You have to consider the risks of these procedures. The sedation for the procedure could cause them to aspirate or become delirious (esp in the demented 90 year old). After putting a stent in a demented pt, can you guarantee she will take DAPT, because if not, she rethrombose the stent and has another MI. What if the contrast pushes their kidneys over the edge, would you offer them dialysis? Would a demented pt lay flat for 4-6 hours after the procedure, because if not, she reopens the arterial access site, and now she has an arterial bleed that you have to hold pressure on, and restart the flat time, which may develop into a pseudoaneurysm or fistula. Are they even active at baseline, because if they are very frail and bed-bound, what are you trying to achieve with the LHC? 90 yr old demented pt tend to fall and end stage cancer pts tend to be pancytopenic, what if they fall while on DAPT.
Don't focus on how a procedure might help a pt, really think about how it may hurt them.