Despite the fast development and popularization of reperfusion as well as adjunctive medical therapy, complications of STEMI remain critical causes of adverse events. Among them, the formation of the left ventricular thrombus (LVT) subsequent to STEMI is not rare. The incidence of STEMI-related LVT could be as higher as 31%-56% in the earlier time when thrombolysis was the mainstream of reperfusion . The risk lowers in the ear of the primary PCI, but LVT can still be detected in around 15% patients. Anterior MI is the most critical determinant of LVT. In a study including 2911 patients, 93.2% LVT occurred due to the occlusion of left artery descending (LAD). More than 2/3 of LVT was reported within the first two weeks of STEMI, late thrombus can be found in three months or even later. The existence of LVT is clearly related to increased risk of embolic events and death. In a meta-analysis in 2019, STEMI patients with LVT demonstrated a 3.97 times higher risk of embolic events than those without LVT. In a recent study, the rate of 5-year embolism in STEMI patients with LVT was up to 16.9% if without effective therapy, significantly higher than the rate of 2.9% in patients without LVT and 3% in patients with LVT but undergoing ideal therapy.

Current therapeutic guidelines recommend anticoagulant therapy for post-STEMI LVT. Since most of the LVT would be found in the acute phase of STEMI, the anticoagulant therapy is usually in addition to antiplatelet treatment. So far, Vitamin K antagonist (VKA) is still the standard medication in the treatment of LVT. The 2013 ACC/AHA guideline for STEMI management recommended adding VKA to the dual-antiplatelet regiment in patients with LVT for at least 3 months. Similarly, the 2014 ASA guideline for primary prevention of stroke gave an IIa level recommendation to use VKA adjunctive to antiplatelet medications in STEMI patients developing LVT. The treatment of VKA seems effective to both resolve LVT and decrease embolic events. In two small studies, the triple antithrombotic regimen comprising of VKA and dual antiplatelet (aspirin and clopidogrel) for 3 months resolved 88% and 92.3% LVT on echo, respectively. The addition of VKA remarkably could reduce the embolic events to 0-3% as reported in different studies.

However, the complicated titrations and the need to frequently monitor international normalized ratios (INRs) make the use of warfarin inconvenient, especially for patients who have difficulty to access medical services regularly. Therefore, the use of novel oral anticoagulants (NOACs) as a substitute for warfarin is highly attractive. However, the efficacy of NOACs in the treatment of STEMI-related LVT is not clear. Current experiences come from small series of case reports. Rivaroxaban is a potent Xa factor inhibitor. In the field of cardiology, it has become a preferred replacement of VKA in the prevention of embolic events due to the left atrial thrombus. In the X-TRA study, 15mg/QD rivaroxaban resolved 41% of left atrial thrombus. In the case of post-STEMI LVT, 15mg/QD rivaroxaban additional to dual antiplatelet therapy resolved all 4 cases of LVT in 2-4 weeks in a Cyprus study. In an American case series, 20mg /QD rivaroxaban plus one antiplatelet medication (clopidogrel) also successfully resolved LVT in 2 patients. Therefore, using NOACs to treat post-STEMI LVT is promising. The 2017 ESC guideline for STEMI management doesn't limit the choice of anticoagulation for LVT only to VKA, but the application of NOACs still needs further confirmation.

This study aims to evaluate the therapeutic efficacy and safety of rivaroxaban on the treatment of post-STEMI LVT.