Put your knowledge to the test -- and protect yourself -- by learning these surprising triggers:
1. Sudden, intense outbursts of anger
A recent study of 313 heart attack patients published by scientists in Sydney, Australia found that a heart attack was 8.5 times more likely to happen two hours after an intense bout of anger than after an average two hour period. Researchers Dr. Thomas Buckley of Sydney Nursing School and Prof. Geoffrey Tofler of the University of Sydney defined intense anger as a five or higher on a seven-point scale. Respondents who described their angry episode as a five or higher agreed that they felt, "furious," "enraged" or "out of control" about two hours before their heart attack. Their fists may have been clenched, they may have been throwing objects and they may have been hurting themselves or others. As for what they were enraged about, the researchers noted that most participants (42 percent) said their anger stemmed from an argument, most commonly with a family member. Anger from work or driving tied for 14 percent.
Thankfully, Buckley and Tofler concluded that anger-induced heart attacks are rare; only two percent of the participants in their study had had been enraged before their heart episode. Of those who did have an anger-induced heart attack, they all had at least one chronic risk factor (like diabetes or smoking), and two had already had heart attacks at least once before.
In order to avoid heart disease events trigged by intense anger, Buckley and Tofler suggested that people who smoke, have elevated blood pressure or have elevated cholesterol strategize ways to control their emotions. These strategies can include listing hot-button issues that can trigger anger, becoming aware of the warning signs one's body exhibits during anger, and learning anger management techniques like distraction and relaxation. The researchers also noted in their study that other research has shown that taking beta-blocking drugs or aspirin after an especially angry episode have been shown to reduce risk of heart attacks as well.
2. Acute anxiety
In the same study, Buckley and Tofler also found that an episode of acute anxiety was also associated with a 9.5 time greater risk of heart attack two hours later.
"Increased risk following intense anger or anxiety is most likely due to increased heart rate, blood pressure, tightening of blood vessels and increased clotting, all associated with triggering heart attacks," explained Buckley in a statement about his study. The researchers recommended that people most at risk of heart attacks proactively avoid activities that trigger anxiety and anger, as well as seek out stress reduction training to limit anger and anxiety responses.
"Before, during and after, take time out, use distraction, use relaxation, learn assertiveness skills, acknowledge the thing that is making you angry," Tofler wrote in an email to HuffPost. "Control your thinking and try to avoid exaggerating the episode."
3. An unusual physical activity
Every winter, thousands of people are injured when shoveling snow, and the most serious injuries are related to heart health. There were an average of 11,500 injuries each year from 1990 to 2006 that related to snow shoveling, according to a 2011 study of U.S. emergency room departments by the Center for Injury Research and Policy. Only seven percent of those injuries were cardiac-related, but they were responsible for 100 percent of the snow shoveling-related fatalities in that study.
The cold, vessel-constricting air and strenuous physical exertion can be a deadly combination for those with already weakened hearts. Researchers have found that people who have had a prior heart attack or known heart disease, as well as people with high blood pressure, high cholesterol, smokers and those who lead mostly sedentary lifestyles are most at risk for a heart attack while clearing snow.
If you're going to shovel snow, the American Heart Association suggests taking frequent rest breaks and using a small shovel so that you lift less snow at once. Also, skip the heavy meals and alcohol before and after shoveling. Most importantly, however, people should learn to listen to their body's signals, which could signal trouble with something as small as mild pain or discomfort and can escalate to an uncomfortable pressure in the chest and shortness of breath.
4. A between-the-sheets session
Similarly, a steamy sex session can also trigger cardiac events in certain at-risk individuals. A meta-analysis of four studies analyzing mostly men in their 50s and 60s found that sex was linked to a 2.7 increased relative risk of heart attack compared to periods when the participants weren't having sex.
Thankfully, researchers describe the absolute number of sex-induced heart attacks as "minuscule," or less than one percent of all heart attacks. In part, this is because sex usually lasts for a short amount of time, and the most dangerous part of sex for people with pre-existing coronary artery disease -- when blood and heart pressure rates rise significantly during an orgasm -- only lasts between 10 to 15 seconds.
Sexual activity is an important part of mental and physical health, and should try to be preserved as much as possible -- even for people with weakened hearts. To minimize their risk, experts in an American Heart Association statement paper recommend that people work with their doctors to stabilize their heart health before having sex. Increasing regular exercise can also help people prepare for sexy time.
5. Substance abuse
Heart attacks can also be triggered by abusing drugs or alcohol. Despite the often touted protective effect of red wine on hearts, the American Heart Association acknowledges that too much alcohol can raise triglyceride levels and blood pressure, as well as cause people to eat too much. These risk factors can lead to heart disease and sudden cardiac death.
6. Unusually heavy meals.
Speaking of eating too much, even sitting down to a big meal can be fraught with peril if you're at risk for a cardiac event. A US Department of Veterans Affairs (VA) researcher found in 2000 that people at risk of heart disease were four times more likely to have a heart attack two hours after a big meal. The study asked 1,986 patients about their meals in the days leading up to their heart attack. Of those, 158 had eaten an "unusually heavy meal" within 26 hours, and 25 of them had eaten a big meal two hours before their attack.
Heavy meals could be acting on the body in a number of ways to trigger a heart attack. The simple act of eating food increases heart rate and blood pressure, according to Science Daily. Other theories implicate fatty acids from food entering the bloodstream, or rising insulin rates that could constrict coronary arteries.
Perhaps the most notorious and high-profile cases of heart attack after a heavy meal have occurred at the Las Vegas-based Heart Attack Grill, a restaurant famous for serving meals like the 10,000-calorie "Quadruple Bypass Burger." A handful of people have suffered an attack mid-meal or after a meal at the restaurant, including two spokesmen (one official, one unofficial) for the business.