BACKGROUND:

The decline in coronary heart disease mortality in the United States may be due to decreasing incidence of clinically apparent coronary heart disease or increasing survival from its first clinical appearance or both. Prior to 1987, few data were available to confirm either one directly.

However, increased risk, decreased medical care, or both may predispose the Mexican-American population to increased recurrence of myocardial infarction and decreased post myocardial infarction survival, and an overall greater mortality among survivors of myocardial infarction, than are observed for

Anglos in the same community setting. The significance of the potential results lies most importantly in the following aspects of this research:

estimation of the community-based incidence of hospitalization for suspect, definite or possible myocardial infarction; precise determination of recurrence rates and survival curves after myocardial infarction in community-wide hospital-based cohorts; analysis of the relation of the above to risk status as ascertained at hospitalization and to health care and preventive practices assessed periodically post-myocardial infarction; and comparison of these observations between Anglos and Mexican-Americans, a group of special interest and concern because of expected differences in natural history of coronary heart disease and near total lack of the relevant data.

DESIGN NARRATIVE:

Patients hospitalized for acute coronary heart disease (CHD) in seven acute care hospitals in Nueces County, Texas were identified by active concurrent case registration. Baseline data on clinical, prognostic and sociodemographic characteristics of these patients at the time of the event were collected from the medical record and by interview with the patient. Patients with events meeting diagnostic criteria for acute myocardial infarction (MI) were followed directly through contacts at three months post-discharge and at the anniversary of discharge thereafter to ascertain vital status and to collect information about recurrent myocardial infarction, other changes in health status, and health care practices in the interim. Endpoints included all-cause mortality and deaths attributed to coronary heart disease, and fatal and non-fatal myocardial infarction. Data analysis included examination of survival and recurrence of myocardial infarction for the entire cohort of myocardial infarction patients and within ethnic groups; evaluation of potential prognostic factors within and between ethnic groups; and comparison of survival and myocardial infarction recurrence between ethnic groups after adjustment for both baseline and time-dependent covariates.

The study was renewed in 1992 to continue to identify hospitalized MI and CHD mortality as well as angioplasty, and bypass surgery among Mexican-Americans and non-Hispanic Whites. The investigators calculated incidence rates for hospitalized MI, for the use of cardiac revascularization, and rates for post-MI mortality, and for both all cause and CHD mortality in the community. They also described trends in these aspects of CHD over an eight year period and determined if ethnic differences existed.