Thank you Eric for your comment.
The original outcome of a possible stenosis was the result of a routine checkup in a medical sports laboratory. As I am almost 71 years old, I thought, it would be good to check my overall condition, as I am running quite a lot (1200 km/year)
Finally the result was that I do not need a stent. I am very happy about this and can continue running without being worried to get a heart attack.