how can i send data from my sensor to Arduino - Xbee - Xbee - PC. help pls. thanks ;]
It depends on what information you want to send. If it is just the pulse rate then there is comparatively little data however if you want to send the whole waveform then you will have to send lots of samples per second. Xbee is not well suited for lots of continuous data. Have a look here for other techniques:-
http://www.arduino.cc/playground/Main/InterfacingWithHardware
Grumpy_Mike:
It depends on what information you want to send. If it is just the pulse rate then there is comparatively little data however if you want to send the whole waveform then you will have to send lots of samples per second. Xbee is not well suited for lots of continuous data. Have a look here for other techniques:-
Arduino Playground - InterfacingWithHardware
but how can i send lots of samples per second sir?
By using a simple protocol and simple transmitter / receiver, not the handshaking, packetised mesh network of an xbee or zigbee.
Have you seen this book:-
It contains a discussion of various types of RF connections.
Do you know what data rate you want to achieve? Without that vital piece of information it is hard so say any more.
The title of your post suggest you are working in an ECG machine, but your post only talk about a sensor. Do you know anything about a sensor capable to register ECG signals? If so, please, let me know, because I'm pretty interested on that idea.
Tnx
See Elektor Magazine -- January 2011 Issue Wireless ECG
Do use batteries... 
We don't want to hear about fried "patients"...