The T Wave

In this article, we discuss the meaning of the T wave in the ECG and its normal parameters including amplitude, morphology, and axis. Additionally will mention causes that can lead to abnormalities of these parameters.

Introduction

The T wave

• Represents the final phase of ventricular repolarization.

• Is the result of the restored negative electrical charges inside the ventricular cells.

• Is seen as the first positive wave following the QRS complex.

The T Wave Amplitude

• Limb leads - Normally less than 0.5 mV (5 mm). The tallest T wave in the limb leads can be seen in lead II.

• Precordial leads - Less than 1.0mV (10 mm) and usually 0.6mV (6mm) on average. The tallest T wave in the precordial leads is seen in v2 - v3 and may reach 1.0mV (10 mm) or more.

The T wave Morphology

Quantitative descriptors

• Low: amplitude less than 10% of R wave.

• Flat: peak T wave amplitude between 0.1mV (1 mm) and -0.1 mV (1 mm) in leads I, II, aVL, v4-v6.

• Inverted : T wave amplitude -0.1mV (-1mm) to -0.5 mV (-5 mm).

• Deep negative : T wave amplitude -0.5 mV (-5mm) to -1.0 mV (-10 mm).

• Giant negative: more negative than -1.0 mV (-10mm), seen in HOCM, NSTEMI, intracerebral hemorrhage).

Qualitative descriptors

Peaked T wave

Symmetrical T wave

Inverted T wave

Biphasic T Wave

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The T Wave Axis

• The normal T wave vector is directed leftward, inferiorly, and anteriorly.

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Key Takeaway

• The T wave denotes repolarization of the ventricle with restored negative charges inside the cells.

• The T wave size should be less than 10 mv (10mm) in precordial leads and less than 5 mv (5mm) in the limb leads.

• The T wave has different morphologies including symmetrical, peaked, biphasic, or inverted.

• Several causes can lead to a change in the normal morphology of the T wave.

• The T wave is upright in leads I, II, v3-v6, always inverted in lead aVR and upright or inverted in leads v1, v2, aVL, III, and aVF.

References

• Rautaharju PM, Surawicz B, Gettes LS. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram part IV. J Am Coll Cardiol. 2009;53:982-991.

• Surawicz, B., Knilans, T. K., & Chou, T.-C. (2008). Chou's electrocardiography in clinical practice: Adult and pediatric. Philadelphia, PA: Saunders/Elsevier.

• Zipes D, Libby P, Bonow R et.al, Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine 11th edition, 2018.

• Somers MP, Brady WJ, Perron AD, Mattu A. The prominent T wave: electrocardiographic differential diagnosis. Am J Emerg Med. 2002 May;20(3):243-51.

• O’Keefe J, Hammill S, Freed M, The Complete Guide of ECGs 4th edition, 2016.
  
  
  

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