Interpreting ECGs

Question 1

Identify the U wave, describe its characteristics, and explain its origin.

Answer 1

The U wave is a rounded, positive deflection that follows the T-wave. It is so low amplitude that it is not seen on the majority of ECGs, but where it is present, it is usually most obvious in the right-sided pericardial leads. Its height should be under 1.5mm and less than 25% of the T-wave. Its origin is unknown, but it may represent repolarisation of the His-Purkinje system and/or the papillary muscles.

Question 2

Inverted U waves may be seen in ischaemic heart disease and left _ _ _.

Answer 2

Left ventricular volume overload.

Question 3

Give a non-pathological cause of prominent U waves.

Answer 3

Exercise.

Question 4

Prominent U waves can be seen in intracranial haemorrhage. True or false?

Answer 4

True.

Question 5

Is this a normal or abnormal ECG? Why?

Answer 5

The diffuse, upwardly concave ST segment elevation indicates early repolarisation, which is a benign finding not associated with any symptoms. It is often seen in young healthy individuals.

Question 6

Is this early repolarisation or pericarditis? Explain why.

Answer 6

This is early repolarisation. As in pericarditis, there is diffusive, upwardly concave ST segment elevation, but unlike in pericarditis the amplitude of this elevation is over 4 times greater than the amplitude of the T wave.

Question 7

Describe these ECG changes and the pathology they indicate.

Answer 7

Acute pericarditis is characterised by diffuse ST segment elevation that is less than 25% of the T-wave in amplitude, PR depression (often subtle), and sometimes notching of the QRS.