Almost a third of patients in England and Wales are being given the wrong initial diagnosis after a heart attack - with women having a far higher chance of being affected, a study suggests.
University of Leeds research examined NHS data on about 600,000 heart attack cases over a period of nine years.
Women were 50% more likely than men to have an initial diagnosis different from their final diagnosis, it said.
NHS England said it was working to improve the diagnosis of heart attacks.
The British Heart Foundation (BHF) is urging people to be aware of the symptoms of a heart attack.
Women 'play down' symptoms
The study, which appears in the European Heart Journal - Acute Cardiovascular Care, looked at the UK national heart attack register and was carried out between April 2004 and March 2013.
It involved 243 NHS hospitals in England and Wales which cared for patients who were aged between 18 to 100 years old when they were admitted.
Researchers found that 198,534 patients were initially misdiagnosed.
Up to 28,000 women die from heart attacks each year in the UK, according to the BHF. There are also about 275,000 female heart attack survivors in the UK.
Dr Sarah Clark, consultant cardiologist at Papworth Hospital, told BBC Radio 4's Today programme that the symptoms of a heart attack can be "very subtle" and, in her experience, men are more likely to report problems than women.
"I have to say I think women tend not to present as frequently as men do, they tend to play down their symptoms... and present later," she said.
Lisa Price, from Bolton, had an ankle operation which resulted in a blood clot which led to a heart attack.
She said women should be made more aware of the differing symptoms.
"The symptoms are not falling to the floor and clutching your chest, they are very different," she said.
"At first the feeling was a real tightness and a crumbling of my ribcage - it was as if I had a small child sitting on me - a child that just would not move. There was such a heavy weight.
"As the actual symptoms progressed it actually turned into a burning. It was as if a burning cannonball had actually been pushed through me and I could feel a huge hole burning right through from my front to my back."
Doctors initially said her symptoms were a result of the operation and told her to take paracetamol, she said.
Heart attack symptoms
- Chest pain - a sensation of pressure, tightness or squeezing in the centre of your chest
- Pain in other parts of the body - it can feel as if the pain is travelling from your chest to your arms (usually the left arm is affected, but it can affect both arms), jaw, neck, back and abdomen
- Feeling lightheaded or dizzy
- Shortness of breath
- Feeling sick (nausea) or being sick (vomiting)
- Overwhelming sense of anxiety (similar to having a panic attack)
- Coughing or wheezing
Although the chest pain is often severe, some people may only experience minor pain, similar to indigestion. In some cases, there may not be any chest pain at all, especially in women, the elderly and people with diabetes.
The BHF, which part-funded the study, says heart attacks can be classified into two main types - STEMI (ST segment elevation myocardial infarction) and NSTEMI (non-ST segment elevation myocardial infarction).
NSTEMI, the more common type, involves a partial blockage of one or more arteries and can cause serious damage to the heart muscle.
A STEMI, which the NHS calls the "most serious type of heart attack", occurs when there is long interruption to the blood supply.
"This is caused by a total blockage of the coronary artery, which can cause extensive damage to a large area of the heart," the NHS explains.
Women who had a final diagnosis of STEMI had a 59% greater chance of a misdiagnosis compared with men, while women who had a final diagnosis of NSTEMI had a 41% greater chance of a misdiagnosis when compared with men.
The BHF's associate medical director Dr Mike Knapton said the diagnosis differences were "alarmingly high" but said better tests were being developed for female heart attack diagnoses.
"This new study highlights the current scale of the issue and confirms more research is urgently needed into tests that will enable earlier and more accurate diagnosis of a heart attack, particularly in women," he added.
Researcher Dr Chris Gale said: "We need to work harder to shift the perception that heart attacks only affect a certain type of person.
"Typically, when we think of a person with a heart attack, we envisage a middle aged man who is overweight, has diabetes and smokes.
"This is not always the case - heart attacks affect the wider spectrum of the population - including women."
An NHS England spokesman said: "Survival rates for heart attacks are the best they have ever been and swift diagnosis and treatment is key to this.
"We are working hard to continually improve tests for accurately diagnosing heart attacks in both men and women so that correct treatment can begin without delay, ensuring the best possible recovery for patients.
"We are also working to increase awareness of signs and symptoms of heart attack amongst both the public and healthcare professionals as this will help speed up diagnosis."