A medicine widely used for high blood pressure and chest pain may be linked to a greater risk of sudden cardiac arrest when taken at higher doses.
Researchers found the possible risk with nifedipine, while another commonly used medicine, amlodipine, was not linked to the same increase.
Sudden cardiac arrest happens when the heart suddenly stops pumping blood effectively, usually because its normal electrical rhythm becomes dangerously disturbed. Without immediate treatment, such as CPR and an electric shock from a defibrillator when appropriate, a person can lose consciousness within seconds and die within minutes.
The condition is different from a heart attack, although a heart attack can sometimes trigger cardiac arrest. A heart attack occurs when blood flow to part of the heart is blocked, while cardiac arrest is mainly an electrical problem that causes the heart to stop pumping properly.
The research was carried out as part of the European Sudden Cardiac Arrest network, known as ESCAPE-NET. The full study was published in the peer-reviewed journal European Heart Journal – Cardiovascular Pharmacotherapy after earlier findings were presented at the European Heart Rhythm Association congress in 2019.
Researchers compared nifedipine and amlodipine, two medicines used to lower blood pressure and treat angina, or chest pain caused by reduced blood flow to the heart. Both medicines relax blood vessels, making it easier for blood to move through the body and reducing the amount of work the heart must do.
The team used large health databases from the Netherlands and Denmark. The Dutch analysis included 2,503 people who had suffered an out-of-hospital cardiac arrest and 10,543 people who had not, while the Danish analysis included 8,101 cardiac arrest patients and 40,505 comparison participants.
The researchers found that people taking nifedipine at 60 milligrams a day or more had a higher chance of out-of-hospital cardiac arrest than people who were not taking this type of medicine. The pattern appeared in both countries, which made the finding more noteworthy.
Lower doses of nifedipine were not linked to the same increased risk. Amlodipine was also not associated with a higher risk at the doses studied, suggesting that the possible problem may not apply equally to all medicines that work in a similar way.
To explore why the difference might exist, the researchers also studied human heart cells in the laboratory. They found that nifedipine could cause stronger changes in the electrical activity of heart cells at commonly used concentrations, which might make dangerous abnormal heart rhythms more likely in some people.
However, this study does not prove that high-dose nifedipine directly causes cardiac arrest. Studies that compare people using different medicines can be affected by other differences in their health, so the researchers said the results should be confirmed by further research.
The findings also do not mean that people taking nifedipine should suddenly stop their medicine. Stopping blood pressure or heart medication without medical advice can itself be dangerous, and anyone concerned about their dose or symptoms should speak with a doctor or pharmacist.
The study highlights an important challenge in medicine: even drugs that have been used for decades can still raise new safety questions when very large health databases become available. Better information about rare events such as sudden cardiac arrest may eventually help doctors choose the safest medicine and dose for each patient.
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