What are the common symptoms of a posterior myocardial infarction (MI)?

Common Symptoms of Posterior Myocardial Infarction

Posterior myocardial infarction (PMI) often presents with atypical symptoms compared to other types of MI, including epigastric discomfort that may be mistaken for indigestion, nausea, vomiting, and dyspnea without prominent chest pain.

Clinical Presentation of Posterior MI

Posterior MI accounts for up to 7% of all ST-elevation myocardial infarctions (STEMIs) 1 and presents with a unique symptom profile that can make diagnosis challenging. Common symptoms include:

Primary Symptoms

• Epigastric discomfort or pain that may be confused with indigestion or heartburn 2
• Nausea and vomiting (more common than in anterior MI) 3
• Shortness of breath or dyspnea (may be the predominant symptom) 4
• Chest discomfort that may be less severe or atypical compared to other MI types 4
• Pain that may radiate to the back, between the shoulder blades (interscapular region) 4

Associated Symptoms

• Diaphoresis (sweating) 4
• Lightheadedness or dizziness 2
• Fatigue or unexplained weakness 2
• Autonomic nervous system activation (pallor, sweating) 4
• Anxiety or sense of impending doom 2

Diagnostic Challenges

Posterior MI is often underdiagnosed because:

1. The standard 12-lead ECG does not directly visualize the posterior wall of the left ventricle 5, 6
2. ECG changes may be subtle, showing ST depression in leads V1-V3 rather than the classic ST elevation 1
3. Additional posterior leads (V7-V9) are required for direct visualization but are often not routinely performed 1
4. Symptoms may be misattributed to gastrointestinal causes 4, 2

Special Considerations for High-Risk Groups

Elderly Patients

• More likely to present with atypical symptoms such as:
  • Confusion or altered mental status
  • Generalized weakness
  • Dyspnea without chest pain
  • Syncope 2, 7

Women

• Higher likelihood of:
  • Unusual fatigue
  • Sleep disturbances
  • Indigestion-like symptoms
  • Anxiety 2

Diabetic Patients

• May have minimal or atypical symptoms due to autonomic neuropathy
• Pain perception may be blunted 2

Clinical Implications

The recognition of posterior MI is critical because:

1. Delayed diagnosis leads to delayed reperfusion therapy
2. Proper diagnosis requires a high index of suspicion and use of posterior leads (V7-V9) 1
3. Early recognition and treatment significantly reduce morbidity and mortality 1

When evaluating patients with suspected acute coronary syndrome, particularly those with epigastric discomfort, nausea/vomiting, or dyspnea without typical chest pain, clinicians should maintain a high suspicion for posterior MI and consider obtaining posterior lead ECG recordings.