A Novel Approach to Quantify Acute Pulmonary Embolism Using Computed Tomography Pulmonary Angiography.

Abstract

Purpose: Acute pulmonary embolism (APE) is the third leading cardiovascular cause of death. Current risk assessment approaches emphasize right ventricular (RV) dysfunction and thrombus burden quantification via computed tomography pulmonary angiography (CTPA). Traditional scoring systems, such as the Modified Miller Score (MMS) or Refined Miller Score (RMS), estimate thrombus burden but tend to oversimplify partial vessel occlusion. This study proposes a novel Obstruction Index (OI) derived from direct thrombus and vessel area measurements from CTPA imaging to improve quantification accuracy.

Materials and methods: This retrospective study analyzed imaging data from 20 patients with intermediate- to high-risk APE. Pre-randomization and posttreatment CTPA scans were assessed for RV/LV ratio, MMS, RMS, and OI. OI was derived from measured thrombus and vessel areas at defined pulmonary artery levels and from the calculated obstruction ratio. Correlations between RV/LV ratio reduction and reduction of MMS, RMS, and OI were evaluated using the Spearman correlation.

Results: Mean RV/LV ratio reduced significantly post treatment (1.498±0.396 to 1.156±0.275), as did MMS (-4.5±4.3), RMS (-4.925±4.2), and OI (-4.49±3.9). OI demonstrated a stronger correlation with RV/LV ratio reduction ( r =0.448, P =0.048) compared with MMS ( r =0.279, P =0.234) and RMS ( r =0.261, P =0.265).

Conclusions: The OI outperforms MMS and RMS in accuracy when reflecting thrombus burden reduction and shows statistically significant correlation with RV/LV ratio reduction. Direct thrombus and vessel area measurements appear to be superior for precise and reproducible APE quantification, and are especially useful for posttreatment imaging follow-ups.