Systemic immune inflammatory response index (SIIRI) in acute myocardial infarction.

Background: Different treatment approaches exist for non-ST elevation acute coronary syndrome (ACS) patients. This study assessed the systemic immune inflammatory response index (SIIRI) for its prognostic value and incremental clinical utility in determining optimal timing for percutaneous coronary intervention (PCI) in non-ST elevation myocardial infarction (NSTEMI) patients, particularly when troponin levels are initially negative.

Methods: This study included 1270 ACS patients: 437 STEMI, 422 NSTEMI, and 411 unstable angina. Patients were stratified by SIIRI levels measured at admission, and coronary artery disease severity was evaluated using the SYNTAX score. The primary endpoint was major adverse cardiovascular events (MACE), including cardiovascular death, non-fatal myocardial infarction, stroke, and revascularization. Secondary endpoints encompassed individual MACE components and heart failure hospitalisations.

Results: The mean age was 54.93 years (83% male). SIIRI levels were significantly higher in STEMI patients (6.83 ± 6.43 × 105) compared to NSTEMI (4.5 ± 5.39 × 105) and unstable angina (3.48 ± 2.83 × 105) (P < 0.001). Area under the curve for SIIRI distinguished NSTEMI and unstable angina from STEMI (0.81 and 0.80), with optimal cut-off points of 4.80 × 105 and 4.25 × 105. In NSTEMI, 24.6% presented within 2 h of symptom onset, were troponin-negative, yet had elevated SIIRI. Post-PCI, SIIRI > 4.93 × 105 correlated with increased MACE at 1 year (17.2% vs 5%).

Conclusion: NSTEMI and unstable angina patients with SIIRI values >4.80 × 105 and 4.25 × 105 respectively, may require urgent intervention (<2 h). SIIRI can be of significant utility in patients of NSTEMI who present earlier with negative troponins. SIIRI can also aid in identifying high-risk individuals post-PCI, providing a valuable tool for early and accurate assessment.