The main goal of this study is to compare two treatments in patients with a specific type of heart attack called Non-ST-elevation Myocardial Infarction (NSTEMI). The investigators want to find out whether using aspirin alone is as effective and safer than using aspirin together with a second blood thinner called fondaparinux. Both treatments will be given before a scheduled heart procedure called coronary angiography (CAG), which may include balloon dilation and stent placement (PCI) if needed. The current guidelines recommend using aspirin in combination with a second blood thinner like fondaparinux before CAG and possible PCI. However, these recommendations are based on studies from the 1990s, a time when invasive procedures were not standard practice for these patients. In contrast, nearly all patients with NSTEMI in Denmark (96%) now undergo CAG within 72 hours. This change in practice raises questions about whether the older studies still provide a valid foundation for today's guidelines. The study aims to answer two questions: 1. Is aspirin alone as effective as aspirin combined with fondaparinux before early CAG and possible PCI? 2. Is aspirin alone safer, with a lower risk of severe bleeding, compared to the combination treatment? To answer these questions, the investigators will enroll about 5,000 patients with NSTEMI. Participants will be randomly assigned to receive either aspirin alone or aspirin with fondaparinux. The investigators will monitor them for 30 days to compare outcomes such as death, new heart attacks, the need for urgent CAG before the scheduled, and severe bleeding.