ADS1292RECG-FE: the sampling graph of ECG is wrong

Part Number:ADS1292RECG-FE

Hello

I am sampling ECG with ADS1292R,but the sampling graph seems to be wrong .

this  is my schematic above.

this is my sampling graph above.

I make a test using RA and LA,not using RL.(the part of RL circuit is used  or this is not used ( the pins of RLDINV and RLDIN/RLDREF are connected to AVDD)).

From the sampling graph,I cannot firgure out the ECG.

I have not used the filtering arithmetic yet .

Please help me analyze what is the problem.

Thank you !