Many reasons but generally its due to risk factors for cardiac arrest.
I had a cardiac arrest apr1 2011. Several factors played into mine.
It was a perfect storm. High BP from AAS. Serotonin storm from a medication caused a further hypertensive crisis which lead to arrhythmia.
I was asleep. Luckily someone heard me gasping and called 911. If I hadnt lived across the st from the hospital Id be dead for sure.
Only a very small % survive a cardiac arrest.
That number jumps considerably if a defibrillator is on hand. = pacemaker. THe pacemaker will kick like the paddles you see in movies restarting the heart.
It also can pace meaning assist the heart in pumping to fix abnormalities in rhythm.