Breaking through complexity: the expanding role of optical coherence tomography in PCI of complex coronary lesions

Coronary angiography frequently encounters challenges related to the insufficient evaluation of lesion severity during diagnostic procedures, as well as the inaccurate assessment of stent implantation during percutaneous coronary interventions (PCI) (1). Furthermore, relying solely on angiographic guidance might overlook certain aspects (i.e., the presence of calcium, vulnerable plaque), resulting in suboptimal results and less favorable clinical outcomes (2,3). Intravascular imaging (IVI) precisely evaluates plaque composition, lesion characteristics, reference areas, and landing zones. These evaluations aid in device selection, determining the stent deployment technique, and addressing eventual stent complications (4-8). The contemporary challenge is to apply this better knowledge to offer clinical advantages. Multiple randomized clinical trials (RCT) have investigated IVI guidance across various lesion subsets (9-13), and data in in complex PCI indicate that IVI use reduces the risks of major cardiovascular events (MACE) (9,10). However, most of these studies were conducted either solely or predominantly using intravascular ultrasound (IVUS), resulting in limited data for optical coherence tomography (OCT). Randomized comparisons have shown that OCT and IVUS guidance result in comparable clinical outcomes (11,12). However, the ILUMIEN IV: OPTIMAL PCI (Optical Coherence Tomography Guided Coronary Stent Implantation Compared with Angiography: A Multicenter Randomized Trial in PCI), which included patients at high-risk of ischemic events, revealed the absence of significant differences in target-vessel failure of OCT-guided PCI at 2-year follow-up when compared to angiography (13). In a recent issue of The Lancet, Hong et al. described the results of the OCCUPI (The Optical Coherence Tomography-guided Coronary Intervention in Patients with Complex Lesions) (14); this was a multicenter (from 20 South-Korean centers), superiority RCT that randomized 1,604 patients to undergo PCI of complex lesions with drug-eluting stents under OCT-guidance (n=803) or angiography-guidance (n=801). Complexity criteria were acute myocardial infarction (AMI), chronic total occlusion (CTO), long lesions (angiographically-based expected stent length ≥28 mm), calcifications, intracoronary thrombus at angiography, unprotected left main disease (ULMD), bifurcation lesion, small vessel disease (vessel diameter <2.5 mm), in-stent restenosis, stent thrombosis, or bypass graft lesions (10,14). The primary endpoint was the rate of MACE (a composite of cardiac mortality, myocardial infarction, stent thrombosis, or ischemia-driven target-vessel revascularization) at 1-year (10,14). In the OCT-group, 37 (5%) patients met the primary endpoint, compared to 59 (7%) in the angiography-group [absolute difference: –2.8%, 95% confidence interval (CI): –5.1 to –0.4; hazard ratio (HR): 0.62; 95% CI: 0.41 to 0.93; P=0.023]. The OCT-group had less ischemia-driven target-vessel revascularization (HR: 0.36; 95% CI: 0.18 to 0.69; P=0.0022) and spontaneous AMI (HR: 0.36; 95% CI: 0.15 to 0.86; P=0.022). No significant differences were reported in all-cause mortality (HR: 0.83, 95% CI: 0.25 to 2.72; P=0.76) or cardiac mortality (HR: 0.20; 95% CI: 0.03 to 1.71; P=0.14) between the two groups. Moreover, despite higher contrast volume and extended procedure times, OCT-guided procedures did not increase rates of contrast-induced nephropathy. In addition, a significant finding from the OCCUPI trial indicated that PCI optimization resulted in a lower incidence of the primary endpoint compared to patients who did not receive OCT