T wave

• The T wave is the positive deflection after each QRS complex.
• It represents ventricular repolarisation.

Characteristics of the normal T wave

• Upright in all leads except aVR and V1
• Amplitude < 5mm in limb leads, < 15mm in precordial leads
• Duration (see QT interval)

T wave abnormalities

• Hyperacute T waves
• Inverted T waves
• Biphasic T waves
• ‘Camel Hump’ T waves
• Flattened T waves

Peaked T waves

Tall, narrow, symmetrically peaked T-waves are characteristically seen in hyperkalaemia.

Hyperacute T waves

Broad, asymmetrically peaked or ‘hyperacute’ T-waves are seen in the early stages of ST-elevation MI (STEMI) and often precede the appearance of ST elevation and Q waves. They are also seen with Prinzmetal angina.

Loss of precordial T-wave balance

Loss of precordial T-wave imbalance occurs when the upright T wave is larger than that in V6. This is a type of hyperacute T wave.

• The normal T wave in V1 is inverted. An upright T wave in V1 is considered abnormal — especially if it is tall (TTV1), and especially if it is new (NTTV1).
• This finding indicates a high likelihood of coronary artery disease, and when new implies acute ischemia.

Inverted T waves

Inverted T waves are seen in the following conditions:

• Normal finding in children
• Persistent juvenile T wave pattern
• Myocardial ischaemia and infarction
• Bundle branch block
• Ventricular hypertrophy (‘strain’ patterns)
• Pulmonary embolism
• Hypertrophic cardiomyopathy
• Raised intracranial pressure

T wave inversion in lead III is a normal variant. New T-wave inversion (compared with prior ECGs) is always abnormal. Pathological T wave inversion is usually symmetrical and deep (>3mm).

Paediatric T waves

Inverted T-waves in the right precordial leads (V1-3) are a normal finding in children, representing the dominance of right ventricular forces.

Persistent Juvenile T-wave Pattern

T-wave inversions in the right precordial leads may persist into adulthood and are most commonly seen in young Afro-Caribbean women. Persistent juvenile T-waves are asymmetric, shallow (<3mm) and usually limited to leads V1-3.

Myocardial Ischaemia and Infarction

T-wave inversions due to myocardial ischaemia or infarction occur in contiguous leads based on the anatomical location of the area of ischaemia/infarction:

• Inferior =  II, III, aVF
• Lateral =  I, aVL, V5-6
• Anterior =  V2-6

NOTE:

• Dynamic T-wave inversions are seen with acute myocardial ischaemia.
• Fixed T-wave inversions are seen following infarction, usually in association with pathological Q waves.

Bundle Branch Block

Left Bundle Branch Block

Left bundle branch block produces T-wave inversion in the lateral leads I, aVL and V5-6.

Right Bundle Branch Block

Right bundle branch block produces T-wave inversion in the right precordial leads V1-3.

Ventricular Hypertrophy

Left Ventricular Hypertrophy

Left ventricular hypertrophy produces T-wave inversion in the lateral leads I, aVL, V5-6 (left ventricular ‘strain’ pattern), with a similar morphology to that seen in LBBB.

Right Ventricular Hypertrophy

Right ventricular hypertrophy produces T-wave inversion in the right precordial leads V1-3 (right ventricular ‘strain’ pattern) and also the inferior leads (II, III, aVF).

Pulmonary Embolism

Acute right heart strain (e.g. secondary to massive pulmonary embolism) produces a similar pattern to RVH, with T-wave inversions in the right precordial (V1-3) and inferior (II, III, aVF) leads.

Pulmonary embolism may also produce T-wave inversion in lead III as part of the S_I Q_III T_III pattern (S wave in lead I, Q wave in lead III, T-wave inversion in lead III).

Hypertrophic Cardiomyopathy (HOCM)

HOCM is associated with deep T wave inversions in all the precordial leads.

Raised intracranial pressure

Events causing a sudden rise in ICP (e.g. subarachnoid haemorrhage) produce widespread deep T-wave inversions with a bizarre morphology.

Biphasic T waves

There are two main causes of biphasic T waves:

• Myocardial ischaemia
• Hypokalaemia

The two waves go in opposite directions:

• Ischaemic T waves go up then down
• Hypokalaemic T waves go down then up

Ischaemia

Hypokalaemia

Wellens’ Syndrome

Wellens’ syndrome is a pattern of inverted or biphasic T waves in V2-3 (in patients presenting with ischaemic chest pain) that is highly specific for critical stenosis of the left anterior descending artery.

There are two patterns of T-wave abnormality in Wellens’ syndrome:

• Type 1 Wellens’ T-waves are deeply and symmetrically inverted
• Type 2 Wellens’ T-waves are biphasic, with the initial deflection positive and the terminal deflection negative

Wellens’ Type 1

Wellens’ Type 2

‘Camel hump’ T waves

This is a term used by the great ECG lecturer and Emergency Physician Amal Mattu to describe T-waves that have a double peak or ‘camel hump’ appearance.

There are two causes for camel hump T waves:

• Prominent U waves fused to the end of the T wave, as seen in severe hypokalaemia
• Hidden P waves embedded in the T wave, as seen in sinus tachycardia and various types of heart block

Flattened T waves

Flattened T waves are a non-specific finding, but may represent ischaemia (if dynamic or in contiguous leads) or electrolyte abnormality, e.g. hypokalaemia (if generalised).

Ischaemia

Dynamic T-wave flattening due to anterior ischaemia (above). T waves return to normal once the ischaemia resolves (below).

Hypokalaemia

Note generalised T-wave flattening with prominent U waves in the anterior leads (V2 and V3).

 

Related Topics

• P wave
• Q wave
• R wave

Further Reading

• ECG BASICS — Waves, Intervals, Segments and Clinical Interpretation
• ECG CLINICAL CASES — Your favourite ECG’s placed in clinical context with a challenging Q&A approach
• ECG and Cardiology Eponymous Syndromes — Cheats guide to eponymous emancipation
• ECG Exam Template — a framework for the FACEM part 2 exam.
• ECG Reference Sites on the WEB — the best of the rest

Author Credits

References

• Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice. 6th Edition. Saunders Elsevier 2008.
• Wagner, GS. Marriott’s Practical Electrocardiography (11th edition), Lippincott Williams & Wilkins 2007.