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Introduction Patients with acute myocardial infarction (AMI) and multivessel disease are at elevated risk of recurrent events. Radial wall strain (RWS), a novel indicator derived from angiography, has emerged as a potentially useful adjunct to optical coherence tomography (OCT) for assessing plaque vulnerability. The NASCENT trial is a prospective, multicentre cohort study designed to assess the natural history of coronary plaque in this high-risk AMI population and investigate the predictive value of angiography-based RWS for lesion progression, compared with OCT-assessed vulnerable plaque.Methods and analysis Following successful culprit lesion revascularisation for AMI patients with multivessel disease, we assessed eligible non-culprit lesions (30%–80% diameter stenosis) in non-flow-limiting, non-infarct-related arteries (Murray law-based quantitative flow ratio >0.80) using OCT and offline RWS analysis. The primary endpoint is lesion progression at 1 year, defined as a ≥20% increase in diameter stenosis percentage measured by quantitative coronary angiography. Between April 2024 and April 2025, 131 patients were enrolled. The 1-year angiographic and OCT follow-ups will be completed by May 2026. Clinical follow-ups are planned at 1 month, 6 months, 1 year and annually up to 3 years. As the first prospective trial comparing angiography-based RWS with OCT for predicting lesion progression in the AMI population, this study may provide crucial evidence for RWS as a valuable tool for risk stratification and clinical decision-making.Ethics and dissemination The protocol has been approved by the Institutional Review Board and Ethics Committee (Fuwai Hospital Approval No. 2023-2039) and will be conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from all participants. The study results will undergo peer-reviewed publication.Trial registration number NCT06040073.