Outcomes and Resource Utilization in ST-Elevation Myocardial Infarction in the United States: Evidence for Socioeconomic Disparities

Study Questions:

Socioeconomic status (SES) as reflected by residential zip code status may detrimentally influence a number of prehospital clinical, access-related, and transport variables that influence outcome for patients with ST-segment elevation myocardial infarction (STEMI) undergoing reperfusion. What is the impact of SES on in-hospital mortality, timely reperfusion, and cost of hospitalization following STEMI?


The authors used the 2003–2011 Nationwide Inpatient Sample database for this analysis. All hospital admissions with a principal diagnosis of STEMI were identified using ICD-9 codes. SES was assessed using median household income of the residential zip code for each patient.


There was a significantly higher mortality among the lowest SES quartile as compared to the highest quartile (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.06-1.17). Similarly, there was a highly significant trend indicating a progressively reduced timely reperfusion among patients from lower quartiles (OR, 0.80; 95% CI, 0.74-0.88). In addition, there was a lower utilization of circulatory support devices among patients from lower as compared to higher zip code quartiles (OR, 0.85; 95% CI, 0.75-0.97). The mean adjusted cost of hospitalization among quartiles 2, 3, and 4, as compared to quartile 1 was significantly higher by $913, $2,140, and $4,070, respectively.


Patients residing in zip codes with lower SES had increased in-hospital mortality and decreased timely reperfusion following STEMI as compared to patients residing in higher SES zip codes. The cost of hospitalization of patients from higher SES quartiles was significantly higher than those from lower quartiles.


This analysis attempts to examine the contemporary role of SES in STEMI outcomes and resource utilization using data from the Nationwide Inpatient Sample (NIS). The findings are not surprising and are consistent with prior work: Patients in poorer zip codes have worse outcomes and use fewer resources. In general, the paper is well-written and the authors provide a new overview of the long literature on disparities in cardiovascular diseases and acute myocardial infarction (AMI). However, the paper does have a few key limitations, which the authors readily acknowledge. The use of administrative data in the NIS limits their ability to detect STEMI (as opposed to AMI), identify timely reperfusion therapy (as opposed to the receipt of any reperfusion therapy), and identify the role of individual SES (as opposed to group SES at the zip code level). These concerns limit the ability to measure the true extent of disparities (because of misclassification), and to understand potential mechanisms by which worse outcomes may be occurring in this group (e.g., individual vs. neighborhood factors). These limitations aside, the continued growth in socioeconomic disparities across the United States makes such work even more important as providers aim to equitably deliver the promise of high-quality cardiovascular care to more patients.

Keywords: Myocardial Infarction, Hospital Mortality, International Classification of Diseases, Income, Residence Characteristics, Hospitalization, Social Class, AHA Annual Scientific Sessions

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