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First-time heart attacks in the United States aren’t as deadly now as they have been in past decades, a long-running study finds.

“We know that deaths from heart disease are going down,” said Dr. Merle Meyerson, director of the cardiovascular disease prevention program at Columbia University’s St. Luke’s-Roosevelt Hospital, and lead author of a report in the Jan. 20 issue of Circulation. “One reason why is that heart attacks are less severe. People are not coming in with these massive heart attacks that are killing them.”

The study, with data on more than 10,000 first heart attacks that occurred in four widely separated U.S. areas, found only a marginal decrease in the heart attack death rate — from 5.3 percent in 1987 to 3.8 percent in 2002. That is of only “borderline statistical significance,” Meyerson said.

But analysis of 20 indicators of severity — such as the damage-indicating changes seen in electrocardiograms, or biomarker molecules released by damaged heart tissue — show a clear trend toward lowered severity, she said.

For example, heart attacks with elevations in the ST-designated portion of the ECG, an indicator of severe damage, were seen in 27.7 percent of attacks in 1987 and 20.9 percent in 2002, an average reduction of 1.9 percent per year.

The percentage of cases of cardiogenic shock, in which the heart is so damaged that it cannot pump blood to the body, decreased by 5.7 percent per year, while the percentage of cases with abnormal biomarkers such as creatine kinase or troponin decreased by a modest, but statistically significant, 0.7 percent a year.

The finding comes from the ongoing Atherosclerosis Risk in Communities Study, done in North Carolina, Maryland, Minnesota and Mississippi. It includes rural, city and suburban areas, so the findings show what is happening all over the country, Meyerson said.

It’s not clear why the decrease has occurred, she said. “It could be better preventive measures, reducing risk factors such as high blood pressure and obesity, or it could be better treatment in the hospitals,” she sad. “While this study doesn’t say it, it points to some influence from both. We need more research to answer the question.”

One factor that does not seem to have improved is public awareness of the symptoms of a heart attack and the need to call for medical help quickly, Meyerson said. “The time to get to the hospital after symptoms begin has not improved,” she said. There was no significant change in the percentage of people who arrived at a hospital less than two hours after the onset of symptoms — about one in every three cases.

Most people do know that crushing chest pain is a clear warning signal, but “it’s not always crushing pain,” Meyerson said. “It can be a feeling of indigestion or shortness of breath, lightheadedness or discomfort in another part of the body.”

When there is uncertainty, it is better to act than to do nothing, she said. “If you are having chest pain with exertion, chest pain that comes and goes, with shortness of breath, it is always best to call for help or go to the hospital if you are near one,” she added.

Medical authorities say it is best to call for help by dialing 911. Emergency medical personnel can arrive in minutes and begin treatment immediately.

“This study offers an opportunity to get the message out,” said Dr. Alice K. Jacobs, a professor of medicine at Boston University and past president of the American Heart Association. “If you get to the hospital faster, the chance of a better outcome is improved. That is an important message for the public.”

(Source: Merle Meyerson, M.D., director, cardiovascular disease prevention program, St. Luke’s-Roosevelt Hospital, New York City; Alice K. Jacobs, M.D., professor, medicine, Boston University; Jan. 20, 2009, Circulation)