The usual waves in an electrocardiogram are P, QRS and T waves. P waves represents depolarisation of the atria. QRS represents the depolarisation of the ventricles. T wave is due to ventricular repolarisation. The repolarisation wave of the atria is not usually visible. If present, it is known as the Ta wave.
In addition to these certain waves occur in abnormal situations. A delta wave appears in pre-excitation while an epsilon wave appears in post excitation. Delta wave is a slurring of the initial portion of the QRS which resembles the Greek alphabet delta. Epsilon wave occurs at the end of the QRS and is seen in arrhythmogenic right ventricular dysplasia. An Osborn wave is visible at the end of the QRS in severe hypothermia. A normal variant known as J wave is also sometimes seen. U wave may be seen after the T wave. U wave becomes
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