Inflammatory cell response following ST-elevation myocardial infarction treated with primary percutaneous coronary intervention and its impact on cardiovascular outcomes: A systematic review and meta-analysis

Background: Inflammatory responses post STEMI may mediate major adverse cardiovascular events (MACE). This is the first systematic review to map leukocyte response following a STEMI and its association with outcomes. Methods: We systematically searched EMBASE and Medline for studies of STEMIs undergoing primary PCI. Eligible studies reported leukocytes or its subtype plus either 30-day and/or 1-year MACE. Random effects model for pooled proportions was used to estimate 30-day and 1-year mortality and MACE. Meta-regression was used to estimate the effect of leukocyte counts on cardiovascular outcomes. Publication bias was assessed using Egger's regression-based test. The review was registered with PROSPERO (CRD42019124991). Results: Of the 3,813 studies meeting the preliminary search criteria, 24 cohort studies were eligible for inclusion, representing 19,074 persons [76.4% male (n = 14,539); mean age 61.6 years]. Leukocytes had a mean of 10.5x109 (SD 4.7) on admission and 11.1x109 (SD 3.3) at day one post STEMI. Neutrophils increased day one post STEMI, while lymphocytes decreased. There was limited data on other leukocyte subtypes and beyond day one. Estimated 30-day and 1-year all-cause mortality were 6.5% (95% CI 4.8-8.2, p <0.001) and 9.7% (95% CI 5.6-13.8, p <0.001), while the estimated 30-day and 1-year MACE were 14.9% (95% CI 5.3-24.4, p < 0.001) and 15.2% (95% CI 7.2-23.2, p < 0.001). The meta-analysis was limited by a high degree of heterogeneity between studies. Conclusions: This review highlights the urgent need to better characterise inflammation post STEMI to identify mediators for the persistently high mortality and morbidity associated with STEMI.