Article, Cardiology

Overall ED efficiency is associated with decreased time to percutaneous coronary intervention for ST-segment elevation myocardial infarction

a b s t r a c t

Background: Performance of percutaneous coronary intervention (PCI) within 90 minutes of hospital arrival for ST-segment elevation myocardial infarction patients is a commonly cited clinical quality measure. The Centers for Medicare and Medicaid Services use this measure to adjust hospital reimbursement via the Value- Based Purchasing Program. This study investigated the relationship between hospital performance on this quality measure and emergency department (ED) operational efficiency.

Methods: Hospital-level data from Centers for Medicare and Medicaid Services on PCI quality measure performance was linked to information on operational performance from 272 US EDs obtained from the Emergency Department Benchmarking Alliance annual operations survey. Standard metrics of ED size, acuity, and efficiency were compared across hospitals grouped by performance on the door-to-balloon time quality measure. Results: Mean hospital performance on the 90-minute arrival to PCI measure was 94.0% (range, 42-100). Among hospitals failing to achieve the door-to-balloon time performance standard, median ED length of stay was 209 minutes, compared with 173 minutes among those hospitals meeting the benchmark standard (P b .001). Similarly, median time from ED patient arrival to physician evaluation was 39 minutes for hospitals below the performance standard and 23 minutes for hospitals at the benchmark standard (P b .001). Markers of ED size and acuity, including Annual patient volume, admission rate, and the percentage of patients arriving via ambulance did not vary with door-to-balloon time.

Conclusion: Better performance on measures associated with ED efficiency is associated with more timely PCI performance.

(C) 2014

  1. Introduction

The Hospital Value-Based Purchasing Program is an initiative of the Centers for Medicare and Medicaid Services incentivizing the delivery of high-quality care to Medicare recipients. Through Value-Based Purchasing, CMS adjusts hospital reimbursement ac- cording to performance on quality measures across a broad spectrum of clinical domains. Centers for Medicare and Medicaid Services implemented quality measures related to the care of patients hospitalized for treatment of an acute myocardial infarction in 2003,

? Meetings: This abstract was presented at the American College of Cardiology annual meeting on 3/10/2013 in San Francisco, CA, and the Society for Academic Emergency Medicine annual meeting on 5/17/2013 in Atlanta, GA.

?? Grants/Disclosures: Dr Seema Sonnad is supported through grants from the

University of Pennsylvania Research Foundation (Philadelphia, PA) and from the University of Pennsylvania-Pfizer Collaborative (Philadelphia, PA). She has previously received consulting income from the Center for Medical technology Policy (Baltimore, MD) and a grant from InHealth (Seattle, WA). No other authors have relevant disclosures.

* Corresponding author. Tel.: +1 856 342 2627; fax: +1 856 968 8272.

E-mail address: [email protected] (C.W. Jones).

when the Hospital Inpatient Quality Reporting Program was estab- lished [1]. The percentage of patients with acute ST-elevation myocardial infarction receiving percutaneous coronary intervention (PCI) within 90 minutes of hospital arrival is one of 12 inaugural Value-Based Purchasing measures affecting hospital reim- bursement during CMS fiscal year 2013 [2]. Centers for Medicare and Medicaid Services has indicated that this measure is likely to remain active through at least fiscal year 2016 [3].

Consistent achievement of the 90-minute “door-to-balloon time” benchmark is dependent on close coordination and cooperation across multiple components of a community’s health care system, including prehospital emergency medical services, emergency departments (EDs), and interventional cardiology teams. Because of the importance of Rapid treatment for acute STEMI patients, prior research examining door-to-balloon time metrics has focused on the identification of specific, practical strategies to improve the timeliness of PCI, including prehospital activation of a STEMI protocol, streamlining catheteriza- tion laboratory activation from the ED, and providing team members with real-time performance feedback [4-8]. The impact of overall ED crowding and efficiency on PCI performance, however, has not been

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hospital characteristics“>well described. Emergency department patient volumes and crowding have increased dramatically over the last decade, and these trends are expected to continue for the foreseeable future [9]. It is likely that as ED utilization continues to increase, the delivery of time-sensitive care to acutely ill patients will face increasing challenges due to ED crowding. Our objective was to characterize the relationship between ED efficiency and the performance of timely PCI for STEMI patients.

