Re: Carrie Fisher had a heart attack...
As a physician, I'm trying not to read between the lines based on the limited info that we have.
My best wishes for her; been watching her film roles since Summer 1977. They are saying "cardiac arrest" but that can be a general term. Sudden loss of consciousness and passing out can come from multiple issues, such as:
1) Acute myocardial infarction, "heart attack"
2) Stroke
3) Pulmonary embolism (blood clot in the lungs)
4) Leaking or ruptured aneurysm
5) Acute toxicity (drug overdose), although this is not normally a "sudden" thing where you are just fine one moment and unconscious the next.
...having said that, and not to sound morbid, but this could completely change the course of Episodes 8 and 9. And you know that Lucasfilm is shocked at the moment, for myriad reasons. People being told to go look at entertainment contracts and insurance policies about right now...
God bless Carrie. Speedy recovery!