Background: In patients with acute coronary syndrome (ACS), there is residual and variable risk of recurrent ischemic events., Objectives: This study aimed to develop biomarker-based prediction models for 1-year risk of cardiovascular (CV) death and myocardial infarction (MI) in patients with ACS undergoing percutaneous coronary intervention., Methods: We included 10,713 patients from the PLATO (A Comparison of Ticagrelor [AZD6140] and Clopidogrel in Patients With Acute Coronary Syndrome) trial in the development cohort and externally validated in 3,508 patients from the TRACER (Thrombin Receptor Antagonist for Clinical Event Reduction in Acute Coronary Syndrome) trial. Variables contributing to risk of CV death/MI were assessed using Cox regression models, and a score was derived using subsets of variables approximating the full model., Results: There were 632 and 190 episodes of CV death/MI in the development and validation cohorts. The most important predictors of CV death/MI were the biomarkers, growth differentiation factor 15, and N-terminal pro-B-type natriuretic peptide, which had greater prognostic value than all candidate variables. The final model included 8 items: age (A), biomarkers (B) (growth differentiation factor 15 and N-terminal pro-B-type natriuretic peptide), and clinical variables (C) (extent of coronary artery disease, previous vascular disease, Killip class, ACS type, P2Y 12 inhibitor). The model, named ABC-ACS ischemia, was well calibrated and showed good discriminatory ability for 1-year risk of CV death/MI with C-indices of 0.71 and 0.72 in the development and validation cohorts, respectively. For CV death, the score performed better, with C-indices of 0.80 and 0.84 in the development and validation cohorts, respectively., Conclusions: An 8-item score for the prediction of CV death/MI was developed and validated for patients with ACS undergoing percutaneous coronary intervention. The ABC-ACS ischemia score showed good calibration and discrimination and might be useful for risk prediction and decision support in patients with ACS. (A Comparison of Ticagrelor [AZD6140] and Clopidogrel in Patients With Acute Coronary Syndrome [PLATO]; NCT00391872; Trial to Assess the Effects of Vorapaxar [SCH 530348; MK-5348] in Preventing Heart Attack and Stroke in Participants With Acute Coronary Syndrome [TRACER]; NCT00527943)., Competing Interests: Funding Support and Author Disclosures Grants from The Swedish Foundation for Strategic Research (grant number RB13-0197) supported this project. The PLATO trial was funded by AstraZeneca, Cambridge, United Kingdom. The TRACER trial was funded by Merck, Kenilworth, New Jersey, USA. Roche Diagnostics, Rotkreuz, Switzerland, provided GDF-15 assays free of charge. The funding sources had no influence on the work but were given the opportunity to review the final version of the report. Dr Batra has received institutional research grants from Pfizer; has received expert committee and consulting fees to his institution from Bayer; and has received honoraria for lectures and scientific advice from AstraZeneca, Boehringer Ingelheim, Novo Nordisk, Pfizer, and Sanofi. Dr Lindbäck has received institutional research grants from GlaxoSmithKline. Dr Becker has participated on a Data Safety Monitoring Board (DSMB) for Ionis and Novartis; serves on the scientific advisory board for Basking; and has received payment for expert testimony from Plunkett and Cooney. Dr Harrington has received institutional research grants from AstraZeneca during the conduct of the study; has received research grants from Janssen; and has received consulting fees from Bristol Myers Squibb. Dr Held has received institutional research grants from GlaxoSmithKline; has received honoraria and research grants from Pfizer; and has received consultant and Advisory Board fees from AstraZeneca, Bayer, Boehringer Ingelheim, and Coala Life. Dr James has received an institutional research grant, honoraria, and consultant/advisory board fee from AstraZeneca; has received an institutional research grant and consultant/advisory board fee from Medtronic; has received institutional research grants and honoraria from The Medicines Company; and has received consultant/advisory board fees from Janssen, Bayer, Novartis, Amgen, and PhaseBio. Dr Kempf has patents related to GDF-15 that have been licensed to Roche Diagnostics. Dr Lopes has received institutional research grants and consulting fees from Bayer, Bristol Myers Squibb, GlaxoSmithKline, Medtronic, Pfizer, and Sanofi; and has received consulting fees from Boehringer Ingelheim, Daiichi-Sankyo, Merck, and Portola. Dr Mahaffey has received grants and consulting fees from and participation on a DSMB for AstraZeneca and Johnson & Johnson; has received grants and consulting fees from Amgen, Bayer, Novartis, and Sanofi; has received consulting fees and speaker honoraria from Inova, Intermountain Health, Medscape, and Mount Sinai; has received grants and participation on a DSMB for Ferring, Luitpold, and Sanifit; has received consulting fees and participation on a DSMB for Myokardia and Theravance; has received grants from Afferent, American Heart Association, Apple Inc, Cardiva Medical Inc, Eidos, Gilead, Google (Verily), Medtronic, Merck, and St. Jude; has received consulting fees from Anthos Applied Therapeutics, CSL Behring, Elsevier, Mundi Pharma, Novo Nordisk, Otsuka, Portola, and SmartMedics; and participates on a DSMB for National Health and Medical Research Council and The George Institute for Global Health, Australia. Dr Steg has received grants and speaker/consultancy fees from Amarin, Bayer, Sanofi, and Servier; and has received speaker/consultancy fees from AstraZeneca, Amgen, Amarin, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Idorsia, Janssen, Novartis, Pfizer, and Regeneron. Dr Storey has received institutional research grants and speaker/consultancy fees from AstraZeneca, Cytosorbents, GlyCardial Diagnostics, and Thromboserin; and has received speaker/consultancy fees from Alnylam, Bayer, Bristol Myers Squibb/Pfizer, Chiesi, CSL-Behring, Hengrui, Idorsia, Intas Pharmaceuticals, Medscape, Novartis, PhaseBio, Portola, and Sanofi. Dr Wollert has received patents related to GDF-15 that have been licensed to Roche Diagnostics. Dr Siegbahn has received institutional research grants from AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb/Pfizer, GlaxoSmithKline, and Roche Diagnostics; and has received consulting fees from OLINK Proteomics. Dr Wallentin has received institutional research grants from AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb/Pfizer, GlaxoSmithKline, Merck & Co, and Roche Diagnostics; has received consulting fees from Abbott; and has patents related to GDF-15 that have been licensed to Roche Diagnostics. Dr Swahn has reported that she has no relationships relevant to the contents of this paper to disclose., (Copyright © 2022 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)