True or false the scariest thing to hear in a hospital is a flat line beep?

It was when my wife was in the ER with a serious infection and I saw the crash team assembling by her. The doc said, "Don't be alarmed. Her heart is doing strange things, so we are going to give her a medication that should stabilize it. There is a chance that her heart might stop, but don't be alarmed." Don't be alarmed? Was he nuts? The meds worked, but it scared me nearly to death.