Introduction: Pulmonary embolism (PE) is a life-threatening cardiovascular condition characterized by the obstruction of pulmonary arteries, typically due to blood clots originating from deep vein thrombosis (DVT). Notably, sudden death occurs in approximately 25% of undiagnosed PE cases. Early identification and risk stratification of PE patients remains a challenge; the few biomarkers currently available in clinical practice lack specificity and are insufficient in predicting disease severity. This study investigates fibrinolytic, endothelial, and inflammatory biomarkers in acute PE, with a focus on their relationship to blood cellular indices and clinical features such as risk severity and obesity.

Materials and Methods: Plasma samples from 66 patients diagnosed with acute PE and managed by the Pulmonary Embolism Response Team (PERT) were collected under a pre-approved IRB protocol at Loyola University Medical Center. Controls were normal human plasma samples from 15 individuals. Expression of fibrinolytic (D-dimer, PAI-1, tPA) and endothelial (vWF, Angiopoietin-2, nitrotyrosine) biomarkers were quantified using sandwich Enzyme-Linked Immunosorbent Assays. TNFα, a pro-inflammatory cytokine, was measured using Chemiluminescence Biochip Array from Randox Technology. Statistical analyses were performed using GraphPad Prism. Clinical data, including PE risk severity and BMI, was obtained from EPIC medical records. Complete blood counts were used to calculate neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII).

Results: The cohort included 43.9% female and 56.1% male patients, with a median age of 66.5 years. Based on AHA guidelines for PE risk stratification, there were 5 high-risk, 33 intermediate-risk, and 28 low-risk patients. 59.1% of all patients were categorized as obese (BMI ≥ 30), while 40.9% were non-obese.

Fibrinolytic biomarkers were significantly elevated in PE patients compared to controls, including D-dimer (p < 0.0001), PAI-1 (p < 0.0001), and tPA (p < 0.0001). Markers of endothelial dysfunction were also higher in patients, including vWF (p < 0.0001), Angiopoietin-2 (p < 0.0001), and nitrotyrosine (p = 0.0033). Additionally, pro-inflammatory TNFα was increased in PE patients (p = 0.0084). Among all biomarkers, those related to fibrinolytic dysfunction exhibited the greatest fold increases in PE patients compared to controls; D-dimer showed the highest fold change (10.5x), followed by PAI-1 (3.6x) and tPA (3.1x). Correlation analyses revealed moderate positive associations between tPA and PAI-1 (r = 0.47), D-dimer and vWF (r = 0.41), and tPA and vWF (r = 0.37). Nitrotyrosine demonstrated negative correlations with Angiopoietin-2 (r = -0.27) and vWF (r = -0.22).

When stratified by PE risk severity, D-dimer (p = 0.0129) and vWF (p = 0.0279) levels distinguished intermediate from low-risk patients. Interestingly, nitrotyrosine levels were decreased in high-risk patients compared to both intermediate (p = 0.0498) and low-risk groups (p = 0.0219). NLR (p = 0.0163) and MLR (p = 0.0321) were also elevated in intermediate-risk patients compared to low-risk patients. Lastly, when stratified by BMI, tPA was significantly lower in obese compared to non-obese patients (p = 0.0288).

Conclusion: This study presents fibrinolytic, endothelial, and inflammatory dysregulation in acute PE. Fibrinolytic markers (D-dimer, PAI-1, tPA) showed the highest fold increases in patients, suggesting their central role in the pathophysiology of PE. Elevated endothelial (vWF, Angiopoietin-2, nitrotyrosine) and inflammatory (TNF-α) biomarker levels further underscore the thrombo-inflammatory state of PE. Importantly, D-dimer and vWF differentiated between intermediate and low-risk groups, signifying potential roles in early risk stratification. Nitrotyrosine, which was inversely correlated with PE severity, may serve as a novel marker of oxidative stress. Inflammatory blood cellular indices (NLR, MLR) were also correlated with PE severity, highlighting their prognostic value. Stratification by obesity revealed a reduction in tPA among obese patients, indicating that dysregulated fibrinolysis may be contributing to increased thrombotic risk in this patient population. These findings emphasize the value of combining cellular indices and clinical stratification with biomarker profiling to improve management of acute PE.

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2025
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