However, many features of the heart and its functioning can be ascertained by this test including, the hearts regularity, the state of the muscle itself in conditions such as angina (ischaemic changes), previous heart attacks (or an acute or ongoing heart attack in patients with chest pain at the time of doing an ECG), the thickness of the muscle walls and several other factors which are important in normal heart funtion.

Electrodes in the shape of sticky pads are applied to the chest wall and connected to a computer which interprets the electrical signal detected by the electrodes and produces either a monitor display or printout.

The number of electodes required vary but in a 12-lead ECG, 6 electrodes are placed onto the chest and a further 1 each onto each wrist and ankle.

This test is quick and painless. However, it is limited in that it can only show or reveal heart rhythm at the time of the test. If there is a history of palpitations or irregular heart beat, then a 24 hour ambulatory ECG is required.

This is when the patient has electodes applied to the chest, but carries on with their daily, normal activites, including going to work. A small box worn by the patient records data from the electodes for a period of approximately 24 hours and this is downloaded into a computer which analysis the data to produce the relevant details.

Another method used in hospitals is an exercise ECG or Treadmill test where the heart is tested while working harder than it would do at rest. This is a very useful method of detecting underlying heart disease. The patient is monitored in the same as as above but asked to walk or run on a treadmill so that the effects of exercise can be assessed.