Here is one example: >"In all patients, a research invasive physiological assessment of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) w

Here is one example: >"In all patients, a research invasive physiological assessment of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) was done. After the administration of intracoronary nitrate, a pressure wire was placed in the distal vessel at least three vessel diameters beyond the most distal stentable stenosis. [...] In the placebo group, patients were kept sedated for at least 15 min on the catheter laboratory table and the coronary catheters were withdrawn with no intervention having been done. [...] After the follow-up assessments, study participation was complete, and patients and physicians were then unblinded to the treatment group allocation. Patients who had the placebo procedure had the opportunity to choose to undergo PCI after consultation with their physician." http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(17)32714-9/abstract http://www.thelancet.com/journals/lancet/article/PIIS0140-67... So it looks like they did an exploratory surgery on the sham patients, then just left them laying sedated on the table.