  1. Methods
    1. Eligibility criteria

Hospitals were eligible for inclusion in this study if they both submitted data on door-to-balloon times to CMS as part of Value- Based Purchasing and completed the Emergency Department Bench- marking Alliance (EDBA) annual operations survey. In order for a hospital to be eligible to participate in Value-Based Purchasing for the door-to-balloon time metric, the facility must have reported data from at least 10 cases to CMS over the course of a year. Because hospitals reporting fewer than 10 cases would not be eligible for financial rewards based on their performance on this measure, these hospitals were excluded from our analysis. We also limited our analysis to hospitals with an annual ED volume of at least 20000 patients, as EDs below this threshold differ from larger facilities with respect to ED crowding and patient acuity [10].

Quality measure performance

Quality measure performance data collected by CMS is publicly available at the hospital level at [11]. Data for fiscal year 2011 was downloaded in Excel spreadsheet format for all hospitals participating in the Value-Based Purchasing program. Data for each facility included both the percentage of STEMI patients receiving PCI within 90 minutes of hospital arrival and the number of cases reported to CMS for the fiscal year.

Centers for Medicare and Medicaid Services uses data gathered during baseline benchmarking periods to define a performance standard and a benchmark standard for each quality measure. The performance standard is equal to the 50th percentile of hospital performance on each measure; the benchmark standard is equal to the average performance of the top decile of hospitals for each measure [12]. Each hospital’s performance relative to these standards is used to calculate a score, which influences that facility’s Value- Based Purchasing incentive payment. The performance standard for the percentage of STEMI patients treated with Primary PCI with a door-to-balloon time of less than 90 minutes is 91.86%; to meet the benchmark standard, 100% of the patients reported to CMS for this measure must meet the 90-minute time cutoff [12]. Hospitals were divided a priori into 3 groups based on PCI performance relative to these standards: those that failed to meet the performance standard, an intermediate group between the performance and benchmark standards, and those hospitals meeting the benchmark standard. Each facility’s unique CMS certification number was used to link CMS data to ED Operational data.

Emergency department variables

Emergency department operational data for calendar year 2011 was obtained from the EDBA, an organization that collects demo- graphic and performance data from a diverse cohort of EDs throughout the United States [13]. Membership in the organization is voluntary and includes both academic and community hospitals. Hospital-level data are collected from ED administrators at partici- pating institutions annually.

Demographic information collected by the EDBA includes ED annual volume, categorization as an academic or community center,

and trauma center status. Measures of ED acuity include the percentage of patients admitted from each facility’s ED, the percent- age of patients arriving to the ED via emergency medical services, and the percentage of patients assigned high-complexity billing codes (Current Procedural Terminology codes 99284, 99285, or 99291). Emergency department crowding and efficiency metrics include the median length of stay within the ED for all patients, median length of stay within the department before transfer to an inpatient bed for admitted patients, percentage of ED patients who chose to leave the ED before being discharged, and the median time between a patient’s arrival in the ED and their evaluation by a physician or midlevel provider [14]. These metrics are not limited to data from STEMI patients but instead describe overall ED performance.


Univariate analyses were performed to determine mean values for standard ED variables across hospitals grouped by PCI performance. We also used linear regression to examine the effect of acuity on the relationship between ED crowding variables and PCI performance. The regression was performed using door-to-balloon time results as our dependent variable. Regression models were constructed for each of the crowding measures by including all four size and acuity measures in each model, along with the crowding measure in question. P values b .05 were considered significant. Statistical significance was assessed using the Kruskal-Wallis test to compare the distributions of ED metrics between hospitals categorized according to door-to-balloon time quality measure results. Statistical analyses were performed with IBM Corp SPSS (Chicago, IL) version 20.0.

