As reported on Variety, Nielsen estimates that the 90-minute debut became the Number 1-rated cable series launch on record with 10.1 million viewers. That's 6.3 million adults 18-49, passing the previous demo record of AMC's other show Better Call Saul. AMC now has three of the top five cable launches of all time (with Walking Dead ranking fifth).

In both total viewers and those 18-49, Sunday's premiere out-rated all 22 episodes from the first two seasons of The Walking Dead. 

Fear will air six episodes in its first season (leading into the season six premiere of The Walking Dead on October 11). It was given a straight-to-series, two season order by AMC earlier this year. Season two is slated for 2016.

The role was originally played by KaDee Strickland. Heigl's costars include Laverne Cox, Dule Hill, Dreama Walker and Elliott Gould.

Heigl was most recently seen in the failed drama State of Affairs. 

"For more than a decade, I was fortunate enough to play a role in the success of E! News and will miss my family at the show,” Rancic said in a statement. “At the same time, I am excited to not only continue as host of two major franchises on E! but also executive produce the aspirational new show Rich in Faith for Oxygen as well as take my wine and clothing lines to the next level. This is such a thrilling time for me and I thank the gang at E! for understanding my desire to embark on this next chapter in my life," she added.

This all comes after Rancic made controversial comments about Zendaya's dreadlocks during a post-Oscar Fashion Police. Then-co-host Kelly Osbourne as well as Kathy Griffin both quit the show following the comments. 

Melissa Rivers will be joining Fashion Police when it returns in September.