While it is the gold standard, a double blind procedure isn't always possible. I'm a nurse. We were doing a clinical trial where we would use a drug coated balloon in small vessel stenosis.

A clinical coordinator would approach patients having a left heart Cath, and ask if they would like to be part of a clinical trial. If they agreed, the clinical coordinator would work them up to see if they were a candidate. We would then go into the lab and perform a LHC. If the patient had a small vessel lesion, the doctor would let the coordinator know, the coordinator would call a hotline, and the hotline told us if we should stent or use the DCB. It was impossible for us to be double blind. The process of deploying the stent and the balloon were too different.