Heart disease has been the leading cause of death in America for over 80 years. An estimated 935,000 people in America suffer a myocardial infarction each year at an estimated annual cost of $151.6 billion.^1,2 Although the development of EMS is often ascribed as a response to America’s shocking rates of morbidity and mortality from motor vehicle accidents, emergency cardiac care has also driven EMS development and in many ways has become the central mission of modern EMS. From some of the first work on prehospital cardiac care as published by Frank Pantridge et al in 1967³ to large multisystem studies of cardiac arrest survival published in the past few years, it is clear that much progress has been made. Yet the basic tenets of prehospital cardiac care remain simple: identification of the patient with a cardiac emergency; stabilization; selection of an appropriate receiving facility; safe and timely transport to that facility.

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  Understand the goals of prehospital treatment for patients with acute coronary syndrome.

  
  
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  Discuss destinations, including options for treatment as well as transfer.

  
  
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  Learn about treatment options for patients diagnosed with arrhythmias.

  
  
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  Consider high-risk patients and special cardiac situations and equipment.

  
  
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  Discuss other etiologies of chest pain and approaches for these patients.

GENERAL APPROACH TO CHEST PAIN

The prehospital approach to the ACS patient begins with identification of potential patients. Emergency medical dispatch (EMD) has been designed to assist with this, but these programs tend to overtriage and, as they rely on data from the lay public, can also fail to identify ACS patients.⁴ For this reason, any dispatched chief complaint suggestive of ACS should be considered as such until it can be properly verified.

Upon arrival, scene safety is always the first step after which a brief scene size-up should be conducted to ensure that adequate equipment and resources are either present or have been requested. After quickly assessing airway, breathing, and circulation, it is essential that a focused history and physical examination be obtained, even if the patient has classic complaints of left-sided chest pain and shortness of breath.

If a patient is complaining of atraumatic chest pain, he or she should be placed on a cardiac monitor and 12-lead ECG obtained. Prehospital ECG has been shown to improve outcomes in patients with STEMI and non-STEMI patients.⁵ IV access should be attempted and appropriate medical therapy started. Package the patient for transport, and transport the patient to the most appropriate facility. The patient needs to be monitored throughout the call for signs of deterioration, with changes in patient status addressed promptly (Table 39-1).

Multitasking with limited providers and resources is the overarching principle in the approach to a patient with chest pain. Therefore, the physician on scene needs to be proficient in starting IVs, properly administering a variety of medications (Table 39-2), and utilizing and troubleshooting all the equipment in the transporting vehicle. Transportation should begin as soon as feasible. The team’s approach should be goal oriented, for example, reaching definitive care quickly and safely, rather than task oriented, for example, obtaining IV access before proceeding to the next step.

If a prehospital diagnosis of ACS is made, determining the most appropriate destination becomes one of the most essential components of patient care. Many EMS systems utilize point-of-entry plans; these should be followed whenever possible. As a general principle, the patient should be transported to the nearest facility capable of providing definitive cardiac care. In most locations, this is a facility that provides emergent interventional cardiac catheterization. In rural locations, the transport time to such a facility may be prohibitive. Therefore, an appropriate facility may be one capable of administering thrombolytic therapy. Many factors, including time of day and weather conditions, affect such a decision. Prehospital delivery of medications like ticagrelor⁶ and glycoprotein IIb/IIIa inhibitors^7,8 does not appear to improve outcomes.

Mode of transportation can also be a critical element of patient care. ACLS-trained providers should transport ACS patients whenever available. However, in locations where transport time to definitive care is short and arrival of ACLS-trained providers will be significantly delayed, BLS transport may be a reasonable option. On the other end of the spectrum, helicopter or fixed-wing transport can rapidly provide skilled personnel to transport even the sickest ACS patient. Air medical transport should be reserved for patients who are time critical, meaning transport time will be reduced compared to that provided by ground-based ALS units with the time savings, providing benefit to the patient, or for patients who are care critical, meaning that the patient requires medical therapies or medications en route which cannot be provided by the ALS ground units.

PREHOSPITAL TREATMENT ACS

Treatment of the patient diagnosed with ACS begins with initial stabilization. This includes immediate assessment of airway, breathing, and circulation and addressing any problems identified. Supplemental oxygen should be provided (at least 2 L or more as indicated) and continuous cardiac monitoring implemented. Insert two IVs, preferably 20 g or larger. If the patient is ambulatory on arrival, he or she should be placed in a seated position and restricted from further ambulation.

The mainstay of pharmacologic therapy for ACS is aspirin; no other prehospital pharmacologic therapy approaches aspirin in reducing mortality.⁹ Four 81-mg aspirin tablets constitute the most common dose, chewed, not swallowed, as this speeds absorption. The only absolute contraindication to aspirin is an aspirin allergy.

The patient with chest pain or pressure and adequate blood pressure should receive nitroglycerin sublingually (0.4 mg) repeated every 5 minutes typically up to three doses if discomfort persists; however, additional doses can be given if blood pressure remains stable and pain continues. Consider ensuring functional IV access prior to administering nitroglycerin due to possible hypotension. This is more common if the myocardial infarction (MI) involves the right ventricle. Therefore, if evidence of inferior MI is present on the initial 12 lead, right-sided leads should be performed. If the right ventricular is involved, the patient will be preload dependent, meaning his or her symptoms will respond better to intravenous fluids instead of nitroglycerin. Consider a continuous infusion of nitroglycerin if chest pain persists, blood pressure is adequate, and transport times are sufficiently long.

