While he has experienced some health scares, he has never had a heart attack on camera.
Here's what we know:
* 2017: Sig experienced chest pains and shortness of breath while on the show, but it was later determined to be a blood clot in his lung (pulmonary embolism), a serious but treatable condition.
* 2020: Sig suffered from a herniated disc which caused severe pain and limited his ability to work on the boat.
It's understandable to be concerned about Sig's health, as he works in a very dangerous and demanding profession. However, he has not had a heart attack on the show.