Um, don't take me for an expert, but I think that a few principles apply.
First, there is always a ground lead on the patient, usually an ankle strap.
This gives a ground reference on the patient and should help reject a lions
share of 60Hz.  The second is this.. Tread carefully when connecting up to
humans.  These machines are built with exceedingly complicated safety features
such that it is nearly impossible to have the circuit burn up and apply large
DC voltages and currents to the victim.  When you are scurely attached to the
person, and shocking him//her, it doesn't take much to kill.

Chris Eddy
Pioneer Microsystems, Inc.

Howard McGinnis wrote:

> In a paper found on the web from MIT Health Sciences and Technology, it was
> stated that the electrocardiogram signal is approx 1 mv in amplitude. If
> the signal is amplified, how can the 60 Hz be filtered by the PIC without
> affecting the ECG signal?
>
> Howard
> Howard McGinnis
> hmcginni@digital.net
> Electronic Visions, Inc.
> 1650 Barrett Drive
> Rockledge FL 32955
> (407) 632-7530
> http://ddi.digital.net/~hmcginni
> mcginnis@e-visions.com