Mechanism of T-wave inversion on ECG

Mechanism of T-wave inversion

The T wave represents ventricular repolarization. Under normal conditions, repolarization proceeds from epicardium to endocardium, producing an upright T wave in most leads. T-wave inversion occurs when this normal repolarization sequence is altered.

Key mechanisms

1. Myocardial ischemia Ischemia delays repolarization in the affected myocardial region. The direction of repolarization reverses relative to normal myocardium, resulting in a negative T wave in leads facing the ischemic area.

• Typically symmetric and deep

• Seen in unstable angina, NSTEMI, post-ischemic states

2. Ventricular hypertrophy (strain pattern) Chronic pressure or volume overload alters myocardial action potentials, especially in the subendocardium. This causes discordant ST depression and T-wave inversion in leads overlying the hypertrophied ventricle.

• LVH: lateral leads (I, aVL, V5–V6)

• RVH: right precordial leads

3. Abnormal depolarization (secondary T-wave inversion) When QRS activation is abnormal, repolarization follows the altered depolarization vector, producing T-wave inversion that is secondary to the QRS abnormality.

Seen in:

• Bundle branch block

• Ventricular pacing

• Ventricular ectopy

4. Myocardial inflammation or injury In conditions like myocarditis or pericarditis (late phase), cellular injury alters membrane potentials, leading to repolarization abnormalities and T-wave inversion.

5. Neurogenic causes (cerebral T waves) Acute CNS events (e.g., subarachnoid hemorrhage, stroke) cause massive sympathetic discharge, leading to myocardial repolarization changes.

• Classically deep, symmetric T-wave inversions

• Often associated with QT prolongation

6. Electrolyte abnormalities Potassium disturbances affect phase 3 of the action potential.

• Hypokalemia: flattened or inverted T waves

• Hyperkalemia (late): T-wave inversion after initial tall peaked T waves

7. Normal variants • Persistent juvenile T-wave pattern (V1–V3)

• Isolated T-wave inversion in lead III

• Seen in young individuals and athletes

Clinical interpretation tip T-wave inversion must always be interpreted in clinical context, considering:

• Lead distribution

• QRS morphology (primary vs secondary)

• Symptoms and biomarkers

• Comparison with prior ECGs

Not all T-wave inversions indicate ischemia, but new, symmetric, deep inversions in contiguous leads are ischemic until proven otherwise.

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