In a patient with a diagnosed ACS who continues to have chest pain after three doses of sublingual nitroglycerin, morphine may be administered for pain control. The role of morphine in patients with unstable angina or non-ST-elevation myocardial infarction (NSTEMI) is questionable due to concerns for increased mortality,¹⁰ though it is still a class I intervention for patients experiencing an ST-elevation myocardial infarction (STEMI)¹¹ (Figure 39-1). Pain management with fentanyl may be a more acceptable alternative to morphine.

Additional pharmacologic therapies for ACS are not routinely given in the prehospital setting. Unfractionated heparin is used for anticoagulation in the hospital setting, but is not a practical option prehospitally due to difficulties with administration, laboratory testing, and unpredictable anticoagulation effects. It is slowly being replaced by low-molecular-weight heparins,¹² which again are typically administered in the hospital setting. β-Blockers have traditionally been used early in ACS, although they are no longer indicated in the prehospital and ED environments due to concerns for cardiogenic shock and studies that do not demonstrate benefit with early administration.¹³

Rural EMS systems with transport times to a PCI capable facility in excess of 90 minutes may be candidates for a prehospital fibrinolysis protocol. If fibrinolysis is considered, it needs to be done immediately after identification of an STEMI, and should be done with the use of a specific fibrinolytic checklist and in consultation with the receiving facility.¹¹

The receiving facility needs to be notified of an incoming patient as soon as possible, in keeping with local protocols. Many EMS systems allow for transmission of prehospital ECGs, which can enable the receiving physician to review the ECG and facilitate activation of the catheterization team. Ideally, transmission of the ECG should not delay patient transport. Should the cardiogram demonstrate an STEMI, the catheterization team should be activated prior to patient arrival, in accordance with local and institutional protocols. Bypassing non-PCI centers has been shown to be safe¹⁴ and is recommended if the time between first medical contact and balloon at the destination facility is less than 90 minutes and transport times are under approximately 30 minutes.¹¹

CONSIDERATIONS FOR INTERFACILITY TRANSFER OF PATIENTS WITH ACS

Non-PCI capable hospitals with door-to-departure time of less than 30 minutes may consider rapid transfer as an acceptable option to fibrinolysis. ACS patients require the most rapid method of transfer that will safely deliver them to the destination hospital. In some systems ground transport via an ALS crew may be faster than air medical transport with a critical care crew. Regardless of the method chosen, transfer of ACS patients is a common occurrence, and transporting crews should be well practiced in efficiently moving the patient through the system from one hospital to the other as quickly and safely as possible.

One method of decreasing times for interfacility transfers is to use bolus dosing of medications in place of continuous intravenous infusions for medications such as nitroglycerin, heparin, and GP2B3A inhibitors.¹⁵ Most interfacility transports are short enough that the duration of action of bolus medications is sufficient for the transport. This also serves to decrease the complexity of the patient encounter for the prehospital provider who no longer needs to focus on monitoring and troubleshooting pumps and can pay more attention to overall patient status and needs.

The prehospital provider transferring a patient with a diagnosed ACS should be prepared to treat complications associated with the patient’s condition. Arrhythmias are the most commonly encountered condition. Cardiogenic shock is one of the most serious complications of MI, and requires vigilance to diagnose. Hypotension is the cardinal marker of cardiogenic shock in the out-of-hospital environment. Fluid boluses are the first line of treatment, remembering the patient with a right-ventricular infarct is preload dependent and so will improve hemodynamically with fluid boluses but the patient with left ventricular involvement will rapidly develop pulmonary edema. The most commonly available vasopressor in the prehospital setting is dopamine, and may be necessary to treat hypotension in the cardiogenic shock patient. Due to the arrhythmogenic potential of dopamine, careful monitoring of the patient’s cardiac rhythm is necessary.

Intra-aortic balloon pumps (IABPs) are sometimes placed during cardiac catheterization for the management of cardiogenic shock. The prehospital provider may transfer a patient with an IABP in place. This is a specialized instrument requiring careful monitoring and an understanding of how to troubleshoot the device in case of malfunction or deterioration in patient condition. This understanding is outside the knowledge base of many physicians and most prehospital providers. Therefore, IABPs should only be transported by providers who have received specific training in their use or with the addition of a specialty team who routinely performs such transfers.

APPROACH TO THE PATIENT

Similar to treatment in the emergency department, the approach to prehospital care of any patient with a cardiac arrhythmia focuses on identification of the dysrhythmia, assessing patient stability, and immediate treatment of any potentially life-threatening rhythms. When assessing the stability of the patient, one should evaluate for presence of chest pain, hypotension (SBP < 100), alteration of mental status, diaphoresis, and changes in skin color. The distinction between stable and unstable or borderline patients will help determine which of several possible treatments is most appropriate. For example, a 60-year-old male with a heart rate of 140 who is awake, alert, mentating well, and does not complain of chest pain may benefit from vagal maneuvers and intravenous fluids. If this same patient were complaining of dyspnea and chest pain, adenosine would be indicated. Similarly, if the patient has chest pain and a systolic blood pressure of 85, then electrical synchronized cardioversion would be indicated.