The study population consisted of greater Worcester residents hospitalized with a discharge diagnosis of AMI at all teaching and community hospitals in the Worcester metropolitan area during the 15 individual study years of 1975 (n=781), 1978 (n=845), 1981 (n=998), 1984 (n=714), 1986 (n=765), 1988 (n=659), 1990 (n=766),1991 (n=848), 1993 (n=953), 1995 (n=949), 1997 (n=1,059), 1999 (n=1,027), 2001 (n=1,239), 2003 (n=1,157), and 2005 (n=903). There were originally 16 hospitals included in this population-based investigation but there are presently 11 due to hospital closures or conversion to chronic care or rehabilitation facilities. Potentially eligible patients were identified through the review of computerized hospital databases of patients with International Classification of Disease discharge diagnoses consistent with the possible presence of AMI (e.g., AMI, unstable angina). The medical records of all potentially eligible patients, who had to be residents of the Worcester metropolitan area since this study is population-based, were reviewed in a standardized manner and the diagnosis of AMI was confirmed according to pre-established criteria that have been previously described (15 (link)-17 (link)).
Cardiogenic shock was defined as a systolic blood pressure of less than 80 mm Hg in the absence of hypovolemia and associated with cyanosis, cold extremities, changes in mental status, persistent oliguria, or congestive heart failure (6 (link),7 (link)). The definition of cardiogenic shock remained the same during all periods studied. This disorder was defined so that patients with classic signs and symptoms of this clinical syndrome would be included.