T wave

Schematic representation of normal ECG

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

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).

Orientation of T waves

Normal Orientation

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.

1. 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.
2. 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.

Morphology of T waves

Shape

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

Cerebral T waves

Overview

In 1954 George Burch described T wave abnormalities as myocardial ischemia mimics in patients with a variety of acute cerebral insults. His classic paper published in May 1954 popularized the term cerebral T waves.

Examples

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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

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