From its triggers to its symptoms, atrial fibrillation (afib) can be unpredictable. “Just as you can have atrial fibrillation without visible symptoms, you can experience an attack of atrial fibrillation without a trigger,” says Smit Vasaiwala, MD, an assistant professor of cardiology at the Loyola University Health System in Maywood, Illinois. However, most people are able to identify at least some afib triggers, and knowing your triggers can help decrease the frequency of attacks and lower your risk for stroke.

You’re probably aware of common afib triggers, including alcohol, smoking, exercise, and over-the-counter cough and cold medications. But have you considered these seven lesser-known triggers that can be just as harmful to your heart?

1. Medical procedures. “It’s well-known that heart surgery is a major trigger for atrial fibrillation, but any type of surgery or medical procedure can be a trigger,” Dr. Vasaiwala says. “Anything that triggers the flight-or-fight response, such as emotional or physical stress, stimulates your heart.” Let your doctor know about your atrial fibrillation history before you have any medical procedure, even a minor one.

2. Travel. Taking a trip can expose you to potential afib triggers. These include becoming overtired, the stress of travel, and a change in sleep patterns, which can trigger the fight-or-flight response. Whenever you travel, get enough sleep, stay well hydrated, and don’t skip meals.

3. Stress. “Stress is a common trigger of atrial fibrillation,” Vasaiwala says. ”Too much stress is like a shot of adrenaline to your heart.” Identify your personal stressors and take steps to avoid or defuse them. If you can’t rule out all causes of stress, practice stress-reduction techniques to lessen the impact.

4. The holidays. “Holiday heart” is a well-documented atrial fibrillation trigger. That’s because the holidays can be a bonanza of triggers, including stress, fatigue, and alcohol use. Alcohol has an especially irritating effect on the heart, and binge drinking is a classic afib trigger. For this reason, it’s important to know your limits. “For some people with atrial fibrillation, any amount of alcohol is too much,” Vasaiwala says. “If your heart is very sensitive to alcohol, even half a glass of wine may be a trigger.”

5. Air pollution. Atrial fibrillation attacks may go hand-in-hand with air pollution. In one study, researchers followed 176 people with atrial fibrillation with implanted defibrillators that turn on when an episode occurs. Two years’ worth of data from the study showed that there were more attacks of afib when air pollution was high. These findings were published in 2013 in the Journal of the American College of Cardiology.

The culprit seems to be very fine particles of pollution from cars and power plants that travel deep into the lungs and trigger atrial fibrillation. To prevent an afib episode, check local air quality daily, and don't go outdoors when pollution is high.

6. Dehydration. Dehydration can trigger atrial fibrillation. Low levels of minerals in the blood (electrolytes), especially potassium, can trigger an abnormal heart rhythm, and when you’re dehydrated, electrolytes are depleted. Dehydration is most common in hot weather, especially when exercising outdoors, but it can also result from an illness that includes vomiting or diarrhea. Be sure to drink enough water on hot days and whenever you're sick.

7. Recreational drugs. Over-the-counter cough and cold medications can trigger afib because they stimulate your heart, but they aren't the only drug culprits: Marijuana can have the same effect, possibly raising your heart rate by 20 to 100 percent for several hours. Cocaine can also trigger an abnormal heartbeat.

Atrial fibrillation triggers are abundant and often surprising. Even seemingly happy events, like vacations and celebrations, can trigger an attack. “A good rule of thumb to stay heart-healthy with atrial fibrillation is to keep everything in moderation,” Vasaiwala says.