Presence of Aromatase enzyme in males : Result of Natural Selection
Estrogen has other functions in males; it is very misleading to attribute the ability in males to synthesize estrogen to effects on heart attack chances. The relationship between estrogen and cardiovascular disease risk is also very complicated, and current guidelines do not suggest estrogen replacement as a preventative treatment for heart disease.

A better explanation for increased male risk of heart attack might be the increased levels of testosterone, but the data on that are mixed as well.