RIVAWAR: Rivaroxaban Akin to Warfarin for Left Ventricular Thrombus After MI

Rivaroxaban achieved comparable efficacy and safety to warfarin in resolving left ventricular blood clots in patients hospitalized with myocardial infarction (MI) without displaying evidence of excess harm, including mortality and bleeding risks.1

The open-label, non-inferiority, randomized controlled RIVAWAR trial, presented at the American College of Cardiology (ACC) 2025 Annual Scientific Sessions, enrolled 261 patients in Pakistan to treatment with rivaroxaban or warfarin for three months, seeking the complete dissolution of the blood clot in the left ventricle.

“The efficacy and safety of rivaroxaban was similar to that of warfarin in resolving left ventricular thrombus (LVT) at three months follow-up,” said Jehangir Ali Shah, MBBS, an associate professor at the National Institute of Cardiovascular Diseases in Pakistan, and primary investigator of RIVAWAR. “We saw complete resolution of blood clots in more than 95% of patients in both groups, with no evidence of excess deaths, ischemic stroke, or major bleeding.”

LVT after MI can be dangerous, with the risk for the clot to travel to the brain and lead to a stroke or systemic embolism. The clot could also travel to the heart, lungs, kidney, liver, spleen, or limbs, leading to ischemic and potentially fatal damage, with the risk highest in the first three months after the event.

The standard treatment for LVT involves Vitamin K antagonists (VKAs), including warfarin, which requires frequent blood test monitoring. Concomitant medication use and diet interactions can impact anticoagulation. Shah and colleagues pointed to non-VKA oral anticoagulants (NOACs) as a potential alternative treatment option for LVT.

Direct oral anticoagulants (DOACs), including rivaroxaban, offer more predictable blood-thinning effects, making regular blood tests unnecessary and less likely to interact with diet than warfarin. RIVAWAR sought to measure the effectiveness of rivaroxaban versus warfarin in a patient population who had recently had an MI and developed LVT.

Approximately 80% of the study population were men with an average age of 55. As ST elevation MI (STEMIs) occur more frequently in men than women, Shah and colleagues noted the population’s young average age was an indication of the high burden of acute coronary syndrome (ACS) in Pakistan. Most patients had STEMI (~90%) and underwent angioplasty (~85%).

Investigators measured the primary endpoint, the complete dissolution of the blood clot in the left ventricle, on an echocardiogram at one month and three months. Secondary endpoints included death from any cause, major bleeding, and the rates of stroke.

Severe left ventricular dysfunction (left ventricular ejection fraction [LVEF] ≤35%) was identified in 93.6% of the rivaroxaban group, compared with 94.4% of the warfarin group. Upon analysis, LVT resolution had been achieved at one month in 20.1% of the rivaroxaban cohort, compared with 8.3% in the warfarin cohort (P =.017). Similar clot dissolution was identified in both groups at 3 months (95.8% vs. 96.6%; P =.759).

Further analysis revealed comparable results for the secondary endpoints, including all-cause mortality, stroke, and bleeding events. Cumulative all-cause mortality occurred in 5.3% of the rivaroxaban group vs. 5.6% in the warfarin group (P =.921), while major bleeding occurred in 2.3% vs. 1.1% (P =.491) and ischemic stroke in 3% vs. 1.1% (P =.254), respectively.

Shah and colleagues noted these data were limited by the single-center study design, as well as a lack of funding, which halted the study after three months of follow-up. As a result, the team indicated there was no long-term tracking of the recurrence of LVT after the study treatment was discontinued.

“These findings support the use of rivaroxaban as a viable alternative to warfarin for the treatment of left ventricular thrombus in post-heart attack patients,” Shah added. “Compared with warfarin, rivaroxaban offers predictable dosing and eliminates the need for routine blood tests to monitor clotting time.”

References

1. Shah JA, Hussain J, Ahmed B, Kumar M, et al. Efficacy Of Rivaroxaban Versus Warfarin In Patients With Acute Left Ventricular Thrombus Following Myocardial Infarction: An Open-label Randomized Controlled Trial RIVAWAR Trial Investigators. Presented at: American College of Cardiology (ACC.25) Annual Scientific Session. March 29 – 31, 2025. Chicago, Il.

2. Rivaroxaban comparable to warfarin in left ventricular blood clots. American College of Cardiology. March 29, 2025. Accessed April 4, 2025. https://www.acc.org/About-ACC/Press-Releases/2025/03/29/15/34/Rivaroxaban-Comparable-to-Warfarin.