  1. Results
    1. Hospital characteristics

PCI performance data were available for 1557 hospitals reporting to CMS during fiscal year 2011. Two hundred forty-two hospitals were excluded because the annual ED volume was below 20000 visits. Emergency department metrics were available for 429 potentially eligible hospitals. The 272 (63%) of these which reported at least 10 PCIs to CMS during the study period formed our study cohort. Hospital and ED characteristics for these facilities appear in Table 1. Of these 272 hospitals, 224 (82%) reported data from every STEMI patient to CMS; the remaining 18% provided data from a random sample of cases. The mean number of cases reported per hospital was 43 (SD, 25; range, 10-168).

Table 1

Hospital characteristics

Hospital characteristics

n = 272

Geographic designation, n (%) Rural

13 (5%)

Large urban

150 (55%)

Other urban

US census region, n (%)

109 (40%)


29 (11%)


110 (40%)


86 (32%)


47 (17%)

Academic center, n (%)

81 (30%)

Bed number, n (%)


78 (29%)


133 (49%)

N 400

61 (22%)

Table 2

Emergency department variables according to door-to-balloon time performance

ED variable


Below performance standard

Between performance and benchmark standardsa

At benchmark standardb


Annual volume (patients)

53793 +- 23219

50201 +- 23427

55434 +- 22761

54441 +- 23627


ED patients with high-complexity billing codes (%)

68 +- 8.8

68 +- 8.2

68 +- 9.5

69 +- 8.4


ED admission rate (%)

21.4 +- 6.1

21.2 +- 6.0

21.2 +- 5.9

21.8 +- 6.9


Arrival by ambulance (%)

19.5 +- 6.3

20.9 +- 7.3

19.3 +- 5.7

18.9 +- 6.2


Median ED LOS (min)

190 +- 62

209 +- 71

192 +- 63

172 +- 47


ED LOS admitted patients (min)

305 +- 91

343 +- 128

303 +- 81

282 +- 64


Left before treatment complete (%)

2.2 +- 1.8

2.7 +- 2.0

2.3 +- 2.0

1.7 +- 1.3


Median time from ED arrival to provider evaluation (min)

28 +- 20

39 +- 29

27 +- 16

23 +- 15


Abbreviation: LOS, length of stay.

Values are mean +- SD.

a The door-to-balloon time performance standard for STEMI patients receiving PCI within 90 minutes of hospital arrival is 91.86%.

b The benchmark standard is 100%.

Main results

Mean hospital performance on the 90-minute arrival to PCI measure was 94.0% (95% confidence interval, 93.0-94.9; range, 42-100). Sixty-nine hospitals (25%) performed below the perfor- mance standard of 91.86%, 117 hospitals (43%) performed between the performance standard and the benchmark standard of 100%, and 86 hospitals (32%) performed at the benchmark standard.

Table 2 displays mean values for measures of ED volume, acuity, efficiency, and crowding among hospitals grouped by PCI perfor- mance. No significant differences were observed across these groups for measures of ED volume and acuity (Fig. 1). A clinically and statistically significant pattern of decreased ED crowding and improved efficiency existed among hospitals with better PCI perfor- mance (Fig. 2). This pattern was consistent across all measures of crowding and efficiency, including mean ED length of stay for all patients (P b .001), mean ED length of stay for admitted patients (P = .01), the percentage of patients who left before treatment was completed (P = .002), and the median delay between ED arrival and evaluation by a medical provider (P b .001). These relationships remained significant when adjusted for any of the acuity measures studied.

  1. Discussion

This study demonstrates a correlation between ED crowding and efficiency and delayed door-to-balloon times for patients with STEMI. The 90-minute door-to-balloon time measure has received substantial attention as a benchmark for the quality of clinical care provided to these patients, reflecting improved clinical outcomes among STEMI patients who receive rapid reperfusion [15-17]. Now that CMS has included door-to-balloon time as a quality measure in the Value- Based Purchasing program, hospitals throughout the United States face financial incentives from CMS to consistently meet the 90-minute benchmark. Previous work has identified multiple interventions shown to reduce door-to-balloon times, including prehospital initiation of a STEMI protocol, activating catheterization laboratory staff and alerting the on-call cardiologist with a single call or page from the ED, and providing Real-time feedback to staff in the ED and catheterization laboratory [6,8,18,19]. Other studies have identified significant associations between fixed variables and door-to-balloon times, including time of day of arrival to the ED, female sex, and race [17,20-23]. To date, the relationship between door-to-balloon time and institutional crowding has received less attention, although the present study shows that ED crowding and inefficiency are associated with delayed care for STEMI patients.

