THE PRACTICE OF EMERGENCY MEDICINE/BRIEF RESEARCH REPORT

Crowding Does Not Adversely Affect Time to PercutaneousCoronary Intervention for Acute Myocardial Infarction in a

Community Emergency DepartmentBen Harris, MD, Jeonghwan (Christian) Bai, HBSc, Erik B. Kulstad, MD, MS

From the Department of Emergency Medicine, Advocate Christ Medical Center, Oak Lawn, IL (Harris, Bai, Kulstad); and University of Medicine andHealth Sciences, St. Kitts, West Indies (Bai).

Study objective: Multiple studies have linked emergency department (ED) crowding to delays in patient care,such as treatment with antibiotics and analgesics. Multiple studies have also demonstrated the benefit of timelypercutaneous coronary intervention for patients with acute ST-segment elevation myocardial infarction (STEMI).We therefore study whether increased occupancy rates in our community ED might correlate with delays in door-to-balloon time for patients with acute STEMI who are referred for emergency percutaneous coronaryintervention.

Methods: This study was a single-institution prospective observational study. For every patient arriving in our EDfrom June 2007 through October 2009 with acute STEMI treated with percutaneous coronary intervention, wemeasured the ED occupancy rate on arrival and the door-to-balloon time and determined the correlation betweenthese variables in univariate and multivariate analyses controlling for patient characteristics, occupancy rate,times to ECG and catheter laboratory activation, and the availability of the catheterization laboratory team (in-house versus on-call).

Results: During the study period, 210 patients were treated with emergency percutaneous coronary interventionin accordance with the hospital protocol. For these patients, the mean ED occupancy rate at arrival was 127%(range 28% to 214%). The mean time to balloon inflation was 65 minutes (range 25 to 142 minutes). The timeto balloon inflation did not significantly change with increasing occupancy rate in univariate analysis (Spearman’scorrelation �0.02; 95% confidence interval �0.13 to 0.11) or in multivariate analysis, with the only significantvariable being the availability of the catheterization laboratory team in house, which was associated withreduced time to balloon inflation.

Conclusion: Times to achieve emergency percutaneous coronary intervention for acute STEMI do not correlatepositively with crowding as measured by the occupancy rate in our ED. [Ann Emerg Med. 2012;59:13-17.]

Please see page 14 for the Editor’s Capsule Summary of this article.

A podcast for this article is available at www.annemergmed.com.

0196-0644/$-see front matterCopyright © 2011 by the American College of Emergency Physicians.doi:10.1016/j.annemergmed.2011.06.545

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INTRODUCTIONBackground

From 1995 to 2005, annual emergency department (ED) visitsin the United States increased by 20% (from 96.5 million to 115.3million per year), whereas the number of hospital EDs decreased by381, the number of US hospitals decreased by 535, and thenumber of hospital beds decreased by 134,000.1 With EDs beingforced to operate at an increasingly higher percentage of theiroriginally intended capacity, concerns have been raised about thesafety and efficacy of patient care delivery in this environment ofhallway beds and “boarders” (patients already admitted to thehospital but who remain in the ED, awaiting an inpatient bed). In

recent years, investigators have linked ED crowding to delays in R

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asic ED treatment, such as providing analgesia for pain andntibiotics for pneumonia, as well as to an overall increase inatient mortality.1,2 Multiple studies have demonstrated the benefitf timely percutaneous coronary intervention for patients withcute ST-segment elevation myocardial infarction (STEMI).3

tudies of the effect of crowding on ED care for acute myocardialnfarctions have yielded mixed reports, with one multicenter studynding a delay associated with crowding4 and another finding nouch delay.5 An earlier retrospective analysis from our institution,sed as the pilot for this study, suggested a decreased likelihood ofimely treatment for acute STEMI in our ED when crowdingncreased.6 In 2007, an analysis of data from the CRUSADE (Can

apid Risk Stratification of Unstable Angina Patients Suppress

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Adverse Outcomes With Early Implementation of the ACC/AHAGuidelines) trial by Diercks et al7 suggested that prolonged lengthof stay (used as a measure of crowding) resulted in decreasedadherence to recommended guidelines.

ImportanceUnderstanding the associations between crowding and time-

sensitive interventions is important in determining areas mostlikely to benefit from attempts at alleviating crowdedconditions. Moreover, if some facets of ED treatment are lessaffected by crowding, efforts at reducing the influence ofcrowding might be optimized.

