Implementation and Integration of Prehospital ECGs Into Systems of Care for Acute Coronary Syndrome

Abstract

HomeCirculationVol. 118, No. 10Implementation and Integration of Prehospital ECGs Into Systems of Care for Acute Coronary Syndrome Free AccessReview ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessReview ArticlePDF/EPUBImplementation and Integration of Prehospital ECGs Into Systems of Care for Acute Coronary SyndromeA Scientific Statement From the American Heart Association Interdisciplinary Council on Quality of Care and Outcomes Research, Emergency Cardiovascular Care Committee, Council on Cardiovascular Nursing, and Council on Clinical Cardiology Henry H. Ting, MD, MBA, Chair, Harlan M. Krumholz, MD, SM, FAHA, Co-Chair, Elizabeth H. Bradley, PhD, David C. Cone, MD, Jeptha P. Curtis, MD, Barbara J. Drew, RN, PhD, FAHA, John M. Field, MD, William J. French, MD, W. Brian Gibler, MD, David C. Goff, MD, PhD, FAHA, Alice K. Jacobs, MD, FAHA, Brahmajee K. Nallamothu, MD, MPH, Robert E. O'Connor, MD and Jeremiah D. Schuur, MD, MHS Henry H. TingHenry H. Ting Search for more papers by this author , Harlan M. KrumholzHarlan M. Krumholz Search for more papers by this author , Elizabeth H. BradleyElizabeth H. Bradley Search for more papers by this author , David C. ConeDavid C. Cone Search for more papers by this author , Jeptha P. CurtisJeptha P. Curtis Search for more papers by this author , Barbara J. DrewBarbara J. Drew Search for more papers by this author , John M. FieldJohn M. Field Search for more papers by this author , William J. FrenchWilliam J. French Search for more papers by this author , W. Brian GiblerW. Brian Gibler Search for more papers by this author , David C. GoffDavid C. Goff Search for more papers by this author , Alice K. JacobsAlice K. Jacobs Search for more papers by this author , Brahmajee K. NallamothuBrahmajee K. Nallamothu Search for more papers by this author , Robert E. O'ConnorRobert E. O'Connor Search for more papers by this author and Jeremiah D. SchuurJeremiah D. Schuur Search for more papers by this author Originally published13 Aug 2008https://doi.org/10.1161/CIRCULATIONAHA.108.190402Circulation. 2008;118:1066–1079Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: August 13, 2008: Previous Version 1 Clinical case: A 58-year-old woman called 9-1-1 with acute onset of chest pain that had persisted for 30 minutes. She had a history of hypertension, hyperlipidemia, and type 2 diabetes mellitus but no previous history of myocardial infarction or heart failure. Her medications included aspirin, atorvastatin, lisinopril, and metoprolol. Paramedics were dispatched, and a prehospital ECG demonstrated 3- to 4-mm ST-segment elevation in leads I, aVL, and V2 through V6 (Figure 1). Her examination revealed a regular pulse of 90 bpm, a blood pressure of 100/60 mm Hg, clear lungs, and normal heart sounds with no murmurs. Paramedics interpreted the prehospital ECG and activated the catheterization laboratory en route to the hospital. On hospital arrival, the patient was transported directly to the catheterization laboratory. Coronary angiography demonstrated an occluded proximal left anterior descending artery, which was successfully treated with balloon angioplasty and a stent. The pertinent time intervals were as follows: paramedic dispatch to balloon time, 56 minutes; paramedic arrival at the scene to balloon time, 46 minutes; hospital door to balloon time, 23 minutes. Her biomarkers revealed a peak troponin T of 2.42 ng/mL and a peak creatine kinase muscle-brain isoenzyme of 26.8 ng/mL. An echocardiogram demonstrated normal left ventricular ejection fraction of 55%, with mild anterior hypokinesis, and the patient was discharged on hospital day 3. Download figureDownload PowerPointFigure 1. Prehospital ECG.Current Guidelines for Prehospital ECGs Among Patients With ST-Segment–Elevation Myocardial InfarctionAmerican Heart Association national guidelines,1–3 as well as other consensus and scientific statements,4–11 recommend that emergency medical services (EMS) acquire and use prehospital ECGs to evaluate patients with suspected acute coronary syndrome. Despite these recommendations, prehospital ECGs are used in fewer than 10% of patients with ST-segment–elevation myocardial infarction (STEMI),12,13 and this rate has not substantially changed since the mid-1990s. Furthermore, even when a prehospital ECG is acquired, the information is often not effectively translated into action and coordinated with hospital systems of care to decrease delays in reperfusion therapy.13 The purpose of this article is to summarize evidence concerning the benefits of using prehospital ECGs, review barriers and challenges to routine use, and recommend approaches to enhance their effectiveness for improving quality of care for patients with acute coronary syndromes.What Are the Benefits of Using Prehospital ECGs in Patients With STEMI?Multiple studies have demonstrated