A heart attack is a medical emergency that requires an immediate call to the emergency services. However, there are sometimes warning signs that can show up weeks in advance that should prompt you to visit your doctor.

Firstly, what exactly happens during a heart attack? A heart attack occurs when the vessels that supply the heart itself with oxygen and nutrients—known as coronary arteries—become blocked. One cause is calcium deposits building up in them, says the German Heart Foundation.

As this is a gradual process, symptoms often appear before the blockage occurs, when the vessels are already narrowed in what is referred to as coronary heart disease.