Goals of This InvestigationIn the study described here, we measured the effect of

crowding on time to percutaneous coronary intervention forpatients with STEMI. We hypothesized that increasing EDoccupancy rates would correlate positively with increasedtimes to achieving percutaneous coronary intervention.

Editor’s Capsule Summary

What is already known on this topicA large body of literature indicates that emergencydepartment (ED) crowding negatively affects thequality of care.

What question this study addressedIs ED crowding, as measured by the ED occupancyrate, associated with delays in time to percutaneouscoronary intervention in patients with ST-segmentelevation myocardial infarction?

What this study adds to our knowledgeTime to percutaneous coronary intervention wasnot associated with occupancy rate. In multivariateanalysis, only the in-house presence of the catheterlaboratory team was associated with time topercutaneous coronary intervention, shortening theinterval from arrival to balloon inflation from anaverage of 76 minutes to 55 minutes.

How this is relevant to clinical practiceThe study demonstrates that when diagnoses suchas STEMI are highly prioritized and additionalresources and personnel are brought to bear, theeffect of ED crowding can be overcome. However,whether this approach negatively affects otherpatients is unknown.

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14 Annals of Emergency Medicine

ATERIALS AND METHODStudy Design

This study was a single-institution prospective observationaltudy approved by our hospital’s institutional review board.

ettingThe study site is a 50-bed ED located in a suburban tertiary care

eaching hospital. The annual ED census was approximately6,000 patients during the study period. The ED is staffed aroundhe clock with board-certified attending emergency physicians andupervised trainee resident physicians, with 110 hours of total dailytaffing by attending physicians and 110 hours of total daily staffingy resident physicians. The hospital has a large cardiacatheterization program, with multiple simultaneous elective andmergency patients undergoing percutaneous coronary interventiony attending and fellow interventional cardiologists during weekdayusiness hours, but no in-house interventional cardiologist oratheterization laboratory staff during nights and weekends. Theospital has a streamlined “code STEMI” protocol designed toacilitate and expedite the movement of patients believed to havecute STEMI from the ambulatory or ambulance triage areas to theatheterization laboratory. This code STEMI protocol consists ofn alert system that pages a catheterization team of interventionalardiologists and support staff and, if they are already in house,lerts them to defer the next elective case and prepare for anmergency catheterization or, during nights or weekends when theyre not at the hospital, brings them in expeditiously. The ED isesponsible for activating the code STEMI protocol, with thettending physician making the decision to activate based on therrival of a patient meeting criteria for an acute STEMI. Becauseur surrounding emergency medical services system consists ofmbulance services capable of obtaining and transmitting an ECGo our ED, activation of the code STEMI protocol occurred beforeD arrival in a small subset of patients (11 of 210).

election of ParticipantsDuring June 2007 through October 2009, all patients

resenting to the ED with chest pain and an ECG with STEMIesulting in activation of our code STEMI protocol werencluded in the study.

ata Collection and ProcessingThe ED occupancy rate data were obtained from our electronic

harting system PulseCheck (Picis, Wakefield, MA). For eachatient, we recorded the real-time ED occupancy rate (totalumber of patients in the ED, including the waiting room, dividedy 50, the total number of licensed beds) at their arrival and theotal time from their arrival to ECG acquisition, code STEMIctivation, and catheter balloon inflation. We measured theorrelation between these variables with Spearman’s correlation.

A small portion of patients (13 of 210) did not have a catheteralloon inflated because either (1) no blockages were found, (2) soany blockages were found that bypass grafting was

ecommended, or (3) the patient’s clinical condition deteriorated

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during catheterization, and angioplasty was deferred to allow forresuscitation. Because all of these patients underwent groinpuncture in the catheterization laboratory and all had the time ofgroin puncture recorded, we used groin puncture as the endpoint.

We did not include patients who were admitted to the hospitaland subsequently underwent elective cardiac catheterization.However, we did include patients whose initial ECG result in theED did not meet the criteria for emergency percutaneous coronaryintervention but who received a diagnosis of acute STEMI on asubsequent ECG while still in the ED, resulting in ED activation ofthe catheterization laboratory. In some cases in which patients werenot found to have STEMI on their initial ECG result but werefound to have STEMI on a subsequent ECG result obtained, forexample, after admission, catheter laboratory activations occurredoutside of the code STEMI protocol, and these cases were thereforenot captured in our data set. In cases in which the catheterlaboratory activation occurred through the code STEMI protocolaccording to an ECG result obtained some time after patientarrival, the time from acquisition of the STEMI ECG was definedas the starting point.

