Acute Coronary Syndromes - NREMT AEMT Level

SECTION 1

Historical Context & Motivation

Coronary artery disease has been the leading cause of death worldwide for over a century, yet our understanding of the acute events that precipitate sudden cardiac death has evolved dramatically. The concept of acute coronary syndromes (ACS) emerged gradually as clinicians recognized that chest pain, electrocardiographic changes, and myocardial necrosis represented a continuum of ischemic injury rather than isolated disease entities. Before the modern era, physicians had limited tools to differentiate between reversible ischemia and irreversible infarction, and prehospital treatment was essentially nonexistent. The progression from bedside observation to 12-lead ECG interpretation and targeted pharmacotherapy in the field represents one of the most significant advances in emergency cardiovascular care.

1772 • Heberden Describes Angina Pectoris

William Heberden presented the first formal clinical description of angina pectoris to the Royal College of Physicians, cataloging the substernal chest pain, radiation to the left arm, and exertional pattern that remain hallmark features recognized by EMS providers today.

1912 • Herrick Links Coronary Thrombosis to MI

James B. Herrick published his landmark paper establishing that acute coronary thrombosis was the pathological basis of myocardial infarction, shifting the paradigm from viewing MI as an inevitably fatal event to one amenable to medical intervention.

1960s • Coronary Care Units Established

The creation of dedicated coronary care units with continuous cardiac monitoring and defibrillation capability reduced in-hospital MI mortality by nearly 30%, demonstrating the value of early rhythm surveillance and the concept of the golden hour of cardiac care.

1986 • Prehospital 12-Lead ECG Introduced

Pioneering EMS systems began transmitting prehospital 12-lead ECGs to receiving hospitals, enabling early identification of ST-elevation myocardial infarction (STEMI) and activation of cardiac catheterization laboratories before the patient arrived, fundamentally transforming the AEMT's role in the chain of survival.

2000s • ACS Spectrum Defined

Major cardiology organizations formalized the ACS continuum—unstable angina, NSTEMI, and STEMI—unifying pathophysiology and treatment algorithms that guide prehospital care today.

This historical arc reveals a central question for the modern AEMT: how can prehospital providers rapidly distinguish among the types of ACS, initiate time-critical interventions, and communicate findings to receiving facilities in a way that maximizes myocardial salvage? The answer lies in understanding the shared pathophysiology of coronary plaque rupture and the clinical features that place each patient on the ACS spectrum.

SECTION 2

Core Principles & Definitions

Acute coronary syndromes encompass a spectrum of clinical presentations caused by the abrupt reduction of coronary blood flow to the myocardium. The underlying mechanism in the vast majority of cases is the rupture or erosion of an atherosclerotic plaque within a coronary artery, triggering platelet aggregation and thrombus formation that partially or completely occludes the vessel lumen. The degree and duration of occlusion determine whether the patient experiences transient ischemia without myocardial necrosis (unstable angina), subendocardial injury with biomarker elevation (NSTEMI), or transmural infarction with characteristic ECG changes (STEMI). Recognizing where a patient falls on this continuum is critical because time-to-treatment directly correlates with the volume of viable myocardium that can be preserved.

Atherosclerotic Plaque Rupture

A vulnerable plaque with a thin fibrous cap ruptures, exposing the lipid-rich necrotic core to circulating blood. Platelets adhere, aggregate, and activate the coagulation cascade, forming a thrombus that occludes the coronary artery to varying degrees.

Ischemia–Injury–Infarction Continuum

Myocardial cells deprived of oxygen first become ischemic (reversible), then injured (potentially reversible), and finally infarcted (necrotic). The progression from ischemia to infarction occurs over minutes to hours, making early intervention paramount.

The ACS Triad

Unstable Angina (UA) presents with ischemic symptoms but no biomarker elevation. NSTEMI shows elevated troponin without ST elevation. STEMI features ST elevation indicating complete occlusion and transmural injury.

