The REFLO-STEMI (REperfusion Facilitated by LOcal adjunctive therapy in ST-Elevation Myocardial Infarction) trial: a randomised controlled trial comparing intracoronary administration of adenosine or sodium nitroprusside with control for attenuation of microvascular obstruction during primary percutaneous coronary intervention

Background: Microvascular obstruction (MVO) predicts short- and longer-term outcomes following primary percutaneous coronary intervention (PPCI) treatment of ST-elevation myocardial infarction (STEMI). The evidence base supporting the role of adenosine and sodium nitroprusside (SNP), the most evaluated adjunctive therapies aimed at attenuating MVO and infarct size, remains weak as the trials involved have had variable end points and used differing drug doses and modes of delivery. Objective: To determine whether intracoronary administration of adenosine or SNP following thrombus aspiration reduces infarct size and/or MVO measured by cardiac magnetic resonance (CMR) imaging in patients undergoing PPCI within 6 hours of onset of STEMI. Design: Multicentre, prospective, parallel, randomised controlled and open-label trial with blinded end point analysis. Setting: Four high-volume UK PPCI centres. Participants: Patients with STEMI undergoing PPCI with Thrombolysis in Myocardial Infarction (TIMI) flow grade 0/1 in the infarct-related artery and no significant bystander coronary artery disease on angiography. Interventions: Participants were anticoagulated with bivalirudin and allocated by an automated 24-hour telephone randomisation service to one of three groups: (1) standard PPCI (control), (2) PPCI with adjunctive adenosine 1–2 mg or (3) PPCI with adjunctive SNP 250 µg. The study drugs were delivered intracoronary immediately following thrombus aspiration and again following successful stenting. Main outcome measures: The primary outcome was infarct size (% total left ventricular end-diastolic mass; %LVM) measured by CMR imaging undertaken 48–96 hours post PPCI. Secondary outcome measures included MVO (hypoenhancement within the infarct core) on CMR imaging, electrocardiographic and angiographic markers of microvascular perfusion and major adverse cardiac events (MACEs) during a median of 6 months’ follow-up. The study aimed to recruit 240 patients (powered at 80% to detect a 5% absolute reduction in infarct size). Results: The trial completed recruitment in April 2014 having randomised 247 patients (standard PPCI group, n = 86; PPCI + adenosine group, n = 82; PPCI + SNP group, n = 79). In total, 79% of participants were male and the mean ± standard deviation age of participants was 59.3 ± 12.3 years. CMR imaging was completed in 197 (80%) patients (standard PPCI, n = 65; PPCI + adenosine, n = 63; PPCI + SNP, n = 69) for the primary outcome. There was no significant difference in infarct size [%LVM, median, interquartile range (IQR)] between the adenosine group (10.1, 4.7–16.2), the SNP group (10.0, 4.2–15.8) and the control group (8.3, 1.9–14.0) (p = 0.062 and p = 0.160 vs. control, respectively). MVO (%LVM, median, IQR) was similar across the groups [1.0, 0.0–3.7 (p = 0.205) and 0.6, 0.0–2.4 (p = 0.244) for adenosine and SNP, respectively, vs. 0.3, 0.0–2.8 for the control]. Using per-protocol analysis, infarct size (%LVM) was increased in adenosine-treated patients compared with control patients (12.0 vs. 8.3; p = 0.031). Increased left ventricular volume and reduced left ventricular ejection fraction were also observed in the adenosine arm. There was a significant increase in MACEs in patients undergoing adenosine-facilitated PPCI compared with control patients, driven by heart failure, at 30 days [hazard ratio (HR) 5.39, 95% confidence interval (CI) 1.18 to 24.60; p = 0.04] and 6 months (HR 6.53, 95% CI 1.46 to 29.2; p = 0.01) post randomisation. Conclusions: High-dose intracoronary adenosine and SNP during PPCI did not reduce infarct size or MVO measured by CMR imaging. Furthermore, adenosine may adversely affect mid-term clinical outcome and should not be used during PPCI to prevent reperfusion injury. Trial registration: ClinicalTrials.gov NCT01747174 and EudraCT 2010–023211–34. Funding: This project was funded by the Efficacy and Mechanism Evaluation (EME) programme, a MRC and NIHR partnership.