I reckon THIS would be proof-positive that "the show MUST go on!" This ole boy was determined to sell the product.

A QVC host named Cassie Slane PASSED OUT on live TV Sunday . . . but apparently she's okay.

First she started slurring her words and grabbing her chest, so it almost looked like she was having a heart attack. Then when she started falling, they cut away.

She posted a message on her Facebook page a few hours later that said she was feeling much better . . . so it's okay to laugh. The funniest part was how her co-host didn't skip a BEAT when it happened.

We assume he caught her, because it cuts away and you can't hear a thud . . . but then he continued talking about the PRODUCT, which was a knock-off version of the iPad, but for kids.

Cassie eventually got up and tried to keep going. But she kept slurring, so they cut away again.