Scientists believe they have an explanation for the axiom that stress, emotional shock, or overexertion may trigger heart attacks in vulnerable people. Hormones released during these events appear to cause bacterial biofilms on arterial walls to disperse, allowing plaque deposits to rupture into the bloodstream, according to research published in published today in mBio®, the online open-access journal of the American Society for Microbiology.
“Our hypothesis fitted with the observation that heart attack and stroke often occur following an event where elevated levels of catecholamine hormones are released into the blood and tissues, such as occurs during sudden emotional shock or stress, sudden exertion or over-exertion” said David Davies of Binghamton University, Binghamton, New York, an author on the study.
Davies and his colleagues isolated and cultured different species of bacteria from diseased carotid arteries that had been removed from patients with atherosclerosis. Their results showed multiple bacterial species living as biofilms in the walls of every atherosclerotic (plaque-covered) carotid artery tested.
In normal conditions, biofilms are adherent microbial communities that are resistant to antibiotic treatment and clearance by the immune system. However, upon receiving a molecular signal, biofilms undergo dispersion, releasing enzymes to digest the scaffolding that maintains the bacteria within the biofilm. These enzymes have the potential to digest the nearby tissues that prevent the arterial plaque deposit from rupturing into the bloodstream.
According to Davies, this could provide a scientific explanation for the long-held belief that heart attacks can be triggered by a stress, a sudden shock, or overexertion. To test this theory they added norepinephrine, at a level that would be found in the body following stress or exertion, to biofilms formed on the inner walls of silicone tubing.
How Does Stress Increase the Risk for Heart Disease?
Medical researchers aren’t sure exactly how stress increases the risk of heart disease. Stress itself might be a risk factor, or it could be that high levels of stress make other risk factors (such as High cholesterol or high blood pressure) worse. For example, if you are under stress, your blood pressure goes up, you may overeat, you may exercise less, and you may be more likely to smoke.
If stress itself is a risk factor for heart disease, it could be because chronic stress exposes your body to unhealthy, persistently elevated levels of stress hormones like adrenaline and cortisol. Studies also link stress to changes in the way blood clots, which increases the risk of heart attack.
“At least one species of bacteria - Pseudomonas aeruginosa - commonly associated with carotid arteries in our studies, was able to undergo a biofilm dispersion response when exposed to norepinephrine, a hormone responsible for the fight-or-flight response in humans,” said Davies. Because the biofilms are closely bound to arterial plaques, the dispersal of a biofilm could cause the sudden release of the surrounding arterial plaque, triggering a heart attack.
Can stress cause a heart attack?
Everyone knows that keeping stress levels low is an important component of a healthy lifestyle. Managing stress can have all sorts of positive effects on your health, like lowering blood pressure and cholesterol levels, which can lead to a decrease in risk of heart disease.
But have you ever wondered if stress itself can directly cause a heart attack? The answer is - not exactly. But sudden, severe stress can cause something called stress cardiomyopathy (also known as “broken heart syndrome” or “takotsubo cardiomyopathy”), an under-diagnosed health condition with symptoms that are very similar to those of a heart attack.
What is it?
The word cardiomyopathy refers to heart muscle that is weakened, resulting in the heart not working as well as it should. Stress cardiomyopathy refers to weakening of the heart as a result of intense physical or emotional stress.
The intense grief that comes with the death of a loved one is a common cause of this condition. However, emotions like extreme anger, fear, and surprise can also cause it. Physical stress to the body includes stroke, dehydration, or low blood sugar.
To their knowledge, this is the first direct observation of biofilm bacteria within a carotid arterial plaque deposit, says Davies. This research suggests that bacteria should be considered to be part of the overall pathology of atherosclerosis and management of bacteria within an arterial plaque lesion may be as important as managing cholesterol.
After a person experiences an intense emotional event, stress hormones (such as adrenaline) are released into the body at levels that can be 10 to 30 times the normal levels. Stress hormones usually help the body cope with stress. However, at these toxic levels of hormones, it’s thought that the heart becomes overwhelmed and “stunned” to the point where it can no longer pump properly.
It is not certain what exactly happens to result in the heart pumping inadequately. It may be due to a decreased oxygen supply to the heart or due to too much calcium entering the heart cells. In any case, it can result in shock, heart failure, and heart rhythm problems, all of which can be life-threatening if not treated.
But with treatment, most patients make a full recovery, sometimes in just a matter of weeks. The effects of excess stress hormones on the heart are brief and do not cause permanent damage to the heart.
Stress cardiomyopathy vs. heart attack
Heart attacks and stress cardiomyopathy can have very similar symptoms but they are different conditions. Most heart attacks are caused by blockages or blood clots in the coronary arteries (the blood vessels that supply the heart), resulting in a decreased flow of blood to the heart that can lead to heart muscle cells to die. This is what can cause permanent damage to the heart muscle cells.
On the other hand, the heart is not permanently damaged with stress cardiomyopathy. Stress cardiomyopathy does not seem to be a result of artery blockages or blood clots. For most people that suffer stress cardiomyopathy, the heart weakness usually stops within a couple of weeks and there is no permanent damage.
mBio® is an open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. The focus of the journal is on rapid publication of cutting-edge research spanning the entire spectrum of microbiology and related fields.
The American Society for Microbiology is the largest single life science society, composed of over 39,000 scientists and health professionals. ASM’s mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.
American Society for Microbiology