Question regarding recent Angiogram

Recently I became SOB after minimal exertion, and because of a hx of blockages and stents, went to the Cardiologist, had a stress test and was whisked to the hospital.  I had an angiography and left ventriculography and stents installed.  It was noted that two previous (unmedicated) stents were blocked and opened to 50%.

There are two references that confuse me.  The Operative Report mentions the following:  "Left anterior descending has a diagonal that has a 60% ostial lesion... and Posterolateral branch has 60% ostial lesion".  I can't find a definition of what a Ostial lesion is. Can anyone out there educate me?

It is also interesting to me that the unmedicated stents are filling up but the medicated stents I have are fine.  Given the news of late about medicated stents, I would have suspected the opposite.  

Getting on my soapbox and repeating what I've posted earlier, regular exercise allows us to understand our limits as well as helps build stronger bodies.  It is because I exercise very regularly I was able to know I had a change in my ability to get my breath.  I also had some chest pain, but we know how elusive that symptom is as a diagnotic tool unless one has a flat-out Hollywood style heart attack.  Also, we get tired from overwork, depression, any number of reasons, but SOB symptoms really narrows things down.

Again, Ostial lesions... what are they?  Thanks

[ireneo]

Ostium is the mouth or opening of a tubular passage (a blood vessel perhaps?)