Is pain always present in every myocardial infarction (MI)?

Myocardial Infarction Can Occur Without Pain

Not every myocardial infarction is accompanied by pain; approximately one-third of myocardial infarctions present without chest pain, and these "silent" infarctions are associated with higher mortality rates. 1

Presentation of Myocardial Infarction

Classic Symptoms

• Chest discomfort/pain (typically described as pressure, tightness, or heaviness)
• Radiation to arm(s), neck, lower jaw, or epigastrium
• Shortness of breath
• Diaphoresis (sweating)
• Nausea or vomiting
• Lightheadedness

Atypical Presentations

Myocardial infarction without chest pain is more common in certain populations:

• Elderly patients (on average 7 years older than those with typical symptoms) 1
• Women (49% of painless MIs vs 38% of painful MIs) 1
• Diabetic patients (32.6% vs 25.4%) 1
• Patients with prior heart failure (26.4% vs 12.3%) 1

Clinical Significance of Silent Myocardial Infarction

The absence of chest pain in myocardial infarction has significant clinical implications:

1. Delayed Presentation: Patients without chest pain delay longer before seeking medical attention (mean 7.9 vs 5.3 hours) 1

2. Diagnostic Challenges: These patients are less likely to be diagnosed with MI at admission (22.2% vs 50.3%) 1

3. Suboptimal Treatment: Patients without chest pain are less likely to receive:

   • Reperfusion therapy (thrombolysis or primary angioplasty)
   • Aspirin
   • Beta-blockers
   • Heparin 1

4. Higher Mortality: Most critically, MI patients without chest pain have a significantly higher in-hospital mortality rate (23.3% vs 9.3%) 1

Alternative Presenting Symptoms

When chest pain is absent, myocardial infarction may present with:

• Dyspnea (shortness of breath)
• Fatigue or weakness
• Epigastric discomfort
• Nausea and vomiting
• Diaphoresis
• Syncope or near-syncope
• Confusion (especially in elderly patients)
• Stroke-like symptoms 2

Posterior Myocardial Infarction

Posterior MI deserves special mention as it often presents with atypical symptoms:

• Predominant shortness of breath rather than chest pain
• Pain that radiates to the back or between shoulder blades
• Epigastric discomfort that may be mistaken for indigestion 2

Clinical Implications

The high prevalence of painless myocardial infarction (33% of all MIs) highlights the importance of:

1. Maintaining High Clinical Suspicion: Especially in high-risk populations (elderly, women, diabetics)

2. Prompt ECG: The European Society of Cardiology recommends that a 12-lead ECG should be obtained and interpreted as soon as possible at the point of first medical contact 3

3. Additional Diagnostic Tools: When standard ECG is non-diagnostic, consider:

   • Additional ECG leads (V7-V9) for suspected posterior MI 3
   • Echocardiography to detect regional wall motion abnormalities 3

4. Public Education: Patients should be educated about the full spectrum of MI symptoms beyond chest pain, and instructed to call emergency services promptly when these symptoms occur 3

Conclusion

The absence of pain does not rule out myocardial infarction. In fact, painless MIs represent a particularly dangerous subset with higher mortality, likely due to delayed presentation and less aggressive treatment. Clinicians must maintain a high index of suspicion for MI even when classic chest pain is absent, particularly in high-risk populations.