Re: What is significance of amplitude of an Electrocardiograph

Hello Devidas!

What a great question, and as it turns out - there is some significance!

As an example, Atrial hypertrophy (associated with enlargement of the 
chambers of the heart) is most often diagnosed by reading and comparing 
peak levels in an ECG - not necessarily in terms of ABSOLUTE voltage 
measurements, but rather in a millimeter span of amplitude as recorded on 
the chart. This is more of a baseline approach to reading ECG plots 
(although in a properly calibrated system, this span most likely could be 
read in terms of a specific voltage measurement). Here is an example by 
way of an excerpt from a course in ECG/EKG interpretation from the 
University of Wisconsin Medical School:

1. LVH: (Left ventricular hypertrophy). Add the larger S wave of V1 or V2 
(not both), measure in mm, to the larger R wave of V5 or V6. If the sum is 
> 35mm, it meets "voltage criteria" for LVH. Also consider if R wave is > 
12mm in aVL.

"Measure in mm" along with "voltage criteria" is indicative of using a 
relative amplitude measurement in the determination of the LVH condition. 

The question that remains is: to what extent are amplitudes of ECG signals 
used in the diagnostic process? For a great tutorial on ECG/EKG 
interpretations, go through the online course yourself!  http://www.medsch.wisc.edu/e
cg/ecg.html

I hope this has been of some help and wish you all the best in your 
studies!

Best Regards,

Jeff