What are the signs and symptoms of myocardial infarction (MI)?

Signs and Symptoms of Myocardial Infarction

The classic presentation of MI includes chest discomfort (pressure, tightness, heaviness) lasting at least 20 minutes, often radiating to the arms, jaw, neck, back, or epigastrium, accompanied by dyspnea, diaphoresis, nausea, or lightheadedness—but up to one-third of patients present without chest discomfort at all, and these atypical presentations carry significantly higher mortality. 1

Typical Presentation

Chest discomfort characteristics:

• Diffuse, non-localized pressure, tightness, heaviness, crushing, cramping, burning, or aching sensation in the chest 1
• Duration typically exceeds 20 minutes 1
• Not positional, not affected by movement of the region 1
• May occur at rest or with exertion 1

Radiation patterns:

• Arms (particularly left arm), back, neck, jaw, throat, or epigastrium 1, 2, 3
• Throat pain is a legitimate cardiac symptom requiring urgent evaluation 2

Associated symptoms:

• Dyspnea (shortness of breath) 1, 3
• Diaphoresis (sweating) 1, 3
• Nausea or vomiting 1, 3
• Lightheadedness or syncope 1, 3
• Weakness or fatigue 1, 3
• Palpitations 3

Atypical Presentations: The High-Risk Scenario

Critical recognition: One-third of confirmed MI patients present without chest discomfort, and these patients have 2.2 times higher in-hospital mortality (23.3% vs 9.3%) compared to those with chest pain. 1

Atypical symptoms include:

• Isolated dyspnea without chest pain (carries more than twice the risk of death compared to typical angina) 1
• Epigastric pain or indigestion-like discomfort 3, 4
• Isolated back pain 3, 4
• Head or neck pain 4
• Generalized weakness without chest symptoms 3, 5
• Mental status changes 3, 5

High-Risk Populations for Atypical Presentations

These groups require heightened suspicion even with minimal or atypical symptoms:

Women:

• More likely to present without chest discomfort 1
• More commonly experience nausea, back pain, dizziness, and palpitations 3
• Often 8-10 years older than male counterparts at presentation 3
• Delay longer before seeking care 1

Elderly patients (age >75):

• May present with generalized weakness, syncope, or mental status changes rather than chest pain 3, 5
• Higher prevalence of silent MI 1

Diabetic patients:

• Atypical presentations due to autonomic dysfunction 3, 5
• Higher likelihood of silent ischemia 1
• Diabetes is a stronger risk factor in women than men 3

Patients with prior heart failure:

• More likely to present without chest discomfort 1

Silent and Unrecognized MI

Up to half of all MIs may be clinically silent and unrecognized by the patient. 1 These events are only detected later by ECG changes, biomarker elevations, or cardiac imaging. 1

Critical Time-Dependent Features

Duration matters:

• Discomfort lasting more than 20 minutes is highly concerning for MI 1, 2
• Symptoms unimproved or worsening after 5 minutes warrant calling 9-1-1 1

Prodromal symptoms:

• Many patients experience warning symptoms (shortness of breath, dizziness, fatigue) before the acute event 4

Common Diagnostic Pitfalls to Avoid

Misattribution of symptoms:

• Symptoms are frequently misdiagnosed as gastrointestinal (indigestion, reflux), neurological, pulmonary, or musculoskeletal disorders 1, 6
• Epigastric pain must not be assumed to be acid-related without excluding cardiac causes 6

Patient delay factors:

• Patients expect dramatic, crushing chest pain and dismiss gradual onset of milder symptoms 1
• Symptoms attributed to chronic conditions (arthritis, influenza) 1
• Fear of embarrassment if symptoms are a "false alarm" 1
• Women often do not perceive themselves at risk 1

Clinical errors:

• Failing to obtain ECG in patients with epigastric pain, especially in high-risk populations 6
• Assuming all throat or jaw pain is non-cardiac 2
• Relying on response to nitroglycerin as diagnostic (relief does not confirm or exclude MI) 3

Immediate Action Protocol

Any patient with symptoms potentially representing ACS should:

• Call 9-1-1 immediately for ambulance transport (not driven by friends/family) 1
• Receive 12-lead ECG within 10 minutes of presentation 1, 2
• Have cardiac biomarkers (troponin) drawn immediately 1, 6
• Be placed on continuous cardiac monitoring with defibrillation capability 2, 6
• Receive aspirin 162-325 mg (chewed) unless contraindicated 1, 2