I'm guessing it's a combination. Heart attack signs and symptoms are different for men and women. But most of the awareness and training, especially in the past, has been more focused on the typically male symptoms.

Add to that the likely facts that 1) women doctors are, on average, more recently trained than men doctors; 2) women doctors are probably far more likely to be aware of the differences in symptoms between the traditionally discussed symptoms and those that are specific to women, simply from a self-interest perspective; 3) men are likely to be a higher percentage of heart attack patients, so the effect of fewer men being as aware of women-specific symptoms of heart attacks would be amplified by the relative frequency of the occurrences (ie, they see few female heart attacks and so the differences in appropriate treatment are less likely to sink in with someone who doesn't have a personal awareness ("what if this were me having the heart attack?")).

But yes I agree it's too bad these topics were skipped in the article in favor of less likely differences (such as "women are better doctors"--something that I wonder if it's controlled for age, but might just be the effect of the fact that women who do make it through medical school and continue to practice are probably just far more driven and serious about the career than similar men, because the obstacles women face in reaching the same point in their career are much higher, so the women who do make it through will naturally be better doctors than the "average" man doctor).