Case Vignette
A 56-year-old riverboat captain experienced sudden onset of shortness of breath and diaphoresis at 1:30 am while on his boat near Red Wing, Minnesota ( Figure 5-e1 ). Emergency Medical Services (EMS) were activated from the boat, and at 2:26 am , the first responders from the Red Wing Fire Department arrived on scene. At 2:38 am , a 12-lead electrocardiogram (ECG) ( Figure 5-e2 ) was obtained showing a large inferior-posterior ST-elevation consistent with ST-elevation myocardial infarction (STEMI). By 3:09 am , a helicopter arrived to transport the patient to the Minneapolis Heart Institute Regional STEMI Center 55 miles away, in Minneapolis, Minnesota. The patient was loaded in the helicopter at 3:20 am ; treated with aspirin 325 mg, clopidogrel 600 mg, and a weight-based intravenous bolus of unfractionated heparin; and arrived at the STEMI center at 3:38 am . He underwent emergent cardiac catheterization, which revealed a 100% thrombotic occlusion of the mid-right coronary artery ( Figures 5-e3A and 5-e3B ) and had a successful primary percutaneous coronary intervention (PPCI). Post-PPCI, his left ventricular ejection fraction was 65% with mild hypokinesis of the inferior wall. The prehospital ECG-to-device time was 101 minutes, and the door-to-device time was 41 minutes. He was discharged from the hospital the following day and was asymptomatic at 1-year follow-up.
In summary, a 56-year-old with acute onset of shortness of breath in the middle of the night, in the middle of the Minneapolis River, 55 miles from the nearest PPCI center, was able to receive guideline-directed medical therapy and PPCI in a timely fashion with an excellent outcome, as a result of a regionalized STEMI system with prespecified standardized protocols and transfer agreements in place.
Introduction
Nearly 500,000 Americans experience an acute STEMI each year in the United States (see Chapter 2 ). A decade ago, many of these patients did not receive appropriate treatment for this life-threatening condition. Approximately 30% of STEMI patients did not receive any form of reperfusion therapy (PPCI or fibrinolysis). Of those who underwent PPCI, only 40% were treated within the recommended time frame (medical contact-to-device time ≤90 minutes). For patients who received fibrinolytics, less than 50% met the recommended door-to-needle time of ≤30 minutes. Care for STEMI patients has evolved dramatically over the past 30 years (see Chapter 13 ). The 1990s was a period of rapid evolution in STEMI care, from fibrinolytics to coronary angiography with balloon angioplasty, and subsequently, coronary stenting. However, it was not until the past decade that the systems for delivery of care became a focus of attention.
Regional STEMI systems of care have drastically changed the approach to health care delivery for acute coronary syndromes (ACS), providing access to PPCI for an increasing proportion of the population. This evolution has resulted in dramatic improvements in time to treatment ( Figure 5-1 ) and cardiovascular outcomes ( Figure 5-2 ). Chapter 13 provides an overview of the principles of care for acute MI, including the critical relationship between time to treatment and outcomes in STEMI (see Figure 13-3 ). Selection among the approaches to reperfusion therapy is addressed in Chapter 14 . Treatment with fibrinolytic therapy is discussed in Chapter 15 , and PPCI is discussed in Chapter 17 . In this chapter, we describe the design and implementation of complex regional systems of care and examine the individual components of any successful STEMI system of care that include: (1) rapid and thorough prehospital evaluation and triage, typically performed by EMS; (2) referring hospitals and clinics (“referral centers”); and (3) regional, tertiary care receiving centers capable of PPCI, preferably with surgical backup (“receiving centers”) ( Figure 5-3 ).
