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9.4 Medical Emergencies: Myocardial Infarction (MONA)

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NCLEX-RN Registered Nurse

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1 Introduction

About the NCLEX-RN Exam Next Generation NCLEX (NGN) Clinical Judgment Measurement Model (NCJMM) How to Use This Course

2 Chapter 2: Management of Care

2.1 Legal Rights and Responsibilities 2.2 Advance Directives and Self-Determination 2.3 Informed Consent Protocols 2.4 Client Advocacy and Rights (HIPAA) 2.5 Assignment, Delegation, and Supervision 2.6 Five Rights of Delegation 2.7 Scope of Practice (RN vs LPN vs UAP) 2.8 Ethical Practice Principles

3 Chapter 3: Safety and Infection Prevention and Control

3.1 Standard Precautions and Hand Hygiene 3.2 Transmission-Based Precautions (Contact, Droplet, Airborne) 3.3 PPE Donning and Doffing Sequences 3.4 Fall Prevention and Restraints 3.5 Fire Safety (RACE/PASS) 3.6 Disaster Triage and Emergency Response

4 Chapter 4: Health Promotion and Maintenance

4.1 Growth and Development (Erikson/Piaget) 4.2 Developmental Stages: Infancy through Older Adult 4.3 Maternal and Newborn Care (Antepartum) 4.4 Intrapartum Care and Fetal Monitoring 4.5 Postpartum Care (BUBBLE-HE) 4.6 Health Screening Guidelines 4.7 Immunization Schedules

5 Chapter 5: Psychosocial Integrity

5.1 Therapeutic Communication Techniques 5.2 Non-Therapeutic Communication (What to Avoid) 5.3 Anxiety Disorders and Mental Health Concepts 5.4 Schizophrenia: Hallucinations and Delusions 5.5 Depression and Suicide Assessment 5.6 Substance Misuse and Withdrawal 5.7 Grief and End-of-Life Care

6 Chapter 6: Basic Care and Comfort

6.1 Mobility and Hazards of Immobility 6.2 Assistive Devices (Crutches, Canes, Walkers) 6.3 Nutrition and Diet Therapy 6.4 Enteral Nutrition (Tube Feeding) 6.5 Bowel Elimination and Ostomy Care 6.6 Urinary Elimination and Catheter Care

7 Chapter 7: Pharmacological and Parenteral Therapies

7.1 Medication Administration Rights 7.2 Medication Calculations 7.3 High-Alert Medications: Insulins 7.4 High-Alert Medications: Anticoagulants 7.5 High-Alert Medications: Opioids 7.6 High-Alert Medications: Digoxin and Electrolytes 7.7 IV Therapy and Complications 7.8 Blood Product Administration 7.9 Total Parenteral Nutrition (TPN)

8 Chapter 8: Reduction of Risk Potential

8.1 Laboratory Values: Hematology (CBC) 8.2 Laboratory Values: Metabolic Panel (BMP) 8.3 Laboratory Values: Coagulation Studies 8.4 Vital Signs and Trend Recognition 8.5 Perioperative Care (Pre-Op and Post-Op) 8.6 Nasogastric Tubes and Therapeutic Procedures

9 Chapter 9: Physiological Adaptation

9.1 Fluid Imbalances (Hypovolemia and Hypervolemia) 9.2 Arterial Blood Gases (ABGs) and Acid-Base Balance 9.3 Medical Emergencies: Stroke (CVA) 9.4 Medical Emergencies: Myocardial Infarction (MONA) 9.5 Diabetic Emergencies (Hypoglycemia and DKA) 9.6 Respiratory Conditions (COPD, Pneumonia) 9.7 Cardiac Conditions (Heart Failure) 9.8 Neurological Conditions (Seizures)

9.4 Medical Emergencies: Myocardial Infarction (MONA)

Key Takeaways Explain This Topic AI

MONA mnemonic: Morphine (if pain unrelieved), Oxygen (if SpO2 < 94%), Nitroglycerin, Aspirin (priority)

Classic MI symptoms: crushing substernal chest pain radiating to jaw/arm, diaphoresis, nausea, shortness of breath

Women and diabetics may present atypically with fatigue, back pain, or indigestion rather than chest pain

Troponin is the most specific cardiac biomarker; elevates 3-6 hours post-MI and remains elevated 10-14 days

  • 12-lead ECG should be obtained within 10 minutes; STEMI requires immediate reperfusion (PCI or thrombolytics)
  • Last updated: January 2026

Medical Emergencies: Myocardial Infarction

Myocardial infarction (MI), commonly called a heart attack, occurs when blood flow to part of the heart muscle is blocked, causing tissue death. Rapid intervention is critical - "Time is muscle."

  • Pathophysiology
  • Atherosclerotic plaque ruptures in coronary artery
  • Platelets aggregate at the rupture site
  • Thrombus (clot) forms, blocking blood flow
  • Cardiac muscle distal to blockage becomes ischemic
  • Without reperfusion, ischemia progresses to infarction (cell death)
  • Types of Myocardial Infarction
  • Type ECG Finding Treatment Priority
  • STEMI ST-segment elevation Emergent reperfusion (PCI < 90 min or thrombolytics < 30 min)
  • NSTEMI ST depression or T-wave inversion Medical management, possible PCI
  • Unstable Angina May be normal or show ST changes Medical management, risk stratification
  • Classic Signs and Symptoms

Typical Presentation:

  • Chest pain - Crushing, squeezing, pressure-like
  • Substernal location
  • Radiates to left arm, jaw, neck, back, or epigastrium
  • Not relieved by rest or nitroglycerin (distinguishes from angina)
  • Lasts longer than 20 minutes
  • Diaphoresis - Cold, clammy, profuse sweating
  • Nausea and vomiting
  • Shortness of breath
  • Anxiety - Feeling of impending doom
  • Pale, cool skin
  • Atypical Presentations

Important: Women, elderly, and diabetic patients often present WITHOUT classic chest pain!

