Accuracy of multimodal intravascular imaging in evaluating neointimal tissue in a swine femoropopliteal artery stent model.

Stent failure, including in-stent restenosis (ISR) and occlusion, remains a major challenge in femoropopliteal arteries. Since the underlying cause of stent failure, such as fibrin-rich thrombus versus organized fibrous plaque, likely dictates the optimal treatment strategy, accurate characterization of neointimal tissue is crucial. However, pathological validation for key intravascular imaging modalities in this setting is lacking. A total of 22 femoral arteries with an in-stent restenosis model in healthy swine after stent implantation were evaluated. One month later, intravascular imaging using intravascular ultrasound (IVUS), optical frequency domain imaging (OFDI), and angioscopy was performed. Diagnostic accuracy for characterizing neointimal tissue ≥ 1000 μm (thick neointima) was assessed using histology as the gold standard. For detecting fibrin/organizing thrombus, IVUS showed high specificity (96%) but poor sensitivity (13%), leading to underestimation. Conversely, OFDI offered relatively high sensitivity (60%) but a modest positive predictive value (PPV, 50%), risking overestimation. A paired use of IVUS and OFDI approach overcame these limitations, yielding significantly improved diagnostic accuracy (sensitivity 50%, specificity 96%, PPV 83%). While angioscopy showed excellent specificity (100%), its utility was limited by very low sensitivity (24%). Paired use of IVUS and OFDI may improve diagnostic confidence for neointimal tissue characterization. In contrast, the utility of angioscopy appears limited due to low sensitivity.