the benefits of prehospital ECGs for decreasing door-to-drug time and door-to-balloon time in patients with STEMI.12–30 The direction and magnitude of the time savings are clinically relevant, resulting in an approximately 10-minute decrease in door-to-drug time and 15- to 20-minute decrease in door-to-balloon time.12,13 However, these time savings may not reflect the full potential of prehospital ECGs to decrease delays in reperfusion therapy. In fact, studies have shown further reductions in door-to-balloon time when prehospital ECGs are used to activate the catheterization laboratory while the patient is en route to the hospital.31–37For patients transported by EMS without prehospital ECG, delay from symptom onset to reperfusion therapy, which reflects the overall period of ischemic injury, can be divided into 4 time intervals: (1) symptom onset to EMS arrival, (2) EMS arrival to hospital arrival, (3) hospital arrival to ECG, and (4) ECG to reperfusion. Prehospital ECG programs, if effectively implemented and coordinated with hospital systems of care, would be expected to decrease the latter 3 time intervals (Figure 2). The second interval is composed of time from first medical contact by EMS to hospital door, and EMS personnel may behave with more urgency if a diagnosis of STEMI has been made in the field. The third interval is essentially eliminated with a prehospital ECG. The fourth interval can be decreased by advanced notification of the hospital to receive and evaluate the patient, to activate the catheterization laboratory while the patient is en route, or to bypass the emergency department and transport the patient directly to the catheterization laboratory. Scholz and colleagues reported the impact of prehospital ECGs on these time intervals from 114 patients with STEMI treated within an integrated system of care.38 The system consisted of acquiring a prehospital ECG by emergency responders (in Germany, this was generally a physician), transmitting the prehospital ECG to a fax machine at the percutaneous coronary intervention (PCI) hospital cardiac intensive care unit, activating the catheterization laboratory en route if STEMI was diagnosed, and bypassing the emergency department when the catheterization laboratory team was on-site. Pertinent time intervals were collected for 1 year. Comparing performance in the last quarter of implementing this system with the first quarter (reference group), the time spent at the scene decreased from 25 to 19 minutes, time spent in the emergency department decreased from 14 to 3 minutes, time from arterial access to balloon decreased from 21 to 11 minutes, door-to-balloon time decreased from 54 to 26 minutes, and first medical contact to balloon time decreased from 113 to 74 minutes. The authors also concluded that systematic, quarterly feedback on performance to cardiology, emergency department, and EMS stakeholders was an important component in improving prehospital and hospital processes of care.38Download figureDownload PowerPointFigure 2. Reperfusion time goals for patients with ST-segment–elevation myocardial infarction.Can EMS Providers Acquire Prehospital ECGs?A survey found that 90% of EMS systems serving the 200 largest cities in the United States had 12-lead ECG equipment available in their ambulance systems.39 EMS providers can rapidly acquire diagnostic-quality prehospital ECGs with an average increase of 5 to 6 minutes in the on-scene time interval.14–16,28,40–49 To acquire diagnostic-quality prehospital ECGs, a valuable strategy is to educate EMS providers about the importance of careful patient positioning and lead placement. Movement artifact, lead misplacement, and poor skin contact can result in poor-quality tracing that can be misinterpreted by algorithms or EMS providers.One study, which used data from the National Registry of Myocardial Infarction between 1994 and 1996, found that patients with prehospital ECGs had time intervals that were 20 minutes longer from symptom onset to hospital arrival.12 This finding was difficult to interpret, however, as there was no measure of how long the prehospital ECG required and potential selection bias in who received a prehospital ECG. For example, patients who had a longer transport distance may have received a higher rate of prehospital ECGs as compared with those with a shorter transport distance. An analysis of the National Registry of Myocardial Infarction between 2000 and 2002 found that patients with prehospital ECGs did not have longer times from symptom onset to hospital arrival.13Can EMS Providers Reliably Interpret or Communicate Prehospital ECGs?Several studies have examined the feasibility of EMS providers identifying STEMI using prehospital ECGs with or without wireless transmission.20,36,50–58 The pros and cons for computer algorithm interpretation, paramedic interpretation, and wireless transmission for physician interpretation of prehospital ECGs are