Acute coronary syndrome (ACS) represents a spectrum of diseases resulting from insufficient blood flow through the coronary arteries culminating in a wide range of presentations.
Rapid identification of ST segment elevation myocardial infarction (STEMI) to facilitate timely reperfusion strategies is the primary goal in out-of-hospital management. Consider ACP intercept for ECG acquisition and interpretation if not available at the scene.
Antiplatelet therapy should be initiated as early as possible in all patients with suspected coronary ischemia.
Reduction of myocardial oxygen demand should be accomplished wherever and whenever possible (e.g., management of nausea, pain, and limiting patient exertion).
ACS exists on a spectrum, from angina through to STEMI:
Angina is pain resulting from a temporary increase in myocardial oxygen demand. This may be the result of reduced blood flow in the coronary arteries due to arterial narrowing, or spasm in the arterial wall.
Non-ST segment elevation myocardial infarction (NSTEMI) is the result of an incomplete occlusion of a coronary artery, either by a thrombus alone or in concert with vasospasm. ECGs generally show ST segment depression or T wave inversion, though transient ST segment elevation may also be observed.
STEMI occurs when a coronary artery is completely occluded by a thrombus. The diagnosis is dependent on ST segment elevation in two or more anatomically contiguous leads.
Common presentations include chest pain, "heaviness", or discomfort associated with shortness of breath, nausea, and/or diaphoresis. Be aware that although these are common findings, certain populations – in particular, women, the elderly, those with a history of diabetes, and younger individuals – may present differently. Atypical ACS presentations can include weakness or fatigue, syncope/presyncope, abdominal pain, and nausea.
The presence of palpable chest wall pain does not exclude ischemic origins. Paramedics and EMRs/FRs should maintain a high suspicion of ischemic-origin pain in cases of chest pain without a clear history of trauma.
Patients presenting with symptoms consistent with ACS should be managed as such, regardless of ECG findings, up to and including a clinical pathway selection.
Contraindications to ASA therapy include known hypersensitivity or a recent history of upper or lower gastrointestinal bleeding. Patients on oral anticoagulant therapies are often told by their physician to avoid ASA. In the setting of suspected or known ACS, the antiplatelet activity of ASA is of more importance than the temporary rise in INR. Consult with CliniCall if unsure.
First Responder (FR) Interventions
Keep the patient warm and protect from further heat loss
Place the patient in a position of comfort, as permitted by clinical condition; in general, limit patient movement
Kawakami S, et al. Time to reperfusion in ST-segment elevation myocardial infarction patients with vs. without pre-hospital mobile telemedicine 12-lead electrocardiogram transmission. 2016. [Link]
Welsford M, et al. Part 5: Acute coronary syndromes: 2015 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. 2015. [Link]