Joanna Mulvaney PhD , 2025-11-13 15:00:00
Everybody knows that over caffeinating can send your pulse racing, so it’s no surprise that doctors usually advise people with heart problems and high blood pressure to steer clear of coffee. Is it true for all heart conditions? According to a team of San Francisco heart doctors, perhaps not. UCSF cardiologists tentatively suggest that when it comes to atrial fibrillation or flutter, for some patients, not only does coffee do no harm, it might even help. Don’t open your Starbucks app just yet, let us walk you through the results so you can get the most out of talking it through with your doctor.
Coffee doesn’t cause atrial fibrillation
In a paper published November 7th 2025, in JAMA, UCSF cardiologists report results from the DECAF clinical trial that shows that coffee might not be as bad for atrial fibrillation and atrial flutter patients as they thought. This open label randomized controlled study followed 200 patients who had had cardioversion to fix atrial fibrillation or flutter. They discovered that a cup of coffee each day reduced the risk of an episode by 40% over six months.
There are some caveats to this. Firstly the main take away is that if you are already a coffee drinker, a daily coffee does not trigger atrial fibrillation. Coffee drinkers were not more likely to have a relapse than coffee abstainers. As far as preventing a recurrance… It’s not a huge change.
The coffee drinkers had a 47% chance versus the abstainers, who had a 64% chance of a flutter or fibrillation. While the trial was randomized and controlled, the participants were aware of whether they were drinking coffee and not all of the abstainers were as abstinent as they intended to be. The participants reported coffee or caffeine consumption through questionaires so there is a chance a few fibs or “misrememberings” slipped by…
There was also the placebo effect – some participants strongly believed that coffee would trigger an attack, so coffee drinkers might have been more likely to notice changes in how they felt. Other coffee connoisseurs might convince themselves they were feeling better than they were. Read on to find out how the researchers tried to minimize these effects and how they judged whether or not coffee was harmful.
Atrial fibrillation is a type of arrhythmia
So what is atrial fibrillation anyway? It’s an abnormal heart rhythm – an arrhythmia. Our heart is a pump with four chambers that pull blood in and push it out by squeezing and relaxing. That ba-dum ba-dum rhythm of your heart beat? That’s the sound of the top two partitions pumping blood into your heart followed by the bottom two chambers pushing blood out into your body. The atria are the top two chambers. They are responsible for pulling in blood.
Normally, your atrial chambers beat between 60 and 100 times per minute. In a person with atrial fibrillation, the way the atrial chambers contract to pump blood becomes chaotic. The heart will start beating much faster, up to 170 bpm at rest or in an abnormal rhythm to try to help get the blood flowing around.
Atrial fibrillation is a chronic condition that can come and go. Sometimes the abnormal rhythm is fleeting; other times it might be a permanent change. Somebody with an atrial flutter will experience their atria beating between 250 and 350 beats per minute. A flutter episode can last as little as a few minutes or as long as several months. That’s one heck of a racing heart!
What calms a fluttering heart?
Doctors typically try to stop atrial fibrillation or flutter with medication that controls heart rate – beta blockers, calcium channel blockers, etc., or in some cases cardioversion. Cardioversion is an outpatient procedure that uses a carefully targeted electrical jolt to set the heart back into its normal rhythm.
The procedure works pretty well with 92% of patients settling back into a safe rhythm within hours of treatment, but 42% of them are likely to have another episode within a few years. With this in mind, doctors are now trying to figure out if patients can prevent it from coming back by making simple lifestyle changes.
Does abstaining from coffee help your heart?
Cardiologists followed 200 patients who had received cardioversion for atrial fibrillation for six months after their procedure to see whether drinking coffee would bring the flutter back. Patients were recruited from hospitals in San Francisco, USA, Adelaide, Australia and Toronto, Canada. Only people over 21 scheduled for cardioversion for atrial fibrillation or flutter who regularly drink coffee were invited to take part.
They excluded people with a life expectancy of less than six months, a history of drug or alcohol abuse, who had had heart surgery, didn’t drink coffee or could not bring themselves to give up coffee.
The researchers split the 200 participants randomly into two groups: the first 100 would abstain from coffee and other caffeinated products for six months or until they had another atrial fibrillation whichever came first. The second group of 100 agreed to drink at least one coffee or one shot of espresso every day for six months or until they experienced another atrial flutter.
Did atrial fibrillation recur within six months?
The cardiologists would then wait to see how many people in each group would have atrial fibrillation within six months. The recurrence was defined as a clinical diagnosis of atrial flutter or a device detected recurrence (for example a heart rate monitor or pace maker) that lasted more than 30 seconds. They also tracked adverse events to make sure that the coffee wasn’t harming patients in other ways. The participants in each group were well matched, with similar demographics (age, sex, education, race, ethnicity) and medical histories (medications, hypertension, pace maker, heart failure, diabetes, etc.) and similar patterns of caffeine and alcohol consumption prior to the trail.
The aim was to eliminate as many differences between the groups as possible so that they could pin point the change in coffee consumption as the cause of any differences between the groups.
Coffee did not trigger atrial fibrillation or atrial flutter
At the end of the study, coffee drinkers will be relieved to learn, caffeine consumption did not increase the odds of a patient having another episode atrial fibrillation or flutter within six months of their cardioversion. Of the 100 coffee drinkers, one withdrew from the study but the other 99 stuck with it.
The first thing the researchers noticed was that the coffee drinkers went longer before they had a recurrence of atrial fibrillation or flutter. People who drank coffee or abstained were similarly likely to have a recurrence within the first few days of cardioversion. This reflects the success rate of the procedure.
Once those people had exited the study, the two groups soon diverged, with caffeine abstainers tending to have a recurrence at least 30 days earlier than people who drank coffee and consumed caffeinated products. By the end of the trial, only 47% of coffee drinkers had had another atrial fibrillation or flutter, while 64% of abstainers did.
A little of what you fancy can do you good-but with doctor’s OK
Drinking coffee won’t cure your heart arrhythmia but the evidence tentatively shows that it might not make things worse. These are early days, with a small cohort so the results might not generalize to everybody. The team did, however, ensure that the sample size would provide sufficient power to be pretty representative of the average atrial fibrillation patient. That is, 60% male, around 69 years old with a mean BMI of 30 and a previous history of coffee drinking.
If you have been diagnosed with atrial fibrillation of atrial flutter and want to revisit your coffee consumption, talk to your doctor before you make any changes.
Sources
Wong CX, Cheung CC, Montenegro G, et al. Caffeinated Coffee Consumption or Abstinence to Reduce Atrial Fibrillation: The DECAF Randomized Clinical Trial. JAMA. Published online November 9, 2025. doi:10.1001/jama.2025.21056
Brandes A, Crijns HJGM, Rienstra M, et al. Cardioversion of atrial fibrillation and atrial flutter revisited: current evidence and practical guidance for a common procedure. Europace. 2020;22(8):1149–1161. doi:10.1093/europace/euaa057