Although these critical elements of triage, transportation, referral centers, and receiving centers are integral components of a STEMI system, no two STEMI systems are alike. Diversity in geography, politics, and sociodemographics across the United States and throughout the world result in a wide variety of STEMI systems, which are all directed toward the same goal—to increase access to timely reperfusion with PPCI for STEMI by reducing delays inherent in systems of care (see also Chapter 13 and Figure 14-1 ). In the United States, current American College of Cardiology Foundation (ACCF)/American Heart Association (AHA) guidelines (see Figure 13-5 ) recommend EMS transportation of STEMI patients directly to a receiving center hospital for PPCI, with an ideal first medical contact to PPCI device (FMC-to-balloon) time goal of less than 90 minutes (class I, level of evidence B). Furthermore, for patients presenting to a non–PPCI-capable hospital, immediate transfer to a receiving center hospital for PPCI is the recommend reperfusion strategy with a goal FMC-to-device time of less than 120 minutes (class I, level of evidence B).
Prehospital Evaluation
Evolution of Emergency Medical Services
The first U.S. Civilian ambulance service was formed in 1865 in Cincinnati, Ohio. It was comprised of local hospital interns who drove a horse-drawn carriage ( Figure 5-e4 ). The first “rescue squad,” designed to deliver basic first aid to civilians was formed in the late 1920s in Roanoke, Virginia. However, there were few advances in emergency care services until the late 1960s. In 1966, the National Academy of Sciences published a statement that many deaths in the United States were preventable and could be reduced through community education, safety standards, and prehospital coordination. This recognition, along with advances in the field of cardiopulmonary resuscitation (CPR) and management of out-of-hospital cardiac arrest (OHCA), served as the impetus for the first statewide EMS system in Maryland, thanks in large part to the efforts of R. Adams Cowley. In 1968, St. Vincent’s Hospital in New York City built the nation’s first mobile coronary care unit, staffed initially with physicians and later by paramedics. This unit was the first to evaluate and triage patients with cardiac complaints and included a portable, battery-powered cardiac monitor and defibrillator, as well as supplies for intravenous access, mobile oxygen, and medications. From here, the modern day EMS system was born. Today, EMS providers in the United States care for an estimated 22 million patients per year. The incorporation of various vehicles, including ambulance vans, helicopters, and airplanes, has allowed for rapid mobilization and transportation of patients over great distances in short periods of time.
With the development of formal EMS systems throughout the country, the framework was in place to build complex regional systems of care for a variety of medical conditions. The first systems of care were designed for trauma patients and acute cardiovascular emergencies, such as STEMI and stroke. The integration of EMS and the incorporation of the prehospital phase for ACS evaluation and diagnosis are integral components of any regionalized STEMI system of care. EMS providers and other first responders have four primary responsibilities: (1) prehospital evaluation, (2) treatment, (3) triage, and (4) transfer ( Figure 5-4 ).
Prehospital Systems
The prehospital evaluation should consist of a focused history and physical examination, including a complete assessment of vital signs and a prehospital 12-lead electrocardiogram (PHECG). Earlier STEMI diagnosis based on the PHECG facilitates in-hospital STEMI treatment. Hospitals with the shortest door-to-balloon (D2B) times are those that have incorporated prehospital STEMI diagnosis with pre-activation of the cardiac catheterization laboratory (CCL). This strategy requires a multidisciplinary team approach in which either the emergency physician or specially trained EMS providers activate the CCL without cardiology consultation.
However, the rapid transport of STEMI patients to the nearest PPCI-capable facility may be limited by several factors. First, only a minority (≤5%) of EMS transported patients with chest pain actually have STEMI. Second, an inadequate number (∼50%) of EMS systems have PHECG capabilities. Third, in some regions a mandate still exists for transport of patients with suspected STEMI to the nearest facility, even if that facility does not provide PPCI. Fourth, evolution toward a more integrated process of prehospital care is complicated by the fact that there are 329 different EMS regions in the United States, with more than 993 hospital-based EMS systems. Remarkably, hospital-based EMS systems represent only 6.5% of all EMS providers, with the remainder comprised of private, third party systems (48.6%) and fire station–based systems (44.9%).