Outcome MeasuresThe primary outcome measure for this study was the interval

from patient arrival to percutaneous coronary intervention. For197 of our 210 study patients, this endpoint corresponded tocatheter balloon inflation. For the 13 patients who did notundergo balloon inflation, this endpoint corresponded to groinpuncture. We additionally measured the time from patientarrival to the acquisition of the ECG and the time from ECG tothe time of activation of the code STEMI.

Primary Data AnalysisAll data were transcribed into an Excel 2007 spreadsheet

(Microsoft, Redmond, WA). Statistical analyses were performedwith SPSS (version 19.0; SPSS Inc, Chicago, IL). We firstperformed a univariate analysis measuring the correlation betweenoccupancy rate and time to percutaneous coronary intervention,using Spearman’s correlation to accommodate potential violationsof parametric assumptions. We then incorporated these data into amultivariate linear regression analysis of the log-transformed timeto percutaneous coronary intervention as a function of theoccupancy rate while controlling for the time of day and day ofweek. Specifically, we specified weekdays between 6 AM and 6 PM tobe times during which the catheterization team was readily availableand all other times to be those in which the catheterization teamwould have had to come in to the hospital from home. Occupancyrate was recorded as a continuous variable, whereas time of day andday of week were coded as a categorical variable (having one of 2values reflecting whether the catheter laboratory team was presentin the hospital or not). We then performed an additionalmultivariate analysis incorporating patient sex, age, and race asvariables in the model, with age specified as a continuous variable,sex as a dichotomous categorical variable, and race as a categoricalvariable with 3 possible values. Additionally, we performed the

analysis with and without the inclusion of the patients who had a p

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TEMI activation in the field. The sample size attained during ourtudy period provides a power of 80% (��.8) to detect atatistically significant correlation coefficient of 0.25 or greater at an

of .05 (type I error rate of 5%).A post hoc analysis was performed to assess whether the

ffect of crowding was being masked by the fact that theatheterization team was in house and readily available duringaytime hours on weekdays. Patients arriving on Mondayhrough Friday between 6 AM and 6 PM were separated fromhose arriving at off hours to assess the effect of crowding whenontrolling for in house catheter laboratory team availability.

ESULTSDuring the study period, June 2007 through October 2009,

10 patients were treated with emergency percutaneousoronary intervention in accordance with our hospital protocol,ode STEMI. Mean age was 61 years, median age 60 yearsinterquartile range 50 years to 71 years), with 65% men. Theacial distribution of patients was 72% white, 14% black, and4% other (including Hispanic, Arab-American and otheriddle Eastern, and Asian). The mean occupancy rate at arrival

as 127% (range 28% to 214%). The mean time to balloonnflation was 65 minutes (range 25 to 142 minutes). The meanime from patient arrival to acquisition of ECG was 4.4 minutes95% confidence interval [CI] 3.0 to 5.8 minutes), and theean time from ECG to activation of the code STEMI protocolas 5.8 minutes (95% CI 4.7 to 7.0 minutes). The correlationetween occupancy rate and time to balloon inflation was smallut negative (Spearman’s correlation �0.02; 95% CI �0.13 to.11; P�.78) (Figure 1). Removal of the 11 patients who hadhe code STEMI protocol activated before arrival to the hospitalesulted in similar findings for the remaining 199 patientsSpearman’s correlation �0.04; 95% CI �0.17 to 0.08;�.61). The correlation between occupancy rate and time from

igure 1. Time to balloon inflation as a function of EDrowding.

atient arrival to acquisition of ECG likewise was small but

Annals of Emergency Medicine 15

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negative (Spearman’s correlation �0.15; 95% CI �0.30 to�0.003; P�.046), as was the correlation between occupancyrate and time from acquisition of ECG to activation of codeSTEMI protocol (Spearman’s correlation �0.10; 95% CI�0.24 to 0.04; P�.18).

In our post hoc analysis, the mean time to balloon inflationwas found to be significantly shorter for those patients arrivingon Monday through Friday between 6 AM and 6 PM (55 versus76 minutes; P�.001) (Figure 2). Figure 3 shows a scatterplot ofdata based on arrival time (a subanalysis of the data presented inFigure 1) to assess the effect of crowding when controlling forin-house catheter laboratory team availability. Including theoccupancy rate and the time to percutaneous coronary

Figure 2. Histogram of times to balloon inflation forpatients arriving when catheter laboratory team is in housecompared with on call.

