Why Hemoglobin Must Be Assessed Before STEMI Diagnosis and PCI

Chest pain and ST-segment abnormalities on ECG are among the most alarming findings in the emergency department. However, this case underscores an important principle: neither ST elevation nor widespread ST depression is synonymous with acute coronary occlusion. A thorough assessment of underlying physiology is essential to avoid misdiagnosis and inappropriate management.

Case Presentation

A man in his 70s with known peripheral arterial disease presented with chest discomfort, dyspnea, and several weeks of deteriorating functional status. He had recently been hospitalized abroad, but no documentation was available.

Initial Findings

ECG: Marked ST-segment depression in multiple leads with ST elevation in aVR

ST-depression in most of the leads and ST-elevation in lead AVR.

Laboratory results:

• Creatinine: 164 µmol/L (eGFR 35)

• Troponin T: 791–879 ng/L

• NT-proBNP: 10,867 ng/L

• Lactate: 5.2 mmol/L

• Hemoglobin: 4.1 g/dL

• Platelets: 866 ×10⁹/L

• Leukocytes: 134 ×10⁹/L (with blasts on smear)

• CRP: 143 mg/L

  
  

Echocardiography: Mild global hypokinesia with no focal wall motion abnormalities

Echocardiography: Apical 4-chamber view

Echcardiography: Apical 2-chamber view

Further hematologic evaluation confirmed acute myeloid leukemia.

Interpretation

The ECG pattern of diffuse ST depression with ST elevation in aVR immediately raised suspicion of left main coronary artery disease, consistent with ESC STEMI guidelines (2023). However, several clinical features pointed away from an acute coronary occlusion:

• Symptoms had been present for several weeks, not hours

• No focal ischemia on echocardiography

• Severe anemia providing a more plausible explanation for global oxygen supply–demand mismatch

  
  

With a hemoglobin level of 4.1 g/dL, the primary problem is not coronary flow. The myocardium receives insufficient oxygen regardless of perfusion pressure or the degree of anatomical stenosis. This leads to global myocardial ischemia without coronary obstruction.

Clinical Implications

This form of systemic supply–demand mismatch can mimic left main disease on ECG, yet the management is fundamentally different. If the anemia is overlooked and the patient is rushed for primary PCI, the consequences can be harmful.

Why PCI may be dangerous in this setting

Coronary angiography should be deferred in the presence of unexplained anemia. If the anemia is due to active bleeding, initiating dual antiplatelet therapy (DAPT) after PCI can worsen the bleeding significantly. At the same time, DAPT cannot be safely discontinued because of the substantial risk of stent thrombosis. Therefore, identifying the underlying cause of anemia is crucial before proceeding with invasive coronary evaluation.

The Role of Hemoglobin in Early STEMI Assessment

Although STEMI guidelines and common clinical algorithms do not explicitly emphasize hemoglobin assessment in the early evaluation of chest pain and ECG changes, Hb is an important variable before committing a patient to coronary angiography and potential PCI.

This assessment can often begin with clinical assessment, for instance, by evaluating skin color, perfusion, and overall circulatory status. When in doubt, a rapid arterial blood gas analysis can provide immediate Hb information.

Clinical judgment remains essential: hemoglobin evaluation should not delay urgent PCI in a truly time-critical STEMI, where treatment delays adversely affect prognosis. The key is distinguishing genuine coronary occlusion from systemic causes of ischemia.

Key Learning Points

1. Global ischemia is not always coronary in origin

Diffuse ST depression with ST elevation in aVR/V1 can result from systemic hypoxia, profound anemia, sepsis, or other states of reduced oxygen delivery.

2. Troponins must be interpreted in context

Elevated troponins are common in severe anemia, malignancy, and systemic illness, even without plaque rupture or coronary occlusion.

3. Symptom duration provides invaluable clues

Prolonged symptoms over days to weeks are rarely consistent with acute coronary thrombosis.

4. Hemoglobin should be assessed early

Not necessarily before ECG interpretation, but before committing the patient to PCI and initiating DAPT.

5. Think broadly when global ischemia appears on ECG

The ECG alone does not make the diagnosis. Always integrate the full clinical picture.

Conclusion

This case illustrates the importance of interpreting ECG findings within the broader clinical context. Recognizing conditions that cause severe supply–demand mismatch can prevent unnecessary catheterization lab activation and avoid potentially harmful treatments.

Hemoglobin is an often undervalued, yet critically important, parameter in the acute evaluation of chest pain and suspected ischemia.