Treatment of Slow-flow After Primary Percutaneous Coronary Intervention With Flow-mediated Hyperemia. The Randomized RAIN-FLOW Study

Background ST-segment Elevation Myocardial Infarction (STEMI) complicated with no reflow after primary percutaneous coronary intervention is associated with adverse outcomes. Although several hyperemic drugs have shown to improve the Thrombolysis In Myocardial Infarction (TIMI) flow, optimal treatment of no reflow remains unsettled. Saline infusion at 20 ml/min via a dedicated microcatheter causes (flow-mediated) hyperemia. The objective is to compare the efficacy of pharmacologic vs . flow-mediated hyperemia in STEMI patients complicated with no reflow. Methods STEMI patients with no reflow were randomized to receive either adenosine or nitroprusside vs . flow-mediated hyperemia. The angiographic corrected TIMI Frame Count (cTFC) and the Minimal Microcirculatory Resistance (MMR), as assessed with intracoronary pressure-thermistor wire, dedicated microcatheter and thermodilution techniques, were compared after study interventions. Results Sixty-seven were included (30 allocated to pharmacologic and 37 to flow-mediated hyperemia). After study interventions, cTFC (40.2±23.1 vs . 39.2±20.7; p=0.858) and MMR (753.6±661.5 vs . 993.3±740.8 Wood units; p=0.174) were similar between groups. TIMI 3 flow was observed in 26.7% vs . 27.0% (p=0.899). Flow-mediated hyperemia showed two different thermodilution patterns during saline infusion indicative of the severity of the no reflow phenomenon. In-hospital death and non-fatal heart failure were observed in 10.4% and 26.9%, respectively. Conclusions Both treatments showed similar (and limited) efficacy restoring coronary flow. Flow-mediated hyperemia with thermodilution pattern assessment allowed the simultaneous characterization of the no reflow degree and response to hyperemia. No reflow was associated with a high rate of adverse outcomes. Further research is warranted to prevent and to treat no reflow in STEMI patients ([NCT04685941][1]). ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial NCT04685941 ### Funding Statement The RAIN-FLOW study received an unrestricted grant from Hexacath (Paris, France) and was promoted by the EPIC (Educación en Procedimientos de Intervencionismo en Cardiología) Foundation. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee of the Bellvitge University Hospital I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All authors have access to the data of the study. * ACBF : absolute coronary blood flow cTFC : corrected TIMI frame count MMR : minimal microcirculatory resistance PPCI : Primary percutaneous coronary intervention STEMI : ST-segment elevation myocardial infarction TIMI : Thrombolysis In Myocardial Infarction [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04685941&atom=%2Fmedrxiv%2Fearly%2F2023%2F02%2F24%2F2023.02.21.23286266.atom