Time Is Myocardium

Every minute of coronary occlusion destroys more cardiac muscle. The AHA target of door-to-balloon time ≤ 90 minutes (or first medical contact to device ≤ 120 minutes) demands that AEMTs identify STEMI and activate the catheterization lab from the field.

Prehospital Role of the AEMT

AEMTs perform focused cardiac assessments, acquire and interpret 12-lead ECGs, administer aspirin and nitroglycerin, establish IV access, monitor for dysrhythmias, and transport to the most appropriate cardiac-capable facility.

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KEY TAKEAWAY

Think of a coronary artery as a major highway and an atherosclerotic plaque as road construction narrowing traffic to one lane. A plaque rupture is like a sudden multi-car pileup blocking the road entirely. If the blockage is partial and brief, downstream neighborhoods lose power temporarily (unstable angina). If the blockage is partial but prolonged, some homes suffer damage (NSTEMI). If the road is completely blocked for an extended period, entire blocks are destroyed (STEMI). The AEMT is the first responder dispatching road-clearing crews—the faster you identify the blockage type and call for the right resources, the more of the neighborhood you save.

SECTION 3

Visual Explanation — The ACS Spectrum

This diagram illustrates the ACS spectrum from a normal patent coronary artery through increasing degrees of occlusion. Note how the plaque and thrombus progressively narrow the lumen, with unstable angina representing partial obstruction, NSTEMI near-total occlusion with subendocardial necrosis, and STEMI complete transmural infarction. The severity bar at the bottom emphasizes the continuum nature of the disease.

As depicted in the diagram above, all three ACS presentations share a common pathological origin—the disrupted atherosclerotic plaque—but differ in the extent and persistence of coronary occlusion. In unstable angina, a non-occlusive thrombus forms over the ruptured plaque, transiently reducing myocardial perfusion but not causing cellular death. With NSTEMI, the thrombus is larger or more persistent, leading to subendocardial necrosis detectable through elevated cardiac troponin levels. In STEMI, complete thrombotic occlusion produces transmural ischemia that manifests as ST-segment elevation on the 12-lead ECG. For the AEMT, the visual distinction between these presentations guides both the urgency of transport and the activation of downstream resources such as the cardiac catheterization laboratory.

SECTION 4

Pathophysiology & Mechanism of Injury

The pathophysiology of ACS follows a well-characterized cascade that begins years before the acute event. Endothelial injury from risk factors such as hypertension, diabetes, smoking, and hyperlipidemia promotes the infiltration of low-density lipoproteins (LDL) into the arterial intima. Over time, macrophages engulf oxidized LDL to become foam cells, which accumulate to form a fatty streak. A fibrous cap composed of smooth muscle cells and collagen forms over the lipid core, creating the mature atherosclerotic plaque. The critical event in ACS occurs when this fibrous cap thins, fractures, or erodes, exposing highly thrombogenic subendothelial material to circulating platelets.

The Coagulation Cascade in ACS

Upon plaque rupture, exposed collagen and tissue factor activate the intrinsic and extrinsic coagulation pathways simultaneously. Platelets adhere to the disrupted endothelium via glycoprotein Ib receptors binding to von Willebrand factor, then activate and release thromboxane A₂ (TXA₂) and adenosine diphosphate (ADP), which recruit additional platelets. Aspirin exerts its therapeutic effect by irreversibly inhibiting cyclooxygenase-1 (COX-1), blocking TXA₂ synthesis and reducing further platelet aggregation. This is precisely why early aspirin administration is among the most important prehospital interventions in suspected ACS.

Oxygen Supply–Demand Mismatch

Myocardial ischemia fundamentally results from a mismatch between myocardial oxygen supply and demand. Oxygen supply depends on coronary blood flow (determined by perfusion pressure and coronary artery patency) and arterial oxygen content. Oxygen demand is driven by heart rate, contractility, wall tension (afterload), and preload. In ACS, supply is acutely reduced by the obstructing thrombus. Simultaneously, the stress response triggers catecholamine release that increases heart rate and contractility, paradoxically raising demand even as supply falls. This is why nitroglycerin—which dilates coronary arteries and reduces preload—can provide symptomatic relief by favorably shifting the supply–demand balance.

