The case for unstable angina pectoris as a primary end point in primary prevention studies
E J Whitney1, C L Shear, G Mantell
1Cardiology Service, Wilford Hall United States Air Force Medical Center, San Antonio, Texas 78236.
Insights
New primary end points for coronary artery disease (CAD) prevention trials are needed. Unstable angina is increasingly common and should be considered, as acute myocardial infarction (AMI) trends are inconsistent.
Area of Science:
- Cardiology
- Clinical Trials
- Public Health
Background:
- Coronary artery disease (CAD) mortality has significantly decreased in the U.S. over the last 20 years.
- Trends in acute myocardial infarction (AMI) incidence are less consistent, while CAD hospital discharge rates have risen.
- Lifestyle changes and medical interventions contribute to declining CAD mortality and incidence.
Purpose of the Study:
- To review primary end point definitions in CAD prevention trials.
- To analyze trends in CAD mortality, incidence, and hospital discharges.
- To determine if new primary end points should be considered for future trials.
Main Methods:
- Review of primary end point definitions in previous CAD prevention trials.
- Analysis of temporal trends in CAD mortality, AMI incidence, and hospital discharge rates.
- Evaluation of the changing landscape of CAD presentation, including angina and unstable angina.
Main Results:
- CAD mortality has declined dramatically, but AMI incidence shows less consistent decreases.
- CAD hospital discharge rates have increased, with a notable rise in unstable angina cases (4% in 1980 to 25% in 1989).
- AMI stabilization in discharge rates contrasts with increasing rates for angina and unstable angina.
Conclusions:
- Solely relying on AMI as a primary end point may not accurately reflect the current U.S. CAD experience.
- Unstable angina, due to its increasing prevalence and high-risk pathology, warrants serious consideration as a primary end point.
- Improved diagnostic methods for unstable angina support its use in future primary prevention trials.
Abstract:
Coronary artery disease (CAD) primary end point definitions used in previous prevention trials are reviewed, as well as trends over time for CAD mortality, incidence and hospital discharges to see if new primary end points should be considered. CAD mortality has shown a dramatic decline in the U.S. in the last 20 years, whereas the decrease in the incidence of acute myocardial infarction (AMI) is less consistent. The decline in CAD incidence and mortality has been attributed to changes in lifestyle and increased medical/surgical intervention. Hospital discharge rates for CAD have risen during the past decade. In addition, although the rate of discharge for AMI appears to have stabilized, the rates for angina, and more dramatically for unstable angina, have increased. Unstable angina made up 4% of CAD discharges in 1980, and increased to 25% of CAD discharges in 1989. Because of these trends, future trials that rely solely on AMI as a primary end point will not reflect the actual experience with CAD presentation in the U.S. Given the greater availability of methods to diagnose unstable angina more accurately, and because of its high risk pathology, it is concluded that unstable angina should receive serious consideration as a primary end point in future primary prevention trials.
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