summarized in Table 1. There are no data to compare the effectiveness of these different approaches for diagnostic accuracy or quality of reperfusion therapy delivered to patients with STEMI. The choice of which option to use may also be limited by the specific resources available in the community or its local geography. ‘Table 1. Models for interpreting Prehospital ECGsMethod of Interpreting Prehospital ECGProsConsEMS indicates emergency medical services.Computer algorithm interpretationRapid, easyFalse-positive and false-negative rates higher than physician interpretationNo wireless network or technology requirementsParamedic interpretationRapid, easy No wireless network or technology requirementsRequires intensive education and quality assurance programMore complex in communities with multiple EMS providers and agenciesWireless transmission and physician interpretationTheoretically, lowest rate of false-positives and false-negativesNew technology requirement for EMS providers and hospitalMedical oversight can provide guidance on destination hospital and treatment en route Reliable wireless network Transmission unit on ambulance Receiver station unit at hospital Smartphones for physiciansRequires system to ensure immediate interpretation by physicianTransmission failuresStudies have also shown that paramedics with specific ECG training can reliably interpret prehospital ECGs without transmitting to a hospital or physician. Trained paramedics can identify STEMI with sensitivity ranging from 71% to 97% and specificity ranging from 91% to 100%,15,16,59–65 and with good agreement between paramedics and emergency department physicians (κ ranging from 0.59 to 0.73).20,60,64 The sensitivity (97%) and specificity (91%) of trained paramedics to interpret prehospital ECGs and diagnose STEMI was particularly high in one study, which included a 2-day training seminar.62 A study of this issue, conducted in the United States with 151 patients with suspected acute myocardial infarction transported by a large urban EMS system, found that trained paramedics had 80% sensitivity and 97% specificity in diagnosing STEMI with prehospital ECGs, with good agreement between paramedics and emergency physicians (κ=0.73).64Alternatively, prehospital ECGs can be transmitted by EMS for physician interpretation to drive decision making, but this approach has been limited by technology requirements for rapid and reliable transmission of prehospital ECGs. Two pilot studies have demonstrated that wireless transmission of prehospital ECG is feasible.36,55 In the Timely Intervention in Myocardial Emergency–Northeast Experience (TIME-NE) conducted in Concord, NC, 24 patients with STEMI had successful wireless transmission of prehospital ECGs to a hospital receiving station and the on-call cardiologist’s smartphone.55 The on-call cardiologist then decided whether to activate the catheterization laboratory on the basis of the prehospital ECG. Median door-to-balloon time decreased in this study to 50 minutes as compared with 101 minutes for historical controls; however, there were 19 patients with STEMI who experienced failed wireless transmission. In the ST-Segment Analysis Using Wireless Technology in Acute Myocardial Infarction (STAT-MI) study conducted in Newark, NJ, 80 patients had prehospital ECGs transmitted using a wireless cellular phone network to a secure hospital central server and to the on-call cardiologist’s smartphone.36 This model had no transmission failures; median time from prehospital ECG acquisition to availability on the remote server was 2 minutes and on the smartphone was 4 minutes. The door-to-balloon time was 80 minutes with use of prehospital ECGs, as compared with 146 minutes for historical controls without use of prehospital ECGs. In geographic regions with reliable wireless network coverage, wireless transmission of prehospital ECG for physician interpretation is feasible and reliable; however, current wireless networks can fail to transmit or encounter significant delays in up to 20% to 44% of cases as a result of wireless “dead zones” in a moving ambulance or in rural areas with sparse coverage.50,55,62,66,67Wireless transmission prehospital ECG systems are commercially available from Medtronic36,57 (Minneapolis, Minn), Welch Allyn55 (Beaverton, Ore), Zoll Medical30 (Chelmsford, Mass), and Phillips Healthcare (Andover, Mass). These systems acquire the prehospital ECG and automatically transmit the data using Bluetooth protocol to a nearby cellular phone. The cellular phone functions as a router to transmit the data to a central receiving station and smartphones via a wireless cellular network or wireless local area network (IEEE 802.11).68–71 A novel approach using camera phones with multimedia messaging service has been proposed and tested in 10 patients.72 A camera phone obtains a digital picture of the prehospital ECG paper printout and wirelessly transmits the picture to an