ECG sensor, how to conect to nano board!!!!!

Hi everyone! I work on university project ecg, but i have some problems how to conect gain scheme to arduino nano. I found gain scheme on this web site:
http://biosignals.berndporr.me.uk/doku.php
May be someone can help? I try diffrent types of connections maybe I lose something?
Please HELP!
I pluged ecg sensor output(on scheme it is X4) to A0 input.
Scheme and code I attached below.

Code:
#define FASTADC 1
// defines for setting and clearing register bits
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif

void setup()
{
Serial.begin(19200);
//TIMSK0 = 0; // turn off timer0 for lower jitter
//ADCSRA = 0xe5; // set the adc to free running mode
//DIDR0 = 0x01; // turn off the digital input for adc0
//ADMUX = 0x40; // use adc0
//pinMode(A0, INPUT);

#if FASTADC
// set prescale to 16
sbi(ADCSRA,ADPS2);
cbi(ADCSRA,ADPS1);
cbi(ADCSRA,ADPS0);
#endif
}

void loop()
{
int k = analogRead(0);
Serial.print(k, DEC);
Serial.print(’\r’);
//delay(2);
}