Guide — Cardiac

Acute Coronary Syndrome (ACS) for Nurses

Acute coronary syndrome encompasses the spectrum of ischemic cardiac emergencies — from unstable angina through STEMI. Understanding ACS pathophysiology, recognition, and nursing priorities is foundational for cardiac and emergency care.

12 min read · Cardiac

Educational use only. ACS is a time-sensitive emergency. All assessment, treatment, and intervention decisions require licensed provider orders and institutional protocol guidance. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.

What Is Acute Coronary Syndrome?

Acute coronary syndrome (ACS) refers to a group of conditions caused by sudden reduction in coronary blood flow, resulting in myocardial ischemia. All three ACS types share a common mechanism — plaque disruption followed by thrombus formation — but differ in severity and ECG/lab findings.

The three ACS types exist on a continuum of coronary artery occlusion: from partial occlusion without myocardial damage (unstable angina) to partial occlusion with damage (NSTEMI) to complete occlusion with transmural infarction (STEMI).

The Three ACS Types

Unstable Angina (UA)

Definition: Chest pain at rest, new onset, or increasing in frequency/severity. No troponin elevation. No ST elevation.

Occlusion: Partial — plaque disruption with thrombus formation but no complete occlusion; no myocardial necrosis.

Urgency: Urgent — requires inpatient evaluation and risk stratification.

Non-ST Elevation MI (NSTEMI)

Definition: Chest pain with troponin elevation but no ST segment elevation on ECG. May show ST depression or T-wave inversion.

Occlusion: Partial to near-complete — myocardial necrosis present (troponin release) but subendocardial rather than transmural.

Urgency: Emergent — catheterization typically within 24–72 hours based on risk score.

ST-Elevation MI (STEMI)

Definition: Chest pain with ST elevation in ≥2 contiguous leads. Troponin rises. Complete coronary artery occlusion.

Occlusion: Complete — transmural ischemia leads to full-thickness myocardial necrosis without immediate reperfusion.

Urgency: Immediate emergency — door-to-balloon time goal ≤90 minutes (PCI) or ≤30 minutes (thrombolytics).

Pathophysiology

Plaque formationAtherosclerotic plaque accumulates in coronary artery wall, narrowing the lumen and reducing blood flow reserve.

Plaque disruptionPhysical stress, inflammation, or shear forces cause plaque rupture or erosion, exposing subendothelial collagen.

Platelet activationExposed collagen triggers platelet aggregation and thrombus formation at the disruption site.

Coronary occlusionThrombus partially or completely occludes the coronary artery, causing ischemia downstream.

Myocardial ischemia → necrosisProlonged ischemia (>20–30 min) causes irreversible cell death beginning in the subendocardium and progressing outward (wavefront phenomenon).

Risk Factors

Modifiable	Non-Modifiable
›Hypertension ›Hyperlipidemia / high LDL ›Diabetes mellitus ›Smoking and tobacco use ›Obesity / metabolic syndrome ›Sedentary lifestyle ›Cocaine or stimulant use ›Chronic kidney disease (contributing)	›Age (men >45, women >55) ›Male sex ›Family history of premature CAD (first-degree relative <55 M or <65 F) ›Personal history of prior MI or CAD ›Postmenopausal status (women)

Clinical Presentation

Finding	Description	Clinical Note
Chest pain / pressure	Substernal pressure, squeezing, heaviness, or tightness — often described as 'elephant on chest'	Classic presentation; may radiate to arm, jaw, back, or epigastrum
Radiation	Left arm, jaw, neck, back, or epigastrum	Right arm or bilateral arm radiation also reported
Diaphoresis	Sudden, profuse sweating	Highly suggestive of cardiac ischemia
Dyspnea	Shortness of breath at rest or with minimal exertion	Can be the primary symptom, especially in women and diabetics
Nausea / vomiting	Nausea often accompanies inferior MI (vagal response)	Inferior STEMI: right vagal nerve innervation → GI symptoms
Syncope / near-syncope	Loss of consciousness or lightheadedness from decreased CO	Hemodynamic compromise; assess immediately
Atypical presentation	Fatigue, jaw pain, back pain, indigestion — no classic chest pain	More common in women, elderly, and diabetics — do not dismiss

Nursing Priorities

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Immediate recognition and ECG: Obtain 12-lead ECG within 10 minutes of arrival for any chest pain complaint. ST elevation identifies STEMI — activate cath lab protocol immediately.