Figure 3. Bivariate analyses separating data according toarrival time (a subanalysis of the data presented in Figure1) to assess the effect of crowding when controlling forin-house catheter laboratory team.

intervention, ECG, and code STEMI activation in a multiple h

16 Annals of Emergency Medicine

egression model controlling for the time of day and day of theeek (as markers of the availability of the catheterization team

n house, categorized as either in house or on call), as well asatient-specific demographics (age, sex, and race), we found thatnly the presence of the catheterization team in house wasignificantly associated with time to percutaneous coronaryntervention (standardized � �.56; P�.001; overall model2�0.31). Examining only the patients who failed to receiveercutaneous coronary intervention within 90 minutes, weound 21 patients who fit this criterion. The occupancy rate atrrival of these 21 patients was a mean of 123% and median of22%, with interquartile range of 95% to 148%. Theccupancy rate at arrival of the 189 patients who successfullyeceived percutaneous coronary intervention within 90 minutesas not significantly different, with a mean of 128%, median of28%, and interquartile range of 92% to 160%.

IMITATIONSThis study was limited because it was performed at a single

nstitution, and results from this institution may not bepplicable to other practice settings or environments. Inasmuchs this is a study of ED crowding and treatment processes, it islso limited by the choice of the primary endpoint, namely,alloon inflation, because part of this therapy occurs outside ofhe auspices of the ED. We selected this as our primaryndpoint, however, because it has agreed-on clinical significancend remains a high-profile metric by which hospitals arevaluated. Although we performed a number of post hocnalyses, we did not make specific adjustments for multipleypothesis testing, increasing the likelihood of any significantndings being the result of a type I error. Nevertheless, becausef the small values identified in our correlations, very few of theffects observed can reasonably be explained by crowding.

Because our study was performed prospectively, there existshe possibility that providers altered their behavior because ofnowledge of timing data’s being measured; however, these datare routinely recorded and reported to providers in an ongoinguality improvement effort, so the likelihood of a substantialawthorne effect is low. We used race categorizations entered at

riage, which may not always be accurate.

ISCUSSIONIn this study, we did not find a positive correlation between ED

ccupancy rate and time to percutaneous coronary intervention foratients with STEMI who presented to our ED. This result isomewhat counter to expectations, given the larger context of multipletudies at multiple institutions showing a positive correlation betweenrowding and delays in caring for patients with a variety of conditions,ncluding hip fracture pain, pneumonia, and abdominal pain.1,2

owever, although most of the existing literature on crowding inmergency care reports positive correlations between crowding andultiple adverse outcomes, studies of the effect of crowding on ED

are for acute myocardial infarctions, including the work we report

ere, have found inconsistent clinical effects. A study by Pines et al5

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that measured the effect of ED crowding on treatment for pneumoniaand myocardial infarction found significant negative effects onpneumonia care but no measurable reduction in quality of care formyocardial infarction. Schull et al4 found an association between thepercentage of regional hospitals on bypass and delays to thrombolysisfor patients with acute myocardial infarction, using a different measureof crowding. Fishman et al8 found that myocardial infarction patientswho arrived in the ED concurrently with trauma activation patientshad worse clinical outcomes, but that study did not directly measureED or hospital census. Diercks et al7 found worse adherence torecommended guidelines when patients stayed longer in the ED. Apilot study at our own institution of 17 patients undergoingpercutaneous coronary intervention during a 2-month period suggestedthat patients arriving with STEMI during high-crowding periodsmight be less likely to receive timely catheterization.6 This conclusion,however, is not supported by the much more robust, prospective datawe report here from the same ED in a study designed to follow up thatstudy’s findings.

We attempted to control for reliance on factors external to the EDby performing a post hoc analysis separating those patients presentingwhen the catheterization team was in house and at peak efficiencyversus those presenting at other times. As expected, mean time toballoon inflation was significantly shorter for patients arriving onMonday through Friday between 6 AM and 6 PM (55 versus 76minutes; P�.001). This difference is similar to the 21.3-minutedifference reported in a large cohort study of 33,647 patientsundergoing percutaneous coronary intervention during business hoursversus off hours.9 In our study, controlling for this effect did notuncover any additional significant effect of crowding on time toballoon inflation.

