It can be blocked at any time.

随时都有可能堵上。

youdao

But if the escape routes really can be blocked then cancer, eventually, will have no hiding place and a diagnosis need not be the death-sentence it often is today.

但是，如果逃跑之路的确可以被堵死，那么最终癌症将无藏身之地，并且这一诊断无需再是今天通常认为的死刑判决。

youdao

It can be a sign of a blocked artery causing a heart attack.

它可能是能够引起心脏病的动脉阻塞的症状。

youdao

But in people who are older than this - as most of the nurses in the study were - it can be the first sign of coronary heart disease, where the heart's arteries become blocked by fatty deposits.

BBC: Light smoking 'doubles sudden heart death risk in women'