T wave



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Overview
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).

General

 * Normally upright in leads 1 and 2 and in the chest leads over the left ventricle.

Precordial Leads

 * Lead V1 may have a positive, negative, or biphasic T wave.
 * The T wave in V1 may be inverted at any age (is more often inverted than upright) and the T in V2 can normally be inverted.
 * When the T in V1 is upright, it is almost never as tall as the T in V6.


 * In infants and young children precordial T waves may be inverted.
 * In adult males it is considered abnormal if the T waves are inverted as far to the left as lead V3.
 * In adult females the T in V3 may be shallowly inverted.

aVF

 * Normally upright in aVL and aVF if the QRS is > 5 mm tall but may be inverted if the R waves are smaller.
 * It is not uncommon to have an isolated negative T wave in lead III, aVL, or aVF. Cardiologists are often asked to consult pre-operativley on the patient with the isolated flipped T in lead III.

aVR

 * Normally inverted in aVR.

In The Presence of Conduction Delay

 * When a conduction abnormality (e.g., left bundle branch block,right bundle branch block, or a paced rhythm) is present, the T wave should be deflected opposite the terminal deflection of the QRS complex. This is known as appropriate T wave discordance.

Differential Diagnosis of Inverted or Negative T waves:

 * Coronary ischemia
 * Left ventricular hypertrophy
 * CNS disorder.

Notched

 * Notched in children and in adults with Pericarditis

Differential diagnosis of the sharp, tented or pointed T wave

 * Tall or "tented" symmetrical T waves may indicate hyperkalemia.
 * One of the earliest electrocardiographic finding of acute myocardial infarction is sometimes the hyperacute T wave, which can be distinguished from hyperkalemia by the broad base and slight asymmetry.
 * T waves can be sharply pointed in ischemia as well.

Height
The T wave is normally not taller than > 5 mm in any standard lead and not taller than > 10 mm in any precordial lead.

Differential diagnosis of the tall T wave:

 * Hyperkalemia
 * Left ventricular hypertrophy
 * Myocardial Ischemia
 * Myocardial infarction
 * Ventricular strain
 * Psychosis
 * Cerebrovascular accident (usually inverted, widely splayed, frequently in subarrachnoid hemorrhages)

Differential diagnosis of the short or flat T wave:

 * Coronary ischemia
 * Hypokalemia.
 * Obesity. This finding may reverse with weight loss

Additional resources

 * ECGpedia: Course for interpretation of ECG
 * The whole ECG - A basic ECG primer
 * 12-lead ECG library
 * Simulation tool to demonstrate and study the relation between the electric activity of the heart and the ECG
 * ECG information from Children's Hospital Heart Center, Seattle
 * ECG Challenge from the ACC D2B Initiative
 * National Heart, Lung, and Blood Institute, Diseases and Conditions Index
 * A history of electrocardiography
 * EKG Interpretations in infants and children