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Use of emergency medical services expedites in-hospital care processes in patients presenting with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention
Use of Emergency Medical Services Expedites In-hospital Care Processes in Patients Presenting with ST-segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention Joshua P. Loh, Lowell F. Satler, Lakshmana K. Pendyala, Sa’ar Minha, William J. Frohna, Rebecca Torguson, Fang Chen, William O. Suddath, Augusto D. Pichard, Ron Waksman PII: DOI: Reference:
S1553-8389(14)00099-2 doi: 10.1016/j.carrev.2014.03.011 CARREV 644
To appear in:
Cardiovascular Revascularization Medicine
Received date: Accepted date:
19 March 2014 20 March 2014
Please cite this article as: Loh Joshua P., Satler Lowell F., Pendyala Lakshmana K., Minha Sa’ar, Frohna William J., Torguson Rebecca, Chen Fang, Suddath William O., Pichard Augusto D., Waksman Ron, Use of Emergency Medical Services Expedites Inhospital Care Processes in Patients Presenting with ST-segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention, Cardiovascular Revascularization Medicine (2014), doi: 10.1016/j.carrev.2014.03.011
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Use of Emergency Medical Services Expedites In-hospital Care Processes in
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Patients Presenting with ST-segment Elevation Myocardial Infarction
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Undergoing Primary Percutaneous Coronary Intervention
Joshua P. Loh, MBBS; Lowell F. Satler, MD; Lakshmana K. Pendyala, MD;
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Sa‟ar Minha, MD; William J. Frohna, MD*; Rebecca Torguson, MPH;
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Fang Chen, PhD; William O. Suddath, MD; Augusto D. Pichard, MD; Ron Waksman, MD
Interventional Cardiology, MedStar Washington Hospital Center, Washington, DC
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*Department of Emergency Medicine, MedStar Washington Hospital Center, Washington, DC
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Brief title: EMS- versus Self-Transport in STEMI
Correspondence to:
Ron Waksman, MD MedStar Washington Hospital Center 110 Irving Street, NW, Suite 4B-1 Washington, DC20010 Tel: 202-877-2812 Fax: 202-877-2715 Email: [email protected]
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ABSTRACT
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Objective: To determine whether door-to-balloon (DTB) times of patients presenting with ST-
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elevation myocardial infarction (STEMI) were reduced in patients transported by emergency medical services (EMS) compared to those who were self-transported.
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Background: DTB time is an important measure of hospital care processes in STEMI. Use of EMS may expedite in-hospital processing and reduce DTB times.
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Methods: A total of 309 consecutive STEMI patients who underwent primary percutaneous
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coronary intervention in our institution were analyzed. Excluded were patients who received fibrinolytics, presented in cardiac arrest, were intubated, or were transferred from another
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hospital. EMS-transported patients (n=83) were compared to self-transported patients (n=226). The primary outcome measure was DTB time and its component time intervals. Secondary end
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points included symptom-to-door and symptom-to-balloon times, and correlates for DTB >90
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minutes.
Results: A higher percentage of EMS-transported patients reached the time goal of DTB <90
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minutes compared to self-transported patients (83.1 versus 54.3%; p <0.001). EMS-transported patients had shorter DTB times [median (IQR) minutes, 65 (50-86) versus 85 (61-126); p <0.001] due to a reduction of emergency department processing (door-to-call) time, whereas catheterization laboratory processing (call-to-balloon) times were similar in both groups. EMStransported patients had shorter symptom-to-door [median (IQR) hours, 1.2 (0.8-3.5) versus 2.3 (1.2-7.5); p <0.001] and symptom-to-balloon [median (IQR) hours, 2.5 (1.9 -4.7) versus 4.3 (2.69.1); p <0.001]. Independent correlates of DTB times >90 minutes were self-transport (odds ratio 5.32, 95% CI 2.65-10.70; p<0.001) and off-hours presentation (odds ratio 2.89, 95% CI 1.605.22; p<0.001).
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Conclusion: Use of EMS transport in STEMI patients significantly shortens time to reperfusion,
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primarily by expediting emergency department processes. Community education efforts should
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focus not only on the importance of recognizing symptoms of myocardial infarction, but also
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taking early action by calling the EMS.
Key words: Door-to-balloon time; ST-segment elevation myocardial infarction; Emergency
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medical services
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INTRODUCTION
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Rapid reperfusion with percutaneous coronary intervention (PCI) is the gold standard
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therapy for patients presenting with ST-segment elevation myocardial infarction (STEMI) when promptly available.1 Delays in door-to-balloon (DTB) times correlate with increased morbidity
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and mortality.2,3 Achieving a DTB time of <90 minutes has become a quality measure of the hospital system performance dealing with STEMI care.1,4 With the identification of key
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strategies to enhance hospital system performances,5,6 several programs have been successfully
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implemented to help meet the DTB <90-minute time goals with timely access to primary PCI.7-9 To address the continuum of care for STEMI patients from the onset of symptoms to
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arrival at the emergency department (ED), the use of emergency medical services (EMS) may potentially facilitate rapid transport, early assessment and treatment, and expedited
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communication of information with the accepting ED. However, EMS has been shown to be
own transportation.
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underutilized,10,11 and a significant proportion of STEMI patients still arrive at the ED via their
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MedStar Washington Hospital Center (Washington, DC) is a primary PCI facility with around-the-clock cardiac catheterization capabilities catering to Washington, DC, a highly urbanized area with EMS coverage provided fully by the DC Fire and EMS. In addition, it serves as a referring PCI center for other facilities in DC, as well as parts of Maryland and Virginia. MedStar Washington Hospital Center is located in the heart of Washington, DC, and with DC Fire and EMS as the single EMS provider for Washington, DC, this offers us a unique opportunity to analyze modes of transport for STEMI patients within DC, and its impact on preand in-hospital care processes leading to reperfusion. Specifically, we aimed to determine if the
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use of EMS transport may actually reduce overall DTB times by reducing certain components of
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in-hospital processing times.
METHODS
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Patient population
This retrospective analysis included all patients from January 2007 to December 2012
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who presented to the MedStar Washington Hospital Center ED with a STEMI and subsequently
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underwent primary PCI. Patients who were transferred from a referring institution, patients who suffered cardiac arrest, patients who were intubated, and patients who were given fibrinolytic
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therapy before the PCI were excluded. The patients were categorized into whether they were self-transported (“self”) or transported by EMS.
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DC Fire and EMS
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DC Fire and EMS provides EMS coverage to Washington, DC, an urban city of 68.3 square miles, through 58 medical units (or ambulances) and is managed by a centralized 911
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dispatch call system. The ambulances have 12-lead electrocardiogram (ECG) capabilities that are transmissible to the receiving ED at MedStar Washington Hospital Center. All patients are transported to the ED where a formal ECG is performed. Based on the qualifying criteria for STEMI, the ED physician contacts the on-call interventionalist. When activation of the catheterization laboratory is considered appropriate, the on-call interventionalist contacts a central number to mobilize the catheterization laboratory team, and the patient is transferred to the catheterization laboratory. Because the system does not allow for pre-activation of the catheterization laboratory team from the ambulance, none of the patients bypassed the ED enroute to the catheterization laboratory.
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Self-transport
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The term „self-transport‟ refers to patients who arrive at the ED using transportation that
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did not involve EMS. These modes of transportation include public transportation, taxi, selfdriven or driven by others, or walked to the hospital. These patients may have also visited
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another healthcare facility after symptom onset, before arriving at the ED by non-EMS transport. They also go through the usual triaging process in the ED. Following a diagnosis of STEMI on
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ECG, the interventionalist and the catheterization laboratory team are mobilized in the usual
Study definitions and end points
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manner.
