The Mantel-Haenszel x2 test for trend was used to analyze the change in the proportion of patients tested for LVEF over time, and the Pearson x2 test was used to compare proportions. Logistic regression was used to examine the independent association between demographic and clinical variables, and testing for LVEF within 30 days after index MI. Candidate predictor variables included age, sex, testing for LVEF within 1 year prior to incident MI, history of congestive heart failure before the index MI, diabetes mellitus, hypertension, comorbidity, peak CK ratio, evaluation by a cardiologist, use of reperfusion therapy, length of hospital stay > 10 days, and year of the MI. Interactions between age and year of the MI and sex and year of the MI were examined.
Cox proportional hazards models were constructed to examine the association between LVEF evaluation and mortality. Results of the final models were summarized by presenting the relative risk and 95% confidence intervals (CIs). A p value of 0.05 was selected for the threshold of statistical significance except for interaction testing, when values up to 0.10 were accepted. Analyses were performed using SAS version 8.2 (SAS Institute; Cary, NC) and S-Plus Version 6.0.4 (Insightful Corporation; Lucent Technologies; Seattle, WA). The study was approved by the Mayo Foundation Institutional Review Board.