CHICAGO — In just six years, death rates and heart failure in hospitalized heart attack patients have fallen sharply, most likely because of better treatment, the largest international study of its kind suggests. The promising trend parallels the growing use of cholesterol-lowering drugs, powerful blood thinners, and angioplasty, the procedure that opens clogged arteries, the researchers said.

“These results are really dramatic, because, in fact, they’re the first time anybody has demonstrated a reduction in the development of new heart failure,” said lead author Dr. Keith Fox, a cardiology professor at the University of Edinburgh.

The six-year study involved nearly 45,000 patients in 14 countries who had major heart attacks or dangerous partial artery blockages. The percentage of patients who died in the hospital or who developed heart failure was nearly cut in half between 1999 and 2005.

The heart attack patients treated most recently were far less likely to have another attack within six months of being hospitalized when compared to the patients treated six years earlier — a sign that the more aggressive efforts of doctors in the last few years are working. There have been other signs that better treatment of heart patients has been saving lives, but not on a scale as large as this international study, the researchers said.

The new study follows landmark research results in March that showed angioplasty is being overused on people who have chest pain but are not in immediate danger of a heart attack. But this popular procedure, which typically uses stents to keep an unclogged vessel open, is still a powerful tool for saving those who are having a heart attack or are at high risk of one.