This flowchart traces the pathophysiological cascade from plaque rupture through thrombus formation to the three ACS presentations. Green boxes mark prehospital intervention points where the AEMT can interrupt the cascade: aspirin inhibits platelet aggregation, and nitroglycerin improves the oxygen supply–demand balance.

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Clinical Pearl

Remember that ACS can occur even without significant fixed stenosis. In some cases, plaque erosion on a minimally obstructive lesion triggers acute thrombus formation. This is why patients with seemingly "clean" coronary arteries on prior studies can still present with STEMI. The plaque doesn't need to be large—it needs to be vulnerable.

SECTION 5

Detailed Classification & Clinical Presentation

Differentiating among the three ACS presentations in the prehospital setting requires the integration of clinical history, symptom patterns, and—when available—12-lead ECG findings. While definitive differentiation between unstable angina and NSTEMI requires laboratory biomarker analysis that is beyond the AEMT scope, certain presentation features can help guide clinical decision-making and transport priority.

Feature	Unstable Angina	NSTEMI	STEMI
Chest Pain Character	Substernal pressure/squeezing, often at rest or with minimal exertion; new onset or worsening pattern	Similar to UA, may be more severe or prolonged (> 20 min); often unrelieved by rest	Severe, crushing substernal pain; classically described as "elephant sitting on chest"; often with diaphoresis
Radiation	Left arm, jaw, neck, back, epigastrium	Same distribution as UA	Same distribution; bilateral arm radiation increases specificity
Associated Symptoms	Dyspnea, nausea, anxiety	Dyspnea, nausea, diaphoresis, weakness	Diaphoresis, nausea/vomiting, sense of impending doom, syncope
12-Lead ECG	May be normal; ST depression; T-wave inversion	ST depression; T-wave inversion or flattening; may be non-diagnostic	ST elevation ≥ 1 mm in ≥ 2 contiguous leads; new LBBB may be equivalent
Cardiac Biomarkers	Troponin: Normal	Troponin: Elevated	Troponin: Elevated (often markedly)
Coronary Occlusion	Partial, transient	Near-total or intermittent total	Complete, persistent
Prehospital Priority	High — treat as ACS until ruled out	High — cannot distinguish from UA without troponin	HIGHEST — activate cath lab from field

Comparison of ACS presentations relevant to prehospital assessment

Atypical Presentations

A significant proportion of ACS patients—particularly women, elderly patients, and those with diabetes—present with atypical symptoms that may not include classic substernal chest pain. These patients may report isolated dyspnea, generalized weakness, syncope, epigastric discomfort mistaken for indigestion, or diffuse upper body pain without a clear cardiac quality. Diabetic patients with autonomic neuropathy may experience silent ischemia—myocardial ischemia without perceivable pain. The AEMT must maintain a high index of suspicion for ACS in any patient with relevant risk factors even when the presentation seems benign, because missing an ACS diagnosis in these populations carries significant morbidity and mortality.

Key ACS Risk Factors: Age > 45 (men) or > 55 (women), hypertension, diabetes mellitus, hyperlipidemia, smoking, family history of premature coronary disease, obesity, sedentary lifestyle, and prior ACS or PCI/CABG history.

SECTION 6

Worked Example — Prehospital ACS Management

Consider the following clinical scenario that an AEMT might encounter during a 911 response. We will walk through the systematic assessment and management steps that align with current AHA and NAEMSP guidelines.

