Long-term mortality after first Acute Myocardial Infarction in the light of changing therapeutic guidelines and diagnostic criteria between 1995 and 2003

Background: The introduction of new invasive therapies for acute myocardial infarction and new medication schemes for secondary prevention is thought to increase life expectancy in 28-day survivors of a first myocardial infarction. The present study examined mortality and re-infarction rate of those patients in the light of changed therapeutic guidelines. Methods: Cases of 25 to 74 year old 28-day survivors of a first definite AMI based on MONICA criteria were identified in the Coronary Event Registry in Augsburg, Southern Germany, who had their index event between the 1st of January 1995 and the 31st of December 2003. Mortality and re-infarction rates were calculated for 1 year, 3 years and total follow-up. Cox models were built to compare the rates of persons, who suffered the index event between 1995 and 1999 (Study period 1) with those who had their first AMI between 2000 and 2003 (Study period 2). Results: Crude mortality was higher in Study period 1 than in Study period 2 and higher for women than for men. Re-infarction rates remained stable for men during both study periods, but women from Study period 1 had a much higher re-infarction rate than women in Study period 2. The hazard ratios showed no significant differences for mortality and re-infarction in men. Hazard ratios of re-infarction in women were significantly reduced, but have to be treated with caution as the number of re-infarctions during Study period 2 was very small. Mortality hazard ratios in women were also not significant. Conclusions: When comparing the time periods before and after the introduction of new therapeutic guidelines, an effect on mortality or re-infarction rate cannot be established. Several reasons are probably responsible for this finding. The population of patients has changed with respect to their risk factors and new diagnostic criteria may have also contributed. Further studies are needed to illuminate these questions