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Cosmos Study

AFib Patients on Direct Oral Anticoagulant Medications Have Lower Rates of Stroke and Embolism Than Those on Warfarin

August 27, 2024
Dual-Team Study
Team A:Kersten Bartelt, RNEric Barkley
Team B:Dave Little, MDOwen Torczon

Key Findings

  • Patients with atrial fibrillation (AFib) who are prescribed direct oral anticoagulants (DOACs) have lower rates of ischemic stroke, hemorrhagic stroke, arterial embolism, and pulmonary embolism compared to those treated with warfarin. 

We recently published findings that the rates of ischemic stroke, transient ischemic attack (TIA), and hemorrhagic stroke among atrial fibrillation (AFib) patients are similar for those treated with a left atrial appendage closure (LAAC) procedure alone, an LAAC with anticoagulation, or anticoagulation alone.1 However, we did not differentiate between different types of anticoagulant medications and wanted to better understand whether specific anticoagulant treatments are associated with stroke, TIA, embolism, or major bleeding events.  

We studied 323,256 patients with AFib who were treated with warfarin, rivaroxaban, apixaban, or dabigatran. Patients with a history of an LAAC procedure, heart valve problems, congestive heart failure, heart attack, ischemic stroke, TIA, hemorrhagic stroke, major bleeding, arterial embolism, pulmonary embolism, or end stage renal disease were excluded from the analysis. 

We found that patients treated with rivaroxaban or apixaban had a lower rate of ischemic stroke and TIA within five years of treatment than patients treated with warfarin or dabigatran. Hemorrhagic stroke was the least common of the outcomes studied. However, patients treated with warfarin had a higher rate of hemorrhagic stroke in the five years after starting treatment than patients on any of the other anticoagulants studied. 

Figure 1
Five-Year Stroke Rate After Start of Treatment for AFib
Five-Year Stroke Rate After Start of Treatment for AFib
Figure 1. The rate of AFib patients experiencing a stroke or TIA within five years after treatment start.

Because a primary indication for anticoagulant use is the prevention of blood clots, we analyzed the rate of pulmonary and arterial embolism five years after the start of anticoagulation treatment. Pulmonary embolism occurred in less than 3% of the population, and arterial embolism was even less prevalent, diagnosed in less than 2% of the population. However, patients prescribed warfarin had the highest rate of both outcomes compared to the other anticoagulants studied. 

Figure 2
Five-Year Embolism Rate After Start of Treatment for AFib
Five-Year Embolism Rate After Start of Treatment for AFib
Figure 2. The rate of AFib patients experiencing an embolism within five years after treatment start.

We also examined the rate of a major bleeding event among AFib patients within five years of starting anticoagulant treatment. We found that this event occurred in less than 2% of patients, with patients treated with dabigatran experiencing the lowest rate of major bleeding events. 

Figure 3
Five-Year Major Bleeding Rate After Start of Treatment for AFib
Five-Year Major Bleeding Rate After Start of Treatment for AFib
Figure 3. The rate of AFib patients experiencing a major bleeding event within five years after treatment start. 

These data come from Cosmos, a dataset created in collaboration with a community of Epic health systems representing more than 270 million patient records from 1,500 hospitals and more than 35,500 clinics from all 50 states and Lebanon. This study was completed by two teams that worked independently, each composed of a clinician and research scientists. The two teams came to similar conclusions. Graphics by Brian Olson. 

References

  1. Little D, Tapper J, Barkley E, Bartelt K, Piff A. Left Atrial Appendage Closure Comparable to Anticoagulants for Ischemic Stroke and TIA Prevention in Atrial Fibrillation Patients. Epic Research. https://epicresearch.org/articles/left-atrial-appendage-closure-comparable-to-anticoagulants-for-ischemic-stroke-and-tia-prevention-in-atrial-fibrillation-patients. Accessed on July 15, 2024.