What causes a heart attack?


In its simplest form, a heart attack occurs when blood flow to the heart is reduced or completely stopped, keeping the muscle from getting the oxygen it needs to stay alive. Most people link heart attacks to atherosclerosis, but many other common causes are ignored. With this in mind, we at redOrbit decided to tell you some other factors, so you might better know your risk. And as always, if you’re concerned, please speak with a doctor.


Atherosclerosis is the top cause of heart attacks and doesn’t always happen just because someone ate fat, like most people think. A lot of things are associated with or contribute heavily to atherosclerosis, although we don’t always know why. For example, risk factors (besides diet) include smoking, older age, high cholesterol and triglycerides, kidney problems, high blood pressure, inflammation (like from arthritis or regular infections), and high blood sugar thanks to insulin resistance or diabetes.

These risk factors often cause the walls of the coronary (heart) artery to become damaged, which can trigger substances like blood cells and plaque (fatty deposits) to build up and harden. As plaque deposits build up, the artery become narrower, meaning less blood is reaching the heart—which can deprive parts of oxygen, leading to part of the heart becoming damaged or dying.

However, it can progress from there: If the plaque ruptures, blood clots form around them. The clot plugs up the artery, completely blocking blood flow to the heart.

Coronary Artery Spasm

Besides something blocking the coronary artery, the artery itself can contract to the point of blood restriction (also known as a coronary artery spasm). While not all causes of this are known, they can include taking drugs like cocaine, exposure to extreme cold, cigarette smoking, and emotional pain or stress, like in the Parks and Rec episode where Leslie and Anne scare poor, poor Jerry into having a fart attack.

Stress is a major cause, especially in the long term. However, acute stress can lead to a heart attack as well. If one becomes overwhelmed by an emotion like fright, massive amounts of adrenaline are released. Martin A. Samuels, chairman of the neurology department at Brigham and Women’s Hospital in Boston, explained why to Scientific American:

“Adrenaline from the nervous system lands on receptors of cardiac myocytes (heart-muscle cells), and this causes calcium channels in the membranes of those cells to open. Calcium ions rush into the heart cells and this causes the heart muscle to contract. If it’s a massive overwhelming storm of adrenaline, calcium keeps pouring into the cells and the muscle just can’t relax.

“There is this specially adapted system of muscle and nerve tissue in the heart—the sinoatrial (SA) node, the atrioventricular node, and the Purkinje fibers—which sets the rhythm of the heart. If this system is overwhelmed with adrenaline, the heart can go into abnormal rhythms that are not compatible with life. If one of those is triggered, you will drop dead.”

Tearing & kidneys

A tear in your coronary artery may cause a heart attack as well, as it may lead a significant amount of blood away from your heart.

Problems with your kidneys can lead to heart attacks in many ways—including anemia and imbalances in phosphate and calcium that can lead to calcification of blood vessel walls.

However, some things linked to heart attacks don’t seem to have a good explanation as to why they trigger them. In a 2012 study of nearly 24,000 people, calcium supplements (but not dietary calcium) were linked to an increased incidence of heart attack. Depression is similarly linked and unexplained.

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