Urban vs Suburban: Is the Door-to-Balloon Time Affected by Geographic, Socioeconomic, or Racial Differences? A Tale of Two Campuses

Background In 2004, the ACC/AHA released guidelines in the treatment of ST-segment elevation myocardial infarction (STEMI) within a time window from the time a patient physically enters the hospital to the time of percutaneous coronary intervention (PCI). This time window is defined as the door-to-balloon time (DTB) and is recommended to be under 90 minutes to improve patient mortality. To add another layer of complexity, patients with varying socioeconomic status and racial differences experience large disparities in health. Our institution provides care for patients in two locations separated by approximately 30 miles within the Detroit metropolitan area. We aimed this study to investigate any differences between DTB times of our two campuses (urban versus suburban population) as well as any differences in the components that comprise DTB times. Methods We retrospectively collected data on all patients who presented to either Campus 1 or Campus 2 with a STEMI from 2016 to 17. DTB times, demographical, temporal, and anatomical data were collected and analyzed. Our search included 169 patients who met the full inclusion criteria. Results The combined average of the overall DTB time for both campuses was 81 minutes, 15 seconds (95% CI: 78:05, 84:25). The average DTB time in Campus 1 was 78 minutes and 41 seconds (95% CI: 73:05, 84:18) versus 82 minutes and 46 seconds (95% CI: 78:55, 86:38) for Campus 2 (p=0.24). There were no statistically significant differences between either campuses within the separate metrics that comprise DTB times. Conclusions Our study demonstrated that we have been able to provide high-quality care to all of our patients presenting with STEMI at either campus, regardless of socioeconomic differences in the populations they serve. Additionally, each campus has demonstrated DTB well below the nationally recommended guidelines.


Introduction
An acute ST-elevation myocardial infarction (STEMI) is an event in which transmural myocardial ischemia results in myocardial injury or necrosis [1]. e estimated annual incidence of myocardial infarction (MI) in the United States is 550,000 new cases per year and 200,000 recurrent cases per year [2]. Recently, it has been estimated that the incidence rates of STEMI decreased appreciably (121 to 77 per 100,000), whereas those of NSTEMI increased slightly (126 to 132 per 100,000) from 1997 to 2005 [3].
A patient presenting with STEMI represents an acute medical emergency requiring immediate complex care coordination to achieve narrow timeliness guidelines for myocardial reperfusion [4]. In patients presenting with STEMI, primary percutaneous coronary intervention (PCI) is the preferred strategy of reperfusion therapy. In 2004, the ACC/AHA released guidelines in the setting and treatment of STEMI.
is guideline recommended a time window from the time a patient physically enters the hospital to the time of PCI to be under 90 minutes [5,6]. is time window was subsequently termed the "door-to-balloon time" or "DTB." Hospitals and medical institutions have implemented a variety of quality protocols within their own systems [7]. Ongoing efforts are recommended to improve the DTB times, which improves the patient-specific mortality overall. ere have been several studies that demonstrated an inverse correlation between DTB time and risk of mortality [8][9][10][11][12]. Currently, it is estimated that almost 90% of patients presenting to a PCI-capable hospital without a clinical reason for delay have a DTB time ≤90 minutes [13,14].
Our institution provides care for patients in two locations within the Detroit metropolitan area with primary PCI capabilities. ese campuses are separated by approximately 30 miles and strive to deliver world-class excellence and quality care to patients, particularly those presenting with life-threatening events. Overall, both campuses report approximately 125 patients per year presenting with STEMIs. Campus 1 is an older institution but also has more beds and advanced services when compared with Campus 2. However, the main difference between our institution's campuses is in regards to the population they serve. Campus 1 serves patients in an urban population with a median income of about $54,000, while Campus 2 serves a more suburban/ rural population with a median income of $92,000 [15]. Campus 1 is located in a city in which 70.3% of the residents are African American, while Campus 2 reported 8.5% of the residents as African American [15].
We aimed to perform a retrospective study investigating our own DTB times in an effort to improve our protocols and patient outcomes. We wanted to investigate any differences between the two campuses (urban versus suburban population) as well as any differences in the components that comprise DTB times. ese components include Door to ECG, ECG to timing of the page to the interventional cardiologist, time of the page to time the patient was on the table in the cardiac catheterization lab, and time from the patient on the table to deployment of the balloon within the culprit lesion.

