Had ekgs, holter monitors, event monitor for a month, heart ultra sound, ct angiogram. all normal! is it safe 2 say my tachycardia is benign?

Probably: But there are other factors you haven't addressed. When you have tachycardia, what are your symptoms? Do you pass out? Is there any family history of sudden or unexpected death? Do you have a normal qt interval on your ekg? Is there any evidence of WPW or brugada syndrome? Tachycardia is common. Most is benign. Check on the above questions.