30-day mortality in patients with intermediate-risk PE.

This retrospective cohort study included patients diagnosed with acute PE by contrast-enhanced CTPA in the emergency department of a single tertiary center between January 1, 2022, and December 31, 2024. Only patients classified as intermediate-risk according to European Society of Cardiology guidelines were included. HU values were measured from predefined pulmonary artery locations. The primary outcome was 30-day all-cause mortality. Multivariate logistic regression and receiver operating characteristic (ROC) analyses were performed to identify independent predictors and assess discriminative ability.

A total of 121 patients (mean age: 70 ± 14.5 years; 58.5% male) were analyzed. The 30-day mortality rate was 26.4%. Thrombus HU values were significantly higher in deceased patients compared to survivors (median 76 vs. 56, p = 0.001). In multivariate analysis, HU value (OR: 1.03; 95% CI: 1.001–1.06; p = 0.04) and sPESI score (OR: 1.70; 95% CI: 1.04–2.78; p = 0.03) were independent predictors. AUCs were 0.702 for HU and 0.731 for sPESI.

Thrombus density on CTPA was independently associated with 30-day mortality in intermediate-risk PE. HU measurement may serve as a practical imaging biomarker for early prognostic assessment.