e-mail account, and the ECG image can be viewed on any multimedia messaging service–capable device, such as a computer or smartphone. This approach may be a simple, low-cost, and innovative technology73 to communicate diagnostic image data and warrants further study for feasibility in real-world practices.Can EMS and Hospitals Organize Systems to Effectively Use Prehospital ECGs?EMS and hospitals should organize efficient systems of care for patients with STEMI from the prehospital phase of care to hospital arrival and reperfusion therapy in the hospital phase of care. The typical current process2 for emergency cardiac care initiated by a 9-1-1 call is contrasted with the ideal process in Figure 3. Historically, EMS providers have been trained to follow these steps in evaluating patients with chest pain in the field: (1) assess airway, breathing, circulation, and vital signs; (2) obtain focused history and examination; (3) assess cardiac rhythm; (4) initiate treatment with oxygen, aspirin, nitroglycerin, and morphine and insert intravenous line; (5) recommended: acquire 12-lead prehospital ECG at the scene, after the patient is transferred to the ambulance, or while en route to the hospital. Because the 12-lead ECG represents the critical data for diagnosis and decision making in patients with chest pain, it should be prioritized and performed as early as possible at the scene. If a STEMI is identified on the prehospital ECG, then scene times should be minimized, with expedited transport to the hospital. Moreover, if the prehospital ECG is communicated to the destination hospital shortly after first medical contact with EMS providers, then the hospital will have more time to prepare for the patient. Download figureDownload PowerPointFigure 3. Current versus ideal processes to integrate prehospital ECGs into systems of care.The information from a prehospital ECG and advanced notification should lead to efficient action by hospital systems of care to deliver prompt reperfusion therapy, including preparing to receive and evaluate the patient, activating the catheterization laboratory while the patient is en route, or bypassing the emergency department and transporting the patient directly to the catheterization laboratory.32,37,74 If patients are evaluated in the emergency department, the evaluation should be streamlined by having a physician and necessary resources (eg, translators, nurses) ready before patient arrival, following a standard protocol for treatment, and minimizing physical movement, such as transferring between stretchers. Although bypassing the emergency department may be intuitively faster, concerns have been raised about processes for obtaining informed consent, patient safety, and consideration of alternative diagnoses (eg, aortic dissection, intracranial hemorrhage) or other false-positives that may account for the ST-segment elevation on the ECG in up to 10% to 15% of patients.75–77 Furthermore, during off hours,78,79 the catheterization team may not have arrived at the hospital before the ambulance, and the patient will need to be observed in a critical care setting until the catheterization laboratory is ready to receive the patient.Can Regional Networks of Hospitals Organize Systems to Effectively Use Prehospital ECGs?Patients with STEMI who require interhospital transfer experience substantial delays with a median first hospital door-to-balloon time of 180 minutes.80 In the United States, regional networks of hospitals and systems of care have been implemented and evaluated to improve time to reperfusion therapy for patients who initially present to a community hospital without on-site PCI capability.35,81–83 Similar, but broader systems of optimizing reperfusion therapy across populations have also been in place in Europe for several years.24,84,85 European systems often have a physician in the ambulance, a central dispatch center for ambulances, and highly organized regional prehospital care, which stands in contrast to the disorganized, competitive environment in the United States.Prehospital ECGs can play an important role for triage of patients in a regional network of hospitals, and the two models proposed include prehospital triage versus interhospital transfer.3,11,74,86–89 The prehospital triage model transports patients with STEMI to the closest PCI center and bypasses hospitals without PCI capability. The interhospital transfer model focuses on advanced notification and efficient transfer of patients from non-PCI hospitals to PCI centers.11 Several key factors, including distance, urban versus rural location, collaborative versus competitive relationships between hospitals, and variability of EMS providers, influence which model is best suited for specific regional populations. An analysis of the US Census Survey and the American Hospital Association Annual Survey showed that 80% of the adult population live within 60 minutes of a PCI-capable