Intravascular Imaging to Predict the Coronary No-Reflow and Slow-Flow Phenomena: Advances and Perspectives

Coronary no-reflow (NF) and slow-flow (SF) are serious complications following percutaneous coronary intervention (PCI) and are associated with adverse prognoses, with microvascular obstruction (MVO) as the central underlying mechanism. Intravascular imaging techniques, including intravascular ultrasound (IVUS), optical coherence tomography (OCT), and near-infrared spectroscopy (NIRS), enable high-resolution, multidimensional (structural, compositional, and functional) assessment of coronary lesions, thereby facilitating prediction of coronary NF and SF. IVUS, with a penetration depth of 4-8 mm, can identify predictive features such as plaque rupture, attenuated plaque, positive remodeling, and large necrotic cores. OCT, with a spatial resolution of 10-20 μm and a penetration depth of 1-2 mm, is capable of detecting thin-cap fibroatheromas, cholesterol crystals, and intraplaque vasa vasorum. NIRS quantifies lipid content using the parameter maximum 4 mm lipid core burden index (maxLCBI_4mm), which demonstrates favorable predictive performance for NF and SF phenomena. When the OCT-derived fibrous cap thickness is <55 µm, the area under the curve (AUC) for predicting NF is 0.985 (95% confidence interval (CI): 0.968-1.000); meanwhile, the corresponding sensitivity and specificity for predicting SF are 93.5% and 96.7%, respectively. When the NIRS-derived maxLCBI_4mm is ≥578, the AUC for predicting SF is 0.849.