Is lifeline actually a wave?
First of I have to clarify the question.
The word LifeLine has got more than one meaning.
See the link below for various reference to LifeLine
I hope your reference is towards ECG (If not, please respond to this post through the commenting system)
“The ECG works mostly by detecting and amplifying the tiny electrical changes on the skin that are caused when the heart muscle “depolarises” during each heart beat. At rest, each heart muscle cell has a charge across its outer wall, or cell membrane. Reducing this charge towards zero is called de-polarization, which activates the mechanisms in the cell that cause it to contract. During each heartbeat a healthy heart will have an orderly progression of a wave of depolarisation that is triggered by the cells in the sinoatrial node, spreads out through the atrium, passes through “intrinsic conduction pathways” and then spreads all over the ventricles. This is detected as tiny rises and falls in the voltage between two electrodes placed either side of the heart which is displayed as a wavy line either on a screen or on paper. This display indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle.” (Wikipedia)
The following links will be of help to learn more about ECG, its working and a little history
As such ECG cannot be treated as a wave. But the term wave is used to talk about the screen or print pattern obtained because of the graphical similarity with a wave pattern.
(Click the image on left for an animation of heart beats and the corresponding ECG obtained)
(I don’t think this as a complete answer. Anyone with better knowledge can add to this through comments)
DOWNLOAD the ebook “How ECG works” here