How Stress Can Lead To Heart Attack

Many extensive studies have been conducted to find out the correlation between stress and cardiovascular diseases. Researchers have uncovered lots of facts suggesting a close relationship between the two. Though scientists could not exactly propose the ‘cause and effect’ relationship between stress and heart diseases, there are abundant evidences to prove that continuous mental stress always has a negative impact on the cardiac health of people, and the effect is much greater in patients who already have a heart disease.

Stress, continuous or acute, can lead to heart attack

Chronic mental stress, which was previously not considered to be a direct cause for cardiovascular diseases, is now recognized as a potential risk factor. It is also found to have a major contribution to the development of other health risks.

In recent years, researchers concentrated on analyzing the effect of acute stress, or ‘acute triggers’, on heart diseases, especially on myocardial infarction that is commonly known as heart attack. The term “acute triggers” refers to events or reactions to events that occurred in the immediate moments or hours before the onset of heart attack.

How does that happen?

The mechanism by which stress leads to heart attack can be considered from two viewpoints –psychological/behavioral and physiological.

To understand how psychologically stress leads to heart attack, let us consider a person who is continuously in stress. He is unlikely to maintain a healthy diet, he tends to stay physically inactive, he is more likely to smoke.

Thus, chronic stress can cause exacerbation of some unhealthy lifestyles habits and lead to heart attack.

Not so long ago, the reaction to stress was usually described as the ‘fight or flight’ response. But these days scientists argue that the reaction to stress is not a generalized response and it differs among individuals depending on how well they cope with stress, their personality and their social conditions. Genetic factors are also found to influence the individual’s cardiovascular reaction to stress.

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Physiological stress responses that lead to heart attack

The physiological stress response, often referred to as the "fight-or-flight" response, is a natural reaction of the body to perceived threats. While this response is adaptive and can be beneficial in acute, short-term situations (like running from a predator), chronic activation of this stress response, especially in non-threatening situations, can have detrimental effects on cardiovascular health.

When a person goes through stress, the various physiological mechanisms that take place can be put in simple words: stress adds physiological burden on the heart by increasing heart rate and blood pressure and constricting the blood vessels that nourish the heart. Over time, this may lead to heart attack.

Mental stress triggers two important neural pathways – the sympathetic nervous system and the hypothalamic-pituitary (HPA) axis. What are these pathways and how do they affect cardiac health?

Heart And Cardiovascular System Are Very Sensitive To Stress

The sympathetic pathway, when activated by stress, releases stress hormones - adrenaline and cortisol. These hormones respond to stress by increasing heart rate, narrowing the blood vessels, increasing blood pressure and activating and aggregating platelets that contribute to the formation of thrombus (blood clot). All these factors ultimately lead to heart attack if they affect the coronary arteries that supply blood to heart. The HPA axis responds to stress by stimulating the release of the stress hormone cortisol (through a cascade of reactions) from the adrenal glands.

Elevated cortisol levels can lead to various negative effects, such as increased blood sugar levels and suppression of the immune system. Over time, this can contribute to inflammation and damage to the artery walls.

Persistent stress can reduce blood supply to heart

Stress is also found to play a role in the development of atherosclerosis which on the long run can lead to cardiovascular diseases including heart attack.

Atherosclerosis is characterized by the inflammation of the walls of arteries along with the deposition of cholesterol particles, cellular waste products, white blood cells and smooth muscle cells in the inner layer of arterial walls to form plaques. A plaque grows over a long period of time and when it disrupts from the wall of an artery, it attracts platelets and forms a blood clot subsequently leading to the occlusion of the artery. When the arteries nourishing the heart are occluded, the result is more commonly a heart attack.

But what is the role of stress in this long process?

Stress-induced activation of the HPA axis impairs the lipid and glucose metabolism. A series of metabolic events result in the cholesterol accumulation in various parts of the body, including arterial walls, thus contributing to the plaque formation.

Chronic stress can lead to conditions like obesity and diabetes, which are significant risk factors for heart disease. Stress can alter metabolic functions, leading to fat accumulation, especially around the belly area, and can increase insulin resistance.

Studies suggest that chronic stress can affect the functions of the endothelial cells that are found along the inner wall of blood vessels. The endothelial cells produce nitric oxide (NO) which normally inhibits accumulation of white blood cells and platelets. This ensures smooth blood flow through the arteries. 

Psychological stress is also found to increase the circulating levels of certain proteins called inflammatory cytokines IL-6 and TNF-α. These are produced by the white blood cells that constitute the body’s immune system. IL-6 plays a major role in causing platelet activation, aggregation and plaque formation.

Frequent acute stress episodes can lead to heart attack

While chronic stress takes time and contributes to formation of atherosclerotic plaques in the long run, the acute triggers are found to affect mostly the last step of the process.

If a person already has atherosclerotic plaques, an acute stress outburst can result in narrowing of blood vessels, plaque disruption, clot formation and blockage of blood vessels supplying the heart. Even in the absence of a plaque or clot, an acute trigger stimulates the sympathetic pathway and may result in ventricular fibrillation, a condition where the heart beats abnormally leading to sudden death.

Studies suggest that acute mental stress can also impair the functions of endothelial cells. Though the endothelial dysfunction is transient in this case, lasting up to 1.5  hours, researchers say that frequent encounter of such short-lived episodes of acute stress are likely to initiate or accelerate atherosclerosis in early life.

Hot-tempered people are at higher risk of heart attack

A recent study that focused on the effect of acute triggers on heart was published in the European Heart Journal.

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According to this study, the risk of heart attack is higher in the first two hours following an outburst of anger. The effects of anger outbursts on heart are usually transient with infrequent episodes, but with increased frequency of episodes, the impact may be larger. The effects are also found to be more in people who already have other risk factors.

Stress, either directly or indirectly, is found to be a cause of serious cardiovascular events, especially heart attack. But it is a modifiable risk factor. Researchers are realizing the need for further studies to develop stress management programs that would have a favorable impact on cardiac health of people.