At three months of follow-up, patients hospitalised for a serious heart attack who were treated with the oral blood thinner rivaroxaban for a blood clot in the left ventricle did as well as similar patients who received standard treatment with warfarin, an older blood-thinning drug. This is according to findings of the RIVAWAR trial, presented during a late-breaking trial session at the 2025 American College of Cardiology (ACC) scientific session (29–31 March, Chicago, USA).
“The efficacy and safety of rivaroxaban was similar to that of warfarin in resolving left ventricular thrombus at three months follow-up,” said Jehangir Ali Shah (National Institute of Cardiovascular Diseases, Karachi, Pakistan), principal investigator for the study. “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.”
A left ventricular thrombus following a heart attack is considered a very serious complication because of the risk the clot will travel to the brain and cause a stroke or a systemic embolism. The risk for a blood clot in the left ventricle is highest in the first three months after having an ST-elevation myocardial infarction (STEMI).
Warfarin is the standard treatment for left ventricular thrombus. However, patients taking warfarin must undergo frequent blood tests to check that the time it takes for their blood to clot remains in a therapeutic range (International Normalized Ratio [INR] of 2-3).
Many other medications and foods can interact with warfarin, potentially increasing the patient’s risk for ischaemic and bleeding complications. Rivaroxaban belongs to a newer class of drugs known as direct oral anticoagulants. As its blood-thinning effects are more predictable than those of warfarin, patients taking rivaroxaban don’t need regular blood tests, and rivaroxaban is less likely than warfarin to interact with foods.
The purpose of the RIVAWAR study was to compare the effectiveness of rivaroxaban with warfarin in post-heart attack patients who developed a left ventricular thrombus.
The study enrolled 261 patients, approximately 80% were men, whose average age was 55 years. STEMIs occur more commonly in men than in women, Shah said, and the patients’ relatively young average age reflects the high burden of acute coronary syndrome in Pakistan.
Roughly 90% of the patients had had a STEMI. The patients were randomly assigned to be treated with either rivaroxaban or warfarin for three months. The study’s primary endpoint was complete dissolution of the blood clot in the left ventricle on an echocardiogram at one month and three months.
Deaths from any cause, major bleeding and rates of stroke were secondary endpoints. At one month, blood clots in the left ventricle had fully dissolved in 20.1% of the patients treated with rivaroxaban compared with 8.3% of those treated with warfarin, a statistically significant difference.
At three months, clot dissolution was comparable in both groups: 95.8% for those taking rivaroxaban, 96.6% for those taking warfarin. Results for all the secondary endpoints, which included all-cause mortality, stroke and bleeding events, were also comparable in both groups.
“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 said. “Compared with warfarin, rivaroxaban offers predictable dosing and eliminates the need for routine blood tests to monitor clotting time.”
