Acute Coronary Syndromes Algorithm

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Using the Acute Coronary Syndromes Algorithm for Managing the Patient

The Acute Coronary Syndromes Algorithm outlines the steps for assessment and management of a patient with ACS. The algorithm begins with the assessment of chest pain and whether it is indicative of ischemia. The assessment and management begin with the EMS responder outside of the hospital who can give oxygen, aspirin, nitroglycerin, and morphine (if needed for pain). An initial 12-lead ECG can also be obtained. Treatment and assessment continues when the patient arrives at the hospital, following the time sequences suggested in the algorithm. Serial cardiac markers (CK-MB, cardiac troponins) provide additional information and allow refined stratification and treatment recommendations.

Out-of-Hospital Care

Decision 1: Does the patient have chest discomfort suggestive of ischemia?

An affirmative answer starts the algorithm.

Assess and care for the patient using the primary and secondary surveys.

Prepare patient for hospital admission.

  1. Monitor and support ABCs (airway, breathing, and circulation).
    • Take vital signs.
    • Monitor rhythm.
    • Be prepared to administer CPR if the need arises. Watch for it.
    • Use a defibrillator if necessary.
  2. Think MONA: Administer oxygen, aspirin, nitroglycerin, and morphine, if needed.
  3. If possible, obtain a 12-lead ECG.
  4. Interpret or request an interpretation of the ECG.

    If ST elevation is present, transmit the results to the receiving hospital.

    Hospital personnel gather resources to respond to STEMI.

  5. Start filling out a fibrinolytic checklist.

In-Hospital Care

Within the first 10 minutes that the patient is in the Emergency Department (ED), work through the following:

  1. Check vital signs.
  2. Evaluate oxygen saturation.
  3. Establish IV access.
  4. Get or review a 12-lead ECG.
  5. Look for risk factors for ACS, cardiac history, signs and symptoms of heart failure by taking a brief, targeted history.
  6. Perform a physical exam.
  7. Complete a fibrinolytic checklist and check contraindication
  8. Obtain a portable x-ray (less than 30 minutes).

Begin general treatment in the ED:

  1. Start oxygen at 4 L/min and maintain oxygen saturation > 90%.
  2. If the patient did not take aspirin while with the EMS provider, give aspirin (160 to 325 mg).
  3. Administer nitroglycerin, either sublingual, spray, or IV.
  4. Give the patient morphine (IV) if pain is not relieved by nitroglycerin.

Decision 2: Classify the patient according to presentation of ST-segment.

The 12-lead ECG is at the heart of the decision pathway in the management of ischemic chest pain and is the only means of identifying STEMI.

Note:The ECG classification of ischemic syndromes is not meant to be exclusive.

STEMI (ST-segment elevation myocardial infarction) High-risk unstable angina (UA) or NSTEMI (non-ST-segment elevation myocardial infarction) Intermediate or low risk UA
Definition: ST segment elevation greater than 1 mm (0.1 mV) in 2 or more contiguous precordial leads or 2 or more adjacent limb leads


New or presumed new left bundle branch block


Ischemic ST-segment depression of 0.5 mm (0.5 mV) or greater


Dynamic T wave inversion with pain or discomfort

Transient ST elevation of 0.5 mm or greater for less than 20 minutes


Normal or non-diagnostic changes in ST segment or T wave that are inconclusive and require further risk stratification

Includes people with normal ECGs and those who have ST-segment deviation in either direction that is less than 0.5 mm or T wave inversion of 2 mm or 0.2 mV or less

Classification: INJURY Classification: ISCHEMIA Classification: NORMAL?

Management is based on the results of the ECG.

ECG shows ST-segment elevation.

Confirm how much time has passed since the onset of symptoms.

If less than 12 hours has elapsed, do the following:

Results of cardiac markers, chest x-ray, and laboratory studies should not delay reperfusion therapy unless there is a clinical reason.

Start adjunctive treatments for STEMI, as indicated:

If the patient is classified with NSTEMI or high-risk unstable angina, follow this section of the algorithm.

Decision 2: Classify the patient according to presentation of ST-segment.

ECG shows ST depression or dynamic T-wave inversion

Start adjunctive treatments for NSTEMI, as indicated:

If more than 12 hours has passed since the patient's onset of symptoms, do the following:

  1. Admit patient to the hospital
  2. Assess risk status

Continue ASA, heparin, and other therapies as indicated (ACE inhibitors, statins) for the high-risk patient characterized by:

Decision 2: Classify the patient according to presentation of ST-segment.

ECG shows normal ECG or nonspecific ST-T wave changes

Consider admitting the patient to hospital or to a monitored bed in ED