Clinical implications of guiding extubation during FFR measurements

Aims: FFR correponds to the coronary pressure ratio at maximum hyperaemia. We hypothesise that guiding intubation in coronary ostia during FFR measurements may underestimate FFR value by limiting the increased coronary flow during maximum hyperaemia. Methods and results: In this prospective monocentric study, we included all consecutive patients between June 2013 and January 2014 with FFR measurement indication. In all patients we measured FFR with a pressure wire (St. Jude Medical, St. Paul, MN, USA) under maximal hyperaemia with intravenous adenosine administration. FFR were successively measured with the guiding intubated in the coronary ostia (FFRint) and with the guiding extubated in the aorta (FFRext). Coronary ostia diameter was systematically assessed with QCA to calculate the ratio between coronary ostia and guiding surfaces as free ostial lumen ratio. During the study period we analysed 111 patients and 121 lesions. Mean FFRext was significantly lower compared to FFRint, 0.816±0.08 and 0.838±0.08, respectively (p=0.03). Revascularisation indication changed in 14 patients (13%) with a wide range of FFRint (0.87 to 0.81) and FFRext (0.80 to 0.76). There was a significant correlation between the difference of FFR value observed (FFRint-FFRext) and the free ostial lumen ratio (R2=0.08, p=0.018). Conclusions: FFR value is significantly lower when the guiding is extubated during FFR measurement. The smaller the coronary ostium, the larger the difference between FFR intubated and extubated. This systematic extubation during FFR measurements changed the revascularisation indication in 13% of the cases. FFR should be measured with the guiding extubated, especially when coronary ostia are diseased or small.