Acute Coronary Syndrome: Emergency Medical Services

By Justin Poole, MD | Medically reviewed by Eileen Johnson, RN on September 20, 2024

ACLS Certification Association videos have been peer-reviewed for medical accuracy by the ACA medical review board.

Emergency Medical Services
Oxygen
Aspirin
Nitroglycerine
Opiates
Assessment and Immediate Treatment
Summary

Article at a Glance

EMS may perform several interventions in the pre-hospital setting, such as obtaining an ECG and monitoring vital signs, as well as supporting the patient’s airway, breathing, and circulation.
EMS personnel should be prepared to provide CPR and defibrillate if the patient goes into cardiac arrest.
EMS personnel may administer several medications prior to hospital arrival, including morphine, oxygen, nitroglycerin, and aspirin.

Emergency Medical Services

Acute Coronary Syndrome Algorithm - flow chart.

Acute Coronary Syndromes Algorithm

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The second link in the STEMI Chain of Survival pertains to the actions of EMS providers. They perform rapid diagnosis, treatment, initial stabilization and transport of patients to a capable facility.

They support the patient’s airway, breathing, and circulation. They monitor the patient’s vital signs and obtain a 12-lead ECG. EMS may need to perform CPR and rapid defibrillation in patients experiencing cardiac arrest.¹

STEMI Chain of Survival

Oxygen

Initial pre-hospital therapies include oxygenation and ventilatory support when necessary. Oxygen supplementation is titrated to maintain an oxygen saturation of 94% and above. That is especially important when the patient shows signs of heart failure, respiratory distress, low oxygen saturation (less than 94%), or if arterial oxygen saturation is unknown.

Aspirin

Thrombus formation is a common pathophysiologic ACS effect. It causes significantly diminished perfusion to certain portions of the myocardium. Aspirin is an inhibitor of thromboxane a2 production, preventing thrombus formation.

To stabilize these patients, providers administer aspirin 160 – 325 mg to inhibit platelet function and prevent coronary occlusion. Aspirin suppositories are available if the patient cannot chew.

Providers must question patients about the presence of comorbidities that are contraindications for aspirin therapy, such as blood dyscrasias and gastrointestinal bleeding.

Nonsteroidal anti-inflammatory drugs are contraindicated in ACS patients. For example, COX-2 selective drugs (Vioxx, Celebrex) increase the risk of mortality, reinfarction, hypertension, heart failure, and myocardial rupture.

Aspirin has antiplatelet effects and is continued indefinitely after an acute coronary syndrome.

Nitroglycerine

Nitroglycerine improves myocardial perfusion by dilating arteries and veins, reducing ventricle preload and lessening the burden on the heart afflicted with ACS. It also reduces chest pain or discomfort, reducing the patient’s metabolic demand.

Nitroglycerin is used with caution in patients with inferior wall myocardial infarction or right ventricular infarction.² It may induce hypotension, bradycardia, or tachycardia.

Its effect is potentiated with concomitant use of sildenafil (Viagra) that can induce severe hypotension which doesn’t respond to vasopressor treatment. Providers must question patients regarding erectile dysfunction medication usage.

Nitroglycerin vasodilates the blood vessels, which helps to relieve chest pain.

Opiates

Morphine relieves chest pain and anxiety. Anxiety worsens ACS symptoms because it increases the patient’s metabolic demands.³ Its vasodilatory effects reduce left ventricular preload and left ventricular afterload. Opiates reduce myocardial oxygen demand and catecholamine release and help redistribute blood volume in patients with acute pulmonary edema.

Pre-hospital ACS Therapies

Assessment and Immediate Treatment

The third link in the STEMI chain of survival corresponds to the immediate assessment and treatment in the emergency department (ED). The patient’s first 10 minutes in the ED are crucial.

EMS responders should promptly report their findings and any interventions provided to the ED team. The team obtains vital signs, hooks the patient up to a cardiac monitor, checks the patient’s oxygen saturation, and establishes intravenous access if not yet performed by the EMS team.

Next, they review and perform a targeted clinical history and physical exam. The ED team also completes the fibrinolytic therapy checklist, asking appropriate questions to determine if the patient is a candidate for fibrinolytic therapy. Providers should obtain all other valuable information such as bloodwork (cardiac markers, electrolytes, complete blood count, coagulation studies).

Elevated cardiac troponins levels may indicate a myocardial injury.

Providers should obtain a chest X-ray within the first half hour. If not done in the pre-hospital setting, the ED team must provide oxygen supplementation, aspirin, nitroglycerine, morphine, and any other necessary treatments, ensuring there are no therapy contraindications.

Summary

In the pre-hospital setting, EMS are responsible for a patient’s ACS treatment. They must monitor vitals, obtain an ECG, and support the patient’s breathing and airways. EMS should be ready to administer CPR and an early AED if necessary. EMS may administer morphine, oxygen, nitroglycerin, and aspirin to ACS patients.

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Editorial Sources

ACLS Certification Association (ACA) uses only high-quality medical resources and peer-reviewed studies to support the facts within our articles. Explore our editorial process to learn how our content reflects clinical accuracy and the latest best practices in medicine. As an ACA Authorized Training Center, all content is reviewed for medical accuracy by the ACA Medical Review Board.

1. Sudden Cardiac Arrest Foundation. The Chain of Survival.

2. Laurie Robichaud, Dave Ross, Marie-Hélène Proulx, Sébastien Légaré, Charlene Vacon, Xiaoqing Xue, Eli Segal. Prehospital Nitroglycerin Safety in Inferior ST Elevation Myocardial Infarction. National Library of Medicine. 2015.

3. Christopher M. Celano, MD, Daniel J. Daunis, MD, Hermioni N. Lokko, MD, Kirsti A. Campbell, BS, and Jeff C. Huffman, MD. Anxiety disorders and cardiovascular disease. National Library of Medicine. 2017.