Assessment of the Effectiveness of Early Versus Delayed Invasive Strategies in Non-ST Elevation Myocardial Infarction (NSTEMI): A Systematic Review and Meta-Analysis

In recent years, early invasive strategies for non-ST-elevation myocardial infarction (NSTEMI) have been increasingly studied as a means of promptly identifying and treating culprit coronary lesions. However, the optimal timing of invasive management remains uncertain, particularly because most available evidence is derived from developed or high-resource healthcare settings. This systematic review and meta-analysis compared early vs. delayed invasive strategies in adults with NSTEMI for major adverse cardiovascular events and key secondary outcomes. A Population, Intervention, Comparison, Outcome framework guided eligibility criteria, and relevant studies were identified through PubMed/MEDLINE, Cochrane, and Embase. Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines were followed, and quantifiable outcomes were analyzed using RevMan v5.4.1 (The Cochrane Collaboration, London, UK). Ten studies were included. Overall, five of 10 studies reported significant benefits favoring early or immediate invasive strategies, four found no significant benefit in adjusted or long-term analyses, and one reported increased adverse events with early intervention. Meta-analysis showed that early intervention significantly reduced all-cause mortality (risk ratio (RR) = 0.68, 95% confidence interval (CI): 0.61-0.76, p < 0.00001) and rehospitalization due to heart failure (RR = 0.41, 95% CI: 0.29-0.58, p < 0.0001). However, no significant benefit was observed for nonfatal acute myocardial infarction (RR = 0.62, 95% CI: 0.18-2.11, p = 0.45) or cardiovascular death at five years (RR = 0.99, 95% CI: 0.66-1.48, p = 0.94). Early invasive intervention within 24 hours may improve selected NSTEMI outcomes, especially mortality and heart-failure rehospitalization. However, because the included studies were predominantly from developed countries, these findings may not be directly applicable to low-resource settings where catheterization facilities, specialists, and rapid referral systems are limited. Further evidence from low- and middle-income regions is needed.