The research, published in the British Medical Journal, looked at more than 800,000 men and women who suffered heart attacks between 2002 and 2010.
They found that fewer heart attacks occurred in later years and, of those that did occur, fewer were fatal.
Researchers say improvements in NHS care and better prevention measures have contributed to the decline.
The Oxford researchers used national hospital and mortality data to analyse 840,175 men and women in England who had suffered a total of 861,134 heart attacks over eight years.
Comparing 2002 with 2010, they found death rates falling by 50% in men (78.7 per 100,000 population to 39.2) and by 53% in women (37.3 per 100,000 to 17.7).
A declining mortality rate was also seen in all age groups and for both sexes.