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The following time points were defined and collected contemporaneously for each STEMI patient (Figure 1): Symptom onset time (from patient recall); Door time (time of first
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registered hospital contact); ECG time (time of inciting STEMI ECG leading to decision to
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activate the catheterization laboratory); Call time (time of call to interventionalist); Lab time (time of patient arrival to the cardiac catheterization laboratory); Case start time (time of first
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sheath insertion); and Balloon time [time of introduction of first device (balloon catheter, aspiration thrombectomy catheter or stent) restoring antegrade flow]. Time intervals were then calculated from these time points. Door-to-call is to be taken as ED processing time interval, and call-to-balloon is to be taken as laboratory processing time interval. Off-hours presentation was defined as any weekend presentation or weekday presentation from 5 pm to 8 am. ECG criteria defining a STEMI included the presence of at least 1 mm STsegment elevation in at least 2 contiguous leads, or the occurrence of a new left bundle branch block. Angiographic success was defined as a residual stenosis of <30% with Thrombolysis In Myocardial Infarction grade III flow.
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The primary end point was DTB time. Secondary end points were the DTB component
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times, symptom-door and symptom-balloon times. In-hospital outcomes evaluated were death,
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cardiac death, Q-wave MI, urgent coronary artery bypass graft surgery, and urgent repeat PCI of target lesion.
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Interventional treatment
PCI was performed according to guidelines current at the time of the procedure. All
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patients received an aspirin loading dose of 325 mg, as well as either clopidogrel (600 mg),
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prasugrel (60 mg) or ticagrelor (180 mg) loading. Anticoagulation regimens were chosen at the operator‟s discretion and included unfractionated heparin adjusted to targeted activated clotting
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time, or bivalirudin 0.75 mg/kg followed by an infusion of 1.75 mg/kg/hr for the duration of the procedure. The interventional strategy, utilization of adjunct pharmacotherapy, such as
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glycoprotein IIb/IIIa inhibitors, and device choice were at the operator‟s discretion. Dual
Data collection
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antiplatelet therapy was recommended for ≥12 months for all patients post procedure.
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Clinical, procedural, and follow-up data were prospectively collected and stored in a central database. A dedicated data coordinating center performed all data management and analyses. Pre-specified clinical and procedural data and in-hospital complications were obtained from hospital charts reviewed by independent research personnel blinded to the study objectives. Primary source documents were obtained for all events and were used to adjudicate STEMI cases by physicians not involved in the procedures, and who were unaware of the study objectives. The time points and time intervals pertaining to STEMI management and system performance were adjudicated and verified by physicians not involved in the study. The institutional review boards
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at MedStar Washington Hospital Center (Washington, DC) and the MedStar Health Research
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Institute (Washington, DC) approved this study.
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Statistical analysis
Statistical analysis was performed using SAS version 9.1 (SAS Institute Inc, Cary, NC).
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Continuous variables are presented as mean ± standard deviation (SD) if normally distributed, or median ± interquartile range (IQR) if non-normally distributed. Student‟s t test and Wilcoxon
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rank-sum test were used for comparisons of normally and non-normally distributed continuous
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data, respectively. Categorical variables are expressed as frequencies and percentage, and compared using chi-square test or Fisher‟s exact test as appropriate. A multivariate logistic
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regression model was used to determine the independent correlates of DTB >90 minutes, expressed as odds ratio, with 95% confidence interval. Variables were selected on the basis of
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overall clinical relevance, with particular attention given to clinical and procedural factors that
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may delay time to reperfusion. Variables included self-transport (versus EMS), off-hours presentation (versus on hours), age, female gender, body mass index, diabetes, peripheral
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vascular disease, prior PCI, prior coronary artery bypass grafting, placement of intra-aortic balloon pump, and American College of Cardiology/American Heart Association type C lesion. A p value <0.05 is considered statistically significant.
RESULTS A total of 309 consecutive STEMI patients who underwent primary PCI were analyzed, of which 226 arrived by self-transport, and 83 were transported by EMS. The baseline and procedural characteristics in both groups were similar. (Tables I and II). The majority of patients from both groups presented to the ED during off hours. A significantly higher percentage of
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EMS-transported patients achieved the time goals of DTB <90 minutes and DTB <120 minutes
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compared to self-transported patients. (Figure 2) Median DTB times were 20 minutes shorter if
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patients arrived by EMS compared to self-transport (65 versus 85 minutes; p <0.001). (Figure 3) Comparisons of individual components of DTB (median, IQR) are shown in Figure 4.
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Door-to-ECG and ECG-to-call intervals were significantly shorter in EMS-transported patients, whereas call-to-lab, lab-to-case start, and case start-to-balloon intervals were similar in both
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groups. The overall ED processing interval (door-to-call) was shorter in EMS-transported
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patients, but the cath lab processing interval (call-to-balloon) was similar compared to selftransported patients. (Figure 3) Compared with EMS-transported patients, self-transported
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patients took longer to arrive at the ED from symptom onset (symptom-to-door, 2.3 versus 1.2 hours, p <0.001), and had a significantly delayed symptom-to-balloon time (4.3 versus 2.5 hours,
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p <0.001). (Figure 5)
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In-hospital clinical outcomes were similar in both groups, although there was a nonstatistical reduction of mortality in the EMS-transported group. (Table III) On multivariate
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analysis, (Table IV) self-transport compared with EMS-transport correlated significantly with a DTB >90 minutes (odds ratio 5.30, 95% confidence interval 2.56-11.00, p <0.001). (Table IV) Presentation during off hours was also found to correlate independently with DTB >90 minutes (odds ratio 3.09, 95% confidence interval 1.63-5.87, p=0.001). We did not find any significant interaction between self-transport and off-hours presentation. None of the other variables included in the multivariate model correlated with DTB >90 minutes.
DISCUSSION
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With continued emphasis on shortening the symptom-to-treatment time in patients
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presenting with acute myocardial infarction, the present study detects important findings that
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may impact this mission: 1) Compared to self-transport, EMS transport leads to faster in-hospital ED processing time, translating to reduction in DTB time in STEMI patients undergoing primary
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PCI; 2) EMS-transported patients experienced shorter delays to hospital care from symptom onset; and 3) Self-transport and off hours presentation predicts delayed DTB times.