Methods
We retrospectively collected data on all patients who presented to either Campus 1 or Campus 2 with a STEMI from 2016 to 17. DTB times, demographical, temporal, and anatomical data were collected and analyzed. All patients with ST elevation from other causes were excluded. Patient charts were systematically read to determine the exact time of chest pain onset, presentation to ED, time of ECG, page to the interventional cardiologist, and DTB times.
Initially, our search included 220 patients between the two campuses, and 169 met the full inclusion criteria. Patients were excluded if the DTB could not be determined, if ECG or page to the cardiologist occurred prior to presentation in hospital, or if the patient was already admitted to the inpatient services of the hospital. Statistical analyses were performed with Microsoft Excel. Continuous data were analyzed using 2 tailed t tests, and categorical data were analyzed using chisquared tests.

Results
Our study collected data about all STEMI cases occurring on both campuses for two calendar years (2016 through 2017).
ere were 169 patients presenting with a clinical scenario and ECG criteria consistent with STEMI that met our inclusion criteria. Campus Table 4). e shortest DTB was 43 minutes, while the longest DTB was 2 hours and 52 minutes (Table 5). e average time from a patient entering the emergency department to receiving an ECG across both campuses was 7 minutes and 50 seconds (95% CI: 6:29, 9:11) ( Table 3). Campus 1 reported an average door-to-ECG time of 8 minutes and 11 seconds (95% CI: 6:20, 10:02), while Campus 2 had an average time of 7 minutes and 39 seconds (95% CI: 5:49, 9:29) (p � 0.68) (Table 4, Figure 2). e shortest time within this door-to-ECG interval was 1 minute, while the longest instance was 1 hour and 9 minutes (Table 5). e average time from a patient receiving an ECG to an outgoing page to an interventional cardiologist was 9 minutes and 51 seconds (95% CI: 7:55, 11:47) (

Discussion
Door-to-balloon (DTB) time is a complex outcome that is potentially affected by many different prognostic factors and   e strongest evidence, supported by the largest number of credible studies, is for activation of the catheterization laboratory using emergency medicine physicians rather than cardiologists, greater use of prehospital ECGs, and use of data monitoring/feedback. e same meta-analysis stated reasonable evidence also exists for establishing a single-call system for activating the catheterization laboratory, setting the expectation that the cardiac catheterization team will be available within 30 minutes after being paged, and having an organizational environment with strong senior management support and team-based culture to foster and sustain organizational changes directed at improving door-to-balloon time [16]. As part of our institution's long-standing protocols, the monthly review of all STEMI cases has been implemented. orough review of all STEMI cases that did not meet the 90 minute DTB time recommendation initiated a root cause analysis (RCA). is RCA breaks down the DTB time into individual components such as door to ECG, ECG to page to physician, time from page to transfer to the cardiac catheterization table, and time from placement on cardiac catheterization table to angioplasty. is multidisciplinary process includes EMS teams, ED physicians, ED   staff, catheterization lab staff, and interventional cardiologists and allows for the opportunity to continue identifying areas for potential quality improvement.
Although there are continuous improvements in medical care and disease prevention, health disparities persist and may be increasing for chronic conditions such as obesity, cardiovascular disease, and cancer [17,18]. Economically disadvantaged racial and ethnic minorities and populations of all races with low socioeconomic status and significant racial disparities experience large disparities in health [19]. Our institution has one campus serving the majority of patients with a lower socioeconomic status compared with the suburban campus. Our study demonstrated we have been able to provide high-quality care to all of our patients presenting with STEMI at either campus, regardless of socioeconomic differences in the populations they serve. Many of these STEMI patients can also experience heart failure as a consequence, and it is always important to consider the psychosocial determinants of health when managing these patients [20].
Even though there was no statistically significant difference in results between the two campuses, we acknowledge a few limitations within our study. First, there is a possibility that our analysis may be underpowered as to the number of patients included. Consequently, there were trends noted in the analysis that were not statistically significant and a larger number of patients may have lead to statistically significant results. Interestingly, the two campuses are staffed by the same groups of emergency physicians and interventional cardiologists although there are different cardiac catheterization lab staff in the two hospitals. Despite this, we noted that the greatest difference between the two campuses, albeit not statistically significant, was in door-to-ECG time which was longer in campus 1, the urban institution. Hence, the intake process at this institution may benefit from further investigation and improvement in workflow to expedite the door-to-ECG time.

Conclusion
e nationally recommended door-to-balloon time <90 minutes remains an important metric that hospitals across the nation strive to achieve and improve upon. We evaluated two different hospitals and despite demographic, socioeconomic, geographical, medical, and hierarchical differences between the 2 hospital campuses and the populations they serve, we found no statistical difference between DTB times. Our institution demonstrated average DTB times for two campuses below the national recommendation of 90 minutes. However, there remain areas of improvement, as several of the most outstanding institutions are now regularly achieving DTB times under 60 minutes [21,22]. We believe this should be our next goal as we move forward in improving our ability to provide the highest quality of care to all of our patients.

Data Availability
Data can be made available upon request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.