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Observational Study of Cardiac Arrhythmia in Subjects Treated With BTK Inhibitors

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BTK inhibitors have revolutionized the care of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL / SLL) patients and profoundly improved outcomes. These oral medications are approved to be taken daily until the disease progresses or the drugs can no longer be tolerated. Unfortunately, intolerance is a frequent reason patients stop their meds.

Cardiac side effects, specifically atrial fibrillation and other heart rhythm abnormalities, are among the most common side effects that lead to drug discontinuation. While these cardiac side effects occur most often with ibrutinib, these problems also can be seen in the other approved BTK inhibitors, including acalabrutinib and zanubrutinib, albeit at a lower frequency.

Also, chronic lymphocytic leukemia/small lymphocytic lymphoma patients are often in their 70s, where 10% of the population has atrial fibrillation, and more have other cardiac issues.

Sorting out who is at risk for a cardiac complication while on a BTK inhibitor and the biology behind these cardiac issues is poorly understood and deserves deeper study.


In March of 2023, Dr. Emily Bryer, D.O. and colleagues at the National Institutes of Health (NIH) in Bethesda, Maryland, opened a study to investigate the cardiac side effects of BTK inhibitors, including heart rhythm abnormalities (an example being atrial fibrillation), heart failure, and sudden death. In addition, the study aims to understand how BTK inhibitors affect the heart’s structure, function, and conduction. The study is looking at patients who are 1) about to start a BTK inhibitor as well as those who are 2) already taking a BTK inhibitor. Study procedures include non-invasive cardiac tests such as EKG, exercise stress test or cardiac MRI, ambulatory cardiac monitoring, and an ultrasound of the heart.

As with all trials at the NIH, most, if not all, trial costs (except the medications in this case) should be covered.

To learn more about the trial, visit the trial listing on, identifier: NCT05724121.

Dr. Brian Koffman sat down with Dr. Emily Bryer to discuss the trial. You can watch the interview below.

Dr. Emily Bryer: Observational Study of Cardiac Arrhythmia in Patients Treated With BTK Inhibitors

If you have any questions, please contact Research Contact: Susan Soto at [email protected]

 If you are on a BTK inhibitor or are considering starting one, this is a trial worth considering.