Heart attacks happen when there's a sudden loss of blood flow to a part of the heart muscle - a complication commonly caused by fatty deposits clogging up your arteries. This internal blockage can produce acute symptoms, such as pain or discomfort in your chest that happens suddenly and doesn't go away. Most people will be familiar with the unsettling image of a person clutching their chest, but it is also possible to have a silent heart attack.
As Mayo Clinic explains, a silent heart attack is a heart attack that has few, if any, symptoms or has symptoms you don't recognise as a sign of a heart attack.
"You might not have chest pain or shortness of breath, which are typically associated with a heart attack," notes the health body.So, what should you be looking for?
People who have a silent heart attack may later recall that they had indigestion, the flu or a strained chest muscle, it notes.
It is worth nothing that still involves blockage of blood flow to your heart and possible damage to the heart muscle.
The health body says to:Call 999 for an ambulanceSit down and stay calmTake a 300mg aspirin if you have one within reachWait for the paramedics.How to reduce your risk
The same preventive measures also apply to a silent heart attack - making healthy lifestyle changes.
One of the most robust measures you can take is to overhaul your diet and shun certain items.
The worst culprits are high-fat foods because they will cause fatty plaques to build up in your arteries, warns the NHS.
This is because fatty foods contain an unhealthy type of cholesterol called LDL cholesterol.
"Avoid foods containing high levels of saturated fat, as they increase levels of LDL cholesterol in your blood," advises the NHS.
Foods high in saturated fat include:PiesFried foodsSausages and fatty cuts of meatButterGhee (a type of butter often used in Indian cooking)LardCreamHard cheeseCakes and biscuitsFoods that contain coconut or palm oil
Instead you should aim to follow a Mediterranean-style diet - this means eating more bread, fruit, vegetables and fish, and less meat.
"One of the better-known aspects is the use of monounsaturated fats such as olive oil instead of saturated fats such as butter," according to Victoria Taylor, a dietician at the BHF.
Being active and doing regular exercise will also lower your blood pressure by keeping your heart and blood vessels in good condition, explains the NHS.
What's more, regular exercise can also help you lose weight, which will help to lower your blood pressure, notes the health body.
Adults should do at least 150 minutes (two hours and 30 minutes) of moderate-intensity aerobic activity, such as cycling or fast walking, every week, it says.