optimization (HR: 0.33; 95% CI: 0.17 to 0.65; P=0.0012). There were no meaningful differences observed between patients without OCT optimization and those guided solely by angiography (absolute difference: 1.2%; 95% CI: −2.9 to 5.3; HR: 1.18, 95% CI: 0.70 to 1.97; P=0.54). The authors deserve praise for contributing to the evidence supporting IVL in guiding PCI, especially for those with complex lesions who may benefit most from it. The OCCUPI results align with other studies (15-17), indicating that the advantage of IVI comes not just from using these tools, but from utilizing the data to achieve the best outcomes (7). The differences in results between the OCCUPI and the ILUMIEN-IV should be interpreted considering some factors. First, in the ILUMIEN-IV were included patients with diabetes and ULMD-PCI were excluded. OCT guidance is expected to be more effective for more complex lesions and this difference may have affected the observed benefits. Moreover, a greater minimal lumen diameter was observed in the OCCUPI [2.75-mm (OCT) vs. 2.59-mm (angiography)] respect to the ILUMIEN-IV [2.65-mm (OCT) vs. 2.61-mm (angiography)] (4,14). However, certain aspects require further clarification. Including ACS and small vessel disease in the definition of complex PCI doesn’t align with many operators’ views (10). They used a mainly anatomical definition, despite growing acknowledgment that complex PCI involves patient, procedural, and lesion characteristics. Moreover, the role and impact of OCT may vary with different complex lesions (Figure 1). For ULMD (18) and bifurcation (19) lesions OCT provides detailed imaging necessary for accurate stent placement and optimization. In the management of heavily calcified lesions, OCT helps to evaluate the extent of calcifications, guiding the selection of the most appropriate modification device (20). When facing in-stent restenosis, OCT is advisable to identify the underlying cause, such as neointimal hyperplasia or stent under-expansion. This information guides the appropriate treatment approach, such as additional stenting or balloon angioplasty (21). Within the context of ACS, OCT aids to accurately identify culprit lesions in ambiguous cases (22). However, its use is limited when facing with CTOs, graft lesions, and small vessels due to technical difficulties and the theoretical risk of complications. Thus, OCT application depends on weighing lesion characteristics against potential risks for optimal patient outcomes. The reasons for sub-optimal OCT results in about 30% of OCCUPI participants are unclear, though most studies report up to 50% (15-17). Inexperience with IVI could be a factor, considering that OCT technical demands and the associated costs could be prohibitive for widespread adoption, especially in regions with limited healthcare resources. Therefore, expertise and training in OCT interpretation are crucial, highlighting the importance of ongoing professional development and standardizing OCT-guided procedures. Some limitations about the OCCUPI trial need to be discussed. First, the trial was conducted only in the Korean population, thus the generalizability of the results still needs to be confirmed. An important aspect to consider is that while the OCCUPI trial demonstrates promising early results, the absence of extended follow-up leaves open the question of whether these improvements persist at long-term follow-up. In conclusion, with current data, the focus shifts from whether to use IVI in complex PCI to how it is used and if optimal imaging criteria are met. In conclusion, the message is clear: adopting OCT as a guiding tool in complex PCI could be a decisive step toward elevating the quality of cardiac care and improving outcomes.

