Schematic representation of normal ECG

In electrocardiography, the T wave represents the repolarization (or recovery) of the ventricles. The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period. The last half of the T wave is referred to as the relative refractory period (or vulnerable period). The T wave contains more information than the QT interval. The T wave can be described by its symmetry, skewness, slope of ascending and descending limbs, amplitude and subintervals like the T_peak–T_end interval.^[1]

In most leads, the T wave is positive. However, a negative T wave is normal in lead aVR. Lead V1 may have a positive, negative, or biphasic (positive followed by negative, or vice versa) T wave. In addition, it is not uncommon to have an isolated negative T wave in lead III, aVL, or aVF.

  Clinical significance

• T-wave inversion (negative T waves) can be a sign of coronary ischemia, Wellens' syndrome, left ventricular hypertrophy, or CNS disorder.
• A periodic beat-to-beat variation in the amplitude or shape of the T wave may be termed T wave alternans.
• Tall and narrow ("peaked" or "tented") symmetrical T waves may indicate hyperkalemia.^[2]
• Flat T waves (less than 1 mV in the limb leads and less than 2 mV in the precordial leads)^[3] may indicate coronary ischemia or hypokalemia^[3]
• The earliest electrocardiographic finding of ST-elevation MI (STEMI) acute myocardial infarction is sometimes the hyperacute T wave, which can be distinguished from hyperkalemia by the broad base and slight asymmetry. This may also be seen in Prinzmetal angina.
• When a bundle branch block is present, the T wave should be deflected opposite the terminal deflection of the QRS complex. This is known as appropriate T wave discordance.

  Frequency of inverted T-waves in precordial leads (lead V1 to V6) according to gender and age

Numbers from Lepeschkin E in ^[4]

  References