What is “Holiday Heart Syndrome” and How Does Excessive Alcohol Consumption Cause Atrial Fibrillation?

It’s the season to party and celebrate the end of another year, but having a few too many drinks can leave you less than joyful.

Maybe it’s a dull headache, a “jittery” feeling, or an unquenchable thirst that has you reaching for electrolytes the next day after drinking.

But for some, hangover symptoms can be a sign of something more sinister, especially if you experience heart palpitations, shortness of breath, or dizziness.

All of this is characteristic of “holiday heart syndrome,” a term coined in 1978 after American doctors noticed a suspicious pattern.

On Monday, they saw an increase in patients showing up to emergency departments after a weekend of heavy drinking with a heart condition called atrial fibrillation, characterized by an irregular and sometimes rapid heartbeat.

They also found increased rates of atrial fibrillation during the holidays.

This led to the discovery that two-thirds of people under the age of 65 who presented to the emergency room with atrial fibrillation had heart arrhythmia caused by excessive alcohol consumption.

Now, a study by a group of German researchers has looked into the mechanisms behind alcohol-induced atrial fibrillation, speculating that the part of the nervous system that helps us “rest and digest” plays an essential role.

But first, how common is alcohol-induced atrial fibrillation and how concerning is it?

What is atrial fibrillation?

“Atrial fibrillation is a common cause of what we call palpitations, or the awareness of an irregular heartbeat,” says Peter Kistler, head of cardiac electrophysiology at the Baker Heart and Diabetes Institute in Melbourne.

“It can make people short of breath, tired, washed out and dizzy.”

Atrial fibrillation is diagnosed by ECG (a test that measures the electrical activity of the heart) and is usually treated with medication or a “shock” from a defibrillator.

It can be triggered by factors such as high blood pressure and heart disease. Sometimes it has no obvious cause.

It’s difficult to quantify exactly how many people suffer from atrial fibrillation after drinking alcohol, but the German study, published in March in the European Heart Journal, suggests it affects around five to 10 percent of heavy drinkers. otherwise in good health. .

And although atrial fibrillation induced by excessive alcohol consumption affects all ages, Professor Kistler says it can be particularly problematic for older people.

“In the younger population (we are more concerned) more symptoms of atrial fibrillation, but for older people it is a very common cause of stroke and heart failure.”

Perhaps most worrying is evidence suggesting that episodes of atrial fibrillation can have long-term health consequences, even in younger people.

“So the more episodes of atrial fibrillation you have, the more changes we see in the heart that make you vulnerable to more episodes that last longer.”

But people who have suffered from atrial fibrillation can reduce their future risk.

A 2019 randomized controlled trial by Professor Kistler showed that abstaining from alcohol significantly reduced disease recurrence.

How does alcohol cause atrial fibrillation?

Until recently, the time frame within which atrial fibrillation occurs after excessive alcohol consumption was poorly understood.

The German study sought to remedy this situation. He tracked more than 200 volunteers who planned to drink excessively and fitted them with Holter monitors, collecting a range of heart rate and rhythm measurements over 72 hours.

When the study participants drank, their hearts beat faster. But it was only during what the researchers called the “hangover” period, six to 19 hours after drinking, that participants typically experienced atrial fibrillation.

Professor Kistler says this finding – that atrial fibrillation is more common during a hangover than when drinking alcohol – suggests the condition is likely triggered when a part of the body’s nervous system called parasympathetic nervous system is suppressed.

The parasympathetic nervous system is responsible for rest and relaxation of the body. When activated, it slows down the heart, among other effects.

However, when it is removed, it is like taking one foot off the brake on the heart rate. The heart is then more likely to beat irregularly and cause atrial fibrillation, explains Professor Kistler.

“We found that suppression of the parasympathetic nervous system becomes greater during this hangover period (than during alcohol consumption).

“So we think the parasympathetics play a very important role in triggering atrial fibrillation.”

The heart “doesn’t work as efficiently”

Professor Kistler and his team also studied what happens after the initial ‘hangover’ period (between 24 and 48 hours after excessive alcohol consumption), finding that the cardiovascular system does its best to ‘hangover’ itself. rebalance”.

“There’s this rebound that happens afterwards… where the parasympathetic nervous system can ‘overcorrect’,” he explains.

This was characterized by a slowed heart rate (even slower than before drinking), while they also noted changes to the heart on MRI scans.

While the research team initially looked for signs of alcohol causing inflammation of the heart, they instead discovered what Professor Kistler describes as a “reduction in upper chamber compression function”, also known as of atrial mechanical dysfunction.

“That’s why people don’t feel as good 24 to 48 hours after drinking, because their hearts aren’t working as efficiently,” he says.

Overall, Professor Kistler says the evidence adds up to a clear message.

“There’s this whole idea that alcohol is good for the heart, but that’s certainly not true if you have an electrical heart problem, and (as general advice) it’s very questionable.”

Australian national guidelines recommend healthy adults drink no more than 10 standard drinks per week, while Professor Kistler advises drinking even fewer if you have a heart arrhythmia.

“Ideally, you (would stop drinking completely), but we say (stick to) up to three standard drinks per week.”

Could it be “hangover anxiety”?

The effect of alcohol on the parasympathetic nervous system may also be responsible for another notorious feature of a hangover: the phenomenon known as “hangover” (or hangover anxiety). .

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Up to 22 percent of people report feeling anxiety after drinking alcohol.

And given that symptoms of anxiety include palpitations, Professor Kistler acknowledges that it can be difficult to distinguish it from atrial fibrillation.

“They’re very often mixed together,” he says.

One way to distinguish the two, he says, is that your heart may feel like it’s “racing” when you’re anxious, but you shouldn’t feel like your heart is beating “irregularly.”

If in doubt, he advises consulting a doctor, or going to the emergency room.

“(Go to the hospital) if you feel very unwell, but especially if you are short of breath, dizzy or feel like your heart is beating uncontrollably.”