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Periods of differing mortality distribution during the first year after acute myocardial infarction
Insights
Mortality after acute myocardial infarction (AMI) is not a single exponential pattern. This study identified distinct early and late periods of mortality, aiding in better patient follow-up and management strategies.
Area of Science:
- Cardiology
- Public Health
- Biostatistics
Background:
- Traditional modeling of post-acute myocardial infarction (AMI) mortality uses a single exponential function.
- This approach may not fully capture the dynamic nature of mortality risk within the first year following AMI.
Purpose of the Study:
- To investigate if distinct mortality patterns exist during the first year after AMI.
- To identify specific time periods with differing mortality distributions in three distinct patient populations.
Main Methods:
- Analysis of mortality data from 3 independent patient cohorts (San Diego, Vancouver, Copenhagen) admitted within 24 hours of symptom onset.
- Exclusion of in-hospital deaths within 24 hours and non-cardiac or unknown causes of death.
- Application of changepoint analysis to identify shifts in mortality rates over the first year post-AMI.
Main Results:
- The overall hypothesis of a single exponential mortality rate throughout the first year post-AMI was rejected.
- Changepoints identified at approximately 21 days (combined data) divided the year into two periods where exponential mortality was not rejected.
- Mortality rates were 11.4% between 2-21 days and 10.5% between 3 weeks and 1 year, with 50% of deaths occurring by day 19 and 75% by day 100.
Conclusions:
- Mortality following AMI exhibits distinct patterns in the early (first 3 weeks) and later (3 weeks to 1 year) periods.
- These findings refine the understanding of the natural history of AMI.
- Identification of these periods supports optimized follow-up and risk management strategies for patients post-AMI.
Abstract:
The mortality rate after acute myocardial infarction (AMI) has generally been modeled by a single exponential function. The present study was undertaken to determine, in 3 different populations, whether or not periods exist during the first year after AMI which have mortality distributions that differ from this pattern. The 3 patient populations included San Diego (346 patients, 71 deaths), Vancouver (704 patients, 146 deaths), and Copenhagen (1,140 patients, 262 deaths). Hospital admission was within 24 hours of the onset of symptoms, and patients dying within the first 24 hours after hospital admission or of noncardiac or unknown causes were not analyzed. The mortality between 2 and 21 days in the combined data base was 11.4% (range 10.9 to 11.7) and from 3 weeks to 1 year 10.5% (range 9.0 to 11.3). A high degree of similarity was noted among the shapes of the 3 survival curves. The hypothesis of an exponential mortality rate during the entire first year was rejected. Using a special statistic, changepoints at days 17, 23, and 24 in the 3 populations (21 days for the combined data base) were identified and used thereafter to divide the year into 2 separate periods of mortality within which exponentiality for the mortality rate was not rejected. The point by which exactly 50% of deaths had occurred was day 19, with 75% of deaths occurring by day 100. These data further define the natural history after AMI and indicate optimal follow-up periods for short- and longer-term management strategies based on risk assessment or trials of risk reduction after AMI.