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IV access and labs: Establish large-bore IV access. Draw stat troponin, BMP, CBC, PT/INR, type and screen. Serial troponins every 3–6 hours.

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Oxygen and monitoring: Apply continuous cardiac monitoring. Oxygen only if SpO₂ <90% — routine oxygen does not improve outcomes and may be harmful in non-hypoxic MI.

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Medication administration per protocol: MONA protocol (evolving): Morphine (use cautiously), Oxygen (only if SpO₂ <90%), Nitroglycerin, Aspirin. P2Y12 inhibitor (clopidogrel/ticagrelor) per order.

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Activity restriction: Bed rest during acute phase. Reduce myocardial oxygen demand. Assist with all activities of daily living.

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Pain reassessment: Reassess chest pain every 5–15 minutes. Unrelieved pain suggests ongoing ischemia — report immediately.

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Hemodynamic monitoring: Monitor BP, HR, SpO₂, urine output, and signs of cardiogenic shock: hypotension, tachycardia, cool extremities, decreased LOC.

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Emotional support and patient education: ACS is terrifying for patients. Explain all procedures, keep family informed, address anxiety. Education begins after stabilization.

NCLEX Pearls

›STEMI requires immediate reperfusion — door-to-balloon goal is ≤90 minutes for PCI.
›UA has no troponin elevation; NSTEMI has troponin elevation — both lack ST elevation.
›12-lead ECG should be obtained within 10 minutes for any suspected ACS presentation.
›Women, elderly, and diabetics often present atypically — jaw pain, back pain, nausea without classic chest pressure.
›Routine oxygen in ACS is NOT indicated unless SpO₂ <90% — it may actually worsen outcomes in normoxic patients.
›Aspirin 325 mg (non-enteric coated, chewed) is the first medication given for suspected ACS.
›Inferior STEMI (II, III, aVF) frequently causes right ventricular involvement — avoid nitroglycerin if RV infarct suspected (can cause severe hypotension).
›Serial troponins are required — a single normal troponin does not rule out NSTEMI in early presentation.

Related Resources

STEMI vs NSTEMI GuideECG differences, troponin findings, treatment priorities, and nursing implications

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Chest Pain Assessment GuideOPQRST, red flags, cardiac vs non-cardiac pain, emergency response

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Cardiac Biomarkers GuideTroponin, CK-MB, BNP — lab trends and clinical interpretation

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ACS Comparison ChartStable angina, UA, NSTEMI, STEMI — ECG, troponins, occlusion, urgency

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STEMI Activation Criteria ReferenceECG criteria, contiguous leads, new LBBB, posterior MI clues

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Cardiac Medications ReferenceAdenosine, amiodarone, atropine, dopamine, epinephrine — ACLS medications

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Cardiac Marker Timeline ChartTroponin, CK-MB, and myoglobin — when each rises, peaks, and clears

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Telemetry Monitoring BasicsLead placement, artifact recognition, and alarm response for cardiac monitoring

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Antiarrhythmic Drug Classes ChartVaughan Williams Class I–IV — channel targets, agents, and indications

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Acute Heart Failure NGN Case StudyWork a decompensation case: six pounds in three days and can't lie flat

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Standards & sources

Fact-checked Jun 20, 2026

This page is written to align with American Heart Association (AHA) · American College of Cardiology (ACC) · AHA ACLS Guidelines. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →