The procedures used to assemble the MI incidence cohort have been reported in detail elsewhere. Briefly, all incident MIs between 1979 and 1998 were ascertained from indexes of medical diagnosis and hospital discharges using standardized epidemiologic criteria, relying on cardiac pain, creatine phos-phokinase enzyme values, and Minnesota coding of the ECG.
Baseline Characteristics and End Point Definitions and Ascertainment
Because of the change over time in the normal values and corresponding ranges, peak creatine kinase (CK) was defined as twice the upper limit of normal for each unit in use within a corresponding time frame. Comorbidity was measured using the Charlson index. Reperfusion therapy was defined as thrombolysis or coronary angioplasty within 24 h after symptom onset. History of smoking was analyzed while combining former and current smoking. Clinician’s diagnoses were used to ascertain hyperlipidemia, hypertension, and diabetes mellitus.
The use of inpatient and outpatient tests for measurement of LVEF was ascertained by electronic queries of the databases of the echocardiography and nuclear cardiology laboratory databases for the entire study period and of the cardiac catheterization database beginning in 1987. A manual search of the catheterization laboratory database was performed for the years prior to 1987.