One possible explanation for our finding no delays caused by EDcrowding for these patients might be the high priority given to thisdiagnostic and treatment algorithm in our ED. A patient with chestpain who has not yet had an ECG is the first priority of our EDtechnicians. Similarly, a patient with chest pain and acute STEMIon ECG is the first priority for our ED clinicians. Ourcardiac catheterization laboratory gives patients referred byour code STEMI protocol its highest priority forpercutaneous coronary intervention. This “all-hands-on-deck” approach may be enough to overcome the well-documented and widely described delays in diagnosis andtreatment caused by ED crowding. Nevertheless, theresulting diversion of resources may yet influence and furtherexacerbate the adverse effects that are known to occur in thediagnosis and treatment of other conditions, particularlythose given less priority than percutaneous coronaryintervention.

In conclusion, times to achieve emergency percutaneouscoronary intervention do not correlate positively with crowdingas measured by the occupancy rate in our ED. The intensiveinvolvement of technicians and clinicians in our approach toemergency percutaneous coronary intervention may rendereffects from crowding negligible while having other effects on

unmeasured, but still important, processes.

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The authors acknowledge the Emergency Medicine Foundationor support of the initial development of this project.

upervising editor: Ellen J. Weber, MD

unding and support: By Annals policy, all authors are required toisclose any and all commercial, financial, and other relationships inny way related to the subject of this article as per ICMJE conflict of

nterest guidelines (see www.icmje.org). Emergency Medicineoundation provided support for an earlier study which eventually ledo the current investigation, although no direct support for thisurrent investigation was provided. No conflicts directly related tohis manuscript, or the topic, exist.

uthor contributions: BH and EBK conceived and designed thetudy and drafted the article. BH, JB, and EBK performed databstraction and analysis and provided substantial input to thenal article. EBK takes responsibility for the paper as a whole.

ublication dates: Received for publication November 7,010. Revisions received January 27, 2011; May 11, 2011;nd June 19, 2011. Accepted for publication June 30, 2011.vailable online July 29, 2011.

resented as an abstract at the Society of Academicmergency Medicine annual meeting, June 2010, Phoenix, AZ;nd the Illinois College of Emergency Physicians Academicorum, October 2010, Oak Lawn, IL.

ddress for correspondence: Ben Harris, MD, E-mailbenharris@gmail.com.

EFERENCES. Moskop JC, Sklar DP, Geiderman JM, et al. Emergency department

crowding, part 1—concept, causes, and moral consequences. AnnEmerg Med. 2009;53:605-611.

. Olshaker JS, Rathlev NK. Emergency department overcrowding andambulance diversion: the impact and potential solutions ofextended boarding of admitted patients in the emergencydepartment. J Emerg Med. 2006;30:351-356.

. Rathore SS, Curtis JP, Chen J, et al. Association of door-to-balloon timeand mortality in patients admitted to hospital with ST elevationmyocardial infarction: national cohort study. BMJ. 2009;338:b1807.

. Schull MJ, Vermeulen M, Slaughter G, et al. Emergency departmentcrowding and thrombolysis delays in acute myocardial infarction.Ann Emerg Med. 2004;44:577-585.

. Pines JM, Hollander JE, Localio AR, et al. The association betweenemergency department crowding and hospital performance onantibiotic timing for pneumonia and percutaneous intervention formyocardial infarction. Acad Emerg Med. 2006;13:873-878.

. Kulstad EB, Kelley KM. Overcrowding is associated with delays inpercutaneous coronary intervention for acute myocardial infarction.Int J Emerg Med. 2009;2:149-154.

. Diercks DB, Roe MT, Chen AY, et al. Prolonged emergency departmentstays of non-ST-segment-elevation myocardial infarction patients areassociated with worse adherence to the American College of Cardiology/American Heart Association guidelines for management and increasedadverse events. Ann Emerg Med. 2007;50:489-496.

. Fishman PE, Shofer FS, Robey JL, et al. The impact of trauma activationson the care of emergency department patients with potential acutecoronary syndromes. Ann Emerg Med. 2006;48:347-353.

. Magid DJ, Wang Y, Herrin J, et al. Relationship between time ofday, day of week, timeliness of reperfusion, and in-hospitalmortality for patients with acute ST-segment elevation myocardial

infarction. JAMA. 2005;294:803-812.

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