Changes over time in the incidence and case-fatality rates of primary ventricular fibrillation complicating acute myocardial infarction: perspectives from the Worcester Heart Attack Study.

BACKGROUND: Limited population-based data are available that describe temporal and recent trends in the incidence and case-fatality rates in patients with primary ventricular fibrillation (VF) complicating acute myocardial infarction (AMI). The purpose of this study was to describe changes over a 22-year period (1975 through 1997) in the incidence and hospital case-fatality rates of primary VF complicating AMI from a multihospital, community-wide perspective. METHODS AND
RESULTS: This was an observational study of metropolitan Worcester residents hospitalized with a validated uncomplicated AMI (n = 5020) in all hospitals in the Worcester, Massachusetts, metropolitan area (1990 census population = 437,000) during 11 1-year periods between 1975 and 1997. The overall incidence rate of primary VF complicating AMI was 4.7%. The crude as well as multivariable adjusted odds of the development of VF did not change significantly over the 22-year period under study. The overall in-hospital case-fatality rate of patients with primary VF was 44%, which was significantly greater in comparison with AMI patients in whom VF did not develop (5%). Hospital mortality rates associated with primary VF declined over time. Improved survival was observed in patients who had primary VF in the 1990s after adjusting for potential prognostic confounders.
CONCLUSIONS: The results of this community-wide study failed to indicate changes over time in the incidence rates of primary VF in patients hospitalized with AMI between 1975 and 1997. On the other hand, hospital death rates in patients with primary VF have shown encouraging declines during more recent periods. These mortality trends are likely to be the results of improvements in the treatment and more careful surveillance of patients with AMI.