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The use of EMS has been recommended as a vital component in STEMI care.6 The
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findings from our study were consistent with those from the National Cardiovascular Data Registry,11 demonstrating that EMS transport in STEMI care reduces not only symptom-to-door
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times, but also DTB times. Our study was distinct in that we were able to collect data dividing DTB times into component times. This enables us to tease out the impact of EMS transport on
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specific time intervals, and hence evaluate the in-hospital systems processes leading to eventual
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reperfusion. Moreover, as one of three primary PCI centers within an urbanized area covered by a single EMS provider, it allowed us to evaluate the impact of different transport modes on
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system processes with greater consistency. Our study demonstrates that compared to self-transport, EMS-transported STEMI patients were more likely to achieve timely reperfusion (DTB <90 minutes) due to a reduction in ED processing intervals (door-to-ECG and ECG-to-call). This is perhaps related to the ability of the DC Fire and EMS ambulances to perform a pre-hospital 12-lead ECG, transmit the ECG to the receiving ED, and the ability to communicate in advance to the receiving ED. All suspected STEMI patients transported by EMS arrive at the ED for assessment, and if the STEMI criteria are met without exclusions, the interventionalist is contacted directly by the ED physician, thus initiating the process of the catheterization lab activation. In our hospital system, none of the
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patients bypass the ED to the catheterization laboratory. The merit of the EMS is perhaps in
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expediting the ED triage and assessment processes, thereby significantly shortening the door-to-
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call time. In contrast, self-transported patients must undergo the usual triaging process in the ED, thus delaying the door-to-ECG interval. Moreover, without advanced insight into the acuity of
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the patient‟s problem, the diagnosis of STEMI and subsequent action (ECG-to-call) are also delayed. However, once the catheterization laboratory is activated, the processing intervals were
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no different in EMS- versus self-transported patients. Thus, with regard to in-hospital care
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processes, catheterization laboratory processing intervals were found to be consistent, whereas differing ED processing intervals led to overall differences in DTB times between the two
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groups. This is consistent with findings from the Activate-SF Registry,12 which demonstrated that door-to-call time is a strong driver of overall door-to-balloon time. In fact, the door-to-call
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time (median, 11.5 minutes, IQR 7-20) for EMS-transported patients in our study was well
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within the 20-minute time interval proposed in that study predicting DTB <90 minutes. From our study, the impact of EMS transport on STEMI patients receiving hospital care
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is an almost two-fold reduction in symptom-to-door time compared to self-transported patients (median, 1.2 vs. 2.3 hours, respectively). In all of our EMS-transported patients, aspirin therapy was administered by EMS. In this regard, activating EMS would certainly shorten the time of symptom onset to first medical contact and anti-ischemic treatment. A delay in hospital arrival in self-transported patients also translates into a longer symptom-to-balloon time; and a prolonged total ischemic time is known to be associated with worse outcomes in STEMI patients.13 Moreover, delaying hospital arrival in STEMI may result in patients falling out of the 12-hour symptom-to-reperfusion therapeutic window for maximum benefit. The reasons for a longer symptom-to-door time in self- compared to EMS-transported patients are not entirely clear and
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are multi-factorial. Perhaps one of the possible explanations attests to the efficiency of the EMS
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provider. In 2012, the DC Fire and EMS had an average response time of 7 minutes, 28 seconds,
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for the first-to-arrive ambulance to critical medical calls; and the percent of critical medical calls to receive an ambulance within 12 minutes has consistently been >90%.14 In other systems,
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however, EMS transport to hospital may not always be quicker than self-transport.15 Moreover, other patient-related factors, such as atypical symptoms, diabetes, race, gender, as well as
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psychosocial factors, have been shown to impact pre-hospital delays.16-21
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Among the known factors associated with delays in DTB, our study found that selftransport (versus EMS-transport) and off-hours presentation (versus on-hours) correlate
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independently with DTB >90 minutes. The impact of off-hours presentation causing delay was also demonstrated in recent studies.22,23 However, other known patient-related factors did not
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correlate with delays in DTB in our study.24-26
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Our study identifies a practical approach to help expedite in-hospital processing of STEMI patients – use of EMS will actually facilitate more efficient ED processes leading to
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catheterization laboratory activation. The availability of pre-hospital ECGs may have helped in the ED triage process leading to catheterization laboratory activation,27 and door-to-activation time is a key determinant of DTB times.12 At present, EMS is still underutilized based on large national registries,11 and for reasons unclear, this has not changed since a decade back,10 although the median DTB times have improved due to improvements in hospital best practice strategies.28 Increasing the use of EMS would certainly provide further opportunities to improve DTB times in most systems similar to ours. Other strategies may include pre-hospital activation of the catheterization laboratory and bypassing the ED altogether for patients with a clear STEMI diagnosis.29 This approach has its pitfalls, however, the least of which include erroneous
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diagnosis, incomplete assessment of patient‟s condition, and false activations.30-32 In addition, many systems in the United States do not practice pre-hospital activation. In line with Mission:
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Lifeline, a nationwide initiative for STEMI care launched by the American Heart Association,33 community education efforts should be directed not only at recognizing symptoms of myocardial
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infarction, but also at the exigency and benefit of EMS activation. The key message to the community is to call EMS early in order to avoid delays. Moreover, efforts should be made to
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identify major barriers to EMS use (e.g. denial, lack of awareness, fear of costs, trustworthiness
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of others to provide care, as well as other psychosocial and educational factors),19-21 to enhance the effectiveness of community outreach.
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This study has several limitations. This was a retrospective, observational study, which reflects the process of care from a single institution and one EMS provider in Washington, DC;
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these data may not be representative in other settings. We excluded certain subgroups of patients
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(cardiac arrest, intubation, fibrinolytic therapy before PCI) to best reflect the system processes of care, which inevitably creates selection bias. We do not have specific information on the types of
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symptoms that prompted the patient to activate EMS or to self-drive, nor did we have the specific reasoning behind each patient‟s decision regarding the mode of transport. We could not control for the DC Fire and EMS‟s jurisdiction to send patients to our institution, one of three primary PCI facilities in Washington, DC; this decision is based on transport timeliness, patient preference or geographic proximity. We were not able to stratify patients based on distance between infarct symptom occurrence and the hospital. Because of the small study population, this study is not powered to evaluate clinical outcomes. Clinical follow-up was limited to inhospital, however our main objective was to compare the process of care. While our study demonstrates a clear relationship between EMS use and shorter DTB times, there is wide
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variability in the time segments analyzed, suggesting that the process of care for STEMI patients
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still has room for improvement.
CONCLUSION
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The use of EMS transport in STEMI patients significantly shortens time to reperfusion by primary PCI, mainly by expediting emergency department processes. Robust EMS programs
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should be supported with community education outreach efforts that focus not only on the
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importance of recognizing symptoms of myocardial infarction, but also on taking early decisive
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action by calling EMS.
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24. Nikolsky E, Mehran R, Yu J, Witzenbichler B, Brodie BR, Kornowski R, Brener S, Xu K,
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Dangas GD, Stone GW. Comparison of Outcomes of Patients With ST-Segment Elevation
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Myocardial Infarction With Versus Without Previous Coronary Artery Bypass Grafting (from the Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction
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[HORIZONS-AMI] Trial). Am J Cardiol 2013;111:1377-1386.
25. Dreyer RP, Beltrame JF, Tavella R, Air T, Hoffmann B, Pati PK, Di Fiore D, Arstall M, Zeitz C. Evaluation of Gender Differences in Door-to-Balloon Time in ST-Elevation Myocardial Infarction. Heart Lung Circ 2013;22:861-869.
26. Swaminathan RV, Wang TY, Kaltenbach LA, Kim LK, Minutello RM, Bergman G, Wong SC, Feldman DN. Nonsystem Reasons for Delay in Door-to-Balloon Time and Associated InHospital Mortality: A Report From the National Cardiovascular Data Registry. J Am Coll Cardiol 2013;61:1688-1695.
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27. Diercks DB, Kontos MC, Chen AY, Pollack CV Jr, Wiviott SD, Rumsfeld JS, Magid DJ,
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Gibler WB, Cannon CP, Peterson ED, Roe MT. Utilization and impact of pre-hospital
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electrocardiograms for patients with acute ST-segment elevation myocardial infarction: data from the NCDR (National Cardiovascular Data Registry) ACTION (Acute Coronary Treatment
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and Intervention Outcomes Network) Registry. J Am Coll Cardiol 2009;53:161-166.
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28. Krumholz HM, Herrin J, Miller LE, Drye EE, Ling SM, Han LF, Rapp MT, Bradley EH, Nallamothu BK, Nsa W, Bratzler DW, Curtis JP. Improvements in door-to-balloon time in the
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United States, 2005 to 2010. Circulation 2011;124:1038-1045.
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29. Cone DC, Lee CH, Van Gelder C. EMS Activation of the Cardiac Catheterization Laboratory Is Associated with Process Improvements in the Care of Myocardial Infarction Patients. Prehosp
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Emerg Care 2013;17:293-298.
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30. Mencl F, Wilber S, Frey J, Zalewski J, Maiers JF, Bhalla MC. Paramedic ability to recognize
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ST-segment elevation myocardial infarction on prehospital electrocardiograms. Prehosp Emerg Care 2013;17:203-210.
