Efficacy of Adjunctive Use of Supersaturated Oxygen (SSO2) Therapy after Six Hours of Onset of STEMI Symptoms

Abstract

Background: ST-Elevation Myocardial Infarction (STEMI) is a critical condition managed with percutaneous coronary intervention (PCI) to restore blood flow. Despite its success in opening epicardial vessels, tissue salvage often remains suboptimal due to microvascular obstruction and reperfusion injury. Supersaturated oxygen (SSO2) therapy, approved by the FDA, has shown potential in reducing infarct size when administered within six hours of symptom onset, as demonstrated by IC-HOT and AMIHOT trials. Case: We present six cases of STEMI patients with left anterior descending (LAD) artery involvement who presented after six hours of symptom onset and received SSO2 therapy as an adjunct to PCI. All patients demonstrated improvement in left ventricular ejection fraction (LVEF) post-therapy, with no major adverse cardiovascular events (MACE), readmissions, or deaths during follow-up. Pre-procedural angiography revealed Rentrop grade 2 or 3 collaterals in five of six patients, correlating with better outcomes. Discussion: This case series highlights the potential utility of SSO2 therapy beyond the traditional six-hour window, particularly in patients with adequate collateral circulation. SSO2 may enhance myocardial perfusion by mitigating reperfusion injury and promoting capillary vasodilation. Previous trials limited to early presenters have shown promising outcomes, but this series indicates a possible role for late presenters, especially in settings with delayed PCI access. Conclusion: SSO2 therapy may provide clinical benefits for STEMI patients presenting beyond six hours, with improved LVEF and reduced complications. The presence of collaterals may allow extended preservation of injured myocardium thus enabling SSO2 to be effective even in late presenters. Larger randomized trials are needed to confirm these findings and guide future guidelines for late presenters.