Use of evidence-based therapies after discharge among elderly patients with acute myocardial infarction

Abstract

Background: Postdischarge use of evidence-based drug therapies has been proposed as a measure of quality of care for myocardial infarction patients. We examined trends in the use of evidence-based drug therapies after discharge among elderly patients with myocardial infarction.

Methods: We performed a cross-sectional study in a retrospective population-based cohort that was created using linked administrative databases. We included patients aged 65 years and older who were discharged from hospital with a diagnosis of myocardial infarction between Apr. 1, 1992, and Mar. 31, 2005. We determined the annual percentage of patients who filled a prescription for statins, beta-blockers and angiotensin-modifying drugs within 90 days after discharge.

Results: The percentage of patients who filled a prescription for a beta-blocker increased from 42.6% in 1992 to 78.1% in 2005. The percentage of patients who filled a prescription for an angiotensin-modifying drug increased from 42.0% in 1992 to 78.4% in 2005. The percentage of patients who filled a prescription for a statin increased from 4.2% in 1992 to 79.2% in 2005. In 2005, about half of the hospitals had rates of use for each of these therapies that were less than 80%. The temporal rate of increase in statin use after discharge was slower among noncardiologists than among cardiologists (3.5%-2.8% slower). The rate of increase was 4.8% slower for among physicians with low volumes of myocardial infarction patients than among those with high volumes of such patients and was 5.7% greater at teaching hospitals compared with nonteaching hospitals.

Interpretation: Use of statins, beta-blockers and angiotensin-modifying drugs increased from 1992 to 2005. The rate of increase in the use of these medications after discharge varied across physician and hospital characteristics.

Figure 1: Use of evidence-based drug therapies after discharge among elderly patients with acute myocardial infarction, from 1992 to 2005. Note: ACE = angiotensin-modifying enzyme, ARB = angiotensin-receptor blocker.

Figure 2: Physician characteristics associated with the temporal rate of increase in the use of β-blockers (A, B) and statins (C, D) from 1992 to 2005. The plotted probabilities of medication use after discharge were derived from the fitted multilevel regression model and represent the predicted probability at an average hospital, for a patient of average age, all of whose risk factors were set to absent, and whose values for the other physician and hospital characteristics were set to their reference levels.