This study is part of an ongoing population-based investigation that is examining changes over time in the incidence, in-hospital, and long-term case-fatality rates of residents of the Worcester metropolitan area hospitalized with a primary or secondary discharge diagnosis of AMI from all greater Worcester Standard Metropolitan Statistical Area (SMSA) hospitals.13–17
The medical records of residents of the Worcester SMSA (1990 census estimate = 437,000) hospitalized for possible AMI were individually reviewed and validated according to predefined diagnostic criteria that have been previously described.13–15,17
In brief, the criteria consisted of a positive clinical history, serum cardiac enzyme level elevations, and serial electrocardiographic findings consistent with AMI. At least 2 of these 3 criteria needed to be satisfied for study inclusion. All autopsy-proven cases of AMI were included. Patients transferred from another health care facility, irrespective of geography, and perioperative-associated cases of AMI were excluded. We restricted the study sample to patients hospitalized with AMI in six 1-year periods between 1990 and 1999 for the purposes of examining recent and decade-long trends in our principal study endpoints.
To examine possible age differences in the receipt of diagnostic and revascularization procedures, 4 age-specific strata in women and men were created. These included patients <55 years (139 women, 544 men), 55 to 64 years (218 women, 564 men), 65 to 74 years (521 women, 707 men), and those 75 years and older (1,159 women, 830 men). The mean ages of these comparison groups were 46, 60, 71, and 83 years, respectively, in women, and 47, 60, 70, and 81 years, respectively, in men.
The medical records of women and men of all ages from the Worcester SMSA who were hospitalized with validated AMI during the periods under study were reviewed by trained physician and nurse study coordinators. Data collected from the review of medical charts included the following: history of angina, diabetes, hypertension, stroke, and congestive heart failure; AMI-associated characteristics including order (initial versus prior), type (Q wave vs non–Q wave) and location (anterior vs inferior/posterior); and occurrence of in-hospital complications such as heart failure and cardiogenic shock.18,19
Information was collected about the diagnostic procedures and coronary revascularization approaches used during the index hospitalization. Both nurses' and physicians' test-ordering notes were reviewed to ascertain this information. The diagnostic procedures examined in this study included echocardiography, exercise treadmill testing (ETT), and cardiac catheterization. The revascularization procedures examined included percutaneous coronary interventions (PCI) and coronary artery bypass grafting (CABG).
The distribution of selected characteristics between women and men within selected age strata (<55, 55–64, 65–74, ≥75 years) were compared using χ2 tests of statistical significance for discrete variables and analysis of variance for continuous variables. The Mantel-Haenszel χ2 test was used to examine trends across the different age groups in terms of clinical characteristics and the use of each of the procedures over the 10-year study period. A multivariable logistic regression analysis was used to examine the independence of the association between age and gender and the receipt of diagnostic and interventional procedures during the index hospitalization while controlling for potentially confounding variables. Age was controlled for as a continuous variable in the regression analyses, including comparisons between women and men in the same age group. Race was not included as a controlling variable because the vast majority of study patients were white. The variables controlled for in these analyses included medical history (presence of 1 or more of the following conditions: angina, diabetes mellitus, hypertension, stroke, or heart failure), AMI order (initial vs prior), AMI type (Q wave vs non–Q wave) and AMI location (anterior vs inferior/posterior), clinical complications (occurrence of heart failure or cardiogenic shock), length of stay, and hospital survival status. These variables were included because of their potentially confounding effects and because of differences in their distribution between respective comparison groups. All tests of statistical significance were 2- tailed.