hospital, and only 5% live farther than 90 minutes from one.90 However, there are still 20% of the adult population and large geographic areas that do not meet this standard. One model of regionalized STEMI care does not preclude the other. Both can coexist within a single network and are often driven by specific resources available within a community and local geography. No data comparing the models exist, and potential unintended consequences, such as exceptionally long delays to reperfusion, should be monitored.10,91How Have Prehospital ECGs Been Incorporated Into Existing Systems of Care?Many communities are implementing prehospital ECG programs that are in varying stages of development, and Boston, Los Angeles, North Carolina, and Ottawa (Canada) provide important contrasts (Table 2). The Boston EMS program, one of the country’s first, involves municipal paramedics trained to interpret and categorize prehospital ECGs as definite STEMI, possible STEMI, or nondiagnostic.9,64,92 Patients with definite STEMI or possible STEMI are triaged to the closest PCI hospital, and the former are brought directly to the catheterization laboratory and the latter are evaluated in the emergency department. The emergency physician decides whether to activate the catheterization laboratory on the basis of the paramedic interpretation while the patient is en route to the hospital. The Boston EMS program covers a relatively small geographic area (<50 square miles) with 60 to 70 municipal paramedics, and private EMS providers do not participate in the program. Table 2. Comparison of Existing Prehospital ECG ProgramsLocationPrehospital ECG InterpretationActivate Catheterization Lab en Route to HospitalBypass Non-PCI HospitalsPCI indicates percutaneous coronary intervention; MI, myocardial infarction; and STEMI, ST-segment–elevation myocardial infarction.Boston64,92Paramedic interpretationYes (activation by emergency department physician based on paramedic interpretation)Yes (for all patients with “definite STEMI” or “possible STEMI”)Los Angeles County76,87Computer algorithm interpretationYes (activation by emergency department physician based on computer algorithm interpretation)Yes (for all patients with acute MI)North Carolina83Mixed (used computer algorithm interpretation, paramedic interpretation, or wireless transmission)Mixed (activation by paramedics or emergency department physician)Mixed (paramedics occasionally diverted patients with STEMI to nearest PCI hospital)Ottawa65,96Paramedic interpretationYes (activation by paramedic through a central page operator)Yes (for all patients with STEMI)In contrast, the Los Angeles County EMS program includes all EMS providers, an area of >4000 square miles with approximately 2500 paramedics working for 27 agencies.76,87 The variability and sheer numbers of EMS providers to train in ECG interpretation were considered an insurmountable obstacle. The Los Angeles County EMS program therefore relies on computer algorithm interpretation that identifies ***ACUTE MI*** to prompt EMS transport of patients to the closest PCI center (or STEMI receiving center). The emergency physician decides whether to activate the catheterization laboratory on the basis of the computer algorithm interpretation while the patient is en route to the hospital. A few hospitals in Los Angeles County have started to pilot the feasibility of transmitting prehospital ECGs for physician interpretation. Both the Boston and Los Angeles programs are undergoing formal evaluation. There are also ongoing clinical trials in other parts of the United States evaluating the effectiveness of prehospital ECGs to decrease first medical contact to balloon/drug times.93–95The Reperfusion of Acute Myocardial Infarction in North Carolina Emergency Departments (RACE) Investigators implemented a statewide approach to improve timeliness of reperfusion therapy for patients with STEMI.83 The use of prehospital ECGs was high, and prehospital ECGs were acquired in 61% and 43% of patients with STEMI transported by EMS to PCI hospitals and non-PCI hospitals, respectively. However, the RACE program did not have standardized procedures for when to acquire a prehospital ECG, who would interpret the prehospital ECG, and how to integrate the prehospital ECG with systems of care. Each hospital and region decided how to interpret and integrate the prehospital ECG based on available resources, geography, and decisions by regional leadership.The Ottawa citywide system, which included 1 PCI center and 4 non-PCI hospitals located within 7 miles of the PCI center, reported their 1-year experience in 344 patients with STEMI.96 The first hospital door-to-balloon time was 69 minutes when paramedics acquired and interpreted a prehospital ECG and bypassed non-PCI hospitals as compared with 123 minutes when a prehospital ECG was not performed and the patient was initially brought to a non-PCI hospital and required interhospital transfer