11. T Wave Abnormalities

Introduction

The T wave is the most labile wave in the ECG. T wave changes including low-amplitude T waves and abnormally inverted T waves may be the result of many cardiac and non-cardiac conditions. The normal T wave is usually in the same direction as the QRS except in the right precordial leads (see V2 below). Also, the normal T wave is asymmetric with the first half moving more slowly than the second half. In the normal ECG (see below) the T wave is always upright in leads I, II, V3-6, and always inverted in lead aVR. The other leads are variable depending on the direction of the QRS and the age of the patient.

Differential Diagnosis of T Wave Inversion

• Q wave and non-Q wave MI (e.g., evolving anteroseptal MI):

  

• Myocardial ischemia
• Subacute or old pericarditis
• Myocarditis
• Myocardial contusion (from trauma)
• CNS disease causing long QT interval (especially subarrachnoid hemorrhage; see below):

  

• Idiopathic apical hypertrophy (a rare form of hypertrophic cardiomyopathy)
• Mitral valve prolapse
• Digoxin effect
• RVH and LVH with "strain" (see below: T wave inversion in leads aVL, V4-6 in LVH)