When you smoke cigarettes you cause your arteries to harden which can lead to blood clots, heart disease, heart attacks, strokes etc.
If you stop smoking cigarettes your arteries began to heal and recover and after awhile the arteries should no longer be harden but sometimes they may still be harden and you will need to see your doctor about it.
Quitting smoking is a good thing for your health and it's never too late to stop smoking but you shouldn't smoke in the first place which is even better.
When you don't smoke you're at less of a risk for heart disease, blood clots, heart attacks, strokes etc and you prolong your lifespan and prevent yourself from getting COPD.