for primary PCI.What Are the Barriers to Implementing Successful Prehospital ECG Programs?What Are the Costs and Benefits for Prehospital ECG Programs?Currently, there are no cost-effectiveness models to evaluate this diagnostic technology from the different perspectives of patients, hospitals, payors, and society.97 One study reported that the incremental cost to upgrade prehospital ECG equipment to wireless capability was $16 100, which consisted of $11 000 for a receiving station, $600 for cell phones, and $4500 for data cables.57 The direct cost for prehospital ECG equipment with monitoring and defibrillation capability ranges from $9000 to $25 000, but this does not take into account other direct and indirect costs for training, quality assurance, and organizing complex EMS and hospital systems.8,98 Developing and implementing STEMI systems require substantial investment of resources that impact on the value of acquiring and using the information provided by prehospital ECGs. Comparative cost models for efficiently acquiring, interpreting, and transmitting prehospital ECGs within the context of STEMI systems will be informative and valuable. Additionally, it will be important to compare the development of STEMI systems of care with other healthcare priorities, both in cardiovascular medicine and other disciplines.What Training and Maintenance of Competency Do EMS Providers Need?In the United States, EMS providers are trained to several competency levels. Although the federal government (http://www.nhtsa.dot.gov/portal/site/nhtsa/menuitem.2a0771e91 315babbbf30811060008a0c/) has defined a standard curricula for each of 4 levels (first responder, emergency medical technician [EMT]–basic, EMT-intermediate, and EMT-paramedic),99 many states use definitions and regulations that vary significantly between states as well as within a single state (rural versus urban areas). The National Registry of EMTs (www.nremt.org), the nation’s de facto “board” for certification, currently certifies EMS personnel at the first responder, EMT-basic, EMT-intermediate/1985, EMT-intermediate/1999, and EMT-paramedic levels.First responder roles are often provided by firefighters or law enforcement officers.9 EMT-basic personnel provide basic life support, including first aid, cardiopulmonary resuscitation, oxygen, and early defibrillation. EMT-intermediate and EMT-paramedic personnel provide advanced life support, including intubation and intravenous medications. Prehospital ECG acquisition has historically been limited to EMT-paramedic. The current EMT-paramedic national standard curriculum99 includes the following objectives intended to provide paramedics with a basic understanding of the pathophysiology and ECG features of acute myocardial infarction: 5–2.9 Identify the arterial blood supply to any given area of the myocardium.5–2.22 Discuss the pathophysiology of cardiac disease and injury.5–2.34 Relate the cardiac surfaces or areas represented by the ECG leads.5–2.48 Recognize the changes on the ECG that may reflect evidence of myocardial ischemia and injury.5–2.78 Identify the ECG changes characteristically seen during evolution of an acute myocardial infarction.The National Association of EMS Educators (www.naemse.org) is presently revising all of the existing national standard curricula for EMS with new standards. The initial draft of this document, released in June 2007, includes 12-lead ECG interpretation as a required competency for paramedics. Currently, no standards exist regarding how much initial and subsequent periodic education is required to achieve and maintain competency in prehospital ECG interpretation. Also, there are no standard protocols for when and what patient subsets to obtain a prehospital ECG, as well as what to do with the data.It has been proposed that prehospital ECG acquisition be extended to EMT-basic and EMT-intermediate levels.9 A preliminary study showed that EMT-basic personnel could acquire, but not interpret, ECGs in a comparable amount of time as compared with EMT-paramedics.100 Although rural geographic areas without paramedic coverage could benefit by extending prehospital ECG acquisition skills to EMT-basic personnel, this would require significant changes in current curriculum, training, protocols, and policy.EMS systems vary substantially with regard to configuration and structure, each using some combination of EMS providers to deliver emergency medical care for rural, suburban, or urban communities. Physician oversight also varies, with only a small number of large EMS systems having full-time physician medical directors. Given the challenges with EMS training, maintenance of competency,101–103 quality management, and medical oversight, there is no “one size fits all” or even “one size fits most” solution.How Will Patients With Acute Coronary Syndromes Use EMS?The reluctance of patients with acute coronary syndromes to call 9-1-1 is a major obstac