Prehospital Assessment and Systems of Care

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.