Which electrocardiogram (ECG) leads typically show hyperacute T waves in the context of an acute myocardial infarction (MI)?

Hyperacute T Waves on Electrocardiogram: Lead Localization and Clinical Significance

Hyperacute T waves typically appear in leads corresponding to the area of myocardial injury, most commonly in anterior leads (V2-V4), inferior leads (II, III, aVF), or lateral leads (I, aVL, V5-V6) depending on the location of the coronary occlusion. 1

Characteristics of Hyperacute T Waves

Hyperacute T waves represent one of the earliest ECG findings in acute myocardial infarction, often preceding ST-segment elevation. They have specific morphological features:

• Broad, asymmetric, and peaked T waves 1
• Prominent and symmetrical appearance 1
• Occur in at least two contiguous leads 1
• May be accompanied by increased R-wave amplitude and width (giant R-wave with S-wave diminution) 1
• Often progress to ST-segment elevation if serial ECGs are obtained 1

Lead Distribution Based on Coronary Territory

The location of hyperacute T waves corresponds to the affected coronary territory:

Anterior Wall Infarction (LAD occlusion)

• Most commonly seen in precordial leads V2-V4 1
• May extend to V1 and V5-V6 in extensive anterior infarctions
• Often accompanied by ST depression in inferior leads (reciprocal changes)

Inferior Wall Infarction (RCA or LCx occlusion)

• Appear in leads II, III, and aVF 1
• RCA occlusion typically shows greater ST elevation in lead III than lead II
• LCx occlusion often shows greater ST elevation in lead II than lead III

Lateral Wall Infarction (LCx or diagonal branch occlusion)

• Present in leads I, aVL, V5, and V6 1
• May be accompanied by reciprocal changes in inferior leads

Clinical Significance and Diagnostic Value

Hyperacute T waves are critically important to recognize as they:

• Represent the earliest ECG manifestation of acute myocardial infarction 1
• May be the only initial ECG finding before ST-segment elevation develops 1
• Require serial ECGs over very short intervals to assess for progression to STEMI 1
• Signal ongoing myocardial ischemia that requires urgent intervention

Differential Diagnosis

It's important to distinguish hyperacute T waves from other causes of prominent T waves:

• Hyperkalemia: typically produces narrow-based, peaked T waves rather than the broad-based hyperacute T waves of MI 2, 3
• Early repolarization: typically has concave ST elevation with notching at the J point
• Left ventricular hypertrophy: may have prominent T waves but usually with associated voltage criteria for LVH
• Cerebral events: including seizures, can rarely cause transient giant T waves 3

Common Pitfalls in Recognition

• Failure to obtain serial ECGs in patients with suspicious symptoms but non-diagnostic initial ECG
• Misinterpreting hyperacute T waves as normal variants, especially in young patients
• Overlooking subtle hyperacute T wave changes in patients with baseline T wave abnormalities
• Not recognizing that hyperacute T waves may be the only initial ECG finding in acute coronary occlusion 1

Clinical Approach

When hyperacute T waves are identified:

1. Obtain serial ECGs at short intervals to monitor for evolution to STEMI 1
2. Consider immediate cardiac biomarker testing
3. Maintain high clinical suspicion for acute coronary occlusion even in the absence of classic ST elevation
4. Consider emergent cardiac catheterization in appropriate clinical context, as hyperacute T waves may represent occlusion myocardial infarction 3

Early recognition of hyperacute T waves can significantly reduce time to reperfusion therapy and improve patient outcomes in acute myocardial infarction.