It's called "holiday heart" because it happens to binge drinkers who feel a flutter or irregular heartbeat after too many cocktails at parties. But a research review suggests it can happen after just one drink.
Conventional wisdom, based on plenty of previous research, is that the occasional glass of wine or beer can be good for the heart, reducing the risk of heart disease and stroke as well as death from cardiovascular causes, lead study author Dr. Peter Kistler of the Baker IDI Heart and Diabetes Institute and the Alfred Hospital in Melbourne, Australia, told Reuters Health.
For the current study, however, researchers examined data collected on almost 900,000 people and found an 8 percent risk increase for irregular heartbeat with each alcoholic drink consumed per day.
"Alcohol is not universally 'good' for the heart," Kistler said. "It is beneficial for the 'plumbing' or blood supply to the heart muscle, but for the 'electrical' part of the heart or the heartbeat it is not."
The study focused on what's known as atrial fibrillation, a quivering or irregular heartbeat (arrhythmia) that can lead to blood clots, stroke, heart failure and other heart-related complications. Untreated, the condition doubles the risk of heart-related deaths and is linked to a five-fold increased risk for stroke, according to the American Heart Association.
While nobody should binge drink during the holidays, people with a history of atrial fibrillation should be especially vigilant about avoiding or limiting alcohol, Kistler said.
Both men and women were equally at risk for holiday heart, researchers report in the Journal of the American College of Cardiology.
The study doesn't prove that an extra cocktail after dinner directly causes atrial fibrillation, the authors note.
Still, they offer some theories about how spending too much time at the bar during holiday cocktail parties might be bad for the heartbeat.
Drinking can damage heart cells directly and lead to small amounts of fibrous tissue within the heart causing an irregular heartbeat.
The review found that people with atrial fibrillation who continue to drink are more likely to have ongoing irregular heartbeats even after a common surgery to repair the heart's electrical system and fix the source of the flutter.
Heart muscle cells contract in a coordinated way by movement of electrical signals between cells. Over time, drinking may actually change these electrical signals, triggering irregular heartbeat.
Alcohol may also trigger an irregular heartbeat by stimulating what's known as the autonomic nervous system, which controls bodily functions such as heart rate, digestion and breathing.
More research still needs to be done to determine the specific mechanisms behind the relationship between alcohol and irregular heartbeat, the authors note. Causes may include alcohol's contribution to obesity, sleep and breathing problems, and high blood pressure, the authors speculate.
One challenge with the study and most research on the heart effects of alcohol is that researchers rely on people to accurately recall and report on how much they drink, a flawed process that often leads participants to underestimate their alcohol consumption, noted Tim Stockwell, director of the Center for Addictions Research and a professor at the University of British Columbia in Vancouver, Canada.
Often, studies that count former drinkers as 'abstainers' can obscure the effects of alcohol on the heart, too, making occasional drinkers look healthier than abstainers, Stockwell, who wasn't involved in the study, said by email.
Even so, there are some common sense steps anyone can take to lower the odds of heart rhythm problems after that next holiday party.
"Certainly drinking with food, interspersing with non-alcoholic drinks and generally keeping the dose of alcohol low are all recommended," Stockwell said. "This all reduces the heart's exposure to cardiotoxins."