31. Bhalla MC, Mencl F, Gist MA, Wilber S, Zalewski J. Prehospital electrocardiographic computer identification of ST-segment elevation myocardial infarction. Prehosp Emerg Care 2013;17:211-216.
32. Potter BJ, Matteau A, Mansour S, Essiambre R, Montigny M, Savoie S, Gobeil F. Performance of a New "Physician-Less" Automated System of Prehospital ST-Segment
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Elevation Myocardial Infarction Diagnosis and Catheterization Laboratory Activation. Am J
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Cardiol 2013;112:156-161.
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33. Mission: Lifeline. Available at:
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http://www.heart.org/HEARTORG/HealthcareResearch/MissionLifelineHomePage/Mission-
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Lifeline-Home-Page_UCM_305495_SubHomePage.jsp. Accessed January 20, 2014
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FIGURE LEGEND
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Figure 1. Time intervals and time points.
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DTB, door-to-balloon; ECG, electrocardiogram; ED, emergency department; EMS, emergency medical services
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Figure 2. Patients who reached reperfusion time goals. The percentage of STEMI patients who
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reached time goals for reperfusion of door-to-balloon <90 minutes and door-to-balloon <120 minutes.
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STEMI, ST-elevation myocardial infarction; DTB, door-to-balloon
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Figure 3. Emergency department processing, cath lab processing, and overall door-to-balloon times. Comparisons of collective time intervals, divided into emergency department processing
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and cath lab processing intervals, as well as overall door-to-balloon time intervals between self-
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and EMS-transported patients (median, interquartile range).
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Figure 4. Door-to-balloon component times. Comparisons were made between self- and EMStransported patients (median, interquartile range), of distinct component intervals of door-toballoon time divided as follows: door-to-ECG, ECG-to-call, call-to-lab, lab-to-case-start, and case-start-to-balloon. EMS, emergency medical services; ECG, electrocardiogram
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Figure 5. Symptom-to-door and symptom-to-balloon times. Comparisons of symptom-to-door
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and symptom-to-balloon time intervals between self- and EMS-transported patients (median,
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interquartile range).
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Table I Baseline characteristics
153 (67.7%)
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EMS (n=83) 58.7 ± 14.1
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Age (years ± SD)
Self (n=226) 60.9 ± 12.1
0.18
54 (65.1%)
0.66
47 (20.8%)
12 (14.5%)
0.21
African American
154 (68.1%)
61 (73.5%)
0.37
12 (5.3%)
4 (4.8%)
1.00
4 (1.8%)
5 (6.0%)
0.06
28.5 ± 5.9
29.0 ± 6.3
0.56
184 (81.8%)
65 (78.3%)
0.49
77 (34.2%)
23 (27.7%)
0.28
166 (73.5%)
52 (62.5%)
0.07
97 (42.9%)
46 (55.4%)
0.05
Family history of coronary artery disease
92 (41.8%)
21 (25.3%)
0.008
Previous myocardial infarction
36 (16.0%)
15 (18.1%)
0.66
Previous percutaneous coronary intervention
37 (17.1%)
9 (10.8%)
0.18
Previous bypass graft surgery
15 (6.7%)
2 (2.4%)
0.17
Previous congestive heart failure
20 (8.9%)
12 (14.6%)
0.15
Chronic renal insufficiency**
26 (11.6%)
11 (13.3%)
0.69
Peripheral vascular disease
18 (8.0%)
3 (3.6%)
0.18
Cardiogenic shock
27 (12.0%)
6 (7.2%)
0.23
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European American
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Ethnicity
p Value
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Hispanic Asian
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Body mass index (kg/m2) Systemic hypertension*
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Diabetes mellitus Hyperlipidemia
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Current smoker
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10 (4.5%)
4 (4.9%)
1.00
40 ± 15
40 ± 18
0.94
Left ventricular ejection fraction (%)
145 (64.2%)
60 (72.3%)
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Off-hours presentation
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Congestive heart failure (Killip III/IV)
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* History of systemic hypertension diagnosed and/or treated with medication or currently being treated with diet and/or medication by a physician. ** Previously diagnosed or treated with medication, diet or dialysis by a physician. Diagnosis at admission if a baseline creatinine of >2.0 mg/dl is found.
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Table II Angiographic and procedural characteristics EMS Patients (n=83) Lesions (n=107) 1.3 ± 0.7
p Value
2 (0.7%)
3 (2.8%)
0.12
134 (44.5%)
45 (42.1%)
0.66
43 (14.3%)
12 (11.2%)
0.42
117 (38.9%)
46 (43.0%)
0.46
4 (1.3%)
1 (0.9%)
1.00
10 (3.3%)
0
0.07
151 (51.2%)
49 (45.8%)
0.34
54 (23.9%)
15 (17.9%)
0.26
177 (78.3%)
73 (88.0%)
0.06
37 (16.4%)
8 (9.6%)
0.14
Glycoprotein IIb/IIIa inhibitor
43 (19.0%)
20 (24.4%)
0.30
Bare metal stent
185 (61.9%)
70 (65.4%)
0.52
Drug-eluting stent
68 (22.6%)
17 (15.9%)
0.14
Angiographic success
294 (98.0%)
106 (99.1%)
0.68
Procedure length (min)
54.0 ± 58.8
61.4 ± 32.0
0.17
174 ± 76
173 ± 79
0.92
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Number of lesions treated
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Target vessel Left main
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Left anterior descending Circumflex
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Right Saphenous vein graft
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Lesion characteristics
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Procedure characteristics
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In-stent restenosis ACC/AHA type C
Heparin
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Contrast amount (ml)
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Self Patients (n=226) Lesions (n=301) 1.3 ± 0.6
0.70
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Table III In-hospital clinical outcomes
Cardiac death
13 (5.7%)
3 (3.6%)
0.57
Q-wave myocardial infarction
3 (1.3%)
0
0.57
Urgent coronary bypass surgery
10 (4.4%)
5 (6.0%)
0.56
Urgent target lesion percutaneous intervention
6 (2.7%)
2 (2.4%)
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EMS (n=83) 3 (3.6%)
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Death
Self (n=226) 14 (6.2%)
p Value 0.58
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Table IV Multivariate logistic regression analysis for variables associated with door-to-balloon
5.30
Presentation during off-hours (versus on-
3.09
p Value
2.56-11.00
<0.001
1.63-5.87
0.001
1.58
0.86-2.91
0.14
1.10
0.88-1.39
0.40
0.90
0.57-1.43
0.66
1.89
0.64-5.62
0.25
1.20
0.66-2.19
0.56
1.85
0.71-4.77
0.21
1.61
0.41-6.22
0.49
Previous percutaneous coronary intervention
1.01
0.46-2.18
0.99
ACC/AHA Type C lesion
0.98
0.56-1.71
0.95
Intra-aortic balloon pump
0.79
0.40-1.57
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Self-transport (versus EMS-transport)
95% confidence interval
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Odds ratio
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time >90 minutes
hours)
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Female gender
Body mass index (10 kg/m2 increment)
Diabetes mellitus
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Previous congestive heart failure
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Peripheral vascular disease
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Age (10-year increment)
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Previous coronary bypass surgery
ACC/AHA, American College of Cardiology/American Heart Association; EMS, emergency medical services
S1553-8389(14)00099-2 doi: 10.1016/j.carrev.2014.03.011 CARREV 644
To appear in:
Cardiovascular Revascularization Medicine
Received date: Accepted date:
19 March 2014 20 March 2014
Please cite this article as: Loh Joshua P., Satler Lowell F., Pendyala Lakshmana K., Minha Sa’ar, Frohna William J., Torguson Rebecca, Chen Fang, Suddath William O., Pichard Augusto D., Waksman Ron, Use of Emergency Medical Services Expedites Inhospital Care Processes in Patients Presenting with ST-segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention, Cardiovascular Revascularization Medicine (2014), doi: 10.1016/j.carrev.2014.03.011
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Use of Emergency Medical Services Expedites In-hospital Care Processes in
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Patients Presenting with ST-segment Elevation Myocardial Infarction
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Undergoing Primary Percutaneous Coronary Intervention
Joshua P. Loh, MBBS; Lowell F. Satler, MD; Lakshmana K. Pendyala, MD;
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Sa‟ar Minha, MD; William J. Frohna, MD*; Rebecca Torguson, MPH;
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Fang Chen, PhD; William O. Suddath, MD; Augusto D. Pichard, MD; Ron Waksman, MD
Interventional Cardiology, MedStar Washington Hospital Center, Washington, DC
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*Department of Emergency Medicine, MedStar Washington Hospital Center, Washington, DC
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Brief title: EMS- versus Self-Transport in STEMI
Correspondence to:
Ron Waksman, MD MedStar Washington Hospital Center 110 Irving Street, NW, Suite 4B-1 Washington, DC20010 Tel: 202-877-2812 Fax: 202-877-2715 Email: [email protected]
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ABSTRACT
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Objective: To determine whether door-to-balloon (DTB) times of patients presenting with ST-
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elevation myocardial infarction (STEMI) were reduced in patients transported by emergency medical services (EMS) compared to those who were self-transported.
