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

Background Limited population-based data are available that describe tempor al and recent trends in the incidence and case-fatality rates in patients w ith primary ventricular fibrillation (VF) complicating acute myocardial inf arction (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 Worcest er residents hospitalized with a validated uncomplicated AMI (n = 5020) in all hospitals in the Worcester, Massachusetts, metropolitan area (1990 cens us population = 437,000) during 111-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 cha nge significantly over the 22-year period under study. The overall in-hospi tal case-fatality rate of patients with primary VF was 44%, which was signi ficantly greater in comparison with AMI patients in whom VF did not develop (5%). Hospital mortality rates associated with primary VF declined over ti me. Improved survival was observed in patients who had primary VF in the 19 90s after adjusting for potential prognostic confounders. Conclusions The results of this community-wide study failed to indicate cha nges over time in the incidence rates of primary VF in patients hospitalize d with AMI between 1975 and 1997. On the other hand, hospital death rates i n patients with primary VF have shown encouraging declines during more rece nt periods. These mortality trends are likely to be the results of improvem ents in the treatment and more careful surveillance of patients with AMI.