First heart attacks are less likely to kill people in the U.S. than they used to be, researchers said in a new study. The reasons, according to a study in the journal Circulation, are better prevention efforts and improved treatments. Better control of risk factors, researchers said, can prevent heart attacks and lessen the severity of a first attack. Government statistics reported that heart disease deaths in the U.S. have fallen 30% during the past decade. The researchers studied more than 10,000 first-time heart attack patients between the ages of 35 and 74.