Inflammatory, Lipid, and Angiographic Differences in Young Versus Middle-Aged Hospital Survivors of Myocardial Infarction With Obstructive, Revascularization-Requiring Coronary Artery Disease

Objective: To compare composite inflammatory indices, the Atherogenic Index of Plasma (AIP), and angiographic findings between patients with acute myocardial infarction (MI) aged <55 years and those aged 55–65 years.
Method: Patients with acute coronary syndrome were retrospectively screened (n=205). Forty patients who died during hospitalization were excluded post hoc, along with 10 patients with normal coronary arteries and 10 with noncritical stenosis not requiring revascularization, leaving 145 patients: Group 1 (<55 years, n=72) and Group 2 (55–65 years, n=73). The Systemic Inflammatory Response Index (SIRI), neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), AIP, and C-reactive protein were compared with lipid, angiographic, and left ventricular ejection fraction (LVEF) parameters.
Results: Younger patients had significantly higher SIRI (1.63 vs. 1.11, P < 0.001), NLR (2.65 vs. 2.26, P = 0.004), MLR (0.261 vs. 0.200, P < 0.001), and AIP (0.440 vs. 0.298, P = 0.039). Because SIRI and MLR were collinear, each index was modeled separately with AIP and ST-segment elevation myocardial infarction (STEMI)/non-ST-segment elevation myocardial infarction (NSTEMI) status; when modeled separately, each was independently associated with younger age after adjustment for MI type (all P ≤ 0.009). LVEF was better preserved (P < 0.001), and among patients with a single identifiable culprit vessel, the right coronary artery was more frequently implicated in younger patients (47.3% vs. 22.2%, P = 0.006).
Conclusion: Young patients with MI and obstructive coronary disease showed higher inflammatory indices and a more atherogenic lipid profile than middle-aged patients. SIRI, NLR, MLR, and AIP were each independently associated with younger age in the primary multivariable models; however, across exploratory sensitivity analyses using stricter age thresholds, a continuous age model, and a death-inclusive cohort, complete blood count (CBC)-derived inflammatory indices—particularly SIRI and MLR—showed relatively consistent age-associated differences, whereas the association with AIP was more dependent on how age was defined and modeled. These findings support further investigation of CBC-derived inflammatory indices, particularly SIRI and MLR, as candidate markers of age-associated inflammatory and lipid differences among MI survivors rather than as biomarkers of premature MI or as a basis for clinical recommendations.

Keywords: Acute myocardial infarction, atherogenic index of plasma, inflammatory indices, premature coronary artery disease, systemic inflammatory response index.