J Emerg Med. 2010; 39:462–7.
CHAPTER 9 Chest pain and acute coronary syndromes
Joseph P. Ornato, Michael R. Sayre, and James I. Syrett
Introduction
In the United States, someone experiences a myocardial infarction every 26 seconds, and alarmingly, the disease claims one life each minute [1]. Heart disease accounts for twice as many deaths in the United States as are attributed to unintentional injuries, which has major implications for EMS systems [2]. About half of individuals who suffer acute myocardial infarctions (AMI) are transported to the hospital by EMS, and many more patients call EMS for help because they are experiencing chest pain [3].
The prehospital management of chest pain has improved with better clinical examination, earlier administration of effective medications, and the broad use of 12‐lead ECGs to detect acute coronary syndromes (ACS) and myocardial infarction more accurately before arrival in the emergency department (ED) [4]. Because more rapid reperfusion during acute myocardial infarction improves heart function and patient survival, EMS and health care systems have focused on developing strategies to identify chest pain patients with myocardial infarction quickly and to provide effective treatment while transporting them directly to definitive care [5–7].
The goals of management for patients with chest pain include rapid identification of the patient with ACS, relief of symptoms, and transport to an appropriate hospital. This chapter will cover the assessment and treatment of patients with the chief complaint of chest pain and will focus on the scientific basis for prehospital medical care of those patients. It will also review common conditions that can cause chest pain.
General approach
When evaluating a patient with a complaint of chest pain, EMS professionals should begin by assessing the patient’s stability and then obtain a basic clinical history and examination. Early in the assessment, an EMS clinician should apply a cardiac monitor to rapidly identify dysrhythmias, perform a diagnostic 12‐lead ECG, and administer specific treatment depending on the results of the initial evaluation. Because only a small minority of the patients with chest pain actually have ACS, maintaining vigilance in this assessment and diagnostic routine can be difficult [8].
Complete accuracy in the diagnosis of chest pain is not always possible in any setting, not even in the hospital [9]. The prehospital clinician should not expect to diagnose a patient with a complaint of chest pain definitively. A careful history can lead the clinician to a correct “category” of diagnosis much of the time. As a general approach, the patient should be treated as if he or she has the most likely serious illness consistent with the signs and symptoms.
Discomfort due to cardiac ischemia is usually, but not always, substernal and may radiate to the shoulder, either arm, both arms, upper abdomen, back, or jaw [9, 10]. Other symptoms such as nausea and diaphoresis are commonly present but do not accurately predict the presence or absence of ACS. Cardiac disease is most often seen beginning in middle‐aged men and older women. However, even younger adults under the age of 40 with chest pain but no cardiac risk factors and a normal ECG have a 1%–2% risk of ACS [11]. Taking a focused history using the “PQRST method” can be helpful (Box 9.1).
Box 9.1 Historical aspects of chest discomfort: the PQRST method
P:What provoked the pain or what was the patient doing when the pain started?
Q:What is the quality of the pain; burning, aching, squeezing, or stabbing?
R:Is there any radiation of the pain; does it go to the neck, jaw, arm, or back?
S:How severe is the pain? On a scale of 1 to 10, with 10 being the worst pain in one’s life, what is the pain now, and how has it changed?
T:What are the temporal aspects of the pain? How long has it been present? Has it occurred before? When?
There are many causes of chest pain, and their incidence changes depending on the characteristics of the population being studied. Patients calling on EMS are more likely to have acute myocardial infarction or other serious causes of chest pain than are patients in the general ED population [3]. Although the majority of this chapter focuses on the management of an ACS, other causes of chest pain are present more commonly.
Role of emergency medical dispatch
Prehospital care of the patient with a complaint of chest pain begins at emergency medical dispatch. Identification of patients suspected to have ACS allows an EMS system to send advanced level clinicians to the patient. Many EMS systems with both basic and advanced level ambulances use a trained emergency medical call taker who asks the caller a series of questions to determine the nature of the emergency and the likelihood that advanced level care will be needed (see Chapter 88).
A retrospective cohort study from England took a rigorous approach to determining the accuracy of one set of dispatcher questions in identifying patients with ACS [12]. Approximately 8% of calls at the “9‐9‐9” center were classified as “chest pain.” Subsequent chart review at the hospital identified all patients with the ultimate diagnosis of ACS and found that this represented only 0.6% of all 9‐9‐9 patients. Approximately 80% of the ACS patients were classified correctly as chest pain at the dispatch level. Another 7% were classified in a variety of other categories that still received a paramedic level response (e.g., severe respiratory distress). Sensitivity of the dispatch system for detecting ACS was 71% and specificity was 93%. However, a great deal of over‐triage occurred, and the positive predictive value of the dispatch system for detecting ACS was only 6%. Additional refinement of the dispatch question sequence to reduce over‐triage seems possible. The emergency dispatch question sequence for stroke performs much better, with a positive predictive value of 42% and a similar sensitivity to ACS at 83% [13].
Although an ACS patient can present with a variety of clinical symptoms, a study in Utah revealed that more than half of patients proven to have AMI complained of chest pain or a breathing complaint at the point of dispatch [14]. The percentage of AMIs significantly increased for patients aged 35 years and older and varied significantly by sex, dispatch level, and chief complaint.
The American Heart Association (AHA) and American College of Cardiology (ACC) recommend that emergency medical dispatchers prompt patients with nontraumatic chest pain to take aspirin if they have no contraindications while awaiting EMS arrival [15, 16]. This recommendation is based on extrapolation from data showing that patients who take aspirin before hospital arrival are less likely to die, and it is likely quite safe [17].
The 12‐lead electrocardiogram
The 12‐lead ECG remains the quickest method of detecting myocardial ischemia or infarction. Although ECGs have been used to diagnose ACS since 1932, the technology has now advanced to the point that a prehospital ECG can be done quickly and accurately and can be sent wirelessly to the receiving hospital at a relatively low cost. Additional benefit can be gained by having the prehospital ECG become the first of a series of ECGs, increasing the sensitivity of diagnosis of coronary syndromes [18].
Performing a prehospital ECG on a patient exhibiting signs and symptoms of ACS is a Class I AHA/ACC recommendation [15, 16]. This recommendation is based on evidence demonstrating that, despite minimal increased time spent on scene for patients receiving ECGs, the time to definitive treatment for ST‐elevation myocardial infarction (STEMI) with fibrinolysis or percutaneous coronary intervention (PCI) is shortened overall, with