Socioeconomic inequalities in quality of care and outcomes among patients with acute coronary syndrome in the modern era of drug eluting stents

Abstract

Background: The rapidly changing landscape of percutaneous coronary intervention provides a unique model for examining disparities over time. Previous studies have not examined socioeconomic inequalities in the current era of drug eluting stents (DES).

Methods and results: We analyzed 835 070 hospitalizations for acute coronary syndrome (ACS) from the Healthcare Cost and Utilization Project across all insurance types from 2008 to 2011, examining whether quality of care and outcomes for patients with ACS differed by income (based on zip code of residence) with adjustment for patient characteristics and clustering by hospital. We found that lower-income patients were less likely to receive an angiogram within 24 hours of a ST elevation myocardial infarction (STEMI) (69.5% for IQ1 versus 73.7% for IQ4, P<0.0001, OR 0.79 [0.68 to 0.91]) or within 48 hours of a Non-STEMI (47.6% for IQ1 versus 51.8% for IQ4, P<0.0001, OR 0.86 [0.75 to 0.99]). Lower income was associated with less use of a DES (64.7% for IQ1 versus 71.2% for IQ4, P<0.0001, OR 0.83 [0.74 to 0.93]). However, no differences were found for coronary artery bypass surgery. Among STEMI patients, lower-income patients also had slightly increased adjusted mortality rates (10.8% for IQ1 versus 9.4% for IQ4, P<0.0001, OR 1.17 [1.11 to 1.25]). After further adjusting for time to reperfusion among STEMI patients, mortality differences across income groups decreased.

Conclusions: For the most well accepted procedural treatments for ACS, income inequalities have faded. However, such inequalities have persisted for DES use, a relatively expensive and until recently, controversial revascularization procedure. Differences in mortality are significantly associated with differences in time to primary PCI, suggesting an important target for understanding why these inequalities persist.

Keywords: acute coronary syndrome; outcomes; quality; socioeconomic status.

Figure 1.

Adjusted procedures by income quartile. Odds ratios for income quartile influencing procedures for patients admitted with ACS from 2008 to 2011, adjusted for age, gender, race, comorbidities, insurance type, and clustering of patients within hospital. The highest income group (quartile 4) was used as the patient reference group. P value for CABG=0.28, P value for DES=0.02, P value for PCI=0.005, P value for any revascularization=0.01, P value for angiogram within 48 hours if NSTEMI=0.18, P value for angiogram within 24 hours if STEMI=0.01, P value for any angiogram=0.07. ACS indicates acute coronary syndrome; CABG, coronary artery bypass graft; DES, drug eluting stents; IQ, income quartile; NSTEMI, non‐ST elevation myocardial infarction; PCI, percutaneous coronary intervention; STEMI, ST elevation myocardial infarction.

Figure 2.

Temporal trends in DES use by income quartile. The percentage of patients who received a DES increased over the time period from 2008 to 2011. Overall, higher‐income quartile was associated with higher DES use regardless of year. DES indicates drug eluting stents; IQ, income quartile.

Figure 3.

Mortality adjusted for revascularization by income quartile. Odds ratios for income quartile influencing mortality for patients admitted with ACS from 2008 to 2011, adjusted for age, gender, race, comorbidities, insurance type, clustering of patients within hospital, and primary PCI. The highest income group (quartile 4) was used as the patient reference group. P value for STEMI <0.0001, P value for STEMI adjusted for 24 hours PCI=0.0003. ACS indicates acute coronary syndrome; IQ, income quartile; PCI, percutaneous coronary intervention; STEMI, ST elevation myocardial infarction.