Holter 48 hr showed 31 xtra beats from atria. If they cause premature ventricular contractions is it dangerous? Read that prexcitaion can cause death??

Atrial arrhythmias. Most probably you don't have preexcitation. You probably have atrial ectopics (extra beats) common with stress, caffeine, hormonal changes, lack of sleep. Rare for pre-excitation to cause death.