ECG techniques and technologies.

The electrocardiogram (ECG) continues to be a critical component of the evaluation of patients who have signs and symptoms of emergency cardiac conditions. This tool is now approximately 100 years old and has been a standard in clinical practice for more than half a century. Application of new signal processing techniques and an expansion in the use of additional leads allows clinicians to extract more and more information from the cardiac electrical activity. An understanding of the technology inherent in the recording of ECGs allows one to more fully understand the benefits and limitation of electrocardiography.