T wave is a the positive deflection after each QRS complex. It represents ventricular repolarisation.
Characteristics of a normal T wave:
Upright in all leads except aVR and V1
Amplitude <5mm in limb leads, <15mm in precordial leads
Tall, narrow, symmetrical peaked T-waves are characteristically seen in hyperkalaemia
Broad, asymmetrically peaked
Seen in early stages of STEMI and often precede the appearance of ST elevation and Q waves
Also seen in Prinzmetal angina
Inverted T waves seen in the following conditions
Normal finding in children
Persistent juvenile T wave pattern
Myocardial ischemia and infarction
Ventricular hypertrophy (strain patterns)
Hypertrophic cardiomyopathy
Raised intracranial pressure
T wave inversion in lead III is a normal variant. New T wave inversion is always abnormal. Pathological T wave inversion is usually symmetrical and deep (>3mm).
T wave inversion in the lateral leads: lead I, aVL, V5 - 6
Right Bundle Branch Block
T wave inversion in the right precordial leads V1 - 3
Left ventricular hypertrophy produces T wave inversion in the lateral leads lead I, aVL, V5 - 6 (left ventricular 'strain' pattern) - similar to LBBB
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 produces a similar pattern to R ventricular hypertrophy
More commonly known - the S1Q3T3 pattern (S wave in lead I, Q wave in lead III, T wave inversion in lead III)
Hypertrophic Cardiomyopathy (HOCM)
Associated with deep T wave inversions in all precordial leads
Raised Intracranial Pressure
Widespread deep T wave inversions with bizarre morphology
2 Waves go in opposite direction
Myocardial ischemia: T waves go up then down
Hypokalaemia: T waves go down then up
May represent ischemia or electrolyte abnormality