“Chest pain needs to be investigated,” says Goss, “but very subtle changes such as feeling more tired or having a bit of jaw pain can also be signs of a heart problem. If it comes out of nowhere, that can be a really big sign there’s something going on with your heart.”

“Coronary heart disease can build up over years,” adds Prof Augustine. “People start to notice they can do less and less because it aggravates their symptoms, whether that’s left- or right-sided chest pain or pain going through to the throat.”

In retrospect, many people say they had noticed unusual bodily changes in the months before the event. The most common complaints are tiredness and disturbed sleep.

“It’s also well known that diabetics don’t necessarily get pain when they have heart disease and heart attacks. Their symptoms are much more subtle, or get missed altogether, and that’s a real problem,” says Dr Oliver Segal, a consultant cardiologist and electrophysiologist at the Harley Street Clinic (part of HCA Healthcare UK) and University College Hospitals.

It’s important to raise awareness of these silent symptoms. “Some of them may not be serious at all, but others could genuinely be life-threatening,” says Dr Segal. If you experience any of these symptoms alongside chest pain or breathlessness, you should seek immediate medical advice.

Arm, jaw or back pain

“If someone’s got pain or discomfort in their chest that starts spreading to their arms, their neck, their jaw, or their back feels tight or heavy, then they should call [111],” says Goss.

People who have been diagnosed with angina – sudden pain in your chest, neck, shoulders, jaw or arms – and live with it may get a similar sort of chest pain on exertion. “Jaw pain, left arm pain, back pain can all be variants of angina,” explains Dr Segal. “Naturally, there are many other causes that could explain it – back pain could very easily be musculoskeletal, but in some cases, it will be heart-related.”

If it doesn’t get better, and following the directions from their GP, people should call emergency services, Goss says.

Leg pain

A gripping or cramping sensation in the calf when walking can be a sign of peripheral arterial disease, which is a heart and circulatory problem, explains Goss. “This is because you’ve got problems with the blood flow, and there’s a build-up of fatty deposits. We focus a lot on peripheral arterial disease happening in your heart, but it can also happen in other blood vessels, such as in your legs. If you notice you’re getting some pain or slight discolouration in your feet, or that just something is not quite right with your legs, make an appointment with your GP, particularly if you have high cholesterol, or a history of heart problems.”

“It’s the equivalent of angina, where you get pain in the chest, but in the legs,” adds Dr Segal. The problem is once you stop walking, the pain often disappears, so people dismiss it.

A choking feeling

Anyone experiencing anything that feels like a restrictive feeling in their throat or choking should call 111, says Goss. “Pain in your throat that may be mistaken for indigestion or heartburn. It might not be heart-related, but it’s definitely one to get checked out, especially if it’s a new symptom and you don’t have a cold or trauma to the throat.”

Sweating profusely

Unless you’re going through menopause or have just exercised, breaking out into a cold sweat or perspiring excessively could be a sign of a heart attack, explains Goss. “If the heart isn’t pumping properly, it will struggle to get blood flow around the body and can set off a nervous response which causes someone to sweat. It tries to tighten everything up to get the blood flow going to where it’s needed. So your blood pressure might go up, and you start to feel a bit cold, or a bit clammy and sweaty.

“In warmer weather, you’ll feel yourself getting a bit sweaty because your heart has relaxed a bit, or your blood pressure has dropped. But if you’re sitting in your front room at a normal temperature and all of a sudden you feel quite cold and clammy, and your breathing gets harder, it may be because your heart has lost blood supply, and needs more oxygen.”

Fainting

Most people are unaware that fainting could be a warning sign for a potentially serious and life-threatening heart condition. In many cases, fainting is the only sign of an abnormal heart rhythm, which is a leading cause of SCA (sudden cardiac arrest), which kills 100,000 people in the UK alone each year, according to the British Heart Foundation.

Excessive fatigue

Feeling worn out after a sleepless night or stressful day is normal. But unusual fatigue might be an early warning sign of a heart attack. Some people suddenly get profound waves of tiredness, which may represent arrhythmia or exhaustion.

“It can start quite gradually,” says Goss. “Feeling very tired all the time, or you get short of breath more quickly, particularly going up stairs or up a hill, that can be a sign there’s something going on with your heart. It could be a faulty valve, or the heart’s not getting enough blood flow to it – and you’re feeling exhausted because your heart is working harder to get oxygen around your body.”

Dizziness

Sudden dizziness or light-headedness could be because the heart isn’t pumping enough blood to the brain, usually a result of an arrhythmia (abnormal heart rhythm), a heart valve condition or even a heart attack.

Feeling sick

“A lot of the time, being nauseous isn’t related to your heart, but if you’re experiencing it, along with the other symptoms like radiating chest pain, it’s because your heart is unhappy and is trying to work on the blood flow. Your body senses something’s not quite right, and then that can affect your stomach, so you feel a bit sick because your body’s struggling,” says Goss.

Swollen ankles

This can be a marker that your heart is not pumping as effectively, says Goss. “Fluid can build because it’s not able to pump blood around properly, and it is common to experience it in your lower limbs. It can sometimes be medication-related or someone might have a problem with their heart like valvular heart disease or heart failure, which can cause fluid to build up.

“Obviously if you get off a plane, and your ankles are swollen, it doesn’t mean you’ve got a heart problem,” agrees Dr Segal, “but it can be an indicator of heart failure and other conditions such as renal failure and liver failure. So get it checked out if it persists.”

Indigestion

Stomach pain which comes in waves can be a sign of a heart attack, and the difficulty is distinguishing between heart pain and indigestion. “It can be quite difficult to tell the difference because the heart, stomach, gullet all lie really close to one another,” says Goss. ‘If you’re having indigestion-type pain and are unsure what is causing it, speak to your doctor as it’s always better to be checked out.”

Grey pallor

People with heart failure can get a bad colour across their face – their skin becomes pasty and grey. Loved ones may look at you and say: “Your colour’s not right.” In some extreme cases, people’s lips go white or bluish. “There are many reasons why that can be benign, but on the other hand, going clammy and pale and grey can be a sign of a heart problem,” says Dr Segal.

Sleeping upright or in a chair

Some elderly people don’t like lying flat because it makes them breathless, which is a sign of fluid building up in the lungs. “Obviously, we all occasionally get up because we can’t sleep,” says Dr Segal. “But if there’s been a persistent change, and the person is now having to prop themselves up, that’s a classic sign the heart is struggling, and they’re unable to lie flat at night comfortably.”