A silent heart attack is defined as a heart attack you didn’t realise you had.
Also known as a silent myocardial infarction (SMI), they are said to account for about half of all heart attacks, but are mistaken for less serious conditions.
The symptoms can feel mild, lacking the intensity of classic heart attack signs such as extreme chest pain, tightness, pressure and stabbing pain in the arm, neck or jaw.
They can include mild pain or discomfort in the throat or centre of the chest.
“SMI symptoms can feel so mild, and be so brief, they often get confused for regular discomfort or another less serious problem,” Dr Jorge Plutzky told Harvard Health Publishing.
Nonetheless, SMIs increase your risk of dying from coronary heart disease.
Harvard cites a study of 2,000 people who initially didn’t have heart problems. Ten years later, eight percent of the subjects had myocardial scars, which proved they had suffered an attack.
Incredibly, 80 percent of those people were unaware they’d had any kind of heart issue.
Silent heart attacks are particularly dangerous because sufferers don’t seek medical treatment afterwards.
“SMI often leaves scarring and damage to the heart, which, combined with the fact that many people who have an SMI don’t seek immediate care, can further raise a person’s risk of a second and potentially more harmful heart attack,” Dr Plutzky told Harvard.
The British Heart Foundation quotes a Norwegian study which found that silent heart attacks happened more in women, because women’s pain threshold is higher, so they may be less likely to realise they are having an attack.
The researchers had 4,000 adults place their hand in ice-cold water for as long as possible to ascertain their pain threshold.
Those who had had a silent heart attack – eight percent of participants – kept their hand in the water for much longer than the 4.7 percent of participants who’d had a heart attack and recognised the pain.
While female participants had experienced less heart attacks than men, a large proportion of those were silent – 75 percent compared to 58 percent in men.
The foundation’s Associate Medical Director, Dr Mike Knapton, said more needs to be done to help understand what was causing people to miss the signs of a heart attack.
“Silent heart attack is a major problem in the UK. It is worryingly common for patients to visit their GP having already had a heart attack but they are completely unaware of it.
“Pain threshold may well be the reason for some people not noticing the symptoms of a heart attack, but more research needs to be done to help us understand what’s causing others to miss the signs,” he said.
“Despite coronary heart disease killing more than twice as many women than breast cancer, we know that women often don’t realise they can be at risk. This makes them more likely to ignore the symptoms and delay getting help.”
Research from the British Health Foundation found that women were 50 percent more likely than men to be given incorrect diagnosis following a heart attack, increasing their risk of death.
Six lifestyle factors, including high blood pressure and high cholesterol, can increase your risk of developing heart disease.
