High Thrombus Burden in Premature Type 1 Myocardial Infarction: Cross-Sectional Associations With STEMI Presentation, Coronary Flow, and Systemic Inflammation.

OBJECTIVE: We evaluated whether admission complete blood count-derived inflammatory indices were associated with angiographic high thrombus burden (HTB) in premature myocardial infarction (MI). METHOD: Consecutive patients aged <45 years with type 1 MI and an identifiable culprit lesion who underwent coronary angiography between 2020 and 2024 were included in this single-center, retrospective, cross-sectional analysis. Thrombus burden was assessed using the Thrombolysis in Myocardial Infarction (TIMI) thrombus grading scale, with occluded vessels reclassified after restoration of coronary flow; HTB was defined as grades 4-5. The neutrophil-to-lymphocyte ratio (NLR) and systemic inflammatory response index (SIRI) were evaluated using clinically defined multivariable logistic regression models, with and without adjustment for ST-elevation myocardial infarction (STEMI) presentation. RESULTS: Among 137 patients (77 with STEMI and 60 with non-ST-elevation myocardial infarction [NSTEMI]), 81 had an occluded culprit vessel; after restoration of coronary flow, only two lesions remained classified as grade 5. HTB was identified in 79 patients (57.7%) and was associated with STEMI presentation (67.1% vs. 41.4%, P = 0.003) and culprit vessel occlusion (69.6% vs. 44.8%, P = 0.004). Neither NLR (P = 0.54) nor SIRI (P = 0.20) differed significantly between thrombus burden categories, and neither was associated with HTB after adjustment for pre-event characteristics (odds ratio [OR] 1.05, 95% confidence interval [CI] 0.94-1.17 and OR 1.13, 95% CI 0.95-1.35, respectively) or additional adjustment for STEMI presentation (OR 1.03, 95% CI 0.92-1.14 and OR 1.08, 95% CI 0.90-1.30, respectively), whereas STEMI presentation remained significantly associated with HTB (OR 2.75, 95% CI 1.33-5.68, P = 0.006). The findings were consistent across all sensitivity analyses, and discriminatory performance was negligible (areas under the curve of 0.531 and 0.564). No significant differences in in-hospital outcomes were detected; however, these comparisons were underpowered. CONCLUSION: In young patients with angiographically confirmed type 1 MI, HTB was associated with STEMI presentation and initial coronary occlusion but not with admission inflammatory indices.