Outcomes and resource utilization in ST-elevation myocardial infarction in the United States: evidence for socioeconomic disparities

Abstract

Background: 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-elevation myocardial infarction (STEMI) undergoing reperfusion. We sought to analyze the impact of SES on in-hospital mortality, timely reperfusion, and cost of hospitalization following STEMI.

Methods and results: We 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 (OR [95% CI]: 1.11 [1.06 to 1.17]). Similarly, there was a highly significant trend indicating a progressively reduced timely reperfusion among patients from lower quartiles (OR [95% CI]: 0.80 [0.74 to 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 [95% CI]: 0.85 [0.75 to 0.97]). Furthermore, the mean adjusted cost of hospitalization among quartiles 2, 3, and 4, as compared to quartile 1 was significantly higher by $913, $2140, and $4070, respectively.

Conclusions: 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.

Keywords: STEMI; acute myocardial infarction; mortality; socioeconomic status; zip code.

Figure 1.

The figure demonstrates the percent incidence and adjusted odds ratio (OR) for in‐hospital mortality, timely reperfusion, use of percutaneous assist devices/intra‐aortic balloon pump (IABP), and Swan Ganz catheterization, stratified by zip‐code‐based socioeconomic quartiles. All quartiles were based on median household income of the respective zip code. All comparisons were drawn with reference to the highest quartile. Quartile 1: $1 to $37 999, quartile 2: $38 000 to $47 999, quartile 3: $48 000 to $62 999, quartile 4: $63 000 or more.

Figure 2.

The percent incidence and adjusted odds ratio (OR) for in‐hospital death and timely reperfusion, stratified by zip‐code‐based socioeconomic quartiles after eliminating all patients who were transferred from an outside healthcare facility. All quartiles were based on median household income of the respective zip code. All comparisons were drawn with reference to the highest quartile. Quartile 1: $1 to $37 999, quartile 2: $38 000 to $47 999, quartile 3: $48 000 to $62 999, quartile 4: $63 000 or more.

Figure 3.

The percent incidence and adjusted odds ratio (OR) for in‐hospital death for various socioeconomic quartiles stratified by the timing of reperfusion therapy. Patients undergoing delayed/no reperfusion are shown in the top panel and those undergoing timely reperfusion are shown in the bottom panel. All comparisons were drawn with reference to the highest quartile. Quartile 1: $1 to $37 999, quartile 2: $38 000 to $47 999, quartile 3: $48 000 to $62 999, quartile 4: $63 000 or more.