Slow Flow/No-Reflow After Primary Percutaneous Coronary Intervention in ST-Segment Elevation Myocardial Infarction: A Meta-Analysis

Coronary slow flow/no-reflow after primary percutaneous coronary intervention (PCI) limits myocardial reperfusion in ST-segment elevation myocardial infarction (STEMI). Clinical, laboratory, angiographic, and procedural associations were synthesized while separating crude primary analyses from adjusted-only sensitivity analyses. Seven databases were searched from inception through May 31, 2026. Random-effects models used restricted maximum likelihood estimation and Hartung-Knapp confidence intervals; 95% prediction intervals were reported when at least three studies contributed. Forty-three observational studies included 27,405 patients, including 5,631 with slow flow/no-reflow. Crude pooled averages supported associations for diabetes mellitus, Killip class II or higher/acute heart failure, advanced Killip class, impaired baseline Thrombolysis in Myocardial Infarction flow, high thrombus burden, longer stent length, thrombus aspiration, and direct stenting, although several prediction intervals included the null. Adjusted-only analyses were consistent for age, hypertension, diabetes, Killip class II or higher/acute heart failure, and high thrombus burden. Outcome-definition and eligibility sensitivity analyses did not eliminate important uncertainty. Domain-based risk-of-bias judgments were predominantly some concerns or high concern, and Grading of Recommendations Assessment, Development and Evaluation certainty was low or very low. The review, therefore, provides a cross-domain evidence map rather than a causal catalog or bedside prediction score.