Fewer women who suffer a heart attack would die if they were given the same treatments as men, according to researchers.
They analysed the outcomes of 180,368 Swedish patients who suffered a heart attack over a 10-year period.
Women were two times more likely to die from the most serious type of heart attack than men in the year after having one.
Researcher believe it is due to differences in the care given.
The team from the University of Leeds and the Karolinska Institute in Sweden analysed data from Sweden's online cardiac registry.
They found women were on average less likely than men to receive the recommended treatments after a potentially fatal type of heart attack called a STEMI.
This is the most serious type of heart attack where the coronary artery is completely blocked by a blood clot and it requires urgent treatment.
In the study, women who had a STEMI were 34% less likely to receive procedures which clear blocked arteries, such as bypass surgery and stents.
They were also 24% less likely to be prescribed statin medication, which helps to prevent a second heart attack, and 16% less likely to be given aspirin, which helps to prevent blood clots.
This is despite guidelines suggesting all three treatments should be given to both genders.
The study found that when women did receive all the recommended treatments, the gap in mortality between the sexes decreased in almost all circumstances.
Roughly 124,000 men and 70,000 women are hospitalised for heart attacks in the UK per year.
Co-author of the study Prof Chris Gale, from the University of Leeds, said gender biases for heart disease occur in the UK too.
"There's misconception amongst the general public and healthcare professionals about what heart attack patients are like.
"Typically, when we think of a heart attack patient, we see 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."
Prof Gale said that from their very first point of contact with healthcare professionals, women are less likely to receive the same diagnostic tests, leading them to be 50% more likely to be initially misdiagnosed.
"That then feeds the whole pathway of care," he said. "If you missed the first, earliest opportunity for care - you're much more likely to miss the next point of contact - and it all adds up cumulatively and leads to a greater mortality."
'Women are dying'
The study also found that women were more likely to suffer from other illnesses, such as diabetes and high blood pressure, but these did not fully account for the difference in mortality.
"Sweden is a leader in healthcare, with one of the lowest mortality rates from heart attacks, yet we still see this disparity in treatment and outcomes between men and women," added Prof Gale.
Prof Jeremy Pearson, of the British Heart Foundation, which part-funded the work, said: "The findings from this research are concerning.
"We urgently need to raise awareness of this issue as it's something that can be easily changed. By simply ensuring more women receive the recommended treatments, we'll be able to help more families avoid the heartbreak of losing a loved one to heart disease."