Clinical implications of guiding catheter extubation during fractional flow reserve measurements.

Background: Fractional flow reserve (FFR) is defined by the maximal coronary flow ratio with and without stenosis.

Aims: We hypothesized that guiding catheter intubation in coronary ostia during FFR measurements may underestimate FFR value by limiting the increase of coronary flow during maximal hyperaemia.

Methods: Between June 2013 and January 2014, we prospectively included all patients with i.