Heard a doctor say there are nerve connections between the throat and the heart (maybe common bundles/branches?), and that the endoscopy could have irritated the nerves and caused the cardiac arrest. Don’t know the accuracy of this.
I'm guessing there's truth to this....when my mother was dying of congestive heart failure/pneumonia (complications from a broken hip at age 87), my sister stayed in the hospital room 24/7 for the last 10 days....the nurses allowed her to use a small suction device in Mom's mouth if she "gurgled" (She was in a deep sleep for the last 48 hours).
Wifey and I were there when sis went to do this once and immediately Mom started gagging and coughing - we called the nurses station and they ran in - at this point her oxygen saturation dropped to zero, she turned white and her heart stopped and she was gone.
Sister was mortified and wailing that she'd been at fault - the nurses assured her, but I'd not be surprised if she still feels responsible.
Very interesting and as I singer I also find that fascinating if true. Either way may Joan rest in peace. Very sad. She is already missed by me.
The first reports said that she suffered respiratory failure which led to cardiac arrest. That sounds like overdose of anesthesia.