Angiography-Derived Physiological Indices for Outcome Prediction in Patients Undergoing OCT-Guided PCI

Prognostic Value of Angiography-Derived Physiological Indices in Patients Undergoing OCT-Guided Percutaneous Coronary Intervention

The primary design of this study is an ambispective observational cohort study. In patients undergoing successful optical coherence tomography (OCT)-guided percutaneous coronary intervention (PCI) with post-procedural angiographic images suitable for computational analysis, this study aims to evaluate the prognostic value of post-PCI angiography-derived physiological indices, specifically angiography-derived fractional flow reserve (Angio-FFR) and angiography-derived index of microcirculatory resistance (Angio-IMR), beyond conventional clinical risk factors and OCT-derived anatomical parameters. Specifically, the objectives are:

1. To determine the associations of post-PCI Angio-FFR and Angio-IMR with the risk of Major Adverse Cardiovascular Events (MACE) during follow-up.
2. To evaluate the incremental prognostic value of post-PCI Angio-FFR and Angio-IMR when added to models incorporating baseline clinical characteristics and OCT-derived anatomical parameters for predicting MACE.
3. To assess whether the combined evaluation of Angio-FFR and Angio-IMR improves identification of residual risk after anatomically optimized, OCT-guided PCI.

Optical coherence tomography (OCT) provides high-resolution intravascular imaging and enables detailed assessment of stent expansion, stent apposition, and edge-related complications, making it an important tool for optimizing PCI in complex coronary lesions. Contemporary guidelines support intravascular imaging-guided PCI, and OCT-guided PCI has improved the anatomical quality of stent implantation compared with angiography-guided procedures. Nevertheless, adverse cardiovascular events continue to occur in a proportion of patients despite apparently successful OCT-guided PCI, suggesting that anatomical optimization alone may not fully eliminate post-procedural risk.

The final physiological result after PCI is determined not only by the local anatomical result within the treated segment but also by residual diffuse epicardial disease and the status of the coronary microcirculation. Previous studies have shown that residual ischemia and microvascular dysfunction may persist even after angiographically successful PCI. Because OCT primarily evaluates epicardial structural features, it cannot directly assess global physiological reserve or microvascular function. These unrecognized functional abnormalities may therefore represent an important source of residual risk after otherwise anatomically optimized PCI.

Pre-procedural physiologic characterization may further improve understanding of this residual risk. Pullback pressure gradient (PPG) quantifies the longitudinal pattern of coronary pressure loss and helps distinguish focal from diffuse epicardial disease. Lower PPG values suggest a more diffuse disease pattern, in which anatomically successful PCI may still yield limited physiological improvement because pressure loss is distributed along the vessel rather than concentrated at a focal stenosis. By contrast, higher PPG values are more consistent with focal disease and a greater potential for physiological recovery after PCI. Accordingly, pre-PCI PPG may provide complementary baseline information for interpreting residual ischemia after anatomically optimized PCI.

In this context, post-PCI functional assessment may provide clinically relevant complementary information. Angiography-derived fractional flow reserve (Angio-FFR) enables physiological assessment of the epicardial coronary circulation, whereas angiography-derived index of microcirculatory resistance (Angio-IMR) provides an estimate of coronary microvascular function. Both indices can be derived from routine post-procedural angiographic images without additional pressure-wire manipulation or pharmacologically induced hyperemia. In general PCI populations, lower post-PCI physiological values and higher microvascular resistance have been associated with worse clinical outcomes, supporting a complementary rather than competitive relationship between anatomical and physiological assessment.

Nevertheless, the applicability of these findings to patients undergoing OCT-guided PCI remains uncertain. Compared with conventional angiography-guided or mixed PCI cohorts, patients selected for OCT-guided PCI often have more complex lesion characteristics and may achieve a higher level of stent optimization. Accordingly, the distribution, composition, and prognostic relevance of residual functional abnormalities may differ in this specific population. More importantly, it has not been directly established whether Angio-FFR and Angio-IMR continue to provide incremental prognostic information after OCT-defined anatomical optimization has been achieved, whether Angio-IMR offers additional value beyond Angio-FFR in this setting, or whether pre-PCI PPG provides complementary information for identifying patients at risk of suboptimal physiological recovery.

Therefore, this study is designed as a multicenter, ambispective observational cohort study led by the National Clinical Research Center for Cardiovascular Diseases and conducted across multiple collaborating centers in China, integrating retrospective and prospective cohorts of patients undergoing successful OCT-guided PCI. Post-procedural Angio-FFR and Angio-IMR will be derived from angiographic images suitable for computational analysis, and their prognostic value will be evaluated in conjunction with baseline clinical characteristics and OCT-derived anatomical parameters. Pre-PCI PPG will also be explored as an adjunctive baseline physiological marker in multivariable analyses. The primary outcome is Major Adverse Cardiovascular Events (MACE), defined as a composite of all-cause death, spontaneous target-vessel myocardial infarction, ischemia-driven target-vessel revascularization, hospitalization for unstable angina, and hospitalization for heart failure. All enrolled patients will undergo a minimum of 24 months of follow-up. By systematically assessing the incremental prognostic value of post-PCI Angio-FFR and Angio-IMR, while exploring the complementary contribution of pre-PCI PPG, this study aims to provide an evidence base for refined risk stratification and individualized post-PCI management after OCT-guided PCI.

Inclusion Criteria:-1.Age >= 18 years and < 85 years. 2.Successful stent implantation under OCT guidance. 3.Availability of at least two optimal post-PCI angiographic projections separated by > 25 degrees and suitable for angiography-derived physiological analysis.

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Exclusion Criteria:1.PCI of the culprit vessel for ST-segment elevation myocardial infarction (STEMI).

2.Cardiogenic shock or requirement for mechanical circulatory support. 3.Life expectancy of less than 1 year. 4.History of coronary artery bypass grafting (CABG). 5.Balloon angioplasty without stent implantation. 6.Severe procedural complications, including intraprocedural death, emergency CABG, or coronary perforation.

7.Target-vessel diameter < 2.5 mm. 8.Heart failure with New York Heart Association (NYHA) class III-IV symptoms or left ventricular ejection fraction (LVEF) < 30%.

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