The 741 opamp was designed 47 years ago to use only a +15V and -15V power supply.
Your 78xx voltage regulator has no part number showing its output voltage, it is wired wrong and it is missing important i9nput and output capacitors shown on its datasheet.
In Google Images look at the thousands of ECG circuits that feed a DC reference voltage and a signal to the patient's right leg that cancels interference.
The input probes should be connected with shielded audio cables.