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Background: DTB time is an important measure of hospital care processes in STEMI. Use of EMS may expedite in-hospital processing and reduce DTB times.
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Methods: A total of 309 consecutive STEMI patients who underwent primary percutaneous
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coronary intervention in our institution were analyzed. Excluded were patients who received fibrinolytics, presented in cardiac arrest, were intubated, or were transferred from another
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hospital. EMS-transported patients (n=83) were compared to self-transported patients (n=226). The primary outcome measure was DTB time and its component time intervals. Secondary end
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points included symptom-to-door and symptom-to-balloon times, and correlates for DTB >90
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minutes.
Results: A higher percentage of EMS-transported patients reached the time goal of DTB <90
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minutes compared to self-transported patients (83.1 versus 54.3%; p <0.001). EMS-transported patients had shorter DTB times [median (IQR) minutes, 65 (50-86) versus 85 (61-126); p <0.001] due to a reduction of emergency department processing (door-to-call) time, whereas catheterization laboratory processing (call-to-balloon) times were similar in both groups. EMStransported patients had shorter symptom-to-door [median (IQR) hours, 1.2 (0.8-3.5) versus 2.3 (1.2-7.5); p <0.001] and symptom-to-balloon [median (IQR) hours, 2.5 (1.9 -4.7) versus 4.3 (2.69.1); p <0.001]. Independent correlates of DTB times >90 minutes were self-transport (odds ratio 5.32, 95% CI 2.65-10.70; p<0.001) and off-hours presentation (odds ratio 2.89, 95% CI 1.605.22; p<0.001).
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Conclusion: Use of EMS transport in STEMI patients significantly shortens time to reperfusion,
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primarily by expediting emergency department processes. Community education efforts should
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focus not only on the importance of recognizing symptoms of myocardial infarction, but also
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taking early action by calling the EMS.
Key words: Door-to-balloon time; ST-segment elevation myocardial infarction; Emergency
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INTRODUCTION
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Rapid reperfusion with percutaneous coronary intervention (PCI) is the gold standard
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therapy for patients presenting with ST-segment elevation myocardial infarction (STEMI) when promptly available.1 Delays in door-to-balloon (DTB) times correlate with increased morbidity
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and mortality.2,3 Achieving a DTB time of <90 minutes has become a quality measure of the hospital system performance dealing with STEMI care.1,4 With the identification of key
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strategies to enhance hospital system performances,5,6 several programs have been successfully
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implemented to help meet the DTB <90-minute time goals with timely access to primary PCI.7-9 To address the continuum of care for STEMI patients from the onset of symptoms to
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arrival at the emergency department (ED), the use of emergency medical services (EMS) may potentially facilitate rapid transport, early assessment and treatment, and expedited
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communication of information with the accepting ED. However, EMS has been shown to be
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underutilized,10,11 and a significant proportion of STEMI patients still arrive at the ED via their
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MedStar Washington Hospital Center (Washington, DC) is a primary PCI facility with around-the-clock cardiac catheterization capabilities catering to Washington, DC, a highly urbanized area with EMS coverage provided fully by the DC Fire and EMS. In addition, it serves as a referring PCI center for other facilities in DC, as well as parts of Maryland and Virginia. MedStar Washington Hospital Center is located in the heart of Washington, DC, and with DC Fire and EMS as the single EMS provider for Washington, DC, this offers us a unique opportunity to analyze modes of transport for STEMI patients within DC, and its impact on preand in-hospital care processes leading to reperfusion. Specifically, we aimed to determine if the
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use of EMS transport may actually reduce overall DTB times by reducing certain components of
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in-hospital processing times.
METHODS
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Patient population
This retrospective analysis included all patients from January 2007 to December 2012
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who presented to the MedStar Washington Hospital Center ED with a STEMI and subsequently
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underwent primary PCI. Patients who were transferred from a referring institution, patients who suffered cardiac arrest, patients who were intubated, and patients who were given fibrinolytic
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therapy before the PCI were excluded. The patients were categorized into whether they were self-transported (“self”) or transported by EMS.
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DC Fire and EMS
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DC Fire and EMS provides EMS coverage to Washington, DC, an urban city of 68.3 square miles, through 58 medical units (or ambulances) and is managed by a centralized 911
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dispatch call system. The ambulances have 12-lead electrocardiogram (ECG) capabilities that are transmissible to the receiving ED at MedStar Washington Hospital Center. All patients are transported to the ED where a formal ECG is performed. Based on the qualifying criteria for STEMI, the ED physician contacts the on-call interventionalist. When activation of the catheterization laboratory is considered appropriate, the on-call interventionalist contacts a central number to mobilize the catheterization laboratory team, and the patient is transferred to the catheterization laboratory. Because the system does not allow for pre-activation of the catheterization laboratory team from the ambulance, none of the patients bypassed the ED enroute to the catheterization laboratory.
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Self-transport
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The term „self-transport‟ refers to patients who arrive at the ED using transportation that
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did not involve EMS. These modes of transportation include public transportation, taxi, selfdriven or driven by others, or walked to the hospital. These patients may have also visited
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another healthcare facility after symptom onset, before arriving at the ED by non-EMS transport. They also go through the usual triaging process in the ED. Following a diagnosis of STEMI on
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ECG, the interventionalist and the catheterization laboratory team are mobilized in the usual
Study definitions and end points
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manner.
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The following time points were defined and collected contemporaneously for each STEMI patient (Figure 1): Symptom onset time (from patient recall); Door time (time of first
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registered hospital contact); ECG time (time of inciting STEMI ECG leading to decision to
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activate the catheterization laboratory); Call time (time of call to interventionalist); Lab time (time of patient arrival to the cardiac catheterization laboratory); Case start time (time of first
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sheath insertion); and Balloon time [time of introduction of first device (balloon catheter, aspiration thrombectomy catheter or stent) restoring antegrade flow]. Time intervals were then calculated from these time points. Door-to-call is to be taken as ED processing time interval, and call-to-balloon is to be taken as laboratory processing time interval. Off-hours presentation was defined as any weekend presentation or weekday presentation from 5 pm to 8 am. ECG criteria defining a STEMI included the presence of at least 1 mm STsegment elevation in at least 2 contiguous leads, or the occurrence of a new left bundle branch block. Angiographic success was defined as a residual stenosis of <30% with Thrombolysis In Myocardial Infarction grade III flow.