Figure 1 OCT in complex coronary lesions. Created in BioRender. Burzotta, F. (2025) https://BioRender.com/c44p351. ACS, acute coronary syndrome; CTO, chronic total occlusion; LM, left main; OCT, optical coherence tomography.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, AME Clinical Trials Review. The article has undergone external peer review.

Peer Review File: Available at https://actr.amegroups.com/article/view/10.21037/actr-24-272/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://actr.amegroups.com/article/view/10.21037/actr-24-272/coif). F Bianchini reports receiving a research grant from Abbott. F Burzotta reports receiving speaker fees from Abbott Vascular, Abiomed, Medtronic, and Terumo. The authors have no other conflicts of interest to declare.

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References

1. Mintz GS, Popma JJ, Pichard AD, et al. Limitations of angiography in the assessment of plaque distribution in coronary artery disease: a systematic study of target lesion eccentricity in 1446 lesions. Circulation 1996;93:924-31. [Crossref] [PubMed]
2. Werner N, Nickenig G, Sinning JM. Complex PCI procedures: challenges for the interventional cardiologist. Clin Res Cardiol 2018;107:64-73. [Crossref] [PubMed]
3. Zito A, Burzotta F, Aurigemma C, et al. Fractional flow reserve or OCT to guide management of complex and noncomplex angiographically intermediate coronary stenosis. Rev Esp Cardiol (Engl Ed) 2025;S1885-5857(25)00088-X.
4. Ali ZA, Landmesser U, Maehara A, et al. OCT-Guided vs Angiography-Guided Coronary Stent Implantation in Complex Lesions: An ILUMIEN IV Substudy. J Am Coll Cardiol 2024;84:368-78. [Crossref] [PubMed]
5. Romagnoli E, Burzotta F, Vergallo R, et al. Clinical impact of OCT-derived suboptimal stent implantation parameters and definitions. Eur Heart J Cardiovasc Imaging 2023;25:48-57. [Crossref] [PubMed]
6. Andreasen LN, Neghabat O, Laanmets P, et al. Unintended Deformation of Stents During Bifurcation PCI: An OCTOBER Trial Substudy. JACC Cardiovasc Interv 2024;17:1106-15. [Crossref] [PubMed]
7. Romagnoli E, Lunardi M, Burzotta F. Optical coherence tomography for optimal stent implantation: what to check? Eur Heart J 2024;45:4644-6. [Crossref] [PubMed]
8. Burzotta F, Zito A, Aurigemma C, et al. Fractional flow reserve or optical coherence tomography for angiographically intermediate coronary stenoses: 5-year outcomes in the FORZA trial. Eur Heart J 2024;45:2785-8. [Crossref] [PubMed]
9. Hamed M, Mohamed S, Mahmoud M, et al. Intravascular Imaging-Guided Versus Coronary Angiography-Guided Complex PCI: A Meta-analysis of Randomized Controlled Trials. Cardiol Ther 2024;13:379-99. [Crossref] [PubMed]
10. Mamas MA, Mintz GS. Optical coherence tomography imaging for complex percutaneous coronary intervention. Lancet 2024;404:994-5. [Crossref] [PubMed]
11. Kubo T, Shinke T, Okamura T, et al. Optical frequency domain imaging vs. intravascular ultrasound in percutaneous coronary intervention (OPINION trial): one-year angiographic and clinical results. Eur Heart J 2017;38:3139-47. [Crossref] [PubMed]
12. Kang DY, Ahn JM, Yun SC, et al. Optical Coherence Tomography-Guided or Intravascular Ultrasound-Guided Percutaneous Coronary Intervention: The OCTIVUS Randomized Clinical Trial. Circulation 2023;148:1195-206. [Crossref] [PubMed]
13. Ali ZA, Landmesser U, Maehara A, et al. Optical Coherence Tomography-Guided versus Angiography-Guided PCI. N Engl J Med 2023;389:1466-76. [Crossref] [PubMed]
14. Hong SJ, Lee SJ, Lee SH, et al. Optical coherence tomography-guided versus angiography-guided percutaneous coronary intervention for patients with complex lesions (OCCUPI): an investigator-initiated, multicentre, randomised, open-label, superiority trial in South Korea. Lancet 2024;404:1029-39. [Crossref] [PubMed]
15. Landmesser U, Ali ZA, Maehara A, et al. Optical coherence tomography predictors of clinical outcomes after stent implantation: the ILUMIEN IV trial. Eur Heart J 2024;45:4630-43. [Crossref] [PubMed]
16. Li X, Ge Z, Kan J, et al. Intravascular ultrasound-guided versus angiography-guided percutaneous coronary intervention in acute coronary syndromes (IVUS-ACS): a two-stage, multicentre, randomised trial. Lancet 2024;403:1855-65. [Crossref] [PubMed]
17. Zhang J, Gao X, Kan J, et al. Intravascular Ultrasound Versus Angiography-Guided Drug-Eluting Stent Implantation: The ULTIMATE Trial. J Am Coll Cardiol 2018;72:3126-37. [Crossref] [PubMed]
18. Vrints C, Andreotti F, Koskinas KC, et al. 2024 ESC Guidelines for the management of chronic coronary syndromes. Eur Heart J 2024;45:3415-537. [Crossref] [PubMed]
19. Onuma Y, Katagiri Y, Burzotta F, et al. Joint consensus on the use of OCT in coronary bifurcation lesions by the European and Japanese bifurcation clubs. EuroIntervention 2019;14:e1568-77. [Crossref] [PubMed]
20. Barbato E, Gallinoro E, Abdel-Wahab M, et al. Management strategies for heavily calcified coronary stenoses: an EAPCI clinical consensus statement in collaboration with the EURO4C-PCR group. Eur Heart J 2023;44:4340-56. [Crossref] [PubMed]
21. Alfonso F, Coughlan JJ, Giacoppo D, et al. Management of in-stent restenosis. EuroIntervention 2022;18:e103-23. [Crossref] [PubMed]
22. Buonpane A, Trimarchi G, Ciardetti M, et al. Optical Coherence Tomography in Myocardial Infarction Management: Enhancing Precision in Percutaneous Coronary Intervention. J Clin Med 2024;13:5791. [Crossref] [PubMed]