13:44 Apr 22, 2011 

I hope it is obvious to you, amasubbu, but IC is called 集積回路. Integration circuit, integrating circuit, and integrator (circuit) all refer to the same thing, 積分回路.

In your application of ECG, I would think that an integration circuit is used because the amount of current from a human body is minute and should be integrated over time to distinguish it from noise. There must be a switch across the C in the circuit in my link to discharge the C periodically.