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The primary end point was DTB time. Secondary end points were the DTB component
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times, symptom-door and symptom-balloon times. In-hospital outcomes evaluated were death,
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cardiac death, Q-wave MI, urgent coronary artery bypass graft surgery, and urgent repeat PCI of target lesion.
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Interventional treatment
PCI was performed according to guidelines current at the time of the procedure. All
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patients received an aspirin loading dose of 325 mg, as well as either clopidogrel (600 mg),
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prasugrel (60 mg) or ticagrelor (180 mg) loading. Anticoagulation regimens were chosen at the operator‟s discretion and included unfractionated heparin adjusted to targeted activated clotting
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time, or bivalirudin 0.75 mg/kg followed by an infusion of 1.75 mg/kg/hr for the duration of the procedure. The interventional strategy, utilization of adjunct pharmacotherapy, such as
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glycoprotein IIb/IIIa inhibitors, and device choice were at the operator‟s discretion. Dual
Data collection
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antiplatelet therapy was recommended for ≥12 months for all patients post procedure.
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Clinical, procedural, and follow-up data were prospectively collected and stored in a central database. A dedicated data coordinating center performed all data management and analyses. Pre-specified clinical and procedural data and in-hospital complications were obtained from hospital charts reviewed by independent research personnel blinded to the study objectives. Primary source documents were obtained for all events and were used to adjudicate STEMI cases by physicians not involved in the procedures, and who were unaware of the study objectives. The time points and time intervals pertaining to STEMI management and system performance were adjudicated and verified by physicians not involved in the study. The institutional review boards
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at MedStar Washington Hospital Center (Washington, DC) and the MedStar Health Research
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Institute (Washington, DC) approved this study.
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Statistical analysis
Statistical analysis was performed using SAS version 9.1 (SAS Institute Inc, Cary, NC).
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Continuous variables are presented as mean ± standard deviation (SD) if normally distributed, or median ± interquartile range (IQR) if non-normally distributed. Student‟s t test and Wilcoxon
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rank-sum test were used for comparisons of normally and non-normally distributed continuous
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data, respectively. Categorical variables are expressed as frequencies and percentage, and compared using chi-square test or Fisher‟s exact test as appropriate. A multivariate logistic
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regression model was used to determine the independent correlates of DTB >90 minutes, expressed as odds ratio, with 95% confidence interval. Variables were selected on the basis of
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overall clinical relevance, with particular attention given to clinical and procedural factors that
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may delay time to reperfusion. Variables included self-transport (versus EMS), off-hours presentation (versus on hours), age, female gender, body mass index, diabetes, peripheral
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vascular disease, prior PCI, prior coronary artery bypass grafting, placement of intra-aortic balloon pump, and American College of Cardiology/American Heart Association type C lesion. A p value <0.05 is considered statistically significant.
RESULTS A total of 309 consecutive STEMI patients who underwent primary PCI were analyzed, of which 226 arrived by self-transport, and 83 were transported by EMS. The baseline and procedural characteristics in both groups were similar. (Tables I and II). The majority of patients from both groups presented to the ED during off hours. A significantly higher percentage of
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EMS-transported patients achieved the time goals of DTB <90 minutes and DTB <120 minutes
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compared to self-transported patients. (Figure 2) Median DTB times were 20 minutes shorter if
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patients arrived by EMS compared to self-transport (65 versus 85 minutes; p <0.001). (Figure 3) Comparisons of individual components of DTB (median, IQR) are shown in Figure 4.
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Door-to-ECG and ECG-to-call intervals were significantly shorter in EMS-transported patients, whereas call-to-lab, lab-to-case start, and case start-to-balloon intervals were similar in both
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groups. The overall ED processing interval (door-to-call) was shorter in EMS-transported
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patients, but the cath lab processing interval (call-to-balloon) was similar compared to selftransported patients. (Figure 3) Compared with EMS-transported patients, self-transported
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patients took longer to arrive at the ED from symptom onset (symptom-to-door, 2.3 versus 1.2 hours, p <0.001), and had a significantly delayed symptom-to-balloon time (4.3 versus 2.5 hours,
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p <0.001). (Figure 5)
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In-hospital clinical outcomes were similar in both groups, although there was a nonstatistical reduction of mortality in the EMS-transported group. (Table III) On multivariate
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analysis, (Table IV) self-transport compared with EMS-transport correlated significantly with a DTB >90 minutes (odds ratio 5.30, 95% confidence interval 2.56-11.00, p <0.001). (Table IV) Presentation during off hours was also found to correlate independently with DTB >90 minutes (odds ratio 3.09, 95% confidence interval 1.63-5.87, p=0.001). We did not find any significant interaction between self-transport and off-hours presentation. None of the other variables included in the multivariate model correlated with DTB >90 minutes.
DISCUSSION
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With continued emphasis on shortening the symptom-to-treatment time in patients
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presenting with acute myocardial infarction, the present study detects important findings that
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may impact this mission: 1) Compared to self-transport, EMS transport leads to faster in-hospital ED processing time, translating to reduction in DTB time in STEMI patients undergoing primary
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PCI; 2) EMS-transported patients experienced shorter delays to hospital care from symptom onset; and 3) Self-transport and off hours presentation predicts delayed DTB times.
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The use of EMS has been recommended as a vital component in STEMI care.6 The
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findings from our study were consistent with those from the National Cardiovascular Data Registry,11 demonstrating that EMS transport in STEMI care reduces not only symptom-to-door
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times, but also DTB times. Our study was distinct in that we were able to collect data dividing DTB times into component times. This enables us to tease out the impact of EMS transport on
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specific time intervals, and hence evaluate the in-hospital systems processes leading to eventual
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reperfusion. Moreover, as one of three primary PCI centers within an urbanized area covered by a single EMS provider, it allowed us to evaluate the impact of different transport modes on
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system processes with greater consistency. Our study demonstrates that compared to self-transport, EMS-transported STEMI patients were more likely to achieve timely reperfusion (DTB <90 minutes) due to a reduction in ED processing intervals (door-to-ECG and ECG-to-call). This is perhaps related to the ability of the DC Fire and EMS ambulances to perform a pre-hospital 12-lead ECG, transmit the ECG to the receiving ED, and the ability to communicate in advance to the receiving ED. All suspected STEMI patients transported by EMS arrive at the ED for assessment, and if the STEMI criteria are met without exclusions, the interventionalist is contacted directly by the ED physician, thus initiating the process of the catheterization lab activation. In our hospital system, none of the
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patients bypass the ED to the catheterization laboratory. The merit of the EMS is perhaps in
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expediting the ED triage and assessment processes, thereby significantly shortening the door-to-
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call time. In contrast, self-transported patients must undergo the usual triaging process in the ED, thus delaying the door-to-ECG interval. Moreover, without advanced insight into the acuity of
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the patient‟s problem, the diagnosis of STEMI and subsequent action (ECG-to-call) are also delayed. However, once the catheterization laboratory is activated, the processing intervals were
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no different in EMS- versus self-transported patients. Thus, with regard to in-hospital care
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processes, catheterization laboratory processing intervals were found to be consistent, whereas differing ED processing intervals led to overall differences in DTB times between the two
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groups. This is consistent with findings from the Activate-SF Registry,12 which demonstrated that door-to-call time is a strong driver of overall door-to-balloon time. In fact, the door-to-call
