Sometimes when a patient is dying in the TV show ER doctors attempting to revive him say word that sounds like Asysteline Does anyone know what this or how its spelled?

The word you are referring to is "asystole". Asystole is a medical term that refers to the complete absence of electrical activity in the heart. It is the most severe form of arrhythmia and is generally considered to be irreversible. When asystole occurs, the heart stops beating and blood circulation ceases. This can lead to permanent brain damage, organ failure, and death if not treated quickly. In the TV show ER, doctors may call out "asystole" to indicate that the patient's heart has stopped beating and they need to begin CPR or other resuscitative measures.