- 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
- 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.
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).
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 SI QIII TIII 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:
The two waves go in opposite directions:
- Ischaemic T waves go up then down
- Hypokalaemic T waves go down then up
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
Dynamic T-wave flattening due to anterior ischaemia (above). T waves return to normal once the ischaemia resolves (below).
Note generalised T-wave flattening with prominent U waves in the anterior leads (V2 and V3).
- 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
- 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.