It is likely that a portion of the delay in PCI associated with

decreased ED efficiency occurs because patients in crowded EDs

spend more time waiting for both an initial triage evaluation and for an initial Electrocardiogram . Furthermore, even after STEMI patients are identified, care is sometimes delayed by other critically ill patients who require attention from ED physicians and nurses. Several prior analyses have demonstrated evidence of this effect among other ED patient populations, by documenting delays in patient care during peak times of ED crowding [24,25]. However, the specific impact of this effect on patients with STEMI is unknown. A recent single-center study failed to show an effect on door-to-balloon times for STEMI patients presenting during periods of ED crowding as determined by ED occupancy rate [26]. This may be because the recognition of an STEMI patient generally triggers the rapid mobilization of hospital- wide resources to expedite care.

The presence of institutional factors, which are causally related to both STEMI care and ED efficiency may also explain why this single-center study failed to show an effect between crowding and door-to-balloon times, in contrast to our observed results [27]. ST-segment elevation myocardial infarction care may be less affected by occasional periods of crowding within a particular institution than by characteristics of a given hospital, which make it function less efficiently overall than its peers. As processes surrounding the identification of STEMI patients, activation of STEMI protocols, and PCI performance are optimized, further improve- ments in time-related STEMI metrics increasingly may depend on the identification and management of these institutional considerations.


Several important limitations should be considered when interpret- ing these results. First, these data are based on a nonrandom hospital sample. It is likely that ED administrators who choose to participate in the EDBA have a particular interest in ED operational performance; data from these EDs therefore may not be generalizable to other facilities. Second, door-to-balloon times in this group of hospitals were tightly clustered, with 75% of hospitals exceeding the door-to-balloon time performance standard of 91.86%. This suggests that the patterns we report on are of limited clinical significance to individual patients. However, our results suggest that ED efficiency may affect overall institutional door-to-balloon performance as assessed by CMS. Further- more, these observed patterns are likely to impact hospital reimburse- ment, as Value-Based Purchasing is fully implemented.

It is also important to consider the distinction between the total population of STEMI patients who receive emergent cardiac cathe- terization and the patients included in the CMS door-to-balloon measure when interpreting our results. Each reporting institution within this data set was responsible for applying numerous exclusion criteria to their patients to generate the door-to-balloon time data submitted to CMS. Consequently, these data represent quality

Fig. 1. Box and whisker plots showing measures of ED volume and acuity among hospitals categorized according to door-to-balloon time performance. The line inside each box represents the median, shaded boxes display the interquartile range (25th-75th percentile), and whiskers encompass minimum and maximum values up to 1.5 times the interquartile range. Outliers are represented by circles.

measure performance, which may differ in some instances from actual overall Clinical performance.

Another limitation is that this analysis demonstrates a correlation between PCI performance and ED crowding and efficiency; it does not prove the existence of a causal relationship. In particular, our data set does not allow for the consideration of several potentially confounding factors, including prehospital electrocardiogram (EKG) transmission, catheteri- zation laboratory activation protocols, and in-house catheterization laboratory staff. Given these limitations, further study is needed to better characterize the nature of the observed relationships. Finally, because of

the nature of the CMS and EDBA data sets, we compared CMS data from fiscal year 2011 (October 2010 to September 2011) with EDBA data from January 2011 to December 2011.

  1. Conclusions

The ability of a hospital to consistently perform PCI for patients with STEMI within 90 minutes of hospital arrival is related to multiple measures of ED crowding and efficiency. Hospitals with more efficient EDs consistently report better performance on this quality measure.

Fig. 2. Box and whisker plots showing measures of ED crowding and efficiency among hospitals categorized according to door-to-balloon time performance. The line inside each box represents the median, shaded boxes display the interquartile range (25th-75th percentile), and whiskers encompass minimum and maximum values up to 1.5 times the interquartile range. Outliers are represented by circles.

No relationship was demonstrated between PCI performance and measures of ED volume or acuity. Further study is needed to isolate the specific causal factors impacting the relationship between PCI performance and ED crowding.


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