Might it be that a a 17 year old have a heart attack or stroke?

Heart attack : Yes takayasu arteritis can cause it. It is rare disease.

Unusual: Possible congenital coronary anomalies are known and can cause ischemia. Aortic dissections can occur and involve coronaries. Even atherosclerosis can occur in some high risk hyperlipemia patients.

Rare: Rare but possible. Congenital disease such as abnormal origin of coronary artery and hypertrophic ("thickened") heart disease can result in "heart attack". Inherited diseases that cause abnormal tissue can predispose to aneurysms and even dissections. Inflammatory diseases can also cause similar cardiovascular events. There are quite few possible origins for teenage heart and vascular disease.