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Scenario

You respond to a 58-year-old male complaining of "crushing" chest pain that began 45 minutes ago while watching television. He describes the pain as substernal, radiating to his left arm and jaw, rated 8/10, associated with diaphoresis and nausea. He has a history of hypertension and hyperlipidemia. Current medications include lisinopril 10 mg and atorvastatin 40 mg daily. He took one of his wife's nitroglycerin tablets without relief 10 minutes ago. Vitals: BP 148/92, HR 96, RR 22, SpO₂ 96% on room air.

Systematic ACS Management — AEMT Level

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Step 1 — Scene Safety & Primary Assessment

Ensure scene safety and perform a rapid primary assessment. The patient is alert and oriented, airway is patent, breathing is slightly tachypneic but adequate, and circulation shows strong radial pulses bilaterally. Skin is pale, cool, and diaphoretic. This presentation—a middle-aged male with cardiac risk factors, classic substernal chest pain with radiation, and associated autonomic symptoms—generates an extremely high clinical suspicion for ACS.

Priority: High acuity — initiate ACS protocol immediately
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Step 2 — Administer Aspirin (ASA)

Confirm no aspirin allergy and that the patient has not already taken aspirin today. Administer 324 mg of chewable aspirin (four 81 mg baby aspirin tablets). Instruct the patient to chew rather than swallow whole to accelerate absorption via the buccal mucosa. Aspirin inhibits COX-1, blocking thromboxane A₂-mediated platelet aggregation, which helps prevent thrombus propagation.

Intervention: ASA 324 mg PO (chewed)
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Step 3 — Establish IV Access & Cardiac Monitoring

Establish at least one large-bore IV (18- or 20-gauge) in the antecubital fossa and initiate a normal saline lock or slow drip. Apply continuous cardiac monitoring. ACS patients are at high risk for sudden dysrhythmias—particularly ventricular fibrillation during the first hour of symptom onset. Ensure the defibrillator is immediately accessible.

IV: 18G antecubital, NS lock; continuous cardiac monitor applied
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Step 4 — Acquire 12-Lead ECG

Acquire a 12-lead ECG and evaluate for ST-segment changes. In this scenario, the ECG reveals ST elevation of 3 mm in leads II, III, and aVF with reciprocal ST depression in leads I and aVL. This pattern is consistent with an acute inferior STEMI, typically caused by right coronary artery (RCA) occlusion. Transmit the ECG to the receiving facility per local protocol and verbally communicate STEMI identification.

Finding: Inferior STEMI — cath lab activation initiated
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Step 5 — Administer Nitroglycerin (with caution)

With an inferior STEMI, the AEMT must exercise caution with nitroglycerin because right ventricular involvement is common and NTG-induced preload reduction can cause severe hypotension. Check BP (currently 148/92—adequate) and confirm no phosphodiesterase inhibitor use (Viagra, Cialis) within 24–72 hours. Per local protocol, administer 0.4 mg NTG sublingual and reassess BP every 3–5 minutes before additional doses. If BP drops below 90 systolic, hold further NTG and consider a 250 mL NS fluid bolus.

Intervention: NTG 0.4 mg SL × 1 dose; monitor BP closely for RV involvement
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Step 6 — Transport Decision & Ongoing Care

Transport the patient directly to the nearest PCI-capable facility with cath lab activation already in progress. During transport, monitor continuous ECG for dysrhythmias, reassess vitals every 5 minutes, provide supplemental oxygen only if SpO₂ falls below 94% (current 96% — O₂ not indicated), position the patient in a position of comfort (semi-Fowler's), and be prepared for cardiac arrest. Document the timeline: symptom onset, first medical contact, aspirin and NTG administration times, and ECG findings.

Transport: Emergent to PCI-capable facility; FMC-to-device clock running

SECTION 7

Prehospital Medications — Benefits, Contraindications & Comparisons

The pharmacological toolkit available to the AEMT for ACS management is focused but powerful. Understanding not only the indications but also the contraindications and potential complications of each medication is essential for safe patient care. The two cornerstone medications—aspirin and nitroglycerin—address different aspects of the ACS pathophysiology and are complementary rather than redundant.