Integrated Emergency Medical Systems
Although the transport time to a specialized PPCI center may appear long, the benefits outweigh the drawbacks when an integrated EMS system incorporates pre-notification, termed “parallel processing.” Some have proposed doubling the allotted transport time for suspected STEMI patients, to allow transportation of these patients directly to a “center of excellence,” where the target D2B time is ≤60 minutes. Process efficiency can be achieved only through an integrated system for STEMI care that incorporates the PHECG for earlier diagnosis, expedited triage, and readily available, rehearsed transport systems. A more uniform evolution toward integrated STEMI care has been impeded by a lack of funding, diverging incentives, a lack of coordinated objectives, and at times, competing strategies. For example, in many regions, particularly those without state-regulated certificate of need requirements, there has been a proliferation of new catheterization laboratories for the provision of PPCI without regard for PPCI volume or surgical backup. Conversely, other regions have developed integrated EMS systems that focus on prehospital diagnosis, triage, and transfer to an established center of excellence proficient in both primary and elective PCI. Although expansion of PPCI-capable centers can improve access to care, more efficient use of existing PPCI centers through prehospital–EMS integration has been proven to be a more cost-effective strategy. Only recently have sophisticated modeling techniques been used to compare the relative efficacy and/or cost of these competing strategies for the care of STEMI patients. Importantly, a strategy focused on EMS integration, prehospital diagnosis, triage, and transportation with more effective use of existing PPCI facilities was found to be more effective and less costly than a strategy of creating new PPCI facilities ( Figure 5-e5 ).
The coordination of strategies, as well as the integration of essential prehospital and in-hospital resources for ACS care on the state level has been the focus of the AHA Mission: Lifeline initiative, which was created as a response to missed opportunities for prompt, appropriate STEMI treatment. The Mission: Lifeline goal is to improve outcomes for STEMI patients by building integrated care networks through community outreach, training, and education of civilians and EMS personnel. The AHA Mission: Lifeline also provides a blueprint for hospitals and administrators to implement systems of care. At present, approximately 65% of U.S. citizens have access to a Mission: Lifeline system of care, the number of which has increased greatly over the past decade ( Figure 5-5 ).
Although the AHA’s Mission: Lifeline has been instrumental in the proliferation of STEMI systems of care throughout the country, the ACC’s Door-to-Balloon Alliance sought to improve D2B times in PPCI hospitals. The D2B Alliance was launched in 2006, in partnership with the Institute for Healthcare Improvement. This Alliance provided hospitals with evidence-based strategies and supporting tools needed to reduce D2B times through a focus on process improvement, parallel processing, and interdisciplinary collaboration. The keys to reducing D2B times are (1) the emergency department (ED) physician (or EMS PHECG) activates the CCL, (2) one call activates the entire team, (3) the CCL team is ready within 30 minutes of receiving the activation call, (4) prompt data feedback, and (5) a team-based approach with commitment from all levels. When launched, the initial goal was to achieve D2B times of ≤90 minutes for 75% of STEMI patients presenting to a PPCI facility. In the decade since its inception, the D2B Alliance has facilitated dramatic improvements in D2B times across the country (see Figure 5-1 ). Through the efforts of these organizations, as well as the individual efforts of countless nurses, doctors, administrators, and EMS providers, the STEMI receiving network system of care model has blossomed both domestically and abroad.
Systems of Care in Practice
ST-Elevation Myocardial Infarction Systems of Care: The European Experience
The rapid restoration of normal coronary blood flow, via pharmacological and/or mechanical recanalization of an occluded coronary artery, limits the extent of myocardial necrosis and reduces the mortality of patients who present with STEMI (see Figure 13-3 ). PPCI has demonstrated more frequent, complete, and durable coronary reperfusion in both randomized controlled clinical trials and observational studies (see Chapter 14 and Chapter 17 ). For these reasons, PPCI is the preferred revascularization modality as long as an experienced operator can provide it in a timely manner ( Figure 5-6 ; also see Figure 13-5 ). On the basis of these principles, the first randomized controlled trials, which compared long-distance transport to PPCI centers with primary fibrinolysis performed at local hospitals, were performed in Europe in the early 2000s. Overall, these studies, which are discussed in Chapter 14 , demonstrated that transferring patients with STEMI to a tertiary angioplasty facility could be both safe and effective. In context, transfer-related delays were generally more than 1 hour and FMC-to-device times were more than 2 hours ( Figures 5-e6A and 5-e6B and 5-e7A and 5-e7B ). Transfer-related delays that prolong the time for initiation of reperfusion by more than 90 minutes appear to favor fibrinolytic therapy (see Chapter 14 and Figure 14-9 ).
