Left Ventricular Unloading in Anterior ST-Segment Elevation Myocardial Infarction Without Shock

Background: Despite rapid percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI), large infarcts contribute to heart failure and mortality. Left ventricular (LV) wall tension and load are major determinants of infarct size. Preclinical studies identified that delaying reperfusion to permit LV unloading with a transvalvular microaxial flow pump (TV-mAFP) reduces infarct size. We tested whether this combination reduces infarct size compared with reperfusion alone in patients with anterior STEMI without cardiogenic shock. Objectives: The STEMI-Door to Unload (DTU) pivotal trial tested the central hypothesis that the combination of mechanical LV unloading plus a 30-minute delay before PCI reduces infarct size compared with immediate PCI alone in patients with anterior STEMI without cardiogenic shock. Methods: We conducted an open-label, randomized controlled trial at 55 hospitals in the United States, Germany, Italy, United Kingdom, Switzerland, and Canada. Adults aged 18 to 85 years with no prior myocardial infarction and presenting with acute anterior STEMI within 1 to 6 hours of symptom onset before hospital arrival were eligible for inclusion. Patients were randomly assigned (1:1) by study site personnel to either LV unloading with a TV-mAFP for 30 minutes before PCI (treatment group) or PCI alone (control group). The primary outcome was infarct size normalized to LV mass (IS/LVM) evaluated by cardiac magnetic resonance imaging 3 to 5 days after PCI and was evaluated in all randomized patients. The trial is closed to new participants. Results: Between December 12, 2019 and September 3, 2024, 527 patients were randomized; 262 patients were assigned to the treatment group and 265 to the control group. Mean patient age was 61 ± 11 years, and 417 patients (79.1%) were men. Total ischemic time was longer in the treatment arm. IS/LVM was 30.8% ± 16.2% in the treatment group and 31.9% ± 16.9% in the control group (mean difference: –1.1%; 95% CI: –4.2 to 2.0; P = 0.50). Major bleeding or vascular complications at 30-day follow-up occurred more frequently in the treatment group when compared with either a prespecified performance goal or the control group. Conclusions: Combination of a TV-mAFP plus delayed PCI did not reduce infarct size in patients with anterior STEMI without cardiogenic shock compared with PCI alone.