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time (median, 11.5 minutes, IQR 7-20) for EMS-transported patients in our study was well
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within the 20-minute time interval proposed in that study predicting DTB <90 minutes. From our study, the impact of EMS transport on STEMI patients receiving hospital care
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is an almost two-fold reduction in symptom-to-door time compared to self-transported patients (median, 1.2 vs. 2.3 hours, respectively). In all of our EMS-transported patients, aspirin therapy was administered by EMS. In this regard, activating EMS would certainly shorten the time of symptom onset to first medical contact and anti-ischemic treatment. A delay in hospital arrival in self-transported patients also translates into a longer symptom-to-balloon time; and a prolonged total ischemic time is known to be associated with worse outcomes in STEMI patients.13 Moreover, delaying hospital arrival in STEMI may result in patients falling out of the 12-hour symptom-to-reperfusion therapeutic window for maximum benefit. The reasons for a longer symptom-to-door time in self- compared to EMS-transported patients are not entirely clear and
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are multi-factorial. Perhaps one of the possible explanations attests to the efficiency of the EMS
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provider. In 2012, the DC Fire and EMS had an average response time of 7 minutes, 28 seconds,
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for the first-to-arrive ambulance to critical medical calls; and the percent of critical medical calls to receive an ambulance within 12 minutes has consistently been >90%.14 In other systems,
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however, EMS transport to hospital may not always be quicker than self-transport.15 Moreover, other patient-related factors, such as atypical symptoms, diabetes, race, gender, as well as
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psychosocial factors, have been shown to impact pre-hospital delays.16-21
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Among the known factors associated with delays in DTB, our study found that selftransport (versus EMS-transport) and off-hours presentation (versus on-hours) correlate
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independently with DTB >90 minutes. The impact of off-hours presentation causing delay was also demonstrated in recent studies.22,23 However, other known patient-related factors did not
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correlate with delays in DTB in our study.24-26
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Our study identifies a practical approach to help expedite in-hospital processing of STEMI patients – use of EMS will actually facilitate more efficient ED processes leading to
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catheterization laboratory activation. The availability of pre-hospital ECGs may have helped in the ED triage process leading to catheterization laboratory activation,27 and door-to-activation time is a key determinant of DTB times.12 At present, EMS is still underutilized based on large national registries,11 and for reasons unclear, this has not changed since a decade back,10 although the median DTB times have improved due to improvements in hospital best practice strategies.28 Increasing the use of EMS would certainly provide further opportunities to improve DTB times in most systems similar to ours. Other strategies may include pre-hospital activation of the catheterization laboratory and bypassing the ED altogether for patients with a clear STEMI diagnosis.29 This approach has its pitfalls, however, the least of which include erroneous
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diagnosis, incomplete assessment of patient‟s condition, and false activations.30-32 In addition, many systems in the United States do not practice pre-hospital activation. In line with Mission:
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Lifeline, a nationwide initiative for STEMI care launched by the American Heart Association,33 community education efforts should be directed not only at recognizing symptoms of myocardial
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infarction, but also at the exigency and benefit of EMS activation. The key message to the community is to call EMS early in order to avoid delays. Moreover, efforts should be made to
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identify major barriers to EMS use (e.g. denial, lack of awareness, fear of costs, trustworthiness
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of others to provide care, as well as other psychosocial and educational factors),19-21 to enhance the effectiveness of community outreach.
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This study has several limitations. This was a retrospective, observational study, which reflects the process of care from a single institution and one EMS provider in Washington, DC;
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these data may not be representative in other settings. We excluded certain subgroups of patients
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(cardiac arrest, intubation, fibrinolytic therapy before PCI) to best reflect the system processes of care, which inevitably creates selection bias. We do not have specific information on the types of
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symptoms that prompted the patient to activate EMS or to self-drive, nor did we have the specific reasoning behind each patient‟s decision regarding the mode of transport. We could not control for the DC Fire and EMS‟s jurisdiction to send patients to our institution, one of three primary PCI facilities in Washington, DC; this decision is based on transport timeliness, patient preference or geographic proximity. We were not able to stratify patients based on distance between infarct symptom occurrence and the hospital. Because of the small study population, this study is not powered to evaluate clinical outcomes. Clinical follow-up was limited to inhospital, however our main objective was to compare the process of care. While our study demonstrates a clear relationship between EMS use and shorter DTB times, there is wide
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variability in the time segments analyzed, suggesting that the process of care for STEMI patients
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still has room for improvement.
CONCLUSION
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The use of EMS transport in STEMI patients significantly shortens time to reperfusion by primary PCI, mainly by expediting emergency department processes. Robust EMS programs
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should be supported with community education outreach efforts that focus not only on the
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importance of recognizing symptoms of myocardial infarction, but also on taking early decisive
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action by calling EMS.
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Fang JC, Fesmire FM, Franklin BA, Granger CB, Krumholz HM, Linderbaum JA, Morrow DA,
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16. McGinn AP, Rosamond WD, Goff DC Jr, Taylor HA, Miles JS, Chambless L. Trends in
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17. Ting HH, Bradley EH, Wang Y, Lichtman JH, Nallamothu BK, Sullivan MD, Gersh BJ, Roger VL, Curtis JP, Krumholz HM. Factors associated with longer time from symptom onset to
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19. Mensah GA, Hand MM, Antman EM, Ryan TJ Jr, Schriever R, Smith SC Jr. Development of
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20. Sullivan MD, Ciechanowski PS, Russo JE, Soine LA, Jordan-Keith K, Ting HH, Caldwell JH. Understanding why patients delay seeking care for acute coronary syndromes. Circ Cardiovasc Qual Outcomes 2009;2:148-154.
21. Perkins-Porras L, Whitehead DL, Strike PC, Steptoe A. Causal beliefs, cardiac denial and pre-hospital delays following the onset of acute coronary syndromes. J Behav Med 2008;31:498505.
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22. Cubeddu RJ, Palacios IF, Blankenship JC, Horvath SA, Xu K, Kovacic JC, Dangas GD,
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Witzenbichler B, Guagliumi G, Kornowski R, Dudek D, Stone GW, Mehran R. Outcome of
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23. Khare RK, Nannicelli AP, Powell ES, Seivert NP, Adams JG, Holl JL. Use of Risk
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Ann Emerg Med 2013;62:388-398.e12.
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Assessment Analysis by Failure Mode, Effects, and Criticality to Reduce Door-to-Balloon Time.
24. Nikolsky E, Mehran R, Yu J, Witzenbichler B, Brodie BR, Kornowski R, Brener S, Xu K,
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Dangas GD, Stone GW. Comparison of Outcomes of Patients With ST-Segment Elevation
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Myocardial Infarction With Versus Without Previous Coronary Artery Bypass Grafting (from the Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction
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25. Dreyer RP, Beltrame JF, Tavella R, Air T, Hoffmann B, Pati PK, Di Fiore D, Arstall M, Zeitz C. Evaluation of Gender Differences in Door-to-Balloon Time in ST-Elevation Myocardial Infarction. Heart Lung Circ 2013;22:861-869.
26. Swaminathan RV, Wang TY, Kaltenbach LA, Kim LK, Minutello RM, Bergman G, Wong SC, Feldman DN. Nonsystem Reasons for Delay in Door-to-Balloon Time and Associated InHospital Mortality: A Report From the National Cardiovascular Data Registry. J Am Coll Cardiol 2013;61:1688-1695.
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27. Diercks DB, Kontos MC, Chen AY, Pollack CV Jr, Wiviott SD, Rumsfeld JS, Magid DJ,
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Gibler WB, Cannon CP, Peterson ED, Roe MT. Utilization and impact of pre-hospital
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electrocardiograms for patients with acute ST-segment elevation myocardial infarction: data from the NCDR (National Cardiovascular Data Registry) ACTION (Acute Coronary Treatment
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and Intervention Outcomes Network) Registry. J Am Coll Cardiol 2009;53:161-166.
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28. Krumholz HM, Herrin J, Miller LE, Drye EE, Ling SM, Han LF, Rapp MT, Bradley EH, Nallamothu BK, Nsa W, Bratzler DW, Curtis JP. Improvements in door-to-balloon time in the
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United States, 2005 to 2010. Circulation 2011;124:1038-1045.
