Evaluating the effect on patient outcomes of appropriate and inappropriate use of beta-blockers as secondary prevention after myocardial infarction in a medicaid population.

BACKGROUND

Acute myocardial infarction (AMI) is associated with high mortality in the United States. Beta-blockers have been shown to reduce mortality and reinfarction rates when used for long-term prevention after an AMI. However, this therapy is both underused and misused. The effect of this practice on outcomes needs to be investigated.

OBJECTIVE

This study was undertaken to evaluate the effect on patient outcomes (ie, fatality, health care utilization, and costs) of appropriate and inappropriate prescribing of beta-blocker therapy after AMI in a Medicaid population aged <65 years.

METHODS

Data for 1 year before and after AMI were extracted from West Virginia Medicaid claims from January 1, 1996, to June 30, 2001. Information was obtained regarding prescriptions for beta-blockers for these patients within 90 days after discharge. Patients were divided into 2 groups: those who were prescribed therapy appropriately and those who were prescribed therapy inappropriately (underuse or misuse). Fatality rates during 1 year after discharge were compared using chi-square analysis. The study used regression analysis to model health care utilization and costs as a function of appropriately/inappropriately prescribed groups.

RESULTS

Data were assessed for 488 eligible patients (mean [SD] age, 53.70 [8.14] years; 246 men [50.4%], 242 women [49.6%]). Overall, 309 patients (63.3%) had appropriate prescribing of beta-blockers; at the end of 1 year, these patients had a significantly lower all-cause death rate compared with those who were prescribed therapy inappropriately (P = 0.030). Although the cardiac death rate was slightly lower for the appropriate group, the difference was not statistically significant. The appropriately prescribed group had significantly higher health care utilization in the follow-up period (P < 0.050 for hospital visits, emergency department visits, and length of stay). These groups demonstrated differences in a few variables at baseline (age, presence of absolute contraindications, presence of hypertension, number of noncardiac admissions before AMI, and use of beta-blockers before AMI: all, P < 0.050), implying different severity levels. Patient health status at the time of the incident AMI had a confounding effect on health care utilization, and there were indications that the appropriate group had greater severity compared with the inappropriate group.

CONCLUSIONS

Appropriate prescribing of beta-blockers for secondary prevention after an AMI was associated with better survival in this population. However, the effects of inappropriate and appropriate beta-blocker prescribing on health care utilization need to be evaluated prospectively so that all severity indicators can be properly adjusted.