I agree with the other contributors – you really need to research your area from the ground up. If I was tasked with this, I’d look at what an ECG is actually measuring, what the scales would be on the axes of the output graph (I’m guessing there’s a requirement for a graph-type output) and I’d look at the specifications of the sensors – what do they output? I’m guessing you may need to write an interface (or get a hold of an interface, possibly from the sensor manufacturer’s) – that might be a good place to start. Hope this helps.
