Percentage of Patients with Chest Pain in ED Who Have MI
Approximately 8-17% of patients presenting to the Emergency Department with chest pain have myocardial infarction (MI). 1
Epidemiology of Chest Pain in the ED
The prevalence of chest pain varies across different clinical settings, with the underlying cause differing significantly depending on where patients are evaluated:
Emergency Department: 45% of chest pain cases have cardiac origin 1
Ambulance Setting: Higher prevalence of cardiac causes (69%) 1
Primary Care Setting: Lower prevalence of cardiac causes (20%) 1
Diagnostic Challenges
The diagnosis of MI in chest pain patients presents several challenges:
- Only 30-40% of patients with acute chest pain who develop MI initially have ST-elevations on hospital admission ECG 2
- About one-third of patients with acute chest pain present with a normal ECG, yet 5-40% of these patients may have an evolving MI 2
- Among patients with normal ECGs and no evidence of ischemia, approximately 1.3% will subsequently be diagnosed with MI 3
- For patients with abnormal ECGs but no clear evidence of ischemia, about 3.6% will be diagnosed with MI 3
- For patients with ECGs questionable for ischemia, 14.6% will be diagnosed with MI 3
- For patients with ECGs showing definite ischemia, 54.2% will be diagnosed with MI 3
Risk Stratification
Risk stratification is essential for appropriate management:
High-Risk Features:
- Ongoing chest pain
- Ischemic ECG changes
- Positive troponin test
- Left ventricular failure
- Hemodynamic abnormalities 1
Low-Risk Features:
- Normal ECG
- Negative cardiac biomarkers
- No hemodynamic instability 4
Management Implications
The identification of MI among chest pain patients has important management implications:
- Patients with normal ECGs are at extremely low risk and may be candidates for outpatient evaluation 3
- Patients with chest pain and ST segment abnormalities suggestive of ischemia should be admitted for further evaluation 3
- Chest pain units have been shown to be safe, effective, and cost-saving for evaluating patients with chest pain 1
- Low-risk patients without evidence of MI may be safely discharged from the ED, though follow-up is essential 4
Common Pitfalls
- Missed MI: 2-4% of patients with evolving MI are inappropriately discharged from the ED due to normal ECG findings 1
- Gender Bias: Women are more likely than men to be inappropriately discharged 1
- Delayed Treatment: Self-medication with nitrates or antacids can delay proper diagnosis and treatment 1
- Reliance on ECG Alone: ECG has limited sensitivity for detecting MI, particularly in the early stages 2
Conclusion
While chest pain is a common presenting complaint in the ED (5-20% of all ED visits), only a minority of these patients (8-17%) will ultimately be diagnosed with MI. However, given the significant morbidity and mortality associated with missed MI, a systematic approach to evaluation is essential, including ECG, cardiac biomarkers, and appropriate risk stratification.