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29. Cone DC, Lee CH, Van Gelder C. EMS Activation of the Cardiac Catheterization Laboratory Is Associated with Process Improvements in the Care of Myocardial Infarction Patients. Prehosp
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Emerg Care 2013;17:293-298.
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30. Mencl F, Wilber S, Frey J, Zalewski J, Maiers JF, Bhalla MC. Paramedic ability to recognize
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ST-segment elevation myocardial infarction on prehospital electrocardiograms. Prehosp Emerg Care 2013;17:203-210.
31. Bhalla MC, Mencl F, Gist MA, Wilber S, Zalewski J. Prehospital electrocardiographic computer identification of ST-segment elevation myocardial infarction. Prehosp Emerg Care 2013;17:211-216.
32. Potter BJ, Matteau A, Mansour S, Essiambre R, Montigny M, Savoie S, Gobeil F. Performance of a New "Physician-Less" Automated System of Prehospital ST-Segment
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Elevation Myocardial Infarction Diagnosis and Catheterization Laboratory Activation. Am J
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Cardiol 2013;112:156-161.
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33. Mission: Lifeline. Available at:
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http://www.heart.org/HEARTORG/HealthcareResearch/MissionLifelineHomePage/Mission-
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Lifeline-Home-Page_UCM_305495_SubHomePage.jsp. Accessed January 20, 2014
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FIGURE LEGEND
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Figure 1. Time intervals and time points.
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DTB, door-to-balloon; ECG, electrocardiogram; ED, emergency department; EMS, emergency medical services
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Figure 2. Patients who reached reperfusion time goals. The percentage of STEMI patients who
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reached time goals for reperfusion of door-to-balloon <90 minutes and door-to-balloon <120 minutes.
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STEMI, ST-elevation myocardial infarction; DTB, door-to-balloon
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Figure 3. Emergency department processing, cath lab processing, and overall door-to-balloon times. Comparisons of collective time intervals, divided into emergency department processing
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and cath lab processing intervals, as well as overall door-to-balloon time intervals between self-
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and EMS-transported patients (median, interquartile range).
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Figure 4. Door-to-balloon component times. Comparisons were made between self- and EMStransported patients (median, interquartile range), of distinct component intervals of door-toballoon time divided as follows: door-to-ECG, ECG-to-call, call-to-lab, lab-to-case-start, and case-start-to-balloon. EMS, emergency medical services; ECG, electrocardiogram
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Figure 5. Symptom-to-door and symptom-to-balloon times. Comparisons of symptom-to-door
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and symptom-to-balloon time intervals between self- and EMS-transported patients (median,
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interquartile range).
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Table I Baseline characteristics
153 (67.7%)
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Men
EMS (n=83) 58.7 ± 14.1
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Age (years ± SD)
Self (n=226) 60.9 ± 12.1
0.18
54 (65.1%)
0.66
47 (20.8%)
12 (14.5%)
0.21
African American
154 (68.1%)
61 (73.5%)
0.37
12 (5.3%)
4 (4.8%)
1.00
4 (1.8%)
5 (6.0%)
0.06
28.5 ± 5.9
29.0 ± 6.3
0.56
184 (81.8%)
65 (78.3%)
0.49
77 (34.2%)
23 (27.7%)
0.28
166 (73.5%)
52 (62.5%)
0.07
97 (42.9%)
46 (55.4%)
0.05
Family history of coronary artery disease
92 (41.8%)
21 (25.3%)
0.008
Previous myocardial infarction
36 (16.0%)
15 (18.1%)
0.66
Previous percutaneous coronary intervention
37 (17.1%)
9 (10.8%)
0.18
Previous bypass graft surgery
15 (6.7%)
2 (2.4%)
0.17
Previous congestive heart failure
20 (8.9%)
12 (14.6%)
0.15
Chronic renal insufficiency**
26 (11.6%)
11 (13.3%)
0.69
Peripheral vascular disease
18 (8.0%)
3 (3.6%)
0.18
Cardiogenic shock
27 (12.0%)
6 (7.2%)
0.23
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European American
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Ethnicity
p Value
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Hispanic Asian
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Body mass index (kg/m2) Systemic hypertension*
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Diabetes mellitus Hyperlipidemia
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Current smoker
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10 (4.5%)
4 (4.9%)
1.00
40 ± 15
40 ± 18
0.94
Left ventricular ejection fraction (%)
145 (64.2%)
60 (72.3%)
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Off-hours presentation
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Congestive heart failure (Killip III/IV)
0.18
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* History of systemic hypertension diagnosed and/or treated with medication or currently being treated with diet and/or medication by a physician. ** Previously diagnosed or treated with medication, diet or dialysis by a physician. Diagnosis at admission if a baseline creatinine of >2.0 mg/dl is found.
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Table II Angiographic and procedural characteristics EMS Patients (n=83) Lesions (n=107) 1.3 ± 0.7
p Value
2 (0.7%)
3 (2.8%)
0.12
134 (44.5%)
45 (42.1%)
0.66
43 (14.3%)
12 (11.2%)
0.42
117 (38.9%)
46 (43.0%)
0.46
4 (1.3%)
1 (0.9%)
1.00
10 (3.3%)
0
0.07
151 (51.2%)
49 (45.8%)
0.34
54 (23.9%)
15 (17.9%)
0.26
177 (78.3%)
73 (88.0%)
0.06
37 (16.4%)
8 (9.6%)
0.14
Glycoprotein IIb/IIIa inhibitor
43 (19.0%)
20 (24.4%)
0.30
Bare metal stent
185 (61.9%)
70 (65.4%)
0.52
Drug-eluting stent
68 (22.6%)
17 (15.9%)
0.14
Angiographic success
294 (98.0%)
106 (99.1%)
0.68
Procedure length (min)
54.0 ± 58.8
61.4 ± 32.0
0.17
174 ± 76
173 ± 79
0.92
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Number of lesions treated
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Target vessel Left main
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Left anterior descending Circumflex
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Right Saphenous vein graft
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Lesion characteristics
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Procedure characteristics
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In-stent restenosis ACC/AHA type C
Heparin
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Contrast amount (ml)
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Self Patients (n=226) Lesions (n=301) 1.3 ± 0.6
0.70
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Table III In-hospital clinical outcomes
Cardiac death
13 (5.7%)
3 (3.6%)
0.57
Q-wave myocardial infarction
3 (1.3%)
0
0.57
Urgent coronary bypass surgery
10 (4.4%)
5 (6.0%)
0.56
Urgent target lesion percutaneous intervention
6 (2.7%)
2 (2.4%)
1.00
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EMS (n=83) 3 (3.6%)
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Death
Self (n=226) 14 (6.2%)
p Value 0.58
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Table IV Multivariate logistic regression analysis for variables associated with door-to-balloon
5.30
Presentation during off-hours (versus on-
3.09
p Value
2.56-11.00
<0.001
1.63-5.87
0.001
1.58
0.86-2.91
0.14
1.10
0.88-1.39
0.40
0.90
0.57-1.43
0.66
1.89
0.64-5.62
0.25
1.20
0.66-2.19
0.56
1.85
0.71-4.77
0.21
1.61
0.41-6.22
0.49
Previous percutaneous coronary intervention
1.01
0.46-2.18
0.99
ACC/AHA Type C lesion
0.98
0.56-1.71
0.95
Intra-aortic balloon pump
0.79
0.40-1.57
0.50
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Self-transport (versus EMS-transport)
95% confidence interval
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Odds ratio
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time >90 minutes
hours)
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Female gender
Body mass index (10 kg/m2 increment)
Diabetes mellitus
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Previous congestive heart failure
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Peripheral vascular disease
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Age (10-year increment)
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Previous coronary bypass surgery
ACC/AHA, American College of Cardiology/American Heart Association; EMS, emergency medical services