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Reperfusion Injury and Infarct Size: Why Translation has Been Difficult, and How We Move Forward
Heerajnarain Bulluck1,2,3, Derek J Hausenloy4,5,6,7
1Department of Cardiology, Leeds General Infirmary, Leeds, UK.
Purpose Of Review:
To evaluate the reasons underlying the translational failure of cardioprotection in reperfused ST-elevation myocardial infarction (STEMI) and propose a framework for designing future clinical cardioprotection trials.
Recent Findings:
The 2024 JACC Scientific Statement on reperfusion injury reframed the field as a network of interrelated injury pathways but stopped short of providing a clinically actionable framework. Contemporary cardioprotection trials in enriched patient STEMI cohorts have produced largely neutral results: STEMI-DTU, PiCSO-AMI-I, EURO-ICE, and COOL AMI EU failed to demonstrate cardioprotection on cardiovascular magnetic resonance (CMR) infarct size. Although the PITRI trial showed reduced periprocedural platelet reactivity with cangrelor there was no reduction in infarct size or microvascular obstruction (MVO), exemplifying proximal target engagement without affecting imaging surrogates. In contrast, the supersaturated oxygen (SSO₂) programme arc - AMIHOT → AMIHOT-II → IC-HOT → IC-HOT-MICRO - showed progressive patient enrichment yielding a progressive mechanistic signal, particularly in patients with severe coronary microvascular dysfunction. The Collaborative Registry on CMR in STEMI confirmed MVO ≥ 2.6% of left ventricular mass as an independent predictor of heart failure hospitalisation and all-cause death. The EU-CARDIOPROTECTION IMPACT criteria provide a preclinical standard for clinical translation. Translational failure of cardioprotection reflects misalignment between heterogeneous biology and trial design, not biological irrelevance. A biological ceiling cannot be excluded but is unlikely to be the dominant barrier. The path forward is to align patient selection, phenotype-specific endpoints, and adaptive trial architecture, and to test mechanical interventions together with pharmacological adjuncts rather than in isolation. When these elements are aligned - as the SSO₂ programme arc suggests - cardioprotection in STEMI may yet deliver clinically meaningful benefit.
Insights
Cardioprotection trials in ST-elevation myocardial infarction (STEMI) have largely failed due to misaligned trial designs and patient selection. Future trials need improved patient stratification and adaptive designs to achieve meaningful clinical benefits.
Area of Science:
- Cardiology
- Translational Medicine
- Clinical Trial Design
Background:
- Reperfusion injury in ST-elevation myocardial infarction (STEMI) is a complex network of pathways.
- Contemporary cardioprotection trials in STEMI have yielded largely neutral results, failing to demonstrate significant infarct size reduction.
- Existing frameworks lack clinical actionability, hindering effective trial design.
Purpose of the Study:
- To identify reasons for the translational failure of cardioprotection in STEMI.
- To propose a framework for designing future, more successful cardioprotection trials.
- To re-evaluate the biological relevance versus trial design in cardioprotection research.
Main Methods:
- Review of recent scientific statements and contemporary clinical trials in STEMI cardioprotection.
- Analysis of trial outcomes, including infarct size and microvascular obstruction (MVO) via cardiovascular magnetic resonance (CMR).
- Evaluation of patient enrichment strategies and preclinical standards for clinical translation.
Main Results:
- Trials like STEMI-DTU, PiCSO-AMI-I, EURO-ICE, and COOL AMI EU showed no significant cardioprotective effects on infarct size.
- The supersaturated oxygen (SSO₂) program demonstrated progressive benefits with patient enrichment, especially in those with severe coronary microvascular dysfunction.
- Microvascular obstruction (MVO) ≥ 2.6% of left ventricular mass is a predictor of adverse outcomes in STEMI patients.
Conclusions:
- Translational failure stems from misalignment between heterogeneous STEMI biology and trial design, not biological irrelevance.
- Future trials require aligned patient selection, phenotype-specific endpoints, and adaptive architectures.
- Combining mechanical interventions with pharmacological adjuncts and employing enriched cohorts may unlock clinical benefits in STEMI cardioprotection.
