Hospital Variation in Adherence Rates to Secondary Prevention Medications and the Implications on Quality

Abstract

Background: Medication adherence is important to improve the long-term outcomes after acute myocardial infarction (MI). We hypothesized that there is significant variation among US hospitals in terms of medication adherence after MI, and that patients treated at hospitals with higher medication adherence after MI will have better long-term cardiovascular outcomes.

Methods: We identified 19 704 Medicare patients discharged after acute MI from 347 US hospitals participating in the ACTION Registry-GWTG (Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With the Guidelines) from January 2, 2007, to October 1, 2010. Using linked Medicare Part D prescription filling data, medication adherence was defined as proportion of days covered >80% within 90 days after discharge. Cox proportional hazards modeling was used to compare 2-year major adverse cardiovascular events among hospitals with high, moderate, and low 90-day medication adherence.

Results: By 90 days after MI, overall rates of adherence to medications prescribed at discharge were 68% for β-blockers, 63% for statins, 64% for angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, and 72% for thienopyridines. Adherence to these medications up to 90 days varied significantly among hospitals: β-blockers (proportion of days covered >80%; 59% to 75%), statins (55% to 69%), thienopyridines (64% to 77%), and angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (57% to 69%). Compared with hospitals in the lowest quartile of 90-day composite medication adherence, hospitals with the highest adherence had lower unadjusted and adjusted 2-year major adverse cardiovascular event risk (27.5% versus 35.3%; adjusted hazard ratio, 0.88; 95% confidence interval, 0.80-0.96). High-adherence hospitals also had lower adjusted rates of death or readmission (hazard ratio, 0.90; 95% confidence interval, 0.85-0.96), whereas there was no difference in mortality after adjustment.

Conclusions: Use of secondary prevention medications after discharge varies significantly among US hospitals and is inversely associated with 2-year outcomes. Hospitals may improve medication adherence after discharge and patient outcomes through better coordination of care between inpatient and outpatient settings.

Keywords: medical adherence; myocardial infarction; patient outcomes.

Figure 1. Study Population

This figure depicts the final study population, from the initial cohort, through exclusions. ACEI indicates angiotensin-converting enzyme inhibitor; AMI, acute myocardial infarction; ARB, angiotensin receptor blocker; CABG, coronary artery bypass grafting; CMS, Centers for Medicare & Medicaid Services

Figure 2. Hospital Variation in 90-day Adherence to Individual Medications

Unadjusted hospital variation in 90-day adherence (PDC >80% vs. ≤80%) to individual medications. PDC indicates proportion of days covered

Figure 3. MACE by Hospital-level 90-day Composite Adherence Rates

Long-term cumulative incidence Kaplan-Meier MACE estimates by hospital 90-day composite adherence groups.

Figure 4. Two-year Outcomes According to Hospital Adherence Classification

A forest plot of unadjusted and adjusted MACE, mortality, and death or all-cause readmission by hospital-level 90-day composite adherence.

Figure 5. Mortality by Hospital-level 90-day Composite Adherence Rates

Long-term cumulative incidence Kaplan-Meier Mortality estimates by hospital 90-day composite adherence groups.

Figure 6. Mortality or All-cause Readmission by Hospital-level 90-day Composite Adherence Rates

Long-term cumulative incidence Kaplan-Meier mortality or all-cause readmission by hospital-level 90-day composite adherence groups. CI indicates confidence interval; HR, hazard ratio; MACE, major adverse cardiovascular event