Atypical Symptoms (More Common in Women/Diabetics):

  • Fatigue, weakness
  • Back pain
  • Jaw pain
  • Indigestion or epigastric discomfort
  • Shortness of breath without chest pain
  • Flu-like symptoms
  • Nausea only
  • MONA Protocol

The MONA mnemonic guides initial MI treatment:

  • M - Morphine
  • Dose: 2-4 mg IV; may repeat every 5-15 minutes
  • Purpose: Pain relief, reduces anxiety, decreases oxygen demand
  • Caution: Use only if pain not controlled by nitroglycerin
  • Monitor for respiratory depression, hypotension
  • Current guidelines recommend using with caution (may mask symptoms)
  • O - Oxygen
  • Indication: Administer if SpO2 < 94% or patient is in respiratory distress
  • Note: Routine oxygen is NOT recommended for normoxic patients
  • Start at 2-4 L/min via nasal cannula; titrate to maintain SpO2 > 94%
  • N - Nitroglycerin
  • Dose: 0.4 mg sublingual every 5 minutes x 3 doses maximum
  • Purpose: Vasodilation decreases preload and myocardial oxygen demand

Contraindications:

  • SBP < 90 mmHg
  • Severe bradycardia (< 50) or tachycardia (> 100)
  • Right ventricular infarction
  • Phosphodiesterase inhibitor use within 24-48 hours (sildenafil, tadalafil)
  • A - Aspirin
  • Dose: 162-325 mg chewed immediately
  • Purpose: Antiplatelet effect prevents further clot formation
  • Priority: Often considered the MOST important initial intervention
  • Chewing provides faster absorption than swallowing whole

Exam Tip: While MONA is the classic mnemonic, current guidelines prioritize Aspirin as the first medication given. Some sources use MOAN (Morphine, Oxygen, Aspirin, Nitroglycerin) to emphasize aspirin's priority.

  • Diagnostic Tests
  • 12-Lead ECG
  • Obtain within 10 minutes of arrival

STEMI shows ST-segment elevation in leads corresponding to affected area:

  • Leads II, III, aVF = Inferior MI
  • Leads V1-V4 = Anterior MI
  • Leads I, aVL, V5-V6 = Lateral MI
  • Cardiac Biomarkers
  • Marker Onset Peak Return to Normal
  • Troponin I/T 3-6 hours 12-24 hours 10-14 days
  • CK-MB 3-6 hours 12-24 hours 2-3 days
  • Myoglobin 1-2 hours 6-9 hours 24 hours

Troponin is the most specific marker for myocardial damage. Serial troponins are drawn at presentation and 3-6 hours later.

  • Reperfusion Therapy
  • Goal: Restore blood flow to save heart muscle
  • Percutaneous Coronary Intervention (PCI)
  • First-line treatment for STEMI
  • Catheter-based balloon angioplasty with stent placement
  • Door-to-balloon time goal: < 90 minutes
  • Preferred over thrombolytics when available
  • Thrombolytic Therapy
  • Used when PCI not available within 120 minutes
  • Door-to-needle time goal: < 30 minutes

Contraindications similar to stroke tPA:

  • Active bleeding
  • Recent surgery
  • History of hemorrhagic stroke
  • Uncontrolled hypertension
  • Nursing Care During Acute MI
  • Immediate Actions
  • Activate emergency response
  • Obtain 12-lead ECG within 10 minutes
  • Establish IV access
  • Administer aspirin (chewed)
  • Apply oxygen if indicated
  • Continuous cardiac monitoring
  • Draw cardiac biomarkers
  • Ongoing Monitoring
  • Vital signs every 5-15 minutes during acute phase
  • Continuous telemetry for arrhythmias
  • Pain assessment using 0-10 scale

Monitor for complications:

  • Arrhythmias (especially V-fib)
  • Heart failure
  • Cardiogenic shock
  • Mechanical complications (septal rupture, papillary muscle rupture)
  • Patient Education Post-MI
  • Cardiac rehabilitation
  • Medication adherence (aspirin, beta-blockers, statins, ACE inhibitors)
  • Lifestyle modifications (smoking cessation, diet, exercise)
  • When to seek emergency care
  • Complications of MI
  • Complication Timing Signs
  • Arrhythmias First 24-48 hours Irregular rhythm, palpitations
  • Heart Failure Days to weeks Crackles, JVD, edema
  • Cardiogenic Shock Hours to days Hypotension, cool skin, altered mental status
  • Pericarditis 2-3 days post-MI Friction rub, chest pain worse with breathing
  • Ventricular Rupture 3-5 days Sudden death, JVD, pulseless electrical activity
  • Key Points for the NCLEX
  • Aspirin is priority - chew 162-325 mg immediately
  • Troponin is the most specific cardiac biomarker
  • STEMI requires emergent reperfusion (PCI or thrombolytics)
  • Door-to-balloon time goal: < 90 minutes

Do NOT give nitroglycerin if:

  • SBP < 90 mmHg
  • Patient took phosphodiesterase inhibitor (Viagra) recently
  • Right ventricular infarction suspected
  • Women and diabetics may present atypically - maintain high suspicion
  • Most dangerous arrhythmia post-MI is ventricular fibrillation