Left ventricular thrombus is found in 10 to 25% of patients with impaired left ventricular function following ST-segment elevation myocardial infarction and up to 20% in dilated cardiomyopathy in observational studies. Likewise, the incidence of atrial thrombus among atrial fibrillation patients treated by vitamin K antagonist (VKA) is between 0.25% and 7%. Despite anticoagulant therapy, intra-cardiac thrombus remains a severe complication associated with a high risk of systemic embolism and subsequent mortality but also bleeding events related to the anticoagulation therapy. The class of non-vitamin K antagonist direct oral anticoagulant (DOA) has emerged in the last decades and has systematically surpassed VKA in the different clinical settings by providing at minimum a similar efficacy and a better safety profile. In the absence of randomized study in the specific clinical setting of intracardiac thrombus, international Guidelines recommend, on the basis of expert opinion, the use of VKA for at least 3 to 6 months in case of left ventricular thrombus and there is no specific recommendation for thrombus management from other cardiac localizations.

In comparison to VKA, the easier management and the large evidence of better safety of DOA make it an interesting anticoagulant strategy. Data for left ventricule thrombosis treatment are limited and only supported by observational cohorts. However, these recent cohorts have shown promising data in this indication reporting similar thrombus regression following DOA in comparison to VKA and similar ischemic outcomes although no head-to-head comparison would be powered.

As a consequence, the multicentric randomized ARGONAUT trial aims to confirm these results and evaluate the impact of DOA compared to VKA on thrombus regression and clinical outcomes among patients with intracardiac thrombus, regardless of the thrombus localization and any underlying heart disease.

Inclusion Criteria:

• Patient with a non-device related intra-cardiac thrombus (all localizations in the four cavities) diagnosed by echocardiography, cardiac CT-scanner or cardiac magnetic resonance imaging independently of underlying heart disease.
• Anticoagulant naïve patient for at least 3 months
• Patient affiliated to a health insurance program
• Patient that accepted not to participate in other studies involving a study medication until the one-year follow-up visit. Registries and studies not involving a study drug are allowed.
• Patient that signed the consent form

Exclusion Criteria:

• Active internal bleeding or recent (< 6 months) major bleeding event requiring surgical procedure or transfusion
• History of intracranial, intraocular, spinal bleeding or known intracranial neoplasm, arteriovenous malformation, or aneurysm
• Severe, disabling stroke (modified Rankin score of 4 to 5, inclusive) within 3 months
• Planned invasive procedure with potential for uncontrolled bleeding
• Impaired hemostasis such as known International Normalized Ratio (INR) >1.5; past or present bleeding disorder (including congenital bleeding disorders such as von Willebrand's disease or hemophilia, acquired bleeding disorders, and unexplained clinically significant bleeding disorders), thrombocytopenia (platelet count <100,000/μL)
• Severe chronic renal failure (creat. clearance<30ml/min)
• Known significant liver disease
• Device related thrombus (mechanical valve prosthesis, left atrial appendage or septal closure devices, pacemaker leads)
• Patients with mechanical valve prosthesis
• Cardiogenic shock
• Pregnancy or breast-feeding patient
• Known allergy or hypersensitivity to VKA or DOA drugs
• Inability or unwillingness to comply with study-related procedures
• Participation in another clinical research protocol with other investigational agents or devices within the previous 30 days, planned use of investigational drugs or devices, or previous enrolment in this trial (participation in a trial of routine care is authorized at the same time)
• Patient under tutorship or curatorship