Single lead ECG ( RA- LL )

Hello 

 I want to design an single lead ECG ( 2 electrodes) no RLD ; 

I think ADS1291 is good solution ; but my problem is how to set the common mode and I can not use RLD ; my sampling rate will be 8khz because I want to detect pacemaker signal too . 

How would lead detect work here and there is no RLD electrode? 

Do you suggest other better solution rather than ads1291 ? 

Could you provide a shematic to  how I set it in single lead ? 

Thank you inadvanced