How could a myocardial infarction (MI) be missed if all standard tests for chest pain were performed?

Why a Myocardial Infarction Can Be Missed Despite Standard Testing

A myocardial infarction (MI) can be missed even with standard testing because up to one-third of MI patients present without chest pain and may have atypical symptoms that don't trigger the appropriate diagnostic pathway. 1

Atypical Presentations of MI

• Up to 33% of patients with confirmed MI present without chest pain, making diagnosis more challenging 1

• Patients without chest pain are more likely to be:

  • Older (average 7 years older than those with chest pain) 1
  • Women (49% vs 38% in those with chest pain) 1
  • Diabetic patients (32.6% vs 25.4%) 1
  • Those with prior heart failure (26.4% vs 12.3%) 1

• Common atypical symptoms include:

  • Unexplained dyspnea (particularly worrisome with more than twice the risk of death compared to typical angina) 2
  • Gradual onset of discomfort involving midsternal pressure or tightness 2
  • Other associated symptoms that increase in intensity 2

Limitations of Standard Testing

• Standard 12-lead ECG provides only a 10-second snapshot of cardiac activity 2

  • ST-segment elevation can be dynamic in early MI hours, with cycles of thrombotic occlusion and spontaneous reperfusion 2
  • If the ECG is taken during a period of resolving ST segments, it may not show diagnostic changes 2

• Cardiac biomarker limitations:

  • Troponin levels may not be elevated early in the course of MI 2
  • Serial testing (at 3 and 6 hours in ED, and at 6-10 hours in-hospital) is necessary to exclude myocardial injury 2
  • Point-of-care testing devices may be less sensitive than central laboratory analyzers 2

Risk of Missed Diagnosis

• Patients with MI but without chest pain experience:

  • Longer delays before hospital presentation (mean 7.9 vs 5.3 hours) 1
  • Less likely to be diagnosed with MI at admission (22.2% vs 50.3%) 1
  • Less likely to receive appropriate treatments like thrombolysis, angioplasty, aspirin, beta-blockers, or heparin 1
  • Higher in-hospital mortality (23.3% vs 9.3%) 1

• Approximately 0.9% of all AMI admissions represent missed diagnoses, where patients visited an ED with chest pain or cardiac conditions, were released, and subsequently admitted for AMI within 7 days 3

Improving Diagnosis

• Continuous ST-segment monitoring for 8-12 hours in combination with serial biomarker testing is more effective than a single ECG and troponin test 2

• Risk stratification tools can help identify high-risk patients:

  • TIMI, EDACS, and unstructured clinical impression by experienced physicians have shown the lowest rates of missed MI cases 4

• Healthcare providers should maintain high suspicion for MI in:

  • Women 2
  • Patients with diabetes 2
  • Older patients 2
  • Those with unexplained dyspnea 2
  • Those with history of heart failure or stroke 2
  • Patients with permanent pacemakers (may confound ECG interpretation) 2

• When coronary spasm is suspected but not documented, provocative testing may be considered 2

Key Takeaway

Even with standard testing, MIs can be missed due to atypical presentations, timing of tests relative to cardiac events, and limitations in test sensitivity. Continuous monitoring and serial testing significantly improve detection rates compared to single-point assessments typically performed in standard evaluations.