Contemporary STEMI systems of care in Europe include the VIENNA STEMI network and the SAMU system in Paris. The former is based on a rotational call between the only two high-volume PPCI centers available. In the latter, physicians routinely staff the ambulances and initiate prehospital care. A pharmaco-invasive strategy that uses prehospital fibrinolytic therapy is commonly used in these two systems, particularly for patients presenting early after STEMI (<3 hours). These and other international STEMI systems of care are summarized in Table 14-e1 .
Despite the results of these trials, many were pessimistic that such a system would work within the construct of U.S. health care because of geographic, political, and financial barriers. In addition, the only U.S. STEMI transfer trial (air-PAMI) reported a total median D2B of 155 minutes with equivocal results, although the trial was small and underpowered.
ST-Elevation Myocardial Infarction Systems of Care: The United States
In the early 2000s, there was mounting evidence that STEMI care within the United States was inadequate. In 2004, the ACC/AHA guidelines for the care of STEMI patients made a class I, level of evidence B recommendation that “the delay from patient contact with the healthcare system (typically, arrival at the Emergency Department (ED) or contact with EMS) to initiation of fibrinolytic therapy should be less than 30 minutes” ( Figure 5-6 ; also see Figure 13-5 ). Alternatively, if PPCI was chosen, “the delay from patient contact with the health care system (typically, arrival at the ED or contact with EMS) to balloon inflation should be less than 90 minutes.” This marked the first time such a recommendation regarding the timing of reperfusion appeared in the ACC/AHA guidelines. Despite this strong recommendation, data from the National Registry of Myocardial Infarction revealed that D2B times in the United States were too slow, in particular for patients who were transferred for PPCI. With a median D2B time of 180 minutes, only 15% of transfer patients achieved a D2B time of less than 120 minutes, and only 4% of patients had a D2B time that met the recommended standard of less than 90 minutes. In 2006, the Institute of Medicine (IOM) published a report titled “Hospital Based-Emergency Care: At the Breaking Point.” In this report, the IOM concluded that overcrowding of emergency rooms, as well as “fragmented” care and inaccessibility of specialists were the largest barriers to improving emergency medical care. The IOM called for drastic changes in coordination of care, policy, funding, and research practices.
Fortunately, despite the many obstacles, there were firm believers in the potential of STEMI systems that were willing to invest incredible time, energy, and resources into building functional STEMI systems within the United States. In 2003, the Minneapolis Heart Institute (MHI) at Abbott Northwestern Hospital began to build one of the first regional STEMI systems in the United States. The system was modeled after successful regional trauma systems and was built on the premise that accelerated diagnosis, streamlined processes, and standardized care protocols were the keys to implementing and maintaining a successful STEMI system within the United States. The MHI system functioned as a “wheel-and-spoke” model, with MHI at the center of the system. Referral hospitals and clinics within a 60-mile radius of MHI were considered Zone 1, with a standardized protocol that included evidence-based adjunctive medications (aspirin, clopidogrel, weight-based intravenous bolus of unfractionated heparin, and intravenous β-blockers) and a prespecified transfer plan from each site. The regional STEMI-system grew quickly and expanded to Zone 2, which included referral hospitals within a 60- to 210-mile radius, using a similar standardized protocol with the addition of one-half dose of intravenous tenecteplase and immediate transfer to MHI for pharmaco-invasive PCI ( Figure 5-7 ; see Chapter 14 ). In addition to the standardized protocol, the MHI group placed high priority on gathering data for quality assurance purposes and feedback. Through the next several years, the MHI group was able to demonstrate marked improvements in a variety of outcomes, including death, re-infarction, stroke, and length of hospital stay.
