The ECG provides a ‘snapshot’ in that it records the electrical activity of the heart for a few heartbeats whilst the recording is being made.
This has obvious limitations for heart rhythm problems that come and go in a ‘paroxysmal’ fashion rather than a sustained rhythm abnormality. If a patient is getting palpitation or dizzy spells every day, then a 24 hour tape recording will be able to show the cardiologist how the heart is behaving during symptoms (which should be recorded with the time on a diary card). If the symptoms are less frequent then a 48 hour, 5 day or one week monitor might be helpful. All test results should be treated with caution and interpreted in the context of a clinical assessment.