Resting coronary flow varies with normal cardiac catheter laboratory stimuli.

•In recent years, there has been growing role for indices measured at rest, such as iFR.•These indices may theoretically be more susceptible to resting variation in microvascular tone.•We show resting coronary flow varies significantly with normal catheter laboratory stimuli•Resting flow variability is accompanied by significant change in microvascular resistance•Associated changes in resting indices were statistically and clinically insignificant.