Parameter	Aspirin (ASA)	Nitroglycerin (NTG)
Mechanism	Irreversibly inhibits COX-1 → blocks TXA₂ → decreases platelet aggregation	Releases nitric oxide → smooth muscle relaxation → vasodilation (venous > arterial > coronary)
Dose	324 mg chewable PO (four 81 mg tablets)	0.4 mg (400 mcg) SL; may repeat × 3 doses at 3–5 min intervals
Onset of Action	≈ 5 minutes (chewed); 30 min (swallowed)	1–3 minutes SL
Contraindications	True aspirin allergy, active GI bleeding, recent hemorrhagic stroke	SBP < 90 mmHg, HR < 50 or > 100 (relative), phosphodiesterase inhibitor use (sildenafil within 24 hr, tadalafil within 48 hr), suspected right ventricular infarction
Key Side Effects	GI upset, bleeding risk (minor in single-dose prehospital context)	Hypotension, headache, reflex tachycardia
Primary Benefit	Reduces mortality by 23% when given early in ACS (ISIS-2 trial)	Symptom relief via preload reduction and coronary vasodilation

Comparison of AEMT-level ACS medications

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CLINICAL PRIORITY

If you can only give one medication in a suspected ACS, give aspirin. It is the only prehospital medication that directly reduces mortality in ACS. Nitroglycerin provides symptom relief but has not been shown to improve survival outcomes. Think of aspirin as the fire extinguisher attacking the source of the fire (thrombus), while nitroglycerin is the fan clearing the smoke (symptoms) so you can breathe easier while the fire department (cath lab) arrives.

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Right Ventricular Infarction Warning

In inferior STEMI (ST elevation in leads II, III, aVF), always consider right ventricular involvement. The right ventricle depends heavily on preload to maintain cardiac output. Nitroglycerin's venodilating effect reduces preload and can precipitate profound hypotension and cardiogenic shock in these patients. If available, obtain a right-sided ECG (V₄R) to evaluate for RV infarction before administering NTG. If SBP drops below 90 mmHg after NTG, place the patient supine, elevate the legs, and administer a 250–500 mL NS bolus.

SECTION 8

Connection to Advanced Cardiac Care

The AEMT's management of ACS represents the critical first link in a chain of increasingly sophisticated interventions. Understanding where your care fits within the broader treatment continuum helps you communicate more effectively with receiving facilities and appreciate why each prehospital action matters. As you advance in your career—potentially to the paramedic level—you will gain access to additional pharmacological and procedural tools that build upon the foundation covered in this lesson.

Intervention Domain	AEMT Level	Paramedic / Hospital Level
ECG Interpretation	Acquire 12-lead; identify STEMI by ST elevation criteria; transmit to receiving facility	Advanced rhythm interpretation; identification of STEMI equivalents (de Winter, Wellens); serial ECGs
Antiplatelet Therapy	Aspirin 324 mg chewable	Aspirin + P2Y₁₂ inhibitor (clopidogrel, ticagrelor); GP IIb/IIIa inhibitors in cath lab
Anti-Ischemic Therapy	Nitroglycerin SL	NTG drip (IV); morphine for refractory pain; beta-blockers; heparin/enoxaparin
Reperfusion	Cath lab activation from field; minimize scene time; bypass to PCI center	Fibrinolytics (when PCI not available within 120 min); primary PCI with stent placement
Dysrhythmia Management	Monitor; defibrillation for VF/pulseless VT; basic CPR	Antiarrhythmics (amiodarone, lidocaine); synchronized cardioversion; transcutaneous pacing

Scope of ACS management by provider level

The concept of first medical contact (FMC) to device time underscores why the AEMT's role is so consequential. Current AHA guidelines recommend that STEMI patients undergo percutaneous coronary intervention (PCI) within 120 minutes of first medical contact—or 90 minutes from hospital arrival (door-to-balloon). Every minute the AEMT saves through efficient assessment, early ECG acquisition, and prehospital cath lab activation directly translates to preserved myocardium. Studies demonstrate that each 30-minute delay in reperfusion is associated with a measurable increase in one-year mortality. This temporal relationship reinforces the axiom that in ACS care, time is myocardium.

SECTION 9

Practice Problems

Question 1: CONCEPTUAL

Explain the fundamental pathophysiological difference between unstable angina and NSTEMI. Both present similarly—what distinguishes them at the cellular level, and why can't this distinction be made in the prehospital setting?

Show answer

Both unstable angina and NSTEMI arise from atherosclerotic plaque disruption with partial coronary occlusion. The critical difference is that in NSTEMI, the duration and severity of ischemia are sufficient to cause myocardial cell death (necrosis), which releases intracellular proteins—particularly cardiac troponin—into the bloodstream. In unstable angina, ischemia is transient and no necrosis occurs, so troponin remains normal. Since troponin measurement requires laboratory analysis that is not available in the prehospital setting, AEMTs cannot definitively distinguish between these two conditions. This is why both are managed identically in the field under the umbrella of ACS, with the differentiation occurring after hospital arrival through serial biomarker testing.

Question 2: BASIC CALCULATION

Your unit makes first medical contact with a STEMI patient at 14:32. The AHA guideline recommends a first medical contact-to-device time of ≤ 120 minutes. What is the latest time by which the patient should undergo balloon inflation in the cath lab to meet this benchmark? If the nearest PCI-capable hospital has a 22-minute transport time, at what time must you depart the scene to allow 15 minutes for in-hospital processing before the balloon deadline?

Show answer

The FMC-to-device target of 120 minutes from a first medical contact time of 14:32 means the balloon must inflate by 16:32 at the latest. Working backward: 15 minutes for in-hospital processing means hospital arrival must occur by 16:17. Subtracting the 22-minute transport time, the ambulance must depart the scene by 15:55. This gives the AEMT approximately 83 minutes of scene time, but in practice, scene times should be minimized to well under 15–20 minutes. This calculation demonstrates why prehospital cath lab activation is so valuable—it allows the hospital to prepare simultaneously, reducing the in-hospital processing component.

Question 3: INTERMEDIATE

You respond to a 72-year-old female with diabetes who presents with acute onset nausea, diaphoresis, and epigastric discomfort but denies chest pain. Her 12-lead ECG shows ST depression in V1–V4 with T-wave inversions. Vital signs: BP 110/70, HR 88, RR 20, SpO₂ 94% on room air. Her medications include metformin, insulin, and lisinopril. Describe your assessment reasoning, suspected diagnosis, and management plan.

Show answer

This patient demonstrates a classic atypical ACS presentation. Elderly women with diabetes frequently present without typical chest pain due to autonomic neuropathy and altered pain perception. The combination of acute-onset nausea, diaphoresis, and epigastric discomfort in the context of diabetes (a major cardiac risk factor) should raise immediate ACS suspicion. The ECG showing ST depression and T-wave inversions in V1–V4 supports a diagnosis of either unstable angina or NSTEMI (indistinguishable prehospitally). Management includes: (1) aspirin 324 mg chewable; (2) nitroglycerin 0.4 mg SL (BP adequate at 110/70, but monitor closely as this is closer to the 90 mmHg threshold); (3) IV access with NS lock; (4) supplemental O₂ to maintain SpO₂ ≥ 94% (currently borderline—apply nasal cannula at 2–4 LPM); (5) continuous cardiac monitoring; (6) transport to cardiac-capable facility with early notification. Even without ST elevation, this patient requires urgent evaluation.

Question 4: APPLIED

You are transporting a 52-year-old male with a confirmed inferior STEMI (ST elevation in II, III, aVF). You administered NTG 0.4 mg SL five minutes ago. His BP has dropped from 134/82 to 78/50, HR has increased to 112, and he is now lightheaded and more diaphoretic. Describe the likely cause of this deterioration and outline your immediate management steps, including the rationale for each intervention.

Show answer

The most likely cause is right ventricular infarction concurrent with the inferior STEMI. The right coronary artery supplies both the inferior wall of the left ventricle and the right ventricle in most patients. RV infarction makes the right ventricle preload-dependent; nitroglycerin's venodilating effect reduced venous return, dramatically decreasing RV filling and consequently left ventricular output. Immediate management: (1) Discontinue all nitroglycerin—no further doses; (2) Place the patient supine and elevate his legs to 15–20° to augment venous return; (3) Administer a rapid 250–500 mL normal saline IV fluid bolus to restore preload; (4) Reassess BP every 2–3 minutes and repeat boluses as needed (judicious volumes to avoid pulmonary edema); (5) Continue transport to PCI-capable facility with urgent notification of hemodynamic deterioration; (6) Be prepared for cardiac arrest, as hemodynamic instability in STEMI significantly increases the risk of malignant dysrhythmias. This scenario illustrates why assessing for RV involvement before NTG administration is critical in inferior STEMI.

Question 5: CRITICAL THINKING

Your community has two hospitals: Hospital A is 8 minutes away but has no cardiac catheterization lab, while Hospital B is 35 minutes away and has 24/7 PCI capability. You have a 64-year-old male with an acute anterior STEMI (ST elevation in V1–V4) identified at 09:15. He is hemodynamically stable with BP 128/78, HR 92. Analyze the transport decision, considering AHA time benchmarks, the concept of first medical contact-to-device time, and potential risks of each option. What would you recommend and why?

Show answer

This question addresses one of the most consequential decisions in prehospital STEMI care: bypass to a PCI center versus nearest facility. The AHA recommends FMC-to-device time ≤ 120 minutes. Transporting to Hospital B (35 min) still leaves approximately 85 minutes for hospital processing and intervention—well within the benchmark. Transporting to Hospital A would require a door-in to door-out transfer, adding an estimated 30–60 minutes for assessment, stabilization, and inter-facility transport, likely pushing total reperfusion time well beyond 120 minutes. Hospital A could administer fibrinolytics (if available and within their protocol), but primary PCI is the preferred reperfusion strategy for STEMI with superior outcomes. For this hemodynamically stable anterior STEMI patient, the recommendation is to bypass Hospital A and transport directly to Hospital B. The AEMT should activate the cath lab during transport. If the patient were hemodynamically unstable or in cardiac arrest, the calculus might shift toward the closest facility for stabilization. This decision framework—weighing time-to-reperfusion against transport distance while considering patient stability—exemplifies the clinical judgment expected of EMS professionals.

SUMMARY

Lesson Summary — Acute Coronary Syndromes

Summary

Acute coronary syndromes represent a continuum of myocardial ischemic events caused by atherosclerotic plaque rupture and subsequent coronary thrombosis. The spectrum ranges from unstable angina (transient ischemia, no necrosis, normal troponin) through NSTEMI (subendocardial necrosis, elevated troponin, no ST elevation) to STEMI (transmural infarction, elevated troponin, ST elevation on 12-lead ECG). The degree of coronary occlusion—partial versus complete—determines presentation severity and guides the urgency of definitive treatment.

The AEMT plays a pivotal role by performing rapid assessment, acquiring a 12-lead ECG to identify STEMI, administering aspirin 324 mg (chewed) to inhibit platelet aggregation, carefully administering nitroglycerin 0.4 mg SL for symptom relief (while watching for right ventricular infarction contraindications), establishing IV access, and initiating cath lab activation for STEMI patients—all while maintaining continuous cardiac monitoring and preparing for potential cardiac arrest. Remember that atypical presentations (especially in women, elderly, and diabetic patients) require a high index of suspicion, and the guiding principle of ACS care is that time is myocardium—every minute of delay in reperfusion means more irreversible cardiac damage.