Can a 30 year old have cardiac arrest & a heart attack i just won't too now?

Unusual but yes: This would be pretty unusual, but can occur. Some people have congenital abnormalities that can cause this. Additionally, use of stimulants such as Cocaine and methamphetamine scan cause this. Occasionally, we see patients who have very accelerated coronary disease- there is often a family history of early heart attacks.

Yes: Younger patients can have heart attacks and cardiac arrest. The reason may be coronary disease (same as older patient) but also may include congenital coronary abnormality, hypertrophic cardiomyopathy, viral cardiomyopathy, right ventricular dysplasia. The frequency of heart attack and cardiac arrest in a 30-year-old is much less than it would be in an older patient.