Systemic Inflammation Response Index Predicts Thrombolytic Therapy Requirement in Intermediate-High Risk Acute Pulmonary Embolism: A Retrospective Study

Background: Intermediate-high-risk acute pulmonary embolism (APE) presents a clinical challenge, as patients are hemodynamically stable at admission yet carry a substantial risk of deterioration requiring rescue thrombolytic therapy. This study evaluated whether admission complete blood count-derived inflammatory indices, particularly the Systemic Inflammation Response Index (SIRI), are associated with subsequent thrombolytic therapy requirement. Methods: In this retrospective cohort study, 134 patients with computed tomography pulmonary angiography–confirmed intermediate-high-risk APE, classified according to 2019 ESC guidelines, were grouped based on the need for rescue thrombolytic therapy (n = 52) versus no thrombolytic therapy (n = 82). Inflammatory indices were calculated from admission blood samples, and multivariable logistic regression and ROC analyses were performed. Results: Patients requiring thrombolysis had significantly higher SIRI, SII, hs-troponin I, and systolic pulmonary artery pressure (SPAP), and lower lymphocyte counts. In multivariable analysis, SIRI (OR = 2.08, 95% CI 1.37–3.13), SPAP (OR = 1.21, 95% CI 1.06–1.37), and troponin (OR = 1.01 per 10 ng/L increment, 95% CI 1.00–1.01) were independently associated with thrombolytic therapy requirement. Conclusions: SIRI, SPAP, and hs-troponin I were independently associated with thrombolytic therapy requirement in intermediate-high-risk APE. These findings are hypothesis-generating and warrant prospective validation before clinical implementation.