T wave

Schematic representation of normal ECG

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List of terms related to T wave

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. The T waves were described as large,were similar to those seen in early myocardial isehemia, and were reported to revert to normal with improvement of the clinical condition,or changed to the pattern of any underlying heart disease present prior to the intracranial insult.

Etiological Theories

Originally the cause was thought to be preexisting coronary artery disease exacerbated by the physiological demands of the critical illness.

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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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