A common medicine used to slow the heart rate may increase the risk of serious bleeding in older people with atrial fibrillation (AFib), according to new research published in the medical journal JAMA.
AFib is the most common type of irregular heartbeat. Instead of beating in a steady rhythm, the upper chambers of the heart beat in a fast and uneven way. This can allow blood to collect inside the heart and form clots.
If a clot travels to the brain, it can block blood flow and cause a stroke. Because of this danger, many people with AFib take blood-thinning medicines every day to lower their risk of stroke.
Doctors also often prescribe medicines to slow the heart rate so the heart does not have to work as hard. Two commonly used medicines are diltiazem and metoprolol.
Both have been used for many years and can help control symptoms such as a racing heartbeat, tiredness, and shortness of breath. Even though these medicines are common, researchers wanted to know whether one choice might be safer than the other when it is taken together with blood thinners.
The research team, led by Dr. Eli Zimmerman from Northwestern University, studied health records from older adults in the United States who were covered by Medicare.
The researchers looked at people aged 65 years and older who started taking one of two widely used blood thinners, apixaban or rivaroxaban, together with either diltiazem or metoprolol between 2012 and 2020. By comparing these large groups of patients, the scientists were able to see how often serious health problems happened after treatment began.
The results showed an important difference. People who took diltiazem together with one of the blood thinners were about 20% more likely to be admitted to hospital or die because of serious bleeding than people who took metoprolol with the same blood thinners.
The researchers did not find major differences in the risk of stroke, blood clots, or other types of bleeding between the two treatment groups.
One possible reason is that diltiazem can affect how the body breaks down certain medicines. When blood thinners stay in the body for longer or reach higher levels than expected, the chance of bleeding may increase. Not every patient will have this problem, but the findings suggest that some people could be more sensitive to this combination of medicines.
The study also highlights an important idea in modern medicine. People do not all respond to medicines in the same way. Age, kidney function, liver function, other medical conditions, genes, and the number of medicines a person takes can all change how a drug works.
Older adults are especially likely to take several medicines at the same time, making drug interactions more likely. This is why doctors regularly review medicine lists and adjust treatment when needed.
Dr. Zimmerman said researchers hope to better understand why some people have a much higher bleeding risk than others. They are also studying whether checking medicine levels in the blood could help doctors choose safer doses or identify patients who need closer monitoring. More research is needed before these approaches become part of everyday care.
The findings do not mean that people should stop taking diltiazem or blood thinners on their own. For many patients, these medicines provide important benefits that outweigh the risks. Anyone with AFib who is worried about their treatment should speak with their doctor before making any changes. Suddenly stopping blood thinners can greatly increase the risk of stroke.
Heart health also depends on healthy daily habits. Keeping blood pressure under control, eating a balanced diet rich in fruits, vegetables, whole grains, and beans, staying physically active, maintaining a healthy weight, avoiding smoking, limiting alcohol, and following medical advice can all help lower the risk of heart disease.
Some people with high blood pressure may also benefit from reducing caffeine if recommended by their healthcare provider.
This study reminds us that treating heart disease is often a careful balancing act. A medicine that helps solve one problem may sometimes increase the chance of another. By understanding how medicines interact and by tailoring treatment to each patient, doctors can continue working toward safer and more effective care for people living with atrial fibrillation.
If you care about heart health, please read studies about how eating eggs can help reduce heart disease risk, and herbal supplements could harm your heart rhythm.
For more health information, please see recent studies about how drinking milk affects risks of heart disease and cancer, and results showing strawberries could help prevent Alzheimer’s disease.
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