A heart attack - also known as a coronary thrombosis or myocardial infarction- is caused by a complete blockage of one of the coronary arteries. As a result, one part of the heart muscle is permanently deprived of oxygen. The blockage is often caused by a blood clot formed inside a coronary artery.

The majority of heart attacks are caused by a clot blocking one of the coronary arteries (the blood vessels bringing blood and oxygen to the heart muscle). The clot usually forms in a coronary artery previously narrowed from changes related to a condition called atherosclerosis. The atherosclerotic plaque (or build up) inside the arterial wall sometimes cracks, and triggers the formation of a clot, also called a thrombus.

A clot in the coronary artery interrupts the flow of blood and oxygen to the heart muscle, leading to the death of heart cells in that area. The damaged heart muscle loses its ability to contract, and the remaining heart muscle needs to compensate for that weakened area.

During the first hour or so of the blockage, the pain can be extremely severe. It’s usually felt as a crushing sensation in the centre of the chest and can also affect the arms jaw and neck. It’s also often accompanied by sweating, nausea and/or breathlessness, which lasts much longer than an angina attack.

Chest pain behind the sternum (breastbone) is also a major symptom of heart attack, but in many cases the pain may be subtle or even completely absent. This is called a “silent heart attack” and can especially occur in the elderly and diabetic. The pain usually radiates from your chest to your arms or shoulder; neck, teeth, or jaw; abdomen or back, but in some patients, the pain is only felt in one of these other locations.

Some patients report the pain as intense and severe or quite subtle and confusing.

It can also feel like:

squeezing or heavy pressure a tight band around your chest “an elephant sitting or lying on your chest” bad indigestion

Other symptoms include: Shortness of breath Cough Light-headedness' - dizziness Fainting Nausea or vomiting Sweating, which may be profuse Feeling of “impending doom” Anxiety

Permanent damage to the heart can follow persistent total blockage of the coronary artery as the affected area of heart muscle forms a scar. Depending on the scars exact location, it may be left weaker in its pumping action or there may be no noticeable impairment at all.

In the first few days after a heart attack, the heart can be rather irritable with an accompanying erratic heart rate. This is why continuous observation in a health care setting is vital in those first few days.

As the scar becomes fully formed, the heart stabilises and this surveillance is no longer required. Active rehabilitation ensures most people with uncomplicated heart attacks are able to lead perfectly normal lives afterwards.

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