Coronary Slow Flow and No-Reflow During Percutaneous Coronary Intervention: Contemporary Insights Into Imaging-Guided Prediction, Prevention, and Management

Coronary slow flow (SF) and no-reflow (NR) are clinically significant complications of percutaneous coronary intervention (PCI), particularly in ST-segment elevation myocardial infarction (STEMI) and saphenous vein graft (SVG) interventions. Angiographically defined as impaired myocardial perfusion despite restored epicardial patency, SF/NR results from microvascular dysfunction driven by distal embolization, ischemia-reperfusion injury, microvascular spasm, capillary plugging and emerging molecular mechanisms such as endothelial glycocalyx degradation and microRNA-mediated inflammatory pathways. These processes contribute to larger infarct size, maladaptive remodeling, and increased mortality. Advanced intracoronary imaging enables lesion-level risk stratification by identifying features such as lipid-rich cores, thin-cap fibroatheromas, positive remodeling, and thrombus. Image-guided strategies, incorporating deferred stenting, selective aspiration, and tailored lesion preparation, can mitigate distal embolization. Risk stratification models (e.g., PAMI score) and recognition of sex- and race-based disparities further refine procedural planning. Cost, accessibility, and emerging AI-driven automated plaque characterization tools are important considerations for wider implementation. Preventive measures emphasize systemic optimization, adequate anticoagulation, high-intensity statin pretreatment informed by precision dosing, dual antiplatelet therapy, and refined device techniques in thrombus-rich or calcified lesions. Management requires early recognition, systematic exclusion of mimics such as dissection or epicardial spasm, maintenance of anticoagulation, and rapid stepwise administration of intracoronary microvasculature dilators. Device-based delivery methods offer practical advantages but carry specific risks, including device entrapment or vessel trauma. Adjunctive therapies such as supersaturated oxygen may be considered in refractory cases. A structured, imaging-informed algorithm integrating preventive strategies, pharmacologic escalation, and device-assisted therapy may reduce SF/NR incidence and improve procedural and long-term outcomes. Future research should validate imaging-guided preventive strategies, standardized rescue protocols, and the role of AI-driven risk assessment in diverse patient populations.