Question: what causes a heart attack?

Susan Cartwright answered on 19 Jun 2015:

Usually, a blood clot which blocks the flow of blood to part of the heart, starving part of the heart muscle of oxygen and preventing it from beating normally. This is why fast treatment of heart attacks is very important: nowadays it is possible to give the patient a drug which breaks down clots, “curing” the heart attack and allowing blood to flow normally. The faster this is done, the less chance of permanent damage to the heart.

This type of heart attack is made much more likely if the blood vessels are already partially blocked by fatty deposits. This is why overweight people are at higher risk of heart attacks.

After the immediate treatment, people who have had this type of heart attack are usually treated by inserting a little metal tube, called a stent, into the bit of the artery in the heart that got blocked. This keeps the artery open and prevents it from causing another heart attack. It is a remarkably minor operation, as the stent is not inserted directly by opening the chest but is manoeuvred into place through one of the big arteries, using a very small incision in the thigh or wrist. The patient doesn’t have to have an anesthetic and can be out of hospital within a few days. Afterwards, they are usually encouraged to take small doses of aspirin, which reduces the risk of blood clots (and to lose weight, if they were overweight before).

There are rarer types of heart attack that are caused by problems with the heart’s electrical control system. One of these is an inherited condition called “long QT syndrome”, in which something as simple as a loud noise can trigger an irregular heartbeat which does not pump blood properly. When young, fit, healthy people suddenly die of a heart attack, this is often the cause, and doctors usually want to test their close relatives to check if anyone else has inherited the faulty gene. This sort of heart problem can be treated by implanting a pacemaker, which provides an artificial electrical trigger system for the heartbeat to replace the faulty natural one. There are a number of other failures of the heart’s electrical system which are treated in this way.