Impact of Loading Doses of Direct Oral Anticoagulants on Left Ventricular and Left Atrial Thrombus: The LOAD-LVT Study.

Background Left ventricular (LV) and left atrial (LA) thrombi are associated with significant thromboembolic risk, particularly in the context of myocardial infarction and atrial fibrillation. While direct oral anticoagulants (DOACs) are recognized as alternatives to warfarin, current studies have not evaluated the utility of loading doses, as routinely used in venous thromboembolism (VTE). The LOAD-LVT study aims to determine whether loading doses of apixaban or rivaroxaban influence bleeding risk, thromboembolic events, or thrombus resolution. Methods and results A multicenter retrospective cohort study of adult patients with confirmed LV or LA thrombus treated with apixaban or rivaroxaban at five Ascension hospitals in Texas between January 2017 and November 2024 was conducted. Patients were categorized into two groups: receiving a DOAC loading dose (apixaban 10 mg twice daily for seven days or rivaroxaban 15 mg twice daily for 21 days) and receiving standard or renal-adjusted dosing. The primary outcome was the incidence of major and non-major bleeding events. Secondary outcomes included thromboembolic events and thrombus resolution on follow-up imaging at three and six months. A total of 135 patients were included; 23 (17%) received a loading dose. No major bleeding or thromboembolic events were observed in either group. Non-major bleeding occurred in 9% of patients in the loading group versus 4.5% in the standard group (p = 0.404). Of the 135 patients analyzed, 34.8% in the loading dose group and 33.9% in the standard dose group had follow-up imaging. Among those with repeat imaging, complete resolution was documented in 75% of the patients in the loading dose group compared to 86.8% in the standard dose group (p = 0.807). No significant differences were observed in time to thrombus resolution or outcomes by subgroup. Conclusion In this retrospective multicenter cohort study, no significant conclusions could be made regarding loading doses of DOACs vs. standard dosing in assessing thrombus resolution or bleeding in patients with LV or LA thrombus. The optimal dosing strategy remains uncertain and should be further evaluated in prospective, randomized trials designed to assess clinical outcomes such as embolic events, bleeding, and thrombus resolution to answer this important and understudied clinical question.