Differential Diagnosis for Early Repolarization vs STEMI on ECG

When differentiating between early repolarization and ST-Elevation Myocardial Infarction (STEMI) on an electrocardiogram (ECG), it's crucial to consider various diagnoses to ensure accurate and timely treatment. The differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis:
  • Early Repolarization: This is often considered the single most likely diagnosis in a patient with a typical ECG pattern of early repolarization, characterized by an elevated J-point, ST elevation, and a notched J-point in leads V2-V5, without reciprocal changes or Q-waves. The patient's clinical presentation, such as the absence of chest pain or other symptoms suggestive of acute coronary syndrome, supports this diagnosis.
• Other Likely Diagnoses:
  • STEMI: While early repolarization is a consideration, STEMI remains a critical diagnosis to rule out due to its high morbidity and mortality if not promptly treated. The presence of chest pain, diaphoresis, or other symptoms of acute coronary syndrome, along with ECG changes such as ST elevation in two or more contiguous leads, would make STEMI a likely diagnosis.
  • Pericarditis: This condition can mimic STEMI on ECG with diffuse ST elevation but is distinguished by the presence of PR depression, absence of reciprocal changes, and often, a history of chest pain that improves with sitting up and leaning forward.
• Do Not Miss Diagnoses:
  • Acute Coronary Syndrome (ACS) without STEMI: While the focus is on STEMI, other forms of ACS (e.g., non-STEMI, unstable angina) can present with subtle ECG changes and must not be overlooked, as they also require urgent evaluation and treatment.
  • Pulmonary Embolism: Although ECG findings are often non-specific, pulmonary embolism can cause ST elevation or depression, T-wave inversion, and right bundle branch block. A high index of suspicion is necessary, especially in patients with risk factors or symptoms suggestive of pulmonary embolism.
• Rare Diagnoses:
  • Brugada Syndrome: Characterized by a specific ECG pattern of ST elevation in leads V1-V3, which can be confused with early repolarization or STEMI. It's a rare but important diagnosis due to its association with sudden cardiac death.
  • Hypokalemia: Severe hypokalemia can cause ST elevation and T-wave flattening or inversion, mimicking early repolarization or STEMI. It's a rare cause but important to recognize due to its potential to cause significant cardiac arrhythmias.

Each of these diagnoses requires careful consideration of the patient's clinical presentation, ECG findings, and sometimes additional diagnostic testing to differentiate between them accurately.