I'm 18 severe anxiety for many years - rapid heart beat, palpitations etc. no family history, healthy weight. what my chances of heart attack/ disease?

Chronic disease: You don't have to worry about a heart attack, heart disease in the near future given your age. But you do need to treat your anxiety- to alleviate the symptoms of anxiety itself, and a lot of physical problems as your body is constantly exposed to stress hormones. See a psychiatrist.

Very very low.: At 18, in the absence of other diagnosed heart conditions or significant family history... your chances are currently very, very low. Though anxiety is a crippling condition and can cause feelings of physical problems, you are at a very low risk of any heart issues. Don't let that compound your anxiety, but I would endorse you to get seen by a mental health professional for the anxiety.