kittypp:
It cannot use monitor or plotter to show the heartbeat or heart rate?
Yes, it can, and very well - but not using the Arduino serial monitor. If you have Excel you can send the data direct using the PLX v2 macro. This will give you the live graphic display you are probably looking for - all for the price of a regular
Serial.print(amplitude);
command. No need to poof about with LEDs or LCDs. If you don't have Excel, now might be a good time to beg, borrow, or steal a copy. Tere are other similar methods.
You may find it more convenient to use a phone instead of a laptop. You can send the same serial data to Android via Bluetooth instead of cable, and get a graphic representation using Bluetooth Graphics Terminal, which is God's gift to the Arduino world.
Both methods also allow you to record the data directly.