Could Frequent Premature Atrial Contractions Be Fatal?

hI. i WAS IN THE EMERGENCY ROOM LAST NIGHT AND DIAGNOSED WITH PAC S. i HAVE BEEN DIGNOSED WITH THEM IN THE PAST AND MY DR HAS ME ON METOPROLOL TITRATE 2X S A DAY. THESE EPISODES HAVE BEEN INTERMITTENT THROUGHOUT THE DAY EVERYDAY FOR THE PAST 6 DAYS. I M SCARED A WORRIED THAT THIS COULD BE FATAL. WHEN IS IT TIME TO WORRY?