Intermediate coronary artery stenosis, defined as visual angiographic stenosis severity of between 30-70%, is present in up to one quarter of patients undergoing coronary angiography. Patients with this particular lesion subset represent a distinct clinical challenge, with operators often uncertain on the need for revascularization. Although international guidelines appropriately recommend physiological pressure-based assessment of these lesions utilizing either fractional flow reserve (FFR) or quantitative flow ratio (QFR), there are specific clinical scenarios and lesion subsets where the use of such indices may not be reliable.Intravascular imaging, mainly utilizing intravascular ultrasound (IVUS) and optical coherence tomography (OCT) represents an alternate and at times complementary diagnostic modality for the evaluation of intermediate coronary stenoses. Studies have attempted to validate these specific imaging measures with physiological markers of lesion-specific ischaemia with varied results. Intravascular imaging however also provides additional benefits that include portrayal of plaque morphology, guidance on stent implantation and sizing and may portend improved clinical outcomes. Looking forward, research in computational fluid dynamics now seeks to integrate both lesion-based physiology and anatomical assessment using intravascular imaging. This review will discuss the rationale and indications for the use of intravascular imaging assessment of intermediate lesions, while highlighting the current limitations and benefits to this approach.

The introduction of drug-eluting stents (DES) significantly reduced angiographic restenosis and the clinical need for revascularization following percutaneous coronary intervention. However, concerns remain regarding the long-term safety and efficacy of DES. The use of durable polymers for drug elution that have limited biocompatibility is thought to contribute toward DES failure, by promoting an adverse local inflammatory response and vascular toxicity. Biodegradable polymer and polymer-free metallic stents represent two novel technological solutions to this challenging clinical problem. This review summarizes the available clinical evidence supporting the use of either biodegradable polymer or polymer-free DES platforms.

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