I've heard of 2 instances where death was very sudden. First: My mother was dancing with her boss at an office Christmas party. She said he turned away from her and instantly fell face-first to the floor, dead.
The second was my ex step-dad: He was at his sister's after getting out of the hospital for heart-related issues. He told his sister he loved her to which she replied, "Don't you die on me!" She could apparently tell from his tone and/or actions he was having a heart attack. She said he made a struggling noise and was gone.
I had a heart attack myself less than 3 months ago. I'm only 42, but it was a 100% blockage. I laid in bed for 3 hours in agony before seeking treatment. I kept waiting for the pain to go away, and when I realized it wasn't going to, I waited for a break in the pain where I could at least function. I was alert enough to drive myself to the hospital (not smart) and never lost consciousness. Long story short, I had a stent put in and have been OK since. They said the damage to my heart was minimal.
I don't understand how their instances and mine could be so drastically different. ZERO blood flowing through a main artery on my heart for 3 hours and the only symptom was excruciating pain. Deep, hardcore agony.
Just my two pennies.