Lumen–Stent Mismatch Affects Long-Term Strut Healing After Primary PCI of Left Main Lesions: An Exploratory Follow-Up OCT Study

Background: Long-term stent healing after primary PCI of culprit unprotected left main (ULM) lesions is insufficiently explored. In this setting, large vessel size and bifurcation anatomy may limit angiographic stent optimization and contribute to persistent strut malapposition and incomplete coverage. Objectives: To identify OCT-derived geometric and healing parameters associated with long-term strut coverage and malapposition after angiography-guided primary PCI of culprit ULM lesions. Methods: This single-center exploratory study included 30 patients with long-term OCT follow-up after angiography-guided primary PCI of culprit ULM lesions. OCT analysis was performed separately in three prespecified subsegments: the left main (LM), polygon of confluence (POC), and distal main branch (dMB). Five predefined strut-level healing outcomes were analysed: covered struts, malapposed struts, malapposed and uncovered struts, significantly malapposed struts (>400 μm), and significantly malapposed and uncovered struts. Associations between patient-level healing outcomes and OCT-derived measures of lumen geometry, stent dimensions, neointimal response, and an exploratory lumen–stent mismatch variable were assessed using univariable and multivariable linear regression. Results: A total of 31,703 struts were analysed. Overall strut coverage was 90.7 ± 6.6%. Compared with the dMB, proximal ULM segments (LM and POC) showed lower strut coverage (82.8% and 84.2% vs. 93.9%, p < 0.001) and higher malapposition rates (17.4% and 14.2% vs. 0.4%, p < 0.001). In regression analysis, larger native lumen dimensions were associated with lower strut coverage and higher malapposition, whereas larger achieved stent area was associated with better strut healing. The exploratory lumen–stent mismatch variable in multivariable models with all five healing outcomes in multivariable models (all p < 0.01). Conclusions: After angiography-guided primary PCI of culprit unprotected left main lesions, long-term strut healing was significantly influenced by the mismatch between native reference lumen area and the achieved mean stent area. Whether intravascular imaging–guided optimization of stent sizing and expansion in large-calibre left main anatomy improves strut healing requires further investigation.