Rivaroxaban comparable to warfarin in left ventricular blood clots

At three months of follow-up, patients hospitalized 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. The findings were presented at the American College of Cardiology’s Annual Scientific Session (ACC.25).

“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, MBBS, an associate professor at the National Institute of Cardiovascular Diseases in Karachi, Pakistan, and 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 clot can also travel to the heart, lungs, kidney, liver, spleen or limbs, causing ischemia (reduced blood flow) and potential damage––all potentially fatal events, Shah said. The risk for a blood clot in the left ventricle, the heart’s main pumping chamber, is highest in the first three months after having a serious heart attack known as 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 (an INR, International Normalized Ratio, of 2-3). Many other medications and foods can interact with warfarin, potentially increasing the patient’s risk for ischemic 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 current study, known as RIVAWAR, 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 (a group of conditions caused by sudden, reduced blood flow to the heart) in Pakistan.

Roughly 90% of the patients had had a STEMI, the most serious and life-threatening type of heart attack, in which one of the main arteries carrying blood to the heart becomes totally blocked. About 94% had a condition in which less than half of the blood in the left ventricle is pumped out with each heartbeat. About 85% were treated with coronary angioplasty, which involves placing tiny tubes called stents into blocked coronary arteries to prop them open.

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.”

The study is limited in that it was conducted at a single institution in Karachi, Pakistan. It was also “open label,” meaning that both patients and their clinicians knew who was receiving which treatment. Due to a lack of funding, follow-up ended after three months, with no long-term way to track recurrence of left ventricular thrombus after the study treatment was discontinued.

ACC.25 will take place March 29-31, 2025, in Chicago, bringing together cardiologists and cardiovascular specialists from around the world to share the newest discoveries in treatment and prevention. Follow @ACCinTouch, @ACCMediaCenter and #ACC25 for the latest news from the meeting.

The American College of Cardiology (ACC) is the global leader in transforming cardiovascular care and improving heart health for all. As the preeminent source of professional medical education for the entire cardiovascular care team since 1949, ACC credentials cardiovascular professionals in over 140 countries who meet stringent qualifications and leads in the formation of health policy, standards and guidelines. Through its world-renowned family of JACC Journals, NCDR registries, ACC Accreditation Services, global network of Member Sections, CardioSmart patient resources and more, the College is committed to ensuring a world where science, knowledge and innovation optimize patient care and outcomes. Learn more at ACC.org.

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Shah will be available to the media in a press conference on Saturday, March 29, at 7 a.m. CT / 12:00 UTC in Room N226.

Shah will present the study, “Efficacy of Rivaroxaban Versus Warfarin in Patients with Acute Left Ventricular Thrombus Following Myocardial Infarction: An Open-label Randomized Controlled Trial,” on Saturday, March 29, 2025, at 11:30 a.m. CT / 16:30 UTC in Main Tent.

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