available PCI centers, coordinated programs with regional STEMI receiving centers can achieve remarkable door‐to‐balloon times, even when measuring from the first door (i.e., the door of the rural ED). Two reports from Minnesota show that excellent treatment times can be achieved. In the Minneapolis area, the median first door‐to‐balloon time was 95 minutes if the referring hospital was less than 60 miles from the PCI center and 120 minutes if the referring hospital was farther away [68]. In the Mayo Clinic STEMI system, patients were transferred from 28 regional hospitals up to 150 miles away from the PCI center. The median first door‐to‐balloon time for the transferred patients was 116 minutes [69].
Air medical evacuation of STEMI patients
A key to a successful regional STEMI system is ready access to air medical transport. Rapid patient transport by highly skilled teams available in medical helicopters can save significant time from the first door‐to‐balloon. Some air medical programs are working closely with referring hospitals and ground EMS systems to dispatch helicopters before arrival of a STEMI patient at a referring hospital [70]. In terms of quality improvement, a recent national assessment of quality programs in EMS showed that air medical agencies are more likely to track quality measures compared to fire‐based agencies [71].
Expanding the role of basic life support (BLS) clinicians
Many 9‐1‐1 prearrival instructions already direct callers to take aspirin if they have chest pain. Allowing BLS clinicians to administer aspirin, if not contraindicated and if permitted by EMS laws and regulations, seems the next logical step. One reason stated for the lack of aspirin administration to eligible ACS patients is the inability of BLS clinicians to administer it based on local protocols or regulations [72].
BLS clinicians can be taught to acquire and transmit 12‐lead ECGs. This approach may be particularly beneficial in rural areas, with scant ALS coverage and long transport times to definitive care. Using the 12‐lead ECG to triage STEMI patients to air transport from the scene may lead to improved cardiac care in rural areas and more efficient use of available resources [73].
Other common causes of chest discomfort
Although most of the available prehospital interventions for chest pain are focused on the identification and treatment of ischemic cardiac disease, the majority of EMS chest pain patients will have other causes for their symptoms, some of which are also immediate threats to life (Box 9.3). A chest pain protocol should focus on treatments that may benefit the ACS/STEMI patient while considering the effects of these treatments on other causes of chest pain.
Box 9.3 Causes of chest discomfort that are immediate life threats
Acute coronary syndrome
Pericardial tamponade
Pulmonary embolism
Tension pneumothorax
Thoracic aortic dissection
Aortic dissection
Acute aortic dissection classically causes sudden pain in the chest, sometimes radiating to the back. The dissection is caused by a tear in the intimal lining of the aorta with entry of high‐pressure blood into the wall of the aorta. The dissection propagates distally and sometimes proximally. If the dissection extends around the origin of a peripheral artery, then that vessel can be partially or completely occluded, creating a >15‐ to 20‐mmHg difference in blood pressures between patient arms. If the origin of a carotid or vertebral artery is occluded, then the patient may develop neurologic signs suggesting a stroke. Occlusion of a spinal artery from the aorta can cause acute paralysis of both legs. Most patients with dissection have long‐standing hypertension, but the problem can occur in younger patients with other conditions such as Marfan syndrome.
In the majority of cases of aortic dissection, the12‐lead ECG will be abnormal, but will not show ST‐segment elevation unless the origin of a coronary artery is occluded by the dissection [74]. Without imaging capability that exists in the hospital, EMS clinicians may suspect, but cannot identify, aortic dissection definitively [75, 76]. If aortic dissection is suspected, morphine can be used for pain control but aspirin should be avoided, since patients with acute aortic syndrome who receive antithrombotic agents such as aspirin or fibrinolytics are more likely to bleed [77].
Pericarditis
Individuals with pericarditis may present to EMS with ST‐segment elevation on an ECG that looks similar to an extensive myocardial infarction. Administration of fibrinolytics in this condition may be fatal because these patients can bleed into the pericardial sac, resulting in pericardial tamponade. Aspirin administration is somewhat less concerning because anti‐inflammatory medications are part of the recommended treatment.
Pneumothorax
A pneumothorax may cause chest pain, shortness of breath, hypoxia, and diaphoresis. Clinical signs may point more to this diagnosis than to acute myocardial infarction. EMS systems should have a separate protocol for management of a pneumothorax. Oxygen and morphine may help the patient. Nitroglycerin should be avoided because it can cause hypotension by further decreasing venous return if the patient is developing a tension pneumothorax. If a developing tension pneumothorax is evident, needle decompression is required.
Pulmonary Embolism
Pulmonary embolism is a great masquerader because its symptoms may be similar to those of other causes of chest pain and shortness of breath. Its presentation can easily be confused with myocardial infarction or anxiety. Treatment should focus on maximizing oxygenation to the patient. If pulmonary embolism is suspected, nitroglycerin should be avoided because it can cause significant hypotension. Administration of fibrinolytics may potentially benefit the patient, but it is preferable to delay administration until the patient has reached a hospital and undergone definitive diagnostic imaging.
Esophageal Perforation
A patient with a perforated esophagus may present with chest pain. A careful and focused history and examination will often help differentiate this condition from other causes of chest pain. Nitroglycerin should be avoided because it may cause significant hypotension, and fibrinolytics are contraindicated because of the need for immediate surgery.
Summary
Quality prehospital care of patients with chest pain can relieve discomfort and improve outcome. EMS systems should have the capability to perform prehospital 12‐lead ECGs, and regional protocols should focus on delivering patients with STEMI to PCI centers promptly. Prehospital activation of the cardiac catheterization laboratory is highly effective at shortening the time to definitive reperfusion treatment and should be encouraged.
References
1 1 Virani SS, Alonso A, Benjamin EJ, et al. Heart disease and stroke statistics‐2020 update: a report from the American Heart Association. Circulation. 2020; 141:e139–e596.
2 2 Moy E, Garcia MC, Bastian B, et al. Leading causes of death in nonmetropolitan
