What happens during a heart attack, exactly?

What is it?

Myocardial infarction (MI), or heart attack, happens when blood stops flowing to a part of the heart and the part becomes damaged. The most typical symptom is chest pain or discomfort, which can “radiate” into the arm, shoulder, back, and jaw. Other symptoms include shortness of breath, tiredness, and a cold sweat.

The WHO has estimated that in 2004, 12.2% of worldwide deaths were caused by diseases that lead to the deprivation of blood in the heart. It is the leading cause of death in high- and middle-income countries.

For those with MI in the US,  5-6% die before leaving the hospital and 7-18% die within a year.

What causes it?

Coronary heart disease is the leading cause of MI. It happens when cholesterol blocks the vessels that are supposed to transport blood to the heart, and its leading risk factors are smoking and obesity. Several diseases, such as diabetes, and some genetic factors have also been associated with MI.

What happens during it?

In coronary heart disease, plaques start to accumulate inside the coronary arteries. They consist of cholesterol, white blood cells and calcium among other things, and are covered by a fibrous cap. Sometimes these plaques can rupture. This can happen because of a sudden change in blood pressure, a sudden contraction of the artery, or an inflammation. When we get a cut in our skin, our body has a sophisticated mechanism of making our blood clot so that it has time to repair the wound before we bleed to death. When a plaque ruptures, the same mechanism is activated, but this time it doesn’t prevent blood from fleeing our body but from reaching certain parts of our heart.

Cells need energy to function, and their main source of this energy is glucose. The cell can’t, however, use glucose directly to its needs: it first needs to convert the energy in glucose into the energy of a molecule called ATP. This process needs oxygen to function effectively. The cells of the heart need to work hard and continuously in order to maintain the pumping, and for this purpose they need a steady supply of oxygen. If they can’t get it, they don’t survive for long, and this is exactly what happens during MI. A blood clot forms that prevents blood from flowing to an area of the heart; the cells in this area don’t get oxygen; the cells die and don’t grow back.

How can it be treated?

An MI can be effectively prevented by maintaining a healthy lifestyle including a good diet, exercise, and no smoking. Aspirin, statins, and other medications can be used as prevention in those who are in an elevated risk. When the MI happens, ordinary surgery can be performed to widen the coronary artery, or sometimes a small balloon can be passed through the vessels until it reaches the place of injury, where it is dilated so that it opens the artery up.



Sources: https://en.wikipedia.org/wiki/Myocardial_infarction, http://www.webmd.com/heart-disease/how-a-heart-attack-happens, http://www.nhs.uk/Conditions/Heart-attack/Pages/Treatment.aspx


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