People are most at risk of dropping dead in the first month after a heart attack, a new study finds, but the most effective treatment to prevent this isn’t done that early on because it, too, is considered riskiest then. The new research should prompt doctors to rethink how patients are treated in those crucial early days. The rate of sudden death was 10 times higher in the first month after a heart attack compared to